Chiron and XOMA Announce Initiation of Phase I Clinical Trial for CHIR-12.12 in Multiple Myeloma — Second Clinical Trial Evaluating Oncology Drug Candidate Begins

Business Wire, Oct 13, 2005

EMERYVILLE, Calif. & BERKELEY, Calif. -- Chiron Corporation (Nasdaq:CHIR) and XOMA Ltd. (Nasdaq:XOMA) today announced the initiation of a second clinical trial of CHIR-12.12, a novel, fully human, antagonist antibody that targets the CD40 antigen. The Phase I trial is for patients with multiple myeloma, a type of cancer that is associated with expression of the CD40 antigen on the cancer cell surface. Chiron and XOMA announced the initiation of a Phase I clinical trial of CHIR-12.12 in patients with chronic lymphocytic leukemia in April 2005. CHIR-12.12 is the first drug candidate to enter clinical testing under the collaborative agreement between Chiron and XOMA for the development and commercialization of antibody products for the treatment of cancer.

"The expansion of our Phase I program is an indication of our excitement for this compound," said Stephen Dilly, M.D., Ph.D., chief medical officer, Chiron BioPharmaceuticals. "Chiron's translational-medicine approach to drug development has helped identify diseases against which CHIR-12.12 may be effective, providing us with data that supports our decision to move forward with studies in multiple areas."

"We're pleased to move CHIR-12.12 into clinical studies in a second B-cell oncology indication," said John C. Castello, XOMA's chairman, president and chief executive officer. "Our collaboration with Chiron enables both companies to advance promising antibodies more quickly than either could alone. This benefits our employees and shareholders, as well as potentially offering a new treatment for multiple myeloma patients."

The single-agent, open-label Phase I study of CHIR-12.12 is designed to evaluate the safety, dose tolerability and pharmacokinetic profile of CHIR-12.12 in patients with multiple myeloma. Translational medicine will be used to monitor biomarkers and allow correlation of these markers with response to CHIR-12.12 therapy, guiding the dosing regimen and the selection of responsive patient populations. The study is expected to enroll up to 40 patients at four leading cancer centers in the United States.

About CHIR-12.12

CHIR-12.12 is a fully human, antagonist antibody that targets the CD40 antigen. As shown in vitro in cell lines, in vivo in animal models and ex vivo in patient cells, CHIR-12.12 binds to tumor cells that express CD40 and antagonizes (prevents) CD40 ligand-mediated growth and survival of malignant B cells. Based on preclinical data, CHIR-12.12 also induces antibody-dependent cellular cytotoxicity (ADCC), killing CD40 expressing tumor cells by immune effector cells. This dual mechanism of action makes CHIR-12.12 a drug candidate with potential for the treatment of B-cell malignancies. CHIR-12.12 is an investigational drug candidate and has not been approved by the U.S. Food and Drug Administration.

About Multiple Myeloma

Multiple myeloma, also known as myeloma or plasma cell myeloma, is a progressive hematologic (blood) cancer of the plasma cell (a type of B lymphocyte), an important part of the immune system that produces immunoglobulins (antibodies) to help fight infection and disease. Clinical manifestations of multiple myeloma include hypercalcemia, anemia, renal damage, increased susceptibility to bacterial infection, and impaired production of normal immunoglobulin. The disease also is characterized by diffuse osteoporosis (bone destruction), usually in the pelvis, spine, ribs and skull. Multiple myeloma is the second most prevalent blood cancer after non-Hodgkin's lymphoma, representing approximately 1 percent of all cancers and 2 percent of all cancer deaths. The median age at diagnosis is about 71 years, and only 2 percent of cases are diagnosed in individuals under the age of 45. Statistics indicate both increasing incidence and earlier age of onset of multiple myeloma. Approximately 50,000 Americans currently have multiple myeloma, and the American Cancer Society estimates that approximately 15,980 new cases of multiple myeloma will be diagnosed in 2005.

About Chiron

Chiron delivers innovative and valuable products to protect human health by advancing pioneering science across the landscape of biotechnology. The company works to deliver on the limitless promise of science and make a positive difference in people's lives. For more information, please visit www.chiron.com.

About XOMA

XOMA develops and commercializes antibody and other protein-based biopharmaceuticals for cancer, immune disorders and infectious diseases. The company pipeline includes products from collaborative product development programs with Chiron Corporation, Millennium Pharmaceuticals, Inc., and Aphton Corporation, and also includes RAPTIVA(R), a product marketed worldwide that came from a collaboration with Genentech, Inc. For more information about XOMA's product pipeline and antibody product development capabilities and technologies, please visit XOMA's website at www.xoma.com.

Chiron Forward-Looking Statements

This news release contains forward-looking statements, including statements regarding development of CHIR-12.12, regulatory review and marketing, that involve risks and uncertainties and are subject to change. A full discussion of the company's operations and financial condition, including factors that may affect its business and future prospects, is contained in documents the company has filed with the SEC, including the Form 10-Q for the quarter ended June 30, 2005, and the Form 10-K for the year ended December 31, 2004, and will be contained in all subsequent periodic filings made with the SEC. These documents identify important factors that could cause the company's actual performance to differ from current expectations, including the outcome of clinical trials, regulatory review and approvals, competition, manufacturing capabilities, intellectual property protections and defenses, and marketing effectiveness. In particular, there can be no assurance that Chiron will successfully develop and receive approval to market new products, including CHIR-12.12, or achieve market acceptance for such new products. There can be no assurance that Chiron's out-licensing activities will generate significant revenue, nor that its in-licensing activities will fully protect it from claims of infringement by third parties. In addition, the company may engage in business opportunities, the successful completion of which are subject to certain risks, including approval by Novartis AG, regulatory approvals, and the integration of operations.