Consolidated 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	$ (171,670)	$ (204,212)	$ (170,060)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,517	927	855
Net amortization of premiums and discounts on marketable securities	(4,569)	(1,462)	0
Stock-based compensation	21,136	21,522	18,409
Non-cash operating lease expense	2,780	2,777	1,829
Other non-cash items	687	763	723
Changes in operating assets and liabilities:
Accounts receivable	30,000	(30,000)	0
Prepaid expenses and other current assets	3,534	3,863	(2,734)
Other assets	0	0	(718)
Accounts payable	(6,080)	947	483
Accrued expenses	(20,935)	13,594	12,570
Operating lease liabilities	(3,143)	(2,539)	(1,827)
Deferred revenue	(22,139)	143,709	(43)
Other liabilities	0	748	525
Net cash used in operating activities	(168,882)	(49,363)	(139,988)
Cash flows from investing activities
Maturities of marketable securities	277,970	97,000	0
Purchase of marketable securities	(155,919)	(247,519)	0
Purchase of property and equipment	(2,168)	(2,197)	(648)
Net cash provided by (used in) investing activities	119,883	(152,716)	(648)
Cash flows from financing activities
Proceeds from exercise of stock options	427	1,331	1,837
Proceeds from purchases of common stock under ESPP	1,121	1,065	640
Payment of employee tax obligations related to vesting of restricted stock units	0	0	(259)
Proceeds from issuance of debt, net of issuance costs	(150)	0	24,042
Repayment of debt	0	0	(5,486)
Payments under finance lease obligations	(262)	(272)	(215)
Net cash provided by financing activities	94,675	153,017	63,646
Increase (decrease) in cash, cash equivalents and restricted cash	45,676	(49,062)	(76,990)
Cash, cash equivalents and restricted cash, beginning of period	129,363	178,425	255,415
Cash, cash equivalents and restricted cash, end of period	175,039	129,363	178,425
Supplemental disclosures of non-cash activities:
Purchases of property and equipment in accounts payable and accrued expenses	132	753	0
Debt financing costs in accrued expenses	0	150	0
Common stock issuance costs in accounts payable and accrued expenses	0	131	0
Cash paid for interest	3,380	2,463	429
Right-of-use assets obtained in exchange for operating lease liabilities	0	298	3,783
Right-of-use assets obtained in exchange for financing lease liabilities	0	0	609
At Market Equity Offering Program
Cash flows from financing activities
Net proceeds from at-the-market facilities	$ 93,539	$ 150,893	$ 43,087