CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
Research and development	$ 112,419	$ 51,769	$ 21,226
General and administrative	57,182	39,894	22,038
Total operating expenses	169,601	91,663	43,264
Loss from operations	(169,601)	(91,663)	(43,264)
Other income (expense):
Interest income	7,994	5,078	584
Interest expense	(2,590)	(464)	(309)
Change in fair value of preferred stock warrant liability		(2,187)	(785)
Other income (expense), net	739	41	(73)
Total other income (expense), net	6,143	2,468	(583)
Net loss	(163,458)	(89,195)	(43,847)
Accretion of Series A redeemable convertible preferred stock to redemption value			(656)
Net loss attributable to common stockholders	$ (163,458)	$ (89,195)	$ (44,503)
Net loss per share attributable to common stockholders, basic and diluted	$ (2.08)	$ (2.27)	$ (5.55)
Weighted average common shares outstanding, basic and diluted	78,688,878	39,285,468	8,023,785
Comprehensive loss:
Net loss	$ (163,458)	$ (89,195)	$ (43,847)
Other comprehensive income (loss):
Unrealized gains (losses) on investments, net of tax of $0	104	(29)
Comprehensive loss	$ (163,354)	$ (89,224)	$ (43,847)