Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Revenue from collaboration agreements	$ 13,834	$ 9,781	$ 21,488	$ 17,207
Operating expenses:
Research and development	31,323	23,286	57,526	43,812
General and administrative	9,895	8,611	22,715	16,020
Total operating expenses	41,218	31,897	80,241	59,832
Loss from operations	(27,384)	(22,116)	(58,753)	(42,625)
Other (expense) income, net:
Interest expense and amortization of long-term debt − related party	(534)	(533)	(1,061)	(1,067)
Interest and other income, net	506	69	782	141
Total other income (expense), net	(28)	(464)	(279)	(926)
Net loss	$ (27,412)	$ (22,580)	$ (59,032)	$ (43,551)
Net loss per share attributable to common stockholders − basic (in dollars per share)	$ (0.56)	$ (0.51)	$ (1.21)	$ (1.00)
Net loss per share attributable to common stockholders − diluted (in dollars per share)	$ (0.56)	$ (0.51)	$ (1.21)	$ (1.00)
Weighted-average number of shares used in computed net loss per share − basic	48,823,698	43,855,420	48,779,508	43,472,327
Weighted-average number of shares used in computed net loss per share − diluted	48,823,698	43,855,420	48,779,508	43,472,327
Other comprehensive income (loss)
Unrealized gain (loss) on marketable securities	$ (931)	$ 25	$ (3,806)	$ (82)
Comprehensive loss	$ (28,343)	$ (22,555)	$ (62,838)	$ (43,633)