Share-Based Compensation

We utilize share-based compensation in the form of stock options, restricted stock, and restricted stock units. The following table summarizes the components of share-based compensation expense for the three months ended March 31, 2020 and 2019 (in thousands):



	Three Months Ended March 31,
	2020		2019
Research and development	$	125	$	124
General and administrative	442		423
Total share-based compensation expense	$	567	$	547

Total compensation cost related to non-vested awards not yet recognized and the weighted-average periods over which the awards were expected to be recognized at March 31, 2020 were as follows (in thousands):



	Stock Options		Restricted Stock Units		Restricted Stock
Unrecognized compensation cost	$	891	$	267	$	260
Expected weighted-average period in years of compensation cost to be recognized	1.93		0.89		0.75

Total fair value of shares vested and the weighted average estimated fair values of shares granted for the three months ended March 31, 2020 and 2019 were as follows (in thousands):



	Stock Options
	Three Months Ended March 31,
	2020		2019
Total fair value of shares vested	$	502	$	372
Weighted average estimated fair value of shares granted	$	2.16	$	3.24

Valuation Assumptions

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.