Stock Options (Tables)

3 Months Ended

Mar. 31, 2017

Stock Options [Abstract]

Stock-Based Compensation Expense

The Company’s stock-based compensation expense was recognized in operating expense as follows:

		Three Months Ended March 31,
		2017		2016
	(unaudited)
Stock-Based Compensation
Research and development		$	608,443	$	497,529
General and administrative			877,262		917,772
Total		$	1,485,705	$	1,415,301

Assumptions Used to Value Stock Options and Warrants Granted

The fair value of options and warrants granted during the three months ended March 31, 2017 and 2016 was estimated using the Black-Scholes option valuation model utilizing the following assumptions:

		Three Months Ended March 31,
		2017			2016
		Weighted Average			Weighted Average
	(unaudited)
Volatility			89.37	%		79.80	%
Risk-Free Interest Rate			1.90	%		1.41	%
Expected Term in Years			6.05			6.08
Dividend Rate			0.00	%		0.00	%
Fair Value of Option on Grant Date		$	6.67		$	4.97

Stock Option Activity

The following table summarizes the number of options outstanding and the weighted average exercise price:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years		Aggregate Intrinsic Value
Options outstanding at December 31, 2016		5,316,511		$	5.84
Granted		965,700			8.97
Exercised		(25,000	)		2.04
Forfeited		(63,750	)		8.20
Options outstanding at March 31, 2017		6,193,461		$	6.32		7.75		$	19,191,512
Vested and expected to vest at March 31, 2017		6,193,461		$	6.32		7.75		$	19,191,512
Exercisable at March 31, 2017		3,358,600		$	4.62		6.68		$	15,807,994