Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Revenue from collaboration agreements	$ 2,664	$ 13,834	$ 6,423	$ 21,488
Operating expenses:
Research and development	29,926	31,323	58,968	57,526
General and administrative	10,306	9,895	21,251	22,715
Total operating expenses	40,232	41,218	80,219	80,241
Loss from operations	(37,568)	(27,384)	(73,796)	(58,753)
Other income (expense), net:
Interest expense and amortization of long-term debt − related party	(600)	(534)	(1,206)	(1,061)
Interest and other income, net	2,246	506	4,300	782
Total other income (expense), net	1,646	(28)	3,094	(279)
Net loss	$ (35,922)	$ (27,412)	$ (70,702)	$ (59,032)
Net loss per share − basic (in dollars per share)	$ (0.73)	$ (0.56)	$ (1.44)	$ (1.21)
Net loss per share − diluted (in dollars per share)	$ (0.73)	$ (0.56)	$ (1.44)	$ (1.21)
Weighted-average number of shares used in computed net loss per share − basic	49,063,631	48,823,698	49,048,062	48,779,508
Weighted-average number of shares used in computed net loss per share − diluted	49,063,631	48,823,698	49,048,062	48,779,508
Other comprehensive income (loss)
Unrealized gain (loss) on marketable securities	$ 696	$ (931)	$ 2,363	$ (3,806)
Comprehensive loss	$ (35,226)	$ (28,343)	$ (68,339)	$ (62,838)
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]			Collaborative Arrangement [Member]	Collaborative Arrangement [Member]