Note 10 - Equity Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2021

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, 2021		1,230,863			6,813,033		$	2.70
Granted		(1,163,000	)		1,163,000		$	6.27
Exercised		—			(207,730	)	$	1.11
Canceled		—			(4,139	)	$	5.17
Balance at March 31, 2021		67,863			7,764,164		$	3.28

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

Risk-free interest rate		1.02% - 1.07%
Expected term	5.87 - 6.07 Years
Expected volatility		122% - 124%
Dividend yield		—	%

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

	Three Months Ended March 31,
	2021		2020
Research and development	$	579	$	22
General and administrative		672		74
Total stock-based compensation	$	1,251	$	96