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Document and Entity Information	12 Months Ended
Dec. 31, 2014
Document And Entity Information [Abstract]
Document Type	S-1
Amendment Flag	false
Document Period End Date	Dec. 31, 2014
Trading Symbol	SAGE
Entity Registrant Name	Sage Therapeutics, Inc.
Entity Central Index Key	0001597553
Entity Filer Category	Non-accelerated Filer

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 127,766	$ 8,066
Prepaid expenses and other current assets	1,056	341
Total current assets	128,822	8,407
Property and equipment, net	163	86
Restricted cash	39	39
Deferred tax assets	641
Total assets	129,665	8,532
Current liabilities:
Accounts payable	2,429	1,988
Accrued expenses	4,687	327
Deferred tax liabilities	641
Total current liabilities	7,757	2,315
Other liabilities	23	44
Total liabilities	7,780	2,359
Commitments and contingencies (Note 4)
Redeemable convertible preferred stock (Series A, B and C), $0.0001 par value; no shares and 37,750,000 shares authorized at December 31, 2014 and 2013, respectively; no shares and 37,750,000 shares issued and outstanding at December 31, 2014 and 2013, respectively; liquidation preference of $0 and $40,663 at December 31, 2014 and 2013, respectively		37,709
Stockholders' equity (deficit):
Preferred stock, $0.0001 par value; 5,000,000 and no shares authorized at December 31, 2014 and 2013, respectively; no shares issued or outstanding at December 31, 2014 and 2013, respectively
Common stock, $0.0001 par value; 120,000,000 and 66,000,000 shares authorized at December 31, 2014 and 2013, respectively; 25,621,791 and 1,622,761 shares issued and outstanding at December 31, 2014 and 2013, respectively	3
Additional paid-in capital	188,727	139
Accumulated deficit	(66,845)	(31,675)
Total stockholders' equity (deficit)	121,885	(31,536)
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	$ 129,665	$ 8,532

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Redeemable convertible preferred stock, par value	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	0	37,750,000
Redeemable convertible preferred stock, shares issued	0	37,750,000
Redeemable convertible preferred stock, shares outstanding	0	37,750,000
Redeemable convertible preferred stock, liquidation preference	$ 0	$ 40,663
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	0
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	66,000,000
Common stock, shares issued	25,621,791	1,622,761
Common stock, shares outstanding	25,621,791	1,622,761

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating expenses:
Research and development	$ 24,100	$ 14,357	$ 7,229
General and administrative	9,710	3,922	2,402
Total operating expenses	33,810	18,279	9,631
Loss from operations	(33,810)	(18,279)	(9,631)
Interest income (expense), net	8	1
Other income (expense), net	(9)	(3)	(1)
Net loss and comprehensive loss	(33,811)	(18,281)	(9,632)
Accretion of redeemable convertible preferred stock to redemption value	(2,294)	(7)	(4)
Net loss attributable to common stockholders	$ (36,105)	$ (18,288)	$ (9,636)
Net loss per share attributable to common stockholders-basic and diluted	$ (1.67)	$ (12.26)	$ (8.62)
Weighted average number of common shares used in net loss per share attributable to common stockholders-basic and diluted	21,574,347	1,492,288	1,118,288

Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Initial Public Offering [Member]	Series A Preferred Stock [Member]	Series A, B and C Redeemable Convertible Preferred Stock[Member]	Series A, B and C Redeemable Convertible Preferred Stock[Member] Series A Preferred Stock [Member]	Series A, B and C Redeemable Convertible Preferred Stock[Member] Series B Preferred Stock [Member]	Series A, B and C Redeemable Convertible Preferred Stock[Member] Series C Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Initial Public Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Initial Public Offering [Member]	Additional Paid-in Capital [Member] Series A Preferred Stock [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Series A Preferred Stock [Member]
Balances at Dec. 31, 2011	$ (3,761)			$ 5,972									$ (3,761)
Shares issued during period, Amount					$ 8,994
Balances, Shares at Dec. 31, 2011				6,000,000				680,560
Shares issued during period, Shares					9,000,000
Accretion of Series A Preferred Stock issuance costs			$ (4)		$ 4							$ (3)		$ (1)
Issuance of common stock from exercise of stock options, Shares								5,555
Vesting of restricted stock, Amount	3									$ 3
Vesting of restricted stock, Shares								709,158
Net loss	(9,632)												(9,632)
Balances at Dec. 31, 2012	(13,394)			$ 14,970									(13,394)
Balances, Shares at Dec. 31, 2012				15,000,000				1,395,273
Shares issued during period, Amount					$ 22,732
Shares issued during period, Shares					22,750,000
Issuance of common stock from exercise of stock options, Amount	1									1
Accretion of Series A Preferred Stock issuance costs			$ (7)		$ 7							$ (7)
Issuance of common stock from exercise of stock options, Shares								3,174
Vesting of restricted stock, Amount	20									20
Vesting of restricted stock, Shares								176,695
Issuance of common stock in payment of licensing and consultant fees, Amount	64									64
Issuance of common stock in payment of licensing and consultant fees, Shares								47,619
Stock-based compensation expense	61									61
Net loss	(18,281)												(18,281)
Balances at Dec. 31, 2013	(31,536)			$ 37,709						139			(31,675)
Balances, Shares at Dec. 31, 2013				37,750,000				1,622,761
Shares issued during period, Amount		$ 93,970				$ 14,970	$ 37,890		$ 1		$ 93,969
Shares issued during period, Shares						9,999,999	8,973,905		5,750,000
Issuance of common stock from exercise of stock options, Amount	40									40
Issuance of common stock from exercise of stock options, Shares								87,475
Vesting of restricted stock, Amount	14									14
Vesting of restricted stock, Shares								138,108
Issuance of common stock in payment of licensing and consultant fees, Amount	127									127
Issuance of common stock in payment of licensing and consultant fees, Shares								15,872
Stock-based compensation expense	2,512									2,512
Accretion of redeemable convertible preferred stock to redemption value	(2,294)			$ 2,294						(935)			(1,359)
Conversion of redeemable convertible preferred stock to common stock, Amount	92,863			$ (92,863)				$ 2		92,861
Conversion of redeemable convertible preferred stock to common stock, Shares				56,723,904				18,007,575
Conversion of redeemable convertible preferred stock to common stock, Shares				(56,723,904)				(18,007,575)
Net loss	(33,811)												(33,811)
Balances at Dec. 31, 2014	$ 121,885							$ 3		$ 188,727			$ (66,845)
Balances, Shares at Dec. 31, 2014								25,621,791

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities
Net loss	$ (33,811)	$ (18,281)	$ (9,632)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,512	61
Licensing or consulting fees paid in common stock	127	64
Depreciation and amortization	51	47	44
Changes in operating assets and liabilities
Prepaid expenses and other current assets	(715)	(317)	71
Accounts payable	441	674	609
Accrued expenses	4,374	236	(18)
Other liabilities	(21)
Net cash used in operating activities	(27,042)	(17,516)	(8,926)
Cash flows from investing activities
Purchase of property and equipment	(128)	(3)	(111)
Net cash used in investing activities	(128)	(3)	(111)
Cash flows from financing activities
Proceeds from the issuance of common stock and restricted stock, net	40	51	3
Proceeds from initial public offering of common stock, net of commissions and underwriting discounts	96,255
Payment of offering costs	(2,285)
Net cash provided by financing activities	146,870	22,783	8,997
Net increase in cash and cash equivalents	119,700	5,264	(40)
Cash and cash equivalents at beginning of period	8,066	2,802	2,842
Cash and cash equivalents at end of period	127,766	8,066	2,802
Supplemental disclosure of non-cash investing and financing activities
Accretion of redeemable convertible preferred stock to redemption value	2,294	7	4
Conversion of redeemable convertible preferred stock to common stock	92,863
Series A Preferred Stock [Member]
Cash flows from financing activities
Proceeds from the issuance of preferred stock, net of issuance costs		$ 22,732	$ 8,994
Series B Preferred Stock [Member]
Cash flows from financing activities
Proceeds from the issuance of preferred stock, net of issuance costs	14,970
Series C Preferred Stock [Member]
Cash flows from financing activities
Proceeds from the issuance of preferred stock, net of issuance costs	$ 37,890

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2014

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 financial statements.

