Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating expenses:
Research and development	$ 7,405	$ 12,323	$ 22,607	$ 28,074
General and administrative	2,778	2,960	9,207	10,768
Total operating expenses	10,183	15,283	31,814	38,842
Loss from operations	(10,183)	(15,283)	(31,814)	(38,842)
Other income	225	88	506	259
Loss before provision for income taxes	(9,958)	(15,195)	(31,308)	(38,583)
Provision for income taxes	37	14	108	36
Net loss	$ (9,995)	$ (15,209)	$ (31,416)	$ (38,619)
Net loss per common share, basic and diluted	$ (0.19)	$ (0.50)	$ (0.64)	$ (1.28)
Weighted-average shares used in computing net loss per common share, basic and diluted	52,268,443	30,331,616	49,080,049	30,198,134