Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Income Statement [Abstract]
Revenue from collaboration agreements	$ 3,759	$ 7,654
Operating expenses:
Research and development	29,042	26,203
General and administrative	10,945	12,820
Total operating expenses	39,987	39,023
Loss from operations	(36,228)	(31,369)
Other income (expense), net:
Interest expense and amortization of long-term debt − related party	(606)	(527)
Interest and other income, net	2,054	276
Total other income (expense), net	1,448	(251)
Net loss	$ (34,780)	$ (31,620)
Net loss per share − basic (in dollars per share)	$ (0.71)	$ (0.65)
Net loss per share − diluted (in dollars per share)	$ (0.71)	$ (0.65)
Weighted-average number of shares used in computed net loss per share − basic	49,032,319	48,734,827
Weighted-average number of shares used in computed net loss per share − diluted	49,032,319	48,734,827
Other comprehensive income (loss)
Unrealized gain (loss) on marketable securities	$ 1,667	$ (2,875)
Comprehensive loss	$ (33,113)	$ (34,495)
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	Collaborative Arrangement [Member]	Collaborative Arrangement [Member]