Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating expenses:
Research and development	$ 11,083	$ 12,557	$ 10,058
General and administrative	13,510	11,506	12,340
Total operating expenses	24,593	24,063	22,398
Operating loss	(24,593)	(24,063)	(22,398)
Other income (expense):
Interest income	189	187	60
Interest expense	(74)	(155)	(172)
Derivatives gain (loss)	(2,267)	593	(10,804)
Other income (expense), net	(2,152)	625	(10,916)
Net loss	$ (26,745)	$ (23,438)	$ (33,314)
Net loss per share, basic and diluted (in dollars per share)	$ (0.81)	$ (0.76)	$ (1.26)
Weighted average number of common shares outstanding, basic and diluted	32,950,068	31,025,585	26,461,374
Other comprehensive loss:
Net loss	$ (26,745)	$ (23,438)	$ (33,314)
Other comprehensive loss:
Comprehensive loss	$ (26,745)	$ (23,438)	$ (33,314)