CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue:
Collaboration revenue	$ 0	$ 277	$ 0	$ 506
License revenue	0	0	425	0
Total revenue	0	277	425	506
Operating expenses:
Research and development	2,909	3,298	5,783	7,930
General and administrative	2,241	3,471	4,454	5,618
Loss from change in fair value of contingent consideration	2,200	0	3,700	0
Total operating expenses	7,350	6,769	13,937	13,548
Loss from operations	(7,350)	(6,492)	(13,512)	(13,042)
Other income (expense):
Other income, net	34	1	135	139
Loss on extinguishment of debt	0	0	0	(915)
Interest expense	0	0	0	(247)
Total other income (expense), net	34	1	135	(1,023)
Net loss and comprehensive loss	$ (7,316)	$ (6,491)	$ (13,377)	$ (14,065)
Net loss per share — basic and diluted (in dollars per share)	$ (0.30)	$ (0.33)	$ (0.54)	$ (0.71)
Weighted-average number of common shares used in net loss per share — basic and diluted (in shares)	24,685	19,874	24,648	19,756