0000950170-24-022036 | 10-K | XBRL Viewer

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Intangible Assets, Net - Summary of Estimated Future Amortization for Intangible Assets (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2024	$ 2,717
2025	2,660
2026	2,528
2027	2,458
2028	2,377
Thereafter	16,880
Total	$ 29,620

Leases - Additional Information (Detail) $ in Thousands			12 Months Ended
Leases - Additional Information (Detail) $ in Thousands	May 31, 2022 USD ($)	Apr. 22, 2022 USD ($) ft²	Dec. 31, 2023 USD ($)	Sep. 01, 2023 ft²	Dec. 31, 2022 USD ($)	Oct. 01, 2022 ft²	Jun. 01, 2022 ft²	Dec. 22, 2018 ft²
Lessee Lease Description [Line Items]
Operating lease liabilities			$ 158,810
Right of use assets			129,952		$ 64,954
Minimum [Member]
Lessee Lease Description [Line Items]
Right of use assets			94,700
Bedford Massachusetts [Member]
Lessee Lease Description [Line Items]
Area of lease \| ft²		288,000
Letter of credit reduce	$ 5,600
Leases, term of contract extend		10 years
Collateralized letter of credit cash deposit	$ 8,400
Undiscounted rent payment		$ 307,400
Tenant improvement allowance		$ 72,000	13,100
Reduction to right of use assets and lease liabilities			72,000
Bedford Massachusetts [Member] \| Maximum [Member]
Lessee Lease Description [Line Items]
Right of use assets			$ 71,600
Columbus Ohio [Member]
Lessee Lease Description [Line Items]
Initial lease term of contract			15 years
Leases, term of contract extend								5 years
Undiscounted rent payment			$ 38,900
Operating lease liabilities			18,500
Right of use assets			$ 11,400
Columbus Ohio [Member] \| Minimum [Member]
Lessee Lease Description [Line Items]
Area of lease \| ft²								78,000
Columbus Ohio [Member] \| Maximum [Member]
Lessee Lease Description [Line Items]
Area of lease \| ft²								167,000
Columbus Ohio [Member] \| Initial Expansion Space [Member]
Lessee Lease Description [Line Items]
Area of lease \| ft²						36,000
Columbus Ohio [Member] \| Second Expansion Space [Member]
Lessee Lease Description [Line Items]
Area of lease \| ft²							18,000
Columbus Ohio [Member] \| Third Expansion Space [Member]
Lessee Lease Description [Line Items]
Area of lease \| ft²				19,000

Fair Value Measurements - Summary of Fair Value of Level 3 Financial Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value at the beginning of the period	$ 36,900
Changes in estimated fair value, net	1,200	$ (6,700)
Fair value at the end of the period	38,100	36,900
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value at the beginning of the period	36,900	43,600
Additions	0	0
Liabilities terminated	(800)	0
Changes in estimated fair value, net	2,000	(6,700)
Fair value at the end of the period	$ 38,100	$ 36,900

FAIR VALUE MEASUREMENTS

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

5. FAIR VALUE MEASUREMENTS

The tables below present information about the Company’s financial assets and liabilities that are measured and carried at fair value and indicate the level within the fair value hierarchy of the valuation techniques it utilizes to determine such fair value:


	Fair Value Measurement as of December 31, 2023
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets
Money market funds	$	63,919	$	63,919	$	—	$	—
Commercial paper		113,362		—		113,362		—
Government and government agency bonds		1,001,137		—		1,001,137		—
Corporate bonds		130,380		—		130,380		—
Strategic investments		6,527		5,527		—		1,000
Certificates of deposit		56,621		—		56,621		—
Total assets	$	1,371,946	$	69,446	$	1,301,500	$	1,000

Liabilities
Contingent consideration	$	38,100	$	—	$	—	$	38,100
Total liabilities	$	38,100	$	—	$	—	$	38,100

	Fair Value Measurement as of December 31, 2022
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets
Money market funds	$	467,553	$	467,553	$	—	$	—
Commercial paper		211,369		—		211,369		—
Government and government agency bonds		807,540		—		807,540		—
Corporate bonds		125,741		—		125,741		—
Strategic investments		31,321		321		—		31,000
Certificates of deposit		42,745		—		42,745		—
Total assets	$	1,686,269	$	467,874	$	1,187,395	$	31,000

Liabilities
Contingent consideration	$	36,900	$	—	$	—	$	36,900
Total liabilities	$	36,900	$	—	$	—	$	36,900

The Company’s assets with a fair value categorized as Level 1 within the fair value hierarchy include money market funds and a $5.5 million strategic investment in a biotechnology company that became publicly traded on the Nasdaq Global Market (the “Nasdaq”) during the year ended December 31, 2023. The Company's $5.5 million strategic investment is included in other non-current assets in the Company's consolidated balance sheets, with changes in fair value being recorded within other income (expense), net in the consolidated statements of operations and comprehensive loss.

The Company's assets with a fair value categorized as Level 2 within the fair value hierarchy consist of commercial paper, government and government agency bonds, corporate bonds and certificates of deposit. These assets have been initially valued at the transaction price and subsequently valued at the end of each reporting period utilizing third-party pricing services. The Company uses observable market inputs to determine value, which primarily consist of reportable trades. Certain of the short-term investments with maturities of less than three months at the date of acquisition are presented as cash equivalents on the consolidated balance sheets as of December 31, 2023 and 2022.

The Company’s assets with a fair value categorized as Level 3 within the fair value hierarchy consist of a strategic investment in a private biotechnology company whose fair value measurement was based upon significant inputs not observable in the market and therefore represented a Level 3 measurement.

The Company’s contingent consideration liability with a fair value categorized as Level 3 within the fair value hierarchy relates to the regulatory-related contingent payments to Myonexus selling shareholders as well as to two academic institutions under separate license agreements that meet the definition of a derivative. For more information related to Myonexus, please read Note 3, License and Collaboration Agreements. The contingent consideration liability was estimated using an income approach based on the probability-weighted expected cash flows that incorporated industry-based probability adjusted assumptions relating to the achievement of the milestone and thus the likelihood of making the payments. This fair value measurement was based upon significant inputs not observable in the market and therefore represented a Level 3 measurement. Significant changes which increase or decrease the probabilities of achieving the milestone, or shorten or lengthen the time required to achieve the milestone, would result in a corresponding increase or decrease in the fair value of the liability. At the end of each reporting period, the fair value is adjusted to reflect the most current assumptions through earnings.

The Company assesses its financial assets measured at fair value on a recurring basis and transfers its financial assets between the relevant fair value hierarchies at the end of each reporting period, as needed. During the year ended December 31, 2023, the Company's strategic investment in a formerly private biotechnology company transferred into Level 1 from Level 3 as a result of the biotechnology company's listing on the Nasdaq. There were no additional transfers into or out of Level 3 during the year ended December 31, 2023. The following table represents a roll-forward of the fair value of Level 3 financial assets for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Fair value, beginning of year	$	31,000		$	32,412
Additions		4,000			1,163
Transfers out of Level 3		(4,000	)		—
Changes in estimated fair value		(30,000	)		(2,575	)
Fair value, end of year	$	1,000		$	31,000

During the year ended December 31, 2023, the Company impaired its investment in Series A preferred stock of Lacerta after comparing the fair value of the Lacerta strategic investment to its carrying value, resulting in an impairment loss of $30.0 million. The Company's assessment considered entity-specific impairment indicators, such as the future business prospects of Lacerta's existing programs and expected future cash flows. The fair value as of December 31, 2023 was estimated based on the expectation that the Company would realize no future cash flows associated with its investment in Lacerta. The impairment loss is included in other income (expense), net within the consolidated statements of operations and comprehensive loss. During the years ended December 31, 2022 and 2021, the company recorded impairment losses of $2.6 million and $4.5 million, respectively, related to its strategic investments.

The following table represents a roll-forward of the fair value of Level 3 financial liabilities for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Fair value, beginning of year	$	36,900		$	43,600
Additions		—			—
Liabilities terminated		(800	)		—
Changes in estimated fair value, net		2,000			(6,700	)
Fair value, end of year	$	38,100		$	36,900

A net increase of $1.2 million and a net decrease of $6.7 million were recorded during the years ended December 31, 2023 and December 31, 2022, respectively, to account for the change in fair value and termination of liabilities of the Company's existing contingent consideration liabilities. These changes, which are recorded in other income (expense), net in the consolidated statement of operations and comprehensive loss, were a result of updates made to certain inputs and assumptions impacting the probability-weighted expected cash flows, principally the discount rate utilized to determine the present value of future payments to be made, the

probability of success of the underlying programs and the approval date of the underlying programs, partially offset by the termination of a license agreement with an academic institution during the year ended December 31, 2023. As of December 31, 2023 and 2022, the remaining contingent consideration was recorded as a non-current liability on the Company's consolidated balance sheets.

The carrying amounts reported in the consolidated balance sheets for cash and cash equivalents, accounts receivable, net and accounts payable approximated fair value because of the immediate or short-term maturity of these financial instruments. For fair value information related to the Company’s debt facilities, please read Note 13, Indebtedness.

License and Collaboration Agreements - Additional Information (Detail) $ in Thousands, shares in Millions		1 Months Ended							12 Months Ended
	Dec. 21, 2019 USD ($) shares	Nov. 30, 2021 USD ($)	Oct. 31, 2021 USD ($)	Jul. 31, 2021 USD ($)	Nov. 30, 2019 USD ($)	Apr. 30, 2019 USD ($)	Jul. 31, 2017	Jun. 30, 2016 USD ($)	Dec. 31, 2023 USD ($) Milestone shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Mar. 31, 2024 USD ($)	Feb. 28, 2021 USD ($)	Dec. 31, 2019 USD ($)	Aug. 08, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance costs			$ 26,500
Product revenues, net									$ 1,144,876	$ 843,769	$ 612,401
Impairment of strategic investments									30,321	2,575	4,488
Contingent consideration									38,100	36,900
Intangible asset, net									29,620	7,578
Cost of sales (excluding amortization of in-licensed rights)									150,343	139,989	97,049
Amortization of in-licensed rights									1,559	714	706
Development milestone and settlement upfront fee recognized as research and development expense									13,200	32,600	50,300
ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product revenues, net									200,356	0
US [Member] \| ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product revenues, net									200,356	0
Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalty payments							4.00%
Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalty payments							8.00%
Genethon [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense									$ 0	0	4,000
Up-front cash payment under development					$ 157,500
Up-front cash payment under sales milestone					$ 78,800
Up-front cash payment under development percentage					75.00%
Number of development milestone \| Milestone									0
Other Licensed Products [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front cash payment under development percentage					25.00%
Myonexus Therapeutics, Inc. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Final exercise price						$ 178,300
Additional development milestone payments to be paid						$ 200,000
Contingent consideration									$ 37,700	35,500
Lacerta Therapeutics [Member] \| Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Impairment of strategic investments									30,000
BioMarin Pharmaceutical, Inc. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory and sales milestone payments									0
Intangible asset, net																$ 6,600
Sales milestone payment recorded as an in-license right									0
Royalty expense									17,600	30,400	31,400
BioMarin Pharmaceutical, Inc. [Member] \| AMONDYS 45 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory milestone payable													$ 10,000
BioMarin Pharmaceutical, Inc. [Member] \| Intellectual Property
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amortization of in-licensed rights									2,300
BioMarin Pharmaceutical, Inc. [Member] \| US [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty payment expiry period		2024-03
BioMarin Pharmaceutical, Inc. [Member] \| EU [member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty payment expiry period		2024-12
BioMarin Pharmaceutical, Inc. [Member] \| Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalty payments		4.00%
BioMarin Pharmaceutical, Inc. [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory and sales milestone payments		$ 50,000
Percentage of royalty payments		5.00%
BioMarin Pharmaceutical, Inc. [Member] \| Maximum [Member] \| Other Countries [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty payment expiry period		2024-12
University of Western Australia [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory and sales milestone payments									0
Sales milestone payment recorded as an in-license right									0
Royalty expense									11,800	10,500	7,700
Carrying value of intangible assets									700
University of Western Australia [Member] \| EXONDYS 51 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sales milestone payment recorded as an in-license right																	$ 1,000
University of Western Australia [Member] \| VYONDYS 53 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sales milestone payment recorded as an in-license right														$ 500
University of Western Australia [Member] \| AMONDYS 45 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sales milestone payment recorded as an in-license right													$ 500
University of Western Australia [Member] \| Maximum [Member] \| EXONDYS 51 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payments to UWA on successful achievement of certain development and regulatory milestones								$ 26,000
Collaborative Arrangement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment for option exercise									165,800		0
Contingent research milestone payments									5,100	6,000	3,000
Collaborative Arrangement \| Research and Development Expense [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front and development milestone expenses									7,500	8,500
Collaborative Arrangement \| ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and other receivable									7,100
Collaborative Arrangement \| Forecast [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and other receivable												$ 48,000
Collaborative Arrangement \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone and settlement upfront fee recognized as research and development expense									3,200
Contingent research milestone payments									$ 34,800
Collaborative Arrangement \| Roche Holding A.G. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from license and collaborative agreement	$ 1,200,000
Issuance costs	$ 312,100
Stock issued during period shares collaboration and license agreement \| shares	2.5
Payment for option exercise	$ 485,000
Single combined performance obligation	348,700
Stock options exercised or expired \| shares									0.0
Product revenues, net									$ 98,500	89,200	89,500
Deferred revenue									487,400
Deferred revenue, current									50,400
Deferred revenue separate material options right									485,000	485,000
Research and development expense									106,900	117,800	90,500
Collaboration receivable									29,800	41,800
Collaborative Arrangement \| Roche Holding A.G. [Member] \| ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and other receivable									9,200	0
Inventory costs									1,800
Collaborative Arrangement \| Roche Holding A.G. [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory and sales milestones payment received	$ 1,700,000
Collaborative Arrangement \| Genethon [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense									6,600	$ 3,500	$ 11,700
Up-front cash payment under development					$ 28,000
Series A Preferred Stock Purchase Agreement \| Lacerta Therapeutics [Member] \| Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front payment \| shares															4.5
Series A Preferred Stock Purchase Agreement \| Lacerta Therapeutics [Member] \| Other Noncurrent Assets [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue															$ 30,000
License And Purchase Agreement \| Lacerta Therapeutics [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue															$ 38,000
Nationwide License Agreement [Member] \| ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Carrying value of intangible assets									22,200
Nationwide License Agreement [Member] \| Nationwide Children's Hospital [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sublicense payment				$ 38,000
Cost of sales (excluding amortization of in-licensed rights)									6,000
Carrying value of intangible assets									23,000
Nationwide License Agreement [Member] \| Nationwide Children's Hospital [Member] \| ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Carrying value of intangible assets									$ 10,000

Leases - Summary of Maturities of Lease Liabilities and Reconciliation of Lease Liabilities Recognized Under Topic 842 (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Maturity of lease liability
2024	$ 33,718
2025	34,477
2026	28,006
2027	27,995
2028	28,611
Thereafter	245,835
Total minimum lease payments	398,642
Less: imputed interest	(239,832)
Total operating lease liabilities	158,810
Included in the consolidated balance sheet:
Current portion of lease liabilities within other current liabilities	$ 17,845	$ 15,489
Current portion of lease liabilities within other current liabilities [Extensible List]	Current portion of lease liabilities within other current liabilities
Lease liabilities, non-current	$ 140,965	$ 57,578
Total operating lease liabilities	$ 158,810

Other (Loss) Income, Net - Summary of Other (Loss) Income, Net (Detail) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Investment Income, Nonoperating [Abstract]

Interest expense

$ (22,010)

$ (53,248)

$ (63,525)

Interest income

36,257

16,488

354

Accretion of investment discount, net

49,712

11,235

157

(Loss) gain on contingent consideration, net

^[1]

(1,200)

6,700

7,200

Impairment of strategic investments

(30,321)

(2,575)

(4,488)

Other, net

617

(6,921)

(936)

Other income (expense), net

33,055

(28,321)

(61,238)

Loss on debt extinguishment

(387,329)

(125,441)

Gain from sale of Priority Review Voucher

102,000

Total other (loss) income, net

$ (252,274)

$ (153,762)

$ 40,762

[1]	The (loss) gain on contingent consideration, net is related to the fair value adjustment of the regulatory-related contingent payments that are accounted for as derivatives. Please see Note 5. Fair Value Measurements for further details.

Fair Value Measurements - Assets and Liabilities Measured and Carried at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 1,371,946	$ 1,686,269
Contingent consideration	38,100	36,900
Total liabilities	38,100	36,900
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	63,919	467,553
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	113,362	211,369
Government and Government Agency Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,001,137	807,540
Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	130,380	125,741
Strategic Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	6,527	31,321
Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	56,621	42,745
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	69,446	467,874
Contingent consideration	0	0
Total liabilities	0	0
Level 1 [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	63,919	467,553
Level 1 [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 1 [Member] \| Government and Government Agency Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 1 [Member] \| Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 1 [Member] \| Strategic Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	5,527	321
Level 1 [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,301,500	1,187,395
Contingent consideration	0	0
Total liabilities	0	0
Level 2 [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 2 [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	113,362	211,369
Level 2 [Member] \| Government and Government Agency Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,001,137	807,540
Level 2 [Member] \| Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	130,380	125,741
Level 2 [Member] \| Strategic Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 2 [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	56,621	42,745
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,000	31,000	$ 32,412
Contingent consideration	38,100	36,900
Total liabilities	38,100	36,900	$ 43,600
Level 3 [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 3 [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 3 [Member] \| Government and Government Agency Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 3 [Member] \| Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 3 [Member] \| Strategic Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,000	31,000
Level 3 [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 0	$ 0

Stock Based Compensation - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock Units (RSUs) [Member]

12 Months Ended

Dec. 31, 2023

$ / shares

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Shares, Grants outstanding at beginning of the period | shares

1,829,632

^[1]

Shares, Granted | shares

1,165,925

^[2]

Shares, Vested | shares

(644,614)

Shares, Forfeited | shares

(110,439)

Shares, Grants outstanding at end of the period | shares

2,240,504

Weighted Average Grant Date Fair Value per Share, Grants outstanding at beginning of the period | $ / shares

$ 93.59

^[1]

Weighted Average Grant Date Fair Value per Share, Granted | $ / shares

151.2

^[2]

Weighted Average Grant Date Fair Value per Share, Vested | $ / shares

93.69

Weighted Average Grant Date Fair Value per Share, Forfeited | $ / shares

112.27

Weighted Average Grant Date Fair Value per Share, Grants outstanding at end of the period | $ / shares

$ 120.17

[1]	(1) Included in RSUs outstanding at the beginning of the year ended December 31, 2023 are 38,500 shares of PSUs (the “March 2022 PSUs”) with performance conditions related to regulatory approval of the Company’s product candidates.
[2]	(2) Included in RSUs granted during the year ended December 31, 2023 are 502,225 shares with performance conditions (the “March 2023 PSUs”), which are related to regulatory approval of certain of the Company's product candidates and achievement of a certain financial performance target.

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Non-deductible premium paid on the conversion of the 2024 Notes	$ 379,900
Current state tax expense	11,111	$ 13,193	$ (40)
Federal, State and Local, Tax Expense	4,200	11,100
Net change in valuation allowance for deferred tax assets	71,800	139,600
Net operating loss carried forwards	154,948	241,826
Federal Orphan Drug Tax Credits	239,400
Accrual for interest or penalties	0	0
Recognized interest and/or penalties	$ 0	$ 0	$ 0
Minimum [Member]
Income Taxes [Line Items]
Operating loss carryforwards, ending of expiration year	2024
Maximum [Member]
Income Taxes [Line Items]
Operating loss carryforwards, ending of expiration year	2041
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 550,300
Net operating loss carryforwards subject to expiration	262,200
Net operating loss carried forwards	288,100
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	473,100
Net operating loss carryforwards subject to expiration	445,000
Net operating loss carried forwards	28,100
Foreign [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 16,700
Research and Development Credits [Member]
Income Taxes [Line Items]
Research and development credits carryforward, Description	These federal and state research and development credits expire between 2024 and 2043 and between 2024 and 2038, respectively.
Research and Development Credits [Member] \| Federal [Member]
Income Taxes [Line Items]
Research and development	$ 102,600
Research and Development Credits [Member] \| State [Member]
Income Taxes [Line Items]
Research and development	$ 40,500

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 42.5	$ 40.0	$ 36.6

INCOME TAXES

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

INCOME TAXES

18. INCOME TAXES

The following table summarizes the loss before the provision (benefit) for income taxes by jurisdiction for the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands)
Domestic	$	(238,660	)	$	(251,384	)	$	(47,633	)
Foreign		(281,438	)		(438,579	)		(371,315	)
Total	$	(520,098	)	$	(689,963	)	$	(418,948	)

The following table summarizes provision (benefit) for income taxes in the accompanying consolidated financial statements for the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands)
Current provision:
Federal	$	4,180		$	—		$	—
State		11,111			13,193			(40	)
Foreign		753			944			181
Total current provision		16,044			14,137			141
Deferred benefit:
Federal		—			—			—
State		—			—			—
Foreign		(165	)		(612	)		(309	)
Total deferred benefit		(165	)		(612	)		(309	)
Total income tax expense (benefit)	$	15,879		$	13,525		$	(168	)

The following table summarizes the reconciliation between the Company’s effective tax rate and the statutory income tax rate for each of the periods indicated:


	For the Year Ended December 31,
	2023				2022				2021
Federal income tax rate		21.0		%		21.0		%		21.0		%
State taxes		(7.7	)			4.1				0.4
Research and development tax credits		28.3				6.9				10.0
Valuation allowance		(13.7	)			(14.7	)			(9.8	)
Permanent differences		(0.2	)			(1.1	)			(0.3	)
Stock-based compensation		(2.0	)			(1.5	)			(3.4	)
Excess benefit stock deductions		1.6				0.3				0.4
Foreign rate differential		(11.3	)			(13.2	)			(18.4	)
Non-deductible repurchase premium		—				(2.2	)			—
Non-deductible premium on note conversion		(15.3	)			—				—
Other		(3.8	)			(1.6	)			0.1
Effective tax rate		(3.1	)	%		(2.0	)	%		(0.0	)	%

The significant items impacting the Company’s effective tax rate for each of the periods primarily includes state taxes, research and development tax credits, valuation allowance and foreign rate differential. For the year ended December 31, 2023, the

Company's effective tax rate was also significantly impacted by the $379.9 million non-deductible premium paid on the conversion of the 2024 Notes.

The following table summarizes the deferred tax assets and liabilities for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	154,948		$	241,826
Difference in depreciation and amortization		36,611			39,725
Research and development tax credits		374,017			261,067
Stock-based compensation		94,452			80,193
Lease liabilities		33,792			11,782
Capitalized inventory		35,269			33,366
Debt discount		25,597			35,975
Capitalized research and development costs		106,534			74,886
Other		50,308			44,022
Total deferred tax assets		911,528			822,842
Deferred tax liabilities:
Right of use asset		(25,800	)		(9,174	)
Debt discount		—			—
Total deferred tax liabilities		(25,800	)		(9,174	)
Valuation allowance		(883,665	)		(811,908	)
Net deferred tax assets	$	2,063		$	1,760

For tax years beginning on or after January 1, 2022, the Tax Cuts and Jobs Act of 2017 eliminates the option to currently deduct research and development expenses and requires taxpayers to capitalize and amortize the costs over five years for research activities performed in the United States and 15 years for research activities performed outside the United States. The requirement to capitalize research and development costs for tax purposes resulted in the Company having taxable profits and recording federal and state tax expense of $4.2 million and $11.1 million, respectively. The state tax expense of $11.1 million is primarily related to the temporary suspension of utilizing net operating loss carryforwards in certain states the Company operates in.

The Company has evaluated the positive and negative evidence bearing upon the realizability of its U.S. net deferred tax assets, which are comprised principally of federal and state net operating loss carryforwards, research and development tax credit carryforwards, capitalized research and development costs, stock-based compensation expense, capitalized inventory, and intangibles. Under the applicable accounting standards, management has considered the Company’s history of losses and concluded that it is more likely than not that the Company will not recognize the benefits of its net federal and state deferred tax assets. Accordingly, a full valuation allowance against the U.S. net deferred tax asset is maintained at December 31, 2023 and 2022. The net change in the valuation allowance for deferred tax assets was an increase of $71.8 million and $139.6 million for the years ended December 31, 2023 and 2022, respectively. This increase for the year ended December 31, 2023 was primarily due to the capitalization of section 174 costs and federal and state tax credits recorded in the current year.

The Company generated foreign deferred tax assets mainly consisting of net operating loss carryforwards, stock-based compensation and unrealized gain/losses. Based upon the income projections in the majority of the foreign jurisdictions, the Company believes it will realize the benefit of its future deductible differences in these jurisdictions. As such, the Company has not recorded a valuation allowance against the net deferred tax assets in these foreign jurisdictions. Brazil and the Netherlands have generated deferred tax assets, which consist primarily of net operating loss carryforwards. The Company has concluded that it is more likely than not that it will not recognize the future benefits of the deferred tax assets in these jurisdictions, and accordingly, a full valuation allowance has been recorded against these foreign deferred tax assets.

As of December 31, 2023, the Company had federal and state net operating loss carryforwards of $550.3 million and $473.1 million, respectively, available to reduce future taxable income. Federal and state net operating loss carry forwards of $262.2 million and $445.0 million will expire at various dates between 2024 and 2041. Federal and state net operating loss carryforwards of $288.1 million and $28.1 million, respectively, can be carried forward indefinitely. Utilization of these net operating losses could be limited under Section 382 of the Internal Revenue Code and similar state laws based on historical or future ownership changes and the value of the Company’s stock. Additionally, the Company has $102.6 million and $40.5 million of federal and state research and

development credits, respectively, and $239.4 million of federal orphan drug tax credits available to offset future tax liabilities. These federal and state research and development credits expire between 2024 and 2043 and between 2024 and 2038, respectively. The federal orphan drug credits expire between 2033 and 2043. The Company also has foreign net operating loss carryforwards of $16.7 million, mainly derived from the net operating loss generated by its subsidiary in Brazil, which may be carried forward indefinitely.

