Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net loss	$ (212,220)	$ (173,995)	$ (118,009)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,101	1,387	639
Stock-based compensation expense	38,222	27,139	17,056
Amortization of premiums and discounts on marketable securities, net	(11,274)	(615)	179
Noncash operating lease costs	2,978	2,749	695
Other non-cash adjustments	0	0	(16)
Changes in operating assets and liabilities:
Prepaid and other assets	(3,444)	(6,616)	(2,510)
Accounts payable and accrued liabilities	1,769	18,315	6,043
Accrued compensation	3,145	2,250	5,788
Operating lease liabilities	(3,328)	(1,762)	(234)
Deferred revenue	62,987	(5,120)	(4,444)
Net cash used in operating activities	(119,064)	(136,268)	(94,813)
Cash flows from investing activities
Purchases of marketable securities	(461,002)	(355,837)	(85,357)
Maturities of marketable securities	335,160	168,705	6,580
Purchases of property and equipment	(4,228)	(2,823)	(3,740)
Net cash used in investing activities	(130,070)	(189,955)	(82,517)
Cash flows from financing activities
Proceeds from issuance of common stock in public offerings, net of issuance costs	60,547	344,779	174,677
Proceeds from issuance of common stock in a private placement, net of issuance costs and allocation to deferred revenues (Note 5)	31,190	0	0
Proceeds from the issuance of common stock under employee incentive equity plans	2,127	1,392	1,639
Net cash provided by financing activities	93,864	346,171	176,316
Net (decrease) increase in cash, cash equivalents and restricted cash	(155,270)	19,948	(1,014)
Cash, cash equivalents and restricted cash at beginning of period	340,647	320,699	321,713
Cash, cash equivalents and restricted cash at end of period	185,377	340,647	320,699
Supplemental schedule of noncash investing and financing activities:
Right-of-use assets obtained in exchange for operating lease liabilities	$ 1,741	$ 0	$ 12,074