Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net loss	$ (112,673)	$ (133,204)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation	2,136	2,266
Net amortization (accretion) on available-for-sale securities	(5,340)	(533)
Change in accrued interest on available-for-sale securities	493	1,025
Stock-based compensation expense	24,982	31,145
Non-cash lease expense	2,780	2,197
Impairment of operating lease right of use asset and leasehold improvements	2,915	0
Loss from write down of held for sale assets	249	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	616	1,605
Other noncurrent assets	590	(1,055)
Accounts payable	(4,148)	4,025
Accrued expenses	(2,032)	4,130
Right-of-use operating assets and liabilities, net	(2,819)	(2,671)
Deferred revenue	13,711	0
Current portion of other liabilities and Other noncurrent liabilities	(42)	144
Net cash used in operating activities	(78,582)	(90,926)
Cash flows from investing activities:
Purchase of property and equipment	(679)	(577)
Purchase of marketable securities	(212,957)	(367,124)
Maturities of marketable securities	280,004	334,979
Proceeds from sale of marketable securities	0	500
Net cash provided by (used in) investing activities	66,368	(32,222)
Cash flows from financing activities:
Proceeds from issuance of common stock upon exercise of stock options	29	471
Proceeds from issuance of common stock under the employee stock purchase plan	538	380
Net cash provided by financing activities	567	851
Net decrease in cash and cash equivalents	(11,647)	(122,297)
Cash, cash equivalents and restricted cash at beginning of period	77,999	200,296
Cash, cash equivalents and restricted cash at end of period	66,352	77,999
Cash and cash equivalents at end of period	64,326	75,973
Restricted cash at end of period	2,026	2,026
Cash, cash equivalents and restricted cash at end of period	66,352	77,999
Supplemental disclosures of non-cash activities:
Property and equipment additions included in accounts payable and accrued expenses	$ 4	$ 20