Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating expenses:
Research and development	$ 8,334	$ 8,008
General and administrative	3,420	3,146
Total operating expenses	11,754	11,154
Loss from operations	(11,754)	(11,154)
Other income	272	96
Loss before provision for income taxes	(11,482)	(11,058)
Provision for income taxes	43	34
Net loss	$ (11,525)	$ (11,092)
Net loss per common share, basic and diluted	$ (0.19)	$ (0.26)
Weighted-average shares used in computing net loss per common share, basic and diluted	59,722,743	42,596,980