0001564590-22-006495 | 10-K | XBRL Viewer

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Consolidated Balance Sheets - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 294,233,000	$ 1,661,082,000
Marketable securities	1,448,063,000	438,467,000
Prepaid expenses and other current assets	39,841,000	22,821,000
Collaboration receivable - related party	18,506,000
Total current assets	1,800,643,000	2,122,370,000
Property and equipment, net	3,016,000	6,755,000
Restricted cash	1,269,000	1,716,000
Right-of-use operating asset	16,109,000	25,064,000
Other long-term assets	4,251,000	3,341,000
Total assets	1,825,288,000	2,159,246,000
Current liabilities:
Accounts payable	10,450,000	3,691,000
Accrued expenses	67,275,000	54,851,000
Operating lease liability, current portion	7,468,000	8,662,000
Total current liabilities	85,193,000	67,204,000
Operating lease liability, net of current portion	10,964,000	19,438,000
Other liabilities	100,000	270,000
Total liabilities	96,257,000	86,912,000
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized at December 31, 2021 and December 31, 2020; no shares issued or outstanding at December 31, 2021 and December 31, 2020
Common stock, $0.0001 par value per share; 120,000,000 shares authorized at December 31, 2021 and December 31, 2020; 58,940,083 and 58,311,444 shares issued at December 31, 2021 and December 31, 2020; 58,937,050 and 58,308,411 shares outstanding at December 31, 2021 and December 31, 2020	6,000	6,000
Treasury stock, at cost, 3,033 shares at December 31, 2021 and December 31, 2020	(400,000)	(400,000)
Additional paid-in capital	3,227,471,000	3,109,807,000
Accumulated deficit	(1,495,386,000)	(1,037,494,000)
Accumulated other comprehensive gain (loss)	(2,660,000)	415,000
Total stockholders’ equity	1,729,031,000	2,072,334,000
Total liabilities and stockholders’ equity	$ 1,825,288,000	$ 2,159,246,000

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	58,940,083	58,311,444
Common stock, shares outstanding	58,937,050	58,308,411
Treasury stock, shares	3,033	3,033

Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total revenue	$ 6,308	$ 1,114,200	$ 6,868
Operating costs and expenses:
Cost of goods sold	553	565	400
Research and development	283,166	292,714	368,815
Selling, general and administrative	183,498	196,952	345,777
Restructuring		27,743
Total operating costs and expenses	467,217	517,974	714,992
Income (loss) from operations	(460,909)	596,226	(708,124)
Interest income, net	2,883	9,597	27,804
Other income, net	134	250	82
Net income (loss)	$ (457,892)	$ 606,073	$ (680,238)
Net income (loss) per share—basic	$ (7.80)	$ 11.66	$ (13.38)
Net income (loss) per share—diluted	$ (7.80)	$ 11.43	$ (13.38)
Weighted average number of common shares outstanding—basic	58,670,230	51,983,188	50,833,837
Weighted average number of common shares outstanding—diluted	58,670,230	53,003,115	50,833,837
Comprehensive income (loss):
Net income (loss)	$ (457,892)	$ 606,073	$ (680,238)
Other comprehensive items:
Unrealized gain (loss) on marketable securities	(3,075)	(880)	1,810
Total other comprehensive gain (loss)	(3,075)	(880)	1,810
Total comprehensive income (loss)	(460,967)	605,193	(678,428)
Product Revenue [Member]
Total revenue	$ 6,308	6,700	3,957
Collaboration Revenue [Member]
Total revenue			$ 2,911
Collaboration Revenue - Related Party [Member]
Total revenue		$ 1,107,500

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balances at Dec. 31, 2018	$ 862,971	$ 5	$ (211)	$ 1,827,021	$ (515)	$ (963,329)
Balances, Shares at Dec. 31, 2018		46,888,263	3,033
Issuance of common stock from exercise of stock options, Amount	44,276			44,276
Issuance of common stock from exercise of stock options, Shares		1,031,989
Issuance of common stock under the employee stock purchase plan	5,744			5,744
Issuance of common stock under the employee stock purchase plan, Shares		55,404
Stock-based compensation expense	151,508			151,508
Purchase of treasury stock, Amount	(189)		$ (189)
Public offering of common stock, net of offering costs, Amount	560,948			560,948
Public offering of common stock, net of offering costs, Shares		3,833,334
Vesting of restricted stock units, net of employee tax obligations	(2,175)			(2,175)
Vesting of restricted stock units, net of employee tax obligations, Shares		68,204
Unrealized gain (loss) on available-for-sale securities	1,810				1,810
Net income (loss)	(680,238)					(680,238)
Balances at Dec. 31, 2019	944,655	$ 5	$ (400)	2,587,322	1,295	(1,643,567)
Balances, Shares at Dec. 31, 2019		51,877,194	3,033
Issuance of common stock from exercise of stock options, Amount	5,082			5,082
Issuance of common stock from exercise of stock options, Shares		117,025
Issuance of common stock under the employee stock purchase plan	4,936			4,936
Issuance of common stock under the employee stock purchase plan, Shares		72,719
Issuance of common stock under the Stock Purchase Agreement - related party	417,500	$ 1		417,499
Issuance of common stock under the Stock Purchase Agreement - related party, Shares		6,241,473
Stock-based compensation expense	$ 94,968			94,968
Public offering of common stock, net of offering costs, Shares	6,241,473
Unrealized gain (loss) on available-for-sale securities	$ (880)				(880)
Net income (loss)	606,073					606,073
Balances at Dec. 31, 2020	2,072,334	$ 6	$ (400)	3,109,807	415	(1,037,494)
Balances, Shares at Dec. 31, 2020		58,308,411	3,033
Issuance of common stock from exercise of stock options, Amount	12,397			12,397
Issuance of common stock from exercise of stock options, Shares		307,378
Issuance of common stock under the employee stock purchase plan	2,761			2,761
Issuance of common stock under the employee stock purchase plan, Shares		46,759
Stock-based compensation expense	$ 103,891			103,891
Purchase of treasury stock, Shares	(3,033)
Vesting of restricted stock units, net of employee tax obligations	$ (1,385)			(1,385)
Vesting of restricted stock units, net of employee tax obligations, Shares		274,502
Unrealized gain (loss) on available-for-sale securities	(3,075)				(3,075)
Net income (loss)	(457,892)					(457,892)
Balances at Dec. 31, 2021	$ 1,729,031	$ 6	$ (400)	$ 3,227,471	$ (2,660)	$ (1,495,386)
Balances, Shares at Dec. 31, 2021		58,937,050	3,033

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income (loss)	$ (457,892)	$ 606,073	$ (680,238)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Stock-based compensation expense	104,629	95,994	153,231
Premium on marketable securities	(23,641)	(1,736)	(3,674)
Amortization of premium (discount) on marketable securities	13,046	1,048	(6,966)
Depreciation	4,182	2,630	2,283
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(17,020)	3,879	(4,781)
Collaboration receivable - related party	(18,506)
Other long-term assets	(910)	452	(3,793)
Right-of-use operating asset	5,221	6,397	8,168
Operating lease liabilities, current	206	36	2,804
Operating lease liabilities, non-current	(5,944)	(6,825)	(10,761)
Accounts payable	6,689	(11,511)	(18,783)
Accrued expenses and other liabilities	11,758	(32,157)	33,804
Net cash provided by (used in) operating activities	(378,182)	664,280	(528,706)
Cash flows from investing activities
Proceeds from sales and maturities of marketable securities	988,075	901,749	1,171,270
Purchases of marketable securities	(1,990,151)	(458,720)	(1,308,675)
Purchases of property and equipment	(372)	(345)	(5,751)
Net cash provided by (used in) investing activities	(1,002,448)	442,684	(143,156)
Cash flows from financing activities
Proceeds from stock option exercises and employee stock purchase plan issuances	14,719	9,262	48,850
Payment of employee tax obligations related to vesting of restricted stock units	(1,385)		(2,175)
Payments of offering costs			(328)
Proceeds from the sale of common stock under the Stock Purchase Agreement - related party		417,500
Proceeds from public offerings of common stock, net of commissions and underwriting discounts			561,277
Net cash provided by financing activities	13,334	426,762	607,624
Net increase (decrease) in cash, cash equivalents and restricted cash	(1,367,296)	1,533,726	(64,238)
Cash, cash equivalents and restricted cash at beginning of period	1,662,798	129,072	193,310
Cash, cash equivalents and restricted cash at end of period	295,502	1,662,798	129,072
Supplemental disclosure of non-cash operating and investing activities
Purchases of property and equipment included in accounts payable	70		65
Right-of-use assets obtained in exchange for new operating lease liabilities			$ 872
Lease asset de-recognized upon lease cancellation	$ 3,733	$ 2,310

Nature of the Business

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of the Business

1.	Nature of the Business

Sage Therapeutics, Inc. (“Sage” or the “Company”) is a biopharmaceutical company committed to developing and commercializing novel medicines with the potential to transform the lives of people with debilitating disorders of the brain.

The Company’s first product, ZULRESSO® (brexanolone) CIV injection, is approved in the U.S. as a treatment for postpartum depression (“PPD”) in adults. The Company launched ZULRESSO commercially in the U.S. in June 2019. The Company has a portfolio of other product candidates with a current focus on modulating two critical central nervous system (“CNS”) receptor systems, GABA and NMDA. The GABA receptor family, which is recognized as the major inhibitory neurotransmitter in the CNS, mediates downstream neurologic and bodily function via activation of GABA_A receptors. The NMDA-type receptors of the glutamate receptor system are a major excitatory receptor system in the CNS. Dysfunction in these systems is implicated in a broad range of CNS disorders. The Company is currently targeting diseases and disorders of the brain with three key focus areas: depression, neurology and neuropsychiatry.

The Company was incorporated under the laws of the State of Delaware on April 16, 2010, and commenced operations on January 19, 2011 as Sterogen Biopharma, Inc. On September 13, 2011, the Company changed its name to Sage Therapeutics, Inc.

Risks and Uncertainties

The Company is subject to risks and uncertainties common to companies in the biotechnology and pharmaceutical industries, including, but not limited to, the risks associated with developing product candidates at each stage of non-clinical and clinical development; the challenges associated with gaining regulatory approval of such product candidates; the risks associated with the marketing and sale of pharmaceutical products; the potential for development by third parties of new technological innovations that may compete with the Company’s products and product candidates; the dependence on key personnel; the challenges of protecting proprietary technology; the need to comply with government regulations; the high costs of drug development; the uncertainty of being able to secure additional capital when needed to fund operations; and the potential impact of the COVID-19 pandemic on its development activities, operations and financial condition.

The product candidates developed by the Company require approvals from the U.S. Food and Drug Administration (“FDA”) or foreign regulatory agencies prior to commercial sales. There can be no assurance that the current and future product candidates of the Company will receive, or that the Company’s current product, ZULRESSO, will maintain, the necessary approvals. If the Company fails to successfully complete clinical development and generate results sufficient to file for regulatory approval or is denied approval or approval is delayed for any of its product candidates, such occurrences may have a material adverse impact on the Company’s business and its financial statements.

The ongoing COVID-19 pandemic has caused and may continue to cause major disruptions to businesses and economies worldwide. The rapid spread of COVID-19 in the U.S. resulted in a significant reduction in patient demand for ZULRESSO and in the number of sites available to administer ZULRESSO. This has had a negative impact on the Company’s revenue from sales of ZULRESSO. While the Company has not experienced any other material disruptions to date as a result of the COVID-19 pandemic, any prolonged material disruptions to the work of the Company’s employees, suppliers, contract manufacturers, or vendors could negatively impact the Company’s activities, availability of supplies, or operating results. While the Company has seen slower recruitment in certain of its clinical trials due to the COVID-19 pandemic, especially with respect to older patients and in the SKYLARK Study in patients with PPD, which caused us to revise our expected timeline for reporting topline data from that study, the Company to date has not experienced other significant impacts to the Company’s development activities as a result of the COVID-19 pandemic. Any material disruption to the Company’s development activities may cause delays, increase the Company’s costs and impact the Company’s operating results. In addition, the COVID-19 pandemic initially caused major volatility in capital markets and

a significant global economic downturn, and the Company’s ability to access the capital markets in the future could be negatively impacted if current efforts to control the COVID-19 pandemic are not successful.

Going Concern

Under Accounting Standards Update (“ASU”) No. 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40), the Company has the responsibility to evaluate whether conditions and/or events raise substantial doubt about its ability to meet its future financial obligations as they become due within one year after the date that the financial statements are issued. The Company has incurred losses and negative cash flows from operations since its inception, except for net income of $606.1 million for the year ended December 31, 2020, reflecting revenue recognized under a collaboration and license agreement with Biogen MA Inc. (“BIMA”) and Biogen International GmbH (collectively with BIMA, “Biogen”) (the “Biogen Collaboration Agreement”). As of December 31, 2021, the Company had an accumulated deficit of $1.5 billion. From its inception through December 31, 2021, the Company has received aggregate net proceeds of $2.8 billion from the sales of redeemable convertible preferred stock prior to its initial public offering, the issuance of convertible notes, and the sales of common stock in its initial public offering (“IPO”) in July 2014, in follow-on public offerings and to BIMA under a stock purchase agreement executed in connection with the Biogen Collaboration Agreement. The Company has also received $1.0 billion in upfront payments under its collaborations with Biogen and Shionogi & Co., Ltd. (“Shionogi”). Until such time, if ever, as the Company can generate substantial product revenue and achieve profitability, the Company expects to finance its cash needs through a combination of equity offerings, debt financings, collaborations, strategic alliances, licensing arrangements and other sources of funding. If the Company is unable to raise additional funds through equity or debt financings or other sources of funding when needed, the Company may be required to delay, limit, reduce or terminate product development or future commercialization efforts or grant rights to develop and market products or product candidates that the Company would otherwise prefer to develop and market itself.

The Company expects that, based on its current operating plans, the Company’s existing cash, cash equivalents and marketable securities will be sufficient to fund its currently planned operations for at least the next 12 months from the filing date of this Annual Report. At some point after that time, the Company anticipates it will require additional financing to fund its future operations. Even if the Company believes it has sufficient funds for its current or future operating plans, the Company may seek to raise additional capital if market conditions are favorable or in light of other strategic considerations.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies

The following is a summary of significant accounting policies followed in the preparation of these consolidated financial statements.

Basis of Presentation

The accompanying consolidated financial statements include those of the Company and its subsidiaries after elimination of all intercompany accounts and transactions. The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the U.S. (“GAAP”).

Principles of Consolidation

The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. Intercompany accounts and transactions have been eliminated.

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets

and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The full extent to which the COVID-19 pandemic may directly or indirectly impact the Company’s business, results of operations and financial condition, including sales, expenses, reserves and allowances, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including: the scope and duration of the pandemic; the effectiveness of vaccination campaigns, vaccine mandates, and other efforts to control the pandemic; the duration of the vaccines’ efficacy against COVID-19 and its variants; the duration and severity of any restrictive measures taken to curb the spread of COVID-19; healthcare staffing shortages; and the impact of the pandemic on the Company’s customers and vendors. The Company has made estimates of the impact of the COVID-19 pandemic within its consolidated financial statements. Due to the evolving nature of the COVID-19 pandemic, and the emergence of highly contagious variants, there may be changes to those estimates in future periods, and actual results could differ from those estimates.

Cash Equivalents

The Company considers all highly liquid investments with an original maturity of 90 days or less to be cash equivalents. As of December 31, 2021, cash equivalents were comprised of money market funds, U.S. commercial paper and international commercial paper. As of December 31, 2020, cash equivalents were comprised of commercial paper, money market funds and U.S. treasury securities.

Marketable Securities

Marketable securities consist of investments with original maturities greater than 90 days. The Company has classified its investments with maturities beyond one year as short-term, based on their highly liquid nature and because such marketable securities represent the investment of cash that is available for current operations. The Company considers its investment portfolio of marketable securities to be available-for-sale. Accordingly, these investments are recorded at fair value, which is based on quoted market prices. Unrealized gains and losses are reported as the accumulated other comprehensive items in stockholders’ equity. When the fair value is below the amortized cost of the asset, an estimate of expected credit losses is made. The credit-related impairment amount is recognized in net income (loss); the remaining impairment amount and unrealized gains are reported as a component of accumulated other comprehensive items in stockholders’ equity. Credit losses are recognized through the use of an allowance for credit losses account and subsequent improvements in expected credit losses are recognized as a reversal of an amount in the allowance for credit losses account. If the Company has the intent to sell the security or it is more likely than not that the Company will be required to sell the security prior to recovery of its amortized cost basis, then the allowance for the credit loss is written-off and the excess of the amortized cost basis of the asset over its fair value is recorded in the consolidated statements of operations and comprehensive income (loss). Regardless of the Company’s intent to sell a security, it performs additional analysis on all securities with unrealized losses to evaluate losses associated with the creditworthiness of the security. Credit losses are identified where the Company does not expect to receive cash flows sufficient to recover the amortized cost basis of a security.

