Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities
Net loss	$ (304,888)	$ (508,783)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	45,072	60,422
Premium on marketable securities	(186)	(71)
Amortization of discount on marketable securities	(5,538)	(12,521)
Depreciation expense	902	984
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	12,195	16,121
Collaboration receivable - related party	68,138	(8,853)
Other long-term assets	2,873	(1,823)
Right-of-use operating asset	4,679	4,506
Operating lease liabilities, current	(5,082)	(676)
Operating lease liabilities, non-current	149	(4,491)
Accounts payable	(3,192)	(7,677)
Accrued expenses and other liabilities	(15,756)	41,796
Net cash used in operating activities	(200,634)	(421,066)
Cash flows from investing activities
Proceeds from sales and maturities of marketable securities	582,357	861,231
Purchases of marketable securities	(362,253)	(459,714)
Purchases of property and equipment	0	(665)
Net cash provided by investing activities	220,104	400,852
Cash flows from financing activities
Proceeds from stock option exercises and employee stock purchase plan issuances	3,020	6,930
Payments of offering costs	(117)	0
Proceeds from public offerings of common stock, net of commissions and underwriting discounts	8,164	0
Payment of employee tax obligations related to vesting of restricted stock units	(402)	(641)
Net cash provided by financing activities	10,665	6,289
Net increase (decrease) in cash, cash equivalents and restricted cash	30,135	(13,925)
Cash, cash equivalents and restricted cash at beginning of period	72,324	163,969
Cash, cash equivalents and restricted cash at end of period	102,459	150,044
Supplemental disclosure of non-cash operating activities
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 11,472	$ 0