Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue
Total revenue	$ 2,412	$ 0	$ 6,457	$ 0
Operating expenses
Research and development	11,343	5,070	25,347	11,085
General and administrative	2,643	2,715	8,102	9,866
Loss on impairment of long-lived assets		2,914	0	5,784
Total operating expenses	13,986	10,699	33,449	26,735
Loss from operations	(11,574)	(10,699)	(26,992)	(26,735)
Interest income	9	8	29	251
Other income (expense), net	479	31	768	(13)
Net loss	$ (11,086)	$ (10,660)	$ (26,195)	$ (26,497)
Net loss per share - basic and diluted (in dollars per share)	$ (0.53)	$ (0.66)	$ (1.33)	$ (1.69)
Weighted-average common shares used to compute basic and diluted net loss per share (in shares)	20,763	16,055	19,758	15,658
Collaborative Arrangement [Member]
Revenue
Total revenue	$ 2,412	$ 0	$ 6,457	$ 0