Data presented at the Digestive Disease Week (DDW) meeting this week in Washington D.C. by Dr. William Sandborn from the Mayo Clinic suggest that Nuvion (visilizumab), an antibody in development as a treatment for intravenous steroid-refractory ulcerative colitis (IVSR-UC), administered on day 1 and day 2, produced a sustained clinical response up to 310 days and was adequately tolerated. The results presented were from long-term follow up of 138 patients who had received Nuvion in a Phase 1 and Phase 1/2 study as a treatment for IVSR-UC, which contributes to the majority of an estimated 30,000 colectomy procedures performed in the U.S. each year. In addition, early data also will be presented at the meeting regarding the Nuvion antibody's potential as a treatment for Crohn's disease.

"The data presented by Professor Sandborn further support our decision to advance Nuvion into a Phase 3 program in patients with IV steroid-refractory ulcerative colitis," said Mark McCamish, M.D., Ph.D., PDL's senior vice president and chief medical officer. "Patients with severe ulcerative colitis face surgical intervention or colectomy, and positive results from our Phase 3 program would lead to a welcomed treatment for these difficult-to-treat patients who currently have very limited non-surgical options."

Nuvion is a humanized monoclonal antibody designed to target and modulate the action of T cells, the cells believed to cause inflammation leading to ulcerative colitis, with the aim of significantly reducing the symptoms of the disease and potentially delaying or avoiding the need for colectomy, or surgical removal of the colon. An estimated 60,000 colectomy procedures are performed in the U.S. and Europe every year. In April, after review of the current data from an external data monitoring committee, PDL announced that it would advance the Nuvion antibody into a second pivotal study in patients with IVSR-UC, the most severe form of this inflammatory bowel disease that attacks the colon.

Summary of Results (Abstract T1279)

In the study presented by Dr. Sandborn, 138 subjects with IVSR-UC were treated with visilizumab at 5, 7.5, 10, 12.5 or 15 mg/kg intravenously on two consecutive days (Days 1 and 2). Eighty-nine (64.5%) of the 138 patients demonstrated a clinical response at day 30. Clinical response was defined by using one of two standard measures to determine the severity of the patient's ulcerative colitis.

Patients were followed for a median of 356 days, ranging from 21 to 792. During the follow-up period, 53% (73/138) received medical or surgical rescue therapy. Only 28 (35%) of the Day 30 responders ended up undergoing rescue therapy during subsequent observation. Encouraging new data presented at DDW from this study show the median time to first rescue therapy was 310 days. Forty-six (33%) patients underwent colectomy (colon removal), either as first rescue therapy or subsequent to failed medical rescue.

The Nuvion antibody was adequately tolerated, with 120 (87%) patients experiencing transient, mild to moderate infusion reactions due to cytokine release within the first three days of treatment. These symptoms were minimized with pre-medication and hydration. A total of 17 (12%) patients also experienced serious or opportunistic infections, including localized mucocutaneous herpes and candida infections, but there were no disseminated opportunistic infections. The Nuvion antibody also produced a transient decline in T cells, which generally lasted less than 30 days.

Additional Nuvion Data Presentations

Two additional presentations at DDW support the potential of Nuvion as a treatment for inflammatory bowel diseases:

-- On Monday, May 21, Lloyd F. Mayer, M.D., Professor and Chairman of the Immunobiology Center, Professor of Medicine and Chief of the Divisions of Clinical Immunology and Gastroenterology at the Mount Sinai School of Medicine in New York, presented results of a study (Abstract M1679) demonstrating that in in vitro culture experiment, the Nuvion antibody induced expansion of CD8+ T cells, and the CD8+ T cells possessed regulatory T cell activity. If confirmed in human studies, this mechanism may contribute to the observed long-term response to the Nuvion antibody in some patients with IVSR-UC, Dr. Mayer concluded.

-- On Wednesday, May 23, Daniel C. Baumgart M.D., Charite Medical Center, Virchow Hospital, Berlin, Germany, will deliver an oral presentation of data supporting the efficacy and safety of the Nuvion antibody in patients with moderate-to-severe, refractory Crohn's disease (Abstract 1032). The data from this study are intriguing, and PDL is assessing options for further study in this patient population.

About PDL BioPharma

PDL BioPharma, Inc. is a biopharmaceutical company focused on discovering, developing and commercializing innovative therapies for severe or life- threatening illnesses. Commercially focused in the acute-care hospital setting, PDL markets and sells its portfolio of products in the United States and Canada. A pioneer of antibody humanization technology, PDL promotes this technology through licensing agreements and clinical development of its own diverse pipeline of investigational compounds. PDL's research platform centers on the discovery and development of antibodies to treat cancer and autoimmune diseases. For more information, please visit pdl.

Forward-looking Statements

The information in this press release should be considered accurate only as of the date of this press release. PDL has no intention of updating and specifically disclaims any duty to update the information in this press release for any reason, except as required by law, even as new information becomes available or other events occur in the future. This press release contains "forward-looking statements" that are based on current expectations and assumptions that are subject to risks and uncertainties. The actual results may differ materially from those in the forward-looking statements because of various factors, risks and uncertainties. In particular, results obtained in the Phase 1 and Phase 1/2 studies of the Nuvion (visilizumab) antibody may not be predictive of results that may be obtained in the additional evaluations that would be necessary to demonstrate visilizumab to be safe and effective in the treatment of IVSR-UC, nor can there be assurance that PDL will initiate or complete the subsequent clinical trials and evaluations that would be necessary to support marketing approval of the Nuvion antibody by the United States Food and Drug Administration. For further information regarding factors, risks and uncertainties that may cause such differences, please refer to the filings PDL has made with the Securities and Exchange Commission, including the "Risk Factors" sections of PDL's Quarterly and Annual Reports, copies of which may be obtained at the "Investors" section on PDL's website at pdl. All forward-looking statements in this press release are qualified in their entirety by this cautionary statement.

PDL BioPharma and the PDL BioPharma logo are considered trademarks of PDL BioPharma, Inc. Nuvion is a registered U.S. trademark of PDL BioPharma, Inc.

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