Preferred Stock, Common Stock and Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Summary of Warrants Activity

  A summary of the Company’s warrant activity is as follows:

					Weighted
			Weighted		Average
			Average		Remaining
			Exercise		Contractual
	Shares		Price		Term (Years)
Outstanding at December 31, 2014		118,881	$	16.73		5.35
Issued	—		—		—
Exercised	—		—		—
Expired/Forfeited	—		—		—
Outstanding at December 31, 2015		118,881	$	16.73		4.35

Summary of Stock Option Activity

A summary of the Company’s stock option activity under the 2007 Plan and 2013 Plan is as follows:

					Weighted
			Weighted		Average
			Average		Remaining
			Exercise		Contractual		Aggregate
	Shares		Price		Term (Years)		IntrinsicValue
Outstanding at December 31, 2014		683,500	$	7.67		8.45	$	649,000
Granted		354,000	$	6.25		9.20	—
Exercised	—		—		—		—
Expired/Forfeited	—		—		—		—
Outstanding at December 31, 2015		1,037,500	$	7.19		8.04	$	342,200
Vested and expected to vest at December 31, 2015		1,037,500	$	7.19		8.04	$	342,200
Exercisable at December 31, 2015		530,079	$	6.80		7.50	$	342,200

Summary of Nonvested Options Activity

The Company had the following nonvested options under the 2007 Plan and 2013 Plan:

	Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested at December 31, 2014		424,419		$	9.02
Granted		354,000		$	4.03
Vested		(270,998	)	$	8.07
Expired/Forfeited	—			—
Nonvested at December 31, 2015		507,421		$	7.60

Summary of Estimated Fair Value of Stock Option Award

The estimated fair value of each option award granted was determined on the date of grant using the Black-Scholes option-pricing valuation model with the following weighted-average assumptions for options grants during the two years ended December 31, 2015:

	Year Ended December 31,
	2015		2014
Risk free interest rate	1.50% - 1.87%		1.66% - 1.77%
Expected option term	5.5 - 6.0 years		5.5 - 6.0 years
Expected volatility of common stock	71.99% - 76.74%		71.06% - 73.21%
Expected dividend yield		0.0%		0.0%

Summary of Estimated Fair Value of Employee Stock Purchase Plan Award

The estimated fair value of the shares to be acquired under the ESPP was determined on the initiation date of each six month purchase period using the Black-Scholes option-pricing valuation model with the following weighted-average assumptions for ESPP shares to be purchased during the year ended December 31, 2015 and 2014:

	Year Ended December 31,
	2015		2014
Risk free interest rate	0.08% - 0.26%		0.05% - 0.08%
Expected term	6 months		6 months
Expected volatility of common stock	62.91% - 69.64%		69.32% - 73.21%
Expected dividend yield		0.0%		0.0%

Summary of Recognized Non-Cash Stock-Based Compensation Expense

The Company recognized non-cash stock-based compensation expense to employees and directors in its research and development and its general and administrative functions as follows:

	Year Ended December 31,
	2015		2014
Research and development	$	579,078	$	410,150
General and administrative		925,278		691,937
Total stock-based compensation expense	$	1,504,356	$	1,102,087

Summary of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following at December 31, 2015 and 2014:

	December 31,
	2015		2014
Stock options issued and outstanding		1,037,500		683,500
Authorized for future option grants		78,854		188,370
Warrants to purchase common stock		118,881		118,881
Authorized for employee stock purchase plan		41,530		52,706
Total common stock reserved for future issuance		1,276,765		1,043,457