The Company, or one of its subsidiaries, files income tax returns in the U.S., and various state and foreign jurisdictions. The federal, state and foreign income tax returns are generally subject to tax examinations for the tax years ended December 31, 2020 through December 31, 2023. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service, state or foreign tax authorities to the extent utilized in a future period.

The following table summarizes the reconciliation of the beginning and ending amount of total unrecognized tax benefits for each of the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands)
Balance at beginning of the period	$	61,704		$	53,815		$	48,475
Increase related to current year tax positions		4,126			8,079			5,503
Increase related to prior year tax positions		—			—			—
Decrease related to prior year tax positions		(800	)		(190	)		(163	)
Balance at end of the period	$	65,030		$	61,704		$	53,815

The balance of total unrecognized tax benefits at December 31, 2023, if recognized, would not affect the effective tax rate on income from continuing operations, due to a full valuation allowance against the Company’s U.S. deferred tax assets. The Company does not expect the amount of unrecognized tax benefits to change significantly in the next twelve months. The Company’s policy is to recognize interest and/or penalties related to income tax matters in income tax expense. It had no accrual for interest or penalties on its consolidated balance sheets at December 31, 2023 or 2022. No interest and/or penalties were recognized in 2023, 2022, or 2021.

The Company’s intent is to only make distributions from non-U.S. subsidiaries in the future when they can be made at no net tax cost. Otherwise, the Company considers all of its foreign earnings to be permanently reinvested outside of the U.S. and has no plans to repatriate these foreign earnings to the U.S. The Company has no material unremitted earnings from its non-U.S. subsidiaries.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Product Revenues, Net, Accounts Receivable, Net and Reserves for Product Revenues - Summary of Change in Reserves for Discounts and Allowances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	$ 94,698	$ 70,466
Provision	258,646	181,518
Adjustments relating to prior year	(4,567)	(5,649)
Payments/credits	(184,005)	(151,637)
Ending Balance	164,772	94,698
Chargebacks [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	417	799
Provision	44,191	12,446
Adjustments relating to prior year	536	0
Payments/credits	(17,658)	(12,828)
Ending Balance	27,486	417
Rebates [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	67,493	60,506
Provision	129,724	108,514
Adjustments relating to prior year	(5,103)	(5,679)
Payments/credits	(93,920)	(95,848)
Ending Balance	98,194	67,493
Prompt Pay [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	3,343	2,798
Provision	15,067	12,904
Adjustments relating to prior year	0	0
Payments/credits	(14,579)	(12,359)
Ending Balance	3,831	3,343
Other Accruals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	23,445	6,363
Provision	69,664	47,654
Adjustments relating to prior year	0	30
Payments/credits	(57,848)	(30,602)
Ending Balance	$ 35,261	$ 23,445

Property and Equipment, Net - Summarizes Components of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 418,124	$ 328,913
Less: accumulated depreciation	(190,970)	(148,876)
Property and equipment, net	227,154	180,037
Lab and Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	108,101	91,806
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	99,989	97,328
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	91,089	23,587
Software and Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	50,179	47,573
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	48,063	47,942
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	9,339	9,313
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,183	5,183
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,988	4,988
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,193	$ 1,193

Income Taxes - Reconciliation Between Effective Tax Rate and Statutory Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Federal income tax rate	21.00%	21.00%	21.00%
State taxes	(7.70%)	4.10%	0.40%
Research and development tax credits	28.30%	6.90%	10.00%
Valuation allowance	(13.70%)	(14.70%)	(9.80%)
Permanent differences	(0.20%)	(1.10%)	(0.30%)
Stock-based compensation	(2.00%)	(1.50%)	(3.40%)
Excess benefit stock deductions	1.60%	0.30%	0.40%
Foreign rate differential	(11.30%)	(13.20%)	(18.40%)
Non-deductible repurchase premium	0.00%	(2.20%)	0.00%
Non-deductible premium on note conversion	(15.30%)	(0.00%)	(0.00%)
Other	(3.80%)	(1.60%)	0.10%
Effective tax rate	(3.10%)	(2.00%)	(0.00%)

Cash, Cash Equivalents and Marketable Securities - Summary of Company Financial Assets with Maturities of Less Than 90 Days Included in Cash Equivalents (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Cash and Cash Equivalents [Line Items]
Cash equivalents	$ 117,599	$ 632,351
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash equivalents	63,919	467,553
Commercial Paper [Member]
Cash and Cash Equivalents [Line Items]
Cash equivalents	53,680	33,190
Government and Government Agency Bonds [Member]
Cash and Cash Equivalents [Line Items]
Cash equivalents	0	128,451
Corporate Bond [Member]
Cash and Cash Equivalents [Line Items]
Cash equivalents	$ 0	$ 3,157

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 428,430	$ 966,777
Short-term investments	1,247,820	1,022,597
Accounts receivable , net	400,327	214,628
Inventory	322,859	203,968
Other current assets	179,895	149,891
Total current assets	2,579,331	2,557,861
Property and equipment, net	227,154	180,037
Right of use assets	129,952	64,954
Non-current inventory	191,368	162,545
Other non-current assets	136,771	162,969
Total assets	3,264,576	3,128,366
Current liabilities:
Accounts payable	164,918	95,875
Accrued expenses	314,997	418,996
Deferred revenue, current portion	50,416	89,244
Current portion of long-term debt	105,483	0
Current portion of lease liabilities	17,845	15,489
Total current liabilities	653,659	619,604
Long-term debt	1,132,515	1,544,292
Lease liabilities, net of current portion	140,965	57,578
Deferred revenue, net of current portion	437,000	485,000
Contingent consideration	38,100	36,900
Other non-current liabilities	3,000	42
Total liabilities	2,405,239	2,743,416
Commitments and contingencies (Note 21)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 3,333,333 shares authorized; none issued and outstanding	0	0
Common stock, $0.0001 par value, 198,000,000 shares authorized; 93,731,831 and 87,950,117 issued and outstanding at December 31, 2023 and 2022, respectively	9	9
Additional paid-in capital	5,304,623	4,296,841
Accumulated other comprehensive income (loss), net of tax	918	(1,664)
Accumulated deficit	(4,446,213)	(3,910,236)
Total stockholders’ equity	859,337	384,950
Total liabilities and stockholders’ equity	$ 3,264,576	$ 3,128,366

Summary of Components of Accounts Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Receivables, Net, Current [Abstract]
Product sales receivable, net of discounts and allowances	$ 400,300	$ 214,600
Total accounts receivable, net	$ 400,327	$ 214,628

OTHER (LOSS) INCOME, NET (Tables)

12 Months Ended

Dec. 31, 2023

Other Income and Expenses [Abstract]

Summary of Other (Loss) Income, Net

The following table summarizes other (loss) income, net for the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands)
Interest expense	$	(22,010	)	$	(53,248	)	$	(63,525	)
Interest income		36,257			16,488			354
Accretion of investment discount, net		49,712			11,235			157
(Loss) gain on contingent consideration, net*		(1,200	)		6,700			7,200
Impairment of strategic investments		(30,321	)		(2,575	)		(4,488	)
Other, net		617			(6,921	)		(936	)
Other income (expense), net	$	33,055		$	(28,321	)	$	(61,238	)
Loss on debt extinguishment		(387,329	)		(125,441	)		—
Gain from sale of Priority Review Voucher		102,000			—			102,000
Total other (loss) income, net	$	(252,274	)	$	(153,762	)	$	40,762

Stock Based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Stock Option Shares
Grants outstanding at beginning of the period \| shares	9,130,140
Granted \| shares	1,186,399
Exercised \| shares	(528,909)
Cancelled and forfeited \| shares	(204,935)
Grants outstanding at end of the period \| shares	9,582,695
Grants exercisable at end of the period \| shares	5,951,953
Grants vested and expected to vest at end of the period \| shares	9,216,033
Weighted Average Exercise Price
Grants outstanding at beginning of the period \| $ / shares	$ 70.04
Granted \| $ / shares	147.71
Exercised \| $ / shares	76.68
Cancelled and forfeited \| $ / shares	103.74
Grants outstanding at end of the period \| $ / shares	78.57
Grants exercisable at end of the period \| $ / shares	70.91
Grants vested and expected to vest at end of the period \| $ / shares	$ 77.01
Aggregate Intrinsic Value
Outstanding at end of year \| $	$ 288,119
Exercisable at end of year \| $	202,405
Vested and expected to vest \| $	$ 285,706
Weighted Average Remaining Contractual Life (Years)
Outstanding at end of year	5 years 8 months 12 days
Exercisable at end of year	4 years 10 months 24 days
Vested and expected to vest	5 years 6 months

Cash, Cash Equivalents and Marketable Securities - Summary of Company Cash, Cash Equivalents and Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash and Cash Equivalents [Line Items]
Available for sale debt securities, Gross unrealized gains	$ 1,124	$ 187
Available for sale debt securities, Gross unrealized losses	(179)	(1,824)
Cash and cash equivalents, Amortized cost	1,675,305	1,991,011
Cash and cash equivalents, Gross unrealized gains	0	9
Cash and cash equivalents, Gross unrealized losses	0	0
Cash and cash equivalents	428,430	966,777	$ 2,115,869
Cash, cash equivalents and investments, Amortized cost	428,430	966,768
Cash, cash equivalents and investments, Gross unrealized gains	1,124	187
Cash, cash equivalents and investments, Gross unrealized losses	(179)	(1,824)
Cash, cash equivalents and investments, Fair market value	1,676,250	1,989,374
Available for sale debt securities current, Amortized cost	1,246,875	1,024,243
Available for sale debt securities current, Gross unrealized gains	1,124	178
Available for sale debt securities current, Gross unrealized losses	(179)	(1,824)
Available for sale debt securities current, Fair market value	1,247,820	1,022,597
Available for sale debt securities noncurrent, Fair market value	428,430
Cash and Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Available for sale debt securities, Gross unrealized gains	0	0
Available for sale debt securities, Gross unrealized losses	0	0
Cash and cash equivalents, Amortized cost	374,750	801,979
Cash and cash equivalents	374,750	801,979
Commercial Paper [Member]
Cash and Cash Equivalents [Line Items]
Available for sale debt securities, Gross unrealized gains	0	0
Available for sale debt securities, Gross unrealized losses	0	0
Available for sale debt securities, Fair market value	113,362	211,369
Cash and cash equivalents, Amortized cost	113,362	211,369
Government and Government Agency Bonds [Member]
Cash and Cash Equivalents [Line Items]
Available for sale debt securities, Gross unrealized gains	1,006	178
Available for sale debt securities, Gross unrealized losses	(171)	(1,542)
Available for sale debt securities, Fair market value	1,001,137	807,540
Cash and cash equivalents, Amortized cost	1,000,302	808,904
Cash, cash equivalents and investments, Fair market value		1,989,374
Corporate Bond [Member]
Cash and Cash Equivalents [Line Items]
Available for sale debt securities, Gross unrealized gains	118	9
Available for sale debt securities, Gross unrealized losses	(8)	(282)
Available for sale debt securities, Fair market value	130,380	125,741
Cash and cash equivalents, Amortized cost	130,270	126,014
Certificates of Deposit [Member]
Cash and Cash Equivalents [Line Items]
Available for sale debt securities, Gross unrealized gains	0	0
Available for sale debt securities, Gross unrealized losses	0	0
Available for sale debt securities, Fair market value	56,621	42,745
Cash and cash equivalents, Amortized cost	$ 56,621	$ 42,745

INTANGIBLE ASSETS, NET (Tables)

12 Months Ended

Dec. 31, 2023

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Components of Intangible Assets

The following table summarizes the components of the Company’s intangible assets for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
In-licensed rights	$	32,673		$	8,573
Patents		4,889			5,106
Software licenses		302			302
Intangible assets, gross		37,864			13,981
Less: accumulated amortization		(8,244	)		(6,403	)
Intangible assets, net	$	29,620		$	7,578

Summary of Estimated Future Amortization for Intangible Assets

The following table summarizes the estimated future amortization for intangible assets:


	As of December 31, 2023
	(in thousands)
2024	$	2,717
2025		2,660
2026		2,528
2027		2,458
2028		2,377
Thereafter		16,880
Total	$	29,620

Gain From Sale of Priority Review Voucher - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 28, 2021	Dec. 31, 2023
Gain From Sale Of Intangible Asset [Line Items]
Proceeds From Sale Of Rare Pediatric Disease Priority Review Voucher	$ 102.0
F D A
Gain From Sale Of Intangible Asset [Line Items]
Proceeds From Sale Of Rare Pediatric Disease Priority Review Voucher		$ 102.0

ORGANIZATION AND NATURE OF BUSINESS

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

ORGANIZATION AND NATURE OF BUSINESS

1. ORGANIZATION AND NATURE OF BUSINESS

Sarepta Therapeutics, Inc. (together with its wholly-owned subsidiaries, “Sarepta” or the “Company”) is a commercial-stage biopharmaceutical company focused on helping patients through the discovery and development of unique RNA-targeted therapeutics, gene therapy and other genetic therapeutic modalities for the treatment of rare diseases. Applying its proprietary, highly-differentiated and innovative technologies, and through collaborations with its strategic partners, the Company has developed multiple approved products for the treatment of Duchenne muscular dystrophy (“Duchenne”) and is developing potential therapeutic candidates for a broad range of diseases and disorders, including Duchenne, Limb-girdle muscular dystrophies (“LGMDs”) and other neuromuscular and central nervous system (“CNS”) disorders.

The Company's products in the U.S., EXONDYS 51 (eteplirsen) Injection (“EXONDYS 51”), VYONDYS 53 (golodirsen) Injection (“VYONDYS 53”), AMONDYS 45 (casimersen) Injection (“AMONDYS 45”) and ELEVIDYS, were granted accelerated approval by the U.S. Food and Drug Administration (the “FDA”) on September 19, 2016, December 12, 2019, February 25, 2021 and June 22, 2023. Indicated for the treatment of Duchenne in patients who have a confirmed mutation of the dystrophin gene that is amenable to exon 51, exon 53 and exon 45 skipping, respectively, EXONDYS 51, VYONDYS 53 and AMONDYS 45 use the Company’s phosphorodiamidate morpholino oligomer (“PMO”) chemistry and exon-skipping technology to skip exon 51, exon 53 and exon 45 of the dystrophin gene. Exon skipping is intended to promote the production of an internally truncated but functional dystrophin protein. ELEVIDYS addresses the root genetic cause of Duchenne mutations in the dystrophin gene that result in the lack of dystrophin protein by delivering a gene that codes for a shortened form of dystrophin to muscle cells known as ELEVIDYS micro-dystrophin. ELEVIDYS is approved for the treatment of ambulatory pediatric patients aged 4 through 5 years with Duchenne with a confirmed mutation in the Duchenne gene. ELEVIDYS is contraindicated in patients with any deletion in exon 8 and/or exon 9 in the Duchenne gene.

As of December 31, 2023, the Company had approximately $1,691.8 million of cash, cash equivalents, restricted cash and investments, consisting of $1,247.8 million of short-term investments, $428.4 million of cash and cash equivalents and $15.6 million of long-term restricted cash. The Company believes that its balance of cash, cash equivalents and investments as of the date of the issuance of this report is sufficient to fund its current operational plan for at least the next twelve months, though it may pursue additional cash resources through public or private debt and equity financings, seek funded research and development arrangements and additional government contracts and establish collaborations with or license its technology to other companies.

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail) $ / shares in Units, $ in Thousands, € in Billions		12 Months Ended
	Jan. 01, 2021 USD ($)	Dec. 31, 2023 EUR (€) Segment	Dec. 31, 2023 USD ($) Segment $ / shares	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($) $ / shares
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments \| Segment		1	1
Tax benefit Percentage		50.00%	50.00%
Percentage of discount recognized on graded-vesting based on stock-based compensation expense over the purchase period		15.00%	15.00%
Advertising costs			$ 28,600	$ 14,600	$ 7,700
Right of use assets			129,952	64,954
Operating lease liabilities			158,810
Increase in convertible notes	$ 96,800
Decrease in accumulated deficit	(60,200)
Decrease in additional paid-in-capital	$ (157,000)
Threshold turnover amount \| €		€ 20
Net loss			$ (535,977)	$ (703,488)	$ (418,780)
Effect on diluted net earnings (loss) per share \| $ / shares			$ (5.8)	$ (8.03)	$ (5.15)
Employee Stock Purchase Plan [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of closing price of common stock		85.00%	85.00%
Patents [Member]
Summary Of Significant Accounting Policies [Line Items]
Initial term of patents			20 years
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer One [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk percentage		40.00%	40.00%	36.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Two [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk percentage		19.00%	19.00%	35.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Three [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk percentage		19.00%	19.00%	12.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Four [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk percentage		12.00%	12.00%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable payment term		60 days	60 days
Right of use assets			$ 94,700
Corporate tax rate					15.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable payment term		100 days	100 days
Maximum [Member] \| Outside of U.S. [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable payment term		150 days	150 days

NET LOSS PER SHARE

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

NET LOSS PER SHARE

20. NET LOSS PER SHARE

Basic net loss per share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding. Diluted net loss per share is computed by dividing net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding. Given that the Company recorded a net loss for each of the periods presented, there is no difference between basic and diluted net loss per share since the effect of common stock equivalents would be anti-dilutive and are, therefore, excluded from the diluted net loss per share calculation.


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands, except per share amounts)
Net loss	$	(535,977	)	$	(703,488	)	$	(418,780	)
Weighted-average common shares outstanding - basic		92,398			87,559			81,262
Effect of dilutive securities*		—			—			—
Weighted-average common shares outstanding - diluted		92,398			87,559			81,262
Net loss per share — basic and diluted	$	(5.80	)	$	(8.03	)	$	(5.15	)

* For the years ended December 31, 2023, 2022 and 2021, stock options, RSAs, RSUs and ESPP to purchase of approximately 12.0 million, 11.2 million and 9.7 million shares of common stock, respectively, were excluded from the net loss per share calculation as their effect would have been anti-dilutive. The Company accounts for the effect of its 2027 Notes and 2024 Notes on diluted net earnings per share (“EPS”) using the if-converted method as this obligation may be settled in cash or shares at the Company’s option. The effect of potential share settlement is included in the diluted EPS calculation if the effect is dilutive. During the years ended December 31, 2023 and 2022, the inclusion of the potential share settlement of the 2027 Notes was anti-dilutive. During the years ended December 31, 2023, 2022 and 2021, the inclusion of the potential share settlement of the 2024 Notes was anti-dilutive. Accordingly, the potential conversion of 1.4 million, 5.7 million and 7.8 million shares related to the 2024 Notes has been excluded from the computation of diluted net loss per share for the years ended December 31, 2023, 2022 and 2021, respectively, and the potential conversion of 8.1 million shares related to the 2027 Notes has been excluded from the computation of diluted net loss per share for the years ended December 31, 2023 and 2022, respectively.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS

Basis of Presentation

The accompanying consolidated financial statements, which have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”), reflect the accounts of Sarepta and its wholly-owned subsidiaries. All intercompany transactions between and among its consolidated subsidiaries have been eliminated. All adjustments of a normal recurring nature necessary for a fair presentation have been reflected.

Segments

Management has determined that the Company operates in one segment: discovering, developing, manufacturing and delivering therapies to patients with rare diseases. The Company’s Chief Executive Officer (“CEO”), as the chief operating decision-maker, manages and allocates resources to the operations of the Company on a total company basis. The Company’s research and development organization is responsible for the research and discovery of new product candidates and supports development and registration efforts for potential future products. The Company’s supply chain organization manages the development of the manufacturing processes, clinical trial supply and commercial product supply. The Company’s commercial organization is responsible for worldwide commercialization of EXONDYS 51, VYONDYS 53 and AMONDYS 45 and domestic commercialization of ELEVIDYS. The Company is supported by other back-office general and administration functions. Consistent with this decision-making process, the Company’s CEO uses consolidated, single-segment financial information for purposes of evaluating performance, forecasting future period financial results, allocating resources and setting incentive targets.

Estimates and Uncertainties

The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, equity, revenue, expenses and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates.

Fair Value Measurements

The Company has certain financial assets and liabilities that are recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements:

•

Level 1—quoted prices for identical instruments in active markets;

•

Level 2—quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets; and

•

Level 3—valuations derived from valuation techniques in which one or more significant value drivers are unobservable.

The fair value of the majority of the Company’s financial assets are categorized as Level 2 within the fair value hierarchy. These assets include commercial paper, government and government agency bonds, corporate bonds and certificates of deposit. For additional information related to fair value measurements, please read Note 5, Fair Value Measurements to the consolidated financial statements.

Cash Equivalents

Only investments that are highly liquid and readily convertible to cash and have original maturities of three months or less at the time of acquisition are considered cash equivalents.

Investments

Available-For-Sale Debt Securities

Available-for-sale debt securities are recorded at fair value and unrealized gains and losses are included in accumulated other comprehensive income (loss) in the consolidated statements of stockholder’s equity. Interest income and realized gains and losses are reported in other income (expense), net, on a specific identification basis. The amortized cost of debt securities are adjusted for amortization of premiums and accretion of discounts to maturity, the net amount of which, along with interest and realized gains and losses, is included in other income (expense), net in the consolidated statements of operations and comprehensive loss.

Equity Investments

The Company’s equity investments include its strategic investments in both publicly traded and private biotechnology companies and are included in other non-current assets in the Company’s consolidated balance sheets. The strategic investment in the publicly traded biotechnology company has a readily determinable fair value and is carried at fair value. The strategic investments in the privately held biotechnology companies do not have readily determinable fair values and are measured at cost less any impairment, plus or minus changes resulting from observable price changes for the identical or a similar investment of the same issuer. Any change in the valuation of equity investments is recorded as a gain or loss on the Company’s consolidated statements of operations and comprehensive loss.

Accounts Receivable, Net

The Company’s accounts receivable, net arise from product sales. They are generally stated at the invoiced amount and do not bear interest.

The accounts receivable, net from product sales represents receivables due from the Company’s specialty distributor and specialty pharmacies in the U.S. as well as certain distributors in the European Union (“EU”), Brazil, Israel, the Middle East and Eastern Europe. The Company has had no material historical write-offs of its accounts receivable, net and its payment terms range from 60 to 100 days for sales within the U.S. and 60 and 150 days for the majority of product sales outside the U.S. The Company monitors the financial performance and creditworthiness of its customers so that it can properly assess and respond to changes in the customers’ credit profiles or any specific issues. The Company provides reserves against trade receivables for expected credit losses that may result from a customer’s inability to pay. Amounts determined to be uncollectible are written-off against the established reserve. As of December 31, 2023, the credit profiles for the Company’s customers are deemed to be in good standing and an allowance for credit losses is not considered necessary.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash held at financial institutions, cash equivalents, investments, and accounts receivable, net. As of December 31, 2023, the Company’s cash was concentrated at three financial institutions, which potentially exposes the Company to credit risks. However, the Company does not believe there is significant risk of non-performance by the financial institutions. The Company also purchases commercial paper, government and government agency bonds, corporate bonds and certificates of deposit issued by highly rated corporations, financial institutions and governments and limits the amount of credit exposure to any one issuer. These amounts may at times exceed federally insured limits. The Company has not experienced any credit losses related to these financial instruments and does not believe to be exposed to any significant credit risk related to these instruments. As of December 31, 2023, four entities accounted for 40%, 19%, 19% and 12% of accounts receivable, net, respectively. As of December 31, 2022, three entities accounted for 36%, 35% and 12% of accounts receivable, net, respectively.

Inventories

Inventories are stated at the lower of cost and net realizable value with cost determined on a first-in, first-out basis. The Company capitalizes inventory costs associated with products following regulatory approval when future commercialization is considered probable and the future economic benefit is expected to be realized. EXONDYS 51, VYONDYS 53, AMONDYS 45 and ELEVIDYS inventory used in clinical development programs is charged to research and development expense when the product enters the research and development process and can no longer be used for commercial purposes.

The Company periodically analyzes its inventories for excess amounts or obsolescence and writes down obsolete or otherwise unmarketable inventory to its estimated net realizable value. Additionally, though the Company’s products are subject to strict quality control and monitoring the Company performs throughout the manufacturing processes, certain batches or units of product may not meet quality specifications. Expense incurred related to excess inventory, obsolete inventory, or inventories that do not meet the Company's quality specifications is recorded as a component of cost of sales in the Company's consolidated statements of operations and comprehensive loss.

For products which are under development and have not yet been approved by regulatory authorities, purchased drug product is charged to research and development expense upon delivery. Delivery occurs when the inventory passes quality inspection and ownership transfers to the Company. Nonrefundable advance payments for research and development activities, including production of purchased drug product, are deferred and capitalized until the goods are delivered. If the Company does not expect the goods to be delivered or services to be rendered, the capitalized advanced payment will be charged to expense.

Property and Equipment

Property and equipment are initially recorded at cost, including the acquisition cost and all costs necessarily incurred to bring the asset to the location and working condition necessary for their intended use. The cost of normal, recurring or periodic repairs and maintenance activities related to property and equipment are expensed as incurred. The cost for planned major maintenance activities, including the related acquisition or construction of assets, is capitalized if the repair will result in future economic benefits. Interest costs incurred during the construction period of major capital projects are periodically reviewed, and if determined to be material, capitalized until the asset is ready for its intended use, at which point the interest costs are amortized as depreciation expense over the life of the underlying asset.

The Company generally depreciates the cost of its property and equipment using the straight-line method over the estimated useful lives of the respective assets, which are summarized as follows:


Asset Category		Useful lives
Lab and manufacturing equipment		5 years
Office equipment		5 years
Software and computer equipment		3 - 5 years
Furniture and fixtures		7 years
Leasehold improvements		Lesser of the useful life or the term of the respective lease
Land improvements		25 years
Land		Not depreciated
Building and improvements		30 years
Construction in progress		Not depreciated until put into service

Intangible assets

The Company’s intangible assets, consisting of in-licensed rights, patent costs and software licenses, are included within other non-current assets in the Company’s consolidated balance sheets.

The in-licensed rights primarily relate to agreements with BioMarin Pharmaceutical, Inc. (“BioMarin”), the University of Western Australia (“UWA”), the Research Institute at Nationwide Children’s Hospital (“NCH”), and Parent Project Muscular Dystrophy (“PPMD”). The in-licensed rights are being amortized on a straight-line basis over the remaining life of the related patents because the life of the related patents reflects the expected time period that the Company will benefit from the in-licensed rights.

