Note 5 - Revenue (Details Textual) - USD ($)	3 Months Ended		6 Months Ended		37 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 28, 2018	Sep. 30, 2015
Revenue from Contract with Customer, Including Assessed Tax	$ 85,000	$ 608,000	$ 5,492,000	$ 2,111,000
Income Tax Expense (Benefit), Total	13,000	1,000	$ 263,000	29,000
Foreign Tax Authority [Member] | National Tax Agency, Japan [Member]
Royalty Withholding Tax			5.00%
Income Tax Expense (Benefit), Total	1,000	1,000	$ 237,000	29,000
Government Contract [Member]
Contract Value					$ 15,700,000	$ 14,000,000
Contract Value, Adjustment					$ 1,700,000
Revenues, Total		520,000		1,130,000
Revenue from Contract with Customer, Including Assessed Tax		520,000		1,130,000
Royalty [Member]
Revenue from Contract with Customer, Including Assessed Tax	69,000	70,000	3,728,000	963,000
Royalty [Member] | GSK Research and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax	69,000	70,000	$ 764,000	$ 411,000
Royalty Percentage			7.00%	7.00%
Royalty [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax	0	0	$ 2,964,000	$ 552,000
Royalty Percentage			4.00%	4.00%
Royalty [Member] | Daiichi Sankyo Collaberation and License Agreement [Member] | HealthCare Royalty Partners III, L.P. [Member]
Liability Related to Sale of Future Royalties	$ 16,000	$ 18,000	$ 16,000	$ 18,000