Condensed Statements of Operations and Comprehensive Loss (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Operating expenses:
Research and development	$ 6,528	$ 3,100	$ 11,928	$ 5,193
General and administrative	2,726	1,172	5,216	2,423
Total operating expenses	9,254	4,272	17,144	7,616
Loss from operations	(9,254)	(4,272)	(17,144)	(7,616)
Interest expense.	(1)	(108)	(1)	(936)
Change in fair value of warrant liability	0	(2,545)	0	(2,587)
Other income (expense), net	17	4	33	(21)
Net loss	(9,238)	(6,921)	(17,112)	(11,160)
Net loss per common share (basic and diluted) (in dollars per share)	$ (0.60)	$ (19.82)	$ (1.11)	$ (32.09)
Weighted-average shares outstanding (basic and diluted)	15,399,018	349,170	15,385,009	347,831
Other comprehensive loss:
Unrealized loss on investments	(8)		(5)
Total comprehensive loss	$ (9,246)	$ (6,921)	$ (17,117)	$ (11,160)