8. Stock Compensation

2013 Stock Option and Incentive Plan

In May 2015, the Company’s stockholders approved the amended and restated 2013 Stock Option and Incentive Plan (as amended, the “2013 Plan”). The number of shares of common stock available for awards under the 2013 Plan was set to 2,975,000 shares, plus (i) shares of common stock that are forfeited, cancelled, held back upon the exercise or settlement of an award to cover the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of common stock or otherwise terminated (other than by exercise) under the 2013 Plan and the Company’s 2008 Incentive Stock Option and Restricted Stock Plan are added back to the shares of common stock available for issuance under the 2013 Plan, and (ii) on January 1, 2016, and each January 1, thereafter, the number of shares of common stock reserved and available for issuance under the 2013 Plan will be cumulatively increased by 2.5% of the number of shares of common stock outstanding on the immediately preceding December 31, or such lesser number of shares of common stock determined by the compensation committee.

The 2013 Plan provides for the granting of stock options, stock appreciation rights, restricted stock awards, restricted stock units, unrestricted stock awards, cash-based awards, performance share awards and dividend equivalent rights. The Company incurs stock-based compensation expense related to stock options and restricted stock units (“RSUs”). The fair value of RSUs is determined by the closing market price of the Company’s common stock on the date of grant. The fair value of stock options is calculated using a Black-Scholes option pricing model. The Company accounts for stock-based compensation in accordance with the provisions of ASC 718, Compensation—Stock Compensation. Accordingly, compensation costs related to equity instruments granted are recognized over the requisite service periods of the awards on a straight-line basis at the grant-date fair value, taking into account estimated forfeitures.

The following table summarizes the activity relating to the Company’s options to purchase common stock for the nine months ended September 30, 2016:

	Number of Options		Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
						(in thousands)
Outstanding at December 31, 2015	2,662,862		$	32.42	8.36	$	16,433
Granted	611,250		$	15.89
Forfeited or expired	(88,168	)	$	29.94
Exercised	(27,757	)	$	1.61

Outstanding at September 30, 2016	3,158,187		$	29.56	7.91	$	6,218

The following table summarizes information about the Company’s stock option plan as of September 30, 2016:

	Number of Options	Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
					(in thousands)
Vested and expected to vest at September 30, 2016	3,057,211	$	29.39	7.87	$	6,137

Exercisable at September 30, 2016	1,558,436	$	24.74	7.08	$	4,955

During the three and nine months ended September 30, 2016, the Company recognized approximately $3.6 million and $12.1 million, respectively, of stock-based compensation related to stock options. During the three and nine months ended September 30, 2015, the Company recognized approximately $3.3 million and $8.3 million, respectively, of stock-based compensation related to stock options. As of September 30, 2016, there was approximately $30.6 million of unrecognized stock-based compensation expense related to unvested options, adjusted for forfeitures, which will be recognized over a weighted-average period of approximately 2.5 years.

The following table summarizes the activity relating to the Company’s RSUs for the nine months ended September 30, 2016:

	Number of RSUs		Weighted-Average Fair Value Per Share

Outstanding and unvested at December 31, 2015	25,000		$	57.54
Granted	3,000		$	15.97
Forfeited or expired	(3,000	)	$	15.97
Vested	(7,187	)	$	57.54

Outstanding and unvested at September 30, 2016	17,813		$	57.54

During the three and nine months ended September 30, 2016, the Company recognized approximately $0.1 million and $0.3 million, respectively, of stock-based compensation expense recognized related to RSUs. During the three and nine months ended September 30, 2015, the Company recognized less than $0.1 million of stock-based compensation expense recognized related to RSUs. As of September 30, 2016, there was approximately $0.9 million of unrecognized stock-based compensation expense related to unvested RSUs, adjusted for forfeitures, which will be recognized over a weighted-average period of approximately 2.8 years.