Note 10. Stock-Based Compensation

We currently grant stock-based compensation under three equity incentive plans (2004, 2006 and 2013 Equity Incentive Plans) approved by the Company’s stockholders and one plan adopted in 2012 pursuant to NASDAQ Listing Rule 5635(c)(4) concerning inducement grants for new employees (our “2012 Commencement Incentive Plan”). As of December 31, 2013, we had 8,553,608 shares available to grant under the above mentioned plans. At our annual stockholders meeting held on June 12, 2007, our stockholders approved an amendment to our 2006 Equity Incentive Plan to provide for an annual increase in the number of shares of common stock available for issuance under the plan each January 1 (beginning January 1, 2008) equal to 4% of the outstanding common shares as of that date. The amendment further provided an aggregate limit of 3,000,000 shares issuable pursuant to incentive stock option awards under the plan. At our annual stockholders meeting held on December 20, 2013, our stockholders approved our 2013 Equity Incentive Plan to grant stock-based compensation of up to an initial 6,000,000 shares, plus an increase of 4% per year of the outstanding number of shares of our common stock beginning in January 1, 2015. Under the three stockholder-approved plans we may grant incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock, restricted stock units, 401(k) Plan employer match in form of shares and performance-based shares to our employees, directors and consultants, at prices determined by our Board of Directors. Incentive stock options may only be granted to employees under these plans with a grant price not less than the fair market value on the date of grant. Under our 2012 Commencement Inducement Plan, we may only award options, restricted stock units and other equity awards to newly hired employees and newly engaged directors, in each case as allowed by NASDAQ listing requirements.

Generally, stock options and restricted stock units granted to employees have a maximum term of ten years, and vest over a four year period from the date of grant; 25% vest at the end of one year, and 75% vest monthly over the remaining three-year service period. We may grant options and restricted stock units with different vesting terms from time to time. Upon employee termination of service, any unexercised vested option will be forfeited three months following termination or the expiration of the option, whichever is earlier.

Our stock-based compensation expense for the last three fiscal years was as follows:


	2013		2012		2011
Research and development expense	$	1,219,308	$	1,280,298	$	1,680,431
General and administrative expense		1,389,362		1,597,836		1,580,506

Total stock-based compensation expense and effect on net loss	$	2,608,670	$	2,878,134	$	3,260,937

As of December 31, 2013, we have approximately $4,275,000 of total unrecognized compensation expense related to unvested awards granted under our various share-based plans that we expect to recognize over a weighted-average period of 3.0 years.

The fair value of options granted is estimated as of the date of grant using the Black-Scholes option pricing model and expensed on a pro-rata straight-line basis over the period in which the stock options vest. The Black-Scholes option pricing model requires certain assumptions as of the date of grant. The weighted-average assumptions used for the last three fiscal years are as follows:


	2013			2012			2011
Expected term (years)(1)		5.1			6.4			7.4
Risk-free interest rate(2)		1.2	%		1.4	%		2.7	%
Expected volatility(3)		89.3	%		78.4	%		79.7	%
Expected dividend yield(4)		0	%		0	%		0	%

(1)

The expected term represents the period during which our stock-based awards are expected to be outstanding. We estimated this amount based on historical experience of similar awards, giving consideration to the contractual terms of the awards, vesting requirements, and expectation of future employee behavior, including post-vesting terminations.

(2)	The risk-free interest rate is based on U.S. Treasury debt securities with maturities close to the expected term of the option as of the date of grant.

(3)	Expected volatility is based on historical volatility over the most recent historical period equal to the length of the expected term of the option as of the date of grant.

(4)	We have neither declared nor paid dividends on any share of common stock and we do not expect to do so in the foreseeable future.

At the end of each reporting period, we estimate forfeiture rates based on our historical experience within separate groups of employees and adjust the stock-based compensation expense accordingly.

A summary of our stock option activity and related information for the last three fiscal years is as follows:


	Outstanding Options
	Number of Shares			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term		Aggregate Intrinsic Value(1)
Balance at December 31, 2010		1,098,241		$	20.20		6.1	$	398,219
Granted		3,750		$	7.30
Exercised		(1,692	)	$	1.41			$	11,293
Cancelled (forfeited and expired)		(224,801	)	$	20.22

Balance at December 31, 2011		875,498		$	20.13		5.5	$	—
Granted		—
Exercised		(3,629	)	$	1.00			$	4,319
Cancelled (forfeited and expired)		(424,510	)	$	20.86

Balance at December 31, 2012		447,359		$	19.59		5.1	$	2,175
Granted		—
Exercised		(3,452	)	$	1.00			$	2,214
Cancelled (forfeited and expired)		(15,649	)	$	13.06

Balance at December 31, 2013		428,258		$	19.97		4.3	$	—

Exercisable at December 31, 2013		409,792		$	20.42		4.2	$	—

Vested and expected to vest(2)		426,027		$	20.02		4.3	$	—

(1)

Aggregate intrinsic value represents the value of the closing price per share of our common stock on the last trading day of the fiscal period in excess of the exercise price multiplied by the number of options outstanding or exercisable, except for the “Exercised” line, which uses the closing price on the date exercised.

