9. Warrants

The Company has issued both warrants that are accounted for as liabilities and warrants that are accounted for as equity instruments.

The Company follows accounting standards that provide guidance in assessing whether an equity-issued financial instrument is indexed to an entity’s own stock for purposes of determining whether a financial instrument should be treated as a derivative and classified as a liability. Accounting standards require that liability classified warrants be recorded at their fair value at each financial reporting period and the resulting gain or loss be recorded as other income (expense) in the Statements of Operations. Fair value is measured using the binomial valuation model.

In May 2005, the Company issued 419,786 warrants to placement agents for services performed in connection with the 2005 Offering, 11,083 of which were subsequently exercised. The remaining 408,703 warrants were originally valued at $1.6 million. Subject to certain exceptions, these warrants provide for anti-dilution protection should common stock or common stock equivalents be subsequently issued at a price less than the exercise price of the warrants then in effect, which was initially $4.75 per share. This provision was triggered in 2006 when stock was sold at $4.63 per share in the 2006 Offering. Accordingly, the warrants were re-priced at $4.69. The provision was triggered a second time with 2009 Private Placement when stock was sold at $1.825 per share and the warrants were subsequently re-priced at $4.25. The provision was triggered again with the Company’s December 2009 public offering when stock was sold at $3.10 per share and the warrants were subsequently re-priced at $3.93. Using a Black-Scholes model, the warrants were valued at $72 thousand on January 1, 2009, when the accounting standard was adopted. The reclassification attributed to adoption of the standard had the following cumulative effect on the Balance Sheets:


(in thousands)	Liabilities		Stockholders’ Equity
	Warrants		Warrants			Deficit Accumulated During the Development Stage
As reported on December 31, 2008	$	—	$	20,504		$	(85,061	)
Re-classification		72		(1,638	)		1,566

Balance on January 1, 2009	$	72	$	18,866		$	(83,495	)

The following Black-Scholes pricing assumptions were used at January 1, 2009:


	January 1, 2009
Risk-free interest rate		1.55	%
Expected life in years		3.42
Expected volatility		102	%
Expected dividend yield		0

Also, in connection with the December 2009 public offering, the Company issued warrants to purchase an aggregate of 8,206,520 shares of common stock (including the investor warrants and 464,520 warrants issued to the Underwriters). The investor warrants are exercisable immediately and the underwriter warrants exercisable six months after the date of issuance. The warrants have an exercise price of $4.02 per share and have a five year term. The fair value of the warrants was estimated at $22.9 million using a Black-Scholes model with the following assumptions: expected volatility of 105%, risk free interest rate of 2.14%, expected life of five years and no dividends.

The Company assessed whether the warrants require accounting as derivatives. The Company determined that the warrants were not indexed to the Company’s own stock in accordance with accounting standards codification Topic 815, Derivatives and Hedging. As such, the Company has concluded the warrants did not meet the scope exception for determining whether the instruments require accounting as derivatives and should be classified in liabilities.

On December 31, 2010, the liability-classified warrants were valued at $27.3 million using a Black-Scholes valuation model. The increase in the fair value of the warrant liabilities of $8.9 million for the year ended December 31, 2010 was credited to Other income, net in the Statements of Operations.

In December 2011, the Company changed from using a Black-Scholes pricing model to estimate the value of the liability-classified warrants to a Binomial/Monte Carlo pricing model. Accordingly, on December 31, 2011, the liability-classified warrants were valued at $19.4 million using the Binomial/Monte Carlo valuation model. The decrease in the fair value of the warrant liabilities of $7.6 million for the year ended December 31, 2011 was charged to Other income, net in the Statements of Operations. Additionally, $0.3 million of the decrease resulted from the exercise of warrants.

On December 31, 2012, the liability-classified warrants were valued at $13.0 million using a Binomial/Monte Carlo valuation model. The decrease in the fair value of the warrant liabilities of $6.1 million for the year ended December 31, 2012 was charged to Other income, net in the Statements of Operations.

