Sage Therapeutics (SAGE) 10-K 27 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 20, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	SAGE
Entity Registrant Name	Sage Therapeutics, Inc.
Entity Central Index Key	0001597553
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		51,911,120
Entity Public Float			$ 9,273,813,345
Entity Interactive Data Current	Yes
Title of 12(b) Security	common stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity File Number	001-36544
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-4486580
Entity Address, Address Line One	215 First Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	299-8380
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Part III of this Annual Report on Form 10-K incorporates by reference certain information from the registrant’s definitive Proxy Statement for its 2020 annual meeting of shareholders, which the registrant intends to file pursuant to Regulation 14A with the Securities and Exchange Commission not later than 120 days after the registrant’s fiscal year end of December 31, 2019. Except with respect to information specifically incorporated by reference in this Form 10-K, the Proxy Statement is not deemed to be filed as part of this Form 10-K.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 126,705	$ 190,943
Marketable securities	881,688	731,833
Prepaid expenses and other current assets	26,700	21,919
Total current assets	1,035,093	944,695
Property and equipment, net	9,126	5,643
Restricted cash	2,367	2,367
Right-of-use operating asset	33,771
Other long-term assets	3,793
Total assets	1,084,150	952,705
Current liabilities:
Accounts payable	15,266	34,036
Accrued expenses	86,618	51,994
Operating lease liability, current portion	10,244
Total current liabilities	112,128	86,030
Operating lease liability, net of current portion	26,848
Other liabilities	519	3,704
Total liabilities	139,495	89,734
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized at December 31, 2019 and December 31, 2018; no shares issued or outstanding at December 31, 2019 and December 31, 2018
Common stock, $0.0001 par value per share; 120,000,000 shares authorized at December 31, 2019 and December 31, 2018; 51,880,227 and 46,891,296 shares issued at December 31, 2019 and December 31, 2018; 51,877,194 and 46,888,263 shares outstanding at December 31, 2019 and December 31, 2018	5	5
Treasury stock, at cost, 3,033 shares at December 31, 2019 and December 31, 2018	(400)	(211)
Additional paid-in capital	2,587,322	1,827,021
Accumulated deficit	(1,643,567)	(963,329)
Accumulated other comprehensive gain (loss)	1,295	(515)
Total stockholders’ equity	944,655	862,971
Total liabilities and stockholders’ equity	$ 1,084,150	$ 952,705

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
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	51,880,227	46,891,296
Common stock, shares outstanding	51,877,194	46,888,263
Treasury stock, shares	3,033	3,033

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Total revenue	$ 6,868	$ 90,273
Type of Revenue [Extensible List]	us-gaap:CollaborativeArrangementMember	us-gaap:CollaborativeArrangementMember	us-gaap:CollaborativeArrangementMember
Operating costs and expenses:
Cost of goods sold	$ 400
Research and development	368,815	$ 282,107	$ 210,277
Selling, general and administrative	345,777	201,404	62,878
Total operating costs and expenses	714,992	483,511	273,155
Loss from operations	(708,124)	(393,238)	(273,155)
Interest income, net	27,804	20,334	3,099
Other income (expense), net	82	22	(64)
Net loss	$ (680,238)	$ (372,882)	$ (270,120)
Net loss per share—basic and diluted	$ (13.38)	$ (8.08)	$ (7.09)
Weighted average number of common shares outstanding—basic and diluted	50,833,837	46,121,194	38,113,678
Comprehensive loss:
Net loss	$ (680,238)	$ (372,882)	$ (270,120)
Other comprehensive items:
Unrealized gain (loss) on marketable securities	1,810	(486)	73
Total other comprehensive gain (loss)	1,810	(486)	73
Total comprehensive loss	(678,428)	(373,368)	$ (270,047)
Product Revenue [Member]
Total revenue	3,957
Collaboration Revenue [Member]
Total revenue	$ 2,911	$ 90,273

Consolidated Statements of Chan

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 Income (Loss) [Member]	Accumulated Deficit [Member]
Balances at Dec. 31, 2016	$ 368,517	$ 4	$ (17)	$ 688,959	$ (102)	$ (320,327)
Balances, Shares at Dec. 31, 2016		37,222,172	346
Issuance of common stock from exercise of stock options, Amount	15,437	$ 1		15,436
Issuance of common stock from exercise of stock options, Shares		706,222
Issuance of common stock under employee stock purchase plan	771			771
Issuance of common stock under employee stock purchase plan, Shares		15,718
Purchase of treasury stock, Amount	(96)		$ (96)
Purchase of treasury stock, Shares			614
Stock-based compensation expense	35,142			35,142
Public offering of common stock, net of offering costs, Amount	325,751			325,751
Public offering of common stock, net of offering costs, Shares		4,058,822
Unrealized gain (loss) on available-for-sale securities	73				73
Net loss	(270,120)					(270,120)
Balances at Dec. 31, 2017	475,475	$ 5	$ (113)	1,066,059	(29)	(590,447)
Balances, Shares at Dec. 31, 2017		42,002,934	960
Issuance of common stock from exercise of stock options, Amount	27,014			27,014
Issuance of common stock from exercise of stock options, Shares		824,188
Issuance of common stock under employee stock purchase plan	2,705			2,705
Issuance of common stock under employee stock purchase plan, Shares		19,687
Purchase of treasury stock, Amount	(98)		$ (98)
Purchase of treasury stock, Shares			2,073
Stock-based compensation expense	100,993			100,993
Public offering of common stock, net of offering costs, Amount	631,154			631,154
Public offering of common stock, net of offering costs, Shares		4,032,012
Unrealized gain (loss) on available-for-sale securities	(486)				(486)
Vesting of restricted stock units, net of employee tax obligations	(904)			(904)
Vesting of restricted stock units, net of employee tax obligations, Shares		9,442
Net loss	(372,882)					(372,882)
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 employee stock purchase plan	5,744			5,744
Issuance of common stock under employee stock purchase plan, Shares		55,404
Purchase of treasury stock, Amount	$ (189)		$ (189)
Purchase of treasury stock, Shares	(3,033)
Stock-based compensation expense	$ 151,508			151,508
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
Unrealized gain (loss) on available-for-sale securities	1,810				1,810
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
Net 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

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss	$ (680,238)	$ (372,882)	$ (270,120)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	153,231	101,963	35,534
Premium on marketable securities	(3,674)	(215)	(105)
Amortization of discount on marketable securities	(6,966)	(9,892)	(293)
Depreciation	2,283	1,143	531
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(4,781)	(15,462)	(1,127)
Other long-term assets	(3,793)
Right-of-use operating asset	8,168
Operating lease liabilities, current	2,804
Operating lease liabilities, non-current	(10,761)
Accounts payable	(18,783)	24,544	(3,693)
Accrued expenses and other liabilities	33,804	10,130	19,996
Net cash used in operating activities	(528,706)	(260,671)	(219,277)
Cash flows from investing activities
Proceeds from sales and maturities of marketable securities	1,171,270	974,757	261,225
Purchases of marketable securities	(1,308,675)	(1,484,358)	(244,403)
Purchases of property and equipment	(5,751)	(2,860)	(1,360)
Net cash provided by (used in) investing activities	(143,156)	(512,461)	15,462
Cash flows from financing activities
Proceeds from stock option exercises and employee stock purchase plan issuances	48,850	29,108	15,972
Payment of employee tax obligations related to vesting of restricted stock units	(2,175)	(904)
Payments of offering costs	(328)	(340)	(179)
Proceeds from public offerings of common stock, net of commissions and underwriting discounts	561,277	631,494	326,025
Net cash provided by financing activities	607,624	659,358	341,818
Net increase (decrease) in cash, cash equivalents and restricted cash	(64,238)	(113,774)	138,003
Cash, cash equivalents and restricted cash at beginning of period	193,310	307,084	169,081
Cash, cash equivalents and restricted cash at end of period	129,072	193,310	307,084
Supplemental disclosure of non-cash operating and investing activities
Purchases of property and equipment included in accounts payable	65	51	138
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 872
Landlord tenant incentive included in other current assets		$ 229
Purchases of property and equipment financed with landlord tenant incentive			1,665
Public offering costs included in accounts payable			$ 95