Accounts Receivable

The Company’s trade accounts receivable consist of amounts due from specialty distributors, specialty pharmacies, and medically-supervised healthcare settings that have been certified under a Risk Evaluation and Mitigation Strategy (“REMS”) program in the U.S. related to sales of ZULRESSO and have standard payment terms that generally require payment within 30 to 90 days from the invoice date. The Company monitors the financial performance and creditworthiness of customers so that it can properly assess and respond to changes in their credit profiles. The Company makes judgments as to its ability to collect outstanding receivables and provides an allowance for bad debts against the trade account receivables, when appropriate. Trade accounts receivable are included in prepaid expenses and other current assets on the consolidated balance sheets. As of December 31, 2021, the Company has not provided any allowance for bad debts against the trade accounts receivable, and the amount of trade accounts receivable was not significant.

Inventory

Inventory is stated at the lower of cost or estimated net realizable value with cost determined on a first-in, first-out basis. Inventory costs include raw materials, third-party contract manufacturing, third-party packaging services, and freight. Raw and intermediate materials that may be utilized for either research and development or commercial purposes are classified as inventory. Amounts in inventory that are used for research and development purposes are charged to research and development expense when the product enters the research and development process and can no longer be used for commercial purposes and, therefore, does not have an “alternative future use” as defined in authoritative guidance. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period and, if needed, writes down any excess and obsolete inventory to its estimated net realizable value in the period it is identified. If they occur, such impairment charges are recorded as a component of cost of goods sold in the consolidated statements of operations and comprehensive income (loss). Inventory is included in prepaid expenses and other current assets on the consolidated balance sheets and the amount was not significant as of December 31, 2021.

Prior to the initial date that regulatory approval is received, costs related to the production of inventory are recorded as research and development expense on the Company’s consolidated statements of operations and comprehensive income (loss) in the period incurred. In connection with the FDA approval of ZULRESSO in March 2019, the Company subsequently began capitalizing inventory manufactured or purchased after this date.

Property and Equipment

Property and equipment are recorded at cost and depreciated over their estimated useful lives using the straight-line method. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is credited or charged to income. Repairs and maintenance costs are expensed as incurred.

Leases

The Company determines if an arrangement is a lease at contract inception. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent the Company’s obligation to make payments arising from the lease. Operating lease assets and liabilities are recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. When determining the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain that the Company will exercise those options. The Company uses the implicit interest rate when readily determinable and uses the Company’s incremental borrowing rate when the implicit interest rate is not readily determinable based upon the information available at the commencement date of the lease in determining the present value of the lease payments.

The lease payments used to determine the Company’s operating lease assets may include lease incentives, stated rent increases and escalation clauses linked to rates of inflation, when determinable, and are recognized in the Company’s operating lease assets in the Company’s consolidated balance sheets. In addition, the Company’s contracts may contain lease and non-lease components. The Company combines lease and non-lease components, which are accounted for together as lease components.

The Company’s operating leases are reflected in the right-of-use operating asset; operating lease liability, current portion; and operating lease liability, net of current portion in the Company’s consolidated balance sheets. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. Short-term leases, defined as leases that have a lease term of 12 months or less at the commencement date, are not recorded on the Company’s consolidated balance sheets and are recognized in the consolidated statements of operations and comprehensive income (loss) on a straight-line basis over the term of the lease.

Variable lease payments are the amounts owed by the Company to a lessor that are not fixed, such as reimbursement for common area maintenance and utilities costs for facility leases and maintenance and tolls for leased vehicles. Variable lease payments are expensed when incurred.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends, and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. To date, the Company has not recorded any impairment losses on long-lived assets.

Cost of Goods Sold

Cost of goods sold includes direct and indirect costs related to the manufacturing and distribution of ZULRESSO, including third-party manufacturing costs, packaging services, freight, third-party royalties payable on the Company’s net product revenues and amortization of intangible assets associated with ZULRESSO. Cost of goods sold may also include period costs related to certain inventory manufacturing services, inventory adjustment charges, as well as manufacturing variances. In connection with the FDA approval of ZULRESSO in March 2019, the Company subsequently began capitalizing inventory manufactured or purchased after this date. As a result, certain manufacturing costs associated with product shipments of ZULRESSO were expensed prior to FDA approval and, therefore, are not included in cost of goods sold during the years ended December 31, 2021 and 2020.

Research and Development Costs and Accruals

Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries and benefits, overhead costs, depreciation, contract services and other related costs. Research and development costs are expensed to operations as the related obligation is incurred.

The Company has entered into various research and development contracts with research institutions and other companies both inside and outside of the U.S. These agreements are generally cancelable, and related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When billing terms under these contracts do not coincide with the timing of when the work is performed, the Company is required to make estimates of outstanding obligations to those third parties as of the end of the reporting period. Any accrual estimates are based on a number of factors, including the Company’s knowledge of the progress towards completion of the research and development activities, invoicing to date under the contracts, communication from the research institution or other companies of any actual costs incurred during the period that have not yet been invoiced, and the costs included in the contracts. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the estimates made by the Company. The historical accrual estimates made by the Company have not been materially different from the actual costs.

Stock-Based Compensation

The Company recognizes compensation expense for stock-based awards, including grants of stock options and restricted stock units, made to employees, non-employee directors and non-employee consultants based on the estimated fair value on the date of grant, over the requisite service period. The Company recognizes stock-based compensation expense for only the portion of awards that are expected to vest.

For awards that vest upon achievement of a performance condition, the Company recognizes compensation expense when achievement of the performance condition is met or during the period from which meeting the condition is deemed probable until the expected date of meeting the performance condition, using management’s best estimates, which consider the inherent risk and uncertainty regarding the future outcomes of the milestones.

The fair value of each stock option grant is estimated using the Black-Scholes option-pricing model. Through the year ended December 31, 2019, the Company estimated its expected volatility using a weighted average of the historical volatility of publicly-traded peer companies and the volatility of its common stock. Effective January 1, 2020, the Company began using the historical volatility of only its common stock, as there is adequate historical data for the duration of the expected term.

The expected term of the stock options granted to employees, non-employee directors and non-employee consultants by the Company has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” stock options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the date of grant for time periods approximately equal to the expected term of the award. The expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The Company also applies a forfeiture rate in order to calculate stock-based compensation expense. Expected forfeitures are based on the historical experience of the Company and management’s expectations of future forfeitures. To the extent actual forfeitures differ from the estimates, the difference is recorded as a cumulative adjustment in the period in which the estimates are revised.

Treasury Stock

The Company records treasury stock at cost. Treasury stock consists of shares of the Company’s common stock received from a then-employee as consideration for exercises of stock options.

Basic and Diluted Net Income (Loss) Per Share

Basic net income (loss) per share is computed by dividing the net income (loss) by the weighted average number of shares of common stock that were outstanding during the period. Diluted net income (loss) per share is computed by adjusting the weighted average number of shares of common stock that were outstanding during the period for the dilutive effect of common stock equivalents outstanding for the period by using the treasury stock method.

For periods in which the Company has reported net losses, diluted net loss per share is the same as basic net loss per share, because dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss for the years ended December 31, 2021 and 2019.

Concentration of Credit Risk and of Significant Suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company maintains accounts for all cash and cash equivalents at accredited financial institutions, in amounts that exceed federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

The Company is dependent on third-party manufacturers to supply products for research and development activities for its programs. The Company also relies and expects to continue to rely on third-party manufacturers to supply it with active pharmaceutical ingredients (“API”) and formulated drugs; and to provide other services related to manufacturing activities for these programs. These programs could be adversely affected by a significant interruption in the supply of API and formulated drugs, or the interruption of manufacturing related services.

Income Taxes

The Company accounts for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted rates in effect for the year in which these temporary differences are expected to be recovered or settled. Valuation allowances are provided if, based on the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of Accounting Standards Codification (“ASC”) Topic 740, “Income Taxes” (“Topic 740”). When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. The Company accrues for potential interest and penalties related to unrecognized tax benefits in income tax expense.

Fair Value Measurements

Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Financial assets and liabilities carried at fair value are classified and disclosed in one of the following three categories:

Level 1	—	Quoted market prices in active markets for identical assets or liabilities.

Level 2	—	Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3	—	Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The Company’s cash equivalents and marketable securities at December 31, 2021 and 2020 were carried at fair value, determined according to the fair value hierarchy; see Note 3, Fair Value Measurements.

The carrying amounts reflected in the consolidated balance sheets for the collaboration receivable – related party, accounts payable and accrued expenses approximate their fair values due to their short-term maturities at December 31, 2021 and 2020, respectively.

Segment Data

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The singular focus of the Company is developing and commercializing novel therapies with the potential to transform the lives of people with debilitating disorders of the brain.

Comprehensive Income (Loss)

Comprehensive income (loss) includes net income (loss) and other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. The Company’s only element of other comprehensive income (loss) is unrealized gains and losses on marketable securities that are considered to be available-for-sale.

Revenue Recognition

The Company generates revenue from the sale of ZULRESSO, which was approved by the FDA in March 2019 and the Company subsequently began selling in June 2019, and from collaboration and supply agreements with the Company’s collaborators. To date, revenue from collaboration agreements has come from initial, upfront payments allocated to licenses of intellectual property delivered to the Company’s collaborators and from the supply of material for clinical trials under a supply agreement.

Under ASC Topic 606, Revenue from Contracts with Customers (“Topic 606”), an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price,

including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations. The exercise of a material right may be accounted for as a contract modification or as a continuation of the contract for accounting purposes.

For contracts determined to be within the scope of Topic 606, the Company assesses whether the goods or services promised within each contract are distinct to identify those that are performance obligations. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract.

The Company allocates the transaction price (the amount of consideration it expects to be entitled to from a customer in exchange for the promised goods or services) to each performance obligation and recognizes the associated revenue when (or as) each performance obligation is satisfied. The Company’s estimate of the transaction price for each contract includes all variable consideration to which the Company expects to be entitled.

Collaboration and License Revenue

In assessing whether a promised good or service is distinct in the evaluation of a collaboration or license arrangement subject to Topic 606, the Company considers factors such as the research, manufacturing and commercialization capabilities of the collaboration partner, and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, the Company is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct.

The transaction price is then determined and allocated to the identified performance obligations in proportion to their standalone selling prices (“SSP”) on a relative SSP basis. SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations requires significant judgment. In developing the SSP for a performance obligation, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. In certain circumstances, the Company may apply the residual method to determine the SSP of a good or service if the standalone selling price is considered highly variable or uncertain. The Company validates the SSP for performance obligations by evaluating whether changes in the key assumptions used to determine the SSP will have a significant effect on the allocation of arrangement consideration between multiple performance obligations.

If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment.

If an arrangement includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated

milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received.

In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less. The Company assessed its arrangements with Shionogi and Biogen and concluded that a significant financing component does not exist for either arrangement. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied.

The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied at a point in time or over time, and if over time this is based on the use of an output or input method. Revenue from the Company’s collaboration agreement with Shionogi has come from initial, upfront consideration upon execution of the agreement and for the supply of drug product for Shionogi clinical trials. Revenue from the Company’s collaboration agreement with Biogen has come from initial, upfront consideration related to the execution of the Biogen Collaboration Agreement. For additional information, refer to Note 6, Collaboration Agreements.

Product Revenue, Net

The Company recognizes product revenues, net of variable consideration related to certain allowances and accruals that are determined using the expected value method, in its consolidated financial statements at the point in time when control transfers to the customer, which is typically when the product has been delivered to the customer’s location. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. The Company’s only performance obligation identified for ZULRESSO is to deliver the product to the location specified by the customer’s order. The Company records shipping and handling costs associated with delivery of product to its customers within selling, general and administrative expenses on its consolidated statements of operations and comprehensive income (loss). The Company expenses incremental costs of obtaining a contract as incurred if the expected amortization period of the asset would be less than one year. If the Company were to incur incremental costs with an amortization period greater than a year, such costs would be capitalized as contract assets, as they are expected to be recovered, and would be expensed by amortizing on a systematic basis that is consistent with the transfer to the customer of the goods or services to which the asset relates. The Company did not have any contract assets (unbilled receivables) at December 31, 2021, as customer invoicing generally occurs before or at the time of revenue recognition. The Company did not have any contract liabilities at December 31, 2021, as the Company did not receive any payments in advance of satisfying its performance obligations to its customers. Amounts billed or invoiced that are considered trade accounts receivable are included in prepaid expenses and other current assets on the consolidated balance sheets.

As of December 31, 2021 and 2020, the Company had not provided any allowance for bad debts against the trade accounts receivable, and the amount of trade accounts receivable was not significant.

The Company records reserves, based on contractual terms, for the following components of variable consideration related to product sold during the reporting period, as well as its estimate of product that remains in the distribution channel inventory of its customers at the end of the reporting period. On a quarterly basis, the Company updates its estimates, if necessary, and records any material adjustments in the period they are identified.

Chargebacks: The Company estimates chargebacks from its customers who directly purchase the product from the Company for discounts resulting from contractual commitments to sell products to eligible healthcare settings at prices lower than the list prices charged to its customers. Customers charge the Company for the difference between what they pay to the Company for the product and the selling price to the eligible healthcare settings. Reserves for chargebacks consist of credits that the Company expects to issue for units that remain in the distribution channel inventories at the end of each reporting period that the Company expects will be sold to eligible healthcare settings, and chargebacks that customers have claimed, but for which the Company has not yet issued a credit.

Government Rebates: The Company is subject to discount obligations under government programs, including Medicaid. The Company records reserves for rebates in the same period the related product revenue is recognized, resulting in a reduction of ZULRESSO product revenues and a current liability that is included in accrued expenses on its consolidated balance sheets. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimates of future claims that will be made for product that has been recognized as revenue, but which remains in the distribution channel at the end of each reporting period.

Trade Discounts and Allowances: The Company generally provides customary invoice discounts on ZULRESSO sales to its customers for prompt payment and the Company pays fees for sales order management, data, and distribution services. The Company estimates its customers will earn these discounts and fees and deducts these discounts and fees in full from gross ZULRESSO revenues and accounts receivable at the time the Company recognizes the related revenues.

Financial Assistance: The Company provides voluntary financial assistance programs to patients with commercial insurance that have coverage and reside in states that allow financial assistance. The Company estimates the financial assistance amounts for ZULRESSO and records any such amounts within accrued expenses on its consolidated balance sheets. The calculation of the accrual for financial assistance is based on an estimate of claims and the cost per claim that the Company expects to receive using demographics for patients who have registered and been approved for assistance. Any adjustments are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability, which is included as a component of accrued expenses on the consolidated balance sheets.

Product Returns: Consistent with industry practice, the Company offers product return rights to customers for damaged, defective or expiring product, provided it is within a specified period around the product expiration date as set forth in the Company’s return goods policy. The Company estimates the amount of its product sales that may be returned by its customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized, as well as a reserve within accrued expenses on the consolidated balance sheets. Product returns have been immaterial to date and are expected to remain immaterial in the future.

Collaborative Arrangements

The Company analyzes its collaboration arrangements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of ASC Topic 808, Collaborative Arrangements (“Topic 808”). This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For collaboration arrangements within the scope of Topic 808 that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of Topic 808 and which elements of the collaboration are more reflective of a vendor-customer relationship and therefore within the scope of Topic 606. For elements of collaboration arrangements that are accounted for pursuant to Topic 808, an appropriate recognition method is determined and applied consistently, either by analogy to authoritative accounting literature or by applying a reasonable and rational policy election. For those elements of the arrangement that are accounted for pursuant to Topic 606, the Company applies the five-step model described above, and presents the arrangement as collaboration revenue in the consolidated statements of operations and comprehensive income (loss).

For collaboration arrangements that are within the scope of Topic 808, the Company evaluates the income statement classification for presentation of amounts due from or owed to other participants associated with multiple activities in a collaboration arrangement based on the nature of each separate activity. Payments or reimbursements that are the result of a collaborative relationship instead of a customer relationship, such as co-development and co-commercialization activities, are recorded as research and development expense or selling, general and administrative expense, in the event of a payment to the collaborative partner in a period, or a reduction to these expense line items in the event of a reimbursement from the collaboration partner in a period, as appropriate.

