CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Revenue	$ 966	$ 1,528	$ 3,057	$ 3,740
Operating expenses:
Research and development	15,725	12,912	42,686	34,581
General and administrative	3,774	3,197	11,546	9,288
Total operating expenses	19,499	16,109	54,232	43,869
Loss from operations	(18,533)	(14,581)	(51,175)	(40,129)
Other income (expense), net	(118)	237	(100)	763
Net loss before taxes	(18,651)	(14,344)	(51,275)	(39,366)
Provision for income taxes		287		791
Net loss	(18,651)	(14,631)	(51,275)	(40,157)
Other comprehensive income (loss):
Foreign currency translation adjustment	173	(70)	281	(65)
Unrealized gain (loss) on marketable securities	9	(33)	(59)	119
Total comprehensive loss	$ (18,469)	$ (14,734)	$ (51,053)	$ (40,103)
Net loss per share, basic and diluted	$ (0.63)	$ (0.60)	$ (1.92)	$ (1.67)
Weighted average number of shares used in computing net loss per share, basic and diluted	29,491,857	24,449,115	26,663,209	23,989,926