8.Stock award plan

On March 5, 2013, the Company’s Board of Directors approved the 2013 Stock Incentive Plan, which provides for the granting of stock option awards, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards in the aggregate of 739,937 shares of common stock. On March 5, 2013, the Board approved a grant of 735,324 shares of restricted stock and 4,613 stock options. There are no additional shares available for issuance under this plan.

In May 2013, the Company’s Board of Directors and stockholders increased by 2,500,000 the number of shares authorized under the 2009 Equity and Long Term Incentive Plan, which provides for the granting of stock option awards, restricted stock awards, and other stock-based and cash-based awards.

In May 2013, the Company’s Board of Directors and stockholders approved the 2013 Long Term Incentive Plan, which became effective upon the closing of the Company’s IPO. The 2013 Long Term Incentive Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards and other stock-based awards. The number of shares of common stock reserved for issuance under the 2013 Long Term Incentive Plan is the sum of (1) 238,427 shares of common stock available for issuance under the Company’s 2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan, (2) the number of shares (up to 3,040,444 shares) equal to the sum of the number of shares of common stock subject to outstanding awards under the Company’s 1998 Employee, Director and Consultant Stock Option Plan, 2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right plus (3) an annual increase, to be added on the first day of each fiscal year until the expiration of the 2013 Long Term Incentive Plan, equal to the lowest of 2,500,000 shares of common stock, 4% of the number of shares of common stock outstanding on the first day of the fiscal year and an amount determined by the Company’s Board of Directors.

From January 1, 2015 through September 30, 2015, the Company issued a total of 2,086,300 stock options to various employees. Of those, 691,100 were inducement grants for non-statutory stock options. The inducement grant awards were made pursuant to the NASDAQ inducement grant exception as a material component of our new hires’ employment compensation.

A summary of stock option activity is as follows:

	Number of options		Weighted- average exercise price		Weighted- average remaining contractual term	Aggregate intrinsic value
						(in thousands)
Outstanding at December 31, 2014	3,432,972		$	25.00
Granted	2,086,300		$	52.04
Exercised	(654,748	)	$	13.27
Forfeited	(74,366	)	$	42.46
Expired	(1,894	)	$	285.48

Outstanding at September 30, 2015	4,788,264		$	37.64	8.58 years	$	20,137

Vested or Expected to vest at September 30, 2015	4,497,155		$	37.00	8.56 years	$	19,018

Exercisable at September 30, 2015	1,132,683		$	32.21	7.89 years	$	10,312

The fair value of grants made in the nine months ended September 30, 2015 was contemporaneously estimated on the date of grant using the following assumptions:

		Nine months ended September 30, 2015
Risk-free interest rate		1.49% — 2.01%
Expected volatility		67%-69%
Expected term		5.50 — 6.11 years

The Company assumed no expected dividends for all grants. The weighted average grant date fair value of options granted during the nine month period ended September 30, 2015 was $32.32 per share.

The Company uses the “simplified method” to determine the expected term of options. Under this method, the expected term represents the average of the vesting period and the contractual term. The expected volatility of share options was estimated based on a historical volatility analysis of peers that were similar to the Company with respect to industry, stage of life cycle, size, and financial leverage. The risk-free rate of the option is based on U.S. Government Securities Treasury Constant Maturities yields at the date of grant for a term similar to the expected term of the option.

Restricted Stock Awards—Restricted stock awards are granted subject to certain restrictions, including in some cases service or time conditions (restricted stock). The grant-date fair value of restricted stock awards, which has been determined based upon the market value of the Company’s shares on the grant date, is expensed over the vesting period.

The following table summarizes information on the Company’s restricted stock:

	Restricted Stock
	Number of Shares		Weighted Average Grant Date Fair Value
January 1, 2015	718,400		$	10.72
Granted	—		$	—
Vested	(361,919	)	$	10.60
Forfeited	(3,346	)	$	10.82

Unvested at September 30, 2015	353,135		$	10.85

The Company recorded share-based compensation expense in the statement of operations as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014

Research and development	$	3,828	$	2,363	$	12,452	$	6,517
General and administrative	4,226		2,258		13,678		6,088

Total	$	8,054	$	4,621	$	26,130	$	12,605

As of September 30, 2015, there was approximately $75.2 million of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the 2009 Equity and Long Term Incentive Plan, 2013 Long Term Incentive Plan and equity awards made pursuant to the NASDAQ inducement grant exception for new hires. This cost is expected to be recognized as share-based compensation expense over the weighted average remaining service period of approximately 2.9 years.