Note 5 - Revenue (Details Textual) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Nov. 30, 2022
Revenue from Contract with Customer, Including Assessed Tax		$ 2,101,000	$ 0	$ 4,134,000	$ 85,000
Income Tax Expense (Benefit)		39,000	16,000	87,000	51,000
Deferred Revenue, Current		79,000		$ 79,000		$ 2,000,000	$ 2,000,000
Foreign Tax Authority [Member] | National Tax Agency, Japan [Member]
Royalty Withholding Tax				5.00%
Income Tax Expense (Benefit)		23,000	0	$ 38,000	4,000
Royalty [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Royalty Percentage				4.00%
Revenue from Contract with Customer, Including Assessed Tax				$ 0	0
Non Cash Royalty Revenue [Member]
Revenue from Contract with Customer, Including Assessed Tax		446,000	0	754,000	85,000
Non Cash Royalty Revenue [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax		400,000	0	800,000	85,000
Grant Milestone Completion [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 1,500,000
Grant [Member]
Revenue from Contract with Customer, Including Assessed Tax		$ 1,655,000	$ 0	$ 3,380,000	$ 0