Stock-Based Compensation

The Company recognized total stock-based compensation expense during the three months ended March 31, 2020 and 2019 as follows:



	Three Months Ended March 31,
	2020		2019
Service based awards:
Restricted stock units	$	238,115	$	344,351
Stock option awards	439,625		652,024
	677,740		996,375
Performance based awards:
Restricted stock units	171,210		398,388
Stock option awards	85,897		122,539
	257,107		520,927
Total	$	934,847	$	1,517,302

Restricted Stock

A summary of the Company’s restricted stock awards during the three months ended March 31, 2020 is as follows:

A summary of the Company’s restricted stock awards during the three months ended March 31, 2019 is as follows:

The fair value of restricted stock awards are measured based on their fair value on the date of grant and amortized over the vesting period of 20 months. As of March 31, 2020 unvested restricted stock awards of 146,800 were related to performance based awards.

Service Based Restricted Stock Units

A summary of the Company’s service based restricted stock units during the three months ended March 31, 2020 is as follows:



	Number of Shares		Weighted Average Grant-Date Fair Value
Unvested at January 1, 2020	463,786		4.26
Granted	16,304		2.61
Forfeited	(7,460	)	4.15
Unvested at March 31, 2020	472,630		4.21

A summary of the Company’s service based restricted stock units during the three months ended March 31, 2019 is as follows:

The fair value of service based restricted stock units are measured based on their fair value on the date of grant and amortized over the vesting period. The vesting periods range from 1 to 3 years. Stock-based compensation expense of $0.2 million and $0.3 million was recognized during the three months ended March 31, 2020 and 2019, respectively. As of March 31, 2020, the unrecognized stock-based compensation expense was $0.7 million, which is expected to be recognized over an estimated weighted average remaining term of 1 year.

Performance Based Restricted Stock Units

A summary of the Company’s performance based restricted stock units during the three months ended March 31, 2020 is as follows:

A summary of the Company’s performance based restricted stock units during the three months ended March 31, 2019 is as follows:

Stock-based compensation expense recognized for performance based restricted stock units was $0.2 million and $0.4 million during the three months ended March 31, 2020 and 2019, respectively. As of March 31, 2020, the unrecognized stock-based compensation expense related to performance based restricted stock units was $0.7 million, which is expected to be recognized over an estimated weighted average remaining term of 2 years.

Service Based Stock Options

The fair value of the service based stock options granted for the three months ended March 31, 2020 were based on the following assumptions:



	March 31, 2020
Exercise price	$2.00 - $2.90
Expected stock price volatility	68.2% - 73.8%
Risk-free interest rate	0.4% - 1.67%
Term (years)	5.5 -6.5

A summary of the Company’s service based stock option activity for the three months ended March 31, 2020 is as follows:



	Shares Underlying Options		Weighted Average Exercise Price			Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value
Outstanding at January 1, 2020	8,210,024		$	7.06		5.1	$	107,150
Granted	51,148		$	2.30		9.9	$	—
Forfeited	(457,334	)	$	(7.02	)	—	$	—
Outstanding at March 31, 2020	7,803,838		$	7.03		5.1	$	1,950

Exercisable at March 31, 2020	6,146,337		$	7.97		4.1	$	—

A summary of the Company’s service based stock option activity for the three months ended March 31, 2019 is as follows:



	Shares Underlying Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value
Outstanding at January 1, 2019	7,856,480		$	7.50	5.2	$	—
Granted	75,000		$	3.49	9.8
Exercised	(30,000	)	$	4.93	—
Outstanding at March 31, 2019	7,901,480		$	7.47	5.0	$	1,959,736

Exercisable at March 31, 2019	6,707,693		$	8.05	4.2	$	206,872

The aggregate intrinsic value in the table above is calculated as the difference between the closing price of our common stock and the exercise price of the stock options that had strike prices below the closing price.

During the three months ended March 31, 2020, the Company granted stock options to purchase up to 51,148 shares of common stock to certain employees. During the three months ended March 31, 2020, 457,334 shares were forfeited. Forfeitures are recorded in the period of occurrence; compensation expense is adjusted accordingly.

Stock-based compensation expense recognized for service based stock options was $0.4 million and $0.7 million for the three months ended March 31, 2020 and 2019, respectively. As of March 31, 2020, total stock-based compensation expense related to unvested options not yet recognized totaled approximately $1.7 million, which is expected to be recognized over an estimated weighted average remaining term of 1.2 years.

Performance Based Stock Options

A summary of the performance based stock options for the three months ended March 31, 2020 is as follows:



	Number of Shares	Weighted Average Exercise Price
Outstanding at January 1, 2020	388,125	$	4.70
Outstanding at March 31, 2020	388,125	$	4.70

Exercisable at March 31, 2020	—	$	—

A summary of the performance based stock options for the three months ended March 31, 2019 is as follows:



	Number of Shares	Weighted Average Exercise Price
Outstanding at January 1, 2019	388,125	$	4.70
Outstanding at March 31, 2019	388,125	$	4.70

Exercisable at March 31, 2019	—	$	—

Stock-based compensation expense recognized for performance based stock options was $0.1 million for the three months ended March 31, 2020 and 2019. As of March 31, 2020, the unrecognized stock-based compensation expense related to performance based stock options was $0.4 million.

On April 17, 2020, Stuart Paul resigned as Chief Executive Officer of the Company, effective immediately. The effects of his resignation are discussed in Note 18 below. The tables above are as of March 31, 2020 and do not reflect Mr. Paul's resignation. All changes relating to his resignation will be reflected in the Company's Quarterly Report on Form 10-Q for the quarter ended June 30, 2020.

Number of Shares

Weighted Average
Grant-Date
Fair Value

Unvested at January 1, 2020

Unvested at March 31, 2020