8. 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)	2018		2017		2018		2017
Research and development	$	552	$	615	$	1,765	$	1,772
General and administrative		928		1,467		5,085		4,393

Stock-based compensation expense	$	1,480	$	2,082	$	6,850	$	6,165

The Company granted an aggregate of 300,500 and 506,000 stock options during the three and nine months ended September 30, 2018 with a weighted-average grant date fair value of $2.11 and $2.49 per share, respectively. The Company granted an aggregate of 593,500 and 859,000 stock options during the three and nine months ended September 30, 2017 with a weighted-average grant date fair value of $4.29 and $4.34 per share, respectively.

On February 15, 2018, the Company extended the contractual life of 751,667 fully vested stock options held by one officer of the Company by an additional 9 months. Additionally, on March 12, 2018, the Company extended the contractual life of 117,500 fully vested stock options held by a director. These extensions resulted in additional stock-based compensation expense of $481 thousand in the nine months ended September 30, 2018.

On September 18, 2018, the Company extended the contractual life of 92,500 fully vested stock options held by a director of the Company by approximately 9 months and 167,500 fully vested stock options held by another director of the Company by approximately 21 months. These extensions resulted in additional stock-based compensation expense of $117 thousand in the three and nine months ended September 30, 2018. Furthermore, the Company accelerated the vesting of 34,516 shares of restricted stock and recorded an adjustment of ($12) thousand in the three and nine months ended September 30, 2018.

The Company recognizes forefeitures as they occur. For the three months ended September 30, 2018 and 2017, 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,
	2018	2017
Risk-free interest rate	2.82 - 2.98%	1.88 - 2.01%
Expected life in years	6	6
Expected volatility	82.27 - 83.08%	80.82 - 80.95%
Expected dividend yield	0	0

Stock option activity under the Company’s stock option plan for the nine months ended September 30, 2018 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, 2017		3,852,135		$	5.12
Granted		506,000			3.50
Exercised		(104,167	)		2.30
Cancelled		(184,500	)		5.77

Outstanding, September 30, 2018		4,069,468		$	5.24		6.17	$	576

Options exercisable, September 30, 2018		2,924,501		$	5.13		4.98	$	498

Options exercisable, December 31, 2017		2,925,502		$	5.12		5.58	$	1,152

Options available for future grant		5,053,295

At September 30, 2018, total unrecognized compensation costs related to unvested stock options outstanding amounted to $4.1 million. The cost is expected to be recognized over a weighted-average period of 1.55 years.

In September 2017, the Company issued a stock option award as an inducement grant for the purchase of an aggregate of 500,000 shares of the Company’s common stock, outside of the 2012 Plan, at an exercise price of $6.19 per share. The inducement grant is excluded from the option activity table above.

A summary of the status of unvested restricted stock for the nine months ended September 30, 2018 is as follows:


	Number of Shares			Weighted-Average Grant Date Fair Value
Non-vested, December 31, 2017		1,808,559		$	5.74
Granted		—			—
Vested		(573,340	)		7.61
Cancelled		(70,867	)		5.07

Non-vested, September 30, 2018		1,164,352		$	4.85

At September 30, 2018, total unrecognized compensation costs related to unvested restricted stock outstanding amounted to $3.5 million. The cost is expected to be recognized over a weighted-average period of 1.48 years.