Recently Issued Accounting Pronouncements

In June 2016, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This standard amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. For available-for-sale debt securities, entities are required to recognize an allowance for credit losses rather than a reduction in carrying value of the asset. Entities are no longer permitted to consider the length of time that fair value has been less than amortized cost when evaluating when credit losses should be recognized. The Company adopted the standard on the required effective date of January 1, 2020, on a prospective basis. This guidance did not have a significant impact on the Company’s consolidated financial statements and related disclosures.

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. This standard modifies certain disclosure requirements on fair value measurements. The Company adopted the standard on the required effective date of January 1, 2020. This guidance did not have a significant impact on the Company’s consolidated financial statements and related disclosures.

In November 2018, the FASB issued ASU No. 2018-18, Clarifying the Interaction between Topic 808 and Topic 606. This standard clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under Topic 606 when the collaborative arrangement participant is a customer for a promised good or service that is distinct within the collaborative arrangement. The guidance also precludes entities from presenting amounts related to transactions with a collaborative arrangement participant that is not a customer as revenue, unless those transactions are directly related to third-party sales. The Company adopted the standard on the required effective date of January 1, 2020. This guidance did not have a significant impact on the Company’s consolidated financial statements and related disclosures.

In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. This standard enhances and simplifies various aspects of the income tax accounting guidance in ASC Topic 740, Income Taxes, including requirements related to hybrid tax regimes, the tax basis step-up in goodwill obtained in a transaction that is not a business combination, separate financial statements of entities not subject to tax, the intra-period tax allocation exception to the incremental approach, ownership changes in investments, changes from a subsidiary to an equity method investment, interim-period accounting for enacted changes in tax law, and the year-to-date loss limitation in interim-period tax accounting. The Company adopted the standard on the required effective date of January 1, 2021. This guidance did not have a significant impact on the Company’s consolidated financial statements and related disclosures.

Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s consolidated financial statements upon adoption.

Fair Value Measurements

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

3.	Fair Value Measurements

The Company’s cash equivalents are classified within Level 1 and Level 2 of the fair value hierarchy. The Company’s investments in marketable securities are classified within Level 2 of the fair value hierarchy.

The fair values of the Company’s marketable securities are based on prices obtained from independent pricing sources. Consistent with the fair value hierarchy described in Note 2, Summary of Significant Accounting Policies, marketable

securities with validated quotes from pricing services are reflected within Level 2, as they are primarily based on observable pricing for similar assets or other market observable inputs. Typical inputs used by these pricing services include, but are not limited to, reported trades, benchmark yields, issuer spreads, bids, offers or estimates of cash flow, prepayment spreads and default rates. The Company performs validation procedures to ensure the reasonableness of this data. The Company performs its own review of prices received from the independent pricing services by comparing these prices to other sources. After completing the validation procedures, the Company did not adjust or override any fair value measurements provided by the pricing services as of December 31, 2021 and 2020.

The following tables summarize the Company’s cash equivalents and marketable securities as of December 31, 2021 and 2020:

	December 31, 2021
	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Cash equivalents	$	294,233	$	290,234	$	3,999	$	—
Total cash equivalents		294,233		290,234		3,999		—
Marketable securities:
U.S. government securities		324,532		—		324,532		—
U.S. corporate bonds		627,780		—		627,780		—
International corporate bonds		236,812		—		236,812		—
U.S. commercial paper		80,176		—		80,176		—
International commercial paper		142,335		—		142,335		—
U.S. municipal securities		36,428		—		36,428		—
Total marketable securities		1,448,063		—		1,448,063		—
	$	1,742,296	$	290,234	$	1,452,062	$	—

	December 31, 2020
	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Cash equivalents	$	1,661,082	$	1,637,609	$	23,473	$	—
Total cash equivalents		1,661,082		1,637,609		23,473		—
Marketable securities:
U.S. government securities		160,588		—		160,588		—
U.S. corporate bonds		123,107		—		123,107		—
International corporate bonds		57,676		—		57,676		—
U.S. commercial paper		45,963		—		45,963		—
International commercial paper		51,133		—		51,133		—
Total marketable securities		438,467		—		438,467		—
	$	2,099,549	$	1,637,609	$	461,940	$	—

During the years ended December 31, 2021 and 2020, there were no transfers among the Level 1, Level 2 and Level 3 categories.

The following tables summarize the gross unrealized gains and losses of the Company’s marketable securities as of December 31, 2021 and 2020:

	December 31, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Fair Value
	(in thousands)
Assets:
U.S. government securities	$	325,514	$	—	$	(982	)	$	—	$	324,532
U.S. corporate bonds		628,836		27		(1,083	)		—		627,780
International corporate bonds		237,303		—		(491	)		—		236,812
U.S. commercial paper		80,194		—		(18	)		—		80,176
International commercial paper		142,358		—		(23	)		—		142,335
U.S. municipal securities		36,518		—		(90	)		—		36,428
	$	1,450,723	$	27	$	(2,687	)	$	—	$	1,448,063

	December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Fair Value
	(in thousands)
Assets:
U.S. government securities	$	160,589	$	11	$	(12	)	$	—	$	160,588
U.S. corporate bonds		122,882		240		(15	)		—		123,107
International corporate bonds		57,485		200		(9	)		—		57,676
U.S. commercial paper		45,963		—		—			—		45,963
International commercial paper		51,133		—		—			—		51,133
	$	438,052	$	451	$	(36	)	$	—	$	438,467

As of December 31, 2021, all marketable securities held by the Company had remaining contractual maturities of one year or less, except for U.S. government securities, U.S. corporate bonds, international corporate bonds and municipal securities with a fair value of $436.1 million that had maturities of one to two years.

As of December 31, 2020, all marketable securities held by the Company had remaining contractual maturities of one year or less, except for corporate bonds with a fair value of $5.1 million that had maturities of one to two years.

All marketable securities, including those with remaining contractual maturities of more than one year, are classified as current assets on the balance sheet because they are considered to be “available for sale” and the Company can convert them into cash to fund current operations.

As of December 31, 2021, the marketable securities in a loss position had a maturity of less than one year, except for U.S. government securities, U.S. corporate bonds, international corporate bonds and municipal securities. with a fair value of $431.5 million, that had maturities of one to two years. As of December 31, 2020, the marketable securities in a loss position had a maturity of less than one year.

There have been no impairments of the Company’s assets measured and carried at fair value during the years ended December 31, 2021 and 2020.

Balance Sheet Components

12 Months Ended

Dec. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

4.	Balance Sheet Components

Property and Equipment, net

Property and equipment, net consists of the following:

	December 31,			December 31,
	2021			2020
	(in thousands)
Computer hardware and software	$	1,391		$	2,758
Furniture and equipment		1,208			1,865
Leasehold improvements		5,390			9,220
		7,989			13,843
Less: Accumulated depreciation		(4,973	)		(7,088	)
	$	3,016		$	6,755

Depreciation expense for the years ended December 31, 2021, 2020 and 2019 was $4.2 million, $2.6 million and $2.3 million, respectively.

The useful life for computer hardware and software is three years, furniture and equipment is five years and leasehold improvements is the lesser of the useful life or the term of the respective lease.

Accrued Expenses

Accrued expenses consist of the following:

	December 31,		December 31,
	2021		2020
	(in thousands)
Accrued research and development costs	$	39,147	$	34,398
Employee-related		18,618		14,769
Professional services		8,893		5,184
Other		617		500
	$	67,275	$	54,851

Leases, Commitments and Contingencies

12 Months Ended

Dec. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Leases, Commitments and Contingencies

5.	Leases, Commitments and Contingencies

Operating Leases

The Company leases office space and certain equipment. All of the leases recorded on the consolidated balance sheets are operating leases. The Company’s leases have remaining lease terms ranging from less than one year to approximately three years. Some of the leases include options to extend the leases for up to five years. These options were not included for the purpose of determining the right-of-use assets and associated lease liabilities as the Company determined that the renewal of these leases is not reasonably certain so only the original lease term was taken into consideration. The leases do not include any restrictions or covenants that had to be accounted for under the lease guidance.

As of January 1, 2019, the Company leased office space in three multi-tenant buildings in Cambridge, Massachusetts, consisting of 58,442 square feet in the first building, under an operating lease that will expire on August 31, 2024; 40,419 square feet in the second building, under an operating lease that will expire on August 31, 2024 and 15,975 square feet in the third building, under an operating lease that began on March 1, 2019 and was initially scheduled to expire on February 29, 2024; and in a multi-tenant building in Raleigh, North Carolina, consisting of 15,525 square feet under an operating lease that will expire on November 30, 2024.

In March 2019, the Company entered into the Eighth Amendment to the operating lease for office space in the first multi-tenant building in Cambridge, Massachusetts, and thereby increased the amount of square feet of office space from 58,442 square feet to 63,017 square feet. The increase of 4,575 square feet began on June 1, 2019. The term for this additional space will expire on August 31, 2024.

During the year ended December 31, 2021, the Company terminated the operating lease for office space in the third multi-tenant building in Cambridge, Massachusetts and the remaining right-of-use asset of $3.7 million and the associated liabilities related to this lease were de-recognized upon termination of the lease. Additionally, during the year ended December 31, 2021, the Company entered into a sublease for a portion of the leased office space in the second multi-tenant building in Cambridge, Massachusetts.

From June 2018 to January 2019, the Company entered into leases for vehicles for field-based employees. These leases were determined to be operating leases and a right-of-use operating asset in the amount of $5.3 million was recorded on the balance sheet upon implementation of the new lease standard on January 1, 2019. The leases were for a term of three years and were to expire on various dates through January 31, 2022. During the year ended December 31, 2020, these leases were terminated as part of the April 2020 restructuring (see Note 13, Restructuring), and the remaining right-of-use asset of $2.3 million and the associated liabilities related to these leases were de-recognized upon termination of the leases. During the year ended December 31, 2020, the restricted cash of $0.7 million related to these leases was returned to the Company by the lessor.

The following table shows the amounts of operating leases in the balance sheets as of December 31, 2021 and 2020:

		December 31,
Balance sheet location	Balance sheet caption	2021		2020
		(in thousands)
Assets
Right-of-use operating asset	Right-of-use operating asset	$	16,109	$	25,064

Liabilities
Current operating lease liabilities	Operating lease liability, current portion		7,468		8,662
Long-term operating lease liabilities	Operating lease liability, net of current portion		10,964		19,438
Total operating lease liabilities		$	18,432	$	28,100

Lease expense by lease type recognized during the years ended December 31, 2021, 2020 and 2019 was as follows:

	Year Ended December 31,
	2021			2020		2019
	(in thousands)
Operating lease cost	$	8,748		$	8,838	$	9,804
Variable lease cost		1,600			2,285		2,675
Short-term lease cost		101			74		438
Sublease income		(234	)		-		-
	$	10,215		$	11,197	$	12,917

The Company made an accounting policy election not to apply the recognition requirements to short-term leases. The Company recognizes the lease payments for short-term leases as expense on a straight-line basis over the lease term, and variable lease payments in the period in which the obligation for those payments is incurred.

The minimum lease payments are expected to be as follows:

Years Ending December 31,	(In thousands)
2022	$	7,468
2023		7,643
2024		5,316
2025		-
2026		-
Thereafter		-
Total lease payments		20,427
Less imputed interest		(1,995	)
Present value of operating lease liabilities	$	18,432

The weighted average remaining lease term and weighted average discount rate of the operating leases are as follows:

		December 31, 2021
Weighted average remaining lease term in years		2.68
Weighted average discount rate		7.5%

The interest rate implicit in lease contracts is typically not readily determinable and as such, the Company uses its incremental borrowing rate based on the information available at the lease commencement date, which represents an internally developed rate that would be incurred to borrow, on a collateralized basis, over a similar term, an amount equal to the lease payments in a similar economic environment.

Supplemental disclosure of cash flow information related to the operating leases included in cash flows used by operating activities in the consolidated statements of cash flows is as follows:

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities	$	9,264	$	9,231	$	9,946

Right-of-use assets obtained in exchange for lease obligations:
Operating leases	$	—	$	—	$	872

Lease asset de-recognized upon lease cancellation
Operating leases	$	3,733	$	2,310	$	—

License Agreements

CyDex License Agreement

In September 2015, the Company and CyDex, a wholly owned subsidiary of Ligand Pharmaceuticals, Inc., amended and restated their existing commercial license agreement. Under the terms of the commercial license agreement as amended and restated, CyDex has granted to the Company an exclusive license to CyDex’s Captisol drug formulation technology and related intellectual property for the manufacture of pharmaceutical products incorporating brexanolone and the Company’s compound known as SAGE-689, and the development and commercialization of the resulting products for the treatment, prevention or diagnosis of any disease or symptom in humans or animals other than (i) the ocular treatment of any disease or condition with a formulation, including a hormone; (ii) topical ocular treatment of

inflammatory conditions; (iii) treatment and prophylaxis of fungal infections in humans; and (iv) any ocular treatment for retinal degeneration. The Company is required to pay a royalty to CyDex on sales of brexanolone and will be required to pay a royalty on any sales of SAGE-689, if such product candidate is successfully developed in the future. Royalty rates are in the low single digits based on levels of net sales. As of December 31, 2021, the Company has paid to CyDex $1.0 million for licensing fees, which was recorded as research and development expense.

Under the amended and restated license agreement with CyDex, the Company agreed to make milestone payments on the achievement of clinical development and regulatory milestones in the amount of up to $0.8 million in clinical milestones and up to $3.8 million in regulatory milestones for each of the first two fields with respect to brexanolone; up to $1.3 million in clinical milestones and up to $8.5 million in regulatory milestones for each of the third and fourth fields with respect to brexanolone; and up to $0.8 million in clinical milestones and up to $1.8 million in regulatory milestones for one field with respect to SAGE-689. As of December 31, 2021, the Company has recorded research and development expense and made cash payments of $3.7 million related to these clinical development and regulatory milestones and has recorded an intangible asset and made a cash payment of $3.0 million related to these regulatory milestones.

For the year ended December 31, 2019, the Company recorded an intangible asset of $3.0 million related to a regulatory milestone for the brexanolone program under the license agreement with CyDex and the amount was paid in cash.

For the year ended December 31, 2020, additional clinical development milestones were met for the brexanolone program under the license agreement with CyDex, and accordingly, the Company recorded research and development expense and accrued expenses totaling $1.3 million. The amount was paid in cash during the year ended December 31, 2021.

For the year ended December 31, 2021, a clinical development milestone was met related to SAGE-689 under the license agreement with CyDex, and accordingly, the Company recorded research and development expense and made a cash payment of $0.1 million.

University of California License Agreements

In October 2013, the Company entered into a non-exclusive license agreement with the Regents under which the Company was granted a non-exclusive license to certain clinical data and clinical material related to brexanolone for use in the development and commercialization of biopharmaceutical products in the licensed field, including status epilepticus and postpartum depression. In May 2014, the license agreement was amended to add the treatment of essential tremor to the licensed field of use, materials and milestone fee provisions of the agreement. The Company paid to the Regents clinical development milestones of $0.1 million, prior to December 31, 2015; no other milestones are outstanding under this non-exclusive license agreement. The Company is required to pay royalties of less than 1% on net sales for a period of fifteen years following the sale of the first product developed using the data and materials. The license will terminate on the earlier to occur of (i) 27 years after the effective date or (ii) 15 years after the last-derived product is first commercially sold.

In June 2015, the Company entered into an exclusive license agreement with the Regents whereby the Company was granted an exclusive license to certain patent rights related to the use of allopregnanolone to treat various diseases. In exchange for such license, the Company paid an upfront payment of $50,000 and will make payments of $15,000 for annual maintenance fees until the calendar year following the first sale, if any, of a licensed product. The Company is obligated to make milestone payments following the achievement of specified regulatory and sales milestones of up to $0.7 million and $2.0 million in the aggregate, respectively. The Company pays royalties at a low single digit percentage of net sales of ZULRESSO, subject to specified minimum annual royalty amounts. Unless terminated by operation of law or by acts of the parties under the terms of the agreement, the license agreement will terminate when the last-to-expire patents or last-to-be abandoned patent applications expire, whichever is later. As of December 31, 2021, the Company has recorded research and development expense and made cash payments of $0.3 million related to these regulatory and sales milestones; and has recorded an intangible asset and made a cash payment of $0.5 million related to these regulatory and sales milestones.

For the year ended December 31, 2019, the Company recorded an intangible asset of $0.5 million related to a regulatory milestone for the brexanolone program under the license agreements with the Regents and the amount was paid in cash.

For the years ended December 31, 2021 and 2020, the Company did not record any expense or make any milestone or royalty payments under the license agreements with the Regents.

