CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Total revenues	$ 132,299	$ 82,271	$ 53,446
Operating expenses:
Research and development	114,592	114,522	174,456
General and administrative	38,600	38,489	36,746
Restructuring charge	1,487	21,433	3,693
Total operating expenses	154,679	174,444	214,895
Loss from operations	(22,380)	(92,173)	(161,449)
Investment income, net	729	4,424	4,227
Non-cash interest expense on liability related to the sale of future royalties and convertible senior notes	(23,107)	(16,879)	(10,631)
Interest expense on convertible senior notes	(95)	(95)	(95)
Other income (expense), net	481	590	(895)
Net loss	$ (44,372)	$ (104,133)	$ (168,843)
Basic and diluted net loss per common share	$ (0.25)	$ (0.70)	$ (1.21)
Basic and diluted weighted average common shares outstanding	176,153	148,311	139,946
Total comprehensive loss	$ (44,372)	$ (104,133)	$ (168,843)
License and milestone fees
Revenues:
Total revenues	63,742	34,788	15,280
Non-cash royalty revenue related to the sale of future royalties
Revenues:
Total revenues	68,529	47,415	32,154
Research and development support
Revenues:
Total revenues	$ 28	$ 68	1,377
Clinical materials revenue
Revenues:
Total revenues			$ 4,635