Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 131,486	$ 136,377
Restricted cash	110	110
Prepaid expenses	3,874	2,488
Research and development rebate receivable	668	1,072
Other current assets	710	1,193
Total current assets	136,848	141,240
Other assets	630	22
Total Assets	137,478	141,262
Current liabilities
Accounts payable	1,596	1,717
Accrued expenses	120	204
Payroll liabilities	593	1,184
Other current liabilities	13	21
Total current liabilities	2,322	3,126
Total Liabilities	2,322	3,126
Commitments and contingencies (Note 13)
Stockholders' equity
Preferred stock - $0.001 par value; 10,000 shares authorized; 1 share issued and outstanding as of March 31, 2022 and December 31, 2021	0	0
Common stock - $0.18 par value; 175,000 shares authorized; 126,624 shares issued and outstanding as of March 31, 2022 and December 31, 2021	22,792	22,792
Additional paid-in capital - common stock	245,802	243,996
Accumulated deficit	(134,020)	(129,234)
Total Stockholders' Equity	135,156	138,136
Total Liabilities and Stockholders' Equity	137,478	141,262
Series B Preferred Stock [Member]
Stockholders' equity
Additional paid-in capital - Series B convertible preferred stock	$ 582	$ 582