Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Research and development, milestone, grant and other revenues, net	$ 8,726	$ 5,862	$ 16,991	$ 6,680
Total revenues	10,641	6,180	22,124	13,386
Operating expenses:
Research and development	21,391	24,947	65,858	64,045
General and administrative	7,164	9,657	23,724	26,210
Total operating expenses	28,555	34,604	89,582	90,255
Operating loss	(17,914)	(28,424)	(67,458)	(76,869)
Interest expense	(867)	(806)	(2,628)	(2,346)
Non-cash interest expense on liability related to sale of future royalties	(4,559)	(3,906)	(13,026)	(9,918)
Interest and other income, net	1,323	779	3,291	1,828
Net loss	$ (22,017)	$ (32,357)	$ (79,821)	$ (87,305)
Net loss per share — basic and diluted	$ (0.40)	$ (0.60)	$ (1.47)	$ (1.82)
Weighted-average shares in net loss per share — basic and diluted	54,626	53,719	54,329	47,879
Other comprehensive income:
Unrealized gain on available-for-sale securities, net	$ 3	$ 512	$ 104	$ 289
Comprehensive loss	(22,014)	(31,845)	(79,717)	(87,016)
License Revenues [Member]
Revenues:
License revenues	$ 1,915	$ 318	$ 5,133	$ 6,706