Phase 3 Clinical Trial Initiated to Evaluate the Use of Panitumumab Therapy for First-Line Treatment of Metastatic Colorectal Cancer; Study Evaluates Panitumumab Administered With Bevacizumab and Chemotherapy| Amgen

Phase 3 Clinical Trial Initiated to Evaluate the Use of Panitumumab Therapy for First-Line Treatment of Metastatic Colorectal Cancer; Study Evaluates Panitumumab Administered With Bevacizumab and Chemotherapy

THOUSAND OAKS & FREMONT, Calif.--(BUSINESS WIRE)--April 26, 2005--Amgen Inc. (Nasdaq:AMGN) and Abgenix, Inc. (Nasdaq:ABGX) today announced the initiation of a Phase 3 clinical study to evaluate the potential benefits of adding panitumumab, an experimental fully human monoclonal antibody, administered every other week to bevacizumab (Avastin(TM), Genentech) and either oxaliplatin- (Eloxatin(R), sanofi-aventis) or irinotecan-based (Camptosar(R), Pfizer) chemotherapy for the first-line treatment of metastatic colorectal cancer. The clinical trial, called the PACCE (Panitumumab Advanced Colorectal Cancer Evaluation) study, is a randomized, multi-center, open-label study, with endpoints of progression-free survival, overall survival and response rate. Enrollment in the study of approximately 1,000 patients is already underway.

"Targeting multiple pathways that aid in tumor survival and growth at the same time or in succession theoretically has advantages over targeting one pathway alone," said Willard Dere, M.D., chief medical officer and senior vice president of global development at Amgen. "In clinical studies to date, panitumumab appears to be well-tolerated, and interim Phase 2 data demonstrate that objective tumor responses in metastatic colon cancer patients occurred following panitumumab treatment. "

"We are delighted with the initiation of this important clinical trial to further explore the potential for our lead product, panitumumab, in the first-line treatment of metastatic colorectal cancer," said Bill Ringo, president and chief executive officer at Abgenix. "This study is a key step in the overall clinical program for panitumumab, which we expect to be evaluated with various chemotherapy agents and targeted therapies across multiple tumor types."

Panitumumab inhibits the epidermal growth factor receptor (EGFr), while bevacizumab targets the vascular endothelial growth factor involved in angiogenesis. Although EGFr normally helps regulate the growth of many different cells in the body, EGFr can also stimulate cancer cells to grow. In fact, many cancer cells actually require signals mediated by EGFr for their survival. Residing on the surface of these tumor cells, EGFr is activated when naturally occurring proteins in the body, epidermal growth factor (EGF) or transforming growth factor alpha (TGF-alpha), bind to it. This binding changes the shape of EGFr, which, in turn, triggers internal cellular signals that stimulate tumor cell growth.

Panitumumab binds to EGFr, preventing EGF and TGF-alpha from binding to the receptor and interfering with the signals that would otherwise stimulate growth of the cancer cell and allow it to survive.

Patients and physicians can access for more information about ongoing panitumumab clinical trials.

About Panitumumab

Co-developed by Amgen and Abgenix, panitumumab is an investigational product in a novel class of targeted cancer treatments called epidermal growth factor receptor (EGFr) inhibitors. Panitumumab (formerly ABX-EGF) 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. Panitumumab is generated with Abgenix's XenoMouse(R) technology, which creates a fully human monoclonal antibody that contains no murine (mouse) protein. The fully human nature of panitumumab may result in a favorable safety profile with a low incidence of infusion reactions, antigenicity and allergic response. These are attributes currently being investigated in clinical trials. Pivotal clinical studies evaluating panitumumab as a third-line monotherapy in colorectal cancer patients are ongoing with an every-other-week dosing regimen.

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

Amgen Forward-Looking Statement

This news release contains forward-looking statements that involve significant risks and uncertainties, including those discussed below and others that can be found in Amgen's Form 10-K for the year ended December 31, 2004, and in Amgen's periodic reports on Form 10-Q and Form 8-K. Amgen is providing this information as of the date of this news release and does not undertake any obligation to update any forward-looking statements contained in this document as a result of new information, future events or otherwise.

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The scientific information discussed in this news release related to our product candidates is preliminary and investigative. Such product candidates are not approved by the U.S. Food and Drug Administration (FDA), and no conclusions can or should be drawn regarding the safety or effectiveness of the product candidates. Only the FDAcan determine whether the product candidates are safe and effective for the use(s) being investigated.

Further, the scientific information discussed in this news release relating to new indications for our products is preliminary and investigative and is not part of the labeling approved by the U.S. Food and Drug Administration (FDA) for the products. The products are not approved for the investigational use(s) discussed in this news release, and no conclusions can or should be drawn regarding the safety or effectiveness of the products for these uses. Only the FDA can determine whether the products are safe and effective for these uses. Healthcare professionals should refer to and rely upon the FDA-approved labeling for the products, and not the information discussed in this news release.

Abgenix Forward-Looking Statement

Certain statements in this press release are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. These include forward-looking statements about Abgenix's technologies, product development activities, clinical trials and clinical trial results, the potential submission of a biologic license application for panitumumab, collaborative arrangements, process sciences and manufacturing activities, projected financial and operating results, and achievement of milestone or similar payments or other revenues. All such statements are subject to a number of uncertainties that could cause actual results to differ materially from the statements made, including risks associated with conducting clinical trials, regulatory approval processes and meeting requirements for regulatory approval, the progress of research and product development programs, product manufacturing, competitive products and services, capital requirements, the extent and breadth of Abgenix's patent portfolio, and other factors set forth in Abgenix's public filings with the Securities and Exchange Commission, including the risks described in Abgenix's annual report on Form 10-K for the year ended December 31, 2004. Abgenix is providing this information as of the date of this press release and does not undertake any obligation to update any forward-looking statements.

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