Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Cash flow from operating activities
Net loss	$ (112)	$ (4)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	16	20
Depreciation and amortization	3	3
Noncash lease expense	2	2
Impairment of long-lived assets	0	20
Amortization of discounts on marketable securities	(4)	(6)
Changes in operating assets and liabilities:
Receivable from collaboration partners ($2 and ($1) from a related party)	5	13
Other assets ($— and $6 from a related party)	0	5
Accounts payable	3	(1)
Deferred revenue (($28) and ($54) to a related party)	(28)	(42)
Other liabilities	(17)	(12)
Net cash used in operating activities	(132)	(2)
Cash flow from investing activities
Purchases of marketable securities	(353)	(387)
Proceeds from maturities of marketable securities	360	222
Proceeds from sales of marketable securities	26	0
Purchases of property and equipment	(1)	(4)
Net cash provided by (used in) investing activities	32	(169)
Cash flow from financing activities
Proceeds from issuance of common stock ($14 and $228 from a related party)	142	228
Proceeds from issuance of common stock pursuant to equity award plans	0	1
Net cash provided by financing activities	142	229
Net increase in cash, cash equivalents and restricted cash	42	58
Cash, cash equivalents and restricted cash at beginning of period	153	130
Cash, cash equivalents and restricted cash at end of period	195	188
Non-cash investing and financing activities:
Unpaid portion of property and equipment purchases included in Accounts payable and Other current liabilities	$ 0	$ 1