Patent costs consist primarily of external legal costs, filing fees incurred to file patent applications and renewal fees on proprietary technology developed or licensed by the Company. Patent costs associated with applying for a patent, being issued a patent and annual renewal fees, costs to defend a patent and costs to invalidate a competitor’s patent or patent application are expensed as incurred. Capitalized patent costs are amortized on a straight-line basis over the shorter of the estimated economic lives or the initial term of the patents, which is generally 20 years.

Impairment of Long-Lived Assets

Long-lived assets held and used by the Company, intangible assets with definite lives and right of use (“ROU”) assets are reviewed for impairment whenever events or circumstances indicate that the carrying amount of the assets may not be recoverable. The Company evaluates recoverability of assets to be held and used by comparing the carrying amount of an asset to future net undiscounted cash flows to be generated by the asset. If the asset is considered to be impaired, the impairment to be recognized is measured as the amount by which the carrying amount of the assets exceeds the fair value of the assets. Such reviews assess the fair value of the assets based upon estimates of future cash flows that the assets are expected to generate.

Convertible Debt

The Company accounts for the liability and equity components of convertible debt instruments that can be settled in cash as a single liability measured at its amortized cost, as long as no other features require bifurcation and recognition as derivatives under ASC Topic 815, Derivatives and Hedging (“ASC 815”). Simultaneously with the issuance of the Company's convertible senior notes due on November 15, 2024 (the “2024 Notes”) and convertible senior notes due on September 15, 2027 (the “2027 Notes”) in November 2017 and September 2022, respectively, the Company bought capped call options from certain counterparties to minimize the impact of potential dilution upon conversion. The premium for the capped call options was recorded as additional paid-in capital. For additional information related to the convertible debt transactions, please read Note 13, Indebtedness to the consolidated financial statements.

Revenue Recognition

The Company recognizes revenue when a customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for the goods or services provided. To determine revenue recognition for arrangements within the scope of ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”), the Company performs the following five steps: (1) identify the contract with the customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when or as the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers or provides to the customer. At contract inception, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when or as the performance obligation is satisfied. The only performance obligation in the Company’s contracts with customers is to timely deliver drug products to the customer’s designated location.

Product revenues

The Company distributes its products principally through its customers or sells directly to sites of care. When the product is distributed through customers, the customers subsequently resell the products to patients and health care providers. The Company provides right of return to the customers only in cases of shipping error or product defect and other limited rights. Product revenues are recognized when the customers take control of the products, which typically occurs upon delivery or shipment. For information related to revenues by product type and region, please read Note 7, Product Revenues, Net, Accounts Receivable, Net and Reserves for Product Revenues to the consolidated financial statements.

Variable Consideration

Product revenues are recorded at the net sales price (transaction price) which includes reserves for variable consideration such as: rebates and chargebacks, distribution fees, prompt pay discounts, patient assistance and return reserves. These reserves, representing the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the contracts, are based on the amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable if no payments are required of the Company or a current liability if a payment is required of the Company. Where appropriate, the estimates reflect the Company’s historical experience, contractual and statutory requirements, industry data and forecasted customer buying and payment patterns. Actual amounts may differ from the Company’s estimates. If actual results vary, these estimates are adjusted, which could have an effect on earnings in the period of adjustment.

Additional details relating to variable consideration are as follows:

•

Rebates and chargebacks: relating to governmental and commercial rebates and governmental chargebacks. Governmental rebates, including Medicaid-rebates relate to the Company’s estimated obligations to states under established reimbursement arrangements. The commercial rebates relate to arrangements the Company enters into with payors that provide for privately-negotiated rebates. Rebate reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a liability which is included in accrued expenses. Governmental chargebacks, including Public Health Services (“PHS”) chargebacks, relate to the Company’s estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices that the Company charges to wholesalers. The wholesaler charges the Company for the difference between what the wholesaler pays for the products and the ultimate selling price to the qualified healthcare providers. Chargeback reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider from the wholesaler, and the Company generally issues credits for such amounts within a few weeks of receiving notification of resale from the wholesaler.

•

Distribution fees: relating to fees paid to customers in the distribution channel that provide the Company with inventory management, data and distribution services and are generally accounted for as a reduction of revenue. To the extent that the services received are distinct from the Company’s sale of products to the customers, these payments are accounted for as selling, general and administrative expenses. Reserves for distribution fees result in an increase in a liability if payments are required of the Company or a reduction of accounts receivable if no payments are required of the Company.

•

Prompt payment discounts: relating to the Company’s estimated obligations for credits to be granted to specialty pharmacies for remitting payment on their purchases within established incentive periods. Reserves for prompt payment discounts are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable.

•

Patient assistance: relating to financial assistance programs provided to qualified patients. Reserves for costs related to patient assistance programs are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a liability which is included in accrued expenses.

•

Return reserves: relating to the limited return rights the Company provides to customers. The Company records product return reserve, if appropriate, as a reduction of revenue at the time product sales are recorded. Several factors are considered in determining whether return reserves are required, including the patient population and the customers’ limited return rights, etc. Because of the pricing, the limited number of patients, and the customers’ limited return rights, most customers only carry a limited inventory. Based on these factors and the fact that the Company has not experienced significant product returns to date, return allowances are immaterial at December 31, 2023.

Collaboration revenue

The Company’s collaboration revenue is primarily generated from its collaboration arrangement with F. Hoffman-La Roche Ltd. (“Roche”). For more information, please read Note 3, License and Collaboration Agreements. At the inception of a collaboration arrangement, the Company first assesses whether the contractual arrangement is within the scope of ASC Topic 808, Collaborative Arrangements to determine whether the arrangement involves a joint operating activity and involves two (or more) parties that are both active participants in the activity and exposed to significant risks and rewards dependent on the commercial success of such activity. Then the Company determines whether the collaboration arrangement in its entirety represents a contract with a customer as defined by ASC 606. If only a portion of the collaboration arrangement is potentially with a customer, the Company applies the distinct good or service unit-of-account guidance in ASC 606 to determine whether there is a unit of account that should be accounted for under ASC 606. For the units of account in the collaboration arrangement that do not represent a vendor-customer relationship, the

Company will (i) consider applying other GAAP, including by analogy, or (ii) if there is no appropriate analogy, consistently apply a reasonable and rational accounting policy election.

In general, by analogy to ASC 606, the Company identifies the performance obligations within the collaboration arrangement and identifies and allocates the transaction price the Company expects to receive on a relative standalone selling price basis to each performance obligation. Variable consideration, consisting of development and regulatory milestones, will be included in the transaction price only if the Company expects to receive such consideration and if it is probable that the inclusion of the variable consideration will not result in a significant reversal in the cumulative amount of revenue recognized under the arrangement. Sales-based royalty and milestone payments are excluded from the transaction price the Company expects to receive until the underlying sales occur because the license to the Company’s intellectual property is deemed to be the predominant item to which the royalties or milestones relate as it is the primary driver of value in its collaboration arrangement.

For the recognition of revenue associated with each performance obligation, if the Company determines ASC 606 is not appropriate to apply by analogy, the Company will apply a reasonable, rational and consistently applied accounting policy election to faithfully depict the transfer of services to the collaboration partner over the estimated performance period. Up-front payments from a collaboration partner are recognized as deferred revenue when received and recognized as revenue over the estimated performance period. Reimbursement payments from a collaboration partner associated with cost-sharing provisions in a collaboration arrangement are recognized as the related expense is incurred and classified as an offset to operating expenses. Revenue from product supply sold to collaboration partners under a collaboration arrangement via contract manufacturing is included as collaboration and other revenues on the consolidated statements of operations and comprehensive loss.

Valuation of Product Options

The Company's collaboration arrangements may contain options which provide the collaboration partner with the right to obtain additional licenses. If an arrangement contains product options, by analogy to ASC 606, the Company evaluates the product options to determine whether they represent material rights, which may include options to acquire additional goods or services for free or at a discount. If the customer options are determined to represent material rights, they are recognized as a separate performance obligation at inception of the arrangement. The Company allocates a portion of the transaction price of the collaboration arrangement to material rights based on the relative standalone selling price. Amounts allocated to material rights are not recognized as revenue until related options are exercised or expire. Key assumptions to determine the standalone selling price of product options in a collaboration arrangement include, but are not limited to, forecasted revenues, development timelines, incremental costs related to the arrangement, discount rates and likelihood of technical and regulatory success.

Research and Development

Research and development expenses consist of costs associated with research activities as well as those with the Company’s product development efforts, conducting pre-clinical trials, clinical trials and manufacturing activities. Research and development expenses are expensed as incurred. Up-front fees and milestones paid to third parties in connection with technologies which have not reached technological feasibility and do not have an alternative future use are expensed when incurred.

Direct research and development expenses associated with the Company’s programs include clinical trial site costs, clinical manufacturing costs, costs incurred for consultants and other external services, such as data management and statistical analysis support and materials and supplies used in support of clinical programs. Indirect costs of the Company’s clinical programs include salaries, stock-based compensation and an allocation of its facility and technology costs.

When third-party service providers’ billing terms do not coincide with the Company’s period-end, the Company is required to make estimates of its obligations to those third parties, including clinical trial and pharmaceutical development costs, contractual services costs and costs for supply of its drug candidates incurred in a given accounting period, and record accruals at the end of the period. The Company bases its estimates on its knowledge of the research and development programs, services performed for the period, past history for related activities and the expected duration of the third-party service contract, where applicable.

Selling, General and Administrative Expenses

Selling, general and administrative expenses consist of salaries, benefits, stock-based compensation and related costs for personnel in the Company's executive, finance, legal, information technology, business development, human resources, commercial and other general and administrative functions. Other general and administrative expenses include an allocation of the Company's facility- and technology-related costs and professional fees for legal, consulting and accounting services.

Advertising costs are included in selling, general and administrative expenses and are expensed as incurred. The Company considers advertising costs as expenses related to the promotion of the Company's commercial products. For the years ended December 31, 2023, 2022 and 2021, advertising costs totaled $28.6 million, $14.6 million and $7.7 million, respectively.

Stock-Based Compensation

The Company’s stock-based compensation programs include stock options, restricted stock units (“RSUs”), RSU shares with performance conditions (“PSUs”) and an employee stock purchase program (“ESPP”). The Company accounts for stock-based compensation using the fair value method.

The fair value of stock options are estimated on the date of grant using the Black-Scholes-Merton option-pricing model. The fair values of PSUs and RSUs are based on the fair market value of the Company’s common stock on the date of the grant. The fair value of stock awards, with consideration given to estimated forfeitures, is recognized as stock-based compensation expense on a straight-line basis over the vesting period of the grants. The Company estimates forfeitures over the requisite service period using historical forfeiture activity. For stock awards with performance-vesting conditions, the Company does not recognize compensation expense until it is probable that the performance condition will be achieved.

Additionally, the Company granted its CEO options with service and market conditions. A market condition relates to the achievement of a specified price of the Company’s common stock, a specified amount of intrinsic value indexed to the Company’s common stock or a specified price of the Company’s common stock in terms of other similar equity shares. The grant date fair value for the options with service and market conditions is determined by a lattice model with Monte Carlo simulations and is recognized as stock-based compensation expense on a straight-line basis over the respective derived service period.

Under the Company’s ESPP, participating employees purchase common stock through payroll deductions. The purchase price is equal to 85% of the lower of the closing price of the Company’s common stock on the first business day and the last business day of the relevant purchase period. The fair value of stock purchase rights is estimated using the Black-Scholes-Merton option-pricing model. The fair value of the look-back provision with the 15% discount is recognized on a graded-vesting basis as stock-based compensation expense over the purchase period.

Income Taxes

The Company follows the asset and liability method of accounting for income taxes, which requires the recognition of deferred tax assets and liabilities for expected future tax consequences attributable to differences between the consolidated financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates in effect for the year in which the differences are expected to reverse. A valuation allowance is recorded to reduce the net deferred tax asset to zero when it is more likely than not that the net deferred tax asset will not be realized.

The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained upon an examination. The amount of the benefit that may be recognized in the financial statements is the largest amount that has a greater than 50% likelihood of being realized. The Company recognizes interest and penalties related to uncertain tax positions within income tax expense.

It is the intention of the Company to reinvest the earnings of its non-U.S. subsidiaries in those operations and not to repatriate the earnings to the U.S. Accordingly, the Company does not provide for deferred taxes on the excess of the financial reporting over the tax basis in its investments in foreign subsidiaries as they are considered permanent in duration.

Effective December 31, 2021, the Company adopted a policy to account for Global Intangible Low-Taxed Income (“GILTI”) as a period cost under the Tax Cuts and Jobs Act. In 2021, the Organization for Economic Co-operation and Development (“OECD”) released a framework for the fundamental reform of international tax rules. The framework provides for two primary “Pillars”; however, only Pillar Two, which provides for a global minimum corporate tax rate of 15%, is expected to be applicable to the Company (Pillar One is not expected to be applicable as the Company does not currently meet the turnover threshold - EUR 20 billion). In December 2022, Pillar Two was adopted by the Council of the European Union for implementation by European Union member states by December 31, 2023, with effect for tax years beginning in calendar year 2024. The OECD, and its member countries, continue to release new guidance on these rules and the Company is continuously evaluating the impact to its financial position. Currently, the global enactment of Pillar Two is not expected to materially impact the Company's effective tax rate or cash flows. However, the Company will continue to monitor and evaluate new legislation and guidance, which could change its current assessment.

Leases

At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than 12 months are recognized on the

consolidated balance sheets as ROU assets and short-term and long-term lease liabilities, as applicable. The Company has elected not to recognize leases with terms of 12 months or less on the consolidated balance sheets. The Company typically only includes an initial lease term in its assessment of a lease arrangement. Options to renew a lease are not included in the Company’s assessment unless there is reasonable certainty that the Company will renew. The Company monitors its plans to renew its leases quarterly or on an as-needed basis. In addition, the Company’s lease agreements generally do not contain any residual value guarantees or restrictive covenants.

Operating lease liabilities and their corresponding ROU assets are recorded based on the present value of future lease payments over the expected remaining lease term at lease commencement. The initial measurement of the lease liability is determined based on the future lease payments, which may include lease payments that depend on an index or a rate (such as the consumer price index or other market index). The Company initially measures payments based on an index or rate by using the applicable rate at lease commencement and subsequent changes in such rates are recognized as variable lease costs. Variable payments that do not depend on a rate or index are not included in the lease liability and are recognized as they are incurred. Lease costs for operating leases are recognized on a straight-line basis over the lease term as an operating expense with unrecognized variable lease payments recognized as incurred. Certain adjustments to the ROU asset may be required for items such as lease prepayments or incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate, which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. Components of a lease are bifurcated between lease components and non-lease components. The fixed and in-substance fixed contract consideration identified is then allocated based on the relative standalone price to the lease and non-lease components. The Company adopted a practical expedient provided by ASC Topic 842, Leases, and elected to account for the lease and non-lease components together for existing classes of underlying assets and allocates the contract consideration to the lease component only. In contrast, the Company does not apply the practical expedient for leases embedded in manufacturing and supply agreements with certain of its contract manufacturing organizations and has instead allocated contract consideration between the lease and non-lease components based on their relative standalone price.

Embedded Derivatives

The Company evaluates certain of its financial and business development transactions to determine if embedded components of these contracts meet the definition of derivative under ASC 815. In general, embedded derivatives are required to be bifurcated from the host instrument if (i) the embedded feature is not clearly and closely related to the host contract and (ii) the embedded feature, if considered a freestanding instrument, meets the definition of a derivative. The embedded derivative is reported on the consolidated balance sheets at its fair value. Any change in fair value, as determined at each measurement period, is recorded as a component of the consolidated statements of operations and comprehensive loss.

Contingent Consideration

Certain of the Company’s license and collaboration agreements include future payments that are contingent upon the receipt, or receipt and subsequent sale, of a Priority Review Voucher (“PRV”). The Company has concluded that these contingent payments represent embedded derivatives. The Company records a liability for such contingent payments at fair value on the date the agreements are effective. The Company estimates the fair value of contingent consideration derivatives through a valuation model that includes an income approach based on the probability-weighted expected cash flows that incorporated industry-based probability adjusted assumptions relating to the achievement of the milestone and thus the likelihood of making the payments. Changes in the fair value of the contingent consideration derivatives can result from changes to one or multiple assumptions, including adjustments to the discount rates, the assumed development timeline and the probability of achievement of certain regulatory milestones. At least quarterly, or upon a material change to one or more of the assumptions discussed above, the Company assesses its contingent consideration derivatives and revalues as necessary. If a revaluation occurs, changes in the fair value of the Company’s contingent consideration derivatives are recognized in the Company’s consolidated statements of operations and comprehensive loss. Such changes are classified as other income (loss), net, which corresponds to the classification of any gain recognized upon the actual sale of a PRV.

Commitments and Contingencies

The Company records liabilities for legal and other contingencies when information available to the Company indicates that it is probable that a liability has been incurred and the amount of loss can be reasonably estimated. Legal costs in connection with legal and other contingencies are expensed as costs are incurred as selling, general and administrative expenses.

Recent Accounting Pronouncements

Recently adopted

In August 2020, the Financial Accounting Standards Board (“FASB”) issued ASU 2020-06, “Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity's Own Equity (Subtopic 815-40): Accounting

for Convertible Instruments and Contracts in an Entity's Own Equity.” This ASU simplifies the complexity associated with applying U.S. GAAP for certain financial instruments with characteristics of liabilities and equity. More specifically, the amendments focus on the guidance for convertible instruments and derivative scope exceptions for contracts in an entity’s own equity. Under ASU 2020-06, the embedded conversion features are no longer separated from the host contract for convertible instruments with conversion features that are not required to be accounted for as derivatives under ASC 815, or that do not result in substantial premiums accounted for as paid-in capital. Consequently, a convertible debt instrument, such as the 2024 Notes or the 2027 Notes, will be accounted for as a single liability measured at its amortized cost, as long as no other features require bifurcation and recognition as derivatives. The new guidance also requires the if-converted method to be applied for all convertible instruments and requires additional disclosures. The Company elected to early adopt this guidance on January 1, 2021, using the modified retrospective method. Under this transition method, the cumulative effect of the accounting change removed the impact of recognizing the equity component of the Company’s convertible notes (at issuance and the subsequent accounting impact of additional interest expense from debt discount amortization). The cumulative effect of the accounting change as of January 1, 2021 increased the carrying amount of the convertible notes by $96.8 million, reduced accumulated deficit by $60.2 million and reduced additional paid-in capital by $157.0 million. The if-converted method for such instruments is used to compute diluted net earnings per share if and when profitability is achieved.

Recently issued

In November 2023, the FASB issued ASU 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures” which is intended to improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant expenses. The amendments will require public entities to disclose significant segment expenses that are regularly provided to the chief operating decision maker and included within segment profit and loss. The amendments are effective for the Company's fiscal years beginning after December 15, 2023 and interim periods beginning after December 15, 2024, with early adoption permitted, and will be applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the ASU to determine its impact on the Company's disclosures.

In December 2023, FASB issued ASU 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.” This ASU enhances the transparency and decision usefulness of income tax disclosures, primarily related to the rate reconciliation and income taxes paid information. ASU 2023-09 is effective for fiscal years beginning after December 15, 2024 and may be adopted on a prospective or retrospective basis. Early adoption is permitted. The Company is evaluating the impact of this guidance on its consolidated financial statements and related disclosures.

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Products, net	$ 1,144,876	$ 843,769	$ 612,401
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Collaboration and other	$ 98,460	$ 89,244	$ 89,486
Total revenues	1,243,336	933,013	701,887
Cost and expenses:
Cost of sales (excluding amortization of in-licensed rights)	150,343	139,989	97,049
Research and development	877,387	877,090	771,182
Selling, general and administrative	481,871	451,421	282,660
Settlement and license charges	0	0	10,000
Amortization of in-licensed rights	1,559	714	706
Total cost and expenses	1,511,160	1,469,214	1,161,597
Operating loss	(267,824)	(536,201)	(459,710)
Other (loss) income, net:
Loss on debt extinguishment	(387,329)	(125,441)	0
Gain from sale of Priority Review Voucher	102,000	0	102,000
Other income (expense), net	33,055	(28,321)	(61,238)
Total other (loss) income, net	(252,274)	(153,762)	40,762
Total	(520,098)	(689,963)	(418,948)
Income tax expense (benefit)	15,879	13,525	(168)
Net loss	(535,977)	(703,488)	(418,780)
Other comprehensive income (loss):
Unrealized gains (losses) on investments, net of tax	2,582	(1,644)	(23)
Total other comprehensive income (loss)	2,582	(1,644)	(23)
Comprehensive loss	$ (533,395)	$ (705,132)	$ (418,803)
Net loss per share - basic	$ (5.8)	$ (8.03)	$ (5.15)
Net loss per share - diluted	$ (5.8)	$ (8.03)	$ (5.15)
Weighted average number of shares of common stock used in computing basic net loss per share	92,398	87,559	81,262
Weighted average number of shares of common stock used in computing diluted net loss per share	92,398	87,559	81,262

Stock Based Compensation - Assumptions for Measuring Fair Values of Stocks (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Expected dividend yield	0.00%

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

Segments

Estimates and Uncertainties

Fair Value Measurements

•

Level 1—quoted prices for identical instruments in active markets;

•

Level 3—valuations derived from valuation techniques in which one or more significant value drivers are unobservable.

Cash Equivalents

Only investments that are highly liquid and readily convertible to cash and have original maturities of three months or less at the time of acquisition are considered cash equivalents.

Investments

Available-For-Sale Debt Securities

Equity Investments

Accounts Receivable

Accounts Receivable, Net

The Company’s accounts receivable, net arise from product sales. They are generally stated at the invoiced amount and do not bear interest.

Concentration of Credit Risk

Inventories

Property and Equipment

The Company generally depreciates the cost of its property and equipment using the straight-line method over the estimated useful lives of the respective assets, which are summarized as follows:


Asset Category		Useful lives
Lab and manufacturing equipment		5 years
Office equipment		5 years
Software and computer equipment		3 - 5 years
Furniture and fixtures		7 years
Leasehold improvements		Lesser of the useful life or the term of the respective lease
Land improvements		25 years
Land		Not depreciated
Building and improvements		30 years
Construction in progress		Not depreciated until put into service

Intangible assets

The Company’s intangible assets, consisting of in-licensed rights, patent costs and software licenses, are included within other non-current assets in the Company’s consolidated balance sheets.

Impairment of Long-Lived Assets

Convertible Debt

Revenue Recognition

Product revenues

Variable Consideration

Additional details relating to variable consideration are as follows:

•

Collaboration revenue

Company will (i) consider applying other GAAP, including by analogy, or (ii) if there is no appropriate analogy, consistently apply a reasonable and rational accounting policy election.

Valuation of Product Options

Research and Development

Selling, General and Administrative Expenses

Stock-Based Compensation

Income Taxes

Leases

Embedded Derivatives

Contingent Consideration

Commitments and Contingencies

Recent Accounting Pronouncements

Recently adopted

Recently issued

LICENSE AND COLLABORATION AGREEMENTS

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

LICENSE AND COLLABORATION AGREEMENTS

3. LICENSE AND COLLABORATION AGREEMENTS

F. Hoffman-La Roche Ltd.

On December 21, 2019, the Company entered into a license, collaboration and option agreement with Roche and a stock purchase agreement (the “Roche Agreement”) with Roche, providing Roche with exclusive commercial rights to ELEVIDYS outside the U.S. The Company retains all rights to ELEVIDYS in the U.S. and will perform all development activities within the joint global development plan necessary to obtain and maintain regulatory approvals for ELEVIDYS in the U.S. and the EU, unless otherwise agreed to by the parties. Further: (i) research and development expenses incurred under the joint global development plan will be equally shared between the Company and Roche, (ii) Roche is solely responsible for all costs incurred in connection with any development activities (other than those within the joint global development plan) that are necessary to obtain or maintain regulatory approvals outside the U.S, and (iii) the Company will continue to be responsible for the manufacturing of clinical and commercial supplies of ELEVIDYS. The Company has also granted Roche options to acquire ex-U.S. rights to certain future Duchenne-specific programs (the “Options”) in exchange for separate option exercise payments, milestone and royalty considerations, and cost-sharing provisions. The agreement became effective on February 4, 2020. The Roche Agreement is governed by a joint steering committee (“JSC”) formed by representatives from Roche and the Company. The JSC, among other activities, manages the overall strategic alignment between the parties, approves any material update to the joint global development plan and budget and oversees the operations of the subcommittees.

The Company received an aggregate of approximately $1.2 billion in cash consideration from Roche, consisting of an up-front payment and an equity investment in the Company. The Company may receive up to $1.7 billion in development, regulatory and sales milestones related to ELEVIDYS. Upon commercial sale of ELEVIDYS outside of the U.S., the Company will become eligible to receive tiered royalty payments on net sales based on the average cost to manufacture ELEVIDYS. Of the $1.2 billion up-front cash received from Roche, (i) $312.1 million, net of issuance costs, was allocated to the approximately 2.5 million shares of the Company’s common stock issued to Roche based on the closing price when the shares were issued, (ii) $485.0 million was allocated to the Options, and (iii) $348.7 million was allocated to a single, combined performance obligation (“Combined Performance Obligation”) comprised of: (i) the license of IP relating to ELEVIDYS transferred to Roche, (ii) the related research and development services provided under the joint global development plan, (iii) the services provided to manufacture clinical supplies of ELEVIDYS, and (iv) the Company’s participation in the JSC, because the Company determined that the license of IP and related activities were not capable of being distinct from one another.

The value assigned to the Options is reflected as deferred revenue and will not be recognized until an option is either: (i) exercised by Roche, or (ii) expires. If exercised, the value will be aggregated with the option exercise price and recognized over the applicable performance period. If expired, the value will be recognized immediately. The Company recognizes revenue related to the Combined Performance Obligation on a straight-line basis over the expected performance period of the joint global development plan, which extended through the fourth quarter of 2023. Revenue relating to future development, regulatory and sales milestones will be recognized when the milestone is probable of achievement (which is typically when the milestone has occurred). Any royalties payable by Roche in the future will be recognized in the period earned.