Basis of Presentation

The accompanying consolidated financial statements include those of the Company and its subsidiary, Sage Securities Corporation, 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 financial statements and the reported amounts of 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 three months or less at the date of purchase to be cash equivalents.

Restricted Cash

A deposit of $39 was restricted from withdrawal as of December 31, 2014 and 2013. The restriction is related to securing the Company’s facility lease and expires in 2017 in accordance with the operating lease agreement. This balance is included in restricted cash on the accompanying balance sheets.

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.

Impairment of Long-Lived Assets

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

Research and Development

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.

Research Contract Costs and Accruals

The Company has entered into various research and development contracts with research institutions and other companies both inside and outside of the United States. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. 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 Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

The Company expenses patent costs as incurred and classifies such costs as general and administrative expenses in the accompanying statements of operations and comprehensive loss.

Stock-Based Compensation

The Company recognizes compensation expense for all stock-based awards made to employees and nonemployee directors, including grants of stock options and restricted stock, based on estimated fair value on date of grant, over the requisite service period.

For stock options and restricted stock issued to nonemployee consultants, the Company recognizes the fair value of such instruments as an expense over the period in which the related services are received. The fair value of the awards and measurement of related stock-based compensation is subject to periodic adjustments as the underlying equity instruments vest.

The fair value of each option grant is estimated using the Black-Scholes option-pricing model. Through July 2014, the Company was a private company and lacks sufficient Company-specific historical and implied volatility information. Therefore, the Company estimates expected volatility based on the historical volatility of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its traded stock price. The expected term of the Company’s options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options, while the expected term of its options granted to consultants and nonemployees has been determined based on the contractual term of the options. 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. Expected dividend yield is based on the fact that the Company 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. To the extent actual forfeitures differ from the estimates, the difference will be recorded as a cumulative adjustment in the period the estimates are revised. The Company recognizes compensation expense for only the portion of awards that are expected to vest. Expected forfeitures are based on the Company’s historical experience and management’s expectations of future forfeitures.

Basic and Diluted Net Income (Loss) Per Share

Upon the closing of the Company’s IPO in July 2014, all of the Company’s outstanding redeemable convertible preferred shares were converted into shares of common stock. Prior to this conversion, the Company followed the two-class method when computing net income (loss) per share as the Company had issued shares that meet the definition of participating securities. The two-class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common shareholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. The Company’s redeemable convertible preferred shares contractually entitled the holders of such shares to participate in dividends, but did not contractually require the holders of such shares to participate in losses of the Company. Accordingly, the two-class method did not apply for periods in which the Company reported a net loss or a net loss attributable to common shareholders resulting from dividends or accretion related to its redeemable convertible preferred shares.

Basic net income (loss) per share attributable to common shareholders is computed by dividing the net income (loss) attributable to common shareholders by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per share attributable to common shareholders is computed by dividing the diluted net income (loss) attributable to common shareholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of outstanding stock options and unvested restricted common shares, as determined using the treasury stock method. For periods in which the Company has reported net losses, diluted net loss per common share attributable to common shareholders is the same as basic net loss per common share attributable to common shareholders, since dilutive common shares are not assumed to have been issued if their effect is antidilutive.

The Company reported a net loss attributable to common stockholders for the years ended December 31, 2014, 2013 and 2012.

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 Company’s current and future product candidates will receive the necessary approvals. If the Company is denied approval or approval is delayed, it may have a material adverse impact on the Company’s business and its financial statements.

The Company is subject to risks common to companies in the development stage including, but not limited to, dependency on the clinical and commercial success of its product candidates, ability to obtain regulatory approval of its product candidates, the need for substantial additional financing to achieve its goals, uncertainty of broad adoption of its approved products, if any, by physicians and consumers, significant competition and untested manufacturing capabilities.

Concentration of Credit Risk and of Significant Suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents. The Company has all cash and cash equivalents balances at two 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. In particular, 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.

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 to be classified and disclosed in one of the following three categories:


Level 1	—	Quoted market prices in active markets for identical assets or liabilities. At December 31, 2014 and 2013, the Company’s Level 1 assets consisted of money market funds totaling $127,766 and $8,066, respectively.

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. At December 31, 2014 and 2013, the Company had no Level 2 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. At December 31, 2014 and 2013, the Company had no Level 3 assets or liabilities.

The Company’s financial instruments generally consist of cash equivalents, accounts payable and accrued expenses. The carrying amounts for the applicable financial instruments reported in the balance sheets approximate their fair values at December 31, 2014 and 2013, respectively.

Deferred Offering Costs

The Company capitalizes certain legal, accounting and other third-party fees that are directly associated with in-process equity financings as other assets until such financings are consummated. After consummation of the equity financing in July 2014, $2,285 of these costs were recorded in stockholders’ equity (deficit) as a reduction of additional paid-in capital generated as a result of the initial public offering.

Segment Data

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on advancing medicines to treat central nervous system disorders, where there are inadequate or no approved existing therapies, including status epilepticus. All tangible assets are held within the U.S.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with stockholders. For the years ended December 31, 2014, 2013 and 2012, there was no difference between net loss and comprehensive loss.

Government Grants

The Company records amounts received under grants as a reduction to research and development expense in the period it has incurred the expenditures in compliance with the specific restrictions of the grant. The Company recorded $129, $96 and $0 for the years ended December 31, 2014, 2013 and 2012, respectively.

Initial Public Offering

On July 23, 2014, the Company completed the sale of 5,750,000 shares of its common stock in its initial public offering (the “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 Nasdaq Global Market on July 18, 2014.

In connection with preparing for the IPO, the Company’s board of directors and stockholders approved a 1-for-3.15 reverse stock split of the Company’s common stock effective July 2, 2014. All share and per share amounts in the financial statements contained herein and notes thereto have been retroactively adjusted, where necessary, to give effect to this reverse stock split. In connection with the closing of the IPO, all of the Company’s outstanding redeemable convertible preferred stock automatically converted into shares of common stock as of July 23, 2014, resulting in the issuance by the Company of an additional 18,007,575 shares of common stock. The significant increase in common stock outstanding in July 2014 will impact the year-over-year comparability of the Company’s net loss per share calculations over the next year.

Recently Issued Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board, (“FASB”), issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606), (“ASU 2014-09”). ASU 2014-09 outlines a new, single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. This new revenue recognition model provides a five-step analysis in determining when and how revenue is recognized. The new model will require revenue recognition to depict the transfer of promised goods or services to customers in an amount that reflects the consideration a company expects to receive in exchange for those goods or services. ASU 2014-09 is effective for public entities for annual reporting periods beginning after December 15, 2016 and interim periods within those periods. Early adoption is not permitted. Companies may use either a full retrospective or a modified retrospective approach to adopt ASU 2014-09. The Company is currently assessing the method of adoption and the impact this new accounting guidance will have on its financial statements and footnote disclosures.

