Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net loss	$ (146,962)	$ (154,808)	$ (100,217)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	43,118	35,480	24,972
Depreciation and amortization	3,565	2,977	2,397
Premiums and discounts on available for sale marketable securities	(5,229)	889	5,807
Loss on disposal of property and equipment	0	0	18
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,961)	(992)	(4,016)
Accounts receivable due from related party	(15,000)	0	577
Contract asset-due from related party	(1,226)	(2,401)	721
Accounts payable	2,038	253	54
Accrued expenses and other current liabilities	3,180	4,519	12,599
Deferred revenue	(8,609)	(37,774)	(69,356)
Operating lease right-of-use assets	4,797	517	419
Operating lease liabilities	18,582	(1,004)	(1,015)
Other non-current assets	909	(998)	(1,992)
Other non-current liabilities	(28)	257	86
Net cash (used in) provided by operating activities	(102,826)	(153,085)	(128,946)
Investing activities
Purchase of property and equipment, net	(34,480)	(2,836)	(1,597)
Purchase of marketable securities	(189,151)	(445,972)	(456,404)
Maturities of marketable securities	363,517	469,327	358,166
Net cash provided by (used in) investing activities	139,886	20,519	(99,835)
Financing activities
Proceeds from issuance of common stock and accompanying pre-funded warrants from private placement, net of issuance costs	0	149,825	0
Proceeds from stock option exercises	2,860	3,154	7,632
Proceeds from employee stock purchase plan	1,408	1,150	788
Payments of offering costs in connection with initial public offering	0	0	(397)
Payments on financing leases	(76)	(1,130)	(849)
Proceeds from follow-on public offering, net of underwriting discounts and offering costs	0	0	240,760
Proceeds from concurrent private placement	0	0	2,346
Net cash provided by financing activities	4,192	152,999	250,280
Net increase (decrease) in cash, cash equivalents and restricted cash	41,252	20,433	21,499
Cash, cash equivalents and restricted cash at beginning of period	74,525	54,092	32,593
Cash, cash equivalents and restricted cash at end of period	115,777	74,525	54,092
Supplemental disclosure of cash flow activities
Cash paid for interest	162	179	158
Supplemental disclosure of noncash investing and financing activities
Purchases of property and equipment through finance and lease liabilities	0	1,506	1,918
Property and equipment purchases included in accounts payable and accrued expenses	4,016	87	42
Supplemental disclosure of noncash operating activities
Reduction of right-of-use asset and liability due to lease modification	48,833	0	0
Cash and cash equivalents	109,966	68,395	47,976
Restricted cash	5,811	6,130	6,116
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total	$ 115,777	$ 74,525	$ 54,092