Stock-Based Compensation

3 Months Ended

Mar. 31, 2016

3.	Stock-Based Compensation

Following is the stock-based compensation expense related to common stock options, common stock, restricted common stock and common stock warrants:


	Three Months Ended March 31,
	2016		2015
Research and development	$	254	$	317
General and administrative		969		618


Total stock-based compensation expense	$	1,223	$	935

The following table summarizes the stock option activity in the Company’s equity incentive plans, including non-plan grants to Company executives, from December 31, 2015 through March 31, 2016:


	Shares			Weighted Average Exercise Price
Outstanding, December 31, 2015		3,342,325		$	5.70
Granted		277,500			1.37
Exercised		—			—
Options forfeited/cancelled		(18,520	)		6.48


Outstanding, March 31, 2016		3,601,305		$	5.36

As of March 31, 2015, there was $1,621,000 of unrecognized compensation related to 920,468 unvested options, which is expected to be recognized over a weighted–average period of approximately 2.0 years. The weighted-average grant date fair value for options granted during the three months ended March 31, 2016 and 2015 was $1.05 and $2.78, respectively. The Company granted 277,500 stock options during the three months ended March 31, 2016, of which 69,375 options vested upon grant with the remaining 208,125 options vesting over 3 years. Approximately $73,000 of non-cash, stock-based compensation expense was recorded during the three months ended March 31, 2016 related to the options granted during the quarter that were vested upon the grant date.

The fair value of all other options granted is determined using the Black-Scholes option-pricing model. The following weighted average assumptions were used:


	Three Months Ended March 31,			Three Months Ended March 31,
	2016			2015
Risk-free interest rate		1.7	%		1.64	%
Expected life of the options		6.0 years			6.0 years
Expected volatility of the underlying stock		94	%		104	%
Expected dividend rate		0	%		0	%

The following table summarizes the restricted stock grant activity in the Company’s equity incentive plans from December 31, 2015 through March 31, 2016:


	Shares
Outstanding, December 31, 2015		754,605
Granted		—
Exercised		—
Options forfeited/cancelled		—


Outstanding, March 31, 2016		754,605

On March 12, 2015, the Company granted 81,352 shares of restricted stock to non-employee directors as a component of their compensation. A total of 77,784 shares were issued to seven directors representing non-cash compensation cost of $280,000 which will be recognized on a straight-line basis from the grant date through May 21, 2016, when the restricted shares will vest in full. A total of 3,568 shares were issued to two directors, who were not nominated for reelection, representing non-cash compensation cost of $12,845 that will be recognized on a straight-line basis from the grant date through May 21, 2016, when the restricted shares will vest in full.