For the years ended December 31, 2023, 2022 and 2021, the Company recognized $98.5 million, $89.2 million and $89.5 million of collaboration and other revenues, respectively, the majority of which relates to the amortization of the Combined Performance Obligation. As of December 31, 2023, the fair value allocated to Combined Performance Obligation was fully amortized.

As of December 31, 2023, the Company has total deferred revenue of $487.4 million, which is primarily associated with the Roche Agreement, of which $50.4 million is classified as current. Through 2023, no Options were exercised or expired. As such, deferred revenue related to the separate material rights for the Options remained unchanged at $485.0 million as of December 31, 2023 and 2022. On February 12, 2024, Roche declined to exercise a certain Option, which resulted in that Option's expiry and the immediate recognition of the value assigned to that Option as collaboration revenue. As such, the Company will recognize $48.0 million of collaboration revenue during the three months ended March 31, 2024 and as of December 31, 2023, this amount is appropriately classified as deferred revenue, current portion, on the Company's consolidated balance sheets.

In accordance with the Roche Agreement, the parties agreed to enter into a supply agreement with Roche in order to supply them with clinical and commercial batches of ELEVIDYS (the “Supply Agreement”). While the Supply Agreement is in the process of being negotiated, the Company delivered several batches of commercial ELEVIDYS supply to Roche that were agreed upon on a purchase order-by-purchase order basis. For the year ended December 31, 2023, the Company recognized $9.2 million of contract manufacturing revenue related to these shipments, with no similar activity for the years ended December 31, 2022 or 2021. This revenue is included in collaboration and other revenues in the consolidated statements of operations and comprehensive loss. For the year ended December 31, 2023, the Company recognized $1.8 million of inventory costs related to these shipments, which is included in costs of goods sold in the consolidated statements of operations and comprehensive loss. As of December 31, 2023, there was $7.1 million of contract manufacturing collaboration receivable included in other current assets on the consolidated balance sheets.

The costs associated with co-development activities performed under the Roche Agreement are included in operating expenses, with any reimbursement of costs by Roche reflected as a reduction of such expenses when the related expense is incurred. For the years ended December 31, 2023, 2022 and 2021, costs reimbursable by Roche and reflected as a reduction to operating expenses were $106.9 million, $117.8 million and $90.5 million, respectively. As of December 31, 2023 and 2022, there was $29.8 million and $41.8 million of collaboration and other receivables included in other current assets on the consolidated balance sheets, respectively.

Genethon

The Company entered into a sponsored research agreement in May 2017 and subsequently entered into a license and collaboration agreement with Genethon in November 2019 (the “Genethon Collaboration Agreement”) for Genethon’s micro-dystrophin gene therapy program for the treatment of Duchenne. The Genethon Collaboration Agreement grants the Company with exclusive rights in the majority of the world (primarily excluding the EU) to Genethon’s micro-dystrophin gene therapy products (“Genethon Products”) and other micro-dystrophin gene therapy products (“Other Licensed Products”). The Company may be liable for up to $157.5 million and $78.8 million in development, regulatory and sales milestones for the Genethon Products and Other Licensed Products, respectively. Furthermore, upon commercialization, the Company will be required to make tiered royalty payments based on net sales of the Genethon Products and the Other Licensed Products. Under the Genethon Collaboration Agreement, a joint steering committee was established to plan, monitor and coordinate development activities for Genethon Products and Other Licensed Products. The Company and Genethon are responsible for 75% and 25%, respectively, of development costs related to both the Genethon Products and the Other Licensed Products.

Upon signing the Genethon Collaboration Agreement, the Company made an up-front payment of $28.0 million, which was recorded as research and development expense in the Company’s consolidated statements of operations and comprehensive loss for the year ended December 31, 2019. Additionally, for the years ended December 31, 2023, 2022 and 2021, the Company recorded $6.6 million, $3.5 million and $11.7 million, respectively, of research and development expense related to reimbursable development costs incurred by Genethon for Genethon Products. For the year ended December 31, 2021, the Company recorded $4.0 million of research and development expense related to milestone achievements, with no similar activity during for the years ended December 31, 2023 and 2022. No additional development or regulatory milestones were deemed probable of being achieved and, accordingly, no additional expense has been recognized.

Myonexus Therapeutics Inc.

In April 2019, the Company completed its acquisition of Myonexus Therapeutics, Inc. (“Myonexus”), a clinical-stage gene therapy biotechnology company that was developing gene therapies for LGMD for $178.3 million. The Company may also be required to make up to $200.0 million in additional payments to selling shareholders of Myonexus based on the achievement of certain sales-and regulatory- related milestones. The acquisition was accounted for as an asset acquisition as substantially all of the fair value of the gross assets acquired is concentrated in a group of similar identifiable assets (the five LGMD gene therapy programs). The Company determined that one regulatory-related milestone (not solely based on drug approval by the FDA) met the definition of a derivative and recorded a contingent consideration liability. As of December 31, 2023 and 2022, the contingent consideration liability was $37.7 million and $35.5 million, respectively. The changes in fair value are recorded within other income (expense), net, in the Company’s consolidated statements of operations and comprehensive loss. Please read Note 5, Fair Value Measurements for further information on the change in fair value of the contingent consideration liability.

Lacerta Therapeutics

In August 2018, the Company entered into a license, development and option agreement (the “Lacerta License Agreement”) and a Series A Preferred Stock Purchase Agreement (the “Lacerta Stock Purchase Agreement”) with Lacerta Therapeutics, Inc. (“Lacerta”). The Lacerta License Agreement was terminated on May 8, 2023. The Company is no longer liable for any remaining development, regulatory and sales milestones associated with the Pompe License and is no longer required to make tiered royalty payments based on net sales of the Pompe product subsequent to its commercialization following termination of the Lacerta License Agreement.

Under the Lacerta Stock Purchase Agreement, the Company purchased approximately 4.5 million shares of Series A preferred stock issued by Lacerta. Of the up-front payment of $38.0 million paid to Lacerta, $30.0 million was allocated to the Series A preferred stock investment and recorded as an other non-current asset in the accompanying consolidated balance sheets. Changes in the carrying value of the investment are reported as a component of earnings whenever there are triggering events that warrant impairment or observable price changes in orderly transactions for identical or similar investments of Lacerta in the future. For the year ended December 31, 2023, the Company fully wrote off its investment in Series A preferred stock of Lacerta and recorded an impairment loss of $30.0 million. For more information related to the Company's investment in Lacerta and the impairment incurred during the year ended December 31, 2023, please refer to Note 5, Fair Value Measurements.

Nationwide Children’s Hospital

In December 2016, the Company entered into an exclusive option agreement with Nationwide from which the Company obtained an exclusive right to acquire a worldwide license of the micro-dystrophin gene therapy technology for Duchenne and Becker muscular dystrophy. In October 2018, the Company exercised the option and entered into a license agreement with Nationwide, which granted the Company exclusive worldwide rights to develop, manufacture and commercialize a micro-dystrophin gene therapy product candidate. Under this agreement, the Company is liable for future regulatory milestone, sales milestone and sublicense payments as well as lower single-digit royalties upon commercialization.

In July 2021, the Company entered into an agreement with Nationwide, settling a dispute relating to a sublicense payment owed by the Company resulting from the up-front payment received from Roche under the Roche Agreement and paid Nationwide $38.0 million. As a result of this payment, the Company has no further financial obligations to Nationwide resulting from the up-front payment received under the Roche Agreement.

During the year ended December 31, 2023, the Company recorded $23.0 million as an in-licensed right intangible asset in its consolidated balance sheets, $10.0 million of which related to the regulatory approval of ELEVIDYS, and the remaining related to sales-based milestones as the Company determined that all sales-based milestones were achieved or were probable of being achieved. As of December 31, 2023, the in-licensed right asset with a net carrying value of $22.2 million is being amortized on a straight-line basis over the remaining life of the relevant patent. Royalty payments due to Nationwide associated with commercial sales of ELEVIDYS totaled $6.0 million for the year ended December 31, 2023 and were recorded as cost of sales in the accompanying consolidated statements of operations and comprehensive loss.

BioMarin Pharmaceutical, Inc.

In July 2017, the Company and UWA entered into a settlement agreement with BioMarin, and simultaneously entered into a license agreement, which was subsequently amended in April 2019 (the “BioMarin Agreement”), with BioMarin and Academisch Ziekenhuis Leiden (collectively with the Company, UWA and BioMarin, the “Settlement Parties”). The BioMarin Agreement provides the Company with an exclusive license to certain intellectual property with an option to convert the exclusive license into a co-exclusive license and the Settlement Parties agreed to stop most existing efforts to continue with ongoing litigation and opposition and other administrative proceedings concerning BioMarin’s intellectual property. BioMarin is also eligible to receive tiered royalty payments, ranging from 4% to 8%, based on the net sales for the three products and product candidates.

In November 2021, the Company entered into a second settlement agreement and second amendment to the license agreement (the “Second Amendment”), which waived certain future milestone payments and altered royalty payment terms of the agreement. Under the Second Amendment, the Company may be liable for up to approximately $50.0 million in regulatory milestones for eteplirsen, casimersen and golodirsen. In addition, on and after July 1, 2022, the tiered royalty payments ranged from 4% to 5%. The royalty terms under the license agreement will expire in March 2024 in the U.S., December 2024 in the EU and no later than December 2024 in other countries.

As a result of the execution of the license agreement with BioMarin, the Company recorded an in-licensed right intangible asset of $6.6 million in its consolidated balance sheets as of December 31, 2017, representing the fair value of the U.S. license to BioMarin’s intellectual property. The intangible asset is being amortized on a straight-line basis over the remaining life of the patent and has a carrying value of $2.3 million as of December 31, 2023.

The FDA approval of AMONDYS 45 in February 2021 resulted in a settlement charge to BioMarin of $10.0 million during the year ended December 31, 2021 and was expensed as incurred. For the years ended December 31, 2023, 2022 and 2021, the Company recognized royalty expense of $17.6 million, $30.4 million and $31.4 million, respectively, which is included in cost of sales in the accompanying consolidated statements of operations and comprehensive loss. For the year ended December 31, 2023, no other regulatory milestones were deemed probable of being achieved and, accordingly, no additional in-licensed rights or expenses have been recognized.

University of Western Australia

In April 2013, the Company and UWA entered into an amendment to an existing exclusive license agreement relating to the treatment of Duchenne by inducing the skipping of certain exons. The agreement was further amended in June 2016. Under the amended agreement, the Company may be obligated to make payments to UWA totaling up to $26.0 million upon the achievement of certain development, regulatory and sales milestones. Additionally, the Company is required to pay a low-single-digit percentage royalty on net sales of products covered by issued patents licensed under the agreements with UWA. Corresponding to the FDA approval of EXONDYS 51 in 2016, VYONDYS 53 in 2019, and AMONDYS 45 in 2021, the Company recorded milestone payments of $1.0 million, $0.5 million and $0.5 million as in-licensed right intangible assets in its consolidated balance sheets, respectively. Each in-licensed right is being amortized on a straight-line basis over the remaining life of the relevant patents and have a combined carrying value of $0.7 million as of December 31, 2023. For the years ended December 31, 2023, 2022 and 2021, the Company recorded $11.8 million, $10.5 million and $7.7 million in royalty expense, respectively, which is included in cost of sales, related to agreements with UWA. For the year ended December 31, 2023, no other development, regulatory or sales milestones were deemed probable of being achieved and, accordingly, no additional in-licensed rights or expenses have been recognized.

Research and Option Agreements

The Company has research and option agreements with third parties in order to develop various technologies and biologics that may be used in the administration of the Company’s genetic therapeutics. The agreements generally provide for research services related to pre-clinical development programs and options to license the technology for clinical development. Prior to the options under these agreements being executed, the Company may be required to make up to $34.8 million in research milestone payments. Under these agreements, there are $165.8 million in potential option payments to be made by the Company upon the determination to exercise the options. Additionally, if the options for each agreement are executed, the Company would incur additional contingent obligations and may be required to make development, regulatory, and sales milestone payments and tiered royalty payments based on the sales of the developed products upon commercialization.

For the years ended December 31, 2023, 2022 and 2021, the Company recognized $5.1 million, $6.0 million, and $3.0 million in research, option and milestone expense as research and development expense in the accompanying consolidated statements of operations and comprehensive loss, respectively. For the years ended December 31, 2023 and 2022, the Company exercised options in a research and option agreement and recognized $7.5 million and $8.5 million, respectively, of up-front expense as research and development expense in the accompanying consolidated statements of operations and comprehensive loss, separately from the research, option and milestone expense listed above. No option exercise payments were made during the year ended December 31, 2021.

Milestone Obligations

Including the agreements discussed above, the Company has license and collaboration agreements in place for which it could be obligated to pay, in addition to the payment of up-front fees upon execution of the agreements, certain milestone payments as a product candidate proceeds from the submission of an investigational new drug application through approval for commercial sale and beyond. As of December 31, 2023, the Company may be obligated to make up to $3.2 billion of future development, regulatory, commercial, and up-front royalty payments associated with its collaboration and license agreements. These obligations exclude potential future option and milestone payments for options that have yet to be exercised within agreements entered into by the Company as of December 31, 2023, which are discussed above. For the years ended December 31, 2023, 2022 and 2021, the Company recognized approximately $13.2 million, $32.6 million and $50.3 million relating to certain up-front, milestone, settlement and other payments as research and development expense, respectively, under these agreements.

Inventory - Summary of Components of Inventory (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Raw materials	$ 133,963	$ 59,181
Work in progress	318,458	269,185
Finished goods	61,806	38,147
Total inventory	$ 514,227	$ 366,513

OTHER ASSETS

12 Months Ended

Dec. 31, 2023

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

OTHER ASSETS

9. OTHER ASSETS

The following table summarizes the Company’s other current assets for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Manufacturing-related deposits and prepaids	$	102,181	$	66,455
Collaboration and other receivables		29,786		41,758
Prepaid maintenance services		11,281		9,815
Prepaid clinical and pre-clinical expenses		10,280		11,237
Tax-related receivables and prepaids		6,862		1,903
Prepaid insurance		3,352		3,717
Interest receivable		2,731		3,311
Prepaid commercial expenses		2,729		2,947
Prepaid research expenses		2,512		1,927
Other		8,181		6,821
Total other current assets	$	179,895	$	149,891

The following table summarizes the Company’s other non-current assets for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Manufacturing-related deposits and prepaids	$	74,204	$	97,409
Intangible assets, net		29,620		7,578
Restricted cash*		15,579		19,024
Strategic investments		6,527		31,321
Prepaid maintenance services		5,466		3,403
Prepaid clinical expenses		2,133		2,150
Other		3,242		2,084
Total other non-current assets	$	136,771	$	162,969

* The Company had approximately $15.6 million and $19.0 million in restricted cash included in other non-current assets on the Company's consolidated balance sheets as of December 31, 2023 and 2022, respectively. Restricted cash for both years relates to (i) letters of credit established under the Company's various property leases that serve as security for potential future default of lease payments, (ii) a letter of credit established under a certain commercial supply agreement and (iii) collateralized cash for the Company's credit cards. The restricted cash is unavailable for withdrawal or use for general obligations.

Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Balance at beginning of the period	$ 61,704	$ 53,815	$ 48,475
Increase related to current year tax positions	4,126	8,079	5,503
Increase related to prior year tax positions	0	0	0
Decrease related to prior year tax positions	(800)	(190)	(163)
Balance at end of the period	$ 65,030	$ 61,704	$ 53,815

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND RECENT ACCOUNTING PRONOUNCEMENTS (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Summary of Estimated Useful Lives of Property and Equipment

The Company generally depreciates the cost of its property and equipment using the straight-line method over the estimated useful lives of the respective assets, which are summarized as follows:


Asset Category		Useful lives
Lab and manufacturing equipment		5 years
Office equipment		5 years
Software and computer equipment		3 - 5 years
Furniture and fixtures		7 years
Leasehold improvements		Lesser of the useful life or the term of the respective lease
Land improvements		25 years
Land		Not depreciated
Building and improvements		30 years
Construction in progress		Not depreciated until put into service

Indebtedness - Summary of Debt Facilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Sep. 16, 2022	Nov. 14, 2017
Debt Instrument [Line Items]
Principal amount	$ 1,314,935
Net carrying value of the convertible notes	1,237,998	$ 1,544,292
Total fair value of debt facilities	1,317,109	2,073,528
2024 Convertible Notes [Member]
Debt Instrument [Line Items]
Principal amount	105,847	419,371		$ 570,000
Unamortized discount - debt issuance costs	(364)	(3,059)
Total fair value of debt facilities	144,833	765,046
2027 Convertible Notes [Member]
Debt Instrument [Line Items]
Principal amount	1,150,000	1,150,000	$ 1,150,000
Unamortized discount - debt issuance costs	(17,485)	(22,020)
Total fair value of debt facilities	$ 1,172,276	$ 1,308,482
2019 Term Loan [Member]
Debt Instrument [Line Items]
Principal amount			$ 550,000

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (SX 210.12-04(a))
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/exampleRef
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Reference 8: http://www.xbrl.org/2003/role/exampleRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1B
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 25: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

PROPERTY AND EQUIPMENT, NET (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Summarizes Components of Property and Equipment, Net

Property and equipment are recorded at historical cost, net of accumulated depreciation. The following table summarizes components of property and equipment, net, for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Lab and manufacturing equipment	$	108,101		$	91,806
Leasehold improvements		99,989			97,328
Construction in progress		91,089			23,587
Software and computer equipment		50,179			47,573
Building and improvements		48,063			47,942
Furniture and fixtures		9,339			9,313
Land		5,183			5,183
Land improvements		4,988			4,988
Office equipment		1,193			1,193
Property and equipment, gross		418,124			328,913
Less: accumulated depreciation		(190,970	)		(148,876	)
Property and equipment, net	$	227,154		$	180,037

Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2016	Sep. 30, 2014	Jun. 30, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of award		10 years
Share based compensation granted under plan vest period		4 years
Granted		1,186,399
Weighted-average grant date fair value per share of stock-based awards, granted to employees		$ 70.94	$ 48.82	$ 48.16
Stock-based compensation Grants		$ 26,300
Share-Based Compensation Arrangement by Share-Based Payment Award, Terms of Award		550,110 options relating to the Unvested Tranche became vested as they met the conditions for vesting as a result of the average closing price of the Company's common stock exceeding $128.65 and $105.74 during 20 consecutive trading days and the compound annual growth rate of the Company's common stock exceeding that of the Nasdaq Biotech Index by greater than 5%
Average closing price		$ 70.91
Stock-based compensation expense		$ 182,514	$ 233,018	$ 113,943
Weighted average period expected to recognize unrecognized stock based compensation expense		3 years
Unrecognized stock based compensation expense		$ 260,700
Options with Service conditions [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock based compensation expense		110,300
Stock Units with Service Conditions [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock based compensation expense		143,800
Restricted Stock Units With Certain Peformance Conditions [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock based compensation expense		$ 6,600
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compound annual growth rate		5.00%	5.00%
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation granted under plan vest period		4 years
Stock-based compensation expense		$ 79,472	$ 174,868	$ 68,995
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation granted under plan vest period		1 year 2 months 12 days
Granted		38,500
Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount		$ 48,500
Stock options granted		502,225
Stock-based compensation Grants		$ 3,300
Weighted Average Grant Date Fair Value			$ 85.39	$ 85.32
Fair Value of RSUs		82,600	$ 33,100	$ 23,100
CEO [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted	3,300,000
Incremental compensation cost		$ 123,300
2013 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares approved under the plan					300,000			500,000		300,000		300,000
Common stock remain available for future grant		300,000
Term of award		24 months
Percentage of closing price of common stock		85.00%
2013 Employee Stock Purchase Plan [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation award, expiration date		Aug. 31, 2025
2013 Employee Stock Purchase Plan [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation award, expiration date		Feb. 29, 2024
2014 Employment Commencement Incentive Plan (2014 Plan) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares approved under the plan											600,000
Common stock remain available for future grant		600,000
Common stock increase in available for future grant shares		7,000,000
2018 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares approved under the plan					2,500,000	2,500,000	3,800,000		2,900,000
Common stock remain available for future grant		5,100,000
Share based compensation award tranche one [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting, Stock options		550,110	550,110
Average closing price		$ 128.65	$ 105.74
Share based compensation award tranche one [Member] \| CEO [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense		$ 13,400	$ 109,900

ACCRUED EXPENSES

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

ACCRUED EXPENSES

12. ACCRUED EXPENSES

The following table summarizes the Company’s accrued expenses for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Product revenue related reserves	$	100,075	$	68,784
Accrued employee compensation costs		78,732		65,946
Accrued clinical and pre-clinical costs		34,669		28,884
Accrued contract manufacturing costs		33,024		202,173
Accrued professional fees		17,187		12,061
Accrued income taxes		13,766		12,521
Accrued royalties		12,070		8,636
Accrued milestone and license expense		11,375		7,702
Accrued interest expense		4,395		4,956
Accrued collaboration cost-sharing		1,076		2,019
Other		8,628		5,314
Total accrued expenses	$	314,997	$	418,996

COMMITMENTS AND CONTINGENCIES

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

21. COMMITMENTS AND CONTINGENCIES

Manufacturing Obligations

The Company has entered into long-term contractual arrangements from time to time for the provision of goods and services.

Thermo Fisher Scientific, Inc.

The Company entered into a development, commercial manufacturing, and supply agreement in June 2018 and, subsequently, entered into the first and second amendments in May 2019 and July 2020, respectively, with Thermo, formerly Brammer Bio MA, LLC (collectively, the “Thermo Agreements”). Pursuant to the terms of the Thermo Agreements, the Company had

access to substantially all of the facility’s eight clean room suites for the Company’s gene therapy programs, subject to certain minimum and maximum volume limitations. The Company determined that the Thermo Agreements contained a lease because the Company had the right to direct the use of the facility and related equipment therein. The lease on four of the eight dedicated clean room suites at Thermo commenced during 2020 and the remaining four commenced during 2021, which is when the dedicated clean room suites became available for use by the Company.

In October 2021, the Company executed a third amendment (the “Third Amendment”) that modified the terms of the Thermo Agreements, which significantly decreased the Company’s right of use of the facility’s capacity and reduced the fixed and in-substance fixed payments due over the remaining term of the agreement. The modification was accounted for as a lease termination, resulting in: (i) the derecognition of ROU assets of $23.4 million and lease liabilities of $20.1 million, (ii) the recognition of $24.4 million research and development expense, inclusive of a loss of $3.3 million due to the lease termination and $21.1 million of accelerated amortization of nonrefundable advance payments made to Thermo that were previously recorded as other assets in the accompanying consolidated balance sheets for the year ended December 31, 2021.

Under the Third Amendment, the Thermo Agreements will expire on December 31, 2028, or earlier if certain conditions are met. The Company has the ability to extend the term with an 18-months’ notice and an agreement between the two parties. The Company also has the ability to terminate the Thermo Agreements prior to expiration, subject to the payment of additional financial consideration. Further, the Company has committed to guaranteed purchases under the Third Amendment on a take-or-pay basis regardless of whether services or goods are ordered. During the year ended December 31, 2022, the Company did not satisfy the total guaranteed purchase requirements in the fiscal year 2022 and, as a result, recognized a loss of approximately $54.0 million, which was classified as research and development expense in the accompanying consolidated statement of operations and comprehensive loss for the year ended December 31, 2022, with the outstanding liability reflected as accrued contract manufacturing costs within accrued expenses in the consolidated balance sheets as of December 31, 2022. No similar losses were incurred in 2023 or 2021.

In March 2023, the Company executed a fourth amendment (the “Fourth Amendment”) that modified the terms of the Thermo Agreements. The Fourth Amendment removed the previous minimum batch purchase commitment of $54.7 million per annum and associated fee for the remaining term of the Thermo Agreements. In connection with the elimination of such commitment and fee, the Amendment implemented a fee of up to $60.0 million, to be paid in three installments of $20.0 million each by March 1, 2024, December 31, 2024 and December 31, 2025, respectively, unless waived in part as described below. The Company will recognize the first $20.0 million installment due March 1, 2024 as a nonrefundable advance payment over the term of the agreement as the Company believes it will receive future benefit from this contract. As the Company has yet to obtain regulatory approval to produce commercial supply of ELEVIDYS at Thermo manufacturing facilities as of December 31, 2023, it recognized approximately $2.6 million as research and development expense during the year ended December 31, 2023 related to this nonrefundable advanced payment.

The second and third payment installments, which are associated with the years ending December 31, 2024 and 2025, will be waived if the Company meets certain minimum purchase thresholds under the Fourth Amendment. As of December 31, 2023, the Company believes it is probable that the minimum purchase thresholds will be met in the normal course of business throughout the term of the agreement and, therefore, no liabilities were recorded related to the second or third payment installments.

Catalent, Inc.

The Company entered into a manufacturing collaboration agreement and, subsequently, entered into a manufacturing and supply agreement with Catalent, formerly Paragon Biosciences, Inc. in October 2018 and February 2019, respectively (collectively, the “Catalent Agreements”). Pursuant to the terms of the Catalent Agreements, Catalent agreed to provide the Company with two dedicated clean room suites and an option to reserve two additional clean room suites for its gene therapy programs, subject to certain minimum and maximum volume limitations. In September 2019, the Company exercised the option to gain access to the two additional clean room suites. The Catalent Agreements will expire on December 31, 2024. The Company has the ability to terminate the Catalent Agreements prior to expiration, subject to the payment of additional financial consideration. The Company determined that the Catalent Agreements contained a lease because the Company had the right to direct the use of the facility and related equipment therein. The lease on all four dedicated clean room suites at Catalent commenced during 2020, which is when the dedicated clean room suites became available for use by the Company.

In March 2021, the Company modified the terms of the Catalent Agreements. The modification decreased the Company’s right of use of certain dedicated clean room suites and reduced the fixed and in-substance fixed payments due over the remaining term of the agreement. The modification was accounted for as a partial lease termination, resulting in the derecognition of ROU assets of $22.8 million and lease liabilities of $20.0 million and the recognition of a loss of $2.8 million, which was included in research and development expense for the year ended December 31, 2021.