Nature of the Business

Nature of the Business	12 Months Ended
	Dec. 31, 2019
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 lead product, ZULRESSO™ (brexanolone) injection, was approved by the U.S. Food and Drug Administration (“FDA”) in March 2019, for the treatment of postpartum depression (“PPD”) in adults, and was made commercially available in the U.S. beginning on June 24, 2019 after completion of controlled substance scheduling of brexanolone by the U.S. Drug Enforcement Administration and incorporation of the scheduling into the FDA-approved label and other product information. 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 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. The Company is subject to risks and uncertainties common to companies in the biotech 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 commercializing pharmaceutical products for marketing and sale; the potential for development by third parties of new technological innovations that may compete with the Company’s products; the dependence on key personnel; the challenges of protecting proprietary technology; the need to comply with government regulations; the high costs of drug development; and the uncertainty of being able to secure additional capital when needed to fund operations. Under Accounting Standards Update (“ASU”) 2014-15, Presentation of Financial Statements—Going Concern Until such time, if ever, as the Company can generate substantial product revenue and achieve profitability, the Company expects to also 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 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 current 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 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 additional capital if market conditions are favorable or in light of other strategic considerations.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
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 United States of America (“GAAP”). 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. Actual results could differ from those estimates. Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of 90 days or less at the date of purchase to be cash equivalents. As of December 31, 2019 and December 31, 2018, cash equivalents were comprised of cash equivalents, commercial paper and money market funds. 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. Realized gains and losses and declines in value judged to be other than temporary are included as a component of other expense, net, based on the specific identification method. When determining whether a decline in value is other than temporary, the Company considers several factors, including whether the Company has the intent to sell the security, and whether it is more likely than not that the Company will be required to sell the security prior to recovery of its amortized cost basis. No declines in value were deemed to be other than temporary during the years ended December 31, 2019 and December 31, 2018. Restricted Cash For the initial facility of the Company, a deposit of $39,000 was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing the initial lease and the restriction will expire in 2024, in accordance with the most recent amendment to the operating lease agreement. A deposit of $0.3 million was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing an amendment to the lease of the initial facility of the Company and the restriction will expire in 2024, in accordance with the most recent amendment to the operating lease agreement. These balances are included in restricted cash on the accompanying consolidated balance sheets. A deposit of $0.5 million was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing the separate facility lease on the second multi-tenant building in May 2016 and the restriction will expire in 2024, in accordance with the most recent amendment to the operating lease agreement. A deposit of $0.4 million was restricted from withdrawal as of December 31, 2018. The restriction is related to securing an amendment to the lease of the separate facility of the Company and the restriction will expire in 2024, in accordance with the most recent amendment to the operating lease agreement. These balances are included in restricted cash on the accompanying consolidated balance sheets. A deposit of $0.4 million was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing a separate facility lease on the third multi-tenant building in December 2018 that will expire on February 29, 2024, under which, beginning on March 1, 2019, the Company will rent 15,975 square feet of additional office space. The restriction will expire in 2024, in accordance with the operating lease agreement. This balance is included in restricted cash on the accompanying consolidated balance sheet. A deposit of $0.7 million was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing leases on automobiles for employees who are based in the field. The restriction will expire in 2021, in accordance with the lease agreement. This balance is included in restricted cash on the accompanying consolidated balance sheet. 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, or 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 profile. The Company reserves against trade accounts receivable for estimated losses that may arise from a customer’s inability to pay and any amounts determined to be uncollectible are written off against the reserve when it is probable that the receivable will not be collected. Trade accounts receivable are included in prepaid expenses and other current assets on the consolidated balance sheets and the amount was not significant as of December 31, 2019. 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 identical and, as a result, are both classified as inventory. Amounts in inventory associated with research and development 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 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 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, 2019. Prior to the initial date 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 loss in the period incurred. The Company received FDA approval for ZULRESSO on March 19, 2019 and subsequently began capitalizing costs related to inventory manufacturing. 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. Intangible assets The Company had no intangible assets as of December 31, 2018. The Company received FDA approval for ZULRESSO on March 19, 2019 (“CyDex”) . 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 lease 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 that option. The Company uses the implicit interest rate when readily determinable and uses the Company’s incremental borrowing rate when the implicit rate is not readily determinable based upon the information available at the commencement date 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 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 excluded from this treatment and are recognized 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; maintenance and tolls for leased vehicles, and 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. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. 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 on March 19, 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 current period. 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 may be 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. Patent Costs The Company expenses patent costs as incurred and classifies such costs as selling, general and administrative expenses in the accompanying consolidated statements of operations and comprehensive loss. Stock-Based Compensation The Company recognizes compensation expense for stock-based awards, including grants of stock options and restricted stock units, made to employees and non-employee directors 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. Effective January 1, 2019, the Company recognizes compensation expense for stock-based awards, including grants of stock options and restricted stock units, made to non-employee consultants based on the estimated fair value on the date of grant, over the requisite service period. Through December 31, 2018, the Company recognized compensation expense for stock-based awards granted to non-employee consultants based on the fair value of the awards on each date on which the awards vest. Compensation expense was recognized over the vesting period, provided that services were rendered by such non-employee consultants during that time. At the end of each financial reporting period, the fair value of unvested options was re-measured using the then-current fair value of the common stock of the Company and updated assumptions using the Black-Scholes option-pricing model. 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. The fair value of each option grant is estimated using the Black-Scholes option-pricing model. Through December 31, 2015, the Company lacked sufficient Company-specific historical and implied volatility information, and as a result, the Company used the volatility of a group of publicly-traded peer companies in the Black-Scholes calculations. Beginning in 2016, 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 and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its common stock price for the duration of the expected term. The expected term of the options granted to employees and non-employee directors by the Company has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. Through December 31, 2018, the expected term of its options granted to non-employee consultants has been determined based on the contractual term of the options, and effective January 1, 2019, the “simplified” method is used. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award 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 received from an employee as consideration for exercises of stock options. Basic and Diluted Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding for the period. 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 antidilutive. The Company reported a net loss for the years ended December 31, 2019, 2018 and 2017. Risks and Uncertainties The product candidates developed by the Company require approvals from the U.S. Food and Drug Administration 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 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, it may have a material adverse impact on the Company’s business and its financial statements. 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 in its programs. The Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs. 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 ASC 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, 2019 and 2018 were carried at fair value, determined according to the fair value hierarchy; see Footnote 3, Fair Value Measurements. The carrying amounts reflected in the consolidated balance sheets for accounts payable and accrued expenses approximate their fair values due to their short-term maturities at December 31, 2019 and 2018, 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 medicines with the potential to transform the lives of people with debilitating disorders of the brain. Comprehensive Loss Comprehensive loss includes net loss and other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. Public Offerings On July 23, 2014, the Company completed the sale of 5,750,000 shares of its common stock in its IPO at a price to the public of $18.00 per share, resulting in net proceeds to the Company of $94.0 million after deducting underwriting discounts and commissions and offering costs paid by the Company. The shares began trading on the Nasdaq Global Market on July 18, 2014. On April 20, 2015, the Company completed the sale of 2,628,571 shares of its common stock at a price to the public of $52.50 per share, resulting in net proceeds to the Company of $129.1 million after deducting underwriting discounts and commissions and offering costs paid by the Company. On January 12, 2016, the Company completed the sale of 3,157,894 shares of its common stock at a price to the public of $47.50 per share, resulting in net proceeds to the Company of $140.4 million after deducting underwriting discounts and commissions and offering costs paid by the Company. On September 14, 2016, the Company completed the sale of 5,062,892 shares of its common stock at a price to the public of $39.75 per share, resulting in net proceeds to the Company of $189.2 million after deducting underwriting discounts and commissions paid by the Company. On November 17, 2017, the Company completed the sale of 4,058,822 shares of its common stock at a price to the public of $85.00 per share, resulting in net proceeds to the Company of $325.8 million after deducting underwriting discounts and commissions and offering costs paid by the Company. On February 13, 2018, the Company completed the sale of 4,032,012 shares of its common stock at a price to the public of $164.00 per share, resulting in net proceeds to the Company of $631.2 million after deducting underwriting discounts and commissions and offering costs paid by the Company. 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. Revenue Recognition Effective January 1, 2017, the Company adopted Accounting Standards Codification (“ASC”), Topic 606, Revenue from Contracts with Customers The Company received approval of ZULRESSO from the FDA in March 2019 and subsequently began to record revenues from product sales in June 2019. Prior to the second quarter of 2019, all of the revenues of the Company were derived from the Company’s collaboration agreement with Shionogi & Co., Ltd., (“Shionogi”). The terms of the Company’s collaboration agreement include consideration such as non-refundable license fees, reimbursement of any development costs the Company incurs on behalf of Shionogi, payments due upon the achievement of clinical and pre-clinical performance-based development milestones, regulatory milestones, manufacturing services to supply drug product for clinical trials, and sales-based milestones and royalties on product sales. Under 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 arrangement with Shionogi and concluded that a significant financing component does not exist. 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

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
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 Account Policies, 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 following tables summarize the Company’s money market funds and marketable securities as of December 31, 2019 and 2018 : December 31, 2019 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 $ 126,705 $ 65,414 $ 61,291 $ — Total cash equivalents 126,705 65,414 61,291 — Marketable securities: U.S. government securities 205,328 — 205,328 — U.S. corporate bonds 429,845 — 429,845 — International corporate bonds 142,998 — 142,998 — U.S. commercial paper 52,261 — 52,261 — International commercial paper 51,256 — 51,256 — Total marketable securities 881,688 — 881,688 — $ 1,008,393 $ 65,414 $ 942,979 $ — December 31, 2018 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 $ 190,943 $ 190,943 $ — $ — Total cash equivalents 190,943 190,943 — — Marketable securities: U.S. government securities 220,482 — 220,482 — U.S. corporate bonds 258,566 — 258,566 — International corporate bonds 78,468 — 78,468 — U.S. commercial paper 77,611 — 77,611 — International commercial paper 96,706 — 96,706 — Total marketable securities 731,833 — 731,833 — $ 922,776 $ 190,943 $ 731,833 $ — During the years ended December 31, 2019 and 2018, there were no transfers among the Level 1, Level 2 and Level 3 categories. Marketable Securities The following tables summarize the gross unrealized gains and losses of the Company’s marketable securities as of December 31, 2019 and 2018: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in thousands) Assets: U.S. government securities $ 205,172 $ 176 $ (20 ) $ 205,328 U.S. corporate bonds 429,148 797 (100 ) 429,845 International corporate bonds 142,568 457 (27 ) 142,998 U.S. commercial paper 52,252 14 (5 ) 52,261 International commercial paper 51,253 5 (2 ) 51,256 $ 880,393 $ 1,449 $ (154 ) $ 881,688 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in thousands) Assets: U.S. government securities $ 220,531 $ 8 $ (57 ) $ 220,482 U.S. corporate bonds 258,876 6 (316 ) 258,566 International corporate bonds 78,600 — (132 ) 78,468 U.S. commercial paper 77,630 8 (27 ) 77,611 International commercial paper 96,711 8 (13 ) 96,706 $ 732,348 $ 30 $ (545 ) $ 731,833 As of December 31, 2019 and 2018, 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 $137.1 million and $5.9 million, respectively, that had maturities of one to two years. As of December 31, 2019 and 2018, the marketable securities in a loss position have 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, 2019 and 2018.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2019
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, 2019 2018 (in thousands) Computer hardware and software $ 2,830 $ 2,148 Furniture and equipment 1,828 1,002 Leasehold improvements 8,967 4,709 13,625 7,859 Less: Accumulated depreciation (4,499 ) (2,216 ) $ 9,126 $ 5,643 Depreciation expense for the years ended December 31, 2019, 2018 and 2017 was $2.3 million, $1.1 million and $0.5 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, 2019 2018 (in thousands) Accrued research and development costs $ 46,940 $ 21,216 Employee-related expenses 22,011 19,638 Professional services 16,720 10,903 Other 947 237 $ 86,618 $ 51,994

