Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net loss	$ (28,323)	$ (27,808)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization expense	122	459
Gain on PPP Loan forgiveness	0	(662)
Stock-based compensation	2,177	2,923
Amortization of premiums and accretion of discounts on investments, net	(185)	0
Other	133	46
Change in operating assets and liabilities:
Contracts and other receivables	0	503
Prepaid materials	0	304
Prepaid expenses and other assets	(67)	(221)
Accounts payable	(110)	(250)
Accrued liabilities	140	240
Accrued research and development expenses	442	(287)
Accrued compensation	189	273
Operating lease right-of-use assets and liabilities, net	(64)	279
Other liabilities	20	73
Net cash used in operating activities	(25,526)	(24,128)
Investing activities
Payments to Acquire Short-Term Investments	(32,759)	0
Sales and maturities of short-term investments	18,000	0
Purchases of property and equipment	(361)	(251)
Net cash used in investing activities	(15,120)	(251)
Financing activities
Proceeds from issuance of securities through private placement, net of issuance costs	0	32,360
Proceeds from issuance of common stock, net	4,491	21,431
Proceeds from exercise of common stock options	0	26
Payments on financing leases	0	(80)
Net cash provided by financing activities	4,491	53,737
Net (decrease) increase in cash, cash equivalents and restricted cash	(36,155)	29,358
Cash, cash equivalents and restricted cash at beginning of period	60,445	31,087
Cash, cash equivalents and restricted cash at end of period	24,290	60,445
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	24,228	60,383
Restricted cash	62	62
Total cash, cash equivalents and restricted cash	24,290	60,445
Supplemental disclosure of cash flow information
Interest paid	(491)	(729)
Income taxes paid	(1)	(1)
Supplemental disclosure of non-cash investing and financing activities
Paycheck Protection Program loan forgiveness	0	662
Purchases of property and equipment included in accrued liabilities	$ 6	$ 0