In June 2014, the Financial Accounting Standard Board, or FASB, issued amended accounting guidance for development stage entities. The amendment eliminates certain financial reporting requirements for development stage entities, specifically, the presentation of inception-to-date information, the development stage entity label on the financial statements, the description of the activities in which the entity is engaged, and disclosure in the first year that the entity is no longer a development stage entity that it had been in prior years. The amendment is effective retrospectively for annual reporting periods beginning after December 15, 2014, and interim periods therein with early adoption permitted. The Company elected to early adopt this standard in the period ended June 30, 2014. Other than a change in presentation, the adoption of this guidance did not have an impact on the Company’s financial statements.

In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40). The new guidance addresses management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related footnote disclosures. Management’s evaluation should be based on relevant conditions and events that are known and reasonably knowable at the date that the financial statements are issued. The standard will be effective for the first interim period within annual reporting periods beginning after December 15, 2016. Early adoption is permitted. The Company is evaluating the effect that this guidance will have on its financial statements.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2014

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

4.	Commitments and Contingencies

Operating Leases

The Company rents its 6,500 square foot office space under an operating lease that was executed in 2011 and expires in 2017. In March 2013, the Company entered into a second lease for an additional 4,100 square feet. The second lease, which commenced on August 26, 2013, has a term of 42 months and rent expense of $9 per month. Also in March 2013, the Company signed a sublease agreement to sublet 1,900 square feet. The sublease is for a term of 42 months and rental income is $4 per month.

Rent expense, net of sublease income, for the years ended December 31, 2014, 2013, and 2012 was $302, $274 and $194, respectively.

Future minimum lease payments, net of sublease income, under non-cancelable operating leases are as follows at December 31, 2014:


Years Ending December 31,
2015	$	262
2016		268
2017		45

	$	575

License Agreements

CyDex License Agreement

In October 2011, the Company entered into a research and development license with CyDex Pharmaceuticals, Inc. (“CyDex”) for the development of drug product using licensed technology for a period of one year. Under the terms of the license agreement, the Company paid an initial licensing fee of $200 and an additional fee of $100 for CyDex to perform research and development services to evaluate the licensed technology for formulation with the Company’s developmental product.

The $200 payment was recorded as research and development expense as the acquired technology was in-process research and development, and the $100 payment was recorded to research and development expense in 2011 and 2012 as services were performed.

In December 2012, the Company exercised its option to enter into a commercial license and supply agreement for CyDex’s proprietary technology and paid $100 for the perpetual license, which was recorded as research and development expense.

In August 2013, the Company entered into a commercial license agreement as a result of which the December 2012 license was terminated and the December 2012 supply agreement was amended. Specifically, CyDex granted the Company an exclusive license to the CyDex technology for use in the fields of status epilepticus and traumatic brain injury. In exchange, the Company is required to pay upfront, milestone and royalty-based compensation. In addition, CyDex granted the Company a research license to Captisol for allopregnanolone for use in proof of concept studies. The August 2013 agreement will continue in effect unless and until terminated. In consideration for the amended license rights, the Company paid $300. The Company is obligated to make milestone payments based on achievement of clinical development and regulatory milestones of $900 and $3,750, respectively. Also under this agreement, the Company is required to pay royalties in the low single digits based on levels of net sales.

Under the amended supply agreement with CyDex, the Company is required to purchase all of its supply of Captisol from CyDex and CyDex is required to supply the Company with Captisol, subject to certain limitations.

In April 2014, the Company amended its commercial license and supply agreements with CyDex to expand the fields of use to include the treatment, prevention or diagnosis of any disease or symptom in humans or animals. In consideration for the amended terms, the Company paid $200 upfront and is obligated to make milestone payments, once per field, based on the achievement of clinical development and regulatory milestones for the development of SAGE-547 in the fields of status epilepticus and traumatic brain injury of $750 and $3,750, respectively. For the development in two additional fields, the Company is obligated to make milestone payments, once per field, based on the achievement of clinical development and regulatory milestones of $1,250 and $8,500, respectively.

As of December 31, 2014, the Company had not made any milestone or royalty payments.

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 and is required to pay an annual license maintenance fee of $15 on each subsequent anniversary date, until the first Phase 2 clinical study for a licensed product is initiated. The Company is obligated to make milestone payments based on achievement of clinical development and regulatory milestones of up to $650 and $500, respectively. Additionally, the Company fulfilled its obligation to issue Washington University 47,619 shares of common stock on December 13, 2013. The fair values of these shares totaling $64 were recorded as research and development expense in 2013.

The Company is obligated to pay royalties of low single digits on net sales for licensed products covered under patent rights and royalties of low single digits on net sales for 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.

As of December 31, 2014, the Company had not made any milestone or royalty payments.

University of California License Agreement

In October 2013, the Company entered into a non-exclusive license agreement with The Regents of the University of California whereby the Company was granted a non-exclusive license to certain clinical data and clinical material for use in the development and commercialization of biopharmaceutical products in the licensed field, including status epilepticus and post-partum depression. In May 2014, the license agreement was amended to add the treatment of essential tremor to the licensed field of use, materials and milestone fee provisions of the agreement.

The Company will be required to pay clinical development milestones of up to $100 and pay royalties of less than 1% on net sales for a period of fifteen years following the sale of the first commercial product.

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.

As of December 31, 2014, the Company had not made any milestone or royalty payments.

Consulting Agreement

In January 2014, the Company entered into a consulting agreement with a nonemployee advisor whereby the Company is obligated to make cash payments of up to $2,000 and to issue up to 126,984 shares of common stock upon attainment of certain clinical development and regulatory milestones.

In January and March 2014, the first milestone for each of two programs included in the consulting agreement were met. Accordingly, the Company made cash payments of $50 and issued 15,872 shares of the Company’s common stock. In connection with the shares of common stock issued, the Company recorded $127 as research and development expense for the year ended December 31, 2014.

Redeemable Convertible Preferred Stock

12 Months Ended

Dec. 31, 2014

Redeemable Convertible Preferred Stock [Member]

Redeemable Convertible Preferred Stock

5.	Redeemable Convertible Preferred Stock

As of December 31, 2014 and 2013, the Company’s Certificate of Incorporation, as amended and restated, authorizes the Company to issue no shares and 37,750,000, respectively, shares of $0.0001 par value preferred stock. In July 2014, all issued and outstanding redeemable convertible preferred stock was converted to common stock, see Note 2.

The Company had issued Series A, Series B and Series C redeemable convertible preferred stock (collectively, the “Redeemable Preferred Stock”). The Redeemable Preferred Stock was classified outside of stockholders’ equity (deficit) as of December 31, 2013 because the shares contain redemption features that are not solely within the control of the Company.

On March 18, 2013, the Company issued an additional 5,000,000 shares in the second funding of the second tranche of Series A Preferred Stock at $1.00 per share, resulting in net proceeds of $4,996.

On July 1, 2013, the Company issued an additional 5,000,000 shares in the third funding of the second tranche of Series A Preferred Stock at $1.00 per share, resulting in net proceeds of $4,999.

On September 12, 2013, the Company issued an additional 12,500,000 shares in the third tranche of Series A Preferred Stock at $1.00 per share, resulting in net proceeds of $12,487.

On October 18, 2013, the Company issued 250,000 shares of Series A Preferred Stock at $1.00 per share, resulting in net proceeds of $250.

The Company incurred issuance costs of $18 and $6 in 2013 and 2012, respectively, with the issuance of the Series A Preferred Stock which were recorded as a reduction of the proceeds received. These costs were accreted on a straight-line basis to the carrying value of preferred stock, beginning with the date of issue to the date of earliest redemption.