Collaboration Agreements

12 Months Ended

Dec. 31, 2021

Shionogi Collaboration Agreement [Member]

Collaboration Agreement

6.	Collaboration Agreements

Shionogi

In June 2018, the Company entered into a strategic collaboration with Shionogi for the clinical development and commercialization of zuranolone for the treatment of major depressive disorder (“MDD”) and other potential indications in Japan, Taiwan and South Korea (the “Shionogi Territory”). In October 2018, the Company entered into a supply agreement with Shionogi for zuranolone clinical material.

Under the terms of the collaboration agreement, Shionogi is responsible for all clinical development and regulatory filings for zuranolone in MDD and other indications in the Shionogi Territory and would be responsible for commercialization in the Shionogi Territory, if zuranolone is successfully developed and obtains marketing approval in any of the countries within the Shionogi Territory. Shionogi was required to make an upfront payment to the Company of $90.0 million, and the Company will be eligible to receive additional payments of up to $485.0 million if certain regulatory and commercial milestones are achieved by Shionogi. The potential future milestone payments include up to $70.0 million for the achievement of specified regulatory milestones, up to $30.0 million for the achievement of specified commercialization milestones, and up to $385.0 million for the achievement of specified net sales milestones. The Company is eligible to receive tiered royalties on sales of zuranolone in the Shionogi Territory, if development efforts are successful, with tiers averaging in the low to mid-twenty percent range, subject to other terms of the agreement. Shionogi has also granted to the Company certain rights to co-promote zuranolone in Japan. The Company maintains exclusive rights to develop and commercialize zuranolone outside of the Shionogi Territory. The upfront cash payment and any payments for milestones and royalties are non-refundable and non-creditable. Due to the uncertainty of pharmaceutical development and the high historical failure rates generally associated with drug development, the Company may not receive any milestone payments or any royalty payments from Shionogi.

The Company concluded that Shionogi meets the definition to be accounted for as a customer because the Company is delivering intellectual property and know-how rights for the zuranolone program in support of territories in which the parties are not jointly sharing the risks and rewards. In addition, the Company determined that the Shionogi collaboration met the requirements to be accounted for as a contract, including that it was probable that the Company will collect the consideration to which the Company was entitled in exchange for the goods or services that will be delivered to Shionogi.

In determining the appropriate amount of revenue to be recognized under Topic 606, the Company performed the following steps: (i) identified the promised goods or services in the contract; (ii) determined whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measured the transaction price, including the constraint on variable consideration; (iv) allocated the transaction price to the performance obligations; and (v) recognized revenue when (or as) the Company satisfied each performance obligation.

The Company determined that the performance obligations in the Shionogi collaboration agreement included the license to zuranolone and the supply of certain materials during the clinical development phase, which includes the supply of API. The performance obligation related to the license to zuranolone was determined to be distinct from other performance obligations and therefore was a separate performance obligation for which control was transferred upon signing. The obligation to provide certain clinical materials, including API for use during the development period, was determined to be a separate performance obligation. Given that Shionogi is not obligated to purchase any minimum amount or quantities of commercial API, the supply of API to Shionogi for commercial use was determined to be an option for Shionogi, rather than a performance obligation of the Company at contract inception and will be accounted for if and when exercised. The Company also determined that there was no separate material right in connection with the supply of API for commercial use as the expected pricing was not at a discount. Given this fact pattern, the Company has concluded the agreement has two performance obligations.

Under the clinical supply agreement, the Company will manufacture and supply to Shionogi (i) clinical quantities of API reasonably required by Shionogi for the development of licensed products in the Shionogi territory under the collaboration and license agreement and (ii) quantities of drug product reasonably required for use by Shionogi in Phase 1 clinical trials of zuranolone in the Shionogi territory under the collaboration and license agreement, in the quantities agreed to by the parties. Collaboration revenue from the clinical supply agreement, which excludes the $90.0 million upfront payment, pertains to the clinical material sold under the terms of the clinical supply agreement. The Company records the costs related to the clinical supply agreement in research and development expense on its consolidated statements of operations and comprehensive income (loss). For the years ended December 31, 2021 and 2020, the Company recognized no collaboration revenue from the Company’s agreement with Shionogi.

The Company completed the evaluation of the standalone selling prices of each of the performance obligations and determined that the standalone selling price of the license performance obligation was $90.0 million. The Company recognized the transaction price allocated to the license performance obligation of $90.0 million as revenue during the quarter upon delivery of the license to Shionogi and resulting ability of Shionogi to use and benefit from the license, which was in the three months ended June 30, 2018. The remaining transaction price related to the performance obligation for the supply of certain clinical material is not significant. The potential milestone payments that the Company is eligible to receive were excluded from the transaction price, as all milestone amounts were fully constrained based on the probability of achievement. The Company will re-evaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, adjust its estimate of the transaction price.

Biogen

In November 2020, the Company entered into the Biogen Collaboration Agreement to jointly develop and commercialize SAGE-217 products for MDD, PPD and other disorders and SAGE-324 products for essential tremor and other disorders. Concurrently, the Company also entered into a stock purchase agreement with BIMA (the “Biogen Stock Purchase Agreement”) to purchase shares of the Company’s common stock. The Biogen Collaboration Agreement became effective on December 28, 2020 (the “Effective Date”).

Under the terms of the Biogen Collaboration Agreement, the Company granted Biogen co-exclusive licenses to develop and commercialize SAGE-217 products and SAGE-324 products (each, a “Product Class” and together, the “Licensed Products”) in the U.S., an exclusive license to develop and commercialize SAGE-217 products in all countries of the world other than the U.S. and the Shionogi Territory, and an exclusive license to develop and commercialize SAGE-324 products in all countries of the world other than the U.S. The Company refers to the territories outside the U.S. to which Biogen has rights under the Biogen Collaboration Agreement with respect to the applicable Licensed Product as the “Biogen Territory”.

In connection with the effectiveness of the Biogen Collaboration Agreement and the closing of the sale of shares to BIMA in December 2020, the Company received $1.5 billion in consideration, comprised of an upfront payment of $875.0 million and the $650.0 million purchase price for 6,241,473 newly issued shares of the Company’s common stock (the “Biogen Shares”). As a result of the purchase of the Biogen Shares, Biogen has become a related party of the Company.

The Company is eligible to receive additional payments of up to $1.6 billion if certain regulatory and commercial milestones are achieved. The potential future milestone payments for SAGE-217 products include up to $475.0 million for the achievement of specified regulatory and commercial milestones and up to $300.0 million for the achievement of specified net sales milestones. The potential future milestone payments for SAGE-324 products include up to $520.0 million for the achievement of specified regulatory and commercial milestones and up to $300.0 million for the achievement of specified net sales milestones. The Company is also eligible to receive tiered royalties on net sales of SAGE-217 products and SAGE-324 products in the Biogen Territory at percentage rates ranging from the high teens to low twenties.

Due to the uncertainty of pharmaceutical development and the high historical failure rates generally associated with drug development, the Company may never receive any milestone payments or any royalty payments under the Biogen Collaboration Agreement.

Development and commercialization activities in the U.S. will be conducted pursuant to plans agreed to by the Company and Biogen and overseen by a joint steering committee that will consist at all times of an equal number of representatives of each party. The Company and Biogen will share equally in the costs for development and commercialization, as well as the profits and losses, in the U.S., subject to the Company’s opt-out right described below. Biogen will be solely responsible for all development activities and costs related to any development and commercialization of SAGE-217 products and SAGE-324 products for the Biogen Territory, and the Company will receive royalties on any sales in the Biogen Territory, as mentioned above.

The Company will supply API and bulk drug product for the Biogen Territory and API and final drug product for the U.S. to support development and commercialization activities. Biogen has the right to assume manufacturing responsibilities for API for the Biogen Territory at any time during the term of the agreement and will, within a reasonable period of time after the Effective Date, assume manufacturing responsibility for bulk drug product for the Biogen Territory.

Unless terminated earlier, the Biogen Collaboration Agreement will continue on a Licensed Product-by-Licensed Product and country-by-country basis until the date on which (a) in any country in the Biogen Territory, the royalty term has expired for all Licensed Products in a Product Class in such country, and (b) for the U.S., the parties agree to permanently cease to commercialize all Licensed Products in a Product Class. Biogen also has the right to terminate the Biogen Collaboration Agreement for convenience in its entirety, on a Product Class-by-Product Class basis or as to a particular region, upon advance written notice. The Company has an opt-out right to convert the co-exclusive licenses in the U.S. to an exclusive license to Biogen on a Product Class-by-Product Class basis. Following the exercise of the opt-out right, the Company would no longer share equally in the profits and losses in the U.S. and would be entitled to receive certain royalty payments at percentage rates ranging from the high teens to low twenties and additional sales milestones.

The Company concluded that the Biogen Collaboration Agreement and the Biogen Stock Purchase Agreement should be combined and treated as a single arrangement for accounting purposes as the agreements were entered into contemporaneously and in contemplation of one another. The Company determined that the combined agreements had elements that were within the scope of Topic 606 and Topic 808.

As of the Effective Date, the Company identified the following promises in the Biogen Collaboration Agreement that were evaluated under the scope of Topic 606: delivery of (i) a co-exclusive license for SAGE-217 products in the U.S.; (ii) an exclusive license for SAGE-217 products in the Biogen Territory; (iii) a co-exclusive license for SAGE-324 products in the U.S.; (iv) an exclusive license for SAGE-324 products in the Biogen Territory; (v) the clinical manufacturing supply of API and bulk drug product for SAGE-217 products in the Biogen Territory; and (vi) the clinical manufacturing supply of API and bulk drug product for SAGE-324 products in the Biogen Territory.

The Company also evaluated whether certain options outlined within the Biogen Collaboration Agreement represented material rights that would give rise to a performance obligation and concluded that none of the options convey a material right to Biogen and therefore are not considered separate performance obligations within the Biogen Collaboration Agreement.

The Company assessed the above promises and determined that the co-exclusive licenses for SAGE-217 products and SAGE-324 products in the U.S. are reflective of a vendor-customer relationship and therefore represent performance obligations within the scope of Topic 606. The co-exclusive license for SAGE-217 products and SAGE-324 products in the U.S. are considered functional intellectual property and distinct from other promises under the contract. The exclusive licenses for SAGE-217 products and SAGE-324 products in the Biogen Territory are considered functional licenses that are distinct in the context of the Biogen Collaboration Agreement as Biogen can benefit from the licenses on its own or together with other readily available resources. As the co-exclusive licenses in the U.S. and the exclusive licenses in the Biogen Territory are delivered at the same time, they are considered one performance obligation at contract inception. The

clinical manufacturing supply of API and bulk drug product for SAGE-217 products and SAGE-324 products for the Biogen Territory are considered distinct in the context of the Biogen Collaboration Agreement as Biogen can benefit from the manufacturing services together with the licenses transferred by the Company at the inception of the agreement. Therefore, each represents a separate performance obligation within a contract with a customer under the scope of Topic 606 at contract inception.

The Company considers the collaborative activities associated with the co-development, co-commercialization, and co-manufacturing of SAGE-217 products and SAGE-324 products in the U.S. to be separate units of account within the scope of Topic 808 as the Company and Biogen are both active participants in the development and commercialization activities and are exposed to significant risks and rewards that are dependent on the development and commercial success of the activities in the arrangement. The Company has determined that the supply of API and bulk drug product for the Biogen Territory and API and final drug product for the U.S. to Biogen will be classified as collaboration revenue – related party in the consolidated statements of operations and comprehensive income (loss). During the year ended December 31, 2021, no collaboration revenue – related party was recognized related to the Biogen Collaboration Agreement.

Payments to or reimbursements from Biogen related to the co-development, co-commercialization, and co-manufacturing activities and the agreement of the parties to share equally the cost of these activities will be accounted for as an increase to or reduction of research and development expenses or selling, general and administrative expenses, depending on the nature of the activity.

During the year ended December 31, 2021, the Company recorded a net reimbursement of $91.1 million for the amounts due from Biogen as a reduction of the related operating expense categories in the consolidated statement of operations and comprehensive income (loss). As of December 31, 2021, the Company recorded a Collaboration Receivable – Related Party of $18.5 million in the consolidated balance sheet for the amounts due for the three months ended December 31, 2021. During the year ended December 31, 2021, no payments were made to Biogen and the Company received $72.6 million from Biogen for the amounts due for the nine months ended September 30, 2021.

The following table summarizes expenses related to the Biogen Collaboration Agreement that were incurred by the Company and the related reimbursement from Biogen, reflected by category of operating expenses:

	Year Ended December 31,
	2021
	(in thousands)
Expenses related to the Biogen Collaboration Agreement incurred by Sage	$	193,776
Net reimbursement from Biogen reflected in the consolidated statement of operations and comprehensive loss:
Research and development expenses		(79,848	)
Selling, general and administrative expenses		(11,282	)
		(91,130	)
Total net expenses related to the Biogen Collaboration Agreement in the consolidated statement of operations and comprehensive income (loss)	$	102,646

The Company determined the transaction price under Topic 606 at the inception of the Biogen Collaboration Agreement to be $1.1 billion, consisting of the upfront payment of $875.0 million plus $232.5 million in excess proceeds from the equity investment under the Biogen Stock Purchase Agreement, when measured at fair value, plus future variable consideration for manufacturing supply of clinical API and bulk drug product for the Biogen Territory. The amount of variable consideration related to the future manufacturing services was not material. The Company determined that any variable consideration related to clinical development and regulatory milestones is deemed to be fully constrained and therefore excluded from the transaction price due to the high degree of uncertainty and risk associated with these potential payments, as the Company determined that it could not assert that it was probable that a significant reversal in the amount

of cumulative revenue recognized will not occur. The Company also determined that royalties and sales milestones relate solely to the licenses of intellectual property and are therefore excluded from the transaction price under the sales- or usage-based royalty exception of Topic 606. Revenue related to these royalties and sales milestones will only be recognized when the associated sales occur, and relevant thresholds are met.

As noted above, the Company identified three performance obligations in the Biogen Collaboration Agreement: (i) the delivery of the co-exclusive licenses for SAGE-217 products and SAGE-324 products in the U.S. and the exclusive licenses for SAGE-217 products and SAGE-324 products in the Biogen Territory; (ii) the clinical manufacturing supply of API and bulk drug product for SAGE-217 products in the Biogen Territory; and (iii) the clinical manufacturing supply of the API and bulk drug product for SAGE-324 products in the Biogen Territory. The selling price of each performance obligation in the Biogen Collaboration Agreement was determined based on the Company’s SSP with the objective of determining the price at which it would sell such an item if it were to be sold regularly on a standalone basis. The Company allocated the variable consideration related to the manufacturing obligations to the future clinical supply of SAGE-217 products and SAGE 324 products in the Biogen Territory and the remaining fixed consideration to the license obligation. The variable consideration related to the manufacturing obligations was not material. As such, the entirety of the $1.1 billion fixed consideration of the transaction price has been allocated to the transfer of the co-exclusive licenses for SAGE-217 products and SAGE-324 products in the U.S. and the exclusive licenses for SAGE-217 products and SAGE-324 products in the Biogen Territory. The Company recognizes revenue for the license performance obligations at a point in time, that is upon transfer of the licenses to Biogen. As control of these licenses was transferred on the Effective Date and Biogen could begin to use and benefit from the licenses, the Company recognized $1.1 billion of license revenue during the year ended December 31, 2020 under the Biogen Collaboration Agreement. The Company will recognize revenue for the clinical manufacturing supply obligations at a point in time, that is upon the delivery of the supply to Biogen.

Accounting for the Biogen Stock Purchase Agreement

In connection with the execution of the Biogen Collaboration Agreement, the Company and BIMA entered into the Biogen Stock Purchase Agreement. Pursuant to the Biogen Stock Purchase Agreement, the Company sold the Biogen Shares to BIMA at a price of approximately $104.14 per share, which represented a 40 percent premium over the 30-day volume-weighted average share price as of the last trading day prior to the date the Biogen Collaboration Agreement and Biogen Stock Purchase Agreement were executed in November 2020, for aggregate consideration of $650.0 million. The sale of the shares to BIMA closed on December 31, 2020.

The Biogen Stock Purchase Agreement includes certain standstill provisions, lock-up restrictions, and a voting agreement with respect to the Biogen Shares. Pursuant to the terms of the Biogen Stock Purchase Agreement

, BIMA has agreed not to, and to cause its affiliates not to, directly or indirectly acquire the Company’s securities, seek or propose a tender or exchange offer or merger between the Company and Biogen, solicit proxies or consents with respect to any matter, or undertake other specified actions, in each case subject to specified conditions. The standstill restrictions terminate on the earliest of (i) a specified regulatory milestone under the Biogen Collaboration Agreement, (ii) the date one year following the termination of the Biogen Collaboration Agreement and (iii) the seventh anniversary of the Effective Date. BIMA has also agreed not to, and to cause its affiliates not to, sell or transfer any of the Biogen Shares for a period of eighteen months from the closing of the sale of the Biogen Shares, which expires June 30, 2022, and to limit sales and transfers of the Biogen Shares for an additional eighteen-month period, in each case subject to specified conditions and exceptions.

