Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating expenses:
Research and development	$ 25,450	$ 23,030	$ 15,686
General and administrative	10,108	8,629	5,995
Total operating expenses	35,558	31,659	21,681
Loss from operations	(35,558)	(31,659)	(21,681)
Other (expense) income:
Interest expense	(837)	(978)	(206)
Interest and investment income	242
Other income, net	93	7	3
Total other expense, net	(502)	(971)	(203)
Net loss	$ (36,060)	$ (32,630)	$ (21,884)
Net loss per share - basic and diluted (in dollars per share)	$ (2.22)	$ (4.06)	$ (51.56)
Weighted-average common shares outstanding used in net loss per share - basic and diluted (in shares)	16,230,190	8,041,948	424,477