Condensed 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	$ 24,672	$ 12,181	$ 12,413
General and administrative	10,871	7,840	2,764
Impairment of intangible assets	17,315
Total operating expenses	52,858	20,021	15,177
Loss from operations	(52,858)	(20,021)	(15,177)
Other income (expense), net
Interest expense	(3,091)	(4,989)	(3,684)
Change in fair value of preferred stock warrant liabilities	1,939	1,181	272
Loss before income tax benefit (expense)	(54,010)	(23,829)	(18,589)
Income tax benefit (expense)	4,393	(271)	0
Net loss and comprehensive loss	$ (49,617)	$ (24,100)	$ (18,589)
Net loss per share, basic and diluted	$ (4.08)	$ (59.72)	$ (47.31)
Weighted-average common shares outstanding, basic and diluted	12,168,354	403,539	392,926