The Company determined the fair value of the common shares issued using an option pricing valuation model to take into consideration the holding period restrictions. The fair value of the Company’s common stock was considered a level 2 fair value measurement within the fair value hierarchy. The most significant assumptions within the model are the Company’s stock price, the term of the restrictions and the stock price volatility, which is based upon a blend of historical and implied volatility of the Company’s stock. Based on the fair value adjustments made by management, the fair value of the shares issued was determined to be $417.5 million, which was $232.5 million less than the proceeds received from BIMA for the issuance of the Company’s common stock under the Biogen Stock Purchase Agreement. As such, the $232.5 million in excess proceeds has been included in the $1.1 billion transaction price of the Biogen Collaboration Agreement determined above.

Preferred Stock

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Preferred Stock

7.	Preferred Stock

The Board of Directors of the Company (the “Board”) is authorized, without action by the stockholders, to designate and issue up to an aggregate of 5,000,000 shares of preferred stock in one or more series. The Board can designate the rights, preferences and privileges of the shares of each series and any of its qualifications, limitations or restrictions. The Board may authorize the issuance of preferred stock with voting or conversion rights that could adversely affect the voting power or other rights of the holders of common stock. As of December 31, 2021 and 2020, the Company had no shares of preferred stock issued or outstanding and preferred stock was classified as stockholders’ equity.

Common Stock

12 Months Ended

Dec. 31, 2021

Text Block [Abstract]

Common Stock

8.	Common Stock

As of December 31, 2021 and 2020, the Company authorized 120,000,000 shares of common stock with a par value of $0.0001 per share.

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the Board, if any. As of December 31, 2021 and 2020, no dividends have been declared.

On February 27, 2019, the Company completed the sale of 3,833,334 shares of its common stock at a price to the public of $150.00 per share, resulting in net proceeds to the Company of $560.9 million after deducting underwriting discounts and commissions and offering costs paid by the Company.

On December 31, 2020, the Company completed the sale of 6,241,473 shares of its common stock in a private placement to BIMA at a price of approximately $104.14 per share, resulting in aggregate gross proceeds to the Company of $650.0 million. For additional information, refer to Note 6, Collaboration Agreements.

As of December 31, 2021, the Company had received 3,033 shares of the Company’s common stock from a then-employee as consideration for exercises of stock options. The total cost of shares held in treasury at December 31, 2021 was $0.4 million.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

9.	Stock-Based Compensation

Equity Plans

On July 2, 2014, the stockholders of the Company approved the 2014 Stock Option and Incentive Plan (the “2014 Plan”), which became effective immediately prior to the completion of the Company’s IPO. The 2014 Plan provides for the grant of restricted stock awards, restricted stock units, incentive stock options and non-statutory stock options. The 2014 Plan replaced the Company’s 2011 Stock Option and Grant Plan (the “2011 Plan”). The Company no longer grants stock options or other awards under its 2011 Plan, but any stock options outstanding under the 2011 Plan remain outstanding and effective in accordance with their terms.

The 2014 Plan provides for an annual increase, to be added on the first day of each fiscal year, by up to 4% of the Company’s outstanding shares of common stock as of the last day of the prior year. On January 1, 2021, 2,332,336 shares of common stock, representing 4% of the Company’s outstanding shares of common stock as of December 31, 2020, were added to the 2014 Plan.

On December 15, 2016, the Board approved the 2016 Inducement Equity Plan (as amended and restated, the “2016 Plan”). The 2016 Plan provides for the grant of equity awards to individuals who have not previously been an employee or a non-employee director of the Company to induce them to accept employment and to provide them with a proprietary interest in the Company. On September 20, 2018, the Board amended the 2016 Plan to increase the total number of shares reserved for issuance by 1,200,000 shares.

Terms of equity grants, including vesting requirements, are determined by the Board or the Compensation Committee of the Board, subject to the provisions of the applicable plan. Stock options granted by the Company that are not performance-based are considered time-based because they vest based on the continued service of the grantee with the Company during a specified period following grant. These awards, when granted to employees, generally vest ratably over four years, with 25% vesting at the one-year anniversary. All stock option awards expire 10 years after the date of grant.

As of December 31, 2021, the total number of shares underlying outstanding awards under all equity plans was 8,539,537 and the total number of shares available for future issuance under all equity plans was 5,672,875 shares.

Restricted Stock Units

The table below summarizes activity relating to time-based restricted stock units and performance restricted stock units:

	Shares
Outstanding as of December 31, 2020		957,695
Granted		799,295
Vested		(302,661	)
Forfeited		(198,231	)
Outstanding as of December 31, 2021		1,256,098

At December 31, 2021, 1,256,098 time-based restricted stock units and performance restricted stock units were both outstanding and unvested, and the total unrecognized stock-based compensation expense related to these awards was $59.2 million.

Time-based restricted stock units

During the year ended December 31, 2017, the Company granted 32,500 time-based restricted stock units to certain employees of the Company. These time-based restricted stock units vested ratably over two years, with vesting of 50% at both the one-year and two-year anniversary of the grant date, which was in February 2018 and 2019, respectively. The fair value of the time-based restricted stock units that vested during the years ended December 31, 2019 and 2018 was $2.0 million and $2.6 million, respectively.

During the year ended December 31, 2020, the Company granted 550,890 time-based restricted stock units to certain employees of the Company. These time-based restricted stock units will vest over two years, with 25% vesting at the one-year anniversary of the grant date and 75% vesting at the two-year anniversary of the grant date, which was in April 2021 and will be in April 2022, respectively. During the year ended December 31, 2021, 113,941 time-based restricted stock units vested, and the fair value of the restricted stock units that vested was $8.8 million.

During the year ended December 31, 2021, the Company granted 268,119 time-based restricted stock units to certain employees of the Company. These time-based restricted stock units will vest ratably over four years, with 25% vesting at the one-year anniversary.

During the year ended December 31, 2019, the Company granted no time-based restricted stock units and no time-based restricted stock units vested during the year ended December 31, 2020.

Performance restricted stock units

During the year ended December 31, 2019, the Company granted 393,539 performance restricted stock units to employees of the Company. These performance restricted stock units are related to the achievement of certain clinical and regulatory development milestones related to product candidates and commercial milestones.

During the year ended December 31, 2020, the Company granted 471,386 performance restricted stock units to employees of the Company. These performance restricted stock units are related to the achievement of certain clinical and regulatory development milestones related to product candidates and commercial milestones.

During the year ended December 31, 2021, the Company granted 531,176 performance restricted stock units to employees of the Company. These performance restricted stock units are related to the achievement of certain clinical and regulatory development milestones related to product candidates and commercial milestones.

Recognition of stock-based compensation expense associated with performance restricted stock units commences when the performance condition is considered probable of achievement, using management’s best estimates, which consider the inherent risk and uncertainty regarding the future outcomes of the milestones.

As of December 31, 2021, 2020 and 2019, for performance restricted stock units that were outstanding, the achievement of the milestones that had not been met was considered not probable, and therefore no expense has been recognized related to these awards in the years ended December 31, 2021, 2020 and 2019, respectively.

During the year ended December 31, 2019, one milestone for outstanding performance restricted stock units was achieved. The fair value of the performance restricted stock units that vested upon achievement was $11.1 million and the Company recognized stock-based compensation expense related to this milestone of $10.9 million. 18% of the performance restricted stock units that were granted during the year ended December 31, 2019 included this milestone as a vesting condition.

No performance restricted stock units vested during the year ended December 31, 2020.

During the year ended December 31, 2021, two milestones for outstanding performance restricted stock units were achieved. For the first milestone that was met, the fair value of the performance restricted stock units that vested upon achievement was $6.1 million and the Company recognized stock-based compensation expense related to this milestone of $3.8 million. 39% of the performance restricted stock units that were granted during the year ended December 31, 2020 included this milestone as a vesting condition. For the second milestone that was met, the fair value of the performance restricted stock units that vested upon achievement was $3.4 million and the Company recognized stock-based compensation expense related to this milestone of $12.8 million. 38% of the performance restricted stock units that were granted during the year ended December 31, 2019 included this milestone as a vesting condition.

Stock Option Rollforward

The table below summarizes activity related to time-based and performance-based stock options:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2020		7,157,830		$	91.41		6.91	$	167,242
Granted		2,095,363		$	79.76
Exercised		(306,078	)	$	40.35
Forfeited		(1,663,676	)	$	117.80
Outstanding as of December 31, 2021		7,283,439		$	84.17		6.74	$	16,590
Vested and expected to vest as of December 31, 2021		6,220,652		$	84.00		6.37	$	16,493
Exercisable as of December 31, 2021		4,434,049		$	85.68		5.47	$	15,713

At December 31, 2021, the Company had unrecognized stock-based compensation expense related to its unvested time-based stock option awards of $86.0 million, which is expected to be recognized over the remaining weighted average vesting period of 2.62 years.

The intrinsic value of stock options exercised during the years ended December 31, 2021, 2020 and 2019 was $9.0 million, $2.1 million and $119.1 million, respectively.

Performance-Based Stock Options

Recognition of stock-based compensation expense associated with performance-based stock options commences when the performance condition is considered probable of achievement, using management’s best estimates, which consider the inherent risk and uncertainty regarding the future outcomes of the milestones.

As of December 31, 2021, 2020 and 2019, for performance-based stock option grants that were outstanding, the achievement of the milestones that had not been met was considered not probable, and therefore no expense has been recognized related to these awards in the years ended December 31, 2021, 2020 and 2019, respectively.

During the year ended December 31, 2021, in connection with the hiring of its chief executive officer, the Company granted to its chief executive officer 650,000 stock options to purchase shares of common stock that contain performance-based vesting criteria which will vest upon the achievement of certain regulatory and commercial milestones. During the years ended December 31, 2020 and 2019, the Company granted no stock options to employees to purchase shares of common stock that contain performance-based vesting criteria.

During the year ended December 31, 2019, one commercial milestone was achieved under performance-based stock options granted to employees. Stock options with this milestone were granted during the years ended December 31, 2018 and 2017, respectively. This milestone represented 20% and 33% of the performance-based stock option grants that were made during the years ended December 31, 2018 and 2017, respectively. During the year ended December 31, 2019, the Company recognized stock-based compensation expense related to this milestone of $16.3 million.

During the year ended December 31, 2020, no milestones were achieved under performance-based stock options granted to employees. During the year ended December 31, 2020, one milestone for performance-based stock option grants that were made during the year ended December 31, 2018 that had to be met by December 31, 2020 or else the stock option grants would be cancelled was not met, and accordingly, those stock option grants were cancelled. This milestone represented 19% of the performance-based stock option grants that were made during the year ended December 31, 2018. The Company recognized no stock-based compensation expense related to this milestone.

During the year ended December 31, 2021, no milestones were achieved under performance-based stock options granted to employees.

During the year ended December 31, 2021, one milestone for performance-based stock option grants that were made during the year ended December 31, 2017 that had to be met by December 31, 2021 or else the stock option grants would be cancelled was not met, and accordingly, those stock option grants were cancelled. This milestone represented 34% of the performance-based stock option grants that were made during the year ended December 31, 2017. The Company recognized no stock-based compensation expense related to this milestone.

During the year ended December 31, 2021, three milestones for performance-based stock option grants that were made during the year ended December 31, 2018 that had to be met by December 31, 2021 or else the stock option grants would be cancelled were not met, and accordingly, those stock option grants were cancelled. These milestones represent 41% of the performance-based stock option grants that were made during the year ended December 31, 2018. The Company recognized no stock-based compensation expense related to these milestones.

As of December 31, 2021, 684,010 performance-based stock options were both outstanding and unvested, the total unrecognized stock-based compensation expense related to these awards was $10.8 million and the timing of recognition of this stock-based compensation expense is subject to judgment of the Company as to when the performance conditions are considered probable of being achieved.

Stock-Based Compensation Expense

Stock-based compensation expense recognized during the years ended December 31, 2021, 2020 and 2019 was as follows:

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Research and development	$	49,746	$	42,370	$	62,931
Selling, general and administrative		54,883		51,836		90,300
Restructuring		—		1,788		—
	$	104,629	$	95,994	$	153,231

Stock-based compensation expense recognized during the years ended December 31, 2021, 2020 and 2019 by award type was as follows:

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Stock options	$	78,516	$	90,064	$	140,517
Restricted stock units		25,375		4,904		10,992
Employee stock purchase plan		738		1,026		1,722
	$	104,629	$	95,994	$	153,231

The stock-based compensation expense recorded for the restructuring in the year ended December 31, 2020 is the incremental amount related to modifying the exercise period for outstanding, vested stock option grants that had been made to employees whose employment was terminated in the restructuring.

For stock option awards, the fair value is estimated at the grant date using the Black-Scholes option-pricing model, taking into account the terms and conditions upon which stock options are granted. The fair value of the stock options is amortized on a straight-line basis for stock option awards to employees, non-employee directors and non-employee consultants over the requisite service period of the awards.

The weighted average grant date fair value per share of stock options granted under the Company’s stock option plans during the years ended December 31, 2021, 2020 and 2019 was $51.87, $37.53 and $82.39, respectively.

The fair value of each stock option granted under the Company’s equity plans has been calculated on the date of grant using the following weighted average assumptions:

	Year Ended December 31,
	2021			2020			2019
Expected dividend yield		0	%		0	%		0	%
Expected volatility		75.92	%		77.86	%		71.34	%
Risk-free interest rate		0.63	%		0.97	%		2.21	%
Expected term	5.92 years			5.98 years			6.05 years

Expected dividend yield: the Company has not paid, and does not anticipate paying, any dividends in the foreseeable future.

Risk-free interest rate: the Company determined the risk-free interest rate by using a weighted average equivalent to the expected term based on the U.S. Treasury yield curve in effect as of the date of grant.

Expected volatility: beginning in 2016, the Company estimated its expected volatility in the Black-Scholes calculations using a weighted average of the historical volatility of a group of publicly-traded peer companies and the historical volatility of its common stock and expected to continue to do so until it had adequate historical data regarding the volatility of its common stock price for the duration of the expected term. Effective January 1, 2020, the Company began using the historical volatility of only its common stock, as there is adequate historical data for the duration of the expected term.

Expected term (in years): the expected term represents the period that the Company’s stock option grants are expected to be outstanding. The expected term of the stock options granted to employees, non-employee directors and non-employee consultants by the Company has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” stock options. Under this approach, the weighted average expected life is presumed to be the average of the vesting term and the contractual term of the stock option.

Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates. The Company estimates forfeitures based on historical terminations. For the years ended December 31, 2021, 2020 and 2019, the weighted-average forfeiture rates were 16.7%, 20.6% and 13.7%, respectively.

2014 Employee Stock Purchase Plan

On July 2, 2014, the Company’s stockholders approved the 2014 Employee Stock Purchase Plan (the “ESPP”), which had been previously approved by the Board. The ESPP became effective upon the completion of the IPO. A total of 282,000 shares of common stock were authorized for issuance under the ESPP. As of December 31, 2021, 224,638 shares have been issued and 57,362 shares are available for issuance under the ESPP. At December 31, 2021, accrued expenses includes $0.3 million of stock-based compensation expense related to an enrollment period for which the related shares had not been issued as of December 31, 2021.

Net Income (Loss) Per Share

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Net Income (Loss) Per Share

10.	Net Income (Loss) Per Share

Basic and diluted net income (loss) per share was calculated as follows for the years ended December 31, 2021, 2020 and 2019:

	Year Ended December 31,
	2021			2020		2019
Basic net income (loss) per share:
Numerator:
Net income (loss) (in thousands)	$	(457,892	)	$	606,073	$	(680,238	)
Denominator:
Weighted average common stock outstanding —basic		58,670,230			51,983,188		50,833,837

Effect of dilutive securities:
Stock options		—			721,791		—
Restricted stock units		—			292,241		—
Employee Stock Purchase Plan		—			5,895		—
Total dilutive securities		—			1,019,927		—

Weighted average common stock outstanding —diluted		58,670,230			53,003,115		50,833,837
Net income (loss) per share—basic	$	(7.80	)	$	11.66	$	(13.38	)
Net income (loss) per share—diluted	$	(7.80	)	$	11.43	$	(13.38	)

The following common stock equivalents outstanding as of December 31, 2021, 2020 and 2019 were excluded from the calculation of diluted net loss per share for the periods presented because including them would have been anti-dilutive:

	Year Ended December 31,
	2021		2020		2019
Stock options		6,599,429		4,781,737		7,677,518
Restricted stock units		563,334		—		—
Employee stock purchase plan		23,625		—		33,429
		7,186,388		4,781,737		7,710,947

Stock options and restricted stock units that are outstanding and contain performance-based vesting criteria for which the performance conditions have not been met are excluded from the calculation of common stock equivalents outstanding.

