Panitumumab Significantly Improves Progression-Free Survival in Phase 3 Randomized Metastatic Colorectal Cancer Study| Amgen

Panitumumab Significantly Improves Progression-Free Survival in Phase 3 Randomized Metastatic Colorectal Cancer Study

First EGFr Inhibitor to Demonstrate Improvement in Progression-Free Survival as Monotherapy for Metastatic Colorectal Cancer

THOUSAND OAKS & FREMONT, Calif., Nov 03, 2005 (BUSINESS WIRE) -- Amgen (Nasdaq:AMGN) and Abgenix, Inc. (Nasdaq:ABGX) today announced that a pivotal Phase 3 study of panitumumab met the primary endpoint of improving progression-free survival in patients with metastatic colorectal cancer (mCRC) who had failed standard chemotherapy. In this randomized Phase 3 trial involving 463 patients, those who received panitumumab every two weeks showed a 46 percent decrease in tumor progression rate versus those who received best supportive care alone (p less than 0.000000001).

This result exceeded the pre-specified measure of progression-free survival that the trial was designed to demonstrate (i.e., a 33 percent decrease in tumor progression rate in patients receiving panitumumab versus those receiving best supportive care, as assessed by central radiology review). A secondary endpoint of objective response rate, as assessed by central radiology review, was also met. Analysis of overall patient survival in this study will occur 12 months after the last patient was randomized.

"Amgen is dedicated to developing safe and effective cancer therapies that significantly improve cancer patients' outcomes," said Willard Dere, M.D., chief medical officer and senior vice president of Global Development at Amgen. "We are excited that panitumumab, our most advanced investigational cancer therapeutic, improved progression-free survival and response rate in metastatic colorectal cancer patients who had failed multiple prior chemotherapy regimens. These results will support a BLA submission, which we plan to initiate by the end of the year."

"We are very encouraged by the results of this pivotal study and what panitumumab could mean for patients with advanced colorectal cancer," said Bill Ringo, president and chief executive officer of Abgenix. "The improvement in progression-free survival shown by panitumumab in this study highlights the value of our proprietary technology and product development capabilities. We continue to work closely with our partner, Amgen, towards the regulatory filing and potential commercialization of panitumumab."

Per protocol, administration of panitumumab did not require administration of pre-medication or a loading dose, and the incidence of infusion reactions (of any severity) was low. An initial safety evaluation showed that the adverse events observed were consistent with previous clinical studies of panitumumab. The most common side effect was acneiform rash. Other side effects less commonly observed were fatigue, nausea and mild diarrhea. No human anti-human antibody (HAHA) or anti-panitumumab antibody formation was observed.

Complete analyses of data from this trial will be submitted for presentation at a medical meeting in 2006.

Panitumumab received Fast Track designation from the U.S. Food and Drug Administration (FDA) in July 2005. Amgen and Abgenix are working toward initiating the submission of the Biologics License Application (BLA) to the FDA for panitumumab in patients who have failed prior standard chemotherapy, including oxaliplatin and irinotecan, by the end of 2005. FDA has previously indicated that data from one pivotal trial, once completed, could be acceptable with additional data from other ongoing studies to support a submission for marketing approval in the United States. The completed submission of the BLA is expected in the first quarter of 2006.

Currently, panitumumab is being investigated as a single agent or in combination with other agents across multiple lines of treatment for various cancers. Patients and physicians can access for more information about ongoing panitumumab clinical trials.

About the Phase 3 Study

The international, multi-center, open-label, controlled Phase 3 study was conducted in Europe, Australia and Canada, and enrolled 463 patients with metastatic colorectal cancer who had failed standard chemotherapy, including oxaliplatin and irinotecan. Patients were randomized to receive panitumumab plus best supportive care (n=231) or best supportive care alone (n=232). Those eligible received panitumumab by intravenous infusion at a dose of 6 mg/kg once every two weeks. There was no requirement that patients receive any pre-medication prior to panitumumab administration.

Best supportive care was defined as the best palliative care available, as judged appropriate by the investigator, and could include antibiotics, analgesics, radiation therapy for pain control (limited to bone metastases), corticosteroids, transfusions, psychotherapy, growth factors, palliative surgery, or any other symptomatic therapy as clinically indicated. For the purposes of this study, best supportive care did not include anti-cancer chemotherapy.

Conference Call Information

Amgen and Abgenix will host a conference call with the investment community today at 8:00 a.m. Pacific Time. Participating in the call will be Roger M. Perlmutter, M.D., Ph.D., executive vice president of Research and Development at Amgen, and Bill Ringo, president and chief executive officer at Abgenix.

Live audio of the conference call will be simultaneously broadcast over the Internet and will be available to members of the news media, investors and the general public.

To participate in the conference call, please dial 877-817-2450 or 706-634-7548 fifteen minutes before start time. The pass code for the live call is 2201994. A telephonic replay of the call will be available by dialing 800-642-1687 or 706-645-9291. The replay participant code is 2201994.

The webcast of the conference can be found on Amgen's Web site,, under Investors, and on Abgenix's Web site, The webcast will be archived and available for replay at least 72 hours after the event.

About Panitumumab

Co-developed by Amgen and Abgenix, panitumumab is the first fully human monoclonal antibody that targets the epidermal growth factor receptor (EGFr), a protein that plays an important role in cancer cell signaling. Panitumumab, an IgG2 monoclonal antibody, binds with high affinity to the EGFr. Panitumumab was generated with Abgenix's XenoMouse(R)(1) technology, which creates a fully human monoclonal antibody that contains no murine (mouse) protein. The body's immune system can recognize the mouse protein found in chimeric antibodies as foreign and launches an immune response in the form of infusion reactions, allergic reactions or anaphylaxis. The goal of developing fully human monoclonal antibodies, which by definition contain no mouse protein, is to offer effective, high