Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2014

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock-Based Compensation Expense

The following stock-based compensation amounts were recognized for the periods indicated:


	Three Months Ended March 31,
	2014		2013

Research and development	$	316,533	$	92,555
General and administrative		295,071		52,317


Total stock-based compensation expense	$	611,604	$	144,872

Schedule of Fair Value Option Award Estimated on the Date of Grant Using the Black-Scholes Option-Pricing Model

The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model using the assumptions in the following table:


	Three Months Ended March 31,
	2014	2013

Expected dividend yield	0%	0%
Expected volatility	66.7% - 66.9%	50.9%
Risk-free interest rate	2.1% - 2.3%	1.2%
Expected term	6 - 6.25 years	7 years
Expected forfeiture rate	5%	5%

Schedule of Stock Option Activity


	Shares			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2013		3,200,958		$	4.90		6.9
Granted		30,449			35.41
Exercised		(34,274	)		0.95
Forfeited or expired		(8,281	)		3.36

Outstanding, March 31, 2014		3,188,852			5.24		6.8	$	72,258


March 31, 2014:
Exercisable		1,735,361			1.04		4.8		46,494
Vested and expected to vest		3,010,087			4.96		6.6		69,044