In November 2022, the Company further modified certain terms of the Catalent Agreements which extended the term of the agreement through December 31, 2028, which represents a modification of the existing embedded lease over certain clean room suites. The modification resulted in the recognition of additional ROU assets and lease liabilities of $19.2 million, as well as reclassification of $3.9 million between long-term and short-term manufacturing deposits. The modification also removed certain fixed payments due over the remaining term of the agreement. Further, in order to maintain the Company's dedicated clean room suites, it has committed to guaranteed purchases under the Amendment on a take-or-pay basis regardless of whether services or goods are ordered. As of December 31, 2023, the Company believes it is probable that the guaranteed purchase requirements will be met in the normal course of business throughout the term of the Catalent Agreements.

Aldevron, LLC

The Company entered into a clinical and commercial supply agreement in December 2018, as subsequently amended in June 2020, with Aldevron LLC (“Aldevron”) for the supply of plasmid DNA to fulfill its needs for gene therapy clinical trials and commercial supply (collectively, the “Aldevron Agreements”). Pursuant to the terms of the Aldevron Agreements, Aldevron agreed to reserve a certain amount of manufacturing capacity on a quarterly basis. In return, the Company is required to make advance payments to Aldevron related to the manufacturing capacity. The term of the Aldevron Agreements will expire on December 31, 2026. The Company has the option to extend the term of the Aldevron Agreements by one year if the Company delivers a written notice of its intention to extend to Aldevron no later than June 1, 2025. Both parties have the right to early terminate without additional penalty. The Company has determined that the Aldevron Agreements do not contain an embedded lease because it does not convey the right to control the use of Aldevron’s facility or related equipment therein.

The following table presents non-cancelable contractual obligations arising from long-term contractual arrangements, including obligations related to leases embedded in certain supply agreements:


	As of December 31, 2023
	(in thousands)
2024	$	1,032,159
2025		150,767
2026		106,984
2027		77,640
2028		72,280
Thereafter		—
Total manufacturing commitments	$	1,439,830

Other Funding Commitments

The Company has several on-going clinical trials in various clinical trial stages. Its most significant clinical trial expenditures are to contract research organizations (“CROs”). The CRO contracts are generally cancellable at the Company’s option. As of December 31, 2023, the Company has approximately $580.0 million in cancellable future commitments based on existing CRO contracts. For the years ended December 31, 2023, 2022 and 2021, the Company recognized approximately $112.2 million, $78.7 million and $47.9 million, respectively, for expenditures incurred by CROs.

Litigation

In the normal course of business, the Company from time to time is named as a party to various legal claims, actions and complaints, which have included and may include matters involving securities, employment, intellectual property, arising from the use of therapeutics utilizing its technology, or others. The Company records a loss contingency reserve for a legal proceeding when it considers the potential loss probable and it can reasonably estimate the amount of the loss or determine a probable range of loss. The Company provides disclosure when it considers a loss reasonably possible or when it determines that a loss in excess of a reserve is reasonably possible. The Company provides an estimate of such reasonably possible losses or an aggregate range of such reasonably possible losses, unless the Company believes that such an estimate cannot be made. The Company has not recorded any material accruals for loss contingencies, and in management's opinion, no material range of loss is estimable for the matters described below as of December 31, 2023.

On September 15, 2020, REGENXBIO INC. (“Regenx”) and the Trustees of the University of Pennsylvania (“U-Penn”) filed a lawsuit against the Company and Sarepta Therapeutics Three, LLC, in the U.S. District Court for the District of Delaware. The plaintiffs assert patent infringement of U.S. Patent No. 10,526,617 (“the ‘617 Patent”) under 35 U.S.C.§§ 271(a)-(c) based on Sarepta’s alleged direct or indirect manufacture and use of the patented cultured host cell technology allegedly used to make adeno-associated virus (“AAV”) gene therapy products, including SRP-9001 (approved June 22, 2023 in the U.S. as ELEVIDYS®). Specifically, the Complaint essentially includes the allegation that Sarepta’s use, and the use by its contract manufacturers on its behalf, of a host cell containing a recombinant acid molecule that encodes a capsid protein having at least 95% amino acid identity to AAVrh10 infringes the ‘617 Patent asserted by Regenx. Plaintiffs seek injunctive relief, a judgment of infringement and willful infringement, damages that are no less than a reasonable royalty (treble damages), attorneys’ fees and costs, and such other relief as the court deems just and proper. On January 5, 2024, the Court granted Sarepta’s motion for summary judgment on the grounds that the asserted claims of Regenx’s ‘617 Patent are invalid because they cover patent-ineligible subject matter under 35 U.S.C. § 101. On January 12, 2024, the Court entered judgment and closed the case and Plaintiffs filed a notice of appeal to the U.S. Court of Appeals for the Federal Circuit.

On June 20, 2023, Regenx and U-Penn commenced a second patent infringement lawsuit against Sarepta and its contract manufacturer, Catalent asserting patent alleged infringement of U. S. Patent No. 11,680,274 (“the ’274 Patent”). In the second lawsuit, Regenx and U-Penn allege that Sarepta and Catalent’s manufacture, use and commercial launch of ELEVIDYS® (formerly/also known as SRP-9001) infringe the ’274 Patent. Sarepta answered the complaint on August 10, 2023, and a case schedule has been set

with a trial commencing on November 17, 2025. On February 21, 2024, Sarepta submitted a petition for Inter Partes Review for filing with the Patent Trial and Appeal Board at the USPTO. The petition seeks to invalidate the ‘274 Patent.

On July 13, 2021, Nippon Shinyaku Co., Ltd. (“Nippon Shinyaku” or “NS”) filed a lawsuit against the Company in the U.S. District Court for the District of Delaware. NS asserts a claim for breach of contract arising from Sarepta filing seven petitions for Inter Partes Review (“IPR Petitions”) with the Patent Trial and Appeal Board at the USPTO in which Sarepta sought to invalidate certain NS patents concerning exon 53 skipping technology (U.S. Patent Nos. 9,708,361, 10,385,092, 10,407,461, 10,487,106, 10,647,741, 10,662,217, and 10,683,322, respectively, and collectively the “NS Patents”). In addition, NS asserts claims for patent infringement and willful infringement of each of the NS Patents allegedly arising from Sarepta’s activities, including the sale of, its exon 53 skipping product, VYONDYS 53 (golodirsen). NS further seeks a determination of non-infringement by NS alleged to arise from NS’s activities, including the sale of, its exon 53 skipping product, Viltepso (viltolarsen) and invalidity of certain patents licensed to the Company from UWA (U.S. Patent Nos. 9,994,851, 10,227,590, and 10,266,827, collectively the “UWA Patents”). In its complaint, NS is seeking legal fees and costs, an unspecified amount of monetary relief (treble damages) attributed to Sarepta’s alleged infringement, and such other relief as the court deems just and proper. In January 2022, the PTAB granted institution of all claims of all NS Patents in response to Sarepta’s IPR Petitions and determined that Sarepta has demonstrated a reasonable likelihood of success in proving that the NS Patents are unpatentable. NS filed a motion for preliminary injunction solely seeking Sarepta’s withdrawal of the IPR Petitions, which was ultimately granted after the U.S. Court of Appeals for the Federal Circuit reversed and remanded to the district court on February 8, 2022. Sarepta subsequently withdrew the IPRs, which were terminated on June 14, 2022. On December 27, 2021, the district court partially granted and denied the motion to dismiss by Sarepta and ordered NS to file a Second Amended Complaint (“SAC”), which it did on January 14, 2022. In the SAC, NS maintains all claims of the original complaint of July 13, 2021, except a determination of non-infringement of the UWA Patents. On January 28, 2022, Sarepta filed its answer to the SAC, with defenses and counterclaims against NS and NS Pharma Inc. that include infringement of the UWA Patents allegedly arising from their activities concerning, including the sale of, its exon 53 skipping product, Viltepso (viltolarsen) and breach of contract. Sarepta is also seeking a determination of invalidity of the NS Patents. In its counterclaim complaint, Sarepta is seeking an award of relief in its defenses to NS’ allegations, a judgment of breach of contract, a determination of invalidity of the NS Patents, a judgment of infringement and willful infringement of the UWA Patents, legal fees and costs, an unspecified amount of monetary relief (treble damages) attributable to NS’ alleged infringement, and such other relief as the court deems just and proper. UWA has since been joined as a Plaintiff in Sarepta’s counterclaims against NS. On August 14, 2023, the Court granted cross motions to amend the pleadings, allowing Sarepta to add a counterclaim against NS for inequitable conduct, and NS to add counterclaims against Sarepta for inequitable conduct and Walker Process fraud. The parties have since stipulated to the dismissal of certain claims and defenses, including (1) NS’s claims of infringement of the ’361 Patent and claims 5 and 10 of the ’322 Patent; and (2) Sarepta’s non-infringement defenses to the remainder of the asserted NS Patents, except to the non-withdrawn claims of the ‘322 patent. Briefing on the parties’ summary judgment and Daubert motions was completed on January 26, 2024. A trial is scheduled to commence on May 13, 2024.

On or about June 5, 2023, Sarepta initiated a patent infringement lawsuit against Nippon Shinyaku in Japan, alleging that NS’s production, sales and offers to sell Viltepso infringe Sarepta’s Japanese Patent No. 6406782. NS filed its preliminary answer on July 13, 2023. Thereafter, the Court set an initial case schedule, with a final hearing set for July 11, 2024.

Stock Based Compensation - Summary of Employee Stock Purchase Plan Activity and Expense (Detail) - 2013 Employee Stock Purchase Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares purchased	153,027	115,124	111,171
Proceeds received (in millions)	$ 10.8	$ 7.5	$ 7.8

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-Subparagraph (a)(3)
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Other Assets - Summary of Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Prepaid Expense and Other Assets, Current [Abstract]
Manufacturing-related deposits and prepaids	$ 102,181	$ 66,455
Collaboration and other receivable	29,786	41,758
Prepaid maintenance services	11,281	9,815
Prepaid clinical and pre-clinical expenses	10,280	11,237
Tax-related receivables and prepaids	6,862	1,903
Prepaid insurance	3,352	3,717
Interest receivable	2,731	3,311
Prepaid commercial expenses	2,729	2,947
Prepaid research expenses	2,512	1,927
Other	8,181	6,821
Total other current assets	$ 179,895	$ 149,891

OTHER (LOSS) INCOME, NET

12 Months Ended

Dec. 31, 2023

Other Income and Expenses [Abstract]

OTHER (LOSS) INCOME, NET

17. OTHER (LOSS) INCOME, NET

The following table summarizes other (loss) income, net for the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands)
Interest expense	$	(22,010	)	$	(53,248	)	$	(63,525	)
Interest income		36,257			16,488			354
Accretion of investment discount, net		49,712			11,235			157
(Loss) gain on contingent consideration, net*		(1,200	)		6,700			7,200
Impairment of strategic investments		(30,321	)		(2,575	)		(4,488	)
Other, net		617			(6,921	)		(936	)
Other income (expense), net	$	33,055		$	(28,321	)	$	(61,238	)
Loss on debt extinguishment		(387,329	)		(125,441	)		—
Gain from sale of Priority Review Voucher		102,000			—			102,000
Total other (loss) income, net	$	(252,274	)	$	(153,762	)	$	40,762

* The (loss) gain on contingent consideration, net is related to the fair value adjustment of the regulatory-related contingent payments that are accounted for as derivatives. Please see Note 5. Fair Value Measurements for further details.

Indebtedness - Additional Information (Detail) $ / shares in Units, shares in Millions							12 Months Ended
	Mar. 02, 2023 USD ($) shares	Sep. 19, 2022 USD ($)	Sep. 16, 2022 USD ($) Days Milestone $ / shares	Sep. 14, 2022 USD ($)	Jan. 01, 2021 USD ($)	Nov. 14, 2017 USD ($) Days Milestone $ / shares	Dec. 31, 2023 USD ($) shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($) shares
Debt Instrument [Line Items]
Debt instrument, face amount							$ 1,314,935,000
Additional loan consideration and premiums							0	$ 25,364,000	$ 0
Debt conversion costs for 2024 Notes	$ 6,900,000						6,887,000	0	0
Partial settlement of capped call							80,645,000	26,317,000	0
Loss on debt extinguishment							(387,329,000)	(125,441,000)	0
Issuance of common stock for exchange of 2024 Notes, value							693,377,000
Long-term debt							1,132,515,000	1,544,292,000
Interest expense related to debt facilities							22,000,000	53,200,000	63,500,000
Amortization of Debt Issuance Costs							5,200,000	7,500,000	$ 7,600,000
Increase in convertible notes					$ 96,800,000
Decrease in accumulated deficit					(60,200,000)
Decrease in additional paid-in-capital					$ (157,000,000)
Aggregate long-term debt							1,237,998,000	1,544,292,000
Convertible Debt, The Term Loan, The Revolver and The Mortgage Loans [Member]
Debt Instrument [Line Items]
Long-term debt							1,132,500,000	1,544,300,000
Long-term debt, current portion							105,500
2024 Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 570,000,000	$ 105,847,000	$ 419,371,000
Fair value convertible note exchange	693,400,000
Debt conversion costs for 2024 Notes	6,900,000
Conversion of shares excluded from computation of diluted EPS \| shares							1.4	5.7	7.8
Loss on debt extinguishment	$ 387,300,000
Debt instrument, maturity date						Nov. 15, 2024
Issuance of common stock for exchange of 2024 Notes, shares \| shares	4.5
Debt instrument, interest rate per annum						1.50%
Net proceeds from convertible note issuance						$ 559,400,000
Debt instrument, convertible into shares \| Milestone						7,763,970
Debt instrument, conversion rate						0.013621
Debt convertible notes per principal amount						$ 1,000
Debt instrument, conversion price \| $ / shares						$ 73.42
Reduction in carrying value of convertible notes	$ 311,500,000
Eliminated accrued interest	1,500,000
Debt Instrument, Convertible, Terms of Conversion Feature						The holders of the 2024 Notes may convert their 2024 Notes at their option only in the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2017, if the last reported sale price per share of common stock exceeds 130% of the conversion price for each of at least 20 trading days during the 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; (2) during the five consecutive business days immediately after any five consecutive trading day period (the “measurement period”) in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company's common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company's common stock, as described in the indenture agreement; and (4) at any time from, and including, May 15, 2024 until the close of business on the scheduled trading day immediately before the maturity date.
Debt Instrument Redemption Price, Percentage of Principal Amount Redeemed						100.00%
Debt issuance costs						$ 10,600,000
Effective interest rate percentage						1.90%
Debt issuance costs							$ 364,000	$ 3,059,000
2024 Convertible Notes [Member] \| Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 1,000
Debt Instrument, Periodic Payment, Principal	313,500,000
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger						130.00%
Debt Instrument, Convertible, Threshold Trading Days \| Days						20
Debt Instrument, Convertible, Threshold Consecutive Trading Days \| Days						30
2027 Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 1,150,000,000				$ 1,150,000,000	$ 1,150,000,000
Conversion of shares excluded from computation of diluted EPS \| shares							8.1	8.1	8.1
Debt instrument, maturity date			Sep. 15, 2027
Debt instrument, interest rate per annum			1.25%
Debt instrument, payment frequency			semi-annually
Net proceeds from convertible note issuance			$ 1,126,700,000
Debt Instrument, Convertible, Terms of Conversion Feature			The holders of the 2027 Notes may convert their 2027 Notes at their option only in the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2022, if the last reported sale price per share of common stock exceeds 130% of the conversion price for each of at least 20 trading days during the 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; (2) during the five consecutive business days immediately after any five consecutive trading day period (the “measurement period”) in which the trading price per $1,000 principal amount of 2027 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company's common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company's common stock, as described in the indenture agreement; (4) if the Company calls such notes for redemption; and (5) at any time from, and including, March 15, 2027 until the close of business on the second trading day immediately before the maturity date.
Debt issuance costs			$ 23,300,000
Effective interest rate percentage			1.67%
Debt issuance costs							$ 17,485,000	$ 22,020,000
2027 Convertible Notes [Member] \| Director [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 20,000,000
2027 Convertible Notes [Member] \| Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 1,000
Debt instrument, convertible into shares \| Milestone			8,100,485
Debt instrument, conversion rate			7.0439
Debt Instrument, Periodic Payment, Principal			$ 1,000
Debt instrument, conversion price \| $ / shares			$ 141.97
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger			130.00%
Debt Instrument, Convertible, Threshold Trading Days \| Days			20
Debt Instrument, Convertible, Threshold Consecutive Trading Days \| Days			30
2027 Convertible Notes [Member] \| Common Stock [Member] \| September 20, 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger			130.00%
Debt Instrument, Convertible, Threshold Trading Days \| Days			20
Debt Instrument, Convertible, Threshold Consecutive Trading Days \| Days			30
Debt Instrument Redemption Price, Percentage of Principal Amount Redeemed			100.00%
Capped Call Transactions [Member]
Debt Instrument [Line Items]
Capped calls strike price \| $ / shares			141.97
Capped calls cap price \| $ / shares			210.32
Amount paid for capped calls transactions			$ 127,300,000
Capped Call Transactions [Member] \| Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, convertible into shares \| Milestone			8,100,485
2017 Capped Call Transactions [Member]
Debt Instrument [Line Items]
Capped calls strike price \| $ / shares						73.42
Capped calls cap price \| $ / shares						104.88
Amount paid for capped calls transactions						$ 50,900,000
2017 Capped Call Transactions [Member] \| Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, convertible into shares \| Milestone						7,763,970
2024 Notes Repurchase [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 150,600,000
Payment for full settlement of the principal value and accrued interest				248,600,000
Reduction In Carrying Value Of Repurchase Of Notes				149,300,000
Accrued Interest				800,000
Loss on debt extinguishment				$ 98,500,000
2017 Capped Calls Partial Settlement [Member]
Debt Instrument [Line Items]
Partial settlement of capped call	$ 80,600,000	$ 26,300,000
2019 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 550,000,000
Additional loan consideration and premiums			25,400,000
Payoff Amount			585,500,000
Accrued Interest			$ 10,100,000
Loss on debt extinguishment								$ (26,900,000)

PROPERTY AND EQUIPMENT, NET

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT, NET

10. PROPERTY AND EQUIPMENT, NET

Property and equipment are recorded at historical cost, net of accumulated depreciation. The following table summarizes components of property and equipment, net, for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Lab and manufacturing equipment	$	108,101		$	91,806
Leasehold improvements		99,989			97,328
Construction in progress		91,089			23,587
Software and computer equipment		50,179			47,573
Building and improvements		48,063			47,942
Furniture and fixtures		9,339			9,313
Land		5,183			5,183
Land improvements		4,988			4,988
Office equipment		1,193			1,193
Property and equipment, gross		418,124			328,913
Less: accumulated depreciation		(190,970	)		(148,876	)
Property and equipment, net	$	227,154		$	180,037

For the years ended December 31, 2023, 2022 and 2021, depreciation expense totaled $42.5 million, $40.0 million, and $36.6 million, respectively.

Income Taxes - Summary of Loss before Provision (Benefit) for Income Taxes by Jurisdiction (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Domestic	$ (238,660)	$ (251,384)	$ (47,633)
Foreign	(281,438)	(438,579)	(371,315)
Total	$ (520,098)	$ (689,963)	$ (418,948)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(11))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479557/942-235-S99-1

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-SubTopic 20
-Topic 940
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481913/940-20-25-1

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Summary of Loss before Provision (Benefit) for Income Taxes by Jurisdiction

The following table summarizes the loss before the provision (benefit) for income taxes by jurisdiction for the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands)
Domestic	$	(238,660	)	$	(251,384	)	$	(47,633	)
Foreign		(281,438	)		(438,579	)		(371,315	)
Total	$	(520,098	)	$	(689,963	)	$	(418,948	)

Summary of Provision (Benefit) for Income Taxes

The following table summarizes provision (benefit) for income taxes in the accompanying consolidated financial statements for the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands)
Current provision:
Federal	$	4,180		$	—		$	—
State		11,111			13,193			(40	)
Foreign		753			944			181
Total current provision		16,044			14,137			141
Deferred benefit:
Federal		—			—			—
State		—			—			—
Foreign		(165	)		(612	)		(309	)
Total deferred benefit		(165	)		(612	)		(309	)
Total income tax expense (benefit)	$	15,879		$	13,525		$	(168	)

Summary of Reconciliation Between Effective Tax Rate and Statutory Income Tax Rate

The following table summarizes the reconciliation between the Company’s effective tax rate and the statutory income tax rate for each of the periods indicated:


	For the Year Ended December 31,
	2023				2022				2021
Federal income tax rate		21.0		%		21.0		%		21.0		%
State taxes		(7.7	)			4.1				0.4
Research and development tax credits		28.3				6.9				10.0
Valuation allowance		(13.7	)			(14.7	)			(9.8	)
Permanent differences		(0.2	)			(1.1	)			(0.3	)
Stock-based compensation		(2.0	)			(1.5	)			(3.4	)
Excess benefit stock deductions		1.6				0.3				0.4
Foreign rate differential		(11.3	)			(13.2	)			(18.4	)
Non-deductible repurchase premium		—				(2.2	)			—
Non-deductible premium on note conversion		(15.3	)			—				—
Other		(3.8	)			(1.6	)			0.1
Effective tax rate		(3.1	)	%		(2.0	)	%		(0.0	)	%

Summary of Analysis of Deferred Tax Assets and Liabilities

The following table summarizes the deferred tax assets and liabilities for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	154,948		$	241,826
Difference in depreciation and amortization		36,611			39,725
Research and development tax credits		374,017			261,067
Stock-based compensation		94,452			80,193
Lease liabilities		33,792			11,782
Capitalized inventory		35,269			33,366
Debt discount		25,597			35,975
Capitalized research and development costs		106,534			74,886
Other		50,308			44,022
Total deferred tax assets		911,528			822,842
Deferred tax liabilities:
Right of use asset		(25,800	)		(9,174	)
Debt discount		—			—
Total deferred tax liabilities		(25,800	)		(9,174	)
Valuation allowance		(883,665	)		(811,908	)
Net deferred tax assets	$	2,063		$	1,760

Summary of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits

The following table summarizes the reconciliation of the beginning and ending amount of total unrecognized tax benefits for each of the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands)
Balance at beginning of the period	$	61,704		$	53,815		$	48,475
Increase related to current year tax positions		4,126			8,079			5,503
Increase related to prior year tax positions		—			—			—
Decrease related to prior year tax positions		(800	)		(190	)		(163	)
Balance at end of the period	$	65,030		$	61,704		$	53,815

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (535,977)	$ (703,488)	$ (418,780)
Adjustments to reconcile net loss to cash flows in operating activities:
Loss on debt extinguishment	387,329	125,441	0
Gain from sale of Priority Review Voucher	(102,000)	0	(102,000)
Depreciation and amortization	44,397	41,864	38,017
Reduction in the carry amounts of the right of use assets	14,495	12,735	11,325
Non-cash interest expense	5,156	7,552	7,581
Stock-based compensation	182,514	233,018	113,943
Accretion of investment discount, net	(46,176)	(10,651)	(102)
Impairment of strategic investments	30,321	2,575	4,488
Other	37	5,078	522
Changes in operating assets and liabilities, net:
Net increase in accounts receivable	(185,699)	(61,638)	(51,650)
Net increase in inventory	(147,714)	(50,780)	(83,772)
Net (increase) decrease in other assets	(10,713)	14,620	103,203
Net decrease in deferred revenue	(86,828)	(89,244)	(89,244)
Net (decrease) increase in accounts payable, accrued expenses, lease liabilities and other liabilities	(50,135)	147,572	23,297
Net cash used in operating activities	(500,993)	(325,346)	(443,172)
Cash flows from investing activities:
Proceeds from sale of Priority Review Voucher	102,000	0	102,000
Purchase of property and equipment	(76,106)	(30,824)	(38,490)
Purchase of available-for-sale securities	(2,044,940)	(1,936,856)	(29,988)
Maturity and sale of available-for-sale securities	1,868,482	923,224	466,000
Purchase of intangible assets	(11,239)	(1,427)	(2,309)
Acquisition of strategic investments	(4,000)	(1,000)	(1,800)
Net cash (used in) provided by investing activities	(165,803)	(1,046,883)	495,413
Cash flows from financing activities:
Partial settlement of capped call share options for 2024 Notes	80,645	26,317	0
Proceeds from exercise of stock options and purchase of stock under the Employee Stock Purchase Program	51,246	30,043	20,802
Debt conversion costs for 2024 Notes	(6,887)	0	0
Proceeds from 2027 Notes offering, net of commissions	0	1,127,400	0
Debt issuance costs for 2027 Notes	0	(716)	0
Purchase of capped call share options for 2027 Notes	0	(127,305)	0
Repurchase of 2024 Notes	0	(247,868)	0
Repayment of principal amount due under 2019 Term Loan	0	(550,000)	0
Payment on debt extinguishment of 2019 Term Loan	0	(25,364)	0
Taxes paid related to net share settlement of equity awards	0	0	(7,765)
Proceeds from sales of common stock, net of offering costs	0	0	548,532
Net cash provided by financing activities	125,004	232,507	561,569
(Decrease) increase in cash and cash equivalents	(541,792)	(1,139,722)	613,810
Cash, cash equivalents and restricted cash:
Beginning of year	985,801	2,125,523	1,511,713
End of year	444,009	985,801	2,125,523
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	428,430	966,777	2,115,869
Restricted cash in other assets	15,579	19,024	9,654
Total cash, cash equivalents and restricted cash	444,009	985,801	2,125,523
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	15,923	44,418	55,949
Cash paid during the period for income taxes	15,081	1,695	583
Supplemental schedule of non-cash activities:
Lease liabilities arising from obtaining right of use assets	80,203	40,006	13,225
Intangible assets and property and equipment included in accounts payable and accrued expenses	33,339	6,765	4,162
Lease liabilities terminated	$ 0	$ 3,807	$ 40,133

