CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Total revenues	$ 153	$ 668	$ 4,317	$ 3,633
Operating expenses:
Research and development	13,557	10,708	38,633	32,109
General and administrative	5,821	3,640	14,247	10,833
Intangible asset impairment	3,500		3,500	3,500
(Gain) loss on fair value remeasurement of contingent consideration	(1,901)	662	(1,160)	(4,236)
Total operating expenses	20,977	15,010	55,220	42,206
Operating loss	(20,824)	(14,342)	(50,903)	(38,573)
Investment and other income, net	145	118	313	465
Net loss before income tax benefit	(20,679)	(14,224)	(50,590)	(38,108)
Income tax benefit	227		227	228
Net loss	$ (20,452)	$ (14,224)	$ (50,363)	$ (37,880)
Basic and diluted net loss per common share	$ (0.45)	$ (0.36)	$ (1.21)	$ (1.44)
Shares used in calculating basic and diluted net loss per share	45,453	39,278	41,582	26,303
Comprehensive loss:
Net loss	$ (20,452)	$ (14,224)	$ (50,363)	$ (37,880)
Other comprehensive income (loss):
Unrealized (loss) gain on marketable securities	(44)	14	(41)	(11)
Comprehensive loss	(20,496)	(14,210)	(50,404)	(37,891)
Product development and licensing agreements
Revenues:
Total revenues		12	29	2,297
Contracts and grants
Revenues:
Total revenues	$ 153	$ 656	$ 4,288	$ 1,336