STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating expenses:
Research and development	$ 7,975	$ 14,959	$ 14,157
General and administrative	18,932	2,706	1,885
Total operating expenses	26,907	17,665	16,042
Loss from operations	(26,907)	(17,665)	(16,042)
Other expense (income):
Interest expense, net	439	252	76
Gain (loss) on extinguishment of debt	(91)		79
Change in fair value of derivative liability			79
Total other expense, net	348	252	155
Net loss	$ (27,255)	$ (17,917)	$ (16,197)
Net loss per share - basic and diluted (in dollars per share)	$ (1.48)	$ (22.72)	$ (4.06)
Weighted-average number of common shares used in net loss per share-basic and diluted (in shares)	13,542,282	933,997	1,697,044