Note 10 - Equity Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2022

Notes Tables

Share-Based Payment Arrangement, Activity [Table Text Block]

							Weighted				Weighted
	Shares			Number of			Average		Number of		Average
	Available			Options			Exercise		RSUs		Grant Date
	For Grant			Outstanding			Price		Outstanding		Fair Value
Balance at January 1, 2022		5,582,742			10,216,106		$	4.96		—	$	—
Granted		(3,486,375	)		3,240,750		$	5.06		245,625	$	5.09
Exercised		—			(30,418	)	$	1.57		—	$	—
Forfeited		172,726			(172,791	)	$	7.04		—	$	—
Balance at March 31, 2022		2,269,093			13,253,647		$	4.97		245,625	$	5.09

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

	Three Months Ended March 31,
	2022			2021
Risk-free interest rate		1.62% - 2.55%			1.02% - 1.07%
Expected term (in years)		6.02 - 6.08			5.87 - 6.07
Expected volatility		125% - 126%			122% - 124%
Dividend yield		—	%		—	%

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

	Three Months Ended March 31,
	2022		2021
Research and development	$	2,027	$	579
General and administrative		1,103		672
Total stock-based compensation	$	3,130	$	1,251