CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities
Net loss	$ (6,719)	$ (6,013)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization expense	26	335
Stock-based compensation	1,000	691
Other	38	10
Change in operating assets and liabilities:
Contracts and other receivables	(8)	432
Prepaid expenses and other assets	681	356
Accounts payable	340	275
Accrued liabilities	(26)	14
Accrued research and development expenses	(202)	(371)
Accrued compensation	(1,159)	(941)
Operating lease right-of-use assets and liabilities, net	(12)	90
Other liabilities	(340)	(589)
Net cash used in operating activities	(6,381)	(5,711)
Investing activities
Purchases of property and equipment	(102)	(53)
Net cash used in investing activities	(102)	(53)
Financing activities
Proceeds from issuance of common stock, net	2	6,382
Proceeds from exercise of common stock options	0	26
Payments on financing leases	0	(72)
Net cash provided by financing activities	2	6,336
Net (decrease) increase in cash and cash equivalents	(6,481)	572
Cash and cash equivalents at beginning of period	60,445	31,087
Cash and cash equivalents at end of period	53,964	31,659
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	53,902	31,597
Restricted cash	62	62
Total cash, cash equivalents and restricted cash	53,964	31,659
Supplemental disclosure of cash flow information
Interest paid	(110)	(109)
Income taxes paid	(1)	0
Supplemental disclosure of non-cash investing and financing activities
Non-cash acquisition of property and equipment	$ 33	$ 24