Note 7 - Commitments and Contingencies (Details Textual)		3 Months Ended		6 Months Ended
	Mar. 16, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)
Sublease Income		$ 10,000	$ 10,000	$ 21,000	$ 21,000
Operating Lease, Payments		34,000	33,000	68,000	66,000
License Agreements Expense		56,000	61,000	94,000	122,000
Research and Development Expense, Total		3,039,000	3,329,000	7,145,000	6,535,000
MD Anderson [Member]
Research and Development Expense, Total		184,000	212,000	278,000	358,000
Houston Pharmaceuticals, Inc [Member]
Other Commitments, Number of Agreements	2
Related Party Transaction, Expenses from Transactions with Related Party		$ 59,000	$ 59,000	$ 117,000	$ 167,000
Houston Pharmaceuticals, Inc [Member] | Consulting Agreement on Licensed Molecules [Member]
Other Commitments, Term (Year)	2 years
Other Commitment, Total	$ 43,500
Houston Pharmaceuticals, Inc [Member] | Agreement Providing Access to Laboratory Equipment [Member]
Other Commitment, Total	$ 15,000
Other Commitments, Cancellation Period (Day)	60 days