Note 1 - Nature of Operations (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended	33 Months Ended
	Jul. 12, 2022	Jul. 31, 2022	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2023	Jul. 13, 2022	Jun. 16, 2020
Retained Earnings (Accumulated Deficit)			$ (234,310)		$ (234,310)	$ (224,105)	$ (234,310)
Proceeds from Issuance of Common Stock			803	$ 0
Stock Issued During Period, Value, New Issues			$ 745
Equity Purchase Agreement [Member] | Lincoln Park [Member]
Equity Purchase Agreement, Maximum Offering Amount									$ 31,000
Stock Issued During Period, Shares, New Issues (in shares)		20,000.00				26,666,000	229,139
Proceeds from Issuance of Common Stock		$ 300				$ 272
Shares Issued, Price Per Share (in dollars per share)			$ 40.50		$ 40.50		$ 40.50
LPC Purchase Agreement 2022 [Member] | Lincoln Park [Member]
Equity Purchase Agreement, Maximum Offering Amount	$ 11,000
Stock Issued During Period, Shares, New Issues (in shares)	50,000.00		224,386		660,000	433,333
Stock Issued During Period, Value, New Issues	$ 300		$ 803		$ 2,800	$ 1,970
Shares Issued, Price Per Share (in dollars per share)			$ 3.58		$ 3.58	$ 4.54	$ 3.58	$ 4.20