Note 4 - Summary of Significant Accounting Policies (Details Textual) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		4 Months Ended
	Apr. 30, 2022 $ / shares shares	Mar. 31, 2022 USD ($) shares	Mar. 31, 2021 USD ($) shares	Apr. 30, 2022 $ / shares shares	Dec. 31, 2021 USD ($)	Nov. 01, 2017 USD ($)
Number of Reporting Units		1
Foreign Currency Transaction Gain, before Tax		$ 200	$ 100
Severance Costs		400
Severance Accrual		300
Depreciation, Total		466	$ 45
Liability for Contingent Milestone Payment, Noncurrent		$ 15,000			$ 15,000
Number of Shares of Common Stock Potentially Issuable upon the Exercise of Stock Options and Warrants (in shares) | shares		21,400,000	19,900,000
Deerfield Loan [Member] | Exchange and Termination Agreement [Member] | Deerfield Management, L.P. [Member]
Liability for Contingent Milestone Payment, Noncurrent						$ 15,000
Manufacturing and Laboratory Equipment [Member]
Depreciation, Total		$ 400
ATM Program [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares		200,348	105,083
Subsequent Event [Member] | ATM Program [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares	936,898			936,898
Subsequent Event [Member] | ATM Program [Member] | Weighted Average [Member]
Shares Issued, Price Per Share (in dollars per share) | $ / shares	$ 1.13			$ 1.13