CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues:
Total revenues	$ 0	$ 5,000	$ 0	$ 5,006
Operating expenses:
Research and development	5,915	4,036	13,385	11,396
General and administrative	2,504	2,059	7,471	6,736
Total operating expenses	8,419	6,095	20,856	18,132
Loss from operations	(8,419)	(1,095)	(20,856)	(13,126)
Other income (expense):
Interest and other income	1	38	823	127
Interest and other expense	(210)	(466)	(641)	(1,416)
Loss before income taxes	(8,628)	(1,523)	(20,674)	(14,415)
Income tax (expense) benefit	0	(1)	(1)	7
Net loss and comprehensive loss	$ (8,628)	$ (1,524)	$ (20,675)	$ (14,408)
Net loss per share, basic (in usd per share)	$ (0.10)	$ (0.04)	$ (0.26)	$ (0.47)
Net loss per share, diluted (in usd per share)	$ (0.10)	$ (0.04)	$ (0.26)	$ (0.47)
Weighted average shares used to compute basic net loss per share (in shares)	87,042,437	38,137,281	78,560,760	30,695,137
Weighted average shares used to compute diluted net loss per share (in shares)	87,042,437	38,137,281	78,560,760	30,695,137
Revenue, Product and Service [Extensible List]	Revenue Under Collaborations [Member]	Revenue Under Collaborations [Member]	Revenue Under Collaborations [Member]	Revenue Under Collaborations [Member]