The Company utilizes share-based compensation in the form of stock options, restricted stock, restricted stock units and warrants. The following table summarizes the components of share-based compensation expense for the years ended December 31, 2024 and 2023 ($ in thousands):


	Year Ended December 31,
	2024		2023
Research and development	$	270	$	540
General and administrative	1,383		1,498

Total share-based compensation expense	$	1,653	$	2,038

The Company modified the exercise period of approximately 186,600 shares of one terminated employee's vested stock options and immediately recognized approximately $258 thousand incremental stock-based compensation during the year ended December 31, 2023. There were no modifications for the year ended December 31, 2024.

Total compensation cost related to unvested awards not yet recognized and the weighted-average periods over which the awards are expected to be recognized at December 31, 2024 were as follows ($ in thousands):


	Stock Options		Restricted Stock Units		Warrants		Restricted Stock
Unrecognized compensation cost	$	228	$	36	$	—	$	426
Expected weighted-average period in years of compensation cost to be recognized	1.82		0.57		0.00		1.77

Total fair value of shares vested and the weighted average estimated fair values of shares granted for the years ended December 31, 2024 and 2023 were as follows ($ in thousands):


	Stock Options				Warrants
	Year Ended December 31,				Year Ended December 31,
	2024		2023			2024		2023
Total fair value of shares vested	$	204	$	1,033		$	—	$	—
Weighted average estimated fair value of shares granted	2.15		2.09			1.99		—

The fair value of stock options and warrants at the date of grant was estimated using the Black-Scholes option pricing model. The expected volatility is based upon historical volatility of the Company’s stock. The expected term for the options is based upon observation of actual time elapsed between date of grant and exercise of options for all employees. The expected term for the warrants is based upon the contractual term of the warrants.

The range of assumptions made in calculating the fair values of stock options was as follows:


	Stock Options
	Year Ended December 31,
	2024	2023
Expected term - minimum (in years)	6.0	3.0
Expected term - maximum (in years)	6.3	6.0
Expected volatility - minimum	73%	74%
Expected volatility - maximum	77%	77%
Weighted average volatility	77%	75%
Expected dividend yield	—	—
Risk-free interest rate - minimum	3.54%	3.63%
Risk-free interest rate - maximum	4.30%	4.68%