CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Total revenues	$ 0	$ 6
Operating expenses:
Research and development	3,320	3,119
General and administrative	2,478	2,422
Total operating expenses	5,798	5,541
Loss from operations	(5,798)	(5,535)
Other income (expense):
Interest and other income	1	79
Interest and other expense	(216)	(489)
Loss before income taxes	(6,013)	(5,945)
Income tax benefit	0	8
Net loss and comprehensive loss	$ (6,013)	$ (5,937)
Net loss per share, basic and diluted (in dollars per share)	$ (0.08)	$ (0.25)
Weighted average shares used to compute basic and diluted net loss per share (in shares)	71,290,918	24,064,373
Revenue, Product and Service [Extensible List]	us-gaap:RevenueUnderCollaborationsMember	us-gaap:RevenueUnderCollaborationsMember