Note 5 - Revenue (Details Textual) - USD ($)	3 Months Ended		37 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jun. 28, 2018	Sep. 30, 2015
Revenues, Total	$ 5,407,000	$ 1,503,000
Income Tax Expense (Benefit), Total	$ 250,000	28,000
Foreign Tax Authority [Member] | National Tax Agency, Japan [Member]
Royalty Withholding Tax	5.00%
Income Tax Expense (Benefit), Total	$ 236,000	28,000
Government Contract [Member]
Contract Value			$ 15,700,000	$ 14,000,000
Contract Value, Adjustment			$ 1,700,000
Revenues, Total		610,000
Royalty [Member]
Revenue from Contract with Customer, Including Assessed Tax	3,659,000	893,000
Royalty [Member] | GSK Research and Licence Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 695,000	$ 341,000
Royalty Percentage	7.00%	7.00%
Royalty [Member] | Daiichi Sankyo Collaberation and License Agreement [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 2,964,000	$ 552,000
Royalty Percentage	4.00%	4.00%
Non Cash Royalty Revenue [Member]
Revenue from Contract with Customer, Including Assessed Tax	$ 1,748,000