Amylyx Pharmaceuticals (AMLX) 10-Q 9 May 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2024	Apr. 30, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Trading Symbol	AMLX
Entity Registrant Name	Amylyx Pharmaceuticals, Inc.
Entity Central Index Key	0001658551
Current Fiscal Year End Date	--12-31
Entity File Number	001-41199
Entity Tax Identification Number	46-4600503
Entity Address, Address Line One	43 Thorndike St.
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02141
City Area Code	617
Local Phone Number	682-0917
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		68,005,749
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 170,552	$ 170,201
Short-term investments	202,741	201,161
Accounts receivable, net	20,351	40,050
Inventories		38,323
Prepaid expenses and other current assets	16,890	14,931
Total current assets	410,534	464,666
Property and equipment, net	2,459	2,686
Restricted cash equivalents	719	719
Operating lease right-of-use assets	3,252	3,725
Long-term inventories		44,957
Other assets	493	701
Total assets	417,457	517,454
Current liabilities:
Accounts payable	21,453	22,061
Accrued expenses	67,874	57,724
Operating lease liabilities, current portion	2,312	2,257
Total current liabilities	91,639	82,042
Operating lease liabilities, net of current portion	1,382	1,980
Total liabilities	93,021	84,022
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized
Common stock, $0.0001 par value; 300,000,000 shares authorized; 67,975,587 and 67,707,432 shares issued and outstanding as of March 31, 2024 and December 31, 2023, respectively	7	7
Additional paid-in capital	748,248	738,177
Accumulated deficit	(423,742)	(304,949)
Accumulated other comprehensive (loss) income	(77)	197
Total stockholders' equity	324,436	433,432
Total liabilities and stockholders' equity	$ 417,457	$ 517,454

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Preferred stock par value	$ 0.0001	$ 0.0001
Preferred stock shares authorized	10,000,000	10,000,000
Common stock, stated par value per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares, issued	67,975,587	67,707,432
Common stock, shares, outstanding	67,975,587	67,707,432

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Product revenue, net	$ 88,643	$ 71,428
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	us-gaap:ProductMember	us-gaap:ProductMember
Operating expenses:
Cost of sales	$ 5,945	$ 5,283
Cost of sales - inventory impairment and loss on firm purchase commitments	110,461
Research and development	36,608	24,192
Selling, general and administrative	57,759	44,006
Total operating expenses	210,773	73,481
Loss from operations	(122,130)	(2,053)
Other income, net:
Interest income	4,326	3,718
Other expense, net	(747)	(262)
Total other income, net	3,579	3,456
(Loss) income before income taxes	(118,551)	1,403
Provision (benefit) for income taxes	242	(170)
Net (loss) income	$ (118,793)	$ 1,573
Net (loss) income per share - basic	$ (1.75)	$ 0.02
Net (loss) income per share - diluted	$ (1.75)	$ 0.02
Weighted-average shares used in computing net (loss) income per share-basic	67,854,356	66,717,271
Weighted-average shares used in computing net (loss) income per share-diluted	67,854,356	70,863,665

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (118,793)	$ 1,573
Other comprehensive loss (income)
Foreign currency translation (loss) gain	(158)	79
Net unrealized (loss) gain on available-for-sale securities	(116)	32
Other comprehensive (loss) income	(274)	111
Comprehensive (loss) income	$ (119,067)	$ 1,684

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance, Shares at Dec. 31, 2022		66,512,011
Beginning Balance at Dec. 31, 2022	$ 340,607	$ 7	$ 694,906	$ (86)	$ (354,220)
Issuance of common stock upon exercise of stock options, Shares		451,298
Issuance of common stock upon exercise of stock options	2,777		2,777
Issuance of common stock upon vesting of RSUs		132,294
Stock-based compensation expense	7,580		7,580
Other comprehensive loss	111			111
Net (loss) income	1,573				1,573
Ending Balance, Shares at Mar. 31, 2023		67,095,603
Ending Balance at Mar. 31, 2023	$ 352,648	$ 7	705,263	25	(352,647)
Beginning Balance, Shares at Dec. 31, 2023	67,707,432	67,707,432
Beginning Balance at Dec. 31, 2023	$ 433,432	$ 7	738,177	197	(304,949)
Issuance of common stock upon exercise of stock options, Shares	49,618	49,618
Issuance of common stock upon exercise of stock options	$ 147		147
Issuance of common stock upon vesting of RSUs		218,537
Stock-based compensation expense	9,924		9,924
Other comprehensive loss	(274)			(274)
Net (loss) income	$ (118,793)				(118,793)
Ending Balance, Shares at Mar. 31, 2024	67,975,587	67,975,587
Ending Balance at Mar. 31, 2024	$ 324,436	$ 7	$ 748,248	$ (77)	$ (423,742)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows used in operating activities:
Net (loss) income	$ (118,793)	$ 1,573
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Stock-based compensation expense	9,924	7,501
Depreciation expense	315	204
Accretion of investment discounts, net	(2,582)	(2,903)
Inventory impairment and loss on firm purchase commitments	110,461
Other non-cash items	22
Changes in operating assets and liabilities:
Accounts receivable, net	19,698	(2,249)
Inventories	(9,253)	(13,303)
Interest receivable	117	253
Prepaid expenses and other current assets	(2,104)	(2,882)
Operating lease right-of-use assets	473	436
Other assets	204
Accounts payable	(652)	4,611
Accrued expenses	(7,776)	2,178
Operating lease liabilities	(543)	(491)
Net cash used in operating activities	(489)	(5,072)
Cash flows provided by investing activities:
Purchases of property and equipment	(67)	(250)
Purchases of investments	(73,114)	(9,756)
Proceeds from maturities of short-term investments	74,000	66,000
Net cash provided by investing activities	819	55,994
Cash flows (used in) provided by financing activities:
Follow-on offering costs paid		(136)
Proceeds from exercise of stock options and RSUs vesting	1,446	3,539
Withholding taxes paid on stock-based awards	(1,315)	(2,363)
Net cash provided by financing activities	131	1,040
Effect of exchange rate changes on cash, cash equivalents and restricted cash equivalents	(110)	75
Net increase in cash, cash equivalents and restricted cash equivalents	351	52,037
Cash, cash equivalents and restricted cash equivalents, beginning of period	170,920	63,245
Cash, cash equivalents and restricted cash equivalents, end of period	171,271	115,282
Supplemental disclosure of cash flow information:
Taxes withheld on stock-based awards included in accrued expenses	9	$ 22
Purchases of property and equipment included in accounts payable	63
Income taxes paid	$ 275

