10. Stock-Based Compensation

The Company recognized stock-based compensation expense on all employee and non-employee awards as follows:


	For the three months ended September 30,				For the nine months ended September 30,
(in thousands)	2015		2014		2015		2014
Research and development	$	264	$	340	$	874	$	1,126
General and administrative		1,213		808		5,180		2,457

Stock-based employee compensation expense	$	1,477	$	1,148	$	6,054	$	3,583

The Company granted an aggregate of 203,000 and 254,800 stock options during the three and nine months ended September 30, 2015 with a weighted-average grant date fair value of $8.49 and $8.10 per share, respectively. The Company granted an aggregate of 10,000 and 114,300 stock options during the three and nine months ended September 30, 2014 with a weighted-average grant date fair value of $2.29 and $3.15 per share, respectively.

On March 31, 2014, the Company extended the contractual life of 71,167 fully vested stock options held by one employee for an additional 9 months.

On March 31, 2014, the Company extended the contractual life of 33,333 fully vested stock options and 66,667 unvested stock options held by one employee for an additional 6 months.

On September 8, 2014, the Company extended the contractual life of 82,834 fully vested stock options and 23,333 unvested stock options held by one employee for an additional 3 months.

On September 15, 2014, the Company extended the contractual life of 39,167 fully vested stock options and 113,333 unvested stock options held by one employee for an additional 27 months.

On June 17, 2015, the Company extended the contractual life of 157,500 fully vested stock options held by a director for an additional 48 months.

The additional expense for the above modifications totaled $325 thousand for the year ended December 31, 2014 and $201 thousand for the nine months ended September 30, 2015.

For the three months ended September 30, 2015 and 2014, the fair value of stock options was estimated on the date of grant using a Black-Scholes option valuation model with the following assumptions:


	For the three months ended September 30,
	2015	2014
Risk-free interest rate	1.66 - 1.93%	2.03%
Expected life in years	6	6
Expected volatility	80.01 - 81.17%	92.36%
Expected dividend yield	0	0

Stock option activity under the Company’s stock option plan for the nine months ended September 30, 2015 is as follows:


(in thousands, except share and per share data)	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding, December 31, 2014		6,505,663		$	4.07

Granted		254,800			11.61
Exercised		(2,938,161	)		3.96
Cancelled		(167,167	)		4.13

Outstanding, September 30, 2015		3,655,135		$	4.69		7.09	$	16,481

Vested and unvested expected to vest at September 30, 2015		3,579,108		$	4.09		5.59	$	16,139

Options exercisable, September 30, 2015		1,886,001		$	4.09		5.59	$	9,277

Options exercisable, December 31, 2014		3,781,162		$	4.10		5.80	$	4,130

Options available for future grant		3,441,950

At September 30, 2015, total unrecognized compensation costs related to unvested stock options outstanding amounted to $5.1 million. The cost is expected to be recognized over a weighted-average period of 1.59 years.

During the three and nine months ended September 30, 2015, the Company issued 4,186 and 1,054,186 shares of restricted stock to employees and directors. The employee grants vest ratably in annual installments over three years, commencing on the first anniversary of the grant date and the director grant vests in total on December 31, 2015. No shares of restricted stock were issued during the three or nine months ended September 30, 2014.

A summary of the status of unvested restricted stock for the nine months ended September 30, 2015 is as follows:


	Number of Shares			Weighted-Average Grant Date Fair Value
Non-vested, December 31, 2014		144,508		$	4.70
Granted		1,054,186			9.36
Vested		(70,991	)		4.62
Cancelled		—			—

Non-vested, September 30, 2015		1,127,703		$	9.06

At September 30, 2015, total unrecognized compensation costs related to unvested restricted stock outstanding amounted to $8.6 million. The cost is expected to be recognized over a weighted-average period of 1.83 years.