XOMA Announces Clinical Trial Plans for XOMA 052 in Type 2 Diabetes

New England Journal of Medicine Article Supports Clinical Testing in Type 2 Diabetes Patients With XOMA 052, a Potent Monoclonal Antibody Targeting IL-1beta With Broad Potential in Many Inflammatory Diseases

BERKELEY, Calif., April 12, 2007 (PRIME NEWSWIRE) -- XOMA Ltd. (Nasdaq:XOMA) today announced plans to initiate clinical testing of XOMA 052, a potent anti-inflammatory monoclonal antibody targeting Interleukin 1-beta (IL-1beta), in Type 2 diabetes patients. XOMA believes that XOMA 052 may have broad applicability in many IL-1 mediated diseases and has selected Type 2 diabetes as an initial indication due to the significant medical need and clinical proof of concept data available for this pathway. The significant findings reported today in the New England Journal of Medicine illustrate the potential for an anti-IL-1beta product with the characteristics of XOMA 052 in the treatment of Type 2 diabetes. XOMA 052's very high binding affinity of 300 fM and expected long circulating half-life, may result in many patient advantages such as less frequent dosing. For the development of XOMA 052 for Type 2 diabetes, XOMA is working with leaders in the field including Thomas Mandrup-Poulsen, M.D., Ph.D., and Marc Y. Donath, M.D., principal investigators of the New England Journal of Medicine article, and Charles A. Dinarello, M.D., a noted IL-1beta authority.

XOMA is announcing its plans to initiate two Phase I clinical trials this year in Type 2 diabetes patients addressing the role of IL-1beta in the disease. One trial will be run in the U.S. and the other in Europe. XOMA is currently evaluating plans to expand the development of XOMA 052 into additional autoimmune / inflammatory indications including osteoarthritis, rheumatoid arthritis, systemic juvenile idiopathic arthritis and others.

"Having participated in the development of other biological drugs such as rituximab, etanercept and anakinra, I can say that I am excited about the potential of XOMA 052," said Alan Solinger, M.D. Vice President of Clinical Immunology at XOMA. "We will be working with key opinion leaders in Type 2 diabetes as our first indication but I also look forward to developing XOMA 052 for its many other potential applications in IL-1 mediated diseases."

Charles A. Dinarello, M.D., a noted IL-1beta authority and co-author of an abstract concerning XOMA 052 to be presented at the May 2007 meeting of the American Association of Immunologists said, "XOMA 052 has a great profile and an excellent chance to make inroads into several inflammatory diseases including Type 2 diabetes."

"Our data supplied proof of concept in clinical trials of the impact of IL-1beta on Type 2 diabetes mellitus," said Marc Y. Donath, M.D., of the University Hospital Zurich, initiator and a co-author of "Interleukin-1-Receptor Antagonist in Type 2 Diabetes Mellitus" published today in the New England Journal of Medicine. "I believe, based on its profile, that XOMA 052 has tremendous potential in the treatment of this disease and clinical testing is a next logical step in developing more effective therapies. I look forward to participating with XOMA in taking XOMA 052 into clinical testing."

Since the seminal discovery by Thomas Mandrup-Poulsen, M.D., Ph.D., of the Steno Diabetes Center, Copenhagen, published in Science in 1986 that IL-1 causes destruction of pancreatic beta-cells, it has been suspected that IL-1 is an important mediator of Type 1 diabetes mellitus, a form of diabetes caused by activation of the immune system against the insulin producing beta-cells. "The surprise is that IL-1 is also involved in the progressive destruction of beta-cells in Type 2 diabetes," said Dr. Mandrup-Poulsen. "IL-1 may thus be a common denominator in the causation of both major types of diabetes, and targeting this pathway may protect insulin secretory capacity in patients at risk for developing diabetes, in patients with established diabetes with some residual beta-cell function and in patients treated with transplantation of insulin-producing cells. The therapeutic potential of anti-IL-1 therapy is therefore considerable."

The New England Journal of Medicine article provides background for an understanding of the importance of IL-1 to Type 2 diabetes. The authors noted that the combination of decreased expression of IL-1-receptor antagonist in pancreatic islets (insulin-producing regions within pancreas) of patients with Type 2 diabetes plus high blood glucose concentrations leads to production of IL-1beta in human pancreatic beta cells. This combination leads to reduced insulin secretion, impaired cell proliferation, and programmed cell death of insulin-producing beta cells in the pancreas. The authors have now demonstrated in a randomized, double-blind, placebo-controlled clinical study of 70 patients with Type 2 diabetes that the administration of an IL-1 receptor antagonist for 13 weeks resulted in statistically significant improvement in the control of blood glucose (measured by HbA1c and other measurements), improvement in beta-cell secretory function and reduced markers of systemic inflammation. The endpoints measured in the trial are generally considered approvable endpoints.

