CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE (LOSS) INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Collaboration revenue	$ 0	$ 406	$ 490
License revenue	425	29,575	500
Total revenue	425	29,981	990
Operating expenses:
Research and development	12,510	13,479	26,336
General and administrative	8,070	14,736	9,850
Loss (gain) from change in fair value of contingent consideration	9,100	(1,100)	0
Total operating expenses	29,680	27,115	36,186
(Loss) income from operations	(29,255)	2,866	(35,196)
Other income (expense):
Other income (expense), net	226	(723)	3,139
Interest expense	0	(247)	(1,395)
Total other income (expense), net	226	(970)	1,744
Net (loss) income before income taxes	(29,029)	1,896	(33,452)
Provision for income taxes	0	5	0
Net (loss) income and comprehensive (loss) income	$ (29,029)	$ 1,891	$ (33,452)
Net (loss) income per share applicable to common stockholders—basic (in dollars per share)	$ (1.11)	$ 0.09	$ (1.76)
Weighted-average number of common shares used in net (loss) income per share applicable to common stockholders—basic (in shares)	26,105	21,083	18,993
Net (loss) income per share applicable to common stockholders-diluted (in dollars per share)	$ (1.11)	$ 0.09	$ (1.76)
Weighted-average number of common shares used in net (loss) income per share applicable to common stockholders—diluted (in shares)	26,105	21,733	18,993