On October 15, 2013, the Company entered into a Stock Purchase Agreement whereby the Company would issue up to $20,000 of Series B redeemable convertible preferred stock (“Series B Preferred Stock”) at $1.50 per share. The initial purchase and sale in the amount of $10,000 could have occurred once certain development milestones had been successfully achieved. The second tranche of $10,000 could be issued after the initial closing and at the discretion of the Board of Directors. In November 2013, the Company met the development milestones to issue the first tranche of the Series B Preferred Stock.

On January 7, 2014, the Company issued 6,666,666 shares of Series B Preferred Stock at $1.50 per share, resulting in net proceeds of $9,995.

On February 12, 2014, the Company issued 3,333,333 shares of Series B Preferred Stock at $1.50 in a second closing, resulting in net proceeds of $5,000. At that time, the Company decided not to draw on the remaining $5,000 of the second tranche of the Series B Preferred Stock.

The Company incurred issuance costs of $30 in 2014 with the issuance of the Series B Preferred Stock which were recorded as a reduction of the proceeds received.

On March 11, 2014, the Company entered into a Stock Purchase Agreement whereby the Company issued 8,973,905 shares of Series C redeemable convertible preferred stock (“Series C Preferred Stock”) at $4.2345 per share for net proceeds of $37,981.

The Company incurred issuance costs of $110 in 2014 with the issuance of the Series C Preferred Stock which were recorded as a reduction of the proceeds received.

The holders of the Redeemable Preferred Stock had the following rights and preferences:

Voting Rights

The holders of Redeemable Preferred Stock were entitled to vote, together with the holders of common stock, on all matters submitted to stockholders for a vote. Each preferred stockholder was entitled to the number of votes equal to the number of shares of common stock into which each share of Redeemable Preferred Stock was convertible at the time of such vote.

Dividends

The holders of Series A, Series B and Series C Preferred Stock were entitled to receive dividends in preference to any dividend on common stock at the rate of $0.08, $0.12 and $0.34, respectively, per share per annum. Dividends were payable only when, as, and if declared by the Board of Directors. As of December 31, 2014 and 2013, no dividends had been declared or paid by the Company.

Liquidation

In the event of any liquidation, dissolution or winding up of the affairs of the Company, the holders of the Series A, Series B and Series C Preferred Stock were entitled to receive an amount per share equal to the original issue price of $1.00, $1.50 and $4.2345, respectively, per share (the “Original Issue Price”), plus all accruing dividends, whether or not declared, payable in preference and priority to any payments made to the holders of the then outstanding common stock. In the event of a liquidation, dissolution or winding up of the affairs of the Company, holders of Series C Preferred Stock were to be paid their liquidation preference amounts prior to the payment to holders of Series A Preferred Stock and Series B Preferred Stock of their liquidation preference amounts on a pari passu basis. Series A Preferred Stock and Series B Preferred Stock were to be paid their liquidation preference amounts on a pari passu basis prior to the payment of any amounts to holders of common stock. If the liquidation proceeds exceeded the liquidation preferences, then holders of the Series A, Series B and Series C Preferred Stock were to participate in the excess on an as-if converted basis with the common shareholders up to $2.50, $3.75 and $10.58, respectively, per share.

Redemption Rights

Redeemable Preferred Stock was redeemable at the option of the preferred stockholders on or after September 30, 2020. If the holders of at least seventy-five percent of the then outstanding shares of Redeemable Preferred Stock exercised their redemption rights, the Company must notify all preferred stockholders of the election to exercise redemption rights. Under the terms of the Company’s Certificate of Incorporation, as amended and restated on March 11, 2014, the holders of the Redeemable Preferred Stock who requested redemption of their Redeemable Preferred Stock were entitled to receive an amount per share equal to the Original Issue Price of $1.00, $1.50 or $4.2345 for each share of Series A, Series B or Series C Preferred Stock, respectively, plus all accruing dividends, whether or not declared, and were to be paid in three annual installments commencing not more than sixty days after receipt of notification by the Company.

If the Company did not have sufficient funds legally available to redeem all shares of Redeemable Preferred Stock to be redeemed at the redemption date, the Company would redeem such shares ratably to the extent possible and would redeem the remaining shares as soon as sufficient funds are legally available.

Conversion

Each share of Redeemable Preferred Stock was convertible at any time at the option of the shareholder into fully paid and nonassessable shares of common stock determined by dividing the Original Issue Price by the Conversion Price in effect at the time of conversion. The initial Series A, Series B and Series C Conversion Price is $3.15, $4.725 and $13.338675, respectively, per share (the “Conversion Price”).

In addition to the above optional conversion feature, the Redeemable Preferred Stock included a mandatory conversion feature whereby upon either of the following events, all outstanding shares of Redeemable Preferred Stock would automatically be converted into shares of common stock at the then-effective conversion ratio: (i) Initial Public Offering resulting in a closing price of at least $14.18 per share that results in at least $30,000 in gross proceeds to the Company, or (ii) the date and time, or the occurrence of an event, specified by vote or written consent of the holders of at least 75% of the then outstanding shares of Redeemable Preferred Stock. All shares that are required to be surrendered per the provisions above will be deemed to have been retired and canceled and may not be reissued as shares of Redeemable Preferred Stock.

The Company has newly authorized preferred stock amounting to 5,000,000 shares as of December 31, 2014. The newly authorized preferred stock was classified under stockholders’ equity (deficit) as of December 31, 2014.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

7.	Stock-Based Compensation

2014 Stock Option Plan

On July 2, 2014, the Company’s stockholders approved the 2014 Stock Option and Incentive Plan (the “2014 Stock Option Plan”), which became effective upon the completion of the IPO. The 2014 Stock Option Plan provides for the grant of restricted stock awards, incentive stock options and non-statutory stock options. The 2014 Stock Option Plan replaced the Company’s 2011 Stock Option and Grant Plan (the “2011 Stock Option Plan”). The Company will grant no further stock options or other awards under the 2011 Stock Option Plan. Any options or awards outstanding under the 2011 Stock Option Plan remained outstanding and effective. As of December 31, 2014, the total number of shares reserved under all equity plans is 3,505,868, and the Company had 1,509,253 shares available for future issuance under such plans.

The 2014 Stock Option 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 issued and outstanding shares of common stock on the immediately preceding December 31.

2014 Employee Stock Purchase Plan

On July 2, 2014, the Company’s stockholders approved the 2014 Employee Stock Purchase Plan. A total of 282,000 shares of common stock were initially authorized for issuance under this plan. The 2014 Employee Stock Purchase Plan became effective upon the completion of the IPO. As of December 31, 2014, no shares have been issued under this plan.

Terms of restricted stock awards and stock option agreements, including vesting requirements, are determined by the Board of Directors, subject to the provisions of the applicable stock option plan. Options and restricted stock awards granted by the Company generally vest based on the grantee’s continued service with the Company during a specified period following grant. Awards generally vest ratably over four years, with a 25% cliff vesting at the one year anniversary for new employee awards. During 2013, the Company also granted a pool of option awards which vest ratably over one year. All awards are exercisable from the date of grant for a period of ten years.

The stock-based compensation expense recognized during the years ended December 31, 2014, 2013, and 2012 was as follows:


	Year Ended December 31,
	2014		2013		2012
Stock compensation expense:
Research and development	$	1,093	$	38	$	—
General and administrative		1,419		23		—

	$	2,512	$	61	$	—

During the year ended 2012, the Company did not record stock-based compensation expense as the amounts were inconsequential.

Prior to December 31, 2012, the estimated fair market value of the Company’s common stock was determined solely by the Board of Directors on the date of grant. From December 31, 2012 until its IPO, the Company secured a third-party valuation to assist the Board of Directors in the determination of the estimated fair market value of the Company’s common stock.

