Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating expenses:
Research and development	$ 6,636	$ 5,296
General and administrative	3,977	1,441
Total operating expenses	10,613	6,737
Loss from operations	(10,613)	(6,737)
Other income (expense), net:
Change in fair value of preferred stock warrants		(1,326)
Other income	83	25
Total other income (expense), net	83	(1,301)
Loss before provision for income taxes	(10,530)	(8,038)
Provision for income taxes	8	10
Net loss	(10,538)	(8,048)
Adjustment to redemption value on redeemable convertible preferred stock		(11,005)
Net loss attributable to common stockholders	$ (10,538)	$ (19,053)
Net loss per share attributable to common stockholders, basic and diluted (Note 3)	$ (0.35)	$ (12.83)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (Note 3)	30,070,227	1,485,609