Note 10 - Stock-based Compensation

3 Months Ended

Mar. 31, 2024

Notes to Financial Statements

Share-Based Payment Arrangement [Text Block]

10. Stock-Based Compensation Stock

2015 Equity Plan

The 2015 Equity Plan provides for increases to the number of shares reserved for issuance thereunder each January 1 equal to 4.0% of the total shares of the Company’s common stock outstanding as of the immediately preceding December 31, unless a lesser amount is stipulated by the Compensation Committee of the Board. As of March 31, 2024, there were 37,678 shares available for future issuance under the 2015 Equity Plan.

2018 Employee, Director and Consultant Equity Incentive Plan

On March 28, 2018, EIP adopted the 2018 Plan, which was assumed by the Company pursuant to and in accordance with the terms of the Merger Agreement. Under the 2018 Plan, the Company may issue incentive stock options, non-qualified stock options, stock grants, and other stock-based awards to employees, directors, and consultants, as specified in the 2018 Plan and subject to applicable SEC and Nasdaq rules and regulations. The Board has the authority to determine to whom options or stock will be granted, the number of shares, the term, and the exercise price. Options granted under the 2018 Plan have a term of up to ten years and generally vest over a four-year period with 25% of the options vesting after one-year of service and the remainder vesting monthly thereafter. As of March 31, 2024, there were no shares available for issuance.

The Company recorded stock-based compensation expense in the following expense categories of its consolidated statements of operations:

	Three Months Ended March 31,
	2024		2023
Research and development	$	63,797	$	40,126
General and administrative		154,418		31,114
Total stock-based compensation expense	$	218,215	$	71,240

The following table summarizes the activity related to all stock option grants for the three months ended March 31, 2024:

	Number of Options			Weighted average exercise price per share		Weighted average remaining contractual life (in years)		Aggregate intrinsic value
Balance at January 1, 2024		349,374		$	51.15
Granted		169,934			9.52
Expired		(51	)		28,897.06
Outstanding at March 31, 2024		519,257		$	34.69		8.5		—
Exercisable at March 31, 2024		192,004		$	79.03		6.7		—

The Black-Scholes option pricing model was used to estimate the grant date fair value of each stock option grant at the time of grant using the following weighted-average assumptions: 

	Three Months Ended March 31,
	2024
Expected term (in years)		5.74 - 5.76
Risk-free interest rate		4.06 - 4.14	%
Expected volatility		79.13 - 79.31	%
Dividend yield		—

There were no stock option grants during the three months ended March 31, 2023.

At March 31, 2024, there was $1.7 million of unrecognized compensation expense that will be recognized over a weighted-average period of 2.3 years.

During the three months ended March 31, 2024 the Company granted 39,721 options in lieu of 2023 executive bonus compensation.