Dendreon Corporation Develops Novel Assay to Measure Potency of Provenge and Other Cancer Immunotherapies `In Vitro'.

Business Editors & Health/Medical Writers

SEATTLE--(BUSINESS WIRE)--Jan. 27, 2003

Researchers at Dendreon Corporation (Nasdaq:DNDN) have developed a novel assay that enables the use of animal models to characterize the Company's therapeutic prostate cancer vaccine, Provenge(TM), as well as other cancer immunotherapies. To date, such approaches have been limited due to species differences between human immune cells and the immune systems of animals. Results of this research are published in the current issue of Human Immunology.

The publication, "Specific Stimulation of MHC-Transgenic Mouse T-Cell Hybridomas with Xenogeneic APC," describes the use of cell lines derived from transgenic mice to measure immune stimulation induced by Provenge, a vaccine against PAP (prostatic acid phosphatase), a protein found at high levels on a majority of prostate cancer cells.

"These studies suggest that we can measure the activity of Provenge using a fairly simple cell culture system in the laboratory," said Reiner Laus, M.D., vice president of research. "The ability to measure efficacy in this manner has helped to characterize this product and greatly accelerated its development in clinical trials."

In these studies, cell lines were generated from T-cells of transgenic mice that carry the human gene for a key portion of the HLA protein, which is expressed on antigen presenting cells. After the antigen presenting cells capture the antigen of interest, in this case PAP, they process it into short peptides that form a molecular complex with HLA protein. This complex then interacts with the T cell receptor, and stimulates specific T cell responses.

Dr. Laus continued, "These data demonstrate that immune cells from different species are able to interact with one another by using co-receptors and co-stimulatory molecules that were previously not known to function across species barriers. This discovery is a result of Dendreon's ongoing efforts to understand and harness the power of the immune system to fight cancer, and may provide new tools for the development or clinical application of immunotherapies."

Previously announced results from the Provenge Phase III clinical trial D9901 demonstrated significant benefit from Provenge treatment for men with hormone resistant prostate cancer who have a Gleason score of 7 or less. In that group of patients, the placebo group had a median time to disease progression of 9.0 weeks compared to 16.0 weeks in the Provenge treated group, with a highly significant p-value of 0.002 and a treatment effect of 78 percent. In addition, the patients receiving Provenge whose disease had not progressed six months after randomization, had a greater than eight-fold advantage in progression-free survival compared to the patients who received placebo (34.7 percent of Provenge patients versus 4 percent of placebo patients). Additionally, patients receiving treatment with Provenge remained pain free significantly longer than those receiving placebo (p=.019). For patients with a Gleason score of 7 or less, the probability of remaining free of cancer-related pain while on the study was over two and one-half fold higher than for patients treated with placebo. For more information on Dendreon's clinical trials, please visit the "Clinical" section at www.dendreon.com.

Dendreon Corporation is a biotechnology company developing targeted therapies for cancer. Dendreon currently has multiple therapeutic vaccines in clinical trials and preclinical development. Dendreon's product pipeline also includes monoclonal antibodies and a pathway to small molecules. Dendreon has established important alliances with industry leaders Genentech, Inc. and Kirin Brewery Co., Ltd. For more information, visit www.dendreon.com.

Except for historical information contained herein, this news release contains forward-looking statements that are subject to risks and uncertainties that may cause actual results to differ materially from the results discussed in the forward-looking statements, particularly those risks and uncertainties surrounding the efficacy of Provenge to treat men suffering from prostate cancer, risks and uncertainties surrounding the consideration of data by the FDA and FDA approval of applications for a biologics license, and risks and uncertainties inherent in the process of discovering, developing and commercializing drugs that are safe and effective for use as human therapeutics. Factors that may cause such a difference include risks related to Dendreon's limited operating history, risks associated with completing our clinical trials, the risk that the safety and/or efficacy results of a clinical trial for Provenge will not support an application for a biologics license, the risk that the FDA will not be satisfied the data we provide for Provenge, the risk that the results of a clinical trial for Provenge may not be indicative of results obtained in a later clinical trial, risks that we may lack the financial resources and access to capital to fund required clinical trials for Provenge, dependence on the efforts of third parties, including collaborators, and our dependence on intellectual property. Further information on the factors and risks that could affect Dendreon's business, financial condition and results of operations, are contained in Dendreon's SEC reports, which are available at www.sec.gov.