Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation (Tables)

Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Schedule of stock-based compensation expense

The amount of stock-based compensation expense recognized for the three months ended March 31, 2019 and 2018 was as follows:



	Three Months Ended March 31,
	2019		2018
Research and development	$	57,376	$	11,497
General and administrative	489,953		207,382
Sales and marketing	49,364		23,945
Total stock-based compensation	$	596,693	$	242,824

Summary of option activity

A summary of option activity with market-based vesting conditions for the three months ended March 31, 2019 is as follows:



	Options Outstanding
	Number of shares	Weighted average exercise price		Weighted average remaining contractual term (in years)	Aggregate intrinsic value (1)
Balance at December 31, 2018	500,000	$	4.24	9.24
Granted	—
Balance at March 31, 2019	500,000	$	4.24	8.99	$	800,000
Exercisable at March 31, 2019	—

(1) The aggregate intrinsic value in the above table represents the total pre-tax amount that a participant would receive if the option had been exercised on the last day of the respective fiscal period. Options with a market value less than its exercise value are not included in the intrinsic value amount.

A summary of option activity for the three months ended March 31, 2019 is as follows:



	Options Outstanding
	Number of shares		Weighted average exercise price		Grant date fair value of options		Weighted average remaining contractual term (in years)
Balance at December 31, 2018	3,746,597		$	4.16			7.79
Granted	134,379		$	4.78	$	334,624
Exercised	(31,288	)	$	3.01
Forfeited	(4,383	)	$	4.25	$	11,297
Balance at March 31, 2019	3,845,305		$	4.19			7.61
Exercisable at March 31, 2019	2,269,081		$	4.56			6.76

Schedule of fair value assumptions for options

The following table shows the assumptions used to compute stock-based compensation expense for stock options with service-based vesting conditions granted to employees and members of the board of directors under the Black-Scholes valuation model for the three months ended March 31, 2019. There were no stock options granted with market-based vesting conditions for the three months ended March 31, 2019.



Service-based options
Expected dividend yield		—%
Expected volatility		55%
Expected life (in years)		5.0 - 6.25
Risk-free interest rate		2.23 - 2.59%

Nonvested Restricted Stock Shares Activity

A summary of RSU grants activity for the three months ended March 31, 2019 is as follows:



	RSUs outstanding
	Number of shares		Weighted average grant date fair value
Non-vested RSUs at December 31, 2018	445,000		$	4.27
Vested	(100,000	)	$	4.24
Non-vested RSUs at March 31, 2019	345,000		$	4.27