Note 10 - Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2024

Notes Tables

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

							Weighted					Weighted
	Shares			Number of			Option Average		Number of			RSU Average
	Available			Options			Exercise		RSUs			Grant Date
	For Grant			Outstanding			Price		Outstanding			Fair Value
Balance at January 1, 2023		12,074,692			14,725,261		$	4.48		808,310		$	3.57
Granted		(10,631,320	)		7,399,849		$	0.78		3,231,471		$	0.78
Exercised		—			(54,720	)	$	0.31		(1,608,809	)	$	1.09
Forfeited		2,444,486			(2,139,887	)	$	5.00		(304,599	)	$	2.42
Canceled		1,797,948			(1,991,777	)	$	4.51		—		$	—
Balance at December 31, 2023		5,685,806			17,938,726		$	2.90		2,126,373		$	1.37
Authorized under 2024 Inducement Plan		3,000,000			—		$	—		—		$	—
Authorized under 2019 Plan Amendment		15,000,000			—		$	—		—		$	—
Granted		(7,258,980	)		5,309,437		$	1.12		1,949,543		$	1.13
Exercised		—			(38,030	)	$	0.78		—		$	—
Released		—			—		$	—		(599,260	)	$	1.48
Forfeited		1,944,001			(1,483,826	)	$	2.29		(460,175	)	$	1.41
Canceled		1,279,297			(1,321,068	)	$	2.87		—		$	—
Balance at December 31, 2024		19,650,124			20,405,239		$	2.49		3,016,481		$	1.19

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

	Year Ended December 31,
	2024			2023
Risk-free interest rate		3.7% - 4.4%			3.5% - 4.2%
Expected term (in years)		5.50 - 6.00			5.50 - 6.00
Expected volatility		128.9% - 130.8%			127.8% - 133.8%
Dividend yield		—	%		—%

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

	Year Ended December 31,
	2024		2023
Research and development	$	7,246	$	8,362
General and administrative		4,255		5,770
Total stock-based compensation	$	11,501	$	14,132