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 a binomial valuation model.

Liability-Classified Warrants

In connection with a 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 warrants had a 5-year term and expired in December 2014. Subject to certain exceptions, these warrants provided anti-dilution protection in the event the Company should subsequently issue common stock or common stock equivalents at a price less than the exercise price of the warrants then in effect.

The Company assessed whether the Warrants required accounting as derivatives. The Company determined that the warrants were not indexed to the Company’s own stock in accordance with FASB Accounting Standards Codification, Derivatives and Hedging (Topic 815). As such, the Company concluded the warrants did not meet the scope exception for determining whether the instruments required accounting as derivatives and should be classified in liabilities.

In December 2014, the Company recognized a gain of $195 thousand on the expiration of these liability-classified warrants.

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 had an exercise price of $2.04 per share and a 5-year term. The fair value of the warrants was estimated at $4.2 million using a Black-Scholes model with the following assumptions: expected volatility of 105%, risk free interest rate of 2.41%, expected life of 5 years and no dividends. The fair value of the warrants was recorded in the equity section of the Company’s balance sheet.

During 2014, 4,004,907 warrants were exercised for 3,725,277 shares of common stock. Of these warrants, 2,249,062 were equity-classified warrants and 1,755,845 were liability-classified warrants. Additionally, 12,329 equity-classified warrants and 6,479,231 liability-classified warrants expired without being exercised.

All remaining warrants expired during the year ended December 31, 2014.