CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating expenses:
Research and development	$ 15,339	$ 6,507	$ 3,488
General and administrative	5,328	2,026	1,769
Total operating expenses	20,667	8,533	5,257
Loss from operations	(20,667)	(8,533)	(5,257)
Interest income	104	16	21
Net loss	(20,563)	(8,517)	(5,236)
Accretion of convertible preferred stock	(2,566)	(2,054)	(1,740)
Net loss attributable to common stockholders	$ (23,129)	$ (10,571)	$ (6,976)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (3.79)	$ (6.15)	$ (6.45)
Weighted average common shares outstanding, basic and diluted (in shares)	6,107,042	1,720,082	1,081,347
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities, net of tax of $0	$ (148)	$ (9)	$ 3
Foreign currency translation adjustments	5
Total other comprehensive income (loss)	(143)	(9)	3
Comprehensive loss	$ (20,706)	$ (8,526)	$ (5,233)