CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating expenses:
Research and development	$ 33,530	$ 14,363	$ 81,919	$ 35,230
General and administrative	14,952	13,191	42,254	27,311
Total operating expenses	48,482	27,554	124,173	62,541
Loss from operations	(48,482)	(27,554)	(124,173)	(62,541)
Other income (expense):
Change in fair value of preferred stock warrant liability		(426)		(2,187)
Interest expense	(835)	(87)	(1,957)	(259)
Interest income and other income, net	2,302	1,705	7,144	2,975
Total other income, net	1,467	1,192	5,187	529
Net loss	$ (47,015)	$ (26,362)	$ (118,986)	$ (62,012)
Net loss per share, basic and diluted	$ (0.59)	$ (0.42)	$ (1.52)	$ (2.33)
Weighted average common shares outstanding, basic and diluted	79,115,305	62,311,111	78,357,791	26,662,233
Comprehensive loss:
Net loss	$ (47,015)	$ (26,362)	$ (118,986)	$ (62,012)
Other comprehensive income (loss):
Unrealized gains (losses) on investments, net of tax of $0	(124)	8	195	(19)
Comprehensive loss	$ (47,139)	$ (26,354)	$ (118,791)	$ (62,031)