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect of Accounting Change [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Cumulative Effect of Accounting Change [Member]	Accumulated Other Comprehensive Gain (Loss) [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Cumulative Effect of Accounting Change [Member]
Balance at Dec. 31, 2020	$ 761,759	$ (96,792)	$ 8	$ 3,609,877	$ (156,953)	$ 3	$ (2,848,129)	$ 60,161
Balance (in shares) at Dec. 31, 2020			79,374
Exercise of options for common stock	12,963			12,963
Exercise of options for common stock, shares			283
Vest of restricted stock units/awards			277
Shares withheld for taxes	(1,432)			(1,432)
Shares withheld for taxes, shares			(18)
Issuance of common stock for cash, net of offering costs	548,532		$ 1	548,531
Issuance of common stock for cash, net of offering costs, shares			7,099
Issuance of common stock under employee stock purchase plan	7,839			7,839
Issuance of common stock under employee stock purchase plan, shares			112
Stock-based compensation	113,943			113,943
Purchase of capped call share options for 2027 Notes	0
Partial settlement of capped call share options for 2024 Notes	0
Unrealized losses from available-for-sale securities, net of tax	(23)					(23)
Net loss	(418,780)						(418,780)
Balance at Dec. 31, 2021	928,009		$ 9	4,134,768		(20)	(3,206,748)
Balance (in shares) at Dec. 31, 2021			87,127
Exercise of options for common stock	22,573			22,573
Exercise of options for common stock, shares			318
Vest of restricted stock units/awards			389
Issuance of common stock under employee stock purchase plan	7,470			7,470
Issuance of common stock under employee stock purchase plan, shares			116
Stock-based compensation	233,018			233,018
Purchase of capped call share options for 2027 Notes	(127,305)			(127,305)
Partial settlement of capped call share options for 2024 Notes	26,317			26,317
Unrealized losses from available-for-sale securities, net of tax	(1,644)					(1,644)
Net loss	(703,488)						(703,488)
Balance at Dec. 31, 2022	384,950		$ 9	4,296,841		(1,664)	(3,910,236)
Balance (in shares) at Dec. 31, 2022			87,950
Exercise of options for common stock	$ 40,485			40,485
Exercise of options for common stock, shares	528,909		528
Vest of restricted stock units/awards			645
Issuance of common stock for exchange of 2024 Notes, shares			4,456
Issuance of common stock for exchange of 2024 Notes, value	$ 693,377			693,377
Issuance of common stock under employee stock purchase plan	10,761			10,761
Issuance of common stock under employee stock purchase plan, shares			153
Stock-based compensation	182,514			182,514
Purchase of capped call share options for 2027 Notes	0
Partial settlement of capped call share options for 2024 Notes	80,645			80,645
Unrealized losses from available-for-sale securities, net of tax	2,582					2,582
Net loss	(535,977)						(535,977)
Balance at Dec. 31, 2023	$ 859,337		$ 9	$ 5,304,623		$ 918	$ (4,446,213)
Balance (in shares) at Dec. 31, 2023			93,732

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Impairment of investment in private companies	$ 30,321	$ 2,575	$ 4,488
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	1,200	(6,700)
Strategic investments	6,527	31,321
Series A Preferred Stock [Member] \| Lacerta Therapeutics Inc [Member]
Schedule of Equity Method Investments [Line Items]
Impairment of investment in private companies	30,000
Fair Value, Inputs, Level 3 [Member]
Schedule of Equity Method Investments [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	2,000	$ (6,700)
Biotechnology Company[ Member]
Schedule of Equity Method Investments [Line Items]
Strategic investments	5,500
Other Noncurrent Assets [Member]
Schedule of Equity Method Investments [Line Items]
Strategic investments	$ 5,500

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	3,333,333	3,333,333
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	198,000,000	198,000,000
Common stock,shares issued	93,731,831	87,950,117
Common stock,shares outstanding	93,731,831	87,950,117

PRODUCT REVENUES, NET, ACCOUNTS RECEIVABLE,NET AND RESERVES FOR PRODUCT REVENUES

12 Months Ended

Dec. 31, 2023

Receivables, Net, Current [Abstract]

PRODUCT REVENUES, NET, ACCOUNTS RECEIVABLE AND RESERVES FOR PRODUCT REVENUES

7. PRODUCT REVENUES, NET, ACCOUNTS RECEIVABLE, NET AND RESERVES FOR PRODUCT REVENUES

Net product revenues, which includes revenues associated with EXONDYS 51, AMONDYS 45 and VYONDYS 53 (collectively, the “PMO Products”) and ELEVIDYS consisted of the following:


	For the Year Ended December 31,
	2023		2022
	(in thousands)
PMO Products
United States	$	797,944	$	747,101
Rest of World		146,576		96,668
Total PMO product revenues, net	$	944,520	$	843,769
ELEVIDYS
United States		200,356		—
Total ELEVIDYS product revenues, net	$	200,356	$	—
Total product revenues, net	$	1,144,876	$	843,769

Net product revenues within the U.S. exceeded 90% of total net product revenues for the year ended December 31, 2021. No individual country outside the U.S. exceeded 10% of total net product revenues for any of the years ended December 31, 2023, 2022 and 2021.

The following table summarizes the Company's net product revenues, by customer, for those customers that exceeded 10% for the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
Product revenues, net
Customer 1		41	%		48	%		48	%
Customer 2		26	%		33	%		39	%
Customer 3	*			*				10	%

* Customer did not exceed 10% of the Company's net product revenues within the applicable year.

As of December 31, 2023 and December 31, 2022, the Company's accounts receivable, net were $400.3 million and $214.6 million, respectively, which related to product sales receivable, net of discounts and allowances. As of December 31, 2023, the Company believes its largest customers are of high credit quality and has not experienced any material credit losses related to such customers. Please refer to Note 2, Summary of Significant Accounting Policies and Recent Accounting Pronouncements for discussion of the credit risk associated with accounts receivable, net.

The following table summarizes an analysis of the change in reserves for discounts and allowances for the periods indicated:


	Chargebacks			Rebates			Prompt Pay			Other Accruals			Total
	(in thousands)
Balance, as of December 31, 2021	$	799		$	60,506		$	2,798		$	6,363		$	70,466
Provision		12,446			108,514			12,904			47,654			181,518
Adjustments relating to prior year		—			(5,679	)		—			30			(5,649	)
Payments/credits		(12,828	)		(95,848	)		(12,359	)		(30,602	)		(151,637	)
Balance, as of December 31, 2022	$	417		$	67,493		$	3,343		$	23,445		$	94,698
Provision		44,191			129,724			15,067			69,664			258,646
Adjustments relating to prior year		536			(5,103	)		—			—			(4,567	)
Payments/credits		(17,658	)		(93,920	)		(14,579	)		(57,848	)		(184,005	)
Balance, as of December 31, 2023	$	27,486		$	98,194		$	3,831		$	35,261		$	164,772

The following table summarizes the total reserves above included in the Company’s consolidated balance sheets for the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Reduction to accounts receivable, net	$	64,697	$	25,914
Component of accrued expenses		100,075		68,784
Total reserves	$	164,772	$	94,698

STOCK-BASED COMPENSATION

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION

15. STOCK-BASED COMPENSATION

In June 2013, the Company’s stockholders approved the 2013 Employee Stock Purchase Plan (the “2013 ESPP”) which authorized 0.3 million shares of common stock available to be issued. In June 2016, 2019 and 2023, the Company’s stockholders approved an additional 0.3 million, 0.5 million and 0.3 million shares, respectively, of common stock available for issuance under the 2013 ESPP. As of December 31, 2023, 0.3 million shares of common stock remain available for future grant under the 2013 ESPP.

In September 2014, the Company initiated the 2014 Employment Commencement Incentive Plan (the “2014 Plan”). The 2014 Plan, which authorized 0.6 million shares of common stock to be issued and allows for the grant of stock options, stock appreciation rights (“SARs”), restricted stock awards (“RSAs”), RSUs, performance shares and performance units. As of December 31, 2023, 7.0 million shares have been added to the Company's 2014 Plan. As of December 31, 2023, 0.6 million shares of common stock remain available for future grant under the 2014 Plan.

In June 2018, the Company’s stockholders approved the 2018 Equity Incentive Plan (the “2018 Plan”). The 2018 Plan, which authorized 2.9 million shares of common stock to be issued, allows for the grant of stock options, SARs, RSAs, RSUs, performance shares and performance units. In June 2020, June 2022 and June 2023, an additional 3.8 million, 2.5 million and 2.5 million shares of common stock, respectively, were approved by the Company’s stockholders and added to the 2018 Plan. As of December 31, 2023, together with the roll-over shares from the Company’s 2011 Equity Incentive Plan, 5.1 million shares of common stock remain available for future grant under the 2018 Plan.

Stock Options

In general, stock options have a ten-year term and vest over a four-year period, with one-fourth of the underlying shares vesting on the first anniversary of the grant and 1/48th of the underlying shares vesting monthly thereafter, such that the underlying shares will be fully vested on the fourth anniversary of the grant, subject to the terms of the applicable plan under which they were granted.

The fair values of stock options granted during the periods presented are measured on the date of grant using the Black-Scholes-Merton option-pricing model, with the following assumptions:


	For the Year Ended December 31,
	2023	2022	2021
Risk-free interest rate (1)	3.5 - 4.9%	1.6 - 4.2%	0.4 - 1.3%
Expected dividend yield (2)	—	—	—
Expected term (3)	5.23 years	5.09 years	4.99 years
Expected volatility (4)	46.8 - 63.2%	52.4 - 72.9%	60.1 - 70.8%

(1)

The risk-free interest rate is estimated using an average of Treasury bill interest rates over a historical period commensurate with the expected term of the option that correlates to the prevailing interest rates at the time of grant.

(2)

The expected dividend yield is zero as the Company has not paid any dividends to date and does not expect to pay dividends in the future.

(3)

The expected term is estimated using historical exercise behavior.

(4)

The expected volatility is the implied volatility in exchange-traded options of the Company’s common stock.

The amounts estimated according to the Black-Scholes-Merton option-pricing model may not be indicative of the actual values realized upon the exercise of these options by the holders.

The following table summarizes the Company’s stock option activity for the period indicated:


	For the Year Ended December 31, 2023
				Weighted-Average
	Shares			Exercise Price
Grants outstanding at beginning of the period		9,130,140		$	70.04
Granted		1,186,399			147.71
Exercised		(528,909	)		76.68
Cancelled and forfeited		(204,935	)		103.74
Grants outstanding at end of the period		9,582,695		$	78.57

Grants exercisable at end of the period		5,951,953		$	70.91
Grants vested and expected to vest at end of the period		9,216,033		$	77.01

The weighted-average grant date fair value per share of stock options granted during the years ended December 31, 2023, 2022 and 2021 was $70.94, $48.82 and $48.16, respectively.


			Weighted-Average
	Aggregate		Remaining
	Intrinsic Value		Contractual
	(in thousands)		Life (Years)
Options outstanding at December 31, 2023	$	288,119		5.7
Options exercisable at December 31, 2023	$	202,405		4.9
Options vested and expected to vest at December 31, 2023	$	285,706		5.5

The following table summarizes the Company’s shares vested and stock options exercised for each of the periods indicated:


	For the Year Ended December 31,
	2023		2022		2021
	(in thousands)
Aggregate grant date fair value of shares vested	$	142,692	$	140,889	$	79,068
Aggregate intrinsic value of stock options exercised	$	29,711	$	12,150	$	10,622

Grant Modification

In June 2017, the Company granted its CEO 3,300,000 options with service and market conditions which were subject to a five-year cliff vesting schedule. On April 19, 2022 (the “Effective Date”), the Company entered into an agreement with its CEO to modify the vesting conditions of the options (the “Amendment”). Under the Amendment, one-third of the options vested (the “Vested Tranche”) on the Effective Date with no required service or market conditions. Subject to the CEO's continued service through each applicable vesting date and the compound annual growth rate of the Company's common stock exceeding that of the Nasdaq Biotech Index in varying percentages, the remaining two-thirds of the options (the “Unvested Tranche”) shall vest in varying increments at any time between the Effective Date and June 26, 2025 (the “Measurement Period”) when (and if) the average of the closing price of the Company’s common stock during any consecutive 20 trading day period during the Measurement Period reaches certain pre-determined target stock prices. Additionally, the CEO is subject to a one-year post-exercise restriction to sell, transfer or dispose shares acquired upon the exercise of any options that vest after deduction of any shares withheld or sold to pay the applicable aggregate exercise price and/or withholding taxes.

To determine the incremental compensation cost of the modification, the fair value of the modified awards was compared to the fair value of the original awards measured immediately before its terms or conditions were modified. As the Vested Tranche became immediately vested on the Effective Date, the post-modification fair value for the Vested Tranche is based on the Black-Scholes-Merton option-pricing model, while the pre-modification fair value is based on a lattice model with Monte Carlo simulations.

The Unvested Tranche represents awards with market conditions only. Both the pre- and post-modification fair values for the Unvested Tranche are determined by a lattice model with Monte Carlo simulations. The incremental compensation costs related to varying increments of the Unvested Tranche will be recognized as stock-based compensation expense over their respective derived service periods, an output from the Monte Carlo simulation, and were fully recognized over a 1.3-year period from the Effective Date. The aggregate incremental cost of the modification of the CEO's awards was $123.3 million.

During both the years ended December 31, 2023 and 2022, respectively, 550,110 options relating to the Unvested Tranche became vested as they met the conditions for vesting as a result of the average closing price of the Company's common stock exceeding $128.65 and $105.74 during 20 consecutive trading days and the compound annual growth rate of the Company's common stock exceeding that of the Nasdaq Biotech Index by greater than 5%. Accordingly, all previously unrecognized expense associated with these options was immediately recognized. For the years ended December 31, 2023 and 2022, the Company recorded $13.4 million and $109.9 million as stock-based compensation expense relating to the CEO’s awards, respectively. As of December 31, 2023, the Unvested Tranche was fully expensed.

Excluding the options with market and service conditions granted to the Company’s CEO, the remaining stock options granted during the periods presented in the table have only service-based criteria and vest over four years.

Restricted Stock Units

The Company grants RSUs to members of its board of directors and employees. The following table summarizes the Company’s RSU activity for the period indicated:


	For the Year Ended December 31, 2023
					Weighted-Average
					Grant Date
	Shares				Fair Value
Grants outstanding at beginning of the period		1,829,632		(1)	$	93.59
Granted		1,165,925		(2)		151.20
Vested		(644,614	)			93.69
Forfeited		(110,439	)			112.27
Grants outstanding at end of the period		2,240,504			$	120.17

(1) Included in RSUs outstanding at the beginning of the year ended December 31, 2023 are 38,500 shares of PSUs (the “March 2022 PSUs”) with performance conditions related to regulatory approval of the Company’s product candidates.

(2) Included in RSUs granted during the year ended December 31, 2023 are 502,225 shares with performance conditions (the “March 2023 PSUs”), which are related to regulatory approval of certain of the Company's product candidates and achievement of a certain financial performance target.

The weighted-average grant date fair value of RSUs granted during the years ended December 31, 2022 and 2021 was $85.39 and $85.32, respectively. The fair values of RSUs vested during the years ended December 31, 2023, 2022 and 2021 totaled $82.6 million, $33.1 million and $23.1 million, respectively.

As a result of the regulatory approval of ELEVIDYS in June 2023 and the achievement of the Company's financial performance target during the year ended December 31, 2023, the March 2023 PSUs became eligible for vesting and, as a result, the Company recorded stock-based compensation expense of $26.3 million. Vesting of the March 2023 PSUs is contingent on the fulfillment of remaining service conditions. The maximum remaining expense associated with the March 2023 PSUs, excluding forfeitures, is $48.5 million. The associated expense will be recognized over approximately the next 1.2 years.

As of December 31, 2023, the performance conditions for the March 2022 PSUs were deemed not probable of being achieved, and as such, no stock-based compensation related to these PSUs was recognized. If the performance conditions of the March 2022 PSUs are met within the required time frame, the Company may recognize up to $3.3 million of stock-based compensation expense, excluding forfeitures. The remaining RSUs granted during the periods presented in the table have only service-based criteria and vest over four years.

2013 Employee Stock Purchase Plan

Under the Company’s 2013 ESPP, participating employees purchase common stock through payroll deductions. The purchase price is equal to 85% of the lower of the closing price of the Company’s common stock on the first business day and the last business day of the relevant purchase period. The 24-month offering period will end between February 29, 2024 and August 31, 2025. The following table summarizes the Company’s ESPP activity for each of the periods indicated:


	For the Year Ended December 31,
	2023		2022		2021
Number of shares purchased		153,027		115,124		111,171
Proceeds received (in millions)	$	10.8	$	7.5	$	7.8

Stock-based Compensation Expense

The following table summarizes stock-based compensation expense by function included within the consolidated statements of operations and comprehensive loss:


	For the Year Ended December 31,
	2023		2022		2021
	(in thousands)
Research and development	$	82,489	$	61,293	$	50,526
Selling, general and administrative		100,025		171,725		63,417
Total stock-based compensation	$	182,514	$	233,018	$	113,943

The following table summarizes stock-based compensation expense by grant type included within the consolidated statements of operations and comprehensive loss:


	For the Year Ended December 31,
	2023		2022		2021
	(in thousands)
Stock options	$	79,472	$	174,868	$	68,995
Restricted stock units		97,808		52,601		40,055
Employee stock purchase plan		5,234		5,549		4,893
Total stock-based compensation	$	182,514	$	233,018	$	113,943

As of December 31, 2023, there was $260.7 million of total unrecognized stock-based compensation expense related to the Company’s stock-based compensation plans, including estimated forfeitures. The expense is expected to be recognized over a weighted-average period of approximately three years. Of this amount, $110.3 million related to options with service conditions only, $6.6 million related to RSUs with certain performance conditions not met and the remaining $143.8 million related to restricted stock units with service conditions only.

OTHER ASSETS (Additional Information) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Prepaid Expense and Other Assets, Current [Abstract]
Other Restricted Assets, Noncurrent	$ 15,579	$ 19,024	$ 9,654

Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
Document and Entity Information - USD ($) $ in Thousands	Dec. 31, 2023	Feb. 23, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	SRPT
Entity Registrant Name	Sarepta Therapeutics, Inc.
Entity Central Index Key	0000873303
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
ICFR Auditor Attestation Flag	true
Entity File Number	001-14895
Entity Tax Identification Number	93-0797222
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	215 First Street
Entity Address, Address Line Two	Suite 415
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	274-4000
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.0001 par value
Security Exchange Name	NASDAQ
Document Annual Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		93,855,410
Entity Public Float			$ 10,681,685,915
Document Financial Statement Error Correction [Flag]	false
Documents Incorporated by Reference	The registrant has incorporated by reference into Part II and Part III of this Annual Report on Form 10-K portions of its definitive Proxy Statement for the 2024 Annual Meeting of Stockholders to be filed no later than 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
Auditor Name	KPMG LLP
Auditor Location	Boston, MA
Auditor Firm ID	185

Net Loss Per Share - Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Net loss	$ (535,977)	$ (703,488)	$ (418,780)
Weighted-average common shares outstanding - basic	92,398	87,559	81,262
Effect of dilutive securities*	0	0	0
Weighted-average common shares outstanding - diluted	92,398	87,559	81,262
Net loss per share - basic	$ (5.8)	$ (8.03)	$ (5.15)
Net loss per share - diluted	$ (5.8)	$ (8.03)	$ (5.15)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 20: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 27: http://www.xbrl.org/2003/role/disclosureRef
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Reference 32: http://www.xbrl.org/2003/role/exampleRef
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-Topic 280
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-Name Accounting Standards Codification
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Reference 37: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Product Revenues, Net, Accounts Receivable, Net and Reserves for Product Revenues - Summary of Total Reserves Included in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Receivables, Net, Current [Abstract]
Reduction to accounts receivable, net	$ 64,697	$ 25,914
Component of accrued expenses	100,075	68,784
Total reserves	$ 164,772	$ 94,698

Other Assets - Summary of Other Non-current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Prepaid Expense and Other Assets, Noncurrent [Abstract]
Manufacturing-related deposits and prepaids	$ 74,204	$ 97,409
Intangible assets, net	29,620	7,578
Other Restricted Assets, Noncurrent	15,579	19,024	$ 9,654
Strategic investments	6,527	31,321
Prepaid maintenance services	5,466	3,403
Prepaid clinical expenses	2,133	2,150
Other	3,242	2,084
Total other non-current assets	$ 136,771	$ 162,969

NET LOSS PER SHARE (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Basic and Diluted Net Loss Per Share

Given that the Company recorded a net loss for each of the periods presented, there is no difference between basic and diluted net loss per share since the effect of common stock equivalents would be anti-dilutive and are, therefore, excluded from the diluted net loss per share calculation.


	For the Year Ended December 31,
	2023			2022			2021
	(in thousands, except per share amounts)
Net loss	$	(535,977	)	$	(703,488	)	$	(418,780	)
Weighted-average common shares outstanding - basic		92,398			87,559			81,262
Effect of dilutive securities*		—			—			—
Weighted-average common shares outstanding - diluted		92,398			87,559			81,262
Net loss per share — basic and diluted	$	(5.80	)	$	(8.03	)	$	(5.15	)

Equity - Additional Information (Detail) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended
	Oct. 31, 2021 USD ($) $ / shares shares
Class Of Stock [Line Items]
Common stock average price per share \| $ / shares	$ 81
Net proceeds from issue of common stock	$ 548.5
Issuance costs	$ 26.5
Underwritten Public Offering [Member]
Class Of Stock [Line Items]
Common stock issued \| shares	7.1

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 272
-SubTopic 10
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-Paragraph 3
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-URI https://asc.fasb.org//1943274/2147483014/272-10-45-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 272
-SubTopic 10
-Name Accounting Standards Codification
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-URI https://asc.fasb.org//1943274/2147482987/272-10-50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
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-Section 50
-Paragraph 13
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Section 50
-Paragraph 13
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
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-Section 50
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section 50
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-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Section 50
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-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
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-Section S99
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-Subparagraph (SX 210.5-02(28))
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-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
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-Section S99
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-Subparagraph (SX 210.5-02(29))
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-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (SX 210.6-03(i)(2))
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Paragraph 3
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Subparagraph (SX 210.6-03(i)(2)(i))
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-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

+ Details

Stock Based Compensation - Summary of Stock-Based Compensation Expense by Grant Type Included within Consolidated Statements of Operations and Comprehensive Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 182,514	$ 233,018	$ 113,943
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	79,472	174,868	68,995
Restricted Stock Awards/Units (RSAs/RSUs) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	97,808	52,601	40,055
Employee Stock Purchase Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 5,234	$ 5,549	$ 4,893

FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured and Carried at Fair Value


	Fair Value Measurement as of December 31, 2023
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets
Money market funds	$	63,919	$	63,919	$	—	$	—
Commercial paper		113,362		—		113,362		—
Government and government agency bonds		1,001,137		—		1,001,137		—
Corporate bonds		130,380		—		130,380		—
Strategic investments		6,527		5,527		—		1,000
Certificates of deposit		56,621		—		56,621		—
Total assets	$	1,371,946	$	69,446	$	1,301,500	$	1,000

Liabilities
Contingent consideration	$	38,100	$	—	$	—	$	38,100
Total liabilities	$	38,100	$	—	$	—	$	38,100

	Fair Value Measurement as of December 31, 2022
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets
Money market funds	$	467,553	$	467,553	$	—	$	—
Commercial paper		211,369		—		211,369		—
Government and government agency bonds		807,540		—		807,540		—
Corporate bonds		125,741		—		125,741		—
Strategic investments		31,321		321		—		31,000
Certificates of deposit		42,745		—		42,745		—
Total assets	$	1,686,269	$	467,874	$	1,187,395	$	31,000

Liabilities
Contingent consideration	$	36,900	$	—	$	—	$	36,900
Total liabilities	$	36,900	$	—	$	—	$	36,900

Summary of Fair Value of Level 3 Financial Assets

The following table represents a roll-forward of the fair value of Level 3 financial assets for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Fair value, beginning of year	$	31,000		$	32,412
Additions		4,000			1,163
Transfers out of Level 3		(4,000	)		—
Changes in estimated fair value		(30,000	)		(2,575	)
Fair value, end of year	$	1,000		$	31,000

Summary of Fair Value of Level 3 Financial Liabilities

The following table represents a roll-forward of the fair value of Level 3 financial liabilities for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Fair value, beginning of year	$	36,900		$	43,600
Additions		—			—
Liabilities terminated		(800	)		—
Changes in estimated fair value, net		2,000			(6,700	)
Fair value, end of year	$	38,100		$	36,900

A n

STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2023

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity for the period indicated:


	For the Year Ended December 31, 2023
				Weighted-Average
	Shares			Exercise Price
Grants outstanding at beginning of the period		9,130,140		$	70.04
Granted		1,186,399			147.71
Exercised		(528,909	)		76.68
Cancelled and forfeited		(204,935	)		103.74
Grants outstanding at end of the period		9,582,695		$	78.57

Grants exercisable at end of the period		5,951,953		$	70.91
Grants vested and expected to vest at end of the period		9,216,033		$	77.01

The weighted-average grant date fair value per share of stock options granted during the years ended December 31, 2023, 2022 and 2021 was $70.94, $48.82 and $48.16, respectively.


