Note 7 - Equity Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2022

Table Text Block [Abstract]

Schedule of Fair Value of Options Granted

The fair value of options granted in the six months ended June 30, 2022 and June 30, 2021 is estimated as of the grant date using the Black-Scholes option pricing model using the assumptions in the following table:

	Six Months Ended June 30,
	2022			2021
Weighted-average exercise price per share	$	0.89		$	17.72
Weighted-average expected term (years)		5.81			5.00
Weighted-average risk-free interest rate		2.17	%		0.88	%
Weighted-average expected dividend yield		—			—
Weighted-average volatility		73.70	%		76.05	%

Schedule of Summarized Stock Option Activity

The following table summarizes stock option activity and related information under the 2013 Plan, the 2021 EIP Plan and the 2021 Inducement Plan for the six months ended June 30, 2022:

	Number of Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2021		1,956,855	$	7.32		8.12	$	—
Granted		699,600		0.89		9.69		—
Exercised		—		—		—		—
Forfeited, expired or cancelled		—		—		—		—
Outstanding at June 30, 2022		2,656,455		5.63		8.36		—
Vested and expected to vest at June 30, 2022		2,656,455		5.63		8.36		—
Exercisable at June 30, 2022		1,145,598	$	10.78		6.83	$	—

Schedule of Stock-based Compensation for all Stock Awards

The allocation of stock-based compensation for all stock awards is as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development expense	$	59	$	49	$	111	$	323
General and administrative		277		446		583		741
Total	$	336	$	495	$	694	$	1,064