Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating expenses:
Research and development	$ 11,307	$ 7,502	$ 23,307	$ 14,095
General and administrative	4,126	3,396	8,241	5,725
Total operating expenses	15,433	10,898	31,548	19,820
Loss from operations	(15,433)	(10,898)	(31,548)	(19,820)
Other income (expense), net	50	(182)	78	(331)
Net loss	(15,383)	(11,080)	(31,470)	(20,151)
Accretion to redemption value of redeemable convertible preferred stock		(15)		(15)
Net loss attributable to common stockholders	$ (15,383)	$ (11,095)	$ (31,470)	$ (20,166)
Net loss per share, basic and diluted	$ (0.65)	$ (0.74)	$ (1.33)	$ (2.53)
Weighted average common stock shares outstanding, basic and diluted	23,672,527	14,901,473	23,655,366	7,955,973