Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating expenses
Research and development	$ 6,092	$ 3,511	$ 18,379	$ 8,274
General and administrative	2,826	12	8,097	2,754
Impairment of intangible assets	17,315		17,315
Total operating expenses	26,233	3,523	43,791	11,028
Loss from operations	(26,233)	(3,523)	(43,791)	(11,028)
Other income (expense), net
Interest expense	(335)	(1,514)	(2,770)	(3,795)
Change in fair value of preferred stock warrant liabilities		2,097	1,939	1,408
Loss before income tax benefit (expense)	(26,568)	(2,940)	(44,622)	(13,415)
Income tax benefit (expense)	4,357		4,392	(271)
Net loss and comprehensive loss	$ (22,211)	$ (2,940)	$ (40,230)	$ (13,686)
Net loss per share, basic and diluted	$ (1.22)	$ (7.29)	$ (4.05)	$ (33.91)
Weighted-average common shares outstanding, basic and diluted	18,184,146	403,539	9,929,260	403,539