			Weighted-Average
	Aggregate		Remaining
	Intrinsic Value		Contractual
	(in thousands)		Life (Years)
Options outstanding at December 31, 2023	$	288,119		5.7
Options exercisable at December 31, 2023	$	202,405		4.9
Options vested and expected to vest at December 31, 2023	$	285,706		5.5

Summary of Company's Stock Options Vested and Exercised

The following table summarizes the Company’s shares vested and stock options exercised for each of the periods indicated:


	For the Year Ended December 31,
	2023		2022		2021
	(in thousands)
Aggregate grant date fair value of shares vested	$	142,692	$	140,889	$	79,068
Aggregate intrinsic value of stock options exercised	$	29,711	$	12,150	$	10,622

Summary of Employee Stock Purchase Plan Activity and Expense

The following table summarizes the Company’s ESPP activity for each of the periods indicated:


	For the Year Ended December 31,
	2023		2022		2021
Number of shares purchased		153,027		115,124		111,171
Proceeds received (in millions)	$	10.8	$	7.5	$	7.8

Summary of Stock-Based Compensation Expense by Function Included within Consolidated Statements of Operations and Comprehensive Loss

The following table summarizes stock-based compensation expense by function included within the consolidated statements of operations and comprehensive loss:


	For the Year Ended December 31,
	2023		2022		2021
	(in thousands)
Research and development	$	82,489	$	61,293	$	50,526
Selling, general and administrative		100,025		171,725		63,417
Total stock-based compensation	$	182,514	$	233,018	$	113,943

Summary of Stock-Based Compensation Expense by Grant Type Included within Consolidated Statements of Operations and Comprehensive Loss

The following table summarizes stock-based compensation expense by grant type included within the consolidated statements of operations and comprehensive loss:


	For the Year Ended December 31,
	2023		2022		2021
	(in thousands)
Stock options	$	79,472	$	174,868	$	68,995
Restricted stock units		97,808		52,601		40,055
Employee stock purchase plan		5,234		5,549		4,893
Total stock-based compensation	$	182,514	$	233,018	$	113,943

Restricted Stock Units (RSUs) [Member]

Summary of Restricted Stock Award and Restricted Stock Units Activity

The following table summarizes the Company’s RSU activity for the period indicated:


	For the Year Ended December 31, 2023
					Weighted-Average
					Grant Date
	Shares				Fair Value
Grants outstanding at beginning of the period		1,829,632		(1)	$	93.59
Granted		1,165,925		(2)		151.20
Vested		(644,614	)			93.69
Forfeited		(110,439	)			112.27
Grants outstanding at end of the period		2,240,504			$	120.17

Stock Options [Member]

Assumptions for Measuring Fair Values of Stocks

The fair values of stock options granted during the periods presented are measured on the date of grant using the Black-Scholes-Merton option-pricing model, with the following assumptions:


	For the Year Ended December 31,
	2023	2022	2021
Risk-free interest rate (1)	3.5 - 4.9%	1.6 - 4.2%	0.4 - 1.3%
Expected dividend yield (2)	—	—	—
Expected term (3)	5.23 years	5.09 years	4.99 years
Expected volatility (4)	46.8 - 63.2%	52.4 - 72.9%	60.1 - 70.8%

(1)

(2)

The expected dividend yield is zero as the Company has not paid any dividends to date and does not expect to pay dividends in the future.

(3)

The expected term is estimated using historical exercise behavior.

(4)

The expected volatility is the implied volatility in exchange-traded options of the Company’s common stock.

Organization and Nature of Business - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash, cash equivalents and investments	$ 1,691,800
Short-term investments	1,247,820	$ 1,022,597
Cash and cash equivalents	428,430	966,777	$ 2,115,869
Restricted cash in other assets	$ 15,579	$ 19,024	$ 9,654

Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended				3 Months Ended	12 Months Ended
	Nov. 30, 2022 USD ($)	Oct. 31, 2021 USD ($)	Mar. 31, 2021 USD ($)	Oct. 31, 2018 Suite	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 Suite	Jun. 30, 2018 mo	Jun. 30, 2018 Suite
Commitments And Contingencies [Line Items]
Amendment Implemented Fee					$ 60.0
Long-Term Purchase Commitment, Amount					$ 54.7
Research and Development Expense [Member]
Commitments And Contingencies [Line Items]
Non Refundable Advance Payments						$ 2.6
First Installments [Member]
Commitments And Contingencies [Line Items]
Installments Date of implemented fee					Mar. 01, 2024
Amendment Implemented Fee					$ 20.0
Thermo Fisher Scientific, Inc. [Member]
Commitments And Contingencies [Line Items]
Research and development expense						0.0	$ 54.0	$ 0.0
CRO [Member]
Commitments And Contingencies [Line Items]
Cancellable future commitments						580.0
CRO [Member] \| Other Funding Commitments [Member]
Commitments And Contingencies [Line Items]
Expenditures incurred by CROs						$ 112.2	$ 78.7	$ 47.9
Supply Agreement [Member] \| Thermo Fisher Scientific, Inc. [Member]
Commitments And Contingencies [Line Items]
Number of dedicated clean room suites										4	4
Agreement expiration date				Dec. 31, 2028
Supply Agreement [Member] \| Thermo Fisher Scientific, Inc. [Member] \| Research and Development Expense [Member]
Commitments And Contingencies [Line Items]
Research and development expense		$ 24.4
Derecognition of right of use asset		23.4
Derecognition of lease liabilities		20.1
Recognition of loss		3.3
Non Refundable Advance Payments		$ 21.1
Catalent Agreements [Member]
Commitments And Contingencies [Line Items]
Recognition Of Right Of Use Asset	$ 19.2
Increase in long-term deposits manufacturing	$ 3.9
Catalent Agreements [Member] \| Research and Development Expense [Member]
Commitments And Contingencies [Line Items]
Derecognition of right of use asset			$ 22.8
Derecognition of lease liabilities			20.0
Recognition of loss			$ 2.8
Catalent Agreements [Member] \| Paragon [Member]
Commitments And Contingencies [Line Items]
Number of dedicated clean room suites \| Suite				2					4
Number of additional clean room suites available on optional reserve \| Suite				2
Agreement expiration date				Dec. 31, 2024
Clinical and Commercial Supply Agreement [Member] \| Aldevron LLC [Member]
Commitments And Contingencies [Line Items]
Agreement expiration date						Dec. 31, 2026
Agreement expiration description						The Company has the option to extend the term of the Aldevron Agreements by one year if the Company delivers a written notice of its intention to extend to Aldevron no later than June 1, 2025. Both parties have the right to early terminate without additional penalty. The Company has determined that the Aldevron Agreements do not contain an embedded lease because it does not convey the right to control the use of Aldevron’s facility or related equipment therein.

OTHER ASSETS (Tables)

12 Months Ended

Dec. 31, 2023

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Summary of Other Current Assets

The following table summarizes the Company’s other current assets for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Manufacturing-related deposits and prepaids	$	102,181	$	66,455
Collaboration and other receivables		29,786		41,758
Prepaid maintenance services		11,281		9,815
Prepaid clinical and pre-clinical expenses		10,280		11,237
Tax-related receivables and prepaids		6,862		1,903
Prepaid insurance		3,352		3,717
Interest receivable		2,731		3,311
Prepaid commercial expenses		2,729		2,947
Prepaid research expenses		2,512		1,927
Other		8,181		6,821
Total other current assets	$	179,895	$	149,891

Summary of Other Non-current Assets

The following table summarizes the Company’s other non-current assets for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Manufacturing-related deposits and prepaids	$	74,204	$	97,409
Intangible assets, net		29,620		7,578
Restricted cash*		15,579		19,024
Strategic investments		6,527		31,321
Prepaid maintenance services		5,466		3,403
Prepaid clinical expenses		2,133		2,150
Other		3,242		2,084
Total other non-current assets	$	136,771	$	162,969

Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Summary of Estimated Useful Lives of Plant and Equipment (Detail)	Dec. 31, 2023
Lab and Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	5 years
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	5 years
Software and Computer Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	3 years
Software and Computer Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	5 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	Property, Plant and Equipment, Net
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	7 years
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	Property, Plant and Equipment, Net
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	25 years
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	Property, Plant and Equipment, Net
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	30 years

Product Revenues, Net, Accounts Receivable, Net and Reserves for Product Revenues - Summary of Product Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Product Information [Line Items]
Products, net	$ 1,144,876	$ 843,769	$ 612,401
PMO Products [Member]
Product Information [Line Items]
Products, net	944,520	843,769
PMO Products [Member] \| United States [Member]
Product Information [Line Items]
Products, net	797,944	747,101
PMO Products [Member] \| Rest of World [Member]
Product Information [Line Items]
Products, net	146,576	96,668
ELEVIDYS [Member]
Product Information [Line Items]
Products, net	200,356	0
ELEVIDYS [Member] \| United States [Member]
Product Information [Line Items]
Products, net	$ 200,356	$ 0

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479941/924-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-30

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-40

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-4

+ Details

INTANGIBLE ASSETS, NET

12 Months Ended

Dec. 31, 2023

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLE ASSETS, NET

11. INTANGIBLE ASSETS, NET

The following table summarizes the components of the Company’s intangible assets for each of the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
In-licensed rights	$	32,673		$	8,573
Patents		4,889			5,106
Software licenses		302			302
Intangible assets, gross		37,864			13,981
Less: accumulated amortization		(8,244	)		(6,403	)
Intangible assets, net	$	29,620		$	7,578

The in-licensed rights relate to agreements with UWA, Nationwide, BioMarin and PPMD. For the year ended December 31, 2023, the Company had $24.1 million in additions of in-licensed rights, which are being amortized on a straight-line basis over the remaining life of the related patent because the life of the related patent reflects the expected time period that the Company will benefit from the in-licensed right. The weighted-average remaining amortization period for the in-licensed rights additions during 2023 is 13.8 years. For more information related to the Company's in-licensed rights related to its license or settlement agreements with Nationwide, BioMarin and UWA, please refer to Note 3. License and Collaboration Agreements. For the years ended December 31, 2023, 2022 and 2021, the Company recorded $1.9 million, $1.9 million, and $1.4 million, respectively, of amortization expense related to intangible assets.

The following table summarizes the estimated future amortization for intangible assets:


	As of December 31, 2023
	(in thousands)
2024	$	2,717
2025		2,660
2026		2,528
2027		2,458
2028		2,377
Thereafter		16,880
Total	$	29,620

CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES (Tables)

12 Months Ended

Dec. 31, 2023

Cash and Cash Equivalents [Abstract]

Summary of Company Financial Assets with Maturities of Less Than 90 Days Included in Cash Equivalents

The following table summarizes the Company’s financial assets with maturities of less than 90 days from the date of purchase included in cash equivalents in the consolidated balance sheets for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Money market funds	$	63,919	$	467,553
Commercial paper		53,680		33,190
Government and government agency bonds		—		128,451
Corporate bonds		—		3,157
Total	$	117,599	$	632,351

Summary of Company Cash, Cash Equivalents and Investments

The following tables summarize the Company’s cash, cash equivalents and short-term investments for each of the periods indicated:


	As of December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
	(in thousands)
Cash and money market funds	$	374,750	$	—	$	—		$	374,750
Commercial paper		113,362		—		—			113,362
Government and government agency bonds		1,000,302		1,006		(171	)		1,001,137
Corporate bonds		130,270		118		(8	)		130,380
Certificates of deposit		56,621		—		—			56,621
Total cash, cash equivalents and investments	$	1,675,305	$	1,124	$	(179	)	$	1,676,250
As reported:
Cash and cash equivalents	$	428,430	$	—	$	—		$	428,430
Short-term investments		1,246,875		1,124		(179	)		1,247,820
Total cash, cash equivalents and investments	$	1,675,305	$	1,124	$	(179	)	$	1,676,250

	As of December 31, 2022
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
	(in thousands)
Cash and money market funds	$	801,979	$	—	$	—		$	801,979
Commercial paper		211,369		—		—			211,369
Government and government agency bonds		808,904		178		(1,542	)		807,540
Corporate bonds		126,014		9		(282	)		125,741
Certificates of deposit		42,745		—		—			42,745
Total cash, cash equivalents and investments	$	1,991,011	$	187	$	(1,824	)	$	1,989,374
As reported:
Cash and cash equivalents	$	966,768	$	9	$	—		$	966,777
Short-term investments		1,024,243		178		(1,824	)		1,022,597
Total cash, cash equivalents and investments	$	1,991,011	$	187	$	(1,824	)	$	1,989,374

Cash, Cash Equivalents and Marketable Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash and Cash Equivalents [Abstract]
Weighted average maturity period of available-for-sale securities	5 months	4 months

Stock Based Compensation - Assumptions for Measuring Fair Values of Stocks (Detail)

12 Months Ended

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Expected dividend yield

0.00%

Stock Options [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Risk-free interest rate, minimum

^[1]

3.50%

1.60%

0.40%

Risk-free interest rate, maximum

4.90%

^[1]

4.20%

^[1]

1.30%

^[1]

1.30%

2.50%

3.00%

Expected dividend yield

^[2]

0.00%

Expected term

^[3]

5 years 2 months 23 days

5 years 1 month 2 days

4 years 11 months 26 days

Expected volatility, minimum

^[4]

46.80%

52.40%

60.10%

Expected volatility, maximum

63.20%

^[4]

72.90%

^[4]

70.80%

^[4]

68.20%

68.90%

60.80%

[1]	The risk-free interest rate is estimated using an average of Treasury bill interest rates over a historical period commensurate with the expected term of the option that correlates to the prevailing interest rates at the time of grant.
[2]	The expected dividend yield is zero as the Company has not paid any dividends to date and does not expect to pay dividends in the future.
[3]	The expected term is estimated using historical exercise behavior.
[4]	The expected volatility is the implied volatility in exchange-traded options of the Company’s common stock.

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

INVENTORY

12 Months Ended

Dec. 31, 2023

Inventory Disclosure [Abstract]

INVENTORY

8. INVENTORY

The following table summarizes the components of the Company’s inventory for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Raw materials	$	133,963	$	59,181
Work in progress		318,458		269,185
Finished goods		61,806		38,147
Total inventory	$	514,227	$	366,513

No material inventory reserves existed as of December 31, 2023 or 2022. The Company classifies inventory associated with its PMO Products as non-current inventory when consumption of the inventory is expected beyond the Company's normal PMO Product inventory operating cycle of two years. Non-current inventory consists of raw materials and work in progress associated with the PMO Products.

The following table summarizes the balance sheet classification of the Company's inventory for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Balance sheet classification
Inventory	$	322,859	$	203,968
Non-current inventory		191,368		162,545
Total inventory	$	514,227	$	366,513

Intangible Assets, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 37,864	$ 13,981
Amortization of in-licensed rights	$ 1,559	714	$ 706
Remaining Amortization Period	13 years 9 months 18 days
Patents [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 4,889	5,106
Software Development [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	302	302
License Agreement [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	24,100
Amortization of in-licensed rights	1,900	$ 1,900	$ 1,400
ELEVIDYS [Member] \| Nationwide License Agreement [Member]
Finite Lived Intangible Assets [Line Items]
Carrying value	$ 22,200

LEASES

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

LEASES

19. LEASES

The Company has real estate operating leases in Cambridge, Andover, Burlington and Bedford, Massachusetts, Dublin and Columbus, Ohio, and Durham, North Carolina that provide for scheduled annual rent increases throughout each lease’s term. The Company has also identified leases embedded in certain of its manufacturing and supply agreements as the Company determined that it controls the use of the facilities and related equipment therein. For more information related to the lease embedded in manufacturing and supply agreements with Catalent, Inc. (“Catalent”), please refer to Note 21, Commitments and Contingencies.

Bedford, Massachusetts

On April 22, 2022, the Company entered into a lease agreement (the “Bedford Lease”) for 288,000 square feet of to-be-constructed research and development and manufacturing space in Bedford, Massachusetts. The term of the Bedford Lease commences upon the landlord’s completion of the initial construction of the core and shell of the building, at which time the Company will obtain control of the premises and commence internal construction activities. The initial term of the Bedford Lease is anticipated to terminate on December 31, 2038. The Company has two options to extend the lease for a period of ten years each, exercisable under certain conditions and at a market rate determined in accordance with the lease agreement.

In May 2022, in connection with the execution of the Bedford Lease, the Company issued a letter of credit collateralized by cash deposits of approximately $8.4 million, which was included in other non-current assets on the Company’s consolidated balance sheets. Such letter of credit shall be reduced to approximately $5.6 million at the commencement of the fourth rent year, provided certain conditions set forth in the Bedford Lease are satisfied.

Undiscounted minimum rent payments due over the term of the lease aggregate to $307.4 million. Additionally, the Company is responsible for reimbursing the landlord for the Company’s share of the property’s operating expenses and property taxes. The Bedford Lease also provides for a tenant improvement allowance from the landlord of up to $72.0 million to be used towards costs incurred by the Company in the design and construction of the premises.

The Bedford Lease commenced in May 2023 as the Company obtained control of the premises (the “Bedford Lease Commencement”). The Company has a lease liability and ROU asset of $94.7 million and $71.6 million, respectively, on the consolidated balance sheets as of December 31, 2023 related to the Bedford Lease. The Company recorded the $72.0 million tenant improvement allowance as a reduction to the ROU asset and lease liability at the date of the Bedford Lease Commencement. Tenant improvement costs incurred by the Company that had been reimbursed by the landlord totaled $13.1 million as of December 31, 2023 and are recorded as an increase to the lease liability within the Company's consolidated balance sheets.

Columbus, Ohio

On December 22, 2018, the Company entered into a lease agreement for a research and development facility in Columbus, Ohio. On May 19, 2022 (the “Columbus Lease Amendment Date”), the Company entered into an amendment to the Columbus Lease to expand the footprint and extend the lease term from June 2026 to December 2036 (the “Columbus Amendment,” together with the Columbus Amendment, the lease agreement is referred to as the “Columbus Lease”). The Columbus Amendment will expand from its current form of approximately 78,000 square feet to 167,000 square feet through a series of expansion spaces commencing at various periods through January 1, 2025.

Each expansion space commences on the date when the landlord will deliver control of that space for the Company to carry out design and construction activities (the “Columbus Commencement Date”). The Company is obligated to pay rent on each expansion space nine months after the Columbus Commencement Date. The Columbus Lease expires on December 31, 2036, and the Company has options to extend the lease by five years in both 2036 and 2041. Each option is exercisable under certain conditions and at a market rate determined in accordance with the lease agreement. The total undiscounted rent payments due over the 15-year term from the Columbus Lease Amendment Date aggregate to $38.9 million.

The Company commenced design and construction activities on areas of the premises of approximately 18,000 square feet (the “Second Expansion Space”), 36,000 square feet (the “Initial Expansion Space”) and 19,000 square feet (the “Third Expansion Space”) on June 1, 2022, October 1, 2022 and September 1, 2023, respectively. As a result, it was determined that the lease related to the Second Expansion Space, the Initial Expansion Space and the Third Expansion Space had commenced on those three dates, respectively. The total ROU asset and lease liability associated with the Columbus Lease, inclusive of the Third Expansion Space, the Second Expansion Space and the Initial Expansion Space, was $11.4 million and $18.5 million, respectively, as of December 31, 2023.

As of December 31, 2023, ROU assets for operating leases were $130.0 million and operating lease liabilities were $158.8 million. The following table contains a summary of the lease costs recognized and other information pertaining to the Company’s operating leases for the periods indicated:


	For the Year Ended December 31,
	2023			2022
	(in thousands)
Lease cost
Operating lease cost	$	29,895		$	18,184
Variable lease cost		38,442			35,505
Total lease cost	$	68,337		$	53,689

Other information
Operating lease payments	$	21,608		$	20,778
Operating lease liabilities arising from obtaining ROU assets	$	80,203		$	40,006
Weighted-average remaining lease term	11.2 years			6.4 years
Weighted-average discount rate		9.1	%		8.3	%

The following table summarizes maturities of lease liabilities and the reconciliation of lease liabilities as of December 31, 2023:


	For the Year Ended December 31, 2023
	(in thousands)
2024	$	33,718
2025		34,477
2026		28,006
2027		27,995
2028		28,611
Thereafter		245,835
Total minimum lease payments		398,642
Less: imputed interest		(239,832	)
Total operating lease liabilities	$	158,810
Included in the consolidated balance sheet:
Current portion of lease liabilities within other current liabilities	$	17,845
Lease liabilities, non-current		140,965
Total operating lease liabilities	$	158,810

Product Revenues, Net, Accounts Receivable, Net and Reserves for Product Revenues - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Principal Transaction Revenue [Line Items]
Product sales receivable, net of discounts and allowances	$ 400.3	$ 214.6
Customer One [Member] \| Customer Concentration Risk [Member] \| Accounts Receivable [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage	40.00%	36.00%
Customer One [Member] \| Customer Concentration Risk [Member] \| Sales Revenue Net [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage	41.00%	48.00%	48.00%
Customer Two [Member] \| Customer Concentration Risk [Member] \| Accounts Receivable [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage	19.00%	35.00%
Customer Two [Member] \| Customer Concentration Risk [Member] \| Sales Revenue Net [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage	26.00%	33.00%	39.00%
Customer Three [Member] \| Customer Concentration Risk [Member] \| Accounts Receivable [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage	19.00%	12.00%
Customer Three [Member] \| Customer Concentration Risk [Member] \| Sales Revenue Net [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage			10.00%
Total [Member] \| Customer Concentration Risk [Member] \| Sales Revenue Net [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage			90.00%
No Individual [Member] \| Customer Concentration Risk [Member] \| Sales Revenue Net [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage	10.00%	10.00%	10.00%
Customers Exceed [Member] \| Customer Concentration Risk [Member] \| Sales Revenue Net [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage	10.00%
Customers Not Exceed [Member] \| Customer Concentration Risk [Member] \| Sales Revenue Net [Member]
Principal Transaction Revenue [Line Items]
Concentration of credit risk percentage	10.00%	10.00%

Commitments and Contingencies - Summary of Non-Cancelable Contractual Obligations Arising From Long-term Contractual Arrangements (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2024	$ 1,032,159
2025	150,767
2026	106,984
2027	77,640
2028	72,280
Thereafter	0
Total manufacturing commitments	$ 1,439,830

ACCRUED EXPENSES (Tables)

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Summary of Accrued Expenses

The following table summarizes the Company’s accrued expenses for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Product revenue related reserves	$	100,075	$	68,784
Accrued employee compensation costs		78,732		65,946
Accrued clinical and pre-clinical costs		34,669		28,884
Accrued contract manufacturing costs		33,024		202,173
Accrued professional fees		17,187		12,061
Accrued income taxes		13,766		12,521
Accrued royalties		12,070		8,636
Accrued milestone and license expense		11,375		7,702
Accrued interest expense		4,395		4,956
Accrued collaboration cost-sharing		1,076		2,019
Other		8,628		5,314
Total accrued expenses	$	314,997	$	418,996

Income Taxes - Analysis of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 154,948	$ 241,826
Difference in depreciation and amortization	36,611	39,725
Research and development tax credits	374,017	261,067
Stock-based compensation	94,452	80,193
Lease liabilities	33,792	11,782
Capitalized inventory	35,269	33,366
Debt discount	25,597	35,975
Capitalized research and development costs	106,534	74,886
Other	50,308	44,022
Total deferred tax assets	911,528	822,842
Deferred tax liabilities:
Right of use asset	(25,800)	(9,174)
Debt discount	0	0
Total deferred tax liabilities	(25,800)	(9,174)
Valuation allowance	(883,665)	(811,908)
Net deferred tax assets	$ 2,063	$ 1,760

COMMITMENTS AND CONTINGENCIES (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Summary of Aggregate Non-Cancelable Contractual Obligations Arising from Manufacturing Obligations

The following table presents non-cancelable contractual obligations arising from long-term contractual arrangements, including obligations related to leases embedded in certain supply agreements:


	As of December 31, 2023
	(in thousands)
2024	$	1,032,159
2025		150,767
2026		106,984
2027		77,640
2028		72,280
Thereafter		—
Total manufacturing commitments	$	1,439,830

INDEBTEDNESS (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Summary of Debt Facilities

The following table summarizes the Company’s debt facilities for the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Principal amount of the 2024 Notes	$	105,847		$	419,371
Principal amount of the 2027 Notes		1,150,000			1,150,000
Unamortized discount - debt issuance costs of 2024 Notes		(364	)		(3,059	)
Unamortized discount - debt issuance costs of 2027 Notes		(17,485	)		(22,020	)
Net carrying value of the convertible notes		1,237,998			1,544,292

Fair value of 2024 Notes	$	144,833		$	765,046
Fair value of 2027 Notes		1,172,276			1,308,482
Total fair value of debt facilities	$	1,317,109		$	2,073,528

Summarizes Total Gross Payments Due under Company's Debt Arrangements

The following table summarizes the total principal and contractual interest payments due under the Company’s debt arrangements:


	As of December 31, 2023
	Principal		Interest		Total Payments
	(in thousands)
2024	$	105,847	$	15,963	$	121,810
2025		—		14,375		14,375
2026		—		14,375		14,375
2027		1,150,000		14,375		1,164,375
Total payments	$	1,255,847	$	59,088	$	1,314,935

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69B

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
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-Name Accounting Standards Codification
-Section 55
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-URI https://asc.fasb.org//1943274/2147481568/470-20-55-69E

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
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-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-3

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Paragraph 2
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-Paragraph 1A
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Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
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-URI https://asc.fasb.org//1943274/2147480848/942-470-50-3

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-7

+ Details

Accrued Expenses - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Product revenue related reserves	$ 100,075	$ 68,784
Accrued employee compensation costs	78,732	65,946
Accrued clinical and pre-clinical costs	34,669	28,884
Accrued contract manufacturing costs	33,024	202,173
Accrued professional fees	17,187	12,061
Accrued income taxes	13,766	12,521
Accrued royalties	12,070	8,636
Accrued milestone and license expense	11,375	7,702
Accrued interest expense	4,395	4,956
Accrued collaboration cost-sharing	1,076	2,019
Other	8,628	5,314
Total accrued expenses	$ 314,997	$ 418,996

Stock Based Compensation - Summary of Company's Stock Options Vested and Exercised (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Aggregate grant date fair value of shares vested	$ 142,692	$ 140,889	$ 79,068
Aggregate intrinsic value of stock options exercised	$ 29,711	$ 12,150	$ 10,622

Inventory - Summarizes The Balance Sheet Classification (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory Disclosure [Abstract]
Inventory	$ 322,859	$ 203,968
Non-current inventory	191,368	162,545
Total inventory	$ 514,227	$ 366,513

CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES

12 Months Ended

Dec. 31, 2023

Cash and Cash Equivalents [Abstract]

CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES

6. CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES


	As of December 31,
	2023		2022
	(in thousands)
Money market funds	$	63,919	$	467,553
Commercial paper		53,680		33,190
Government and government agency bonds		—		128,451
Corporate bonds		—		3,157
Total	$	117,599	$	632,351

It is the Company’s policy to mitigate credit risk in its financial assets by maintaining a well-diversified portfolio that limits the amount of exposure as to maturity and investment type. The weighted-average maturity of the Company's available-for-sale securities was approximately five and four months as of December 31, 2023 and 2022, respectively.

