Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net loss	$ (107,494)	$ (71,317)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	17,121	13,799
Vesting of common stock warrants in return for services	87	87
Change in fair value of derivative liability	(2)	92
Depreciation and amortization	2,403	1,523
Amortization of right-of-use assets	1,477	1,497
Net amortization (accretion) of premium (discount) on marketable securities	1,059	719
Changes in operating assets and liabilities
Accounts receivable	47	1,439
Prepaid expenses and other current assets	1,235	(4,225)
Other assets	(11)	0
Accounts payable	(1,638)	2,285
Accrued and other liabilities	2,485	689
Deferred revenue	(3,130)	(14,722)
Operating lease liabilities	(324)	(1,000)
Net cash used in operating activities	(86,685)	(69,134)
Cash flows from investing activities
Acquisition of property and equipment	(11,536)	(9,110)
Purchase of marketable securities	(153,313)	(168,570)
Maturities of marketable securities	147,799	5,000
Net cash used in investing activities	(17,050)	(172,680)
Cash flows from financing activities
Issuance of common stock upon offerings, net of issuance costs	0	114,296
Issuance of common stock upon exercise of stock options and warrants	2,730	3,360
Payment of offering costs	(468)	0
Net cash provided by financing activities	3,085	118,089
Net decrease in cash and cash equivalents	(100,650)	(123,725)
Cash and cash equivalents, beginning of period	153,001	276,726
Cash and cash equivalents, end of period	52,351	153,001
Supplemental disclosures of noncash investing and financing information
Purchases of property and equipment in accounts payable and accrued and other liabilities	937	2,199
Receivable for common stock issued upon exercise of stock options	264	545
Unpaid offering costs	0	152
Decrease in right-of-use assets due to reduction in operating lease liabilities upon modification	0	(478)
Issuance of common stock warrant to settle liability	0	1,146
Employee Stock Purchase Plan
Cash flows from financing activities
Issuance of common stock upon offerings, net of issuance costs	$ 823	$ 433