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

11.	Income Taxes

Income (loss) before income tax expense consists of the following:

	Year Ended December 31,
	2021			2020			2019
	(in thousands)
Domestic	$	(457,693	)	$	639,986		$	(634,289	)
Foreign		(199	)		(33,913	)		(45,949	)
	$	(457,892	)	$	606,073		$	(680,238	)

There is no current or deferred provision for income taxes because the Company has historically incurred and utilized operating losses prior to the year ended December 31, 2021. As of December 31, 2021, the Company continues to maintain a full valuation allowance against its net deferred tax assets. The reported amount of income tax expense for the

years differs from the amount that would result from applying domestic federal statutory tax rates to pretax losses primarily because of changes in the valuation allowance.

A reconciliation of the U.S. statutory rate to the Company’s effective tax rate is as follows:

	Year Ended December 31,
	2021			2020			2019
Tax due at statutory rate		21.0	%		21.0	%		21.0	%
State taxes, net of federal		1.9			5.7			2.8
Biogen transaction-related items		—			(10.1	)		—
Stock-based compensation		(5.2	)		0.9			1.4
Foreign rate differential		—			1.2			(1.6	)
Federal and state credits		3.5			(1.5	)		2.4
Change in valuation allowance		(20.7	)		(17.6	)		(25.8	)
Other		(0.5	)		0.4			(0.2	)
		0.0	%		0.0	%		0.0	%

For the year ended December 31, 2021, the impact from stock-based compensation on the Company’s effective tax rate was primarily caused by shortfalls related to exercises and cancellations of non-qualified stock options.

For the year ended December 31, 2020, the Biogen transaction-related items consisted primarily of the excess proceeds from the equity investment under the Biogen Stock Purchase Agreement.

Significant components of the Company’s net deferred tax assets at December 31, 2021 and 2020 are as follows:

	December 31,
	2021			2020
	(in thousands)
Net operating losses	$	305,824		$	222,607
Capitalized start-up costs		735			873
Tax credit carryforwards		106,176			90,460
Accrued expenses		6,684			3,157
Depreciation and amortization		1,401			1,614
Stock-based compensation		49,281			56,520
Right of use asset		(3,702	)		(5,981	)
Lease liability		4,236			6,705
Other		(31	)		148
Total net deferred tax asset before valuation allowance		470,604			376,103
Valuation allowance		(470,604	)		(376,103	)
Net deferred tax asset	$	—		$	—

As of December 31, 2021, the Company had federal net operating loss carryforwards of $1.3 billion, of which $30.2 million begin to expire in 2033 and the remainder do not expire but are subject to 80% limitation. As of December 31, 2021, the Company had state net operating loss carryforwards of $584.8 million that begin to expire in 2031. As of December 31, 2021, the Company had federal and state research and development tax credits carryforwards of $56.9 million and $11.6 million, respectively, which begin to expire in 2031 and 2028, respectively. As of December 31, 2021, the Company had federal orphan drug tax credit carry forwards of $40.1 million, which begin to expire in 2034.

As of December 31, 2021, net deferred tax assets before the valuation allowance increased $94.5 million, primarily due to the increase of federal and state net operating loss carryforwards due to the loss generated for the year ended December 31, 2021. This increase in net deferred tax assets was offset by a corresponding increase in the valuation allowance.

Management of the Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which are comprised principally of federal and state net operating loss and tax credit carryforwards. 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 federal and state deferred tax assets. Accordingly, a full valuation allowance of $470.6 million and $376.1 million has been established at December 31, 2021 and 2020, respectively. The valuation allowance increased by $94.5 million, decreased by $107.2 million and increased by $174.9 million for the years ended December 31, 2021, 2020 and 2019, respectively, primarily due to generation or utilization of net operating losses.

Pursuant to Section 382 of the Internal Revenue Code, and similar state tax law, certain substantial changes in the Company’s ownership may result in a limitation on the amount of net operating loss and tax credit carryforwards that may be used in future years. Utilization of the net operating loss and tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended, due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of net operating loss and tax credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company completed a Section 382 study through December 31, 2020. Based on the study, the Company underwent two ownership changes for Section 382 purposes which occurred on March 11, 2014 and December 31, 2015. As a result of the ownership changes, the Company’s net operating loss and tax credit carryforwards as of the ownership change dates are subject to limitation under Section 382; however, these limitations are not expected to cause any of the impacted net operating loss and tax credit carryforwards to expire unused. Any net operating losses or tax credits generated after the December 2015 change are not subject to this annual limitation. However, subsequent ownership changes, as defined by Section 382, may potentially further limit the amount of net operating loss and tax credit carryforwards that could be utilized to offset future taxable income and tax.

The Company applies the authoritative guidance on accounting for and disclosure of uncertainty in tax positions, which requires the Company to determine whether a tax position of the Company is more likely than not to be sustained upon examination, including resolution of any related appeals of litigation processes, based on the technical merits of the position. For tax positions meeting the more likely than not threshold, the tax amount recognized in the financial statements is reduced by the largest benefit that has a greater than fifty percent likelihood of being realized upon the ultimate settlement with the relevant taxing authority.

The following table reconciles the beginning and ending amounts of gross unrecognized tax benefits, excluding interest and penalties, if any, for the year ended December 31, 2021:

	2021
	(in thousands)
Balance as of January 1	$	-
Increases related to current year tax positions		396
Increases related to prior year tax positions		5,688
Balance as of December 31	$	6,084

For the years ended December 31, 2020 and 2019, there were no gross unrecognized tax benefits.

For the year ended December 31, 2021, the increases in unrecognized tax benefits related to current year and prior year tax positions primarily related to the Company’s federal and state tax credits.

The Company’s policy is to record interest and penalties related to income taxes as part of the tax provision. As of December 31, 2021 and 2020, the Company had no accrued interest or penalties related to income taxes and no amounts have been recognized in the Company’s statements of operations and comprehensive income (loss) for the years ended December 31, 2021, 2020 and 2019.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal, state and foreign jurisdictions, where applicable.

There are currently no pending tax examinations, and the Company’s tax returns are generally open under statute from 2018 to the present. Tax attributes such as net operating losses and tax credits generated prior to 2018 and utilized in open years may still be adjusted upon examination.

- 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Employee Benefit Plan

12 Months Ended

Dec. 31, 2021

Postemployment Benefits [Abstract]

Employee Benefit Plan

12.	Employee Benefit Plan

The Company maintains a 401(k) profit sharing plan (the “401(k) Plan”) for its employees. Each employee may elect to contribute a portion of his or her compensation to the 401(k) Plan, subject to annual limits established by the Internal Revenue Service. For the years ended December 31, 2021, 2020 and 2019, the Company matched 50% of eligible contributions to the 401(k) Plan up to 6% of employee contributions. For the years ended December 31, 2021, 2020 and 2019 the Company contributed $1.8 million, $2.2 million and $3.6 million, respectively, to the 401(k) Plan.

Restructuring

12 Months Ended

Dec. 31, 2021

Restructuring And Related Activities [Abstract]

Restructuring

13.	Restructuring

In April 2020, the Company announced a restructuring plan to enable the Company to advance its corporate strategy and pipeline that included the elimination of approximately 53% of the Company’s workforce. The workforce reduction primarily affected the ZULRESSO commercial operation and related selling, general and administrative support functions. During the year ended December 31, 2020, the Company recorded $27.7 million of expense for restructuring, primarily for one-time termination benefits to the affected employees, primarily for cash payments of severance, healthcare benefits and outplacement assistance. Substantially all of the accrued restructuring charges were paid in cash as of December 31, 2020. As of December 31, 2021, the balance of the restructuring accrual was zero.

Restructuring activity during the years ended December 31, 2021 and December 31, 2020 was as follows:

	Restructuring accrual
	(in thousands)
Balance as of January 1, 2020	$	-
Restructuring expenses incurred		27,743
Cash paid		(25,102	)
Non-cash activity		(2,438	)
Balance as of December 31, 2020		203
Cash paid		(203	)
Balance as of December 31, 2021	$	-

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Risks and Uncertainties

Going Concern

Basis of Presentation

Principles of Consolidation

The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. Intercompany accounts and transactions have been eliminated.

Use of Estimates

Cash Equivalents

Marketable Securities

Accounts Receivable

Inventory

Property and Equipment

Leases

Impairment of Long-Lived Assets

Cost of Goods Sold

Research and Development Costs and Accruals

Stock-Based Compensation

Treasury Stock

The Company records treasury stock at cost. Treasury stock consists of shares of the Company’s common stock received from a then-employee as consideration for exercises of stock options.

Basic and Diluted Net Loss Per Share

Basic and Diluted Net Income (Loss) Per Share

Concentration of Credit Risk and of Significant Suppliers

Income Taxes

Fair Value Measurements

Level 1	—	Quoted market prices in active markets for identical assets or liabilities.

Level 2	—	Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3	—	Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

Segment Data

Comprehensive Loss

Comprehensive Income (Loss)

Revenue Recognition

Collaboration and License Revenue

Product Revenue, Net

As of December 31, 2021 and 2020, the Company had not provided any allowance for bad debts against the trade accounts receivable, and the amount of trade accounts receivable was not significant.

Collaborative Arrangements

Recently Issued Accounting Pronouncements

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Summary of Company's Cash Equivalents and Marketable Securities

The following tables summarize the Company’s cash equivalents and marketable securities as of December 31, 2021 and 2020:

	December 31, 2021
	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Cash equivalents	$	294,233	$	290,234	$	3,999	$	—
Total cash equivalents		294,233		290,234		3,999		—
Marketable securities:
U.S. government securities		324,532		—		324,532		—
U.S. corporate bonds		627,780		—		627,780		—
International corporate bonds		236,812		—		236,812		—
U.S. commercial paper		80,176		—		80,176		—
International commercial paper		142,335		—		142,335		—
U.S. municipal securities		36,428		—		36,428		—
Total marketable securities		1,448,063		—		1,448,063		—
	$	1,742,296	$	290,234	$	1,452,062	$	—

	December 31, 2020
	Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(in thousands)
Cash equivalents:
Cash equivalents	$	1,661,082	$	1,637,609	$	23,473	$	—
Total cash equivalents		1,661,082		1,637,609		23,473		—
Marketable securities:
U.S. government securities		160,588		—		160,588		—
U.S. corporate bonds		123,107		—		123,107		—
International corporate bonds		57,676		—		57,676		—
U.S. commercial paper		45,963		—		45,963		—
International commercial paper		51,133		—		51,133		—
Total marketable securities		438,467		—		438,467		—
	$	2,099,549	$	1,637,609	$	461,940	$	—

Summary of Gross Unrealized Gains and Losses of Marketable Securities

The following tables summarize the gross unrealized gains and losses of the Company’s marketable securities as of December 31, 2021 and 2020:

	December 31, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Fair Value
	(in thousands)
Assets:
U.S. government securities	$	325,514	$	—	$	(982	)	$	—	$	324,532
U.S. corporate bonds		628,836		27		(1,083	)		—		627,780
International corporate bonds		237,303		—		(491	)		—		236,812
U.S. commercial paper		80,194		—		(18	)		—		80,176
International commercial paper		142,358		—		(23	)		—		142,335
U.S. municipal securities		36,518		—		(90	)		—		36,428
	$	1,450,723	$	27	$	(2,687	)	$	—	$	1,448,063

	December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Credit Losses		Fair Value
	(in thousands)
Assets:
U.S. government securities	$	160,589	$	11	$	(12	)	$	—	$	160,588
U.S. corporate bonds		122,882		240		(15	)		—		123,107
International corporate bonds		57,485		200		(9	)		—		57,676
U.S. commercial paper		45,963		—		—			—		45,963
International commercial paper		51,133		—		—			—		51,133
	$	438,052	$	451	$	(36	)	$	—	$	438,467

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Summary of Property and Equipment, Net

Property and equipment, net consists of the following:

	December 31,			December 31,
	2021			2020
	(in thousands)
Computer hardware and software	$	1,391		$	2,758
Furniture and equipment		1,208			1,865
Leasehold improvements		5,390			9,220
		7,989			13,843
Less: Accumulated depreciation		(4,973	)		(7,088	)
	$	3,016		$	6,755

Summary of Accrued Expenses

Accrued expenses consist of the following:

	December 31,		December 31,
	2021		2020
	(in thousands)
Accrued research and development costs	$	39,147	$	34,398
Employee-related		18,618		14,769
Professional services		8,893		5,184
Other		617		500
	$	67,275	$	54,851

Leases, Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Schedule of Amount of Operating Leases

The following table shows the amounts of operating leases in the balance sheets as of December 31, 2021 and 2020:

		December 31,
Balance sheet location	Balance sheet caption	2021		2020
		(in thousands)
Assets
Right-of-use operating asset	Right-of-use operating asset	$	16,109	$	25,064

Liabilities
Current operating lease liabilities	Operating lease liability, current portion		7,468		8,662
Long-term operating lease liabilities	Operating lease liability, net of current portion		10,964		19,438
Total operating lease liabilities		$	18,432	$	28,100

Schedule of Lease Expense by Lease Type Recognized

Lease expense by lease type recognized during the years ended December 31, 2021, 2020 and 2019 was as follows:

	Year Ended December 31,
	2021			2020		2019
	(in thousands)
Operating lease cost	$	8,748		$	8,838	$	9,804
Variable lease cost		1,600			2,285		2,675
Short-term lease cost		101			74		438
Sublease income		(234	)		-		-
	$	10,215		$	11,197	$	12,917

Schedule of Minimum Lease Payments

The minimum lease payments are expected to be as follows:

Years Ending December 31,	(In thousands)
2022	$	7,468
2023		7,643
2024		5,316
2025		-
2026		-
Thereafter		-
Total lease payments		20,427
Less imputed interest		(1,995	)
Present value of operating lease liabilities	$	18,432

Schedule of Weighted Average Remaining Lease Term and Weighted Average Discount Rate of Our Operating Leases

The weighted average remaining lease term and weighted average discount rate of the operating leases are as follows:

		December 31, 2021
Weighted average remaining lease term in years		2.68
Weighted average discount rate		7.5%

Schedule of Supplemental Disclosure of Cash Flow Information Related to Operating Leases

Supplemental disclosure of cash flow information related to the operating leases included in cash flows used by operating activities in the consolidated statements of cash flows is as follows:

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Cash paid for amounts included in the measurement of lease liabilities	$	9,264	$	9,231	$	9,946

Right-of-use assets obtained in exchange for lease obligations:
Operating leases	$	—	$	—	$	872

Lease asset de-recognized upon lease cancellation
Operating leases	$	3,733	$	2,310	$	—

Collaboration Agreements (Tables)

12 Months Ended

Dec. 31, 2021

Collaboration Agreement [Abstract]

Summary of Operating Expenses Category Related to Collaboration Agreement

	Year Ended December 31,
	2021
	(in thousands)
Expenses related to the Biogen Collaboration Agreement incurred by Sage	$	193,776
Net reimbursement from Biogen reflected in the consolidated statement of operations and comprehensive loss:
Research and development expenses		(79,848	)
Selling, general and administrative expenses		(11,282	)
		(91,130	)
Total net expenses related to the Biogen Collaboration Agreement in the consolidated statement of operations and comprehensive income (loss)	$	102,646

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Activity Relating to Restricted Stock Units

The table below summarizes activity relating to time-based restricted stock units and performance restricted stock units:

	Shares
Outstanding as of December 31, 2020		957,695
Granted		799,295
Vested		(302,661	)
Forfeited		(198,231	)
Outstanding as of December 31, 2021		1,256,098

Summary of Activity Relating to Time Based and Performance Based Stock Options

The table below summarizes activity related to time-based and performance-based stock options:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2020		7,157,830		$	91.41		6.91	$	167,242
Granted		2,095,363		$	79.76
Exercised		(306,078	)	$	40.35
Forfeited		(1,663,676	)	$	117.80
Outstanding as of December 31, 2021		7,283,439		$	84.17		6.74	$	16,590
Vested and expected to vest as of December 31, 2021		6,220,652		$	84.00		6.37	$	16,493
Exercisable as of December 31, 2021		4,434,049		$	85.68		5.47	$	15,713

Summary of Stock-Based Compensation Expense Recognized

Stock-based compensation expense recognized during the years ended December 31, 2021, 2020 and 2019 was as follows:

