Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2024

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Stock-Based Compensation Expense on All Employee and Non-Employee Awards

The Company recognized stock-based compensation expense on all employee and non-employee awards as follows:

	Three Months Ended March 31,
(in thousands)	2024		2023
Research and development	$	11	$	175
General and administrative		161		735
Stock-based compensation expense	$	172	$	910

Fair Value of Stock Options Assumptions Using Black-Scholes Option Valuation Model

For the three months ended March 31, 2024 and 2023, the fair value of stock options was estimated on the date of grant using a Black-Scholes option valuation model with the following assumptions:

	Three Months Ended March 31,
	2024	2023
Risk-free interest rate	4.09%	3.58 – 3.87%
Expected life in years	5.27	5.06 – 6.25
Expected volatility	114.65%	89.69 – 95.63%
Expected dividend yield	—%	—%

Stock Option Activity under Stock Option Plan

Stock option activity under the Company’s stock option plans for the three months ended March 31, 2024 was as follows:

(in thousands, except share and per share data)	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding, December 31, 2023		465,898		$	26.85
Granted		40,000			1.80
Exercised		-			-
Cancelled		(254,441	)		19.61
Outstanding, March 31, 2024		251,457		$	21.15		6.92	$	—
Options exercisable, March 31, 2024		161,844		$	28.28		5.53	$	—
Options available for future grant, March 31, 2024		1,514,087