Dendreon's APC8024 Immunotherapy Shows Long-Term Disease Stabilization and Significant Immune Response in Advanced, Metastatic Breast Cancer Patients.

Business Editors/Health/Medical Writers

BIOWIRE2K

95th Annual Meeting of the American Association for Cancer

Research (AACR)

ORLANDO, Fla.--(BUSINESS WIRE)--March 29, 2004

Data presented at AACR annual meeting

Dendreon Corporation (Nasdaq:DNDN) today announced that updated results from a Phase 1 clinical trial of APC8024, the company's investigational immunotherapy for HER-2/neu-positive cancers, indicate that APC8024 continues to demonstrate clinical benefit and statistically significant T-cell immune responses in patients with advanced, metastatic, HER-2/neu positive breast cancer. The findings were presented Sunday, March 28 at the 95th Annual Meeting of the American Association for Cancer Research in Orlando, Florida.

Results from 18 patients with advanced, metastatic, HER-2/neu-positive breast cancer (2+ or 3+ by immunohistochemistry or positive by FISH) were presented. All but one of the patients had failed Herceptin therapy and most patients had also failed chemotherapy treatment, including 32 percent of whom had received more than three chemotherapy regimens. Clinical benefit was demonstrated in 22 percent of patients treated with APC8024, including three patients with prolonged stabilization of disease. Further, long-term follow up on these patients indicates that they experienced stabilization of their disease for 15, 20 and 22 months following treatment with APC8024, respectively, without requiring additional chemotherapy. Treatment with APC8024 was well tolerated, with no significant side effects reported and no evidence of cardiotoxicity. Treatment with APC8024 also induced a robust cellular immune response specific to HER-2/neu antigens, and this immune response was statistically significant.

"It is encouraging that we are seeing both strong immunologic effects and prolonged stabilization of disease in selected patients, which now includes very extended durations post-treatment. Such results are notable among patients with advanced, metastatic disease who have failed other treatment modalities," said John W. Park, M.D., assistant professor of medicine and director of Novel Therapeutics in Breast Oncology at the University of California San Francisco Comprehensive Cancer Center, and principal investigator of the study. "Based on these results, we certainly believe that further studies are warranted."

"The clinical benefit and significant immune response demonstrated from APC8024 treatment among these patients with advanced, progressive breast cancer underscores the expandability of our therapeutic vaccine platform," said Robert Hershberg, M.D., Ph.D., senior vice president and chief medical officer, Dendreon Corporation. "Like Provenge(R), APC8024 may provide patients with a new treatment alternative that is highly targeted and has a favorable safety profile. We look forward to advancing this program into Phase 2 trials."

The APC8024 vaccine targets tumors that express the HER-2/neu marker. In humans, HER-2/neu is overexpressed in a variety of solid tumors. APC8024 uses Dendreon's proprietary Antigen Delivery Cassette(TM) technology to genetically engineer antigens such as HER-2/neu to bind to antigen presenting cells and stimulate T-cell immunity. Treatment consists of three vaccinations with APC8024 over the course of a one-month period. The APC8024 approach is similar to the approach used in the development of Provenge, Dendreon's therapeutic prostate cancer vaccine, which has produced promising results in a Phase 3 clinical trial.

About Breast Cancer

Breast cancer is the most common cancer among women in the United States, other than skin cancer. It is the second leading cause of cancer death in women, after lung cancer, with approximately 216,000 new cases and 40,000 deaths estimated in the United States in 2004.

About Dendreon

Dendreon Corporation is a biotechnology company developing targeted therapies for cancer. In addition to its immunotherapies in clinical and preclinical development for a variety of cancers, Dendreon's product pipeline also includes monoclonal antibody, small molecule and prodrug product candidates. Dendreon has research and development alliances with Genentech, Inc., Abgenix, Inc. and Dyax Corp. For more information about the company and its programs, 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 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 relating to the efficacy of APC8024, the risk that the results of this Phase 1 clinical trial of APC8024 may not be indicative of results obtained in other clinical trials of APC8024, risks and uncertainties surrounding the presentation of data to the FDA, risks related to Dendreon's relatively limited operating history, risks associated with completing our clinical trials, risks that we may lack the financial resources and access to capital to fund required clinical trials, 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