Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Summary of stock option activity

A summary of stock option activity during the year ended December 31, 2015 is as follows:

					Weighted-
					Average
			Weighted-		Remaining
			Average		Contractual	Aggregate
	Number		Exercise		Term	Intrinsic
	of Options		Price		(in years)	Value
Outstanding at December 31, 2014		1,652,882	$	10.03	8.9		1,628
Granted		2,269,247		7.50
Exercised		(130,920)		2.71
Cancelled		(177,782)		7.83
Outstanding at December 31, 2015		3,613,427	$	8.81	8.8	$	485
Vested and expected to vest at: December 31, 2015		3,438,732	$	8.90	8.8	$	482
Exercisable at: December 31, 2015		699,459	$	14.73	7.7	$	316
Weighted average grant-date fair value of options granted during the period	$	4.86
Cash received upon exercise of options	$	355

Summary of restricted stock activity

A summary of the restricted stock activity during the year ended December 31, 2015 is as follows:

		Weighted-
	Restricted	Average Grant
	Stock	Date Fair Value
Nonvested at December 31, 2014	13,259	$	5.08
Granted	—
Vested	(13,259)		5.08
Cancelled	—		—
Nonvested at December 31, 2015	—	$	—

Summary of the activity of nonvested RSUs

A summary of the activity of nonvested restricted stock units (“RSUs”) for the year ended December 31, 2015 is as follows:

				Weighted-
				Average
	Number		Weighted-	Remaining
	of		Average	Contractual		Aggregate
	Restricted		Grant Date	Term		Intrinsic
	Stock Units		Fair Value	(in years)		Value
Nonvested at December 31, 2014	—	$	—	—	$	—
Granted	126,621		10.53			—
Vested	—		—	—
Cancelled	(2,179)		10.53	—
Nonvested at December 31, 2015	124,442	$	10.53	2.9	$	385
Vested and expected to vest at:
December 31, 2015	116,964	$	10.53	2.9	$	361
Exercisable at:
December 31, 2015	—	$	—	—	$	—

Stock Options

Summary of range of assumptions used in the Black-Scholes pricing model for grants and grants issued or accelerated in connections with the Merger

During the years ended December 31, 2015 and 2014, respectively, the range of assumptions used in the Black-Scholes pricing model for new grants and grants issued or accelerated in connection with the Merger were as follows:

	Year Ended December 31,
	2015	2014
Risk-free interest rate	1.48% - 1.96%	1.80% - 2.09%
Expected volatility	61.40% - 89.05%	63.96% - 66.07%
Expected term (in years)	6.00	6.00
Expected dividend yield	0.0%	0.0%

Employee Stock Purchase Plan

Summary of range of assumptions used in the Black-Scholes pricing model for grants and grants issued or accelerated in connections with the Merger

The fair value of the option component of the shares purchased under the ESPP was estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions:

	Year Ended December 31,
	2015
Risk-free interest rate	0.42%
Expected volatility	76.01%
Expected term (in years)	0.50
Expected dividend yield	0.0%