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

12 Months Ended

Dec. 31, 2014

Equity [Abstract]

Summary of Warrants Activity

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

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, 2013		624,750		$	7.61		8.41	$	869,490
Granted		64,000		$	7.65		9.35	—
Exercised		(5,250	)	$	0.29		2.70	$	33,810
Expired/Forfeited	—			—		—		—
Outstanding at December 31, 2014		683,500		$	7.67		8.45	$	649,000
Vested and expected to vest at December 31, 2014		683,500		$	7.67		8.45	$	649,000
Exercisable at December 31, 2014(1)		259,081		$	5.47		7.65	$	631,231

— Includes awards with early exercise provisions that permit optionee to exercise unvested options.

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, 2013		534,210		$	8.84
Granted		64,000		$	4.76
Vested		(173,791	)	$	7.96
Expired/Forfeited	—			—
Nonvested at December 31, 2014		424,419		$	9.02

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, 2014:  

	Year Ended December 31,
	2014		2013
Risk free interest rate	1.66% - 1.77%		1.75% - 1.8%
Expected option term	5.5 - 6.0 years		6.0 years
Expected volatility of common stock	71.06% - 73.21%		70.8% - 79.4%
Expected dividend yield		0.00%		0.00%

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, 2014:

	Year Ended December 31,
	2014		2013
Risk free interest rate	0.05% - 0.08%			—
Expected term	6.0 months			—
Expected volatility of common stock	69.32% - 73.21%			—
Expected dividend yield		0.00%		—

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,
	2014		2013
Research and development	$	410,150	$	39,638
General and administrative		691,937		106,328
Total stock-based compensation expense	$	1,102,087	$	145,966

Summary of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following at December 31, 2014 and 2013:

	December 31,
	2014		2013
Stock options issued and outstanding		683,500		624,750
Authorized for future option grants		188,370		8,500
Warrants to purchase common stock		118,881		106,000
Authorized for employee stock purchase plan		52,706		30,000
Total common stock reserved for future issuance		1,043,457		769,250