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (118,793)	$ 1,573

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 2024
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	During the three months ended March 31, 2024 , no officer or director of the Company (as defined in Rule 16a-1(f)) adopted or terminated a “Rule 10b5-1 trading arrangement” or a “non-Rule 10b5-1 trading arrangement,” as each term is defined in Item 408(a) of Regulation S-K of the Exchange Act.
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Nature of the Business

Nature of the Business	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business	1. Nature of the Business Amylyx Pharmaceuticals, Inc., together with its wholly owned subsidiaries, known as Amylyx or the Company, is a biotechnology company with a mission to end the suffering caused by neurodegenerative diseases. The Company is investigating AMX0035 in diseases where endoplasmic reticulum, or ER, and mitochondrial stress are implicated, including progressive supranuclear palsy, or PSP, and Wolfram syndrome, or WS. The Company dosed the first participant in the HELIOS trial, a Phase 2 trial of AMX0035 for the treatment of WS, in April 2023. The Company dosed the first participant in the ORION trial, a Phase 3 trial of AMX0035 for the treatment of PSP, in December 2023. The Company is also advancing additional drug candidates developed by Amylyx for neurodegenerative diseases including AMX0114, a potent antisense oligonucleotide targeting inhibition of Calpain-2, a key contributor to the axonal (also known as Wallerian) degeneration pathway. Preclinical studies completed to date have shown that AMX0114 achieves potent, dose-dependent, and durable knockdown of CAPN2 mRNA expression and Calpain-2 protein levels in human motor neurons. In preclinical efficacy studies, treatment with AMX0114 reduced extracellular neurofilament light chain levels following neurotoxic insult in induced pluripotent stem cell (iPSC)-derived human motor neurons, and improved survival of iPSC-derived human motor neurons harboring ALS-linked, pathogenic TDP-43 mutations. Neurofilament is a broadly researched biomarker in ALS. The Company plans to file an investigational new drug (IND) application, then initiate a multiple ascending dose clinical trial of AMX0114 in people living with ALS in the second half of 2024. On April 4, 2024, the Company announced it started a process with the U.S. Food and Drug Administration, or the FDA, and Health Canada to voluntarily discontinue the marketing authorizations for RELYVRIO ® /ALBRIOZA ™ (AMX0035) for amyotrophic lateral sclerosis, or ALS, and remove the product from the market in the U.S. and Canada based on topline results from the global Phase 3 PHOENIX trial, which failed to meet its prespecified primary and secondary endpoints. The Company will continue to collect available data on survival and to share learnings from PHOENIX to help inform future ALS research. Amylyx is planning to wind down the Open Label Extension by the end of 2024. Separately, the PHOENIX survival data collection efforts will continue at the encouragement of ALS specialists. Risks and Uncertainties The Company is subject to risks and uncertainties common to companies in the biotechnology industry, including, but not limited to, the outcome of preclinical studies and clinical trials, potential difficulties with or delays in timing with respect to regulatory approval processes, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, ability to secure additional capital to fund operations, and risks associated with the economic challenges caused by economic uncertainty in various global markets caused by geopolitical instability and conflict. The Company and its contractors may experience disruptions in supply of items that are essential for its research and development activities, including, for example, raw materials and bulk drug substances that the Company imports from Europe and Canada used in the manufacturing of AMX0035, and any additional or future product candidates .

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Significant Accounting Policies The Company’s significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2023 and the notes thereto, which are included in the Company’s most recent Annual Report on Form 10-K. Since the date of those consolidated financial statements, there have been no material changes to its significant accounting policies. Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements are unaudited and have been prepared in conformity with accounting principles generally accepted in the U.S., or GAAP, and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. In the opinion of the Company's management, all normal and recurring adjustments necessary for a fair presentation have been reflected. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB. Use of Estimates The preparation of the condensed consolidated financial statements in conformity with GAAP requires the Company’s management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amount of expenses during the reporting period. Actual results could differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies in developing the estimates and assumptions that are used in the preparation of the financial statements. Management must apply significant judgment in this process. Management’s estimation process often may yield a range of potentially reasonable estimates and management must select an amount that falls within that range of reasonable estimates. Estimates are used in the following areas, among others: gross-to-net, or GTN, adjustments; recoverability of inventories; accrued expense and research and development expenses . New Accounting Pronouncements Not Yet Adopted In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvement to Income Tax Disclosures , or ASU 2023-09, to enhance the transparency and decision usefulness of income tax disclosures. ASU 2023-09 is effective for annual periods beginning after December 15, 2024 on a prospective basis. Early adoption and retrospective application is permitted. The Company is currently evaluating the impact of this ASU on its consolidated financial statements and related disclosures. In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , or ASU 2023-09, which requires public entities to disclose information about their reportable segments’ significant expenses on an interim and annual basis. ASU 2023-07 is effective for the Company beginning the year ended May 31, 2025. The Company is currently evaluating the impact of this ASU on its consolidated financial statements and related disclosures.

