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	$ 29,802	$ 25,302	$ 16,014
General and administrative	20,238	10,922	6,745
Total operating expenses	50,040	36,224	22,759
Loss from operations	(50,040)	(36,224)	(22,759)
Interest expense.	(520)	(270)	(936)
Change in fair value of warrant liability			(2,587)
Other income, net	776	119	194
Net loss	$ (49,784)	$ (36,375)	$ (26,088)
Net loss per common share (basic and diluted) (in dollars per share)	$ (2.26)	$ (2.22)	$ (3.31)
Weighted-average shares outstanding (basic and diluted)	22,019,818	16,374,102	7,885,921
Other comprehensive income (loss):
Unrealized ( loss) on investments	$ (423)	$ (56)	$ (3)
Total comprehensive loss	$ (50,207)	$ (36,431)	$ (26,091)