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	$ 5,813	$ 4,543	$ 16,360	$ 11,361
General and administrative	2,388	1,427	5,966	4,443
Total operating expenses	8,201	5,970	22,326	15,804
Loss from operations	(8,201)	(5,970)	(22,326)	(15,804)
Other (expense) income:
Other (expense) income, net	(2)	2	11	3
Interest expense	(282)	(57)	(709)	(57)
Total other expense	(284)	(55)	(698)	(54)
Net loss and comprehensive loss	$ (8,485)	$ (6,025)	$ (23,024)	$ (15,858)
Net loss per share - basic and diluted (in dollars per share)	$ (0.55)	$ (13.55)	$ (4.11)	$ (38.34)
Weighted-average common shares outstanding used in net loss per share - basic and diluted (in shares)	15,297,794	444,787	5,596,412	413,622