Product Revenue, Net

Product Revenue, Net	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Product Revenue, Net	3. PRODUCT REVENUE, NET To date, the Company’s only source of product revenue has been from the sales of RELYVRIO, known as ALBRIOZA in Canada. Significant judgment is required in estimating GTN adjustments considering historical experience, payer channel mix (e.g., Medicare or Medicaid), current contract prices under applicable programs, unbilled claims and processing time lags and inventory levels in the distribution channel. The following table reconciles gross product revenue to net product revenue (in thousands): Three Months Ended March 31, 2024 2023 Product revenue, gross $ 113,660 $ 84,553 GTN adjustments ( 25,017 ) ( 13,125 ) Product revenue, net $ 88,643 $ 71,428 The activity and ending reserve balance for GTN adjustments were as follows for the three months ended March 31, 2024 and 2023 (in thousands): Chargebacks and Cash Discounts Medicaid and Medicare Rebates Other Rebates, Returns, Discounts and Adjustments Total Ending balance at December 31, 2023 $ 3,143 $ 4,946 $ 11,073 $ 19,162 Provision related to sales in the current year 4,983 3,504 19,288 27,775 Adjustments related to prior period sales ( 1,696 ) — ( 1,062 ) ( 2,758 ) Credits and payments made ( 5,784 ) ( 2,201 ) ( 5,246 ) ( 13,231 ) Ending balance at March 31, 2024 $ 646 $ 6,249 $ 24,053 $ 30,948 Chargebacks and Cash Discounts Medicaid and Medicare Rebates Other Rebates, Returns, Discounts and Adjustments Total Ending balance at December 31, 2022 $ 648 $ 1,992 $ 1,664 $ 4,304 Provision related to sales in the current year 6,273 3,640 3,448 13,361 Adjustments related to prior period sales — ( 236 ) — ( 236 ) Credits and payments made ( 2,907 ) ( 718 ) ( 2,422 ) ( 6,047 ) Ending balance at March 31, 2023 $ 4,014 $ 4,678 $ 2,690 $ 11,382 Included in the ending reserve balance for GTN adjustments are chargebacks resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to customers who directly purchase the product from the Company, discounts to customers for prompt payment and estimates for product returns. Chargebacks, discounts and returns are recorded as reductions of accounts receivable, net on the condensed consolidated balance sheets. In addition, included in the ending reserve balance for GTN adjustments are Medicaid and Medicare rebates, other rebates for obligations under voluntary patient assistance programs, and accrued fees payable to customers. Medicaid and Medicare rebates, other rebates and fees are recorded as a component of accrued expenses on the condensed consolidated balance sheets. In April 2024, the Company announced it started a process with the FDA and Health Canada to voluntarily discontinue the marketing authorizations for RELYVRIO ® /ALBRIOZA ™ and remove the product from the market in the U.S. and Canada based on topline results from the Phase 3 PHOENIX trial .

Short-Term Investments

Short-Term Investments	3 Months Ended
	Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract]
Short-Term Investments	4. SHORT-TERM INVESTMENTS The Company has classified all of its marketable securities at March 31, 2024 as “available-for-sale”. The Company records available-for-sale securities at fair value, with the unrealized gains and losses included as a separate component of other accumulated comprehensive income (loss). There were no realized gains or losses recognized during the three months ended March 31, 2024 and 2023. The Company adjusts the cost of available-for-sale debt securities for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in interest income. The cost of securities sold is based on the specific identification method. The Company includes interest and dividends on securities classified as available-for-sale in interest income. Accrued interest receivable relating to the Company's available-for-sale securities is presented within prepaid expenses and other current assets in the accompanying condensed consolidated balance sheets, and amounted to $ 0.3 million and $ 0.5 million at March 31, 2024 and December 31, 2023, respectively. The following is a summary of available-for-sale securities with unrealized losses for less than 12 months as of March 31, 2024 and December 31, 2023 (in thousands): March 31, 2024 December 31, 2023 Fair Value Unrealized Losses Fair Value Unrealized Losses Treasury bills $ 182,832 $ ( 52 ) $ — $ — U.S. agency bonds — — 4,996 ( 3 ) Total available-for-sale securities in an unrealized loss position $ 182,832 $ ( 52 ) $ 4,996 $ ( 3 ) At March 31, 2024, the Company's security portfolio consisted of 9 securities related to investments in debt securities available-for-sale, of which 8 se curities were in an unrealized loss position. There were no securities in an unrealized loss position for greater than 12 months as of March 31, 2024. The contractual terms of these investments do not permit the issuer to settle the securities at a price less than the amortized cost bases of the investments. The Company does not intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases. The Company did not record an allowance for credit losses as of March 31, 2024. Short-term investments, which are classified as available-for-sale, consisted of the following (in thousands): Balance at March 31, 2024: Amortized Unrealized Unrealized Fair Treasury bills $ 202,793 $ — $ ( 52 ) $ 202,741 Total short-term investments $ 202,793 $ — $ ( 52 ) $ 202,741 Balance at December 31, 2023: Amortized Unrealized Unrealized Fair Treasury bills $ 196,098 $ 67 $ — $ 196,165 U.S. agency bonds 4,999 — ( 3 ) 4,996 Total short-term investments $ 201,097 $ 67 $ ( 3 ) $ 201,161

Inventories

Inventories	3 Months Ended
	Mar. 31, 2024
Inventory Disclosure [Abstract]
Inventories	5. INVENTORIES Inventories consisted of the following (in thousands): March 31, 2024 December 31, 2023 Raw materials $ — $ 53,144 Work in process — 18,945 Finished goods — 11,191 Total inventories $ — $ 83,280 On April 4, 2024, the Company announced it started a process with the FDA and Health Canada to voluntarily discontinue the marketing authorizations for RELYVRIO ® /ALBRIOZA™ and remove the product from the market in the U.S. and Canada based on topline results from the global Phase 3 PHOENIX trial. As a result, the Company recorded approximately $ 92.5 million of charges associated with the write-down of inventory for the three months ended March 31, 2024. Inventory write-downs for the three months ended March 31, 2023 were immaterial.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2024
Payables and Accruals [Abstract]
Accrued Expenses	6. Accrued Expenses Accrued expenses consisted of the following (in thousands): March 31, 2024 December 31, 2023 Accrued external research and development $ 11,029 $ 12,625 Accrued benefits and incentive compensation 6,204 16,790 Accrued manufacturing 4,489 1,652 Accrued consulting and other professional fees 8,693 6,506 Accrued rebates and co-pay assistance 18,636 16,063 Accrued royalties — 3,111 Accrued loss on future purchase commitments 17,928 — Other accrued expenses 895 977 Total accrued expenses $ 67,874 $ 57,724

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	7 . FAIR VALUE MEASUREMENTS The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands): March 31, 2024 Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 78,731 $ — $ — $ 78,731 Short-term investments: Treasury bills 202,741 — — 202,741 Total short-term investments 202,741 — — 202,741 Restricted cash equivalents 719 — — 719 Total financial assets $ 282,191 $ — $ — $ 282,191 December 31, 2023 Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 76,710 $ — $ — $ 76,710 Short-term investments: Treasury bills 196,165 — — 196,165 U.S. agency bonds — 4,996 — 4,996 Total short-term investments 196,165 4,996 — 201,161 Restricted cash equivalents 719 — — 719 Total financial assets $ 273,594 $ 4,996 $ — $ 278,590 The Company classifies its money market funds, treasury notes and treasury bills as Level 1 assets under the fair value hierarchy, as these assets have been valued using quoted market prices for identical assets in active markets without any valuation adjustment. The Company classifies its commercial paper, corporate debt securities, and agency bonds as Level 2 assets under the fair value hierarchy, as these assets have been valued using information obtained through a third-party pricing service at each balance sheet date, using observable market inputs that may include trade information, broker or dealer quotes, bids, offers, or a combination of these data sources .

