Note 11 - Equity Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2020

Notes Tables

Share-based Payment Arrangement, Option, Activity [Table Text Block]

							Weighted
	Shares			Number of			Average
	Available			Options			Exercise
	For Grant			Outstanding			Price
Balance at January 1, 2020		295,180			1,811,652		$	2.74
2019 Plan Amendment		6,400,000
PRSUs granted, net of tax forfeitures		(278,535	)		—		$	—
Granted		(4,892,100	)		4,892,100		$	2.04
Exercised		—			(178,381	)	$	0.65
Forfeited		85,910			(85,992	)	$	0.39
Canceled		9,573			(57,147	)	$	10.50
Balance at June 30, 2020		1,620,028			6,382,232		$	2.22

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

	Six Months Ended June 30,
	2020	2019
Risk-free interest rate	0.44% - 0.88%	1.89% - 2.31%
Expected term	5.22 - 10.00 Years	5.39 - 6.08 Years
Expected volatility	94% - 104%	83% - 85%
Dividend yield	—%	—%

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
	(in thousands)				(in thousands)
Research and development	$	1,115	$	80	$	1,137	$	159
General and administrative		1,745		100		1,819		185
Total stock-based compensation	$	2,860	$	180	$	2,956	$	344