CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating expenses:
Research and development	$ 7,162	$ 9,407	$ 26,533	$ 12,937
General and administrative	3,650	1,233	10,407	2,928
Total operating expenses	10,812	10,640	36,940	15,865
Loss from operations	(10,812)	(10,640)	(36,940)	(15,865)
Other income, net	118	8	336	16
Net loss	(10,694)	(10,632)	(36,604)	(15,849)
Accretion of convertible preferred stock		(1,020)		(2,353)
Net loss attributable to common stockholders	$ (10,694)	$ (11,652)	$ (36,604)	$ (18,202)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.50)	$ (5.12)	$ (1.76)	$ (8.44)
Weighted average common shares outstanding, basic and diluted (in shares)	21,415,871	2,274,617	20,752,590	2,155,685
Other comprehensive (loss) income:
Unrealized (loss) gain on marketable securities, net of tax of $0	$ (12)	$ 1	$ 144	$ 7
Foreign currency translation adjustments	(43)		(49)
Total other comprehensive (loss) income	(55)	1	95	7
Comprehensive loss	$ (10,749)	$ (10,631)	$ (36,509)	$ (15,842)