Stock Option and Grant Plan

Stock Option and Grant Plan	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Stock Option and Grant Plan	8. Stock Option and Grant Plan Stock Incentive Plan General Option Information A summary of option activity for the three months ended March 31, 2024, is as follows: Number of Weighted- Weighted- Aggregate Outstanding at December 31, 2023 9,823,248 $ 18.39 7.9 $ 27,639 Granted 1,357,981 $ 16.76 Exercised ( 49,618 ) $ 2.96 $ 653 Cancelled or forfeited ( 356,109 ) $ 21.88 Outstanding at March 31, 2024 10,775,502 $ 18.14 7.9 $ 689 Options exercisable as of March 31, 2024 4,739,300 $ 14.87 7.0 $ 689 Options unvested as of March 31, 2024 6,036,202 $ 20.70 8.6 $ — Weighted average grant-date fair value of options granted during the period $ 11.00 The aggregate intrinsic value of options exercised during the three months ended March 31, 2024 and 2023 was $ 0.7 million and $ 11.7 million , respectively. The total fair value of stock options vested during the three months ended March 31, 2024 and 2023 was $ 14.9 million and $ 14.7 million , respectively. Restricted Stock Unit Activity A summary of restricted stock unit activity for the three months ended March 31, 2024, is as follows: Number of Shares Weighted Average Grant Date Fair Value Nonvested as of December 31, 2023 1,112,542 $ 24.80 Granted 1,242,207 $ 17.42 Vested ( 231,437 ) $ 25.39 Forfeited ( 67,972 ) $ 24.90 Nonvested as of March 31, 2024 2,055,340 $ 20.27 Summary of Stock-Based Compensation Expense Stock-based compensation expense for the three months ended March 31, 2024 and 2023, is as follows (in thousands): Three Months Ended March 31, 2024 2023 Research and development $ 2,712 $ 1,891 Selling, general and administrative 7,212 5,610 Total stock-based compensation expense $ 9,924 $ 7,501 The following table summarizes unrecognized stock-based compensation expense as of March 31, 2024, by type of awards (in thousands), and the weighted-average period over which that expense is expected to be recognized (in years). The total unrecognized stock-based compensation expense will be adjusted for actual forfeitures as they occur. March 31, 2024 Unrecognized Expense Weighted-average Recognition Period Stock options $ 80,901 2.63 Restricted stock units $ 39,510 3.30

Net (Loss) Income Per Share

Net (Loss) Income Per Share	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Net (Loss) Income Per Share	9. NET (LOSS) INCOME PER SHARE Net (Loss) Income per Share Basic earnings per share is computed by dividing net income (loss) by the weighted average number of common shares outstanding during the period. Diluted earnings per share is calculated based on the combined weighted average number of common shares and potentially dilutive shares, which include the assumed exercise of employee stock options and unvested restricted stock units. In computing diluted earnings per share, the Company utilizes the treasury stock method. A summary of the numerator and denominators used in the computation of earnings per share follows (in thousands, except share and per share data): Three Months Ended March 31, 2024 2023 Numerator: Net (loss) income $ ( 118,793 ) $ 1,573 Denominator: Weighted-average shares used to compute basic net (loss) income per share 67,854,356 66,717,271 Dilutive effect of employee stock options and restricted stock units — 4,146,394 Weighted-average shares used to compute diluted net (loss) income per share 67,854,356 70,863,665 Net (loss) income per share Basic $ ( 1.75 ) $ 0.02 Diluted $ ( 1.75 ) $ 0.02 Because the Company reported a net loss attributable to common stockholders for the three months ended March 31, 2024, basic and diluted net loss per share attributable to common stockholders were the same. All stock options and restricted stock units were excluded from the computation of diluted weighted-average shares outstanding because such securities would have an antidilutive impact for the three months ended March 31, 2024 . The following stock options and restricted stock units outstanding at each period end have been excluded from the calculation of diluted net income (loss) per share because their inclusion would have been antidilutive: Three Months Ended March 31, 2024 2023 Options to purchase common stock 10,775,502 368,503 Restricted stock units 2,055,340 4,509 Total excluded common stock equivalents 12,830,842 373,012