For stock option awards, the fair value of the options 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 over the requisite service period of the awards. The weighted average grant date fair value per share relating to outstanding stock options granted under the Company’s stock option plans during the years ended December 31, 2014 and 2013 was $14.33 and $0.38, respectively.

The fair value of each option granted to employees and directors during the years ended December 31, 2014, 2013, and 2012 under the Company’s stock option plans has been calculated on the date of grant using the following weighted average assumptions:


	Year Ended December 31,
	2014			2013			2012
Expected dividend yield		0.00	%		0.00	%		0.00	%
Expected volatility		98.86	%		99.89	%		0.00	%
Risk free interest rate		1.95	%		1.66	%		0.00	%
Expected term		6.38 years			6.04 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: As the Company has only been a public company since July 2014, there is not sufficient historical volatility for the expected term of the options. Therefore, the Company used an average historical share price volatility based on an analysis of reported data for a peer group of comparable companies.

Expected term (in years): Expected term represents the period that the Company’s share option grants are expected to be outstanding. As the Company has only been a public company since July 2014, 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 option grants issued 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 termination behavior. For the years ended December 31, 2014, 2013 and 2012, a forfeiture rate of 10% was applied.

For options granted to nonemployees, the expected life of the option used is ten years, which is the contractual term of each such option. All other assumptions used to calculate the grant date fair value are generally consistent with the assumptions used for options granted to employees.

The table below summarizes activity related to stock options:


	Shares			Weighted Average Exercise Price		Weighted Average Remaining Life (in years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2011		—		$	—		—		—

Granted		5,555			0.04
Exercised		(5,555	)		0.04
Forfeited		—			—

Outstanding as of December 31, 2012		—		$	—		—		—

Granted		1,206,655			0.51
Exercised		(3,174	)		0.45
Forfeited		—			—

Outstanding as of December 31, 2013		1,203,481		$	0.51		9.60	$	1,038

Granted		942,513			14.34
Exercised		(87,476	)		0.46
Forfeited		(61,903	)		1.36

Outstanding as of December 31, 2014		1,996,615		$	7.01		8.98	$	59,362

Vested or expected to vest as of December 31, 2014		1,782,257		$	6.61		8.96	$	53,670

Exercisable as of December 31, 2014		383,032		$	0.82		8.66	$	13,705

As of December 31, 2014, the Company had unrecognized stock-based compensation expense related to its unvested stock option awards of $9,705, which is expected to be recognized over the remaining weighted average vesting period of 3.24 years. The total fair value of shares vested for the years ended December 31, 2014, 2013 and 2012 was $988, $9, and $1, respectively. During the year ended December 31, 2014, stock option exercises resulted in proceeds of $40, and during the years ended December 31, 2013 and 2012 stock option exercises resulted in the proceeds of less than $1. The intrinsic value of stock options exercised during the year ended December 31, 2014 was $2,446 and the intrinsic value of stock options exercised during the years ended December 31, 2013 and 2012 was zero.

Restricted Stock Awards

During the years ended December 31, 2014, 2013 and 2012, the Company granted restricted stock awards to certain officers, employees, directors, and consultants of the Company. During the years ended December 31, 2014 and 2013, the Company recorded $213 and $11, respectively, of stock-based compensation expense related to its restricted stock. There was no stock-based compensation expense for the year ended December 31, 2012. The table below summarizes activity relating to restricted stock:


	Shares			Weighted Average Grant Date Fair Value Per Share
Outstanding as of December 31, 2011		613,086			—

Issued		561,104		$	0.04
Vested		(709,158	)		—
Forfeited		—			—
Repurchased		(102,777	)		—

Outstanding as of December 31, 2012		362,255

Issued		130,158		$	0.45
Vested		(176,695	)		—
Forfeited		—			—
Repurchased		—			—

Outstanding as of December 31, 2013		315,718
Issued		—			—
Vested		(138,108	)		—
Forfeited		—			—
Repurchased		(6,778	)		—

Outstanding as of December 31, 2014		170,832

As of December 31, 2014, the Company had unrecognized stock-based compensation expense related to its unvested restricted stock awards of $340, which is expected to be recognized over the remaining weighted average vesting period of 1.15 years.

During the year ended December 31, 2014, no shares of restricted stock were issued. During the years ended December 31, 2013, and 2012, current and former employees of the Company purchased a total of 130,158 and 561,104 shares of restricted stock, respectively, resulting in the proceeds of $50 and $19, respectively.

Unvested shares are subject to repurchase by the Company, at the issuance price, upon the employee’s termination at the Company’s sole discretion. In 2012, the Company repurchased 102,777 shares of restricted common stock issued to employees with a value of $3 in conjunction with the employees’ termination from the Company, and in the year ended December 31, 2014, the Company repurchased 6,778 shares of restricted common stock issued to employees at their $0.04 original purchase price per share.

Income Taxes

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Income Taxes

9.	Income Taxes

There is no 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 U.S. statutory rate to the Company’s effective tax rate is as follows:


	Year Ended December 31,
	2014			2013			2012
Tax due at statutory rate		34.0	%		34.0	%		34.0	%
State taxes, net of federal		4.5			5.2			5.2
Permanent items		(1.0	)		(0.1	)		(0.1	)
Federal and state credits		8.5			1.5			0.8
Change in valuation allowance		(46.0	)		(40.5	)		(39.9	)
Other		—			(0.1	)		—

		0.0	%		0.0	%		0.0	%

Significant components of the Company’s net deferred tax asset at December 31, 2014 and 2013 are as follows:


	December 31,
	2014			2013
Net operating losses		21,907			9,401
Capitalized start-up costs		2,514			2,694
Accounting method change		(2,020	)		—
Tax credit carryforwards		4,433			369
Accrued expenses		494			15
Depreciation and amortization		332			239
Stock options		623			—
Others		20			21

Total net deferred tax asset before valuation allowance		28,303			12,739
Valuation allowance		(28,303	)		(12,739	)

Net deferred tax asset		—			—

As of December 31, 2014, the Company had federal and state net operating loss carryforwards of $55,821 and $55,443, respectively, which begin to expire in 2031. As of December 31, 2014, the Company had federal and state research and development tax credits carryforwards of $663 and $326, respectively, which begin to expire in 2031 and 2027, respectively. As of December 31, 2014, the Company had federal orphan drug tax credit carry forwards of $3,555, which begin to expire in 2034.

As of December 31, 2014, net deferred tax assets increased approximately $15,564 primarily due to the operating loss 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 capitalized start-up costs. 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 $28,303 and $12,739 has been established at December 31, 2014 and 2013, respectively.

Pursuant to Section 382 of the Internal Revenue Code, 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 has not completed a study to assess whether an ownership change has occurred, or whether there have been multiple ownership changes since its formation, due to significant complexity and related costs associated with such a study. There could also be additional ownership changes in the future which may result in additional limitations on the utilization of NOL carryforwards and credits.

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

The following is a rollforward of the Company’s unrecognized tax benefits:


	Year Ended December 31,
	2014			2013		2012
Unrecognized tax benefits—as of the beginning of the year	$	2,880		$	1,477	$	504
Gross increases—current period tax positions		—			1,403		—
Gross decreases—tax positions of prior periods		(2,880	)		—		973

Unrecognized tax benefits—as of the end of the year	$	—		$	2,880	$	1,477

During 2014, the Company filed an application for change in accounting method with the IRS to capitalize start-up costs that were historically deducted and included as part of the NOL carryforward through December 31, 2013. As a result, the Company’s unrecognized tax benefits, which historically related to start-up costs, are zero at December 31, 2014.

