Interim Phase 2 Data Suggest Activity of Panitumumab with Chemotherapy in First-Line Treatment of Metastatic Colorectal Cancer

VIENNA, Austria--(BUSINESS WIRE)--Nov. 1, 2004--Amgen Inc. (Nasdaq:AMGN) and Abgenix (Nasdaq:ABGX) today announced interim data from part one of an ongoing Phase 2 study suggesting panitumumab, the first fully human monoclonal antibody that inhibits the epidermal growth factor receptor (EGFr), has activity as a first-line treatment with chemotherapy in patients with metastatic colorectal cancer (mCRC). Results from part one of this two-part single-arm, open-label phase 2 study were described in a poster presentation at the European Society for Medical Oncology's (ESMO) 29th Congress in Vienna (Abstract # 265).

Patients in part one of the study (n=19) received 2.5 mg/kg weekly of panitumumab administered with standard doses of the Saltz regimen (Irinotecan, 5-Fluorouracil and Leucovorin (IFL)). The primary efficacy endpoint was progression-free survival (PFS) as measured by the Response Evaluation Criteria in Solid Tumors (RECIST). Median progression free survival was 8.2 months (95% confidence interval: 5.4 to 16.5 months). Nine of 19 patients (47 percent) had confirmed objective responses (1 complete response and 8 partial responses) after six weeks of therapy. Six patients (32 percent) had stable disease at week six or later, and one patient had progressive disease at week six as assessed by the investigator.

"These interim data suggest that adding panitumumab to chemotherapy for colorectal cancer produces promising anti-tumor activity. The final results of this ongoing trial should lead to future studies incorporating panitumumab with other active agents in colorectal cancer," said Jordan Berlin, M.D., associate professor of medicine at Vanderbilt-Ingram Cancer Center and the study's lead investigator.

Panitumumab was generally well-tolerated. The most frequent adverse event was skin rash (100 percent; 16 percent grade 3, no grade 4). No patient discontinued therapy due to rash. Diarrhea (47 percent grade 3 or 4) was an expected adverse reaction that has been associated with IFL chemotherapy; in previous studies, panitumumab given by itself has resulted in only generally mild diarrhea (30 percent grade 1 or 2). Other grade 3 or 4 treatment-related adverse events reported in more than 2 patients were abdominal pain (16 percent), dehydration (16 percent), and hypokalemia (low potassium level, 16 percent).

Two minor possibly infusion-related reactions were reported, including one cold sweat (grade 1) and one hypotension (grade 2). These events did not reappear upon additional panitumumab administration. No other infusion-related reactions were reported.

Based on these findings, part 2 of this study (n=24) is ongoing to evaluate safety, pharmacokinetics and efficacy of panitumumab administered with the FOLFIRI regimen (FOLinic acid, Fluorouracil, and IRInotecan), currently the more widely applied of the various irinotecan-based regimens.

Additional Pharmacokinetic Data Presented Separately

Additional pharmacokinetic data from the phase 2 study of panitumumab as a first line treatment in combination with chemotherapy in patients with metastatic colorectal cancer were also presented as a poster (Abstract # 311). In the pharmacokinetic data subset study, exposure to panitumumab and irinotecan was similar to that in previously published reports and abstracts in which either drug was given alone. The study concluded that no apparent pharmacokinetic interactions were observed between panitumumab and irinotecan in metastatic colorectal cancer patients.

About Panitumumab

Co-developed by Amgen and Abgenix, panitumumab is an investigational product in a new class of targeted cancer treatments called epidermal growth factor receptor (EGFr) inhibitors. Panitumumab (formerly ABX-EGF), which was generated with XenoMouse(R) technology, is the first fully human monoclonal antibody directed against EGFr and is being evaluated as both a monotherapy and in combination with other agents for the treatment of various types of cancer, including colorectal, lung and kidney. Amgen initiated pivotal trials in the United States and Europe evaluating panitumumab as third-line monotherapy in colorectal cancer patients in January 2004.

About Amgen

Amgen is a global biotechnology company that discovers, develops, manufactures and markets important human therapeutics based on advances in cellular and molecular biology.

About Abgenix

Abgenix is a biopharmaceutical company focused on the discovery, development and manufacturing of human therapeutic antibodies. The company's antibody development platform includes a leading technology and state-of-the-art manufacturing capabilities that enable the rapid generation, selection and production of high affinity, fully human antibody product candidates to a variety of disease targets. Abgenix leverages its leadership position in human antibody technology to build a diversified product portfolio through the establishment of collaborations with multiple pharmaceutical and biotechnology companies. For more information on Abgenix, visit the company's Web site at

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SOURCE: Abgenix and Amgen Inc.