CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities
Net loss	$ (18,638)	$ (12,711)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,401	3,251
Amortization of premiums (discounts) on marketable securities	76	(25)
Depreciation expense	196	48
Non cash interest expense	626	729
Reduction in operating lease right-of-use asset	125	113
Changes in operating assets and liabilities:
Prepaid expenses and other assets	1,048	218
Accounts payable	(131)	435
Unbilled receivable	(218)	0
Accrued expenses and other current liabilities	(880)	239
Deferred revenue	0	(500)
Operating lease liability	(126)	(83)
Net cash used in operating activities	(15,521)	(8,286)
Cash flows from investing activities
Sales and maturities of marketable securities	50,000	35,600
Purchases of marketable securities	(4,477)	(46,216)
Purchases of property and equipment	(159)	(607)
Deposits	(146)	(77)
Net cash provided by (used in) investing activities	45,218	(11,300)
Cash flows from financing activities
Proceeds from exercise of stock options	0	513
Proceeds from issuance of common stock, net of issuance costs	0	28,119
Proceeds from Debt, Net of Issuance Costs	0	4,975
Debt issuance costs	(17)	0
Repayment of financing lease	(2)	(1)
Net cash (used in) provided by financing activities	(19)	33,606
Net increase in cash, cash equivalents and restricted cash	29,678	14,020
Cash, cash equivalents and restricted cash at the beginning of the period	15,752	10,686
Cash, cash equivalents and restricted cash at the end of the period	45,430	24,706
Supplemental disclosure of noncash investing and financing activities:
Property and equipment purchases payable or accrued at period end	291	239
Right-of-use asset obtained in exchange for lease obligation	99	0
Change in unrealized gain on marketable securities	(35)	(2)
Cash paid for interest	$ 1,468	$ 1,376