The Company will recognize interest and penalties related to uncertain tax positions in income tax expense when in a taxable income position. As of December 31, 2014 and 2013, the Company had no accrued interest or penalties related to uncertain tax positions 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 and state jurisdictions, where applicable. There are currently no pending tax examinations, and the Company’s tax returns are open under statute from 2011 to the present. The Company’s policy is to record interest and penalties related to income taxes as part of the tax provision.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Basis of Presentation

Basis of Presentation

Use of Estimates

Use of Estimates

Cash and Cash Equivalents

Cash and Cash Equivalents

The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents.

Restricted Cash

Restricted Cash

Property and Equipment

Property and Equipment

Impairment of Long-Lived Assets

Impairment of Long-Lived Assets

Research and Development

Research and Development

Research Contract Costs and Accruals

Research Contract Costs and Accruals

Patent Costs

Patent Costs

The Company expenses patent costs as incurred and classifies such costs as general and administrative expenses in the accompanying statements of operations and comprehensive loss.

Stock-Based Compensation

Stock-Based Compensation

Basic and Diluted Net Income (Loss) Per Share

Basic and Diluted Net Income (Loss) Per Share

The Company reported a net loss attributable to common stockholders for the years ended December 31, 2014, 2013 and 2012.

Risks and Uncertainties

Risks and Uncertainties

Concentration of Credit Risk and of Significant Suppliers

Concentration of Credit Risk and of Significant Suppliers

Income Taxes

Income Taxes

Fair Value Measurements

Fair Value Measurements


Level 1	—	Quoted market prices in active markets for identical assets or liabilities. At December 31, 2014 and 2013, the Company’s Level 1 assets consisted of money market funds totaling $127,766 and $8,066, respectively.

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. At December 31, 2014 and 2013, the Company had no Level 2 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. At December 31, 2014 and 2013, the Company had no Level 3 assets or liabilities.

Deferred Offering Costs

Deferred Offering Costs

Segment Data

Segment Data

Comprehensive Loss

Comprehensive Loss

Government Grants

Government Grants

Initial Public Offering

Initial Public Offering

Recently Issued Accounting Pronouncements

Recently Issued Accounting Pronouncements

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Recognized Stock-Based Compensation Expense

The stock-based compensation expense recognized during the years ended December 31, 2014, 2013, and 2012 was as follows:


	Year Ended December 31,
	2014		2013		2012
Stock compensation expense:
Research and development	$	1,093	$	38	$	—
General and administrative		1,419		23		—

	$	2,512	$	61	$	—

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


	Year Ended December 31,
	2014			2013			2012
Expected dividend yield		0.00	%		0.00	%		0.00	%
Expected volatility		98.86	%		99.89	%		0.00	%
Risk free interest rate		1.95	%		1.66	%		0.00	%
Expected term		6.38 years			6.04 years			—

Summary of Activity Relating to Stock Options

The table below summarizes activity related to stock options:


	Shares			Weighted Average Exercise Price		Weighted Average Remaining Life (in years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2011		—		$	—		—		—

Granted		5,555			0.04
Exercised		(5,555	)		0.04
Forfeited		—			—

Outstanding as of December 31, 2012		—		$	—		—		—

Granted		1,206,655			0.51
Exercised		(3,174	)		0.45
Forfeited		—			—

Outstanding as of December 31, 2013		1,203,481		$	0.51		9.60	$	1,038

Granted		942,513			14.34
Exercised		(87,476	)		0.46
Forfeited		(61,903	)		1.36

Outstanding as of December 31, 2014		1,996,615		$	7.01		8.98	$	59,362

Vested or expected to vest as of December 31, 2014		1,782,257		$	6.61		8.96	$	53,670

Exercisable as of December 31, 2014		383,032		$	0.82		8.66	$	13,705

Summary of Activity Relating to Restricted Stock

The table below summarizes activity relating to restricted stock:


	Shares			Weighted Average Grant Date Fair Value Per Share
Outstanding as of December 31, 2011		613,086			—

Issued		561,104		$	0.04
Vested		(709,158	)		—
Forfeited		—			—
Repurchased		(102,777	)		—

Outstanding as of December 31, 2012		362,255

Issued		130,158		$	0.45
Vested		(176,695	)		—
Forfeited		—			—
Repurchased		—			—

Outstanding as of December 31, 2013		315,718
Issued		—			—
Vested		(138,108	)		—
Forfeited		—			—
Repurchased		(6,778	)		—

Outstanding as of December 31, 2014		170,832

Summary of Significant Accounting Policies - Additional Information (Detail)			1 Months Ended	12 Months Ended
	Jul. 23, 2014 USD ($) $ / shares shares	Jul. 02, 2014	Jul. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Restricted cash deposit				$ 39,000	$ 39,000
Payment of offering costs				2,285,000
Proceeds from initial public offering of common stock, net of commissions and underwriting discounts			$ 96,300,000	$ 96,255,000
Reverse stock split description				In connection with preparing for the IPO, the Company's board of directors and stockholders approved a 1-for-3.15 reverse stock split of the Company's common stock
Reverse stock split effective date				Jul. 02, 2014
Reverse stock split ratio		0.3175
Issuance of additional shares of common stock upon conversion \| shares	18,007,575
Research and Development [Member]
Summary Of Significant Accounting Policies [Line Items]
Government grants				$ 129,000	96,000	$ 0
Fair Value, Inputs, Level 1 [Member] \| Money Market Funds [Member]
Summary Of Significant Accounting Policies [Line Items]
Assets fair value				127,766,000	8,066,000
Fair Value, Inputs, Level 2 [Member]
Summary Of Significant Accounting Policies [Line Items]
Assets fair value				0	0
Liabilities fair value				0	0
Fair Value, Inputs, Level 3 [Member]
Summary Of Significant Accounting Policies [Line Items]
Assets fair value				0	0
Liabilities fair value				$ 0	$ 0
Initial Public Offering [Member]
Summary Of Significant Accounting Policies [Line Items]
Issuance of common stock, Shares \| shares	5,750,000
Initial public offering, common stock price per share \| $ / shares	$ 18.00
Proceeds from initial public offering of common stock, net of commissions and underwriting discounts	$ 94,000,000

