XOMA Announces Proposed Public Offering of Common Stock and Warrants

BERKELEY, Calif., March 5, 2012 (GLOBE NEWSWIRE) -- XOMA Corporation (Nasdaq:XOMA) announced today that it is offering to sell, subject to market and other conditions, shares of its common stock and corresponding warrants to purchase one half of a share of common stock for each share purchased, pursuant to an effective shelf registration statement in an underwritten public offering. All of the shares and warrants in the offering are to be sold by XOMA.

RBC Capital Markets and Cowen and Company are acting as joint book-running managers and Roth Capital Partners is acting as co-manager of the proposed offering. The shares of common stock and warrants will be issued pursuant to a prospectus supplement filed as part of a shelf registration statement previously filed with the Securities and Exchange Commission (SEC) on Form S-3.

This press release does not constitute an offer to sell or a solicitation of an offer to buy nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction. This press release is being issued pursuant to and in accordance with Rule 134 under the Securities Act of 1933, as amended. Any offer, if at all, will be made only by means of a prospectus supplement and accompanying prospectus forming a part of the effective registration statement. Copies of the preliminary prospectus supplement and accompanying prospectus relating to the offering may be obtained, when available, from RBC Capital Markets, LLC, Attention: Equity Syndicate, 3 World Financial Center, 200 Vesey Street, 8th Floor, New York, NY 10281-8098, Telephone: 1-877-822-4089, or from Cowen and Company, LLC c/o Broadridge Financial Services., 1155 Long Island Avenue, Edgewood, NY,11717, Attn: Prospectus Department, Phone: 631-274-2806, Fax: 631-254-7140. XOMA intends to file a preliminary prospectus supplement relating to the offering with the SEC, which will be available along with the prospectus filed with the SEC in connection with the shelf registration, on the SEC's website at http://www.sec.gov/.

About XOMA

XOMA discovers and develops innovative antibody therapeutics.

The XOMA Corporation logo is available at https://www.globenewswire.com/newsroom/prs/?pkgid=5960

Forward-Looking Statements

Certain statements contained herein concerning XOMA's expectations regarding the completion, timing, size and terms of the proposed public offering or product development, or that otherwise relate to future periods are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. These statements are based on assumptions that may not prove accurate. Actual results could differ materially from those anticipated due to certain risks inherent in the biotechnology industry and for companies engaged in the development of new products in a regulated market. Among other things, the proposed offering is subject to market conditions and, if terms are agreed, the offering will be subject to customary closing conditions. These and other risks, including those related to current economic and financial market conditions; the results of discovery and pre-clinical testing; the timing or results of pending and future clinical trials (including the design and progress of clinical trials; safety and efficacy of the products being tested; action, inaction or delay by the FDA, European or other regulators or their advisory bodies; and analysis or interpretation by, or submission to, these entities or others of scientific data); changes in the status of existing collaborative or licensing relationships; the ability of collaborators, licensees and other third parties to meet their obligations and their discretion in decision-making; XOMA's ability to meet the demands of the United States government agency with which it has entered into its government contracts; competition; market demand for products; scale-up, manufacturing and marketing capabilities; availability of additional licensing or collaboration opportunities; international operations; share price volatility; XOMA's financing needs and opportunities; uncertainties regarding the status of biotechnology patents; and uncertainties as to the costs of protecting intellectual property, are described in more detail in XOMA's most recent filing on Form 10-K and in other SEC filings. Consider such risks carefully when considering XOMA's prospects.

CONTACT: XOMA Corporation
         Company and Investor Contact:
         Carol DeGuzman
         510-204-7270
         deguzman@xoma.com

         Juliane Snowden
         The Oratorium Group, LLC
         jsnowden@oratoriumgroup.com

         Canale Communications
         Media Contact:
         Pam Lord
         619-849-6003
         pam@canalecomm.com

Released March 5, 2012