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	5. Commitments and Contingencies Operating Leases The Company has leases for office space, vehicles, 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 six years. Some of the leases include options to extend the leases for up to five years and 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, 2018, the Company leases office space in two multi-tenant buildings in Cambridge, Massachusetts, consisting of 54,943 square feet in the first building under an operating lease that will expire on August 15, 2024 and 19,805 square feet in the second building under an operating lease that will expire on February 28, 2022. In April 2018, the Company entered into the First Amendment to the lease for office space in the second multi-tenant building and thereby increased the amount of square feet of office space from 19,805 square feet to 40,419 square feet, an increase of 20,614 square feet, consisting of (i) 13,481 square feet that began on August 1, 2018, and (ii) 7,133 square feet that began on October 1, 2018. The term for this additional space will expire on August 31, 2024 . Additionally, the term of the existing lease was extended from February 28, 2022 until August 31, 2024. In May 2018, the Company entered into a lease for office space in a multi-tenant building in Raleigh, North Carolina. The amount of square feet of office space is 15,525 square feet and the lease period began on September 1, 2018. The term for this space will expire on November 30, 2024. In October 2018, the Company entered into the Seventh Amendment to the lease for office space in the first building and thereby increased the amount of square feet of office space from 54,943 square feet to 58,442 In December 2018, the Company entered into a lease in a third multi-tenant building in Cambridge, Massachusetts, for 15,975 square feet of office space which will begin on March 1, 2019. The term for this lease will expire on February 29, 2024. In March 2019, the Company entered into the Eighth Amendment to the lease for office space in the first multi-tenant building 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. From June 2018 to January 2019, the Company entered 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 are for a term of three years and will expire on various dates through January 31, 2022. Rent expense for the years ended December 31, 2019, 2018 and 2017, was $10.2 million, $6.5 million, and $3.7 million, respectively. The following table summarizes the presentation of operating leases in the Company’s consolidated balance sheet: (In thousands) Balance sheet location As of December 31, 2019 Assets Right-of-use operating asset Right-of-use operating asset $ 33,771 Liabilities Current operating lease liabilities Operating lease liabilities, current portion 10,244 Long-term operating lease liabilities Operating lease liability, net of current portion 26,848 Total operating lease liabilities $ 37,092 The following table summarizes the lease costs recorded in the Company’s consolidated statements of operations and comprehensive loss: Year Ended (In thousands) December 31, 2019 Operating lease cost $ 9,804 Variable lease cost 2,675 Short-term lease cost 438 $ 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 in the consolidated statements of operations and comprehensive loss 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) 2020 $ 10,244 2021 9,972 2022 8,898 2023 9,105 2024 5,560 Thereafter - Total lease payments 43,779 Less imputed interest (6,687 ) Present value of operating lease liabilities $ 37,092 Under the prior lease guidance, future minimum lease payments under non-cancelable operating leases are as follows at December 31, 2018: Years Ending December 31, (In thousands) 2019 $ 7,918 2020 8,299 2021 8,463 2022 8,692 2023 8,894 Thereafter 5,415 $ 47,681 The weighted average remaining lease term and weighted average discount rate of the Company’s operating leases are as follows: As of December 31, 2019 Weighted average remaining lease term in years 4.39 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 Company’s operating leases included in cash flows used by operating activities in the consolidated statements of cash flows is as follows: Year Ended (In thousands) December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities $ 9,946 Right-of-use assets obtained in exchange for lease obligations: Operating leases $ 872 During the year ended December 31, 2019, other than the initial adoption of the lease standard that required right-of-use assets and lease liabilities to be recorded, one right-of-use asset was recorded arising from new lease liabilities. In March 2019, the Company entered into the Eighth Amendment to the lease for office space in the first building 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. License Agreements CyDex License Agreement In September 2015, the Company and CyDex 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 in 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 sales of SAGE-689, if successfully developed in the future The Company is obligated to make milestone payments under the amended and restated license agreement with CyDex based 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, 2019, the Company has recorded research and development expense and made cash payments of $2.3 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, 2017, the Company did not record any expense or make any milestone payments related to clinical development or regulatory milestones for the brexanolone program under the license agreement with CyDex. For the year ended December 31, 2018, 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 made cash payments totaling $0.8 million. For the year ended December 31, 2019 , the Company recorded an intangible asset and made a cash payment of $3.0 million related to a regulatory milestone for the brexanolone program under the license agreement with CyDex. As of December 31, 2019, the Company has made no milestone payments related to clinical development or regulatory milestones for SAGE-689 under the license agreement with CyDex. University of California License Agreements In October 2013, the Company entered into a non-exclusive license agreement with The Regents of the University of California 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. As of December 31, 2015, the Company paid to The Regents of the University of California clinical development milestones of $0.1 million. 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 of the University of California 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. Following the first sale of a licensed product, the Company is required to pay royalties at a low single digit percentage of net sales of licensed products, 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, 2019, 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, 2017, the Company did not record any expense or make any milestone or royalty payments under the license agreements with The Regents of the University of California. For the year ended December 31, 2018, the Company recorded research and development expense and made cash payments of $0.2 million related to regulatory milestones under the license agreements with The Regents of the University of California. For the year ended December 31, 2019, the Company recorded an intangible asset and made a cash payment of $0.5 million related to a regulatory milestone under the license agreements with The Regents of the University of California. Washington University License Agreement In November 2013, the Company entered into a license agreement with Washington University whereby the Company was granted exclusive, worldwide rights to develop and commercialize a novel set of neuroactive steroids developed by Washington University. In exchange for development and commercialization rights, the Company paid an upfront, non-refundable payment of $50,000 and is required to pay an annual license maintenance fee of $15,000 on each subsequent anniversary date, until the first Phase 2 clinical trial for a licensed product is initiated. The Company is obligated to make milestone payments to Washington University based on achievement of clinical development and regulatory milestones of up to $0.7 million and $0.5 million, respectively. Additionally, the Company fulfilled its obligation to issue to Washington University 47,619 shares of common stock on December 13, 2013. The fair value of these shares of $0.1 million was recorded as research and development expense in 2013. As of December 31, 2019, the Company has recorded research and development expense and made a cash payment of $50,000 related to these clinical and development milestones. The Company is obligated to pay royalties to Washington University at rates in the low single digits on net sales of licensed products covered under patent rights and royalties at rates in the low single digits on net sales of licensed products not covered under patent rights. Additionally, the Company has the right to sublicense and is required to make payments at varying percentages of sublicensing revenue received, initially in the mid-teens and descending to the mid-single digits over time. For the years ended December 31, 2019, 2018 and 2017, the Company did not record any expense or make any milestone payments under the license agreement with Washington University. Consulting Agreement In January 2014, the Company entered into a consulting agreement with a then non-employee advisor whereby the Company agreed to make cash payments of up to $2.0 million and to issue up to 126,984 shares of common stock upon attainment of certain clinical development and regulatory milestones. As of December 31, 2019, the Company recorded research and development expense of $1.8 million, comprised of $0.5 million in cash and $1.3 million related to the issuance of 39,681 shares of the Company’s common stock, related to the achievement of these milestones. For the years ended December 31, 2019, 2018 and 2017, the Company did not record any expense or make any milestone payments under the consulting agreement with the non-employee advisor.

Collaboration Agreement

Collaboration Agreement	12 Months Ended
	Dec. 31, 2019
Collaboration Agreement [Abstract]
Collaborative Agreement	6. Collaboration Agreement Effective June 12, 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. On October 26, 2018, the Company entered into a supply agreement with Shionogi for zuranolone clinical material. Under the terms of the collaboration and license agreement, Shionogi will be responsible for all clinical development, regulatory filings and commercialization of zuranolone for MDD, and potentially other indications, in Japan, Taiwan and South Korea. 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. Due to the uncertainty of pharmaceutical development and the high historical failure rates generally associated with drug development, the Company may not receive any additional 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 ASC 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 included the license to zuranolone , supply of certain clinical materials and manufacturing supply of the active pharmaceutical ingredient (“API”). The performance obligation related to the license to zuranolone was determined to be distinct from other performance obligations and therefore was a standalone performance obligation for which control was transferred upon signing. The obligation to provide certain clinical materials was determined to be a separate performance obligation. The supply agreement related for API was determined to be an option for Shionogi to purchase, rather than a firm obligation , because no minimum amount or quantities are specified and therefore, was not considered a performance obligation within the main agreement. Given this fact pattern, the Company has concluded the agreement has two performance obligations. Under the 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 studies of zuranolone in the Shionogi territory under the collaboration and license agreement, in the quantities agreed to by the parties. Collaboration revenue from the supply agreement, which excludes the $90.0 million upfront payment, pertains to the clinical material sold under the terms of the supply agreement. The Company records the costs related to the supply agreement in research and development expense on its consolidated statements of operations and comprehensive loss. 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.

