The Company considers financial instruments which do not have fixed settlement provisions to be derivative instruments. The common stock purchase warrants issued with the Company’s August 13, 2007 private placement, and the common stock purchase warrants issued to the placement agent in the transaction, do not have fixed settlement provisions because their exercise prices may be lowered if the Company issues securities at lower prices in the future. The Company was required to include the reset provisions in order to protect the warrant holders from the potential dilution associated with future financings. At issuance, the warrants were recognized as equity instruments and have since been re-characterized as derivative liabilities. Accordingly, the warrant obligations are adjusted to fair value at the end of each reporting period with the change in value reported in the statement of operations. Such fair values were estimated using the Black-Scholes valuation model. Although the Company determined the common stock warrants include an implied down-side protection feature, it performed a Monte-Carlo simulation and concluded that the value of the feature is de minimis between the two models and the use of the Black-Scholes valuation model is considered to be a reasonable method to value the warrants.

The derivative liability related to warrants without fixed settlement provisions were valued using the Black-Scholes option valuation model and the following assumptions on the following dates:

Warrants Issued in Conjunction with the Company’s April 22, 2012 Registered Direct Offering

The Company deems financial instruments which require net-cash settlement as either an asset or a liability. The common stock purchase warrants issued in conjunction with the Company’s April 22, 2012 registered direct offering originally contained a net-cash settlement feature which gave the warrant holder the right to net-cash settlement in the event certain transactions occur. Pursuant to the terms of the original warrants, if such a transaction occurred the warrant holder would be entitled to a net-cash settlement value calculated using the Black-Scholes valuation model using an expected volatility equal to the greater of 100% and the 100 day volatility obtained from the HVT function on Bloomberg, an expected term equal to the remaining term of the warrants, and applicable risk-free interest rate corresponding to the U.S. Treasury. On October 29, 2012, the Company entered into a side letter agreement with the holders of the warrants and the parties agreed to amend the terms of the warrants to eliminate the net-cash settlement feature contained in the warrants and extended the expiration date of the warrants by two years. Subsequent to the execution of the side letter agreement, the Company adjusted the fair value of the warrants to the modified fair value and recorded a $298,000 gain. Additionally, the Company recorded a $382,000 loss due to the incremental fair value adjustment resulting from the modification of the warrants. Subsequent to the Company’s entry into the side letter agreement, the Company reclassified the fair value of the warrants of $1,636,000 from a liability to additional paid-in capital as classified on the accompanying December 31, 2012 condensed consolidated balance sheet.

The derivative liability relating to the warrants with net-cash settlement provisions were valued using the Black-Scholes option valuation model and the following assumptions on the following dates:

The Company will continue to adjust the derivative liabilities for changes in fair value until the earlier of the exercise, at which time the liability will be reclassified to stockholders’ equity, or expiration of the warrants.

The following table sets forth a summary of the changes in the fair value of our Level 3 financial liabilities that are measured at fair value on a recurring basis: