Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net loss	$ (400,666)	$ (541,489)	$ (532,784)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	54,504	73,367	61,602
Premium on marketable securities	(344)	(132)	(1,500)
Amortization of (discount) premium on marketable securities	(6,481)	(6,340)	5,853
Depreciation expense	1,031	1,393	1,122
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	14,076	19,001	(10,985)
Collaboration receivable - related party	73,875	(69,349)	4,846
Other long-term assets	3,720	(1,778)	(519)
Right-of-use operating asset	5,302	6,074	5,577
Operating lease liabilities, current	(3,847)	(2,478)	175
Operating lease liabilities, non-current	(1,079)	(4,491)	(6,473)
Accounts payable	2,381	(8,495)	8,433
Accrued expenses and other liabilities	(9,666)	(5,868)	4,617
Net cash used in operating activities	(267,194)	(540,585)	(460,036)
Cash flows from investing activities
Proceeds from sales and maturities of marketable securities	717,635	1,038,136	1,207,407
Purchases of marketable securities	(450,957)	(594,670)	(881,037)
Purchases of property and equipment	0	(553)	(937)
Net cash provided by investing activities	266,678	442,913	325,433
Cash flows from financing activities
Proceeds from stock option exercises and employee stock purchase plan issuances	3,019	6,930	3,113
Payments of offering costs	(117)	0	0
Proceeds from public offerings of common stock, net of commissions and underwriting discounts	8,164	0	0
Payment of employee tax obligations related to vesting of restricted stock units	(403)	(903)	(43)
Net cash provided by financing activities	10,663	6,027	3,070
Net increase (decrease) in cash, cash equivalents and restricted cash	10,147	(91,645)	(131,533)
Cash, cash equivalents and restricted cash at beginning of period	72,324	163,969	295,502
Cash, cash equivalents and restricted cash at end of period	82,471	72,324	163,969
Supplemental disclosure of non-cash operating activities
Right-of-use assets obtained in exchange for new operating lease liabilities	11,597	0	0
Purchases of property and equipment included in accounts payable	0	0	137
Reconciliation of cash, cash equivalents, and restricted cash reported in the consolidated balance sheets
Cash and cash equivalents	81,021	70,992	162,700
Restricted cash	1,450	1,332	1,269
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$ 82,471	$ 72,324	$ 163,969