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
Related Party Transactions	10. Related party transactions Supplier Agreements In the ordinary course of business, the Company may purchase materials or supplies or services from entities that are associated with a party that meets the criteria of a related party of the Company. These transactions are reviewed quarterly and to date have not been material to the Company’s condensed consolidated financial statements.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies Lease Commitments The Company has two operating lease agreements for its office space. Letter of Credit Restricted cash equivalents consist of $ 0.2 million of cash serving as collateral for a letter of credit issued for the Company’s office space, and $ 0.5 million as collateral for a corporate credit card program. As of March 31, 2024 and December 31, 2023, the Company’s restricted cash equivalents balance was $ 0.7 million on its condensed consolidated balance sheets. Legal Proceedings On February 9, 2024, a putative class action lawsuit was filed in the U.S. District Court for the Southern District of New York against the Company and certain of its current and former officers ( Shih v. Amylyx Pharmaceuticals, Inc., et al. , Case Number 1:24-CV-00988, or the Shih Complaint. The Shih Complaint asserts a claim against all defendants for alleged violations of Section 10(b) of the Exchange Act and Rule 10b-5 promulgated thereunder and a claim under Section 20(a) against certain current and former officers as alleged controlling persons. The Shih Complaint alleges that defendants made materially false and misleading statements related to the commercial results and prospects for RELYVRIO. The Shih Complaint seeks unspecified damages, interest, costs and attorneys’ fees, and other unspecified relief that the court deems appropriate. The Company intends to defend against the Shih Complaint vigorously. At this time, an estimate of the impact, if any, of these claims cannot be made. Royalty Payments Between August 2016 and February 2019, the Company entered into grant agreements with the ALS Association, ALS Finding a Cure Foundation, Alzheimer’s Drug Discovery Foundation, Alzheimer’s Association and Cure Alzheimer’s Fund, or Grantors. Under the terms of the agreements, the Company was granted, in aggregate, $ 4.3 million. These grants were provided to the Company for the purpose of furthering the research and development of AMX0035 as a therapeutic benefit for ALS and Alzheimer’s disease. Under the terms of the arrangements, the Company would receive a tranche of funds as it completed certain milestones. Pursuant to the terms of the grant agreements, the Company has certain payment obligations that are contingent upon future events such as the achievement of commercialization or the receipt of proceeds from a revenue generating transaction resulting from the projects for which the grants are used for. Pursuant to the terms of the respective grant agreements among the Company, ALS Association and ALS Finding a Cure, the Company will be required to make royalty payments to each Grantor in the total amount equal to 150 % of the grant received. The royalty payments will be achieved through a combination of the following payment methods: (i) an annual installment payment of 3 % of net sales of any products developed under the project for which the grant was used for and (ii) 3 % of cash proceeds resulting from revenue generating transaction under the project for which the grants are used for. During the three months ended March 31, 2024 , the Company did no t record any royalty expense. During the three months ended March 31, 2023, the Company recorded $ 2.5 million in royalty expense, which is included in cost of sales in the condensed consolidated financial statements. As of March 31, 2024 , no further royalties remain to be accrued under the grant agreements with the ALS Association and ALS Finding a Cure Foundation. Under the terms of the respective grant agreements among the Company, Alzheimer’s Drug Discovery Foundation, the Alzheimer’s Association, and Cure Alzheimer’s Fund, the Company will make royalty payments up to the maximum amount of $ 15.0 million to each Grantor (or $ 45.0 million in aggregate). The royalty payment will be made through a combination of the following payment methods: (i) 4 % of annual net sales of any product commercialized from the project for which the grant was used for and directly related to the treatment of the Alzheimer’s disease and (ii) 15 % of all royalties and cash proceeds resulting from revenue generating transactions associated with the projects for which the grants were used for under the grant agreements. As the conditions that would trigger royalty payments under the agreements have not occurred, no amounts have been recorded in the condensed consolidated financial statements for the three months ended March 31, 2024 and 2023. Purchase Commitments The Company enters into agreements in the normal course of business with contract manufacturing organizations for raw material purchases and manufacturing services. As disclosed in Note 18 Commitments and Contingencies in the Company's Annual Report on Form 10-K, as of December 31, 2023, the Company had committed approximately $ 195.0 million under these agreements related to raw material purchases and manufacturing services, which were expected to be paid through 2028. While these commitments are estimates and are subject to changes based on the outcomes of ongoing negotiations with the contract manufacturing organizations, as of March 31, 2024, the Company had estimated approximately $ 35.1 million of commitments under these agreements related to raw material purchases and manufacturing services, which are expected to be paid through 2025. The actual obligations may differ from these estimates, and such differences will be reflected in the Company's financial statements in future periods as they become known. The Company recognized a loss on purchase commitments of $ 17.9 million for the three months ended March 31, 2024 , which was recorded to cost of sales on the condensed consolidated statement of operations and as part of accrued expenses on the condensed consolidated balance sheet. The purchase commitment loss is based on an estimate of future commitments related to supply agreements with third party vendors for which the Company does not expect to have related sales.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2024
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events In April 2024, the Company announced that it has started a process with the FDA and Health Canada to voluntarily discontinue the marketing authorizations for RELYVRIO ® /ALBRIOZA ™ (sodium phenylbutyrate and taurursodiol [also known as ursodoxicoltaurine]; also known as AMX0035) for the treatment of ALS and remove the product from the market in the U.S. and Canada. As of April 4, 2024, RELYVRIO/ALBRIOZA was no longer available for new patients. The Company also announced a restructuring plan designed to focus the Company’s resources on key clinical and preclinical programs, or the Restructuring Plan. The Restructuring Plan includes a reduction in force which is expected to reduce the Company’s workforce by approximately 70 % and a decrease in external financial commitments outside of its priority areas. The Company expects to substantially complete the Restructuring Plan by the end of the third quarter of 2024. As part of this Restructuring Plan, the Company expects to incur severance and severance-related charges of approximately $ 19.1 million . The Company may also incur other charges or cash expenditures not currently contemplated or that cannot be currently estimated due to events that may occur as a result of, or associated with, the Restructuring Plan. As the Company will no longer sell RELYVRIO or ALBRIOZA, the Company recorded approximately $ 92.5 million of charges associated with the write-down of inventory for the three months ended March 31, 2024. In addition, the Company recognized a loss on purchase commitments of $ 17.9 million for the three months ended March 31, 2024 , which is based on an estimate of future commitments related to supply agreements with third party vendors for which the Company does not expect to have related sales.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements are unaudited and have been prepared in conformity with accounting principles generally accepted in the U.S., or GAAP, and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. In the opinion of the Company's management, all normal and recurring adjustments necessary for a fair presentation have been reflected. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with GAAP requires the Company’s management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amount of expenses during the reporting period. Actual results could differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies in developing the estimates and assumptions that are used in the preparation of the financial statements. Management must apply significant judgment in this process. Management’s estimation process often may yield a range of potentially reasonable estimates and management must select an amount that falls within that range of reasonable estimates. Estimates are used in the following areas, among others: gross-to-net, or GTN, adjustments; recoverability of inventories; accrued expense and research and development expenses
New Accounting Pronouncements Not Yet Adopted	New Accounting Pronouncements Not Yet Adopted In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvement to Income Tax Disclosures , or ASU 2023-09, to enhance the transparency and decision usefulness of income tax disclosures. ASU 2023-09 is effective for annual periods beginning after December 15, 2024 on a prospective basis. Early adoption and retrospective application is permitted. The Company is currently evaluating the impact of this ASU on its consolidated financial statements and related disclosures. In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , or ASU 2023-09, which requires public entities to disclose information about their reportable segments’ significant expenses on an interim and annual basis. ASU 2023-07 is effective for the Company beginning the year ended May 31, 2025. The Company is currently evaluating the impact of this ASU on its consolidated financial statements and related disclosures.

