Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current Assets
Cash and cash equivalents	$ 8,535	$ 53,689
Prepaid expenses and other current assets	1,027	4,281
Total current assets	9,562	57,970
Restricted cash	2,408	2,445
Property and equipment, net	167	270
Operating lease right-of-use assets	907	1,462
Other assets	5	6
Total assets	13,049	62,153
Current liabilities
Accounts payable	5,423	8,765
Accrued liabilities	2,233	6,738
Operating lease obligation, current portion	2,121	2,195
Current portion of deferred revenue	0	4,414
Total current liabilities	9,777	22,112
Deferred revenue, net of current portion	0	621
Operating lease obligation, net of current portion	306	1,882
Warrant liability	1,265	26,881
Total liabilities	11,348	51,496
Commitments and contingencies (Note 6)
Stockholders' equity
Common stock, $0.0001 par value, 250,000,000 shares authorized at September 30, 2023 and 100,000,000 shares authorized at December 31, 2022; 73,562,648 shares issued and outstanding at September 30, 2023 and 59,844,850 shares issued and outstanding at December 31, 2022	7	6
Additional paid-in capital	628,543	626,778
Accumulated deficit	(626,849)	(616,127)
Total stockholders' equity	1,701	10,657
Total liabilities and stockholders’ equity	$ 13,049	$ 62,153