The following tables summarize the Company’s cash, cash equivalents and short-term investments for each of the periods indicated:


	As of December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
	(in thousands)
Cash and money market funds	$	374,750	$	—	$	—		$	374,750
Commercial paper		113,362		—		—			113,362
Government and government agency bonds		1,000,302		1,006		(171	)		1,001,137
Corporate bonds		130,270		118		(8	)		130,380
Certificates of deposit		56,621		—		—			56,621
Total cash, cash equivalents and investments	$	1,675,305	$	1,124	$	(179	)	$	1,676,250
As reported:
Cash and cash equivalents	$	428,430	$	—	$	—		$	428,430
Short-term investments		1,246,875		1,124		(179	)		1,247,820
Total cash, cash equivalents and investments	$	1,675,305	$	1,124	$	(179	)	$	1,676,250

	As of December 31, 2022
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Market Value
	(in thousands)
Cash and money market funds	$	801,979	$	—	$	—		$	801,979
Commercial paper		211,369		—		—			211,369
Government and government agency bonds		808,904		178		(1,542	)		807,540
Corporate bonds		126,014		9		(282	)		125,741
Certificates of deposit		42,745		—		—			42,745
Total cash, cash equivalents and investments	$	1,991,011	$	187	$	(1,824	)	$	1,989,374
As reported:
Cash and cash equivalents	$	966,768	$	9	$	—		$	966,777
Short-term investments		1,024,243		178		(1,824	)		1,022,597
Total cash, cash equivalents and investments	$	1,991,011	$	187	$	(1,824	)	$	1,989,374

Leases - Summary of Lease Costs Recognized Under Topic 842 and Other Information Pertaining to Operating Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease cost
Operating lease cost	$ 29,895	$ 18,184
Variable lease cost	38,442	35,505
Total lease cost	68,337	53,689
Other information
Operating lease payments	21,608	20,778
Operating lease liabilities arising from obtaining ROU assets	$ 80,203	$ 40,006	$ 13,225
Weighted average remaining lease term	11 years 2 months 12 days	6 years 4 months 24 days
Weighted average discount rate	9.10%	8.30%

401 (K) Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2015
Retirement Benefits [Abstract]
Description of 401(k) plan	The Company sponsors a 401(k) Plan (“the Plan”) in the U.S. and other retirement plans in the rest of the world, all of which are defined contribution plans. The Plan is available to all employees who are age 21 or older. Participants may make voluntary contributions and the Company makes matching contributions according to the Plan’s matching formula. Matching contributions fully vest after one year of service for all employees. The expense related to the Plan primarily consists of the Company’s matching contributions.
Defined contribution plan, employers matching contribution, service period					1 year
Defined contribution plan, employers matching contribution, vesting percentage after one years of service					100.00%
Age limit for eligibility to participate in the defined contribution plan				21 years
Expense related to 401 (K) Plan	$ 8.8	$ 6.5	$ 5.3

EQUITY

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

EQUITY

14. EQUITY

In October 2021, the Company issued approximately 7.1 million shares of common stock through an underwritten public offering. The offering price was $81.00 per share. The Company received net proceeds of approximately $548.5 million from the offering, net of commission and offering expenses of approximately $26.5 million.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section 50
-Paragraph 14
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
-Section 50
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-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org//1943274/2147481004/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
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-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
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-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-Name Accounting Standards Codification
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-URI https://asc.fasb.org//505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

Net Loss Per Share - Basic and Diluted Net Loss Per Share (Parenthetical) (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	12.0	11.2	9.7
2024 Convertible Notes [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Conversion of shares excluded from computation of diluted EPS	1.4	5.7	7.8
2027 Convertible Notes [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Conversion of shares excluded from computation of diluted EPS	8.1	8.1	8.1

401 (K) PLAN

12 Months Ended

Dec. 31, 2023

Retirement Benefits [Abstract]

401(K) PLAN

16. 401(K) PLAN

The Company sponsors a 401(k) Plan (“the Plan”) in the U.S. and other retirement plans in the rest of the world, all of which are defined contribution plans. The Plan is available to all employees who are age 21 or older. Participants may make voluntary contributions and the Company makes matching contributions according to the Plan’s matching formula. Matching contributions fully vest after one year of service for all employees. The expense related to the Plan primarily consists of the Company’s matching contributions.

Expense related to the Plan totaled $8.8 million, $6.5 million and $5.3 million for the years ended December 31, 2023, 2022 and 2021, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 70
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480794/715-70-50-1

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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Topic 715
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

+ Details

Income Taxes - Summary of Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current provision:
Federal	$ 4,180	$ 0	$ 0
State	11,111	13,193	(40)
Foreign	753	944	181
Total current provision	16,044	14,137	141
Deferred benefit:
Federal	0	0	0
State	0	0	0
Foreign	(165)	(612)	(309)
Total deferred benefit	(165)	(612)	(309)
Total income tax expense (benefit)	$ 15,879	$ 13,525	$ (168)

Intangible Assets, Net - Summary of Components of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 37,864	$ 13,981
Less: accumulated amortization	(8,244)	(6,403)
Intangible assets, net	29,620	7,578
In-Licensed Rights [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	32,673	8,573
Patents [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	4,889	5,106
Software Licenses [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 302	$ 302

Indebtedness - Summarizes Total Gross Payments Due under Company's Debt Arrangements (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
2024	$ 121,810
2025	14,375
2026	14,375
2027	1,164,375
Total payments	1,314,935
Principal [Member]
Debt Instrument [Line Items]
2024	105,847
2025	0
2026	0
2027	1,150,000
Total payments	1,255,847
Interest [Member]
Debt Instrument [Line Items]
2024	15,963
2025	14,375
2026	14,375
2027	14,375
Total payments	$ 59,088

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

LEASES (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Summary of Lease Costs Recognized Under Topic 842 and Other Information Pertaining to Operating Leases

The following table contains a summary of the lease costs recognized and other information pertaining to the Company’s operating leases for the periods indicated:


	For the Year Ended December 31,
	2023			2022
	(in thousands)
Lease cost
Operating lease cost	$	29,895		$	18,184
Variable lease cost		38,442			35,505
Total lease cost	$	68,337		$	53,689

Other information
Operating lease payments	$	21,608		$	20,778
Operating lease liabilities arising from obtaining ROU assets	$	80,203		$	40,006
Weighted-average remaining lease term	11.2 years			6.4 years
Weighted-average discount rate		9.1	%		8.3	%

Summary of Maturities of Lease Liabilities and Reconciliation of Lease Liabilities Recognized Under Topic 842

The following table summarizes maturities of lease liabilities and the reconciliation of lease liabilities as of December 31, 2023:


	For the Year Ended December 31, 2023
	(in thousands)
2024	$	33,718
2025		34,477
2026		28,006
2027		27,995
2028		28,611
Thereafter		245,835
Total minimum lease payments		398,642
Less: imputed interest		(239,832	)
Total operating lease liabilities	$	158,810
Included in the consolidated balance sheet:
Current portion of lease liabilities within other current liabilities	$	17,845
Lease liabilities, non-current		140,965
Total operating lease liabilities	$	158,810

GAIN FROM SALE OF PRIORITY REVIEW VOUCHER

12 Months Ended

Dec. 31, 2023

Goodwill and Intangible Assets Disclosure [Abstract]

GAIN FROM SALE OF PRIORITY REVIEW VOUCHER

4. GAIN FROM SALE OF PRIORITY REVIEW VOUCHER

In June 2023, the Company entered into an agreement to sell the rare pediatric disease Priority Review Voucher (the “ELEVIDYS PRV”) it received from the FDA in connection with the approval of ELEVIDYS for consideration of $102.0 million, with no commission costs. The closing of the transaction was not subject to the conditions set forth under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and closed in June 2023. The net proceeds were recorded as a gain from sale of the ELEVIDYS PRV during the year ended December 31, 2023 as it did not have a carrying value at the time of the sale.

In February 2021, the Company entered into an agreement to sell the rare pediatric disease PRV it received from the FDA in connection with the approval of AMONDYS 45 (the “AMONDYS 45 PRV”) for consideration of $102.0 million, with no commission costs. Following the termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, in April 2021, the Company completed its sale of the AMONDYS 45 PRV. The net proceeds were recorded as a gain from sale of the AMONDYS 45 PRV during the year ended December 31, 2021 as it did not have a carrying value at the time of the sale.

Fair Value Measurements - Summary of Fair Value of Level 3 Financial Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, beginning of year	$ 1,686,269
Fair value, end of year	1,371,946	$ 1,686,269
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, beginning of year	31,000	32,412
Additions	4,000	1,163
Transfers out of Level 3	(4,000)	0
Changes in estimated fair value	(30,000)	(2,575)
Fair value, end of year	$ 1,000	$ 31,000

INVENTORY (Tables)

12 Months Ended

Dec. 31, 2023

Inventory Disclosure [Abstract]

Summary of Components of Inventory

The following table summarizes the components of the Company’s inventory for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Raw materials	$	133,963	$	59,181
Work in progress		318,458		269,185
Finished goods		61,806		38,147
Total inventory	$	514,227	$	366,513

Summary of Inventory Balance Sheet Classification

The following table summarizes the balance sheet classification of the Company's inventory for each of the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Balance sheet classification
Inventory	$	322,859	$	203,968
Non-current inventory		191,368		162,545
Total inventory	$	514,227	$	366,513

Product Revenues, Net, Accounts Receivable, Net and Reserves for Product Revenues - Summarizes the concentration of the three largest customers (Details) - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Customer One [Member] \| Accounts Receivable [Member]
Principal Transaction Revenue [Line Items]
Concentration Risk, Percentage	40.00%	36.00%
Customer One [Member] \| Revenue Benchmark [Member]
Principal Transaction Revenue [Line Items]
Concentration Risk, Percentage	41.00%	48.00%	48.00%
Customer Two [Member] \| Accounts Receivable [Member]
Principal Transaction Revenue [Line Items]
Concentration Risk, Percentage	19.00%	35.00%
Customer Two [Member] \| Revenue Benchmark [Member]
Principal Transaction Revenue [Line Items]
Concentration Risk, Percentage	26.00%	33.00%	39.00%
Customer Three [Member] \| Accounts Receivable [Member]
Principal Transaction Revenue [Line Items]
Concentration Risk, Percentage	19.00%	12.00%
Customer Three [Member] \| Revenue Benchmark [Member]
Principal Transaction Revenue [Line Items]
Concentration Risk, Percentage			10.00%

Stock Based Compensation - Summary of Stock-Based Compensation Expense by Function Included within Consolidated Statements of Operations and Comprehensive Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 182,514	$ 233,018	$ 113,943
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	82,489	61,293	50,526
Selling, General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 100,025	$ 171,725	$ 63,417

INDEBTEDNESS

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

INDEBTEDNESS

13. INDEBTEDNESS

2027 Convertible Notes Issuance

On September 16, 2022, the Company issued $1,150.0 million aggregate principal amount of convertible senior notes due on September 15, 2027. The 2027 Notes are senior unsecured obligations of the Company and bear interest at a rate of 1.25% per annum, payable semi-annually in cash on each March 15 and September 15, commencing on March 15, 2023. The net proceeds were $1,126.7 million after deducting the discounts and offering expenses of $23.3 million. The debt discount is amortized under the effective interest method and recorded as additional interest expense over the life of the 2027 Notes. The effective interest rate on the 2027 Notes is 1.67%. The aggregate issuance of the 2027 Notes includes the issuance of $20.0 million in aggregate principal amount of 2027 Notes to the Michael A. Chambers Living Trust, an entity affiliated with Michael Chambers, a member of the Company’s board of directors.

The 2027 Notes may be convertible into shares of the Company’s common stock under certain circumstances prior to maturity at a conversion rate of 7.0439 shares per $1,000 principal amount of the 2027 Notes (8,100,485 shares of the Company’s common stock in the aggregate), which represents a conversion price of $141.97 per share, subject to adjustment under certain

conditions. Upon conversion, the Company may pay cash, shares of its common stock or a combination of cash and stock, as determined by the Company at its discretion.

The holders of the 2027 Notes may convert their 2027 Notes at their option only in the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2022, if the last reported sale price per share of common stock exceeds 130% of the conversion price for each of at least 20 trading days during the 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; (2) during the five consecutive business days immediately after any five consecutive trading day period (the “measurement period”) in which the trading price per $1,000 principal amount of 2027 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company's common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company's common stock, as described in the indenture agreement; (4) if the Company calls such notes for redemption; and (5) at any time from, and including, March 15, 2027 until the close of business on the second trading day immediately before the maturity date.

The 2027 Notes are not redeemable by the Company prior to September 20, 2025. On or after September 20, 2025, the Company may redeem for cash all or any portion of the 2027 Notes at a redemption price equal to the principal amount of the 2027 Notes to be redeemed, plus accrued and unpaid interest, if the last reported sale price of the Company’s common stock exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period. Holders of the 2027 Notes have the right to require the Company to repurchase for cash all or a portion of their notes at 100% of its respective principal amount, plus any accrued and unpaid interest, upon the occurrence of a fundamental change as defined in the indenture agreement for the 2027 Notes. The 2027 Notes contain customary covenants and events of default, occurrence of which permits the holders to accelerate all outstanding obligations, including principal and interest.

2022 Capped Call Transactions

In connection with the issuance of the 2027 Notes, the Company entered into privately negotiated capped call transactions with counterparties intended to minimize the impact of potential dilution upon conversion of the 2027 Notes (the “2022 Capped Calls”). The 2022 Capped Calls have an initial strike price of approximately $141.97 per share, which corresponds to the initial conversion price of the 2027 Notes and is subject to anti-dilution adjustments generally similar to those applicable to the 2027 Notes and have a cap price of approximately $210.32 per share. The 2022 Capped Calls cover, subject to anti-dilution adjustments, 8,100,485 shares of the Company’s common stock, which is the same number of shares of the Company’s common stock initially underlying the 2027 Notes. If, upon conversion of the 2027 Notes, the price of the Company’s common stock is between the strike price and the cap price of the capped calls, the counterparties will deliver shares of the Company’s common stock and/or cash with an aggregate value equal to the difference between the price of the Company’s common stock at the conversion date and the strike price, multiplied by the number of shares of the Company’s common stock related to the capped calls being exercised. The Company paid $127.3 million for the 2022 Capped Calls, which was initially recorded to additional paid-in capital within the consolidated balance sheets as of December 31, 2022.

2024 Convertible Notes Issuance

On November 14, 2017, the Company issued $570.0 million aggregate principal amount of senior convertible notes due on November 15, 2024. The 2024 Notes are senior unsecured obligations of the Company and bear interest at a rate of 1.50% per annum, payable semi-annually in cash on each May 15 and November 15, commencing on May 15, 2018. The net proceeds were $559.4 million after deducting the discounts and offering expenses of $10.6 million. The debt discount is amortized under the effective interest method and recorded as additional interest expense over the life of the 2024 Notes. The effective interest rate on the 2024 Notes is 1.9%.

The 2024 Notes may be convertible into shares of the Company’s common stock under certain circumstances prior to maturity at a conversion rate of 13.621 shares per $1,000 principal amount of the 2024 Notes (7,763,970 shares of the Company's common stock in the aggregate), which represents a conversion price of $73.42 per share, subject to adjustment under certain conditions. Upon conversion, the Company may pay cash, shares of its common stock or a combination of cash and stock, as determined by the Company at its discretion.

The holders of the 2024 Notes may convert their 2024 Notes at their option only in the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2017, if the last reported sale price per share of common stock exceeds 130% of the conversion price for each of at least 20 trading days during the 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; (2) during the five consecutive business days immediately after any five consecutive trading day period (the “measurement period”) in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company's common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company's common stock, as described in the indenture agreement; and (4) at any time from, and including, May 15, 2024 until the close of business on the scheduled trading day immediately before the maturity date.

The 2024 Notes are not redeemable by the Company prior to the maturity date. Holders of the 2024 Notes, however, have the right to require the Company to repurchase for cash all or a portion of their notes at 100% of its respective principal amount, plus any accrued and unpaid interest, upon the occurrence of a fundamental change as defined in the indenture agreement for the 2024 Notes. The 2024 Notes contain customary covenants and events of default, occurrence of which permits the holders to accelerate all outstanding obligations, including principal and interest.

2017 Capped Call Transactions

In connection with the issuance of the 2024 Notes, the Company entered into privately negotiated capped call transactions with counterparties intended to minimize the impact of potential dilution upon conversion of the 2024 Notes (the “2017 Capped Calls”). The 2017 Capped Calls have an initial strike price of approximately $73.42 per share, which corresponds to the initial conversion price of the 2024 Notes and is subject to anti-dilution adjustments generally similar to those applicable to the 2024 Notes, and have a cap price of approximately $104.88 per share. The 2017 Capped Calls initially covered, subject to anti-dilution adjustments, 7,763,970 shares of the Company’s common stock, which is the same number of shares of the Company’s common stock initially underlying the 2024 Notes. If, upon conversion of the 2024 Notes, the price of the Company’s common stock is between the strike price and the cap price of the capped calls, the counterparties will deliver shares of the Company’s common stock and/or cash with an aggregate value equal to the difference between the price of the Company’s common stock at the conversion date and the strike price, multiplied by the number of shares of the Company’s common stock related to the capped calls being exercised. The Company paid $50.9 million for the 2017 Capped Calls, which was initially recorded to additional paid-in capital within the consolidated balance sheets as of December 31, 2017.

2024 Notes Repurchase and Exchange

In connection with the issuance of the 2027 Notes, on September 14, 2022, the Company entered into separate, privately negotiated transactions to repurchase a portion of the outstanding 2024 Notes (the “2024 Notes Repurchase”). The holders exchanged $150.6 million in aggregate principal value of 2024 Notes held by them for an aggregate payment of $248.6 million for full settlement of the principal value and accrued interest on such date. The repurchase was not pursuant to the conversion privileges included in the terms of the debt at issuance and therefore was accounted for as a debt extinguishment. The Company accounted for the debt extinguishment by recognizing the difference between the reacquisition price of the debt and the net carrying amount of the extinguished debt as loss on debt extinguishment. Accordingly, on the repurchase date, the Company: (i) reduced the carrying value of repurchased 2024 Notes by $149.3 million, (ii) eliminated accrued interest of $0.8 million, and (iii) recorded $98.5 million of debt extinguishment expense which was included in the loss on debt extinguishment within the consolidated statements of operations and comprehensive loss for the year ended December 31, 2022.

On March 2, 2023, the Company entered into separate, privately negotiated exchange agreements with certain holders of the outstanding 2024 Notes (the “Exchange Agreements”). The Exchange Agreements resulted in an exchange of $313.5 million in aggregate principal value of the 2024 Notes for shares of the Company’s common stock (the “2024 Notes Exchange”), which closed on March 7, 2023 (the “Exchange Date”). In connection with the 2024 Notes Exchange, the Company issued approximately 4.5 million shares of the Company's common stock representing an agreed upon contractual exchange rate under each of the Exchange Agreements. The fair value of these shares issued was approximately $693.4 million. The Company also incurred approximately $6.9 million in third-party debt conversion costs. The exchange was not pursuant to the conversion privileges included in the terms of the debt at issuance and therefore was accounted for as a debt extinguishment.

Accordingly, on the Exchange Date, the Company: (i) reduced the carrying value of the 2024 Notes by $311.5 million, (ii) eliminated accrued interest of $1.5 million, and (iii) recorded a loss on debt extinguishment of $387.3 million, inclusive of the $6.9 million in third-party debt conversion costs, which is included in the consolidated statements of operations and comprehensive loss for the year ended December 31, 2023. The outstanding principal balance of the 2024 Notes as of December 31, 2023 is approximately $105.8 million, which is convertible into approximately 1.4 million shares of Company common stock.

2017 Capped Calls Partial Settlements

As a result of the 2024 Notes Exchange and the 2024 Notes Repurchase, in March 2023 and September 2022, respectively, the Company entered into agreements with the 2017 Capped Calls counterparties to terminate a portion of the 2017 Capped Calls in a notional amount corresponding to the principal amount of the 2024 Notes exchanged and repurchased and received $80.6 million and $26.3 million, respectively, in cash from the counterparties, which was initially recorded to additional paid-in capital within the consolidated balance sheets as of December 31, 2023 and 2022, respectively.

Termination of 2019 Term Loan

On September 16, 2022, using proceeds received from the issuance of the 2027 Notes described above, the Company prepaid in full all of its amounts outstanding with respect to the December 2019 term loan with Biopharma Credit PLC and Biopharma Credit Investments V (Master) LP (the “December 2019 Term Loan”) and repaid in full all obligations due. The aggregate payoff amount was approximately $585.5 million, which includes $550.0 million of principal, additional loan consideration and premiums of $25.4 million, and accrued interest of $10.1 million through the repayment date. The loss on debt extinguishment was $26.9 million, and is

included in the loss on debt extinguishment in the consolidated statements of operations and comprehensive loss for the year ended December 31, 2022.

Derivatives

Embedded derivatives are required to be separated from the host contract and accounted for as a derivative instrument if the economic characteristics and risk of the embedded derivative are not clearly and closely related to the economic characteristics and risks of the host contract and if a separate instrument with the same terms as the embedded derivative would be a derivative instrument subject to the scope of ASC 815. ASC 815 includes a scope exception for instruments issued by a reporting entity that are both (1) indexed to the reporting entity’s own stock and (2) classified in stockholders’ equity in the reporting entity’s statement of financial position.

All of the features of the 2027 Notes were evaluated to determine if separate accounting as a derivative instrument was required. The conversion feature in the 2027 Notes is indexed solely in the Company's common stock and since the Company retains the option to settle these notes in shares, the conversion feature qualified for a “scope exception” from treatment as a derivative since the conversion feature qualifies as “fixed for fixed”, meaning the settlement is equal to the difference between a fixed monetary amount of convertible notes and the fair value of a fixed number of the Company’s shares, and therefore, the Company did not separately account for it as a derivative. Other features of the notes, such as rights under certain default events, were not considered clearly and closely related to the economic characteristics and risks of the underlying debt host instrument, however, the fair value of these features were determined to be immaterial.

The capped calls are indexed solely to the Company’s common stock and classified in stockholders’ equity since the Company retains the right to receive shares if there is an exercise of the capped call options. The premiums paid for the capped call options, equal to their fair value at inception, were recorded as a reduction to additional paid-in capital.

Total Debt Obligations

As of December 31, 2023 and 2022, the Company recorded approximately $1,132.5 million and $1,544.3 million as long-term debt on the consolidated balance sheets. The Company reclassified the balance of $105.5 million of 2024 Notes from long-term debt to current liabilities on its consolidated balance sheets as of December 31, 2023 as the 2024 Notes mature in less than twelve months. All debt as of December 31, 2022 was long-term in nature.

The following table summarizes the Company’s debt facilities for the periods indicated:


	As of December 31,
	2023			2022
	(in thousands)
Principal amount of the 2024 Notes	$	105,847		$	419,371
Principal amount of the 2027 Notes		1,150,000			1,150,000
Unamortized discount - debt issuance costs of 2024 Notes		(364	)		(3,059	)
Unamortized discount - debt issuance costs of 2027 Notes		(17,485	)		(22,020	)
Net carrying value of the convertible notes		1,237,998			1,544,292

Fair value of 2024 Notes	$	144,833		$	765,046
Fair value of 2027 Notes		1,172,276			1,308,482
Total fair value of debt facilities	$	1,317,109		$	2,073,528

For the years ended December 31, 2023, 2022 and 2021, the Company recorded $22.0 million, $53.2 million and $63.5 million of interest expense, respectively. Total interest expense for the years ended December 31, 2023, 2022 and 2021 is inclusive of $5.2 million, $7.5 million and $7.6 million of amortization of debt discounts, respectively. The fair values of the 2027 Notes and 2024 Notes are based on open market trades and are classified as Level 1 in the fair value hierarchy.

The following table summarizes the total principal and contractual interest payments due under the Company’s debt arrangements:


	As of December 31, 2023
	Principal		Interest		Total Payments
	(in thousands)
2024	$	105,847	$	15,963	$	121,810
2025		—		14,375		14,375
2026		—		14,375		14,375
2027		1,150,000		14,375		1,164,375
Total payments	$	1,255,847	$	59,088	$	1,314,935

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

PRODUCT REVENUES, NET, ACCOUNTS RECEIVABLE,NET AND RESERVES FOR PRODUCT REVENUES (Tables)

12 Months Ended

Dec. 31, 2023

Receivables, Net, Current [Abstract]

Summary of Product Revenues

Net product revenues, which includes revenues associated with EXONDYS 51, AMONDYS 45 and VYONDYS 53 (collectively, the “PMO Products”) and ELEVIDYS consisted of the following:


	For the Year Ended December 31,
	2023		2022
	(in thousands)
PMO Products
United States	$	797,944	$	747,101
Rest of World		146,576		96,668
Total PMO product revenues, net	$	944,520	$	843,769
ELEVIDYS
United States		200,356		—
Total ELEVIDYS product revenues, net	$	200,356	$	—
Total product revenues, net	$	1,144,876	$	843,769

Schedule of Product revenue Concentration risks

The following table summarizes the Company's net product revenues, by customer, for those customers that exceeded 10% for the periods indicated:


	For the Year Ended December 31,
	2023			2022			2021
Product revenues, net
Customer 1		41	%		48	%		48	%
Customer 2		26	%		33	%		39	%
Customer 3	*			*				10	%

* Customer did not exceed 10% of the Company's net product revenues within the applicable year.

Summary of Change in Reserves for Discounts and Allowances

The following table summarizes an analysis of the change in reserves for discounts and allowances for the periods indicated:


	Chargebacks			Rebates			Prompt Pay			Other Accruals			Total
	(in thousands)
Balance, as of December 31, 2021	$	799		$	60,506		$	2,798		$	6,363		$	70,466
Provision		12,446			108,514			12,904			47,654			181,518
Adjustments relating to prior year		—			(5,679	)		—			30			(5,649	)
Payments/credits		(12,828	)		(95,848	)		(12,359	)		(30,602	)		(151,637	)
Balance, as of December 31, 2022	$	417		$	67,493		$	3,343		$	23,445		$	94,698
Provision		44,191			129,724			15,067			69,664			258,646
Adjustments relating to prior year		536			(5,103	)		—			—			(4,567	)
Payments/credits		(17,658	)		(93,920	)		(14,579	)		(57,848	)		(184,005	)
Balance, as of December 31, 2023	$	27,486		$	98,194		$	3,831		$	35,261		$	164,772

Summary of Total Reserves Included in Consolidated Balance Sheets

The following table summarizes the total reserves above included in the Company’s consolidated balance sheets for the periods indicated:


	As of December 31,
	2023		2022
	(in thousands)
Reduction to accounts receivable, net	$	64,697	$	25,914
Component of accrued expenses		100,075		68,784
Total reserves	$	164,772	$	94,698