Product Revenue, Net (Tables)

Product Revenue, Net (Tables)	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Summary of Gross Product Revenue to Net Product Revenue	The following table reconciles gross product revenue to net product revenue (in thousands): Three Months Ended March 31, 2024 2023 Product revenue, gross $ 113,660 $ 84,553 GTN adjustments ( 25,017 ) ( 13,125 ) Product revenue, net $ 88,643 $ 71,428
Schedule of Activity and Ending Reserve Balance for GTN Adjustments	The activity and ending reserve balance for GTN adjustments were as follows for the three months ended March 31, 2024 and 2023 (in thousands): Chargebacks and Cash Discounts Medicaid and Medicare Rebates Other Rebates, Returns, Discounts and Adjustments Total Ending balance at December 31, 2023 $ 3,143 $ 4,946 $ 11,073 $ 19,162 Provision related to sales in the current year 4,983 3,504 19,288 27,775 Adjustments related to prior period sales ( 1,696 ) — ( 1,062 ) ( 2,758 ) Credits and payments made ( 5,784 ) ( 2,201 ) ( 5,246 ) ( 13,231 ) Ending balance at March 31, 2024 $ 646 $ 6,249 $ 24,053 $ 30,948 Chargebacks and Cash Discounts Medicaid and Medicare Rebates Other Rebates, Returns, Discounts and Adjustments Total Ending balance at December 31, 2022 $ 648 $ 1,992 $ 1,664 $ 4,304 Provision related to sales in the current year 6,273 3,640 3,448 13,361 Adjustments related to prior period sales — ( 236 ) — ( 236 ) Credits and payments made ( 2,907 ) ( 718 ) ( 2,422 ) ( 6,047 ) Ending balance at March 31, 2023 $ 4,014 $ 4,678 $ 2,690 $ 11,382

Short-Term Investments (Tables)

Short-Term Investments (Tables)	3 Months Ended
	Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-sale Securities with Unrealized Losses for Less Than 12 Months	The following is a summary of available-for-sale securities with unrealized losses for less than 12 months as of March 31, 2024 and December 31, 2023 (in thousands): March 31, 2024 December 31, 2023 Fair Value Unrealized Losses Fair Value Unrealized Losses Treasury bills $ 182,832 $ ( 52 ) $ — $ — U.S. agency bonds — — 4,996 ( 3 ) Total available-for-sale securities in an unrealized loss position $ 182,832 $ ( 52 ) $ 4,996 $ ( 3 )
Schedule of Short-term Investments Classified as Available-for-sale	Short-term investments, which are classified as available-for-sale, consisted of the following (in thousands): Balance at March 31, 2024: Amortized Unrealized Unrealized Fair Treasury bills $ 202,793 $ — $ ( 52 ) $ 202,741 Total short-term investments $ 202,793 $ — $ ( 52 ) $ 202,741 Balance at December 31, 2023: Amortized Unrealized Unrealized Fair Treasury bills $ 196,098 $ 67 $ — $ 196,165 U.S. agency bonds 4,999 — ( 3 ) 4,996 Total short-term investments $ 201,097 $ 67 $ ( 3 ) $ 201,161

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2024
Inventory Disclosure [Abstract]
Summary of Inventories	Inventories consisted of the following (in thousands): March 31, 2024 December 31, 2023 Raw materials $ — $ 53,144 Work in process — 18,945 Finished goods — 11,191 Total inventories $ — $ 83,280

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2024
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following (in thousands): March 31, 2024 December 31, 2023 Accrued external research and development $ 11,029 $ 12,625 Accrued benefits and incentive compensation 6,204 16,790 Accrued manufacturing 4,489 1,652 Accrued consulting and other professional fees 8,693 6,506 Accrued rebates and co-pay assistance 18,636 16,063 Accrued royalties — 3,111 Accrued loss on future purchase commitments 17,928 — Other accrued expenses 895 977 Total accrued expenses $ 67,874 $ 57,724

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands): March 31, 2024 Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 78,731 $ — $ — $ 78,731 Short-term investments: Treasury bills 202,741 — — 202,741 Total short-term investments 202,741 — — 202,741 Restricted cash equivalents 719 — — 719 Total financial assets $ 282,191 $ — $ — $ 282,191 December 31, 2023 Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 76,710 $ — $ — $ 76,710 Short-term investments: Treasury bills 196,165 — — 196,165 U.S. agency bonds — 4,996 — 4,996 Total short-term investments 196,165 4,996 — 201,161 Restricted cash equivalents 719 — — 719 Total financial assets $ 273,594 $ 4,996 $ — $ 278,590

Stock Option and Grant Plan (Ta

Stock Option and Grant Plan (Tables)	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Summary of Stock Option Activity	A summary of option activity for the three months ended March 31, 2024, is as follows: Number of Weighted- Weighted- Aggregate Outstanding at December 31, 2023 9,823,248 $ 18.39 7.9 $ 27,639 Granted 1,357,981 $ 16.76 Exercised ( 49,618 ) $ 2.96 $ 653 Cancelled or forfeited ( 356,109 ) $ 21.88 Outstanding at March 31, 2024 10,775,502 $ 18.14 7.9 $ 689 Options exercisable as of March 31, 2024 4,739,300 $ 14.87 7.0 $ 689 Options unvested as of March 31, 2024 6,036,202 $ 20.70 8.6 $ — Weighted average grant-date fair value of options granted during the period $ 11.00
Summary of Restricted Stock Unit Activity	A summary of restricted stock unit activity for the three months ended March 31, 2024, is as follows: Number of Shares Weighted Average Grant Date Fair Value Nonvested as of December 31, 2023 1,112,542 $ 24.80 Granted 1,242,207 $ 17.42 Vested ( 231,437 ) $ 25.39 Forfeited ( 67,972 ) $ 24.90 Nonvested as of March 31, 2024 2,055,340 $ 20.27
Summary of Stock-Based Compensation Expense	Stock-based compensation expense for the three months ended March 31, 2024 and 2023, is as follows (in thousands): Three Months Ended March 31, 2024 2023 Research and development $ 2,712 $ 1,891 Selling, general and administrative 7,212 5,610 Total stock-based compensation expense $ 9,924 $ 7,501
Summary of Unrecognized Stock-Based Compensation Expense and Weighted-Average Recognition Period	The following table summarizes unrecognized stock-based compensation expense as of March 31, 2024, by type of awards (in thousands), and the weighted-average period over which that expense is expected to be recognized (in years). The total unrecognized stock-based compensation expense will be adjusted for actual forfeitures as they occur. March 31, 2024 Unrecognized Expense Weighted-average Recognition Period Stock options $ 80,901 2.63 Restricted stock units $ 39,510 3.30

