Condensed Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net loss	$ (20,321)	$ (61,724)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities
Stock-based compensation expense	2,843	2,136
Depreciation and amortization	604	549
Non-cash lease expense	160	25
Net amortization of discounts on marketable securities	305	574
Changes in operating assets and liabilities
Prepaid expenses and other assets	(1,884)	(1,143)
Other assets	47	316
Accounts payable	946	1,070
Accrued liabilities	(1,645)	49,359
Deferred revenue	(5,906)	(9,007)
Operating lease liabilities	(387)	(232)
Net cash used in operating activities	(25,238)	(18,077)
Cash flows from investing activities
Purchases of property and equipment	597	45
Purchases of marketable securities	(10,505)	(82,956)
Maturities of marketable securities	40,367	43,101
Net cash provided by (used in) investing activities	30,459	(39,900)
Cash flows from financing activities
Proceeds from follow-on offering, net of issuance costs	0	107,581
Proceeds from issuance of common stock in connection with employee benefit plans	830	561
Net cash provided by financing activities	830	108,142
Net increase in cash, cash equivalents, and restricted cash	6,051	50,165
Cash, cash equivalents, and restricted cash at beginning of period	45,360	21,637
Cash, cash equivalents, and restricted cash at end of period	51,411	71,802
Supplemental disclosures of non-cash investing and financing information
Purchases of property and equipment included in accrued liabilities and accounts payable	675	0
Reclassification of employee stock liability to equity upon vesting	$ 3	$ 6