Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Cash flow from operating activities
Net loss	$ (353)	$ (283)	$ (307)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	60	76	73
Depreciation and amortization	10	10	8
Noncash lease expense	7	7	8
Impairment on right-of use assets	0	20	0
Amortization of discounts on marketable securities	(13)	(25)	(19)
Other items, net	1	3	2
Changes in operating assets and liabilities:
Receivable from collaboration partners ($6, $14 and $19 from a related party)	9	28	15
Other assets ($—, $6 and ($4) from a related party)	5	22	(14)
Accounts payable ($24, $—, and $— to a related party)	24	3	(1)
Deferred revenue (($240), ($56) and ($77) to a related party)	(240)	(56)	(68)
Other liabilities	8	25	(3)
Net cash used in operating activities	(482)	(170)	(306)
Cash flow from investing activities
Purchases of marketable securities	(1,076)	(1,043)	(788)
Proceeds from maturities of marketable securities	1,073	929	982
Proceeds from sales of marketable securities	71	36	24
Purchases of property and equipment	(2)	(6)	(24)
Net cash provided by (used in) investing activities	66	(84)	194
Cash flow from financing activities
Proceeds from issuance of common stock ($14, $228 and $20 from a related party), net	429	228	25
Proceeds from debt issuances, net	49	47	0
Proceeds from issuance of common stock pursuant to equity award plans	10	9	8
Payments of employee taxes related to net settlement of equity awards	0	(7)	0
Net cash provided by financing activities	488	277	33
Net increase (decrease) in cash, cash equivalents and restricted cash	72	23	(79)
Cash, cash equivalents and restricted cash at beginning of period	153	130	209
Cash, cash equivalents and restricted cash at end of period	225	153	130
Supplemental disclosure of cash flow information
Income taxes paid	0	0	5
Interest paid	7	1	0
Non-cash investing and financing activities:
Unpaid portion of property and equipment purchases included in Accounts payable and Other current liabilities	$ 0	$ 0	$ 2