Stock Option and Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2018

A summary of stock option activity for the nine months ended September 30, 2018, is summarized as follows:


	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Options outstanding at December 31, 2017		6,200,151		$	3.81
Granted		2,280,000			1.45
Exercised		—			—
Expired		(865,606	)		3.93
Forfeited		(366,347	)		1.84

Options outstanding at September 30, 2018		7,248,198			3.15		6.92	$	1,987,550

Vested and exercisable at September 30, 2018		4,714,393			3.88		5.89	$	762,306

The following assumptions were used to compute the fair value of stock option grants:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018			2017
Risk free interest rate		—		—		2.57	%		2.08	%
Expected dividend yield		—		—		—			—
Expected term (in years)		—		—		6.02			6.00
Expected volatility		—		—		82.3	%		79.1	%