Net Loss Per Share of Common Stock

Basic net loss per share of common stock is based on the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share of common stock is based on the weighted average number of shares outstanding during the period, adjusted to include the assumed conversion of certain stock options, restricted stock units (“RSUs”), and warrants for common stock.

Potentially dilutive securities are excluded from the calculation of loss per share if their inclusion is anti-dilutive. The following table shows the total outstanding securities considered anti-dilutive and therefore excluded from the computation of diluted net loss per share (in thousands):

For the three and nine months ended September 30, 2013 and 2012, all outstanding securities were considered anti-dilutive, and therefore the calculation of basic and diluted net loss per share was the same.

Cash and Cash Equivalents

At September 30, 2013, cash and cash equivalents consisted of demand deposits of $16.2 million and money market funds of $57.8 million with maturities of less than 90 days at the date of purchase. At December 31, 2012, cash and cash equivalents consisted of demand deposits of $7.8 million and money market funds of $37.5 million with maturities of less than 90 days at the date of purchase.

Short-term Investments

At September 30, 2013, the Company did not have short-term investments. At December 31, 2012, short-term investments consisted of U.S. treasury securities of $40.0 million with maturities of greater than 90 days and less than one year from the date of purchase.

Foreign Exchange Options

The Company holds debt and may incur revenue and expenses denominated in foreign currencies, which exposes it to market risk associated with foreign currency exchange rate fluctuations between the U.S. dollar and the Euro. The Company is required in the future to make principal and accrued interest payments in Euros on its €15.0 million loan from Servier (See Note 7: Long-Term Debt and Other Financings). In order to manage its foreign currency exposure related to these payments, in May 2011, the Company entered into two foreign exchange option contracts to buy €1.5 million and €15.0 million in January 2014 and January 2016, respectively. By having these option contracts in place, the Company’s foreign exchange rate risk is reduced if the U.S. dollar weakens against the Euro. However, if the U.S. dollar strengthens against the Euro, the Company is not required to exercise these options, but will not receive any refund on premiums paid.

Upfront premiums paid on these foreign exchange option contracts totaled $1.5 million. The fair values of these option contracts are revalued at each reporting period and are estimated based on pricing models using readily observable inputs from actively quoted markets. The fair values of these option contracts are included in other assets on the consolidated balance sheet and changes in fair value on these contracts are included in other income (expense) on the condensed consolidated statements of comprehensive loss.

The foreign exchange options were revalued at September 30, 2013 and had an aggregate fair value of $0.3 million. The Company recognized a $0.2 million loss on revaluation for the nine months ended September 30, 2013. The Company recognized losses for the three and nine months ended September 30, 2012 of $0.1 million and $0.7 million, respectively, as a result of the revaluation.

Accrued Liabilities

Accrued liabilities consisted of the following at September 30, 2013 and December 31, 2012 (in thousands):

Contingent Warrant Liabilities

In March 2012, in connection with an underwritten offering, the Company issued five-year warrants to purchase 14,834,577 shares of XOMA’s common stock at an exercise price of $1.76 per share. These warrants contain provisions that are contingent on the occurrence of a change in control, which would conditionally obligate the Company to repurchase the warrants for cash in an amount equal to their fair value using the Black-Scholes Option Pricing Model (the “Black-Scholes Model”) on the date of such change in control. Due to these provisions, the Company is required to account for the warrants issued in March 2012 as a liability at fair value. In addition, the estimated liability related to the warrants is required to be revalued at each reporting period until the earlier of the exercise of the warrants, at which time the liability will be reclassified to stockholders' equity, or expiration of the warrants. At December 31, 2012, the fair value of the warrant liability was estimated to be $15.0 million using the Black-Scholes Model. The Company revalued the warrant liability at September 30, 2013 using the Black-Scholes Model and recorded the $25.7 million increase in the fair value as a loss in the revaluation of contingent warrant liabilities line of its condensed consolidated statements of comprehensive loss. The Company also reclassified $1.6 million from contingent warrant liabilities to equity on its condensed consolidated balance sheets due to the exercise of warrants. As of September 30, 2013, 13,673,183 of these warrants were outstanding and had a fair value of $39.1 million. This increase in liability is due primarily to the increase in the market price of the Company’s common stock at September 30, 2013 compared to December 31, 2012.

In February 2010, in connection with an underwritten offering, the Company issued five-year warrants to purchase 1,260,000 shares of XOMA’s common stock at an exercise price of $10.50 per share. In June 2009, the Company issued warrants to certain institutional investors as part of a registered direct offering. These warrants represent the right to acquire an aggregate of up to 347,826 shares of XOMA’s common stock over a five year period beginning December 11, 2009 at an exercise price of $19.50 per share. These warrants contain provisions that are contingent on the occurrence of a change in control, which would conditionally obligate the Company to repurchase the warrants for cash in an amount equal to their fair value using the Black-Scholes Model on the date of such change in control. Due to these provisions, the Company is required to account for the warrants issued in February 2010 and June 2009 as liabilities at fair value. As of September 30, 2013, all of these warrants were outstanding and had an aggregate fair value of approximately $0.1 million.