CONDENSED CONSOLIDATED 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
Expenses
Research and development	$ 14,563	$ 6,886	$ 34,046	$ 18,995
General and administrative	4,161	3,662	12,180	9,333
Restructuring costs	0	0	0	334
Total operating expenses	18,724	10,548	46,226	28,662
Loss from operations	(18,724)	(10,548)	(46,226)	(28,662)
Other income (expense), net	(17)	24	99	(105)
Change in fair value of warrant liability	0	1,907	0	(4,544)
Net loss	(18,741)	(8,617)	(46,127)	(33,311)
Unrealized gain (loss) on available-for-sale investments	6	(12)	2	22
Comprehensive loss	$ (18,735)	$ (8,629)	$ (46,125)	$ (33,289)
Basic net loss per share	$ (1.11)	$ (0.64)	$ (2.86)	$ (2.47)
Diluted net loss per share	$ (1.11)	$ (0.72)	$ (2.86)	$ (2.47)
Weighted average number of shares used in computing net loss per share, basic	16,841,954	13,527,113	16,103,326	13,478,735
Weighted average number of shares used in computing net loss per share, diluted	16,841,954	14,717,253	16,103,326	13,478,735