The following pricing assumptions were used in the Binomial/Monte Carlo valuation model at December 31, 2012 and 2011 and the Black-Scholes valuation model at December 31, 2010:


	December 31, 2012	December 31, 2011	December 31, 2010
Risk-free interest rate	0.25%	0.05 - 0.35%	0.42 - 1.48%
Expected life in years	1.94	0.42 - 2.92	1.42 - 3.92
Expected volatility	70%	64 - 80%	75 - 116%
Expected dividend yield	0	0	0

Warrants accounted for as equity instruments include the following issuances:

During 2004, the Company issued warrants to purchase 62,621 shares of the Company’s common stock to Paramount as compensation for services rendered in connection with our entering into an option agreement with Southern Research Institute. In connection with the warrants issued, the Company recorded a charge of $251 thousand to general and administrative expense. The Company has estimated the fair value of such options using the Black-Scholes model, using an assumed risk-free rate of 3.93%, and expected life of 7 years, volatility of 134% and dividend yield of 0%.

In 2005, the Company issued performance warrants to purchase 50,000 shares of the Company’s common stock for services to be rendered to its investor relations consultant as compensation. In connection with the warrant issuance, 12,500 shares were exercisable immediately and the Company recorded a charge of $45 thousand to general and administrative expense in the year ended December 31, 2005. The Company has estimated the fair value of such options using the Black-Scholes model, using an assumed risk-free rate of 4.39%, an expected life of 5 years, volatility of 109%, and dividend yield of 0%. The remaining 37,500 warrants were cancelled in the year ended December 31, 2006 due to performance objectives not being obtained at the expiration of agreement.

In connection with the 2006 Offering completed on May 3, 2006, the Company issued warrants to purchase 2,397,392 shares of common stock to investors and 799,126 warrants to purchase common stock to the 2006 Placement Agents and their designees. The Company estimated the fair value of the warrants at $9.6 million and $3.5 million, respectively, using the Black-Scholes model, using an assumed risk-free rate of 5.01% and an expected life of 5 and 7 years, volatility of 100% and a dividend yield of 0%.

On February 23, 2007, as part of the 2007 Offering, the Company issued warrants to purchase 1,182,015 shares of common stock to investors and 177,302 warrants to purchase common stock to the placement agents in connection with the Company’s 2007 private placement, their designees and a previously-engaged financial consultant. The Company estimated the fair value of the warrants at $4.7 million and $709 thousand respectively, using the Black-Scholes model, using an assumed risk-free rate of 4.71% and an expected life of 5 years, volatility of 93% and a dividend yield of 0%.

In connection with its 2009 private placement, the Company issued warrants to purchase an aggregate of 2,910,954 shares of common stock (including 138,617 warrants issued to the placement agents) which were exercisable immediately. The warrants have an exercise price of $2.04 per share and have a five year term. The fair value of the warrants was estimated at $4,207 thousand using a Black-Scholes model with the following assumptions: expected volatility of 105%, risk free interest rate of 2.41%, expected life of five years and no dividends. The fair value of the warrants was recorded in the equity section of the balance sheet. In October 2009, 136,986 of these warrants were exercised.

During 2010, no new warrants were issued. However, 95,505 warrants were exercised for 39,225 shares of common stock. Of these warrants, 70,738 were equity-classified and 24,767 were liability-classified. Additionally, 12,500 equity-classified warrants expired without being exercised.

During 2011, no new warrants were issued. However, 2,516,968 warrants were exercised for 2,377,571 shares of common stock. Of these warrants, 2,351,417 were equity-classified and 165,551 were liability-classified. Additionally, 277,910 equity-classified warrants expired without being exercised.

During 2012, no new warrants were issued. However, 553,914 warrants were exercised for 259,660 shares of common stock. Of these warrants, 186,297 were equity-classified and 373,617 were liability-classified. Additionally, 1,359,317 equity-classified warrants and 579 liability-classified warrants expired without being exercised.

The following is a summary of warrants outstanding as of December 31, 2012.


Number of Warrants		Issued in Connection With	Exercise Price		Expiration Date
	706,708	Placement warrants for services performed	$	5.09	May 3, 2013
	2,399,739	Investor warrants	$	2.04	September 15, 2014
	40,298	Placement warrants for services performed	$	2.04	September 15, 2014
	7,726,000	Investor warrants	$	4.02	December 9, 2014
	324,709	Underwriter warrants for services performed	$	4.02	December 9, 2014

	11,197,454