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Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Nov. 30, 2022	Dec. 31, 2021
Cash, Cash Equivalents, and Short-Term Investments	$ 39,700
Reduction in Workforce, Percentage	27.00%
Severance Costs	$ 500
Restricted Cash, Total	0	$ 2,000
Accounts Receivable, Allowance for Credit Loss, Ending Balance	0	0
Revenue from Contract with Customer, Including Assessed Tax	7,379	107
Deferred Revenue, Current, Total	0	2,000	$ 2,000
Grant [Member]
Grants Receivable			$ 3,500
Revenue from Contract with Customer, Including Assessed Tax	$ 3,459	$ 0
Developed Technology Rights [Member] \| Maximum [Member]
Finite-Lived Intangible Asset, Useful Life (Year)				11 years 9 months
Intellectual Property [Member]
Finite-Lived Intangible Asset, Useful Life (Year)				20 years
Customer Concentration Risk [Member] \| Accounts Receivable [Member] \| Daiichi Sankyo [Member]
Concentration Risk, Percentage	100.00%	100.00%