Preferred Stock

Preferred Stock	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Preferred Stock	7 . Preferred Stock The Board of Directors of the Company 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 of Directors of the Company can designate the rights, preferences and privileges of the shares of each series and any of its qualifications, limitations or restrictions. The Board of Directors of the Company 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, 2019 and 2018, the Company had no shares of preferred stock issued or outstanding and preferred stock was classified as stockholders’ equity.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2019
Text Block [Abstract]
Common Stock	8 . Common Stock As of December 31, 2019 and 2018, 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 of Directors, if any. As of December 31, 2019 and 2018, no dividends have been declared. As of December 31, 2019, the Company received 3,033 shares of the Company’s common stock from an employee as proceeds for exercises of stock options. The total cost of shares held in treasury at December 31, 2019 was $0.4 million.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9 . Stock-Based Compensation Restricted Stock Units During the year ended December 31, 2017, the Company granted 32,500 restricted stock units to employees of the Company. The Company did not grant restricted stock units prior to January 1, 2017. These restricted stock units vested ratably over two years, with cliff 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 restricted stock units that vested during the years ended December 31, 2019 and 2018 was $2.0 million and $2.6 million, respectively. No restricted stock units vested during the year ended December 31, 2017. During the year ended December 31, 2018, the Company granted 71,400 performance restricted stock units to employees of the Company. The milestones for 33,600 grants were not met, and accordingly, these grants were cancelled. 37,800 performance restricted stock units will vest upon the achievement of a certain commercial milestone. 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. 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. During the year ended December 31, 2019, one milestone was achieved for a grant that was made during the year. This milestone represents 18% of the performance restricted stock units that were granted during the year ended December 31, 2019. The fair value of performance restricted stock units that vested during the year ended December 31, 2019 was $11.1 million. No performance restricted stock units vested during the year ended December 31, 2018. The table below summarizes activity relating to restricted stock units: Shares Outstanding as of December 31, 2018 82,700 Granted 393,539 Vested (82,128 ) Forfeited (60,868 ) Outstanding as of December 31, 2019 333,243 At December 31, 2019, 333,243 performance restricted stock units were both outstanding and unvested, and the total unrecognized stock-based compensation expense related to those awards was $52.6 million. 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 options outstanding under the 2011 Plan remain outstanding and effective. 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, 2019, 1,875,530 shares of common stock, representing 4% of the Company’s outstanding shares of common stock as of December 31, 2018, were added to the 2014 Plan. On December 15, 2016, the Board of Directors of the Company (the “Board”) approved the 2016 Inducement Equity Plan (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 under such plan 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. Options granted by the Company, that are not performance-based, generally 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% cliff vesting at the one-year Performance-Based Stock Options During the years ended December 31, 2018 and 2017, the Company granted 524,003 and 449,208 options, respectively, to employees to purchase shares of common stock that contain performance-based vesting criteria, primarily related to the achievement of certain clinical and regulatory development milestones related to product candidates and commercial milestones. During the year ended December 31, 2019, the Company did not grant 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. During the year ended December 31, 2017, no milestones were achieved. During the year ended December 31, 2018, a milestone was achieved under a stock option granted to a consultant. The milestone was related to the consummation of a licensing or corporate partnering arrangement. During the year ended December 31, 2018, the Company recognized stock-based compensation expense related to this milestone of $6.9 million. During the year ended December 31, 2018, one milestone was achieved. This milestone represents 33% of the performance-based option grants that were made during the year ended December 31, 2017. During the year ended December 31, 2018, the Company recognized stock-based compensation expense related to this milestone of $4.4 million. During the year ended December 31, 2018, the remaining milestone for the performance-based option grants that were made during the years ended December 31, 2016 and December 31, 2015 was not met, and accordingly, those options were cancelled. This milestone represents 50% and 35% of the performance-based option grants that were made during the years ended December 31, 2016 and December 31, 2015, respectively. The Company recognized no stock-based compensation expense related to this milestone. During the year ended December 31, 2019, one milestone was achieved. This milestone represents 20% and 33% of the performance-based 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. As of December 31, 2019, 2018 and 2017 for option grants that were outstanding, the achievement of the milestones that had not been met that are the criteria for vesting of performance-based stock options was considered not probable, and therefore no expense has been recognized related to these awards in the years ended December 31, 2019, 2018 and 2017, respectively. Stock-Based Compensation Expense Stock-based compensation expense recognized during the years ended December 31, 2019, 2018 and 2017 was as follows: 2019 2018 2017 (in thousands) Research and development $ 62,931 $ 50,871 $ 19,893 Selling, general and administrative 90,300 51,092 15,641 $ 153,231 $ 101,963 $ 35,534 Stock-based compensation expense by award type recognized during the years ended December 31, 2019, 2018 and 2017 was as follows: 2019 2018 2017 (in thousands) Stock options $ 140,517 $ 100,342 $ 34,525 Restricted stock units 10,992 651 617 Employee stock purchase plan 1,722 970 392 $ 153,231 $ 101,963 $ 35,534 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 options are granted. The fair value of the options is amortized on a straight-line basis for awards to employees over the requisite service period of the awards. For awards to non-employees, the fair value of the options was amortized on a graded basis through December 31, 2018, and starting on January 1, 2019, on a straight-line basis, 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 equity plans during the years ended December 31, 2019, 2018 and 2017 was $82.39, $109.92 and $41.94, respectively. The fair value of each 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, 2019 2018 2017 Expected dividend yield 0 % 0 % 0 % Expected volatility 71.34 % 74.45 % 79.89 % Risk-free interest rate 2.21 % 2.68 % 2.03 % Expected life of option 6.05 years 6.04 years 6.03 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: the Company does not have sufficient history to support a calculation of volatility using only its historical data. Starting in 2016, the Company uses a weighted-average volatility considering the Company’s own volatility since the IPO in July 2014 and the volatilities of a peer group of comparable companies for time periods prior to the IPO. Prior to 2016, the Company used volatilities based on an analysis of reported data for a peer group of comparable companies. Expected term (in years): the expected term represents the period that the Company’s stock option grants are expected to be outstanding. The Company has been publicly-traded since July 2014, and there is not sufficient historical term data to calculate the expected term of the options. Therefore, the Company elected to utilize the “simplified” method to estimate the expected term of options granted to employees. Under this approach, the weighted average expected life is presumed to be the average of the vesting term and the contractual term of the 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, 2019, 2018 and 2017, the weighted-average forfeiture rates were 13.7%, 10.7% and 13.3%, respectively. Through December 31, 2018, for options granted to non-employees, the expected term is 10 years, which is the contractual term of each option. All other assumptions used to calculate the grant date fair value for non-employees are generally consistent with the assumptions used for options granted to employees. Option Rollforward and Other 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, 2018 7,530,767 $ 93.22 8.03 $ 227,447 Granted 2,215,606 129.15 Exercised (1,031,989 ) 42.72 Forfeited (551,271 ) 138.35 Outstanding as of December 31, 2019 8,163,113 $ 106.30 7.75 $ 87,972 Vested and expected to vest as of December 31, 2019 7,035,349 $ 102.32 7.63 $ 84,442 Exercisable as of December 31, 2019 3,737,468 $ 78.55 6.63 $ 77,652 At December 31, 2019, the Company had unrecognized stock-based compensation expense related to its unvested service-based stock option awards of $283.4 million, which is expected to be recognized over the remaining weighted average vesting period of 2.44 years. At December 31, 2019, 485,595 performance-based stock options were both outstanding and unvested, and the total unrecognized stock-based compensation expense related to those awards was $35.7 million. The intrinsic value of stock options exercised during the years ended December 31, 2019, 2018 and 2017 was $119.1 million, $98.3 million and $77.7 million, respectively. 2014 Employee Stock Purchase Plan On July 2, 2014, the Company’s stockholders approved the 2014 Employee Stock Purchase Plan, which had been previously approved by the Board of Directors. The 2014 Employee Stock Purchase Plan became effective upon the completion of the IPO. A total of 282,000 shares of common stock were authorized for issuance under this plan. As of December 31, 2019, 105,160 shares have been issued under this plan and 176,840 shares are available for issuance under this plan. At December 31, 2019, accrued expenses includes $0.7 million of stock-based compensation expense related to an enrollment period for which the related shares had not been issued as of December 31, 2019. Shares Reserved and Available for Future Issuance As of December 31, 2019, the total number of shares reserved under all equity plans was 10,651,531 and the total number of shares available for future issuance under all equity plans was 2,155,175.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	10 . Net Loss Per Share Basic and diluted net loss per share was calculated as follows for the years ended December 31, 2019, 2018 and 2017: Year Ended December 31, 2019 2018 2017 Basic net loss per share: Numerator: Net loss (in thousands) $ (680,238 ) $ (372,882 ) $ (270,120 ) Denominator: Weighted average common stock outstanding —basic 50,833,837 46,121,194 38,113,678 Dilutive effect of shares of common stock equivalents resulting from common stock options and restricted stock units — — — Weighted average common stock outstanding —diluted 50,833,837 46,121,194 38,113,678 Net loss per share—basic and diluted $ (13.38 ) $ (8.08 ) $ (7.09 ) The following common stock equivalents outstanding as of December 31, 2019, 2018 and 2017 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, 2019 2018 2017 Stock options 7,677,518 6,758,420 4,915,956 Restricted stock units — 13,500 29,100 Employee stock purchase plan 33,429 16,398 11,683 7,710,947 6,788,318 4,956,739 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

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	1 1 . Income Taxes There is no current or deferred provision for income taxes because the Company has historically incurred operating losses and maintains 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 valuation allowance A reconciliation of the U.S. statutory rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2019 2018 2017 Tax due at statutory rate 21.0 % 21.0 % 34.0 % State taxes, net of federal 2.8 6.0 5.1 Stock-based compensation 1.4 2.5 6.4 Foreign rate differential (1.6 ) (4.3 ) (3.2 ) Federal and state credits 2.4 2.5 7.2 Change in valuation allowance (25.8 ) (27.6 ) (22.5 ) Other 0.5 (0.1 ) — Federal and state rate change (0.7 ) — (24.6 ) Research and orphan drug credit addback — — (2.4 ) 0.0 % 0.0 % 0.0 % Significant components of the Company’s net deferred tax asset at December 31, 2019 and 2018 are as follows: December 31, 2019 2018 (in thousands) Net operating losses $ 348,848 $ 206,460 Capitalized start-up costs 982 1,242 Tax credit carryforwards 80,088 63,653 Accrued expenses 4,055 4,498 Depreciation and amortization 2,002 1,001 Stock options 46,750 30,925 Right of use asset (8,059 ) — Right of use liability 8,852 — Other (246 ) 568 Total net deferred tax asset before valuation allowance 483,272 308,347 Valuation allowance (483,272 ) (308,347 ) Net deferred tax asset $ — $ — As of December 31, 2019, the Company had federal and state net operating loss carryforwards of $1.4 $1.0 2031 $34.2 2031 $40.0 On December 22, 2017, the President of the U.S. signed into law the Tax Cuts and Jobs Act (“The TCJA”). This legislation reduced the U.S. corporate tax rate from the existing rate of 34% to 21% for tax years beginning after December 31, 2017. As a result of the enacted law, the Company was required to revalue deferred tax assets and liabilities existing as of December 31, 2017 from the 34% federal rate in effect through the end of 2017, to the new 21% rate. This revaluation resulted in a reduction to the Company’s deferred tax asset of $66.4 million as of December 31, 2017. This amount was offset by a corresponding reduction to the Company’s valuation allowance. The other provisions of the TCJA did not have a material impact on the December 31, 2017 consolidated financial statements. Our final determination of the TCJA impact and the remeasurement of our deferred assets and liabilities was completed prior to the deadline of one year from the enactment of the TCJA. For the year ended December 31, 2019, there were no material changes to our analysis originally performed as of December 31, 2017. As of December 31, 2019, net deferred tax assets increased approximately $174.9 million, primarily due to the operating loss, timing differences related to stock-based compensation and tax credits incurred during the year. 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 net operating loss carryforwards 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 federal and state deferred tax assets. Accordingly, a full valuation allowance of $483.3 million and $308.3 million has been established at December 31, 2019 and 2018, respectively. 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 carryforwards and tax carryforwards that may be used in future years. Utilization of the net operating loss (“NOL”) and tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of NOL and tax credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company completed a detailed Section 382 study during 2017 on its Net Operating Losses and Credits incurred from the year it began operations in 2011 through December 31, 2016. 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, all of the Company’s NOL and Tax Credit carryforwards as of the ownership change dates are subject to limitation under Section 382. Any NOLs 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 carryforwards that could be utilized to offset future taxable income. 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. At December 31, 2019, 2018 and 2017, the Company had no unrecognized tax benefits. The Company’s policy is to record interest and penalties related to income taxes as part of the tax provision. As of December 31, 2019 and 2018, the Company had no accrued interest or penalties related to income taxes and no amounts have been recognized in the Company’s statement of operations. 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 2016 to the present. The tax attributes prior to 2016 may still be adjusted upon examination.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2019
Postemployment Benefits [Abstract]
Employee Benefit Plan	1 2 . Employee Benefit Plan The Company maintains a 401(k) profit sharing plan (the “Plan”) for its employees. Each employee may elect to contribute a portion of his or her compensation to the Plan, subject to annual limits established by the Internal Revenue Service. For the years ended December 31, 2019, 2018 and 2017, the Company matched 50% of eligible contributions up to 6% of employee contributions. For the years ended December 31, 2019, 2018 and 2017 the Company contributed $3.6 million, $1.8 million and $0.9 million, respectively.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	1 3 . Selected Quarterly Financial Data (Unaudited) The following table contains quarterly financial information for 2019 and 2018. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period. 2019 First Quarter Second Quarter Third Quarter Fourth Quarter Total (in thousands, except per share amounts) Total revenue $ 465 $ 873 $ 3,570 $ 1,960 $ 6,868 Total operating costs and expenses 170,317 177,330 190,747 176,598 714,992 Loss from operations (169,852 ) (176,457 ) (187,177 ) (174,638 ) (708,124 ) Net loss (163,406 ) (168,221 ) (179,958 ) (168,653 ) (680,238 ) Net loss per share—basic and diluted $ (3.37 ) $ (3.28 ) $ (3.48 ) $ (3.25 ) $ (13.38 ) 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total (in thousands, except per share amounts) Total revenue $ — $ 90,000 $ — $ 273 $ 90,273 Total operating expenses 78,119 112,147 128,745 164,500 483,511 Loss from operations (78,119 ) (22,147 ) (128,745 ) (164,227 ) (393,238 ) Net loss (74,598 ) (16,978 ) (122,918 ) (158,388 ) (372,882 ) Net loss per share—basic and diluted $ (1.68 ) $ (0.36 ) $ (2.63 ) $ (3.38 ) (8.08 )