About Type 2 diabetes:

More than 20 million Americans have diabetes, over 90% of whom have Type 2 diabetes, which is the seventh leading cause of death in the Unites States. Type 2 diabetes is nearing epidemic proportions, due to an increased number of older Americans and a greater prevalence of obesity and a sedentary lifestyle. Over 200 million people worldwide have Type 2 diabetes and the prevalence is increasing dramatically in both the developed and developing worlds. Type 2 diabetes is a lifelong illness, which generally starts in middle age or later part of life, but can start at any age. Type 2 diabetes is a metabolic disorder characterized by insulin resistance (e.g., increasing amounts of insulin needed to control blood glucose levels), relative insulin deficiency (e.g., decreased insulin production by pancreatic beta-cells), and hyperglycemia (elevated blood glucose levels). There is currently no cure for Type 2 diabetes but the disease can often be managed through proper diet, weight control, an appropriate exercise program, various medications and regular monitoring of the hemoglobin A1c levels. Untreated or poorly controlled diabetes can cause problems with the kidneys, legs, feet, eyes, heart, nerves, and blood flow, which could lead to kidney failure, gangrene, amputation, blindness, or stroke.

Type 2 diabetes occurs when pancreatic beta-cell insulin production fails to compensate for insulin resistance elsewhere in the diabetic patient. In Type 2 diabetes, beta-cell function progressively deteriorates over time, partly because of beta-cell destruction. IL-1beta, a proinflammatory cytokine, inhibits the function and promotes the apoptosis (programmed cell death) of pancreatic beta cells in Type 2 diabetes. Blocking IL-1beta, such as with XOMA 052, may offer a new approach to treatment and control of Type 2 diabetes.

About XOMA 052:

XOMA 052 is a potent anti-inflammatory monoclonal antibody targeting IL-1beta and is being developed as a modulator of cytokine imbalance in IL-1 mediated disease states. It is an IgG2 isotype, which reduces the possibility of antibody dependent cellular cytotoxicity. With its very high binding affinity of 300 fM and expected long circulating half-life, XOMA 052 may result in many patient advantages including less frequent dosing. XOMA 052 was developed by XOMA from its extensive antibody discovery infrastructure, was humanized using XOMA's Human Engineering(tm) technology, and is fully owned by XOMA. XOMA plans initial clinical trials in Type 2 diabetes and is evaluating plans to expand the development of XOMA 052 into additional autoimmune / inflammatory indications including osteoarthritis, rheumatoid arthritis, systemic juvenile idiopathic arthritis, and others.

About XOMA

XOMA is a leader in the discovery, development and manufacture of therapeutic antibodies, with a therapeutic focus that includes cancer and immune diseases. XOMA has royalty interests in RAPTIVA(r) (efalizumab), a monoclonal antibody product marketed worldwide (by Genentech, Inc. and Merck Serono S.A.) to treat moderate-to-severe plaque psoriasis, and LUCENTIS(r) (ranibizumab injection), a monoclonal antibody product marketed worldwide (by Genentech and Novartis AG) to treat neovascular (wet) age-related macular degeneration.

The company has built a premier antibody discovery and development platform that includes access to seven of the leading commercially available antibody phage display libraries and XOMA's proprietary HE(tm) and BCE technologies. More than 45 companies have signed BCE licenses. XOMA's development collaborators include Lexicon Pharmaceuticals, Inc., Novartis, Schering-Plough Research Institute and Takeda Pharmaceutical Company Limited. With a fully integrated product development infrastructure, XOMA's product development capabilities extend from preclinical sciences to product launch. For more information, please visit the company's website at www.xoma.com.

Certain statements contained herein concerning the development of XOMA 052 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. These risks, including those related to the results of discovery research and preclinical 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); uncertainties regarding the status of biotechnology patents; uncertainties as to the cost of protecting intellectual property; changes in the status of the existing collaborative and licensing relationships; the ability of collaborators, licensees and other third parties to meet their obligations; market demand for products; scale up and marketing capabilities; competition; international operations; share price volatility; XOMA's financing needs and opportunities and risks associated with XOMA's status as a Bermuda company, are described in more detail in XOMA's most recent annual report on Form 10-K and in other SEC filings. Consider such risks carefully in considering XOMA's prospects.

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