Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Collaboration and license revenue	$ 3,550	$ 3,550
Operating expenses
Research and development	8,130	6,616
General and administrative	3,860	1,765
Total operating expenses	11,990	8,381
Loss from operations	(8,440)	(4,831)
Interest and other income, net	20	17
Change in fair value of redeemable convertible preferred stock call option liability		314
Net loss and comprehensive loss	(8,420)	(4,500)
Cumulative dividend relating to redeemable convertible preferred stock		(952)
Accretion of redeemable convertible preferred stock to redemption value		(33)
Net loss attributable to common stockholders	$ (8,420)	$ (5,485)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.32)	$ (2.47)
Weighted-average number of common shares used to compute net loss per share, basic and diluted	26,169,152	2,221,751

Change in fair value of temporary equity call option liability.

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Collaboration and license revenue.

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Interest and other income (expense), net.

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense.

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The net result for the period of deducting operating expenses from operating revenues.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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Amount of decrease to net income for accretion of temporary equity to its redemption value to derive net income apportioned to common stockholders.

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Accretion of temporary equity during the period due to cash, stock, and in-kind dividends. This item is an adjustment to net income necessary to derive net income apportioned to common stockholders and is to be distinguished from Temporary Equity, Accretion of Dividends (Temporary Equity, Accretion of Dividends).

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Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

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