Note 1 - Significant Accounting Policies and Concentrations of Risk (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

Debt Securities, Available-for-sale [Table Text Block]

	December 31, 2020
	Amortized Cost		Accrued Interest		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of U.S. Government and its agencies	$	24,986	$	14	$	3	$	(3	)	$	25,000
Certificates of deposit		3,225		11		3		−			3,239
Total Investments	$	28,211	$	25	$	6	$	(3	)	$	28,239

	December 31, 2019
	Amortized Cost		Accrued Interest		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of U.S. Government and its agencies	$	10,488	$	50	$	23	$	−		$	10,561
Corporate debt securities		9,742		59		10		(1	)		9,810
Certificates of deposit		1,669		7		7		−			1,683
Total Investments	$	21,899	$	116	$	40	$	(1	)	$	22,054

Schedule of Receivables from Collaborations [Table Text Block]

	December 31, 2020
	Billed		Unbilled		Total
U.S. Department of Health and Human Services	$	−	$	5,402	$	5,402
Shionogi & Co. Ltd.		2,037		4		2,041
Green Cross Corporation		740		21		761
Mundipharma International Holdings Limited		39		−		39
Total receivables	$	2,816	$	5,427	$	8,243

	December 31, 2019
	Billed		Unbilled		Total
U.S. Department of Health and Human Services	$	1,353	$	15,023	$	16,376
Shionogi & Co. Ltd.		1,336		4		1,340
Green Cross Corporation		2,924		8		2,932
Mundipharma International Holdings Limited		56		-		56
Seqirus UK Limited		1,091		351		1,442
Total receivables	$	6,760	$	15,386	$	22,146

Schedule of Accrued Liabilities [Table Text Block]

	December 31,
	2020		2019
Compensation and benefits	$	11,030	$	6,190
Development costs		15,150		11,302
Inventory		2,453		29
Professional fees		333		326
Duties and taxes		80		67
Other		4,896		3,451
Total accrued expenses	$	33,942	$	21,365

Disaggregation of Revenue [Table Text Block]

	2020		2019		2018
Product sales, net	$	3,301	$	17,533	$	−
Royalty revenue		3,381		6,303		6,101
Collaborative and other research and development revenues:
U.S. Department of Health and Human Services		9,231		4,898		2,552
Torii Pharmaceutical Co., Ltd.		1,899		20,101		−
Seqirus UK Limited		−		−		12,000
Total collaborative and other research and development revenues		11,130		24,999		14,552
Total revenues	$	17,812	$	48,835	$	20,653