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	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 United States of America (“GAAP”).
Use of Estimates	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. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of 90 days or less at the date of purchase to be cash equivalents. As of December 31, 2019 and December 31, 2018, cash equivalents were comprised of cash equivalents, commercial paper and money market funds.
Marketable 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. Realized gains and losses and declines in value judged to be other than temporary are included as a component of other expense, net, based on the specific identification method. When determining whether a decline in value is other than temporary, the Company considers several factors, including whether the Company has the intent to sell the security, and whether it is more likely than not that the Company will be required to sell the security prior to recovery of its amortized cost basis. No declines in value were deemed to be other than temporary during the years ended December 31, 2019 and December 31, 2018.
Restricted Cash	Restricted Cash For the initial facility of the Company, a deposit of $39,000 was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing the initial lease and the restriction will expire in 2024, in accordance with the most recent amendment to the operating lease agreement. A deposit of $0.3 million was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing an amendment to the lease of the initial facility of the Company and the restriction will expire in 2024, in accordance with the most recent amendment to the operating lease agreement. These balances are included in restricted cash on the accompanying consolidated balance sheets. A deposit of $0.5 million was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing the separate facility lease on the second multi-tenant building in May 2016 and the restriction will expire in 2024, in accordance with the most recent amendment to the operating lease agreement. A deposit of $0.4 million was restricted from withdrawal as of December 31, 2018. The restriction is related to securing an amendment to the lease of the separate facility of the Company and the restriction will expire in 2024, in accordance with the most recent amendment to the operating lease agreement. These balances are included in restricted cash on the accompanying consolidated balance sheets. A deposit of $0.4 million was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing a separate facility lease on the third multi-tenant building in December 2018 that will expire on February 29, 2024, under which, beginning on March 1, 2019, the Company will rent 15,975 square feet of additional office space. The restriction will expire in 2024, in accordance with the operating lease agreement. This balance is included in restricted cash on the accompanying consolidated balance sheet. A deposit of $0.7 million was restricted from withdrawal as of December 31, 2019 and 2018. The restriction is related to securing leases on automobiles for employees who are based in the field. The restriction will expire in 2021, in accordance with the lease agreement. This balance is included in restricted cash on the accompanying consolidated balance sheet.
Accounts Receivable	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, or 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 profile. The Company reserves against trade accounts receivable for estimated losses that may arise from a customer’s inability to pay and any amounts determined to be uncollectible are written off against the reserve when it is probable that the receivable will not be collected. Trade accounts receivable are included in prepaid expenses and other current assets on the consolidated balance sheets and the amount was not significant as of December 31, 2019.
Inventory	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 identical and, as a result, are both classified as inventory. Amounts in inventory associated with research and development 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 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 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, 2019. Prior to the initial date 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 loss in the period incurred. The Company received FDA approval for ZULRESSO on March 19, 2019 and subsequently began capitalizing costs related to inventory manufacturing.
Property and Equipment	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.
Intangible Assets	Intangible assets The Company had no intangible assets as of December 31, 2018. The Company received FDA approval for ZULRESSO on March 19, 2019 (“CyDex”) .
Leases	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 lease 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 that option. The Company uses the implicit interest rate when readily determinable and uses the Company’s incremental borrowing rate when the implicit rate is not readily determinable based upon the information available at the commencement date 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 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 excluded from this treatment and are recognized 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; maintenance and tolls for leased vehicles, and are expensed when incurred.
Impairment of Long-Lived Assets	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. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. 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 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 on March 19, 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 current period.
Research and Development Costs and Accruals	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 may be 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.
Patent Costs	Patent Costs The Company expenses patent costs as incurred and classifies such costs as selling, general and administrative expenses in the accompanying consolidated statements of operations and comprehensive loss.
Stock-Based Compensation	Stock-Based Compensation The Company recognizes compensation expense for stock-based awards, including grants of stock options and restricted stock units, made to employees and non-employee directors 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. Effective January 1, 2019, the Company recognizes compensation expense for stock-based awards, including grants of stock options and restricted stock units, made to non-employee consultants based on the estimated fair value on the date of grant, over the requisite service period. Through December 31, 2018, the Company recognized compensation expense for stock-based awards granted to non-employee consultants based on the fair value of the awards on each date on which the awards vest. Compensation expense was recognized over the vesting period, provided that services were rendered by such non-employee consultants during that time. At the end of each financial reporting period, the fair value of unvested options was re-measured using the then-current fair value of the common stock of the Company and updated assumptions using the Black-Scholes option-pricing model. 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. The fair value of each option grant is estimated using the Black-Scholes option-pricing model. Through December 31, 2015, the Company lacked sufficient Company-specific historical and implied volatility information, and as a result, the Company used the volatility of a group of publicly-traded peer companies in the Black-Scholes calculations. Beginning in 2016, 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 and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its common stock price for the duration of the expected term. The expected term of the options granted to employees and non-employee directors by the Company has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. Through December 31, 2018, the expected term of its options granted to non-employee consultants has been determined based on the contractual term of the options, and effective January 1, 2019, the “simplified” method is used. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award 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	Treasury Stock The Company records treasury stock at cost. Treasury stock consists of shares received from an employee as consideration for exercises of stock options.
Basic and Diluted Net Loss Per Share	Basic and Diluted Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding for the period. 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 antidilutive. The Company reported a net loss for the years ended December 31, 2019, 2018 and 2017.
Risks and Uncertainties	Risks and Uncertainties The product candidates developed by the Company require approvals from the U.S. Food and Drug Administration 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 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, it may have a material adverse impact on the Company’s business and its financial statements.
Concentration of Credit Risk and of Significant Suppliers	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 in its programs. The Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs.
Income Taxes	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 ASC 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 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, 2019 and 2018 were carried at fair value, determined according to the fair value hierarchy; see Footnote 3, Fair Value Measurements. The carrying amounts reflected in the consolidated balance sheets for accounts payable and accrued expenses approximate their fair values due to their short-term maturities at December 31, 2019 and 2018, respectively.
Segment Data	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 medicines with the potential to transform the lives of people with debilitating disorders of the brain.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss and other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders.
Public Offerings	Public Offerings On July 23, 2014, the Company completed the sale of 5,750,000 shares of its common stock in its IPO at a price to the public of $18.00 per share, resulting in net proceeds to the Company of $94.0 million after deducting underwriting discounts and commissions and offering costs paid by the Company. The shares began trading on the Nasdaq Global Market on July 18, 2014. On April 20, 2015, the Company completed the sale of 2,628,571 shares of its common stock at a price to the public of $52.50 per share, resulting in net proceeds to the Company of $129.1 million after deducting underwriting discounts and commissions and offering costs paid by the Company. On January 12, 2016, the Company completed the sale of 3,157,894 shares of its common stock at a price to the public of $47.50 per share, resulting in net proceeds to the Company of $140.4 million after deducting underwriting discounts and commissions and offering costs paid by the Company. On September 14, 2016, the Company completed the sale of 5,062,892 shares of its common stock at a price to the public of $39.75 per share, resulting in net proceeds to the Company of $189.2 million after deducting underwriting discounts and commissions paid by the Company. On November 17, 2017, the Company completed the sale of 4,058,822 shares of its common stock at a price to the public of $85.00 per share, resulting in net proceeds to the Company of $325.8 million after deducting underwriting discounts and commissions and offering costs paid by the Company. On February 13, 2018, the Company completed the sale of 4,032,012 shares of its common stock at a price to the public of $164.00 per share, resulting in net proceeds to the Company of $631.2 million after deducting underwriting discounts and commissions and offering costs paid by the Company. 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.
Revenue Recognition	Revenue Recognition Effective January 1, 2017, the Company adopted Accounting Standards Codification (“ASC”), Topic 606, Revenue from Contracts with Customers The Company received approval of ZULRESSO from the FDA in March 2019 and subsequently began to record revenues from product sales in June 2019. Prior to the second quarter of 2019, all of the revenues of the Company were derived from the Company’s collaboration agreement with Shionogi & Co., Ltd., (“Shionogi”). The terms of the Company’s collaboration agreement include consideration such as non-refundable license fees, reimbursement of any development costs the Company incurs on behalf of Shionogi, payments due upon the achievement of clinical and pre-clinical performance-based development milestones, regulatory milestones, manufacturing services to supply drug product for clinical trials, and sales-based milestones and royalties on product sales. Under 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 arrangement with Shionogi and concluded that a significant financing component does not exist. 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. To date, revenue from the Company’s collaboration agreement with Shionogi has come from an initial, upfront fee upon execution of the agreement and for the supply of drug product for Shionogi’s clinical trials. Product revenue 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 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, 2019, as customer invoicing generally occurs before or at the time of revenue recognition. The Company did not have any contract liabilities at December 31, 2019, as the Company did not receive any payments in advance of satisfying its performance obligations to its customers. Amounts billed or invoiced are included in prepaid expenses and other current assets on the consolidated balance sheets. 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 will update its estimates and record any necessary 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 its customers that purchase ZULRESSO directly from the Company limited product return rights for damaged, defective or expiring product, provided it is within a specified period around the product expiration date as set forth in the applicable individual distribution agreement. 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. Based on the distribution model for ZULRESSO, contractual inventory limits with its customers, the product price and limited contractual return rights, the Company believes there will be minimal ZULRESSO returns. The Company has experienced no product returns to date. The Company will update its estimated refund liability, on at least a quarterly basis, based on actual shipments of ZULRESSO subject to contractual return rights, changes in expectations about the amount of estimated refunds or actual returns.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2016-02, Leases Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842 Codification Improvements to Topic 842, Leases Leases (Topic 842): Targeted Improvements Narrow-Scope Improvement for Lessors Leases (Topic 842): Codification Improvements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, and subsequently issued amendments, which introduces a new methodology for accounting for credit losses on financial instruments, including available-for-sale debt securities. The guidance establishes a new "expected loss model" that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Any expected credit losses are to be reflected as allowances rather than reductions in the amortized cost of available-for-sale debt securities. Early adoption is permitted for annual periods beginning after December 15, 2018, and interim periods therein. The Company adopted the standard on the required effective date of January 1, 2019. This guidance did not have a significant impact on the Company’s consolidated financial statements and related disclosures . In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash The Company adopted this standard during the first quarter of 2018. Restricted cash is now included as a component of cash, cash equivalents, and restricted cash on the Company’s consolidated statements of cash flows. Restricted cash balances are classified as non-current unless, under the terms of the applicable agreements, the funds will be released from restrictions within one year from the balance sheet date. The inclusion of restricted cash increased the beginning balances of the consolidated statements of cash flows by $2.4 million, $0.8 million and $0.6 million, respectively, and the ending balances by $2.4 million, $2.4 million and $0.8 million, respectively, for the years ended December 31, 2019, 2018 and 2017. In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718) – Improvements to Nonemployee Share-Based Payment Accounting The Company adopted the standard on the required effective date of January 1, 2019. 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 The Company adopted the standard on the required effective date of January 1, 2020. This guidance is not expected to 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 (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Summary of Company's Money Market Funds and Marketable Securities	The following tables summarize the Company’s money market funds and marketable securities as of December 31, 2019 and 2018 : December 31, 2019 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 $ 126,705 $ 65,414 $ 61,291 $ — Total cash equivalents 126,705 65,414 61,291 — Marketable securities: U.S. government securities 205,328 — 205,328 — U.S. corporate bonds 429,845 — 429,845 — International corporate bonds 142,998 — 142,998 — U.S. commercial paper 52,261 — 52,261 — International commercial paper 51,256 — 51,256 — Total marketable securities 881,688 — 881,688 — $ 1,008,393 $ 65,414 $ 942,979 $ — December 31, 2018 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 $ 190,943 $ 190,943 $ — $ — Total cash equivalents 190,943 190,943 — — Marketable securities: U.S. government securities 220,482 — 220,482 — U.S. corporate bonds 258,566 — 258,566 — International corporate bonds 78,468 — 78,468 — U.S. commercial paper 77,611 — 77,611 — International commercial paper 96,706 — 96,706 — Total marketable securities 731,833 — 731,833 — $ 922,776 $ 190,943 $ 731,833 $ —
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, 2019 and 2018: December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in thousands) Assets: U.S. government securities $ 205,172 $ 176 $ (20 ) $ 205,328 U.S. corporate bonds 429,148 797 (100 ) 429,845 International corporate bonds 142,568 457 (27 ) 142,998 U.S. commercial paper 52,252 14 (5 ) 52,261 International commercial paper 51,253 5 (2 ) 51,256 $ 880,393 $ 1,449 $ (154 ) $ 881,688 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in thousands) Assets: U.S. government securities $ 220,531 $ 8 $ (57 ) $ 220,482 U.S. corporate bonds 258,876 6 (316 ) 258,566 International corporate bonds 78,600 — (132 ) 78,468 U.S. commercial paper 77,630 8 (27 ) 77,611 International commercial paper 96,711 8 (13 ) 96,706 $ 732,348 $ 30 $ (545 ) $ 731,833

