Stock-Based Compensation

3 Months Ended

Mar. 31, 2016

Stock-Based Compensation

7. Stock-Based Compensation

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

	For the three months ended March 31,
(in thousands)	2016		2015
Research and development	$	417	$	295
General and administrative		1,592		798
Stock-based compensation expense	$	2,009	$	1,093

The Company granted 20,000 stock options during the three months ended March 31, 2016 with a weighted-average grant date fair value of $3.88 per share. The Company granted 50,000 stock options during the three months ended March 31, 2015 with a weighted-average grant date fair value of $6.58 per share.

For the three months ended March 31, 2016 and 2015, 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 March 31,
	2016	2015
Risk-free interest rate	1.58 - 1.90%	1.63 - 1.64%
Expected life in years	6	6
Expected volatility	79.15 - 79.69%	85.48 - 86.81%
Expected dividend yield	0	0

Stock option activity under the Company’s stock option plan for the three months ended March 31, 2016 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, 2015		3,481,469		$	4.96
Granted		20,000			5.66
Exercised		(93,672	)		4.72
Cancelled		(3,333	)		3.28
Outstanding, March 31, 2016		3,404,464		$	4.97		6.77	$	9,874
Vested and unvested expected to vest at March 31, 2016		3,337,935		$	4.29		5.72	$	9,681
Options exercisable, March 31, 2016		2,122,328		$	4.29		5.72	$	6,666
Options exercisable, December 31, 2015		2,120,834		$	4.24		5.84	$	8,622
Options available for future grant		2,751,563

At March 31, 2016, total unrecognized compensation costs related to unvested stock options outstanding amounted to $4.4 million. The cost is expected to be recognized over a weighted-average period of 1.53 years.

A summary of the status of unvested restricted stock for the three months ended March 31, 2016 is as follows:

	Number of Shares		Weighted-Average Grant Date Fair Value
Non-vested, December 31, 2015		1,586,388	$	9.00
Granted		—		—
Vested		—		—
Cancelled		—		—
Non-vested, March 31, 2016		1,586,388	$	9.00

At March 31, 2016, total unrecognized compensation costs related to unvested restricted stock outstanding amounted to $10.8 million. The cost is expected to be recognized over a weighted-average period of 1.62 years.