Net (Loss) Income Per Share (Ta

Net (Loss) Income Per Share (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Summary of the Numerator and Denominators Used in Computation of Earnings Per Share	A summary of the numerator and denominators used in the computation of earnings per share follows (in thousands, except share and per share data): Three Months Ended March 31, 2024 2023 Numerator: Net (loss) income $ ( 118,793 ) $ 1,573 Denominator: Weighted-average shares used to compute basic net (loss) income per share 67,854,356 66,717,271 Dilutive effect of employee stock options and restricted stock units — 4,146,394 Weighted-average shares used to compute diluted net (loss) income per share 67,854,356 70,863,665 Net (loss) income per share Basic $ ( 1.75 ) $ 0.02 Diluted $ ( 1.75 ) $ 0.02
Schedule of Antidilutive Shares Excluded from the Calculation of Diluted Net Income (Loss) Per Share	The following stock options and restricted stock units outstanding at each period end have been excluded from the calculation of diluted net income (loss) per share because their inclusion would have been antidilutive: Three Months Ended March 31, 2024 2023 Options to purchase common stock 10,775,502 368,503 Restricted stock units 2,055,340 4,509 Total excluded common stock equivalents 12,830,842 373,012

Product Revenue, Net - Summary

Product Revenue, Net - Summary of Gross Product Revenue to Net product Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenue from Contract with Customer [Abstract]
Product revenue, gross	$ 113,660	$ 84,553
GTN adjustments	(25,017)	(13,125)
Product revenue, net	$ 88,643	$ 71,428

Product Revenue, Net - Schedule

Product Revenue, Net - Schedule of Activity and Ending Reserve Balance for GTN Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
GTN Adjustments, Ending balance	$ 19,162	$ 4,304
GTN Adjustments, Provision related to sales in the current year	27,775	13,361
GTN Adjustments, Adjustments related to prior period sales	(2,758)	(236)
GTN Adjustments, Credits and payments made	(13,231)	(6,047)
GTN Adjustments, Ending balance	30,948	11,382
Chargebacks and Cash Discounts
Disaggregation of Revenue [Line Items]
GTN Adjustments, Ending balance	3,143	648
GTN Adjustments, Provision related to sales in the current year	4,983	6,273
GTN Adjustments, Adjustments related to prior period sales	(1,696)
GTN Adjustments, Credits and payments made	(5,784)	(2,907)
GTN Adjustments, Ending balance	646	4,014
Medicaid and Medicare Rebates
Disaggregation of Revenue [Line Items]
GTN Adjustments, Ending balance	4,946	1,992
GTN Adjustments, Provision related to sales in the current year	3,504	3,640
GTN Adjustments, Adjustments related to prior period sales		(236)
GTN Adjustments, Credits and payments made	(2,201)	(718)
GTN Adjustments, Ending balance	6,249	4,678
Other Rebates, Returns, Discounts and Adjustments
Disaggregation of Revenue [Line Items]
GTN Adjustments, Ending balance	11,073	1,664
GTN Adjustments, Provision related to sales in the current year	19,288	3,448
GTN Adjustments, Adjustments related to prior period sales	(1,062)
GTN Adjustments, Credits and payments made	(5,246)	(2,422)
GTN Adjustments, Ending balance	$ 24,053	$ 2,690

Short-Term Investments - Additi

Short-Term Investments - Additional Information (Details)	3 Months Ended
	Mar. 31, 2024 USD ($) Security	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Debt Securities, Available-for-Sale [Line Items]
Realized gains | $	$ 0	$ 0
Realized loss | $	$ 0	$ 0
Debt securities available-for-sale number of positions | Security	9
Debt securities available-for-sale number of positions in an unrealized loss position | Security	8
Debt securities available-for-sale in an unrealized loss position for greater than 12 months | Security	0
Available-for-Sale Securities
Debt Securities, Available-for-Sale [Line Items]
Accrued interest receivable | $	$ 300,000		$ 500,000

Short-Term Investments - Summar

Short-Term Investments - Summary of Available-for-sale Securities with Unrealized Losses for Less Than 12 Months (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Fair Value	$ 182,832	$ 4,996
Unrealized Losses	(52)	(3)
Treasury Bills
Debt Securities, Available-for-Sale [Line Items]
Fair Value	182,832
Unrealized Losses	$ (52)
Corporate Debt Securities
Debt Securities, Available-for-Sale [Line Items]
Fair Value		4,996
Unrealized Losses		$ (3)

Short-Term Investments - Schedu

Short-Term Investments - Schedule of Short-term Investments Classified as Available-for-sale (Details) - Short-term Investments - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	$ 202,793	$ 201,097
Unrealized Gain		67
Unrealized Loss	(52)	(3)
Fair Value	202,741	201,161
Treasury Bills
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	202,793	196,098
Unrealized Gain		67
Unrealized Loss	(52)
Fair Value	$ 202,741	196,165
Agency Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis		4,999
Unrealized Loss		(3)
Fair Value		$ 4,996

Inventories - Summary of Invent

Inventories - Summary of Inventory (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Inventory Disclosure [Abstract]
Raw materials	$ 53,144
Work in process	18,945
Finished goods	11,191
Total inventories	$ 83,280

Inventories - Additional Inform

Inventories - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)
Inventory Disclosure [Abstract]
Inventory write-downs	$ 92.5

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued external research and development	$ 11,029	$ 12,625
Accrued benefits and incentive compensation	6,204	16,790
Accrued Manufacturing	4,489	1,652
Accrued consulting and other professional fees	8,693	6,506
Accrued rebates and co-pay assistance	18,636	16,063
Accrued royalties		3,111
Accrued loss on future purchase commitments	17,928
Other accrued expenses	895	977
Total accrued expenses	$ 67,874	$ 57,724

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 202,741	$ 201,161
Fair Value Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	202,741	201,161
Assets measured at fair value	282,191	278,590
Fair Value Measurements, Recurring | Cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	78,731	76,710
Fair Value Measurements, Recurring | Treasury Bills
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	202,741	196,165
Fair Value Measurements, Recurring | U.S. Agency Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments		4,996
Fair Value Measurements, Recurring | Restricted Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	719	719
Fair Value Measurements, Recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	202,741	196,165
Assets measured at fair value	282,191	273,594
Fair Value Measurements, Recurring | Level 1 | Cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	78,731	76,710
Fair Value Measurements, Recurring | Level 1 | Treasury Bills
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	202,741	196,165
Fair Value Measurements, Recurring | Level 1 | Restricted Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 719	719
Fair Value Measurements, Recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments		4,996
Assets measured at fair value		4,996
Fair Value Measurements, Recurring | Level 2 | U.S. Agency Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments		$ 4,996

