CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues:
Total revenues	$ 3,480	$ 236	$ 4,165	$ 2,965
Operating expenses:
Research and development	12,356	9,705	25,076	21,400
General and administrative	4,306	3,528	8,426	7,194
Intangible asset impairment		3,500		3,500
Loss (gain) on fair value remeasurement of contingent consideration	258	(5,132)	741	(4,898)
Total operating expenses	16,920	11,601	34,243	27,196
Operating loss	(13,440)	(11,365)	(30,078)	(24,231)
Investment and other income, net	67	106	167	347
Net loss before income tax benefit	(13,373)	(11,259)	(29,911)	(23,884)
Income tax benefit		228		228
Net loss	$ (13,373)	$ (11,031)	$ (29,911)	$ (23,656)
Basic and diluted net loss per common share	$ (0.34)	$ (0.50)	$ (0.76)	$ (1.20)
Shares used in calculating basic and diluted net loss per share	39,616	22,082	39,615	19,744
Comprehensive loss:
Net loss	$ (13,373)	$ (11,031)	$ (29,911)	$ (23,656)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	5	(3)	3	(25)
Comprehensive loss	(13,368)	(11,034)	(29,908)	(23,681)
Product development and licensing agreements
Revenues:
Total revenues	26		29	2,285
Contracts and grants
Revenues:
Total revenues	$ 3,454	$ 236	$ 4,136	$ 680