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Research and development	$	49,746	$	42,370	$	62,931
Selling, general and administrative		54,883		51,836		90,300
Restructuring		—		1,788		—
	$	104,629	$	95,994	$	153,231

Summary of Stock-Based Compensation Expense by Award Type

Stock-based compensation expense recognized during the years ended December 31, 2021, 2020 and 2019 by award type was as follows:

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Stock options	$	78,516	$	90,064	$	140,517
Restricted stock units		25,375		4,904		10,992
Employee stock purchase plan		738		1,026		1,722
	$	104,629	$	95,994	$	153,231

Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted

The fair value of each stock option granted under the Company’s equity plans has been calculated on the date of grant using the following weighted average assumptions:

	Year Ended December 31,
	2021			2020			2019
Expected dividend yield		0	%		0	%		0	%
Expected volatility		75.92	%		77.86	%		71.34	%
Risk-free interest rate		0.63	%		0.97	%		2.21	%
Expected term	5.92 years			5.98 years			6.05 years

Net Income (Loss) Per Share (Tables)

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Summary of Basic and Diluted Net Income (Loss) Per Share

Basic and diluted net income (loss) per share was calculated as follows for the years ended December 31, 2021, 2020 and 2019:

	Year Ended December 31,
	2021			2020		2019
Basic net income (loss) per share:
Numerator:
Net income (loss) (in thousands)	$	(457,892	)	$	606,073	$	(680,238	)
Denominator:
Weighted average common stock outstanding —basic		58,670,230			51,983,188		50,833,837

Effect of dilutive securities:
Stock options		—			721,791		—
Restricted stock units		—			292,241		—
Employee Stock Purchase Plan		—			5,895		—
Total dilutive securities		—			1,019,927		—

Weighted average common stock outstanding —diluted		58,670,230			53,003,115		50,833,837
Net income (loss) per share—basic	$	(7.80	)	$	11.66	$	(13.38	)
Net income (loss) per share—diluted	$	(7.80	)	$	11.43	$	(13.38	)

Summary of Anti-Dilutive Common Stock Equivalents Outstanding

	Year Ended December 31,
	2021		2020		2019
Stock options		6,599,429		4,781,737		7,677,518
Restricted stock units		563,334		—		—
Employee stock purchase plan		23,625		—		33,429
		7,186,388		4,781,737		7,710,947

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Summary of Income (Loss) Before Income Tax Expense

Income (loss) before income tax expense consists of the following:

	Year Ended December 31,
	2021			2020			2019
	(in thousands)
Domestic	$	(457,693	)	$	639,986		$	(634,289	)
Foreign		(199	)		(33,913	)		(45,949	)
	$	(457,892	)	$	606,073		$	(680,238	)

Summary of Reconciliation of U.S. Statutory Rate to Company's Effective Tax Rate

A reconciliation of the U.S. statutory rate to the Company’s effective tax rate is as follows:

	Year Ended December 31,
	2021			2020			2019
Tax due at statutory rate		21.0	%		21.0	%		21.0	%
State taxes, net of federal		1.9			5.7			2.8
Biogen transaction-related items		—			(10.1	)		—
Stock-based compensation		(5.2	)		0.9			1.4
Foreign rate differential		—			1.2			(1.6	)
Federal and state credits		3.5			(1.5	)		2.4
Change in valuation allowance		(20.7	)		(17.6	)		(25.8	)
Other		(0.5	)		0.4			(0.2	)
		0.0	%		0.0	%		0.0	%

Summary of Significant Components of Company's Net Deferred Tax Asset

Significant components of the Company’s net deferred tax assets at December 31, 2021 and 2020 are as follows:

	December 31,
	2021			2020
	(in thousands)
Net operating losses	$	305,824		$	222,607
Capitalized start-up costs		735			873
Tax credit carryforwards		106,176			90,460
Accrued expenses		6,684			3,157
Depreciation and amortization		1,401			1,614
Stock-based compensation		49,281			56,520
Right of use asset		(3,702	)		(5,981	)
Lease liability		4,236			6,705
Other		(31	)		148
Total net deferred tax asset before valuation allowance		470,604			376,103
Valuation allowance		(470,604	)		(376,103	)
Net deferred tax asset	$	—		$	—

Summary of Gross Unrecognized Tax Benefits Excluding Interest and Penalties

The following table reconciles the beginning and ending amounts of gross unrecognized tax benefits, excluding interest and penalties, if any, for the year ended December 31, 2021:

	2021
	(in thousands)
Balance as of January 1	$	-
Increases related to current year tax positions		396
Increases related to prior year tax positions		5,688
Balance as of December 31	$	6,084

Restructuring (Tables)

12 Months Ended

Dec. 31, 2021

Restructuring And Related Activities [Abstract]

Summary of Restructuring Activity

Restructuring activity during the years ended December 31, 2021 and December 31, 2020 was as follows:

	Restructuring accrual
	(in thousands)
Balance as of January 1, 2020	$	-
Restructuring expenses incurred		27,743
Cash paid		(25,102	)
Non-cash activity		(2,438	)
Balance as of December 31, 2020		203
Cash paid		(203	)
Balance as of December 31, 2021	$	-

Nature of the Business - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended		141 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021
Nature Of Business [Line Items]
Accumulated deficit	$ 1,495,386	$ 1,037,494	$ 1,495,386
Net income from up-front		$ 606,100
Up-front payments receive	$ 1,000,000
Redeemable Convertible Preferred Stock [Member] \| Convertible Notes [Member] \| Initial Public Offering [Member]
Nature Of Business [Line Items]
Net proceeds from sale of equity and notes			$ 2,800,000

- Definition

The cumulative amount of the reporting entity's undistributed earnings or deficit.

+ References + Details

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2021
Product Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Incremental costs incurred expected amortization period of asset	true

Fair Value Measurements - Summary of Company's Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	$ 294,233	$ 1,661,082
Total marketable securities	1,448,063	438,467
Total cash equivalents and marketable securities	1,742,296	2,099,549
Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	294,233	1,661,082
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	290,234	1,637,609
Total cash equivalents and marketable securities	290,234	1,637,609
Fair Value, Inputs, Level 1 [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	290,234	1,637,609
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	3,999	23,473
Total marketable securities	1,448,063	438,467
Total cash equivalents and marketable securities	1,452,062	461,940
Fair Value, Inputs, Level 2 [Member] \| Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	3,999	23,473
U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	324,532	160,588
U.S. Government Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	324,532	160,588
U.S. Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	627,780	123,107
U.S. Corporate Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	627,780	123,107
International Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	236,812	57,676
International Corporate Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	236,812	57,676
U.S. Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	80,176	45,963
U.S. Commercial Paper [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	80,176	45,963
International Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	142,335	51,133
International Commercial Paper [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	142,335	$ 51,133
U.S. Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	36,428
U.S. Municipal Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	$ 36,428

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument Fair Value Carrying Value [Line Items]
Transfers among the Level 1, Level 2 and Level 3 categories	$ 0	$ 0
Impairment of assets	0	0
US Treasury Bond Securities \| U.S. Corporate Bonds [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities fair value held to maturity		$ 5,100,000
US Treasury Bond Securities \| Corporate Bonds and Municipal Securities [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities fair value held to maturity	436,100,000
US Treasury Bond Securities \| Corporate Bonds and Municipal Securities [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities loss on fair value held to maturity	$ 431,500,000
Maximum [Member] \| US Treasury Bond Securities \| U.S. Corporate Bonds [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities, remaining contractual maturities	1 year	1 year
Marketable securities held, matuirity period		2 years
Maximum [Member] \| US Treasury Bond Securities \| Corporate Bonds and Municipal Securities [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities held, matuirity period	2 years
Minimum [Member] \| US Treasury Bond Securities \| U.S. Corporate Bonds [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities held, matuirity period		1 year
Minimum [Member] \| US Treasury Bond Securities \| Corporate Bonds and Municipal Securities [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities held, matuirity period	1 year

Fair Value Measurements - Summary of Gross Unrealized Gains and Losses of Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,450,723	$ 438,052
Gross Unrealized Gains	27	451
Gross Unrealized Losses	(2,687)	(36)
Fair Value	1,448,063	438,467
U.S. Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	325,514	160,589
Gross Unrealized Gains		11
Gross Unrealized Losses	(982)	(12)
Fair Value	324,532	160,588
U.S. Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	628,836	122,882
Gross Unrealized Gains	27	240
Gross Unrealized Losses	(1,083)	(15)
Fair Value	627,780	123,107
International Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	237,303	57,485
Gross Unrealized Gains		200
Gross Unrealized Losses	(491)	(9)
Fair Value	236,812	57,676
U.S. Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	80,194	45,963
Gross Unrealized Losses	(18)
Fair Value	80,176	45,963
International Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	142,358	51,133
Gross Unrealized Losses	(23)
Fair Value	142,335	$ 51,133
U.S. Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	36,518
Gross Unrealized Losses	(90)
Fair Value	$ 36,428

Balance Sheet Components - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,989	$ 13,843
Less: Accumulated depreciation	(4,973)	(7,088)
Property and equipment, net	3,016	6,755
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,391	2,758
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,208	1,865
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5,390	$ 9,220

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 13, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 4,182	$ 4,200	$ 2,630	$ 2,283
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life		3 years
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life		5 years

Balance Sheet Components - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued research and development costs	$ 39,147	$ 34,398
Employee-related	18,618	14,769
Professional services	8,893	5,184
Other	617	500
Total accrued expenses	$ 67,275	$ 54,851

Leases, Commitments and Contingencies - Operating Leases - Additional Information (Detail)			1 Months Ended	12 Months Ended
	Feb. 28, 2019 ft²	Jan. 01, 2019 USD ($) ft²	Mar. 31, 2019 ft²	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 13, 2021 USD ($)
Commitments And Contingencies [Line Items]
Lease expire date					Jan. 31, 2022
Operating lease option to extend				true
Operating lease renewal term				5 years
Right-of-use operating asset \| $		$ 5,300,000		$ 16,109,000	$ 25,064,000	$ 3,700
Lessee, operating lease contract term					3 years
Remaining Amount Of Lease Write Off \| $					$ 2,300,000
Restricted Cash And Cash Equivalents Noncurrent \| $					$ 700,000
Operating Lease One [Member]
Commitments And Contingencies [Line Items]
Office space rent under operating lease	58,442	58,442	63,017
Lease expire date		Aug. 31, 2024	Aug. 31, 2024
Increased office space rent			4,575
Operating Lease Two [Member]
Commitments And Contingencies [Line Items]
Office space rent under operating lease		40,419
Lease expire date		Aug. 31, 2024
Operating Lease Three [Member]
Commitments And Contingencies [Line Items]
Office space rent under operating lease		15,525
Lease expire date		Nov. 30, 2024
Operating Lease Five [Member]
Commitments And Contingencies [Line Items]
Office space rent under operating lease		15,975
Lease expire date		Feb. 29, 2024
Minimum [Member]
Commitments And Contingencies [Line Items]
Operating lease remaining lease terms				1 year
Maximum [Member]
Commitments And Contingencies [Line Items]
Operating lease remaining lease terms				3 years

Leases, Commitments and Contingencies - Schedule of Amounts of Operating Leases (Detail) - USD ($)	Dec. 31, 2021	Dec. 13, 2021	Dec. 31, 2020	Jan. 01, 2019
Assets
Right-of-use operating asset	$ 16,109,000	$ 3,700	$ 25,064,000	$ 5,300,000
Liabilities
Current operating lease liabilities	7,468,000		8,662,000
Long-term operating lease liabilities	10,964,000		19,438,000
Total operating lease liabilities	$ 18,432,000		$ 28,100,000

Leases, Commitments and Contingencies - Schedule of Lease Expense by Lease Type Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Operating lease cost	$ 8,748	$ 8,838	$ 9,804
Variable lease cost	1,600	2,285	2,675
Short-term lease cost	101	74	438
Sublease income	(234)
Total	$ 10,215	$ 11,197	$ 12,917

Leases, Commitments and Contingencies - Schedule of Minimum Lease Payments (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Lessee Lease Description [Line Items]
Present value of operating lease liabilities	$ 18,432	$ 28,100
ASU Topic (842) [Member]
Lessee Lease Description [Line Items]
2022	7,468
2023	7,643
2024	5,316
Total lease payments	20,427
Less imputed interest	(1,995)
Present value of operating lease liabilities	$ 18,432

Leases, Commitments and Contingencies - Schedule of Weighted Average Remaining Lease Term and Weighted Average Discount Rate of Our Operating Leases (Detail)	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Weighted average remaining lease term in years	2 years 8 months 4 days
Weighted average discount rate	7.50%

Leases, Commitments and Contingencies - Schedule of Supplemental Disclosure of Cash Flow Information Related To Operating Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 9,264	$ 9,231	$ 9,946
Right-of-use assets obtained in exchange for new operating lease liabilities			$ 872
Lease asset de-recognized upon lease cancellation	$ 3,733	$ 2,310

Leases, Commitments and Contingencies - CyDex License Agreement - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Commitments And Contingencies [Line Items]
Research and development expense	$ 283,166,000	$ 292,714,000	$ 368,815,000
CyDex License Agreement [Member]
Commitments And Contingencies [Line Items]
Research and development expense	1,000,000.0
CyDex License Agreement [Member] \| First and Second Clinical Development Milestones [Member] \| Brexanolone [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	800,000
CyDex License Agreement [Member] \| First and Second Regulatory Milestones [Member] \| Brexanolone [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	3,800,000
CyDex License Agreement [Member] \| Third and Fourth Clinical Development Milestones [Member] \| Brexanolone [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	1,300,000
CyDex License Agreement [Member] \| Third and Fourth Regulatory Milestones [Member] \| Brexanolone [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	8,500,000
CyDex License Agreement [Member] \| Clinical Development [Member] \| SAGE-689 [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	800,000
CyDex License Agreement [Member] \| Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Construction Expense Related To Milestone Payment	1,300,000
CyDex License Agreement [Member] \| Regulatory Milestones [Member] \| Brexanolone [Member]
Commitments And Contingencies [Line Items]
Research and development expense related to milestone expense	100,000
Milestone payments	100,000
Intangible asset related to milestone			$ 3,000,000.0
CyDex License Agreement [Member] \| Regulatory Milestones [Member] \| SAGE-689 [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	1,800,000
CyDex License Agreement [Member] \| Clinical Development and Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Research and development expense related to milestone expense	3,700,000
Milestone payments	3,700,000
Intangible asset related to milestone	$ 3,000,000.0

Leases, Commitments and Contingencies - University of California License Agreements - Additional Information (Detail) - University of California License Agreements [Member] - USD ($)		1 Months Ended	12 Months Ended
	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2015
Commitments And Contingencies [Line Items]
Upfront payment		$ 50,000
Annual license maintenance fee						$ 15,000
Milestone payments			$ 0	$ 0	$ 500,000
After The Effective Date [Member]
Commitments And Contingencies [Line Items]
Licenses Expiration period, maximum	27 years
After The First Sale [Member]
Commitments And Contingencies [Line Items]
Licenses Expiration period, maximum	15 years
Clinical Development [Member]
Commitments And Contingencies [Line Items]
Milestone payments	$ 100,000
Milestone outstanding	$ 0
Clinical Development [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Percentage of net sales paid as royalties	1.00%
Regulatory Milestones [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments		700,000
Sales Milestones [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments		$ 2,000,000.0
Regulatory and Sales Milestones [Member]
Commitments And Contingencies [Line Items]
Research and development expense related to milestone expense			300,000
Milestone payments			300,000
Intangible asset related to milestone			500,000
Milestone payments related to intangible assets			$ 500,000