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended						12 Months Ended
	Apr. 30, 2014 USD ($)	Jan. 31, 2014 USD ($) shares	Nov. 30, 2013 USD ($)	Aug. 31, 2013 USD ($)	Mar. 31, 2013 USD ($) ft²	Oct. 31, 2011 USD ($)	Dec. 31, 2014 USD ($) ft² shares	Dec. 31, 2013 USD ($) shares	Dec. 31, 2012 USD ($)	Oct. 31, 2013 USD ($)
Commitments And Contingencies [Line Items]
Area of leased property \| ft²					4,100
Operating lease commence date							Aug. 26, 2013
Lease term					42 months
Rent expense per month					$ 9,000
Rent expense, net of sublease income							$ 302,000	$ 274,000	$ 194,000
Research and development expense							$ 24,100,000	14,357,000	7,229,000
CyDex License Agreement [Member]
Commitments And Contingencies [Line Items]
License agreement term							1 year
Initial licensing fee						$ 200,000
Additional license fee						$ 100,000
Research and development expense							$ 200,000		100,000
Milestone payments							0
Commercial License and Supply Agreements [Member] \| Research and Development [Member]
Commitments And Contingencies [Line Items]
Perpetual license fee									$ 100,000
License Agreement Terms [Member]
Commitments And Contingencies [Line Items]
Upfront payment				$ 300,000
License Agreement Terms [Member] \| Clinical Development [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments				900,000
License Agreement Terms [Member] \| Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments				$ 3,750,000
Amended and Restated License Agreement [Member]
Commitments And Contingencies [Line Items]
Upfront payment	$ 200,000
Amended and Restated License Agreement [Member] \| Clinical Development [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	1,250,000
Amended and Restated License Agreement [Member] \| Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	$ 8,500,000
Amended and Restated License Agreement [Member] \| Clinical Development And Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments							750,000	3,750,000
Washington University License Agreement [Member]
Commitments And Contingencies [Line Items]
Research and development expense								64,000
Milestone payments							0	$ 0
Upfront non-refundable payment			$ 50,000
Annual license maintenance fee			15,000
Issuance of common stock ,shares \| shares								47,619
Washington University License Agreement [Member] \| Clinical Development [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments			650,000
Washington University License Agreement [Member] \| Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments			$ 500,000
University of California License Agreement [Member]
Commitments And Contingencies [Line Items]
Milestone payments							$ 0	$ 0
License payment description							The Company will be required to pay clinical development milestones of up to $100 and pay royalties of less than 1% on net sales for a period of fifteen years following the sale of the first commercial product.
Percentage of net sales							1.00%
University of California License Agreement [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Licenses Expiration period							27 years
University of California License Agreement [Member] \| Minimum [Member]
Commitments And Contingencies [Line Items]
Licenses Expiration period							15 years
University of California License Agreement [Member] \| Clinical Development [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments										$ 100,000
Consulting Agreement [Member]
Commitments And Contingencies [Line Items]
Research and development expense							$ 127,000
Milestone payments							$ 50,000
Issuance of common stock ,shares \| shares							15,872
Consulting Agreement [Member] \| Clinical Development And Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Issuance of common stock ,shares \| shares		126,984
Milestone payment		$ 2,000,000
Operating Lease One [Member]
Commitments And Contingencies [Line Items]
Operating lease start year							2011
Office space rented under operating lease \| ft²							6,500
Operating lease end year							2017
Sublease Agreement [Member]
Commitments And Contingencies [Line Items]
Area of leased property \| ft²					1,900
Lease term					42 months
Lease income per month					$ 4,000

Redeemable Convertible Preferred Stock - Additional Information (Detail) - USD ($)								12 Months Ended
	Mar. 11, 2014	Feb. 12, 2014	Jan. 07, 2014	Oct. 18, 2013	Sep. 12, 2013	Jul. 01, 2013	Mar. 18, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 30, 2013	Oct. 15, 2013
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized								0	37,750,000
Redeemable convertible preferred stock, par value								$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares issued								0	37,750,000
Redeemable convertible preferred stock									$ 37,709,000
Dividends declared								$ 0	$ 0
Redeemable preferred stock, earliest redemption date								Sep. 30, 2020
Maximum redemption percentage								75.00%
Redemption of preferred units								Under the terms of the Company’s Certificate of Incorporation, as amended and restated on March 11, 2014, the holders of the Redeemable Preferred Stock who requested redemption of their Redeemable Preferred Stock were entitled to receive an amount per share equal to the Original Issue Price of $1.00, $1.50 or $4.2345 for each share of Series A, Series B or Series C Preferred Stock, respectively, plus all accruing dividends, whether or not declared, and were to be paid in three annual installments commencing not more than sixty days after receipt of notification by the Company.
Preferred stock, shares authorized								5,000,000	0
Minimum [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, redemption price								$ 14.18
Proceeds from the issuance of preferred stock, gross								$ 30,000,000
Percentage of outstanding shares of preferred stock								75.00%
Series A Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value				$ 1.00
Redeemable convertible preferred stock, shares issued				250,000
Proceeds from the issuance of preferred stock, net proceeds				$ 250,000
Redeemable convertible preferred Stock, issuance costs									$ 18,000	$ 6,000
Dividends payable								$ 0.08
Dividends declared								$ 0	0
Liquidation Preference, per share								$ 1.00
Redeemable convertible preferred stock, redemption price								1.00
Redeemable convertible preferred stock, conversion rate								3.15
Proceeds from the issuance of preferred stock, gross									22,732,000	$ 8,994,000
Series A Preferred Stock [Member] \| Maximum [Member]
Temporary Equity [Line Items]
Liquidation proceeds, in excess of liquidation Preference, per share								$ 2.50
Series A Preferred Stock [Member] \| Second Tranche [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value						$ 1.00	$ 1.00
Redeemable convertible preferred stock, shares issued						5,000,000	5,000,000
Proceeds from the issuance of preferred stock, net proceeds						$ 4,999,000	$ 4,996,000
Series A Preferred Stock [Member] \| Third Tranche [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value					$ 1.00
Redeemable convertible preferred stock, shares issued					12,500,000
Proceeds from the issuance of preferred stock, net proceeds					$ 12,487,000
Series B Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value		$ 1.50	$ 1.50									$ 1.50
Redeemable convertible preferred stock, shares issued		3,333,333	6,666,666									20,000,000
Proceeds from the issuance of preferred stock, net proceeds		$ 5,000,000	$ 9,995,000
Redeemable convertible preferred Stock, issuance costs								$ 30,000
Redeemable convertible preferred stock												$ 10,000,000
Dividends payable								$ 0.12
Dividends declared								$ 0	0
Liquidation Preference, per share								$ 1.50
Redeemable convertible preferred stock, redemption price								1.50
Redeemable convertible preferred stock, conversion rate								$ 4.725
Proceeds from the issuance of preferred stock, gross								$ 14,970,000
Series B Preferred Stock [Member] \| Maximum [Member]
Temporary Equity [Line Items]
Liquidation proceeds, in excess of liquidation Preference, per share								$ 3.75
Series B Preferred Stock [Member] \| Second Tranche [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, Undrawn amount		$ 5,000,000
Series B Preferred Stock [Member] \| First Tranche [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock											$ 10,000,000
Series C Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, par value	$ 4.2345
Redeemable convertible preferred stock, shares issued	8,973,905
Proceeds from the issuance of preferred stock, net proceeds	$ 37,981,000
Redeemable convertible preferred Stock, issuance costs								$ 110,000
Dividends payable								$ 0.34
Dividends declared								$ 0	$ 0
Liquidation Preference, per share								$ 4.2345
Redeemable convertible preferred stock, redemption price								4.2345
Redeemable convertible preferred stock, conversion rate								$ 13.338675
Proceeds from the issuance of preferred stock, gross								$ 37,890,000
Series C Preferred Stock [Member] \| Maximum [Member]
Temporary Equity [Line Items]
Liquidation proceeds, in excess of liquidation Preference, per share								$ 10.58

Stock-Based Compensation - Additional Information (Detail) - USD ($)		12 Months Ended
	Jul. 02, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share option, forfeiture rate		10.00%	10.00%	10.00%
Contractual term, option		10 years
Stock-based compensation expense		$ 2,512,000	$ 61,000
Proceeds from restricted shares sold to employees		40,000	51,000	$ 3,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense		$ 340,000
Weighted average period of unrecognized compensation costs		1 year 1 month 24 days
Stock-based compensation expense		$ 213,000	$ 11,000	$ 0
Issued, Shares--Restricted stock		0	130,158	561,104
Proceeds from restricted shares sold to employees			$ 50,000	$ 19,000
Stock repurchased, shares		6,778		102,777
Stock repurchased, value				$ 3,000
Stock repurchased, purchase price per share		$ 0.04
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option grant		942,513	1,206,655	5,555
Unrecognized stock-based compensation expense		$ 9,705,000
Weighted average period of unrecognized compensation costs		3 years 2 months 27 days
Total fair value of shares vested		$ 988,000	$ 9,000	$ 1,000
Proceeds from stock options exercised		40,000
Intrinsic value of options exercised		$ 2,446,000	0	0
Stock Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from stock options exercised			$ 1,000	$ 1,000
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under the plan	282,000
Number of shares issued under the plan		0
2011 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option grant		0
2014 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance under the plan		1,509,253
Total number of shares reserved under equity plan	3,505,868
Share based compensation granted under plan vest period		4 years	1 year
Share based compensation, vest period		1 year
Share based compensation, term of plan		10 years
Share based compensation, vesting percentage		25.00%
Weighted average grant date fair value per share		$ 14.33	$ 0.38
2014 Stock Option Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of increase on issued and outstanding shares of Common stock	4.00%