Stock Option and Grant Plan - S

Stock Option and Grant Plan - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Number of Options, Outstanding	9,823,248
Number of Options, Granted	1,357,981
Number of Options, Exercised	(49,618)
Number of Options, Cancelled or forfeited	(356,109)
Number of Options, Outstanding	10,775,502		9,823,248
Number of Options, Options exercisable	4,739,300
Number of Options, Options unvested	6,036,202
Weighted average grant-date fair value of options granted during the period	$ 11
Weighted-Average Exercise Price, Outstanding	18.39
Weighted-Average Exercise Price, Granted	16.76
Weighted-Average Exercise Price, Exercised	2.96
Weighted-Average Exercise Price, Cancelled or forfeited	21.88
Weighted-Average Exercise Price, Outstanding	18.14		$ 18.39
Weighted-Average Exercise Price, Options exercisable	14.87
Weighted-Average Exercise Price, Options unvested	$ 20.7
Weighted- Average Remaining Contractual Term (in years), Outstanding	7 years 10 months 24 days		7 years 10 months 24 days
Weighted- Average Remaining Contractual Term (in years), Options exercisable	7 years
Weighted- Average Remaining Contractual Term (in years), Options unvested	8 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding	$ 27,639
Aggregate intrinsic value, exercised	653	$ 11,700
Aggregate Intrinsic Value, Outstanding	689		$ 27,639
Aggregate Intrinsic Value, Options exercisable	$ 689

Stock Option and Grant Plan - A

Stock Option and Grant Plan - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-Based Payment Arrangement [Abstract]
Aggregate intrinsic value, exercised	$ 653	$ 11,700
Total fair value of stock options vested	$ 14,900	$ 14,700

Stock Option and Grant Plan -_2

Stock Option and Grant Plan - Summary of Restricted Stock Unit Activity (Details) - Restricted Stock Unit	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, Nonvested | shares	1,112,542
Number of shares, Granted | shares	1,242,207
Number of shares, Vested | shares	(231,437)
Number of shares, Forfeited | shares	(67,972)
Number of shares, Nonvested | shares	2,055,340
Weighted Average Grant Date Fair Value, Nonvested | $ / shares	$ 24.8
Weighted Average Grant Date Fair Value, Granted | $ / shares	17.42
Weighted Average Grant Date Fair Value, Vested | $ / shares	25.39
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	24.9
Weighted Average Grant Date Fair Value, Nonvested | $ / shares	$ 20.27

Stock Option and Grant Plan -_3

Stock Option and Grant Plan - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 9,924	$ 7,501
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	2,712	1,891
Selling, General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 7,212	$ 5,610

Stock Option and Grant Plan -_4

Stock Option and Grant Plan - Summary of Unrecognized Stock-Based Compensation Expense and Weighted-Average Recognition Period (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized Expense	$ 80,901
Weighted-average Recognition Period	2 years 7 months 17 days
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized Expense	$ 39,510
Weighted-average Recognition Period	3 years 3 months 18 days

Net (Loss) Income Per Share - S

Net (Loss) Income Per Share - Summary of the Numerator and Denominators Used in Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net (loss) income	$ (118,793)	$ 1,573
Denominator:
Weighted-average shares used to compute basic net (loss) income per share	67,854,356	66,717,271
Dilutive effect of employee stock options and restricted stock units		4,146,394
Weighted-average shares used to compute diluted net (loss) income per share	67,854,356	70,863,665
Net (loss) income per share - basic	$ (1.75)	$ 0.02
Net (loss) income per share - diluted	$ (1.75)	$ 0.02

Net (Loss) Income Per Share -_2

Net (Loss) Income Per Share - Schedule of Antidilutive Shares Excluded from the Calculation of Diluted Net Income (Loss) Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total excluded common stock equivalents	12,830,842	373,012
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total excluded common stock equivalents	10,775,502	368,503
Restricted Stock Unit
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total excluded common stock equivalents	2,055,340	4,509

Commitment and Contingencies -

Commitment and Contingencies - Additional Information (Details)	3 Months Ended		31 Months Ended
	Mar. 31, 2024 USD ($) LeaseAgreement	Mar. 31, 2023 USD ($)	Feb. 28, 2019 USD ($)	Dec. 31, 2023 USD ($)
Commitments And Contingencies [Line Items]
Number of operating lease agreements | LeaseAgreement	2
Restricted cash	$ 700,000			$ 700,000
Accrued expenses	67,874,000			57,724,000
Raw Material Purchases and Manufacturing Services
Commitments And Contingencies [Line Items]
Purchase commitments	35,100,000			$ 195,000,000
Purchase Commitments
Commitments And Contingencies [Line Items]
Loss on purchase commitments	17,900,000
ALS Association and ALS Finding a Cure
Commitments And Contingencies [Line Items]
Accrued royalities grant agreements	0
ALS Association and ALS Finding a Cure | Cost of Sales
Commitments And Contingencies [Line Items]
Royalty expense	0	$ 2,500,000
Royalty Payments Agreements with Grantors
Commitments And Contingencies [Line Items]
Funding received from grantors			$ 4,300,000
Royalty Payments Agreements with Grantors | ALS Association and ALS Finding a Cure
Commitments And Contingencies [Line Items]
Percentage of grant received			150%
Percentage of net sales of products developed under projects			3%
Percentage of cash proceeds from revenue generating transaction			3%
Royalty Payments Agreements with Grantors | Alzheimer's Drug Discovery Foundation, the Alzheimer's Association, and Cure Alzheimer's Fund
Commitments And Contingencies [Line Items]
Maximum Royalty amount payable to each grantor			$ 15,000,000
Aggregate royalty amount payable to grantor			$ 45,000,000
Percentage of annual net sales of products commercialized from project			4%
Percentage of all royalties and cash proceeds from revenue generating transaction			15%
Collateral for Letter of Credit Issued
Commitments And Contingencies [Line Items]
Restricted cash	200,000
Collateral for Corporate Credit Card Program
Commitments And Contingencies [Line Items]
Restricted cash	$ 500,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2024	Mar. 31, 2024
Subsequent Event [Line Items]
Inventory write-down		$ 92.5
Restructuring Plan
Subsequent Event [Line Items]
Inventory write-down		92.5
Loss on purchase commitments		$ 17.9
Subsequent Event | Restructuring Plan
Subsequent Event [Line Items]
Percentage of reduction in workforce	70%
Severance and severance-related charges	$ 19.1