Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 0	$ 0	$ 0
Operating expenses:
Research and development	59,208	41,340	27,899
General and administrative	23,761	18,623	7,828
Total operating expenses	82,969	59,963	35,727
Loss from operations	(82,969)	(59,963)	(35,727)
Interest and other income, net	6,200	2,448	236
Net loss	(76,769)	(57,515)	(35,491)
Accretion of redeemable convertible preferred stock to redemption value		(88)	(213)
Cumulative dividends on redeemable convertible preferred stock			(437)
Reversal of cumulative dividends on redeemable convertible preferred stock			634
Net loss attributable to common stockholders	$ (76,769)	$ (57,603)	$ (35,507)
Net loss per share attributable to common stockholders, basic and diluted	$ (2.07)	$ (3.13)	$ (19.12)
Weighted average common shares outstanding, basic and diluted	37,014,875	18,389,576	1,856,907
Comprehensive loss:
Net loss	$ (76,769)	$ (57,515)	$ (35,491)
Other comprehensive income (loss):
Unrealized gains (losses) on marketable securities	16	(8)
Total other comprehensive income (loss)	16	(8)
Total comprehensive loss	$ (76,753)	$ (57,523)	$ (35,491)