Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net loss		$ (71,174)	$ (56,624)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense		6,850	5,079
Depreciation and amortization expense		1,400	1,570
Non-cash operating lease cost		2,070	1,058
Net (accretion) amortization of (discounts) premiums on investments		(187)	313
Amortization of debt issuance costs		187	133
Collaboration (profit) loss sharing - related party		3,607	(976)
Changes in operating assets and liabilities:
Prepaid expenses and other current and other non-current assets		3,044	(3,841)
Deferred revenue - related party		522	(1,493)
Accounts payable		(3,806)	(6,464)
Operating lease liabilities		(67)	(1,507)
Accrued expenses and other current and long-term liabilities (3)	[1]	(19,030)	(3,693)
Net cash used in operating activities		(76,584)	(66,445)
Cash flows from investing activities:
Purchases of property and equipment		(4,068)	(2,950)
Purchases of investments		(4,426)	(28,156)
Sales and maturities of investments		11,233	44,078
Net cash provided by investing activities		2,739	12,972
Cash flows from financing activities:
Proceeds from exercise of stock options		188	257
Proceeds from issuance of common stock from at the market equity offering		4,239	0
Issuance of common stock under ESPP		1,229	892
Proceeds from issuance of debt, net of issuance costs		0	27,606
Repayment of notes payable		0	(1,907)
Net cash provided by financing activities		5,656	26,848
Net decrease in cash, cash equivalents, and restricted cash		(68,189)	(26,625)
Cash, cash equivalents and restricted cash at beginning of period		171,215	188,002
Cash, cash equivalents and restricted cash at end of period		103,026	161,377
Supplemental disclosure of cash flow information:
Cash paid for interest		1,737	558
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases included in accounts payable and accrued expenses		928	622
Prepaid rent reclassified to right-of-use assets		0	4,962
Lease liability arising from obtaining right-of-use assets		$ 0	$ 4,370

[1] Includes related party amounts of $(9,812) and $(1,107) at March 31, 2023 and March 31, 2022, respectively (see Note 11)