Collaboration Agreements - Additional Information (Detail) - USD ($)				3 Months Ended	9 Months Ended	12 Months Ended
	Nov. 30, 2020	Feb. 27, 2019	Jun. 30, 2018	Jun. 30, 2018	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 12, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue						$ 6,308,000	$ 1,114,200,000	$ 6,868,000
Public offering of common stock, net of offering costs, Shares		3,833,334					6,241,473
Collaboration receivable - related party						18,506,000
Collaboration Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue								$ 2,911,000
Shionogi Collaboration Agreement [Member] \| Collaboration Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue						0	$ 0
Shionogi Collaboration Agreement [Member] \| SAGE-217 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement effective date			Jun. 30, 2018
Upfront payment			$ 90,000,000.0
Average percentage on tiered royalties			20.00%
Revenue				$ 90,000,000.0
Standalone selling price of license performance obligation			$ 90,000,000.0	90,000,000.0
Shionogi Collaboration Agreement [Member] \| SAGE-217 [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payment receivable			485,000,000.0	$ 485,000,000.0
Shionogi Collaboration Agreement [Member] \| SAGE-217 [Member] \| Maximum [Member] \| Regulatory Milestones [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future milestone payments			70,000,000.0
Shionogi Collaboration Agreement [Member] \| SAGE-217 [Member] \| Maximum [Member] \| Commercial Milestones [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future milestone payments			30,000,000.0
Shionogi Collaboration Agreement [Member] \| SAGE-217 [Member] \| Maximum [Member] \| Sales Milestones [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future milestone payments			$ 385,000,000.0
Biogen Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement effective date	Dec. 28, 2020
Upfront payment							875,000,000.0
Revenue						0	1,100,000,000
Standalone selling price of license performance obligation							1,100,000,000
Sale of stock, consideration received							$ 1,500,000,000
Public offering of common stock, net of offering costs, Shares							6,241,473
Purchase price							$ 650,000,000.0
Operating expenses						91,130,000
Collaboration receivable - related party						18,500,000
Proceeds from related parties					$ 72,600,000
Payments To Related Parties						$ 0
Biogen Collaboration Agreement [Member] \| SAGE-217 [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payment receivable									$ 1,600,000,000
Biogen Collaboration Agreement [Member] \| SAGE-217 [Member] \| Maximum [Member] \| Sales Milestones [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future milestone payments	$ 300,000,000.0
Biogen Collaboration Agreement [Member] \| SAGE-217 [Member] \| Maximum [Member] \| Regulatory and Commercial Milestones [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future milestone payments	475,000,000.0
Biogen Collaboration Agreement [Member] \| SAGE-324 [Member] \| Maximum [Member] \| Sales Milestones [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future milestone payments	300,000,000.0
Biogen Collaboration Agreement [Member] \| SAGE-324 [Member] \| Maximum [Member] \| Regulatory and Commercial Milestones [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future milestone payments	$ 520,000,000.0
Biogen Stock Purchase Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment							875,000,000.0
Purchase price							650,000,000.0
Transaction price, total							1,100,000,000
Premium amount on equity investment							$ 232,500,000
Price per share							$ 104.14
Premium on per share price							40.00%
Biogen stock purchase agreement, description						The standstill restrictions terminate on the earliest of (i) a specified regulatory milestone under the Biogen Collaboration Agreement, (ii) the date one year following the termination of the Biogen Collaboration Agreement and (iii) the seventh anniversary of the Effective Date. BIMA has also agreed not to, and to cause its affiliates not to, sell or transfer any of the Biogen Shares for a period of eighteen months from the closing of the sale of the Biogen Shares, which expires June 30, 2022, and to limit sales and transfers of the Biogen Shares for an additional eighteen-month period, in each case subject to specified conditions and exceptions.
Stock issued							$ 417,500,000

Collaboration Agreements - Summary of Operating Expenses Category Related to Collaboration Agreement (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net reimbursement from Biogen reflected in the consolidated statement of operations and comprehensive loss:
Total operating costs and expenses	$ 467,217	$ 517,974	$ 714,992
Biogen Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Expenses related to the Biogen Collaboration Agreement incurred by Sage	193,776
Net reimbursement from Biogen reflected in the consolidated statement of operations and comprehensive loss:
Selling, general and administrative expenses	(11,282)
Operating expenses	(91,130)
Total operating costs and expenses	102,646
Research and Development [Member] \| Biogen Collaboration Agreement [Member]
Net reimbursement from Biogen reflected in the consolidated statement of operations and comprehensive loss:
Research and development expenses	$ (79,848)

Preferred Stock - Additional Information (Detail) - shares	Dec. 31, 2021	Dec. 31, 2020
Temporary Equity Disclosure [Abstract]
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Common Stock - Additional Information (Detail) - USD ($)		12 Months Ended
	Feb. 27, 2019	Dec. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Common stock, shares authorized		120,000,000	120,000,000
Common stock, par value		$ 0.0001	$ 0.0001
Dividends declared		$ 0	$ 0
Voting rights		Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders.
Public offering of common stock, net of offering costs, Shares	3,833,334		6,241,473
Common stock price per share	$ 150.00		$ 104.14
Proceeds from public offering of common stock, net of commissions and underwriting discounts and offering costs	$ 560,900,000		$ 650,000,000.0
Purchase of treasury stock, Shares		3,033
Total cost of shares held in treasury		$ 400,000	$ 400,000

Stock-Based Compensation - Additional Information (Detail)		12 Months Ended
	Jan. 01, 2021 shares	Dec. 31, 2021 USD ($) Milestone $ / shares shares	Dec. 31, 2020 USD ($) Milestone $ / shares shares	Dec. 31, 2019 USD ($) Milestone $ / shares shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 shares	Sep. 20, 2018 shares	Jul. 02, 2014 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation granted under plan vested period		4 years
Share based compensation, vest period		1 year
Share based compensation, term of plan		10 years
Total number of shares outstanding		8,539,537
Common stock available for issuance under stock option plan		5,672,875
Restricted stock units granted		268,119	550,890	0
Fair value of restricted stock units vested \| $		$ 8,800,000
Restricted stock units vested		113,941	0
Stock-based compensation expense \| $		$ 104,629,000	$ 95,994,000	$ 153,231,000
Weighted average grant date fair value per share \| $ / shares		$ 51.87	$ 37.53	$ 82.39
Share option, weighted-average forfeiture rates		16.70%	20.60%	13.70%
Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding and unvested performance restricted stock units		1,256,098
Total unrecognized stock-based compensation expense \| $		$ 59,200,000
Restricted stock units granted		531,176	471,386	393,539
Fair value of restricted stock units vested \| $			$ 0	$ 11,100,000
Percentage Of Milestone Achieved				18.00%
Stock-based compensation expense \| $				$ 10,900,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation granted under plan vested period						2 years
Outstanding and unvested performance restricted stock units		1,256,098	957,695
Restricted stock units granted		799,295				32,500
Fair value of restricted stock units vested \| $				2,000,000.0	$ 2,600,000
Stock-based compensation expense \| $		$ 25,375,000	$ 4,904,000	10,992,000
Performance-Based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense \| $		$ 0	$ 0	0
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted		2,095,363
Total number of shares outstanding		7,283,439	7,157,830
Total unrecognized stock-based compensation expense \| $		$ 86,000,000.0
Stock-based compensation expense \| $		$ 78,516,000	$ 90,064,000	140,517,000
Weighted average period of unrecognized compensation costs		2 years 7 months 13 days
Intrinsic value of options exercised \| $		$ 9,000,000.0	$ 2,100,000	$ 119,100,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted			0	0
Total unrecognized stock-based compensation expense \| $		$ 10,800,000
Number of shares outstanding and unvested stock options		684,010
Performance Shares [Member] \| Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted		650,000
Restricted Stock Units Vest One Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units vesting percentage		25.00%
Restricted Stock Units Vest One Year Anniversary [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units vesting percentage		25.00%	25.00%			50.00%
Restricted stock units vesting period month and year			2021-04			2018-02
Restricted Stock Units Vest Two Year Anniversary [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units vesting percentage			75.00%			50.00%
Restricted stock units vesting period month and year			2022-04			2019-02
2011 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted		0
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares annual increase added to plan	2,332,336
Stock-based compensation expense \| $		$ 0	$ 0
2014 Plan [Member] \| Milestone One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Milestone performance restricted stock percentage			0.39	0.38
2014 Plan [Member] \| Milestone Four [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of performance based grants that were achieved					20.00%	33.00%
2014 Plan [Member] \| Milestone Five [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of performance based grants that were achieved					19.00%
2014 Plan [Member] \| Milestone Six [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of performance based grants that were achieved					41.00%	34.00%
2014 Plan [Member] \| Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Milestones achieved \| Milestone		2
2014 Plan [Member] \| Performance-Based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Milestones achieved \| Milestone		0	0	1
2014 Plan [Member] \| Performance Milestone
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of restricted stock units vested \| $		$ 6,100,000	$ 3,400,000
Stock-based compensation expense \| $		$ 3,800,000	$ 12,800,000	$ 16,300,000
2014 Plan [Member] \| Performance Milestone \| Award Granted in 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of milestones not met \| Milestone			1
2014 Plan [Member] \| Performance Milestone \| Award Granted in 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of milestones not met \| Milestone		1
2014 Plan [Member] \| Performance Milestone \| Milestone Six [Member] \| Award Granted in 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of milestones not met \| Milestone		3
2014 Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of increase on outstanding shares of Common stock			4.00%
2016 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares reserved for issuance							1,200,000
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares reserved for issuance								282,000
Number of shares issued under the plan		224,638
Accrued expenses \| $		$ 300,000
Total number of shares available for issuance		57,362

Stock-Based Compensation - Summary of Activity Relating to Restricted Stock Units (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares	268,119	550,890	0
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Shares at beginning balance	957,695
Granted, Shares	799,295			32,500
Vested, Shares	(302,661)
Forfeited, Shares	(198,231)
Outstanding, Shares at ending balance	1,256,098	957,695

Stock-Based Compensation - Summary of Activity Relating to Time Based and Performance Based Stock Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, Outstanding Shares	8,539,537
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Outstanding Shares	7,157,830
Granted, Shares	2,095,363
Exercised, Shares	(306,078)
Forfeited, Shares	(1,663,676)
Ending balance, Outstanding Shares	7,283,439	7,157,830
Vested and expected to vest, Shares	6,220,652
Exercisable, Shares	4,434,049
Beginning balance, Outstanding Weighted Average Exercise Price	$ 91.41
Granted, Weighted Average Exercise Price	79.76
Exercised, Weighted Average Exercise Price	40.35
Forfeited, Weighted Average Exercise Price	117.80
Ending balance, Outstanding Weighted Average Exercise Price	84.17	$ 91.41
Vested and expected to vest, Weighted Average Exercise Price	84.00
Exercisable, Weighted Average Exercise Price	$ 85.68
Outstanding, Weighted Average Remaining Life	6 years 8 months 26 days	6 years 10 months 28 days
Vested and expected to vest, Weighted Average Remaining Life	6 years 4 months 13 days
Exercisable, Weighted Average Remaining Life	5 years 5 months 19 days
Outstanding, Aggregate Intrinsic Value	$ 16,590	$ 167,242
Vested and expected to vest, Aggregate Intrinsic Value	16,493
Exercisable, Aggregate Intrinsic Value	$ 15,713

Stock-Based Compensation - Summary of Stock-Based Compensation Expense Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 104,629	$ 95,994	$ 153,231
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	49,746	42,370	62,931
Selling, General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 54,883	51,836	$ 90,300
Restructuring Charges [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense		$ 1,788

Stock-Based Compensation - Summary of Stock-Based Compensation Expense by Award Type (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 104,629	$ 95,994	$ 153,231
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	78,516	90,064	140,517
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	25,375	4,904	10,992
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 738	$ 1,026	$ 1,722

Stock-Based Compensation - Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility	75.92%	77.86%	71.34%
Risk-free interest rate	0.63%	0.97%	2.21%
Expected term	5 years 11 months 1 day	5 years 11 months 23 days	6 years 18 days

Net Income (Loss) Per Share - Summary of Basic and Diluted Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net income (loss)	$ (457,892)	$ 606,073	$ (680,238)
Denominator:
Weighted average number of common shares outstanding—basic	58,670,230	51,983,188	50,833,837
Effect of dilutive securities:
Dilutive effect of shares of common stock equivalents	0	1,019,927	0
Weighted average common stock outstanding —diluted	58,670,230	53,003,115	50,833,837
Net income (loss) per share—basic	$ (7.80)	$ 11.66	$ (13.38)
Net income (loss) per share—diluted	$ (7.80)	$ 11.43	$ (13.38)
Stock Options [Member]
Effect of dilutive securities:
Dilutive effect of shares of common stock equivalents	0	721,791	0
Restricted Stock Units [Member]
Effect of dilutive securities:
Dilutive effect of shares of common stock equivalents	0	292,241	0
Employee Stock Purchase Plan [Member]
Effect of dilutive securities:
Dilutive effect of shares of common stock equivalents	0	5,895	0

Net Income (Loss) Per Share - Summary of Anti-Dilutive Common Stock Equivalents Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	7,186,388	4,781,737	7,710,947
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	6,599,429	4,781,737	7,677,518
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	563,334
Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	23,625		33,429

Income Taxes - Summary of Income (Loss) Before Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Domestic	$ (457,693)	$ 639,986	$ (634,289)
Foreign	(199)	(33,913)	(45,949)
Net income (loss) before income tax expense	$ (457,892)	$ 606,073	$ (680,238)

- 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123384075&loc=d3e41242-110953

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
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Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Section S99
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-Subparagraph (SX 210.7-04(8))
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Current tax expense	$ 0
Deferred tax expense	0
Federal operating loss carryforwards	$ 1,300,000,000
Federal net operating loss carryforwards, limitation percentage	80.00%
Federal orphan drug tax credit carry forwards	$ 40,100,000
Tax credit carry forwards expiration period	2034
Change in amount of deferred tax assets	$ 94,500,000
Valuation allowance	470,604,000	$ 376,103,000
Valuation allowance, increase (decrease), amount	94,500,000	(107,200,000)	$ 174,900,000
Gross unrecognized tax benefits	6,084,000	0	0
Accrued interest or penalties related to uncertain tax positions	0	0
Uncertain tax positions	0	$ 0	$ 0
Begin to Expire 2033 [Member]
Income Tax Disclosure [Line Items]
Federal operating loss carryforwards	$ 30,200,000
Federal net operating loss carryforwards expiration year	2033
Begin to Expire 2028 [Member]
Income Tax Disclosure [Line Items]
State operating loss carryforwards	$ 584,800,000
State net operating loss carryforwards expiration year	2031
Domestic Tax Authority [Member]
Income Tax Disclosure [Line Items]
Research and development tax credits carryforwards	$ 56,900,000
Research and development tax credits carryforwards expiration year	2031
State and Local Jurisdiction [Member]
Income Tax Disclosure [Line Items]
Research and development tax credits carryforwards	$ 11,600,000
Research and development tax credits carryforwards expiration year	2028

Income Taxes - Summary of Reconciliation of U.S. Statutory Rate to Company's Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Tax due at statutory rate	21.00%	21.00%	21.00%
State taxes, net of federal	1.90%	5.70%	2.80%
Biogen transaction-related items		(10.10%)
Stock-based compensation	(5.20%)	0.90%	1.40%
Foreign rate differential		1.20%	(1.60%)
Federal and state credits	3.50%	(1.50%)	2.40%
Change in valuation allowance	(20.70%)	(17.60%)	(25.80%)
Other	(0.50%)	0.40%	(0.20%)
Total effective tax rate	0.00%	0.00%	0.00%

Income Taxes - Summary of Significant Components of Company's Net Deferred Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Net operating losses	$ 305,824	$ 222,607
Capitalized start-up costs	735	873
Tax credit carryforwards	106,176	90,460
Accrued expenses	6,684	3,157
Depreciation and amortization	1,401	1,614
Stock-based compensation	49,281	56,520
Right of use asset	(3,702)	(5,981)
Lease liability	4,236	6,705
Other	(31)	148
Total net deferred tax asset before valuation allowance	470,604	376,103
Valuation allowance	$ (470,604)	$ (376,103)

Income Taxes - Summary of Gross Unrecognized Tax Benefits Excluding Interest and Penalties (Detail)	12 Months Ended
	Dec. 31, 2021 USD ($)
Income Tax Disclosure [Abstract]
Balance as of January 1	$ 0
Increases related to current year tax positions	396,000
Increases related to prior year tax positions	5,688,000
Balance as of December 31	$ 6,084,000

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Postemployment Benefits [Abstract]
Employer matching contribution, percent of match	50.00%	50.00%	50.00%
Maximum annual contributions per employee, percent	6.00%	6.00%	6.00%
Employer contribution	$ 1.8	$ 2.2	$ 3.6
Defined Contribution Plan, Sponsor Location [Extensible Enumeration]	us-gaap:DomesticPlanMember	us-gaap:DomesticPlanMember	us-gaap:DomesticPlanMember
Defined Contribution Plan, Tax Status [Extensible Enumeration]	us-gaap:QualifiedPlanMember	us-gaap:QualifiedPlanMember	us-gaap:QualifiedPlanMember

Restructuring - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2020	Dec. 31, 2020	Dec. 31, 2021
Restructuring Cost And Reserve [Line Items]
Operating expenses, workforce reduction, percent	53.00%
Restructuring accrual		$ 203,000	$ 0
Employee Severance
Restructuring Cost And Reserve [Line Items]
Employee severance, benefits, and related costs		$ 27,700,000

Restructuring - Summary of Restructuring Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restructuring And Related Activities [Abstract]
Balance	$ 203,000
Restructuring		$ 27,743,000
Cash paid	(203,000)	(25,102,000)
Non-cash activity		(2,438,000)
Balance	$ 0	$ 203,000