Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating expenses:
Research and development	$ 7,194	$ 9,115	$ 15,202	$ 15,751
General and administrative	3,283	3,831	6,429	7,808
Total operating expenses	10,477	12,946	21,631	23,559
Loss from operations	(10,477)	(12,946)	(21,631)	(23,559)
Other income	185	88	281	171
Loss before provision for income taxes	(10,292)	(12,858)	(21,350)	(23,388)
Provision for income taxes	37	14	71	22
Net loss	$ (10,329)	$ (12,872)	$ (21,421)	$ (23,410)
Net loss per common share, basic and diluted	$ (0.20)	$ (0.43)	$ (0.45)	$ (0.78)
Weighted-average shares used in computing net loss per common share, basic and diluted	52,268,443	30,191,093	47,459,428	30,130,660