Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets
Cash and cash equivalents	$ 83,960	$ 88,460
Restricted cash	110	110
Prepaid materials	1,372	1,487
Prepaid expenses and other current assets	1,613	2,162
Total current assets	87,055	92,219
Investment in equity securities	1,710	1,710
Other assets	2,322	2,323
Total Assets	91,087	96,252
Current liabilities
Accounts payable	1,230	806
Accrued expenses	1,613	973
Payroll liabilities	659	1,654
Other current liabilities	1,826	1,803
Total current liabilities	5,328	5,236
Total Liabilities	5,328	5,236
Commitments and contingencies (Note 13)
Stockholders' equity
Convertible preferred stock - $0.001 par value; 10,000,000 shares authorized; 582 shares issued and outstanding as of March 31, 2024 and December 31, 2023	0	0
Common stock - $0.18 par value; 175,000,000 shares authorized; 125,507,814 and 125,304,064 shares issued and outstanding as of March 31, 2024 and December 31, 2023, respectively	22,829	22,792
Additional paid-in capital	256,571	255,987
Treasury stock, at cost; 1,320,046 shares of common stock at March 31, 2024 and December 31, 2023	(1,475)	(1,475)
Accumulated deficit	(192,166)	(186,288)
Total Stockholders' Equity	85,759	91,016
Total Liabilities and Stockholders' Equity	$ 91,087	$ 96,252