Stock Options (Tables)

6 Months Ended

Jun. 30, 2018

The Company issued the following non-qualified options to purchase shares of common stock to its newly appointed executives who are still employed by the Company. The awards were granted outside of the Company's 2014 Equity Incentive Plan and vest over four years with 25% vesting one year following the date of hire, and the remaining 75% vesting in 36 equal monthly installments thereafter, subject to continued service to the Company through each vesting date and subject to acceleration or forfeiture upon the occurrence of certain events as set forth in the applicable option agreement and employment agreement. The grant awards were made pursuant to the NASDAQ inducement grant exception as a material component of employment compensation.

Issue Date	25% Vesting Date	Executive	Number of Options
November 16, 2015	October 30, 2016	SVP, General Counsel and Secretary	80,000
March 1, 2017	February 28, 2018	SVP, Regulatory Affairs	80,000
November 1, 2017	October 31, 2018	Chief Financial Officer	200,000

Stock-Based Compensation Expense

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
	(unaudited)				(unaudited)
Stock-Based Compensation
Research and development	$	631,511	$	779,349	$	1,428,851	$	1,387,792
General and administrative		1,027,107		801,174		2,215,554		1,678,436
Total	$	1,658,618	$	1,580,523	$	3,644,405	$	3,066,228

Assumptions Used to Value Stock Options and Warrants Granted

The fair value of options and warrants granted during the three months ended June 30, 2018 and 2017 was estimated using the Black-Scholes option valuation model utilizing the following assumptions:

	Three Months Ended June 30,						Six Months Ended June 30,
	2018			2017			2018			2017
	Weighted Average			Weighted Average			Weighted Average			Weighted Average
	(unaudited)						(unaudited)
Volatility		87.82	%		85.71	%		89.06	%		88.93	%
Risk-Free Interest Rate		2.27	%		1.84	%		2.31	%		1.89	%
Expected Term in Years		2.50			5.56			4.24			5.99
Dividend Rate		0.00	%		0.00	%		0.00	%		0.00	%
Fair Value of Option on Grant Date	$	0.58		$	7.15		$	5.54		$	6.73

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, 2017		6,462,795		$	6.50
Granted		2,322,906			7.52
Exercised		(198,300	)		3.64
Forfeited		(1,194,835	)		10.35
Options outstanding at June 30, 2018		7,392,566		$	6.28		6.43	$	107,730
Vested and expected to vest at June 30, 2018		7,392,566		$	6.28		6.43	$	107,730
Exercisable at June 30, 2018		4,183,685		$	5.54		6.01	$	107,730