Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating expenses:
Research and development	$ 25,622	$ 13,365	$ 9,154
General and administrative	7,467	5,150	3,574
Total operating expenses	33,089	18,515	12,728
Loss from operations	(33,089)	(18,515)	(12,728)
Other income (expense)
Interest expense	(2,077)	(1,566)	(1,513)
Interest income	5	3	1
Change in fair value of warrants	(110)	348	(81)
Loss on extinguishment of debt	(1,036)
Loss before benefit from income taxes	(36,307)	(19,730)	(14,321)
Benefit from income taxes	5,972	3,653
Net loss	$ (30,335)	$ (16,077)	$ (14,321)
Net loss per share (basic and diluted) (in dollars per share)	$ (1.38)	$ (1.41)	$ (289.39)
Weighted-average shares outstanding (basic and diluted) (in shares)	22,017,229	11,394,971	49,486