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net consists of the following: December 31, 2019 2018 (in thousands) Computer hardware and software $ 2,830 $ 2,148 Furniture and equipment 1,828 1,002 Leasehold improvements 8,967 4,709 13,625 7,859 Less: Accumulated depreciation (4,499 ) (2,216 ) $ 9,126 $ 5,643
Summary of Accrued Expenses	Accrued expenses consist of the following: December 31, 2019 2018 (in thousands) Accrued research and development costs $ 46,940 $ 21,216 Employee-related expenses 22,011 19,638 Professional services 16,720 10,903 Other 947 237 $ 86,618 $ 51,994

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of Consolidated Balance Sheets of Operating Leases	The following table summarizes the presentation of operating leases in the Company’s consolidated balance sheet: (In thousands) Balance sheet location As of December 31, 2019 Assets Right-of-use operating asset Right-of-use operating asset $ 33,771 Liabilities Current operating lease liabilities Operating lease liabilities, current portion 10,244 Long-term operating lease liabilities Operating lease liability, net of current portion 26,848 Total operating lease liabilities $ 37,092
Schedule of Lease Costs Recorded in Consolidated Statements of Operations and Comprehensive Loss	The following table summarizes the lease costs recorded in the Company’s consolidated statements of operations and comprehensive loss: Year Ended (In thousands) December 31, 2019 Operating lease cost $ 9,804 Variable lease cost 2,675 Short-term lease cost 438 $ 12,917
Schedule of Minimum Lease Payments	The minimum lease payments are expected to be as follows: Years Ending December 31, (In thousands) 2020 $ 10,244 2021 9,972 2022 8,898 2023 9,105 2024 5,560 Thereafter - Total lease payments 43,779 Less imputed interest (6,687 ) Present value of operating lease liabilities $ 37,092
Schedule of Future Minimum Lease Payments, Under Non-Cancelable Operating Leases	Under the prior lease guidance, future minimum lease payments under non-cancelable operating leases are as follows at December 31, 2018: Years Ending December 31, (In thousands) 2019 $ 7,918 2020 8,299 2021 8,463 2022 8,692 2023 8,894 Thereafter 5,415 $ 47,681
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 Company’s operating leases are as follows: As of December 31, 2019 Weighted average remaining lease term in years 4.39 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 Company’s operating leases included in cash flows used by operating activities in the consolidated statements of cash flows is as follows: Year Ended (In thousands) December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities $ 9,946 Right-of-use assets obtained in exchange for lease obligations: Operating leases $ 872

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Activity Relating to Restricted Stock Units	The table below summarizes activity relating to restricted stock units: Shares Outstanding as of December 31, 2018 82,700 Granted 393,539 Vested (82,128 ) Forfeited (60,868 ) Outstanding as of December 31, 2019 333,243
Summary of Stock-Based Compensation Expense Recognized	Stock-based compensation expense recognized during the years ended December 31, 2019, 2018 and 2017 was as follows: 2019 2018 2017 (in thousands) Research and development $ 62,931 $ 50,871 $ 19,893 Selling, general and administrative 90,300 51,092 15,641 $ 153,231 $ 101,963 $ 35,534
Summary of Stock-Based Compensation Expense by Award Type Recognized	Stock-based compensation expense by award type recognized during the years ended December 31, 2019, 2018 and 2017 was as follows: 2019 2018 2017 (in thousands) Stock options $ 140,517 $ 100,342 $ 34,525 Restricted stock units 10,992 651 617 Employee stock purchase plan 1,722 970 392 $ 153,231 $ 101,963 $ 35,534
Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted	The fair value of each 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, 2019 2018 2017 Expected dividend yield 0 % 0 % 0 % Expected volatility 71.34 % 74.45 % 79.89 % Risk-free interest rate 2.21 % 2.68 % 2.03 % Expected life of option 6.05 years 6.04 years 6.03 years
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, 2018 7,530,767 $ 93.22 8.03 $ 227,447 Granted 2,215,606 129.15 Exercised (1,031,989 ) 42.72 Forfeited (551,271 ) 138.35 Outstanding as of December 31, 2019 8,163,113 $ 106.30 7.75 $ 87,972 Vested and expected to vest as of December 31, 2019 7,035,349 $ 102.32 7.63 $ 84,442 Exercisable as of December 31, 2019 3,737,468 $ 78.55 6.63 $ 77,652

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Summary of Basic and Diluted Net Loss Per Share	Basic and diluted net loss per share was calculated as follows for the years ended December 31, 2019, 2018 and 2017: Year Ended December 31, 2019 2018 2017 Basic net loss per share: Numerator: Net loss (in thousands) $ (680,238 ) $ (372,882 ) $ (270,120 ) Denominator: Weighted average common stock outstanding —basic 50,833,837 46,121,194 38,113,678 Dilutive effect of shares of common stock equivalents resulting from common stock options and restricted stock units — — — Weighted average common stock outstanding —diluted 50,833,837 46,121,194 38,113,678 Net loss per share—basic and diluted $ (13.38 ) $ (8.08 ) $ (7.09 )
Summary of Anti-Dilutive Common Stock Equivalents Outstanding	The following common stock equivalents outstanding as of December 31, 2019, 2018 and 2017 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, 2019 2018 2017 Stock options 7,677,518 6,758,420 4,915,956 Restricted stock units — 13,500 29,100 Employee stock purchase plan 33,429 16,398 11,683 7,710,947 6,788,318 4,956,739

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
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, 2019 2018 2017 Tax due at statutory rate 21.0 % 21.0 % 34.0 % State taxes, net of federal 2.8 6.0 5.1 Stock-based compensation 1.4 2.5 6.4 Foreign rate differential (1.6 ) (4.3 ) (3.2 ) Federal and state credits 2.4 2.5 7.2 Change in valuation allowance (25.8 ) (27.6 ) (22.5 ) Other 0.5 (0.1 ) — Federal and state rate change (0.7 ) — (24.6 ) Research and orphan drug credit addback — — (2.4 ) 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 asset at December 31, 2019 and 2018 are as follows: December 31, 2019 2018 (in thousands) Net operating losses $ 348,848 $ 206,460 Capitalized start-up costs 982 1,242 Tax credit carryforwards 80,088 63,653 Accrued expenses 4,055 4,498 Depreciation and amortization 2,002 1,001 Stock options 46,750 30,925 Right of use asset (8,059 ) — Right of use liability 8,852 — Other (246 ) 568 Total net deferred tax asset before valuation allowance 483,272 308,347 Valuation allowance (483,272 ) (308,347 ) Net deferred tax asset $ — $ —

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Information	The following table contains quarterly financial information for 2019 and 2018. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period. 2019 First Quarter Second Quarter Third Quarter Fourth Quarter Total (in thousands, except per share amounts) Total revenue $ 465 $ 873 $ 3,570 $ 1,960 $ 6,868 Total operating costs and expenses 170,317 177,330 190,747 176,598 714,992 Loss from operations (169,852 ) (176,457 ) (187,177 ) (174,638 ) (708,124 ) Net loss (163,406 ) (168,221 ) (179,958 ) (168,653 ) (680,238 ) Net loss per share—basic and diluted $ (3.37 ) $ (3.28 ) $ (3.48 ) $ (3.25 ) $ (13.38 ) 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total (in thousands, except per share amounts) Total revenue $ — $ 90,000 $ — $ 273 $ 90,273 Total operating expenses 78,119 112,147 128,745 164,500 483,511 Loss from operations (78,119 ) (22,147 ) (128,745 ) (164,227 ) (393,238 ) Net loss (74,598 ) (16,978 ) (122,918 ) (158,388 ) (372,882 ) Net loss per share—basic and diluted $ (1.68 ) $ (0.36 ) $ (2.63 ) $ (3.38 ) (8.08 )

Nature of the Business - Additi

Nature of the Business - Additional Information (Detail) - USD ($) $ in Thousands	116 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Nature Of Business [Line Items]
Accumulated deficit	$ (1,643,567)	$ (963,329)
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	$ 2,200

