Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue
Total revenue	$ 3,789	$ 0	$ 4,045	$ 0
Operating expenses
Research and development	8,120	2,522	14,004	6,014
General and administrative	3,080	3,201	5,460	7,151
Loss on impairment of long-lived assets	0	0	0	2,870
Total operating expenses	11,200	5,723	19,464	16,035
Loss from operations	(7,411)	(5,723)	(15,419)	(16,035)
Interest income	11	26	20	243
Other income (expense), net	295	656	290	(45)
Net loss	$ (7,105)	$ (5,041)	$ (15,109)	$ (15,837)
Net loss per share - basic and diluted (in dollars per share)	$ (0.35)	$ (0.32)	$ (0.78)	$ (1.02)
Weighted-average common shares used to compute basic and diluted net loss per share (in shares)	20,414	15,902	19,247	15,457
Collaborative Arrangement [Member]
Revenue
Total revenue	$ 3,789	$ 0	$ 4,045	$ 0