Note 6 - Commitments and Contingencies (Details Textual) - USD ($)	1 Months Ended			3 Months Ended			6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Feb. 28, 2022	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Sublease Income				$ 12,000		$ 10,000	$ 25,000	$ 21,000
Operating Lease, Payments				38,000		35,000	75,000	70,000
License Agreements Expense				64,000		56,000	129,000	133,000
Research and Development Expense				3,888,000		4,204,000	9,576,000	8,824,000
Stock Issued During Period, Value, New Issues				69,000	$ 141,000
MD Anderson [Member]
Payments For Research And Development Agreement	$ 800,000
MD Anderson [Member] | Sponsored Research [Member]
Research and Development Expense				176,000		313,000	331,000	500,000
WPD Pharmaceuticals [Member] | License Termination [Member]
Payments for Termination of Commitment		$ 700,000
Stock Issued During Period, Value, New Issues		$ 800,000			$ 800,000
Stock Issued During Period, Shares, New Issues (in shares)		822,115			822,115
Exploration Invest Pte Ltd. (Exploration) [Member]
Payments for Termination of Commitment			$ 400,000
License Terminations Expense				1,500,000		400,000	1,500,000	400,000
Houston Pharmaceuticals, Inc [Member]
Related Party Transaction, Amounts of Transaction				$ 59,000		$ 59,000	$ 117,000	$ 117,000