(2)	Number of shares includes options vested and those expected to vest net of estimated forfeitures.

No options were granted in 2013 and 2012.The estimated weighted average fair value per share of options granted was approximately $5.31 in 2011, based on the assumptions in the Black-Scholes model discussed above. Total intrinsic value of options exercised at time of exercise was approximately $2,000 in 2013, $4,000 in 2012, and $11,000 in 2011.

The following is a summary of changes in unvested options:


Unvested Options	Number of Options			Weighted Average Grant Date Fair Value
Unvested options at December 31, 2012		64,503		$	8.67
Granted		—			—
Vested		(45,564	)	$	8.91
Cancelled		(473	)	$	7.82

Unvested options at December 31, 2013		18,466		$	8.11

The estimated fair value of options vested were approximately $406,000 in 2013, $627,000 in 2012 and $1,545,000 in 2011.

The following table presents weighted average exercise price and remaining term information about significant option groups outstanding at December 31, 2013:


Options Outstanding at December 31, 2013
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Term (Yrs.)		Weighted Average Exercise Price		Aggregate Intrinsic Value at December 31, 2013
Less than $10.00		4,050		7.3	$	7.42	$	—
$10.00 - $19.99		250,949		5.3	$	12.65		—
$20.00 - $29.99		117,459		3.1	$	23.22		—
$30.00 - $39.99		19,800		1.9	$	36.46		—
$40.00 - $49.99		5,500		1.7	$	46.51		—
$50.00 - $59.99		30,500		1.7	$	53.94		—

		428,258		4.3	$	19.97	$	—


Vested Options Outstanding at December 31, 2013
Range of Exercise Prices	Number Outstanding		Weighted Average Exercise Price
Less than $10.00		2,677	$	7.45
$10.00 - $19.99		233,856	$	12.81
$20.00 - $29.99		117,459	$	23.22
$30.00 - $39.99		19,800	$	36.46
$40.00 - $49.99		5,500	$	46.51
$50.00 - $59.99		30,500	$	53.94

		409,792	$	20.42

Restricted Stock Units

We have granted restricted stock units (RSUs) to our directors and to certain employees which entitle the holders to receive shares of our common stock upon vesting of the RSUs. The fair value of restricted stock units granted are based upon the market price of the underlying common stock as if it were vested and issued on the date of grant.

A summary of our restricted stock unit activity for the year ended December 31, 2013 is as follows:


	Number of RSUs			Weighted Average Grant Date Fair Value
Outstanding at January 1, 2013		1,534,200		$	2.10
Granted(1)		2,421,965		$	1.80
Vested and exercised		(565,883	)	$	3.37
Cancelled		(64,000	)	$	1.61

Outstanding at December 31, 2013		3,326,282		$	1.68

(1)

11,765 of these restricted stock units vested on the date of grant. 55,000 of these restricted stock units vest and convert into shares of our common stock after one year from the date of grant. 2,355,200 of these restricted stock units vest and convert into shares of our common stock over a four year period from the date of grant: one-fourth of the award will vest on each grant date anniversary following the grant.

Stock Appreciation Rights

In July 2006, we granted cash-settled Stock Appreciation Rights (SARs) to certain employees that give the holder the right, upon exercise, to the difference between the price per share of our common stock at the time of exercise and the exercise price of the SARs.

The SARs have a maximum term of ten years with an exercise price of $20.00, which is equal to the market price of our common stock at the date of grant. The SARs vest 25% on the first anniversary of the grant date and 75% vest monthly over the remaining three-year service period. All of the outstanding SARs as of December 31, 2013 are fully vested. Compensation expense is based on the fair value of SARs which is calculated using the Black-Scholes option pricing model.

The stock-based compensation expense and liability are re-measured at each reporting date through the earlier of date of settlement or forfeiture of the SARs.

The following is a summary of the changes in our outstanding SARs for the last three fiscal years:


	2013				2012					2011
	Number		Weighted Average Exercise Price		Number			Weighted Average Exercise Price		Number			Weighted Average Exercise Price
Outstanding at January 1,		110,593	$	20.00		115,187		$	20.00		135,409		$	20.00
Granted		—		—		—			—		—			—
Exercised		—		—		—			—		—			—
Forfeited		—				(4,594	)				(20,222	)

Outstanding at December 31,		110,593	$	20.00		110,593		$	20.00		115,187		$	20.00

Exercisable at December 31,		110,593	$	20.00		110,593		$	20.00		115,187		$	20.00

For the year ended December 31, 2013, the re-measured liability related to the SARs reduced compensation expense by approximately $11,000.The total compensation expense related to SARs was approximately $18,000 in 2012 and for the year ended December 31, 2011, the re-measured liability related to the SARs reduced compensation expense by approximately $344,000. The resulting effect on net loss and net loss per share attributable to common stockholders is not likely to be representative of the effects in future periods, due to changes in the fair value calculation which is dependent on the stock price, volatility, interest and forfeiture rates, additional grants and subsequent periods of vesting. We will continue to recognize compensation cost each period, which will be the change in fair value from the previous period through the earlier date of settlement or forfeiture of the SARs.