Saturday, May 15, 1999

Follow-Up Data Shows Improvement in Overall Survival in Metastatic Breast Cancer Patients Treated with Herceptin, Plus Chemotherapy

One of Few Therapies to Demonstrate Overall Survival Benefit in This Patient Population

Atlanta -- May 15, 1999 --

Genentech, Inc. (NYSE: GNE) today announced at the annual meeting of the American Society of Clinical Oncology (ASCO) that metastatic breast cancer patients who have tumors that overexpress the HER2 (human epidermal growth factor receptor2) protein, when treated with Herceptin, (Trastuzumab) plus chemotherapy had a longer overall survival. The results were given in an oral presentation at ASCO by Dr. Larry Norton, head of the Division of Solid Tumor Oncology at Memorial Sloan-Kettering.

Updated results from the Phase III trial showed that at a median follow-up of 29 months, overall survival in patients treated with Herceptin plus chemotherapy (anthracycline and cyclophosphamide (AC) or paclitaxel) was 25.4 months as compared to 20.3 months in patients treated with chemotherapy alone. In patients treated with Herceptin plus AC, median survival was 26.8 months as compared to 22.8 months for patients treated with AC alone. Median survival for patients treated with Herceptin plus paclitaxel was 22.1 months as compared to 18.4 months for patients receiving paclitaxel alone.

"These are important results for women with this very aggressive form of metastatic breast cancer," said Susan D. Hellmann, M.D., M.P.H., Genentech's senior vice president, development and chief medical officer. "Few therapies have demonstrated an overall survival benefit in this disease."

In this Phase III trial, presented last year at ASCO, patients were treated either with Herceptin in combination with chemotherapy -- paclitaxel alone or anthracycline plus cyclophosphamide -- or treated with chemotherapy alone. The study included 469 women who had tumors that overexpressed HER2 who had not been previously treated with chemotherapy for their metastatic disease. However, 65 percent of the patients who received chemotherapy alone elected to receive Herceptin when their disease progressed, a crossover that might be expected to understate the actual survival benefit of Herceptin.

"The overall survival advantage shown is particularly notable as almost two-thirds of the patients treated initially with chemotherapy alone received Herceptin after disease progression," said Dr. Hellmann.

Herceptin was approved in September 1998 for use in women with metastatic breast cancer who have tumors that overexpress the HER2 protein. It is indicated for treatment of patients both as first line therapy in combination with paclitaxel and as a single agent in second and third line therapy.

Herceptin was generally well tolerated by the 900 women treated in clinical trials. Overall, the most common adverse events were chills and fever in approximately 40 percent of patients, primarily with the first infusion.

An increased risk of cardiac dysfunction was observed in women receiving Herceptin and anthracyclines at the same time compared to women receiving anthracyclines alone. In the Herceptin-plus-anthracycline group, 27 percent (38 of 143) of women experienced cardiac dysfunction, compared to 6 percent (8 of 135) in patients receiving anthracyclines alone. The incidence of cardiac dysfunction was 12 percent (11 of 91) for Herceptin and paclitaxel compared to 2 percent (2 of 95) in patients receiving paclitaxel alone. This side effect can be potentially severe or life-threatening, but in most cases can be managed with medication. In patients treated with Herceptin alone the incidence was 4.7 percent (10 of 213). Most of these patients (87 percent) had symptomatic improvement with initial treatment for their cardiac dysfunction. Of the 38 patients with cardiac dysfunction receiving Herceptin plus anthracyclines 14 continued, and of the 11 patients receiving Herceptin plus paclitaxel 6 continued without further cardiac events.

Approximately 1.6 million women have been diagnosed with breast cancer in the United States. According to the American Cancer Society, approximately 180,000 new cases are diagnosed in any given year. Genentech estimates there are approximately 164,000 women with metastatic breast cancer. Of these women, 25-30 percent have tumors that overexpress HER2 and may be candidates for Herceptin. Routine testing of the tumors from women with metastatic breast cancer will be critical for identification of patients who overexpress the HER2 protein and who could potentially benefit from treatment with Herceptin.

Genentech, Inc. is a leading biotechnology company that discovers, develops, manufactures and markets human pharmaceuticals for significant unmet medical needs. Twelve of the currently marketed biotechnology products stem from Genentech science. Genentech markets seven biotechnology products directly in the United States. The company has headquarters in South San Francisco, California, and is traded on the New York Stock Exchange and the Pacific Exchange under the symbol GNE.

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