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail)	Feb. 28, 2019ft²	Feb. 27, 2019USD ($)$ / sharesshares	Sep. 30, 2018ft²	Feb. 13, 2018USD ($)$ / sharesshares	Jan. 01, 2018ft²	Nov. 17, 2017USD ($)$ / sharesshares	Sep. 14, 2016USD ($)$ / sharesshares	Jan. 12, 2016USD ($)$ / sharesshares	Apr. 20, 2015USD ($)$ / sharesshares	Jul. 23, 2014USD ($)$ / sharesshares	Mar. 31, 2019ft²	Dec. 31, 2018USD ($)ft²	Oct. 31, 2018ft²	May 31, 2018ft²	Apr. 30, 2018ft²	Mar. 31, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)ft²	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jan. 01, 2019USD ($)
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit												$ 2,367,000					$ 2,367,000	$ 2,367,000
Lease expire date																	Jan. 31, 2022
Intangible assets												0						0
Issuance of common stock, shares | shares		3,833,334		4,032,012		4,058,822	5,062,892	3,157,894	2,628,571
Common stock price per share | $ / shares		$ 150		$ 164		$ 85	$ 39.75	$ 47.50	$ 52.50
Proceeds from public offering of common stock, net of commissions and underwriting discounts and estimated offering costs		$ 560,900,000		$ 631,200,000		$ 325,800,000	$ 189,200,000	$ 140,400,000	$ 129,100,000
Lease liabilities																	$ 37,092,000
ASC Topic 842 [Member]
Summary Of Significant Accounting Policies [Line Items]
Lease liabilities																	37,092,000				$ 44,200,000
Right-of-use assets																					$ 41,100,000
Accounting Standards Update 2016-18 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents increased by amount due to inclusion of restricted cash																	2,400,000	2,400,000	$ 800,000	$ 600,000
Initial Public Offering [Member]
Summary Of Significant Accounting Policies [Line Items]
Issuance of common stock, shares | shares										5,750,000
Common stock price per share | $ / shares										$ 18
Proceeds from initial public offering of common stock, net of commissions and underwriting discounts										$ 94,000,000
CyDex License Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Milestone payments																$ 3,000,000
The Regents of University of California [Member]
Summary Of Significant Accounting Policies [Line Items]
Milestone payments																$ 500,000
Operating Lease Two [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit												39,000					39,000	39,000
Additional Office space rented under operating lease | ft²					19,805										40,419
Lease expire date					Feb. 28, 2022										Aug. 31, 2024
Operating Lease Three [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit												300,000					300,000	300,000
Additional Office space rented under operating lease | ft²														15,525
Lease expire date														Nov. 30, 2024
Operating Lease One [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit												500,000					500,000	500,000
Additional Office space rented under operating lease | ft²	58,442		54,943		54,943						63,017		58,442
Lease expire date					Aug. 15, 2024						Aug. 31, 2024		Aug. 31, 2024
Operating Lease Six [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit												400,000						400,000
Operating Lease Four [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit												400,000					400,000	$ 400,000
Additional Office space rented under operating lease | ft²																		15,975
Lease expire date																		Feb. 29, 2024
Operating Lease Five [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit												$ 700,000					$ 700,000	$ 700,000
Additional Office space rented under operating lease | ft²												15,975
Lease expire date												Feb. 29, 2024

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Company's Money Market Funds and Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	$ 126,705	$ 190,943
Total marketable securities	881,688	731,833
Total cash equivalents and marketable securities	1,008,393	922,776
Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	126,705	190,943
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	65,414	190,943
Total cash equivalents and marketable securities	65,414	190,943
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	65,414	190,943
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	61,291
Total marketable securities	881,688	731,833
Total cash equivalents and marketable securities	942,979	731,833
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	61,291
U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	205,328	220,482
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	205,328	220,482
U.S. Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	429,845	258,566
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	429,845	258,566
International Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	142,998	78,468
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	142,998	78,468
U.S. Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	52,261	77,611
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	52,261	77,611
International Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	51,256	96,706
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	$ 51,256	$ 96,706

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument Fair Value Carrying Value [Line Items]
Transfers among the Level 1, Level 2 and Level 3 categories	$ 0	$ 0
Marketable securities fair value held to maturity	137,100,000	5,900,000
Impairment of assets	$ 0	$ 0
Maximum [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
Minimum [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities held, matuirity period	1 year

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Gross Unrealized Gains and Losses of Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 880,393	$ 732,348
Gross Unrealized Gains	1,449	30
Gross Unrealized Losses	(154)	(545)
Fair Value	881,688	731,833
U.S. Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	205,172	220,531
Gross Unrealized Gains	176	8
Gross Unrealized Losses	(20)	(57)
Fair Value	205,328	220,482
U.S. Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	429,148	258,876
Gross Unrealized Gains	797	6
Gross Unrealized Losses	(100)	(316)
Fair Value	429,845	258,566
International Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	142,568	78,600
Gross Unrealized Gains	457
Gross Unrealized Losses	(27)	(132)
Fair Value	142,998	78,468
U.S. Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	52,252	77,630
Gross Unrealized Gains	14	8
Gross Unrealized Losses	(5)	(27)
Fair Value	52,261	77,611
International Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	51,253	96,711
Gross Unrealized Gains	5	8
Gross Unrealized Losses	(2)	(13)
Fair Value	$ 51,256	$ 96,706

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 13,625	$ 7,859
Less: Accumulated depreciation	(4,499)	(2,216)
Property and equipment, net	9,126	5,643
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,830	2,148
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,828	1,002
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,967	$ 4,709

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 2,283	$ 1,143	$ 531
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 - Su_2

Balance Sheet Components - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued research and development costs	$ 46,940	$ 21,216
Employee-related expenses	22,011	19,638
Professional services	16,720	10,903
Other	947	237
Total accrued expenses	$ 86,618	$ 51,994

Commitments and Contingencies -

Commitments and Contingencies - Operating Leases - Additional Information (Detail) $ in Thousands

Feb. 28, 2019ft²

Oct. 02, 2018ft²

Sep. 30, 2018ft²

Aug. 01, 2018ft²

Jan. 01, 2018ft²

Mar. 31, 2019ft²

Dec. 31, 2018ft²

Oct. 31, 2018ft²

May 31, 2018ft²

Apr. 30, 2018ft²

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Dec. 31, 2017USD ($)

Jan. 01, 2019USD ($)

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 | $

$ 33,771

$ 5,300

Lessee, operating lease contract term

3 years

Rent expense | $

$ 10,200

$ 6,500

$ 3,700

Operating Lease One [Member]

Commitments And Contingencies [Line Items]

Office space rent under operating lease

58,442

54,943

54,943

63,017

58,442

Lease expire date

Aug. 15, 2024

Aug. 31, 2024

Aug. 31, 2024

Increased office space rent

4,575

3,499

Operating Lease Two [Member]

Commitments And Contingencies [Line Items]

Office space rent under operating lease

19,805

40,419

Lease expire date

Feb. 28, 2022

Aug. 31, 2024

Increased office space rent

7,133

13,481

20,614

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

6 years

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Consolidated Balance Sheets of Operating Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Assets
Right-of-use operating asset	$ 33,771	$ 5,300
Liabilities
Current operating lease liabilities	10,244
Long-term operating lease liabilities	26,848
Total operating lease liabilities	$ 37,092

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Lease Costs Recorded in Consolidated Statements of Operations and Comprehensive Loss (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating lease cost	$ 9,804
Variable lease cost	2,675
Short-term lease cost	438
Total	$ 12,917

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Minimum Lease Payments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Lessee Lease Description [Line Items]
Present value of operating lease liabilities	$ 37,092
ASU Topic (842) [Member]
Lessee Lease Description [Line Items]
2020	10,244
2021	9,972
2022	8,898
2023	9,105
2024	5,560
Total lease payments	43,779
Less imputed interest	(6,687)
Present value of operating lease liabilities	$ 37,092	$ 44,200

Commitments and Contingencies_5

Commitments and Contingencies - Schedule of Future Minimum Lease Payments, Under Non-Cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019	$ 7,918
2020	8,299
2021	8,463
2022	8,692
2023	8,894
Thereafter	5,415
Total Operating leases, future minimum payments	$ 47,681

Commitments and Contingencies_6

Commitments and Contingencies - Schedule of Weighted Average Remaining Lease Term and Weighted Average Discount Rate of Our Operating Leases (Detail)	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Weighted average remaining lease term in years	4 years 4 months 20 days
Weighted average discount rate	7.50%

Commitments and Contingencies_7

Commitments and Contingencies - Schedule of Supplemental Disclosure of Cash Flow Information Related To Operating Leases (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 9,946
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 872

Commitments and Contingencies_8

Commitments and Contingencies - CyDex License Agreement - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commitments And Contingencies [Line Items]
Research and development expense		$ 368,815,000	$ 282,107,000	$ 210,277,000
CyDex License Agreement [Member]
Commitments And Contingencies [Line Items]
Research and development expense		1,000,000
Milestone payments	$ 3,000,000
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] | Brexanolone [Member]
Commitments And Contingencies [Line Items]
Research and development expense related to milestone expense				0
Milestone payments		0		$ 0
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] | Brexanolone [Member]
Commitments And Contingencies [Line Items]
Research and development expense related to milestone expense			800,000
Milestone payments			$ 800,000
Intangible asset related to milestone		3,000,000
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		2,300,000
Milestone payments		2,300,000
Intangible asset related to milestone		3,000,000
Milestone payments related to intangible assets		$ 3,000,000

Commitments and Contingencies_9

Commitments and Contingencies - University of California License Agreements - Additional Information (Detail) - University of California License Agreements [Member] - USD ($)	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Commitments And Contingencies [Line Items]
Upfront payment		$ 50,000
Annual license maintenance fee						$ 15,000
Research and development expense related to milestone expense			$ 500,000	$ 200,000	$ 0
Milestone payments			500,000	$ 200,000	$ 0
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
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
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

Commitments and Contingencie_10

Commitments and Contingencies - Washington University License Agreement - Additional Information (Detail) - Washington University License Agreement [Member] - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2013	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2013
Commitments And Contingencies [Line Items]
Upfront non-refundable payment	$ 50,000
Annual license maintenance fee					$ 15,000
Issuance of common stock, shares					47,619
Research and development expense related to issue of common stock obligation					$ 100,000
Research and development expense related to milestone expense		$ 0	$ 0	$ 0
Milestone payments		0	$ 0	$ 0
Clinical Development [Member]
Commitments And Contingencies [Line Items]
Research and development expense related to milestone expense		50,000
Milestone payments		$ 50,000
Maximum [Member] | Clinical Development [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	700,000
Maximum [Member] | Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	$ 500,000

Commitments and Contingencie_11

Commitments and Contingencies - Consulting Agreement - Additional Information (Detail) - Consulting Agreement [Member] - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2014	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commitments And Contingencies [Line Items]
Research and development expense related to milestone expense		$ 0	$ 0	$ 0
Milestone payments		0	$ 0	$ 0
Clinical Development and Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Shares of common stock for attaining milestones	126,984
Research and development expense related to milestone expense		1,800,000
Milestone payments		500,000
Payments for stock issued upon reaching a milestone		$ 1,300,000
Milestone based share compensation, shares issued		39,681
Clinical Development and Regulatory Milestones [Member] | Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	$ 2,000,000