Stock-Based Compensation - Summary of Activity Relating to Stock Options (Detail) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Shares--Stock options	1,203,481
Granted, Shares--Stock options	942,513	1,206,655	5,555
Exercised, Shares--Stock options	(87,476)	(3,174)	(5,555)
Forfeited, Shares--Stock options	(61,903)
Ending balance, Outstanding Shares--Stock options	1,996,615	1,203,481
Beginning balance, Weighted Average Exercise Price--Stock options	$ 0.51
Vested or expected to vest, Shares--Stock options	1,782,257
Granted, Weighted Average Exercise Price--Stock options	$ 14.34	$ 0.51	$ 0.04
Exercisable, Shares--Stock options	383,032
Exercised, Weighted Average Exercise Price--Stock options	$ 0.46	0.45	$ 0.04
Forfeited, Weighted Average Exercise Price--Stock options	1.36
Ending balance, Outstanding Weighted Average Exercise Price--Stock options	7.01	$ 0.51
Vested or expected to vest, Weighted Average Exercise Price--Stock options	6.61
Exercisable, Weighted Average Exercise Price--Stock options	$ 0.82
Outstanding, Weighted Average Remaining Life--Stock options	8 years 11 months 23 days	9 years 7 months 6 days
Vested or expected to vest, Weighted Average Remaining Life--Stock options	8 years 11 months 16 days
Exercisable, Weighted Average Remaining Life--Stock options	8 years 7 months 28 days
Outstanding, Aggregate Intrinsic Value--Stock options	$ 59,362	$ 1,038
Vested or expected to vest, Aggregate Intrinsic Value--Stock options	53,670
Exercisable, Aggregate Intrinsic Value--Stock options	$ 13,705

Stock-Based Compensation - Summary of Activity Relating to Restricted Stock (Detail) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted common stock, Shares at beginning balance--Restricted stock	315,718	362,255	613,086
Issued, Shares--Restricted stock	0	130,158	561,104
Vested, Shares--Restricted stock	(138,108)	(176,695)	(709,158)
Forfeited, Shares--Restricted stock	0	0	0
Repurchased, Shares--Restricted stock	(6,778)		(102,777)
Unvested restricted common stock, Shares at ending balance--Restricted stock	170,832	315,718	362,255
Unvested restricted common stock , Weighted Average Grant Date Fair Value Per Share, beginning balance--Restricted stock	$ 0	$ 0	$ 0
Issued, Weighted Average Grant Date Fair Value Per Share--Restricted stock		0.45	0.04
Vested, Weighted Average Grant Date Fair Value Per Share--Restricted stock	0	0	0
Forfeited, Weighted Average Grant Date Fair Value Per Share--Restricted stock	0	0	0
Repurchased, Weighted Average Grant Date Fair Value Per Share--Restricted stock	0	0	0
Unvested restricted common stock, Weighted Average Grant Date Fair Value Per Share, ending balance--Restricted stock	$ 0	$ 0	$ 0

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Line Items]
Provision for income taxes	$ 0
Federal orphan drug tax credit carry forwards	$ 3,555,000
Tax credit carry forwards expiration period	2034
Change in amount of deferred tax assets	$ 15,564,000
Federal operating loss carryforwards	55,821,000
State operating loss carryforwards	$ 55,443,000
Federal and state net operating loss carryforwards expiration year	2031
Valuation allowance	$ 28,303,000	$ 12,739,000
Income tax position description	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.
Unrecognized tax benefit related to start-up costs	$ 0	2,880,000	$ 1,477,000	$ 504,000
Accrued interest or penalties related to uncertain tax positions	0	$ 0
Domestic Tax Authority [Member]
Income Tax Disclosure [Line Items]
Research and development tax credits carryforwards	$ 663,000
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	$ 326,000
Research and development tax credits carryforwards expiration year	2027

Income Taxes - Summary of Reconciliation of U.S. Statutory Rate to Company's Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Tax due at statutory rate	34.00%	34.00%	34.00%
State taxes, net of federal	4.50%	5.20%	5.20%
Permanent Items	(1.00%)	(0.10%)	(0.10%)
Federal and state credits	8.50%	1.50%	0.80%
Change in valuation allowance	(46.00%)	(40.50%)	(39.90%)
Other		(0.10%)
Total effective tax rate	0.00%	0.00%	0.00%

Income Taxes - Summary of Significant Components of Company's Net Deferred Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Net operating losses	$ 21,907	$ 9,401
Capitalized start-up costs	2,514	2,694
Accounting method change	(2,020)
Tax credit carryforwards	4,433	369
Accrued expenses	494	15
Depreciation and amortization	332	239
Stock options	623
Others	20	21
Total net deferred tax asset before valuation allowance	28,303	12,739
Valuation allowance	(28,303)	(12,739)
Net deferred tax asset	$ 0	$ 0

Balance Sheet Components - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 309	$ 181
Less: Accumulated depreciation	(146)	(95)
Property and equipment, net	$ 163	86
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Property and equipment, gross	$ 206	78
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years
Property and equipment, gross	$ 103	$ 103

Balance Sheet Components - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Payables and Accruals [Abstract]
Employee related expenses	$ 1,279	$ 49
Development costs	2,788	57
Professional services	574	190
Other accrued expenses	46	31
Total accrued expenses	$ 4,687	$ 327

Net Loss Per Share - Summary of Common Stock Equivalents Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	1,791,973	9,072,460
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	1,621,906	766,156
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents	170,067	284,129
Redeemable Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common stock equivalents		8,022,175

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Nov. 01, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options Outstanding, Weighted Average Exercise Price, and Additional Disclosures [Abstract]
Employer matching contribution, percent of match	50.00%
Maximum annual contributions per employee, percent	6.00%
Employer contribution		$ 15

Related Party Transactions - Additional Information (Detail) - Third Rock Ventures LLC [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Payment for consulting and management services	$ 282	$ 682	$ 994
Accrued expenses to related parties	$ 5
Accounts payable to related parties		$ 125	$ 209
Percentage of ownership held with related party transactions	45.30%

Nature of the Business - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Nature Of Business [Line Items]
Accumulated deficit		$ (66,845)	$ (31,675)
Gross proceeds from sale of common stock	$ 96,300	96,255
Cash balance		127,766	$ 8,066	$ 2,802	$ 2,842
Redeemable Convertible Preferred Stock [Member]
Nature Of Business [Line Items]
Convertible preferred stock proceeds raised		$ 90,600

Commitments and Contingencies - Schedule of Future Minimum Lease Payments, Net of Sublease Income, Under Non-Cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2014 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2015	$ 262
2016	268
2017	45
Total Operating leases, future minimum payments	$ 575

Common Stock - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Common stock, shares authorized	120,000,000	66,000,000
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.

Subsequent Events - Additional Information (Detail) $ in Thousands		1 Months Ended
	Jan. 01, 2015 USD ($) ft²	Mar. 31, 2013 ft²
Subsequent Event [Line Items]
Area of leased property		4,100
Subsequent Event [Member]
Subsequent Event [Line Items]
Area of leased property	2,700
Lease term expiration	2017-07
Lease payment per month \| $	$ 9