Note 10 - Stockholder's Equity (Tables)

9 Months Ended

Sep. 30, 2020

Notes Tables

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Cost of product sales	$	23	$	32	$	67	$	124
Research and development cost		24		34		124		168
General and administrative expense		473		835		1,841		2,607
Total	$	520	$	901	$	2,032	$	2,899

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Three Months Ended September 30,		Nine Months Ended September 30,
	2019		2019
Expected stock volatility		86.2% - 86.5%		82.3% - 87.5%
Risk free interest rate		1.7% - 1.8%		1.7% - 2.6%
Expected years until exercise		3.5		1.0 - 4.0
Dividend yield		0%		0%