Note 6 - Revenue (Details Textual) - USD ($)	1 Months Ended	12 Months Ended
	Jul. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Nov. 30, 2022
Revenue from Contract with Customer, Including Assessed Tax		$ 7,379,000	$ 107,000
Income Tax Expense (Benefit)		261,000	67,000
Deferred Revenue, Current, Total		$ 0	2,000,000	$ 2,000,000
Foreign Tax Authority [Member] | National Tax Agency, Japan [Member]
Royalty Withholding Tax		5.00%
Income Tax Expense (Benefit)		$ 200,000	5,000
Royalty [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Royalty Percentage		4.00%
Non Cash Royalty Revenue [Member]
Revenue from Contract with Customer, Including Assessed Tax		$ 3,920,000	107,000
Non Cash Royalty Revenue [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax		3,900,000	100,000
Grant [Member]
Revenue from Contract with Customer, Including Assessed Tax		$ 3,459,000	$ 0
Grants Receivable				$ 3,500,000
Grant Milestone Completion [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 1,500,000