CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue:
Total revenue	$ 12,661	$ 12,506	$ 34,232	$ 37,953
Operating expenses:
Research and development	34,871	22,962	95,246	64,265
General and administrative	5,341	3,103	15,603	8,244
Total operating expenses	40,212	26,065	110,849	72,509
Loss from operations	(27,551)	(13,559)	(76,617)	(34,556)
Other income, net:
Interest income	347	766	1,986	1,571
Interest and other expense	(17)	(25)	(57)	(83)
Total other income, net	330	741	1,929	1,488
Loss before income taxes	(27,221)	(12,818)	(74,688)	(33,068)
Benefit from income taxes			733
Net loss	(27,221)	(12,818)	(73,955)	(33,068)
Redeemable convertible preferred stock dividends - undeclared and cumulative		(4,247)	(2,219)	(9,987)
Net loss attributable to common stockholders	$ (27,221)	$ (17,065)	$ (76,174)	$ (43,055)
Net loss per share attributable to common stockholders - basic and diluted	$ (0.42)	$ (6.08)	$ (1.49)	$ (15.81)
Weighted-average common shares used to compute net loss per share, basic and diluted	64,892,868	2,806,470	51,031,003	2,723,541
Collaboration Revenue, Related Party
Revenue:
Total revenue	$ 12,661	$ 12,506	$ 34,232	$ 37,953