Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Collaboration revenue	$ 11	$ 11	$ 32	$ 817
Operating expenses:
Research and development	35,275	16,546	94,645	44,179
General and administrative	10,124	5,881	26,214	15,988
Total operating expenses	45,399	22,427	120,859	60,167
Other income (expense):
Interest income	15	19	36	414
Interest expense	(98)	(92)	(286)	(267)
Total other income (expense), net	(83)	(73)	(250)	147
Net loss	(45,471)	(22,489)	(121,077)	(59,203)
Other comprehensive loss
Unrealized gain (loss) on marketable securities	0	(2)	0	(25)
Comprehensive loss	(45,471)	(22,491)	(121,077)	(59,228)
Net loss attributable to common stockholders - basic	(45,471)	(22,489)	(121,077)	(59,203)
Net loss attributable to common stockholders - diluted	$ (45,471)	$ (22,489)	$ (121,077)	$ (59,203)
Net loss per share attributable to common stockholders - basic (in dollars per share)	$ (0.63)	$ (0.33)	$ (1.73)	$ (1.00)
Net loss per share attributable to common stockholders - diluted (in dollars per share)	$ (0.63)	$ (0.33)	$ (1.73)	$ (1.00)
Weighted-average number of shares of common stock used in net loss per share attributable to common stockholders - basic (in shares)	71,753,004	68,419,192	70,129,236	59,086,202
Weighted-average number of shares of common stock used in net loss per share attributable to common stockholders - diluted (in shares)	71,753,004	68,419,192	70,129,236	59,086,202