Collaboration Agreement - Addit

Collaboration Agreement - Additional Information (Detail) - USD ($)	Jun. 12, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue		$ 1,960,000	$ 3,570,000	$ 873,000	$ 465,000	$ 273,000	$ 90,000,000	$ 6,868,000	$ 90,273,000
Shionogi Collaboration Agreement [Member] | SAGE-217 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement effective date	Jun. 12, 2018
Upfront payment	$ 90,000,000
Average percentage on tiered royalties	20.00%
Standalone selling price of license performance obligation		$ 90,000,000						90,000,000
Revenue								$ 90,000,000
Shionogi Collaboration Agreement [Member] | SAGE-217 [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone payment receivable	$ 485,000,000
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
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
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

Preferred Stock - Additional In

Preferred Stock - Additional Information (Detail) - shares	Dec. 31, 2019	Dec. 31, 2018
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 Infor

Common Stock - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
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.
Purchase of treasury stock, Shares	3,033
Total cost of shares held in treasury	$ 400,000	$ 211,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)	Jan. 01, 2019shares	Dec. 31, 2019USD ($)Milestone$ / sharesshares	Dec. 31, 2018USD ($)Milestone$ / sharesshares	Dec. 31, 2017USD ($)Milestone$ / sharesshares	Dec. 31, 2016USD ($)	Dec. 31, 2015	Sep. 20, 2018shares	Jul. 02, 2014shares
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
Stock-based compensation expense | $		$ 153,231,000	$ 101,963,000	$ 35,534,000
Weighted average grant date fair value per share | $ / shares		$ 82.39	$ 109.92	$ 41.94
Share option, weighted-average forfeiture rates		13.70%	10.70%	13.30%
Total number of shares reserved		10,651,531
Common stock available for issuance under stock option plan		2,155,175
Non-employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, term of plan			10 years
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	1,875,530
Milestones achieved | Milestone		1	1	0
2014 Plan [Member] | Milestone Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of performance based grants that were achieved			33.00%		50.00%	35.00%
2014 Plan [Member] | Milestone Two [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] | Consultant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $					$ 0
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
Shares of common stock initially authorized for issuance under this plan							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
Shares of common stock initially authorized for issuance under this plan								282,000
Number of shares issued under the plan		105,160
Accrued expenses | $		$ 700,000
Total number of shares available for issuance		176,840
Restricted Stock Units Vest One Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units cliff vesting percentage		25.00%
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted		393,539		32,500
Share based compensation granted under plan vested period				2 years
Fair value of restricted stock units vested | $		$ 2,000,000	$ 2,600,000	$ 0
Restricted stock units granted		60,868
Outstanding and unvested performance restricted stock units		333,243	82,700
Stock-based compensation expense | $		$ 10,992,000	$ 651,000	$ 617,000
Restricted Stock Units [Member] | Restricted Stock Units Vest One Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units cliff vesting percentage				50.00%
Restricted stock units vesting period month and year				2018-02
Restricted Stock Units [Member] | Restricted Stock Units Vest Two Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units cliff vesting percentage				50.00%
Restricted stock units vesting period month and year				2019-02
Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted			71,400
Fair value of restricted stock units vested | $		$ 11,100,000	$ 0
Percentage Of Milestone Achieved		18.00%
Outstanding and unvested performance restricted stock units		333,243
Total unrecognized stock-based compensation expense | $		$ 52,600,000
Performance Restricted Stock Units [Member] | Milestones [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted			33,600
Performance Restricted Stock Units [Member] | Commercial Milestones [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted		393,539	37,800
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense | $		$ 35,700,000
Options granted		0	524,003	449,208
Number of shares outstanding and unvested stock options		485,595
Performance-Based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $		$ 0	$ 0	$ 0
Performance-Based Stock Options [Member] | Consultant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $			6,900,000
Performance Milestone [Member] | 2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $		16,300,000	4,400,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense | $		$ 283,400,000
Options granted		2,215,606
Stock-based compensation expense | $		$ 140,517,000	100,342,000	34,525,000
Weighted average period of unrecognized compensation costs		2 years 5 months 8 days
Intrinsic value of options exercised | $		$ 119,100,000	$ 98,300,000	$ 77,700,000
Total number of shares reserved		8,163,113	7,530,767

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Activity Relating to Restricted Stock Units (Detail) - Restricted Stock Units [Member] - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Shares at beginning balance	82,700
Granted, Shares	393,539	32,500
Vested, Shares	(82,128)
Forfeited, Shares	(60,868)
Outstanding, Shares at ending balance	333,243

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock-Based Compensation Expense Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 153,231	$ 101,963	$ 35,534
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	62,931	50,871	19,893
Selling, General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 90,300	$ 51,092	$ 15,641

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock-Based Compensation Expense by Award Type Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 153,231	$ 101,963	$ 35,534
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	140,517	100,342	34,525
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	10,992	651	617
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 1,722	$ 970	$ 392

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility	71.34%	74.45%	79.89%
Risk-free interest rate	2.21%	2.68%	2.03%
Expected life of option	6 years 18 days	6 years 14 days	6 years 10 days

Stock-Based Compensation - Su_5

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, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance, Outstanding Shares	10,651,531
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Outstanding Shares	7,530,767
Granted, Shares	2,215,606
Exercised, Shares	(1,031,989)
Forfeited, Shares	(551,271)
Ending balance, Outstanding Shares	8,163,113	7,530,767
Vested and expected to vest, Shares	7,035,349
Exercisable, Shares	3,737,468
Beginning balance, Outstanding Weighted Average Exercise Price	$ 93.22
Granted, Weighted Average Exercise Price	129.15
Exercised, Weighted Average Exercise Price	42.72
Forfeited, Weighted Average Exercise Price	138.35
Ending balance, Outstanding Weighted Average Exercise Price	106.30	$ 93.22
Vested and expected to vest, Weighted Average Exercise Price	102.32
Exercisable, Weighted Average Exercise Price	$ 78.55
Outstanding, Weighted Average Remaining Life	7 years 9 months	8 years 10 days
Vested and expected to vest, Weighted Average Remaining Life	7 years 7 months 17 days
Exercisable, Weighted Average Remaining Life	6 years 7 months 17 days
Outstanding, Aggregate Intrinsic Value	$ 87,972	$ 227,447
Vested and expected to vest, Aggregate Intrinsic Value	84,442
Exercisable, Aggregate Intrinsic Value	$ 77,652

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss	$ (168,653)	$ (179,958)	$ (168,221)	$ (163,406)	$ (158,388)	$ (122,918)	$ (16,978)	$ (74,598)	$ (680,238)	$ (372,882)	$ (270,120)
Denominator:
Weighted average common stock outstanding —basic									50,833,837	46,121,194	38,113,678
Dilutive effect of shares of common stock equivalents resulting from common stock options and restricted stock units									0	0	0
Weighted average common stock outstanding —diluted									50,833,837	46,121,194	38,113,678
Net loss per share—basic and diluted	$ (3.25)	$ (3.48)	$ (3.28)	$ (3.37)	$ (3.38)	$ (2.63)	$ (0.36)	$ (1.68)	$ (13.38)	$ (8.08)	$ (7.09)

Net Loss Per Share - Summary _2

Net Loss Per Share - Summary of Anti-Dilutive Common Stock Equivalents Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	7,710,947	6,788,318	4,956,739
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	7,677,518	6,758,420	4,915,956
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents		13,500	29,100
Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	33,429	16,398	11,683

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Current tax expense	$ 0
Deferred tax expense	0
Federal operating loss carryforwards	1,400,000,000
State operating loss carryforwards	$ 1,000,000,000
Federal net operating loss carryforwards expiration year	2031
State net operating loss carryforwards expiration year	2030
Federal orphan drug tax credit carry forwards	$ 40,000,000
Tax credit carry forwards expiration period	2034
U.S. corporate tax rate	21.00%	21.00%	34.00%
Reduction to deferred tax asset			$ 66,400,000
Change in amount of deferred tax assets	$ 174,900,000
Valuation allowance	483,272,000	$ 308,347,000
Unrecognized tax benefits	0	0	$ 0
Accrued interest or penalties related to uncertain tax positions	0	$ 0
Uncertain tax positions	0
Domestic Tax Authority [Member]
Income Tax Disclosure [Line Items]
Research and development tax credits carryforwards	$ 34,200,000
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	$ 7,400,000
Research and development tax credits carryforwards expiration year	2027

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of U.S. Statutory Rate to Company's Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax due at statutory rate	21.00%	21.00%	34.00%
State taxes, net of federal	2.80%	6.00%	5.10%
Stock-based compensation	1.40%	2.50%	6.40%
Foreign rate differential	(1.60%)	(4.30%)	(3.20%)
Federal and state credits	2.40%	2.50%	7.20%
Change in valuation allowance	(25.80%)	(27.60%)	(22.50%)
Other	0.50%	(0.10%)
Federal and state rate change	(0.70%)		(24.60%)
Research and orphan drug credit addback			(2.40%)
Total effective tax rate	0.00%	0.00%	0.00%

Income Taxes - Summary of Signi

Income Taxes - Summary of Significant Components of Company's Net Deferred Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Net operating losses	$ 348,848	$ 206,460
Capitalized start-up costs	982	1,242
Tax credit carryforwards	80,088	63,653
Accrued expenses	4,055	4,498
Depreciation and amortization	2,002	1,001
Stock options	46,750	30,925
Right of use asset	(8,059)
Right of use liability	8,852
Other	(246)	568
Total net deferred tax asset before valuation allowance	483,272	308,347
Valuation allowance	$ (483,272)	$ (308,347)

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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	$ 3.6	$ 1.8	$ 0.9
Defined Contribution Plan, Sponsor Location [Extensible List]	country:US	country:US	country:US
Defined Contribution Plan, Tax Status [Extensible List]	us-gaap:QualifiedPlanMember	us-gaap:QualifiedPlanMember	us-gaap:QualifiedPlanMember

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 1,960	$ 3,570	$ 873	$ 465	$ 273		$ 90,000		$ 6,868	$ 90,273
Total operating costs and expenses	176,598	190,747	177,330	170,317	164,500	$ 128,745	112,147	$ 78,119	714,992	483,511	$ 273,155
Loss from operations	(174,638)	(187,177)	(176,457)	(169,852)	(164,227)	(128,745)	(22,147)	(78,119)	(708,124)	(393,238)	(273,155)
Net loss	$ (168,653)	$ (179,958)	$ (168,221)	$ (163,406)	$ (158,388)	$ (122,918)	$ (16,978)	$ (74,598)	$ (680,238)	$ (372,882)	$ (270,120)
Net loss per share—basic and diluted	$ (3.25)	$ (3.48)	$ (3.28)	$ (3.37)	$ (3.38)	$ (2.63)	$ (0.36)	$ (1.68)	$ (13.38)	$ (8.08)	$ (7.09)