Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenue:
License fees	$ 305	$ 305
Total revenues	305	305
Operating expenses:
Research and development	9,552	4,786
General and administrative	3,930	4,272
Total operating expenses	13,482	9,058
Loss from operations	(13,177)	(8,753)
Other income (expense):
Interest income, net	259	144
Change in fair value of common stock warrant liability		(1,703)
Other expense, net	(53)	(18)
Total other income (expense)	206	(1,577)
Net loss	(12,971)	(10,330)
Other comprehensive (loss) income:
Unrealized (losses) gains on marketable securities	(58)	200
Comprehensive loss	(13,029)	(10,130)
Net loss attributable to common stockholders	$ (12,971)	$ (12,928)
Net loss per share attributable to common stockholders-basic and diluted	$ (0.71)	$ (2.85)
Weighted-average number of common shares used to compute net loss per share attributable to common stockholders-basic and diluted	18,231,602	4,541,536