Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating expenses:
Research and development	$ 7,541	$ 12,157	$ 26,441	$ 29,063
General and administrative	4,184	4,840	12,928	13,036
Total operating expenses	11,725	16,997	39,369	42,099
Loss from operations	(11,725)	(16,997)	(39,369)	(42,099)
Other income (expense):
Change in fair value of preferred stock warrant liability	0	0	0	(51)
Interest income (expense), net	(712)	(307)	(1,969)	(1,174)
Total other income (expense), net	(712)	(307)	(1,969)	(1,225)
Net loss	$ (12,437)	$ (17,304)	$ (41,338)	$ (43,324)
Net loss per basic and diluted (USD per share)	$ (0.34)	$ (0.75)	$ (1.39)	$ (3.01)
Weighted average common shares outstanding, basic and diluted (in shares)	36,942,475	23,083,367	29,804,034	14,430,397
Comprehensive loss:
Net loss	$ (12,437)	$ (17,304)	$ (41,338)	$ (43,324)
Other comprehensive income (loss):
Unrealized losses on marketable securities	(4)	0	(4)	0
Comprehensive loss	$ (12,441)	$ (17,304)	$ (41,342)	$ (43,324)