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	$ (146,828)	$ (122,055)
Adjustments to reconcile net loss to net cash (used in) operating activities:
Stock-based compensation expense	20,038	18,553
Premium on marketable securities	(29)	(1,189)
Amortization of premium (discount) on marketable securities	(3,179)	3,533
Depreciation expense	323	275
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(8,024)	2,635
Collaboration receivable - related party	(1,342)	(1,291)
Other long-term assets	515	(340)
Right-of-use operating asset	1,470	1,350
Operating lease liabilities, current	41	55
Operating lease liabilities, non-current	(1,728)	(1,568)
Accounts payable	(6,550)	(3,251)
Accrued expenses and other liabilities	(8,389)	(4,507)
Net cash used in operating activities	(153,682)	(107,800)
Cash flows from investing activities
Proceeds from sales and maturities of marketable securities	351,982	292,539
Purchases of marketable securities	(156,890)	(301,928)
Purchases of property and equipment	(225)	(169)
Net cash provided by (used in) investing activities	194,867	(9,558)
Cash flows from financing activities
Proceeds from stock option exercises and employee stock purchase plan issuances	3,301	1,799
Payment of employee tax obligations related to vesting of restricted stock units	(629)
Net cash provided by financing activities	2,672	1,799
Net increase (decrease) in cash, cash equivalents and restricted cash	43,857	(115,559)
Cash, cash equivalents and restricted cash at beginning of period	163,969	295,502
Cash, cash equivalents and restricted cash at end of period	$ 207,826	$ 179,943