Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2015

Summary of Reserved Shares of Common Stock for Future Issuance

The Company has reserved for future issuance the following number of shares of common stock:

	December 31,
	2015		2014
Unvested restricted common stock		216,716		422,145
Common stock options and RSU's outstanding		2,231,057		1,526,346
Shares available for issuance under the 2014 Plan (1)		1,318,732		1,549,154
Shares available for issuance under the ESPP		440,304		262,500
Total		4,206,809		3,760,145

⁽¹⁾ On January 1, 2016, the shares reserved for future grants under the 2014 Plan increased by 986,800 shares pursuant to the 2014 Plan Evergreen Provision.

⁽²⁾ On February 28, 2016, the shares reserved for future issuance under the ESPP increased by 379,430 shares pursuant to the ESPP Evergreen Provision.

Schedule of Assumptions Used in Black-Scholes Option Pricing Model

The assumptions used in the Black-Scholes pricing model to estimate the grant date fair value of options granted to employees are as follows:

	Year ended December 31,
	2015		2014
Risk-free interest rate	1.44% - 1.95%		1.63% - 2.06%
Dividend yield		0.00%		0.00%
Volatility	62.47% - 81.25%		67.97% - 77.00%
Expected term (years)	5.51 - 6.25		6.25

Schedule of Stock Option Activity

The following table summarizes the Company’s stock option activity:

	Shares			Weighted-Average Exercise Price		Weighted-Average Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding,    December 31, 2014		1,526,349		$	7.57			$	11,523,531
Granted		992,050		$	9.81
Exercised		(218,674	)	$	0.60			$	2,047,507
Forfeited		(93,090	)	$	12.96			$	107,384
Expired/cancelled		—
Outstanding,    December 31, 2015		2,206,635		$	9.04		8.20	$	13,114,811
Options exercisable,    December 31, 2015		610,696		$	6.20		6.63	$	5,620,564
Expected to vest,    December 31, 2015		1,958,808		$	9.71		8.56	$	10,737,600

Schedule of Restricted Stock Activity

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

	Shares			Weighted-Average Grant Date Fair Value
Unvested balance, December 31, 2014		422,145		$	8.39
Granted		-
Vested		(169,376	)	$	8.87
Forfeited		(36,053	)	$	8.93
Outstanding, December 31, 2015		216,716		$	7.97

Compensation Cost Related to Share-Based Awards

Compensation Expense Summary

The Company has recognized the following compensation cost related to share-based awards:

	Year ended December 31,
	2015		2014
	(in thousands)
Research and development	$	2,079	$	2,766
General and administrative		2,635		3,244
Total	$	4,714	$	6,010

Schedule of Compensation Expense by Type of Award

	Year ended December 31,
	2015		2014
	(in thousands)
Stock options	$	3,660	$	1,925
Restricted stock		909		4,085
Restricted stock units		62		—
Employee stock purchase plan		83		—
Total	$	4,714	$	6,010

Restricted Stock Units

Schedule of Restricted Stock Activity

	Shares			Weighted-Average Grant Date Fair Value
Unvested balance, December 31, 2014		-		$	-
Granted		27,875		$	11.15
Vested		-		$	-
Forfeited		(3,450	)	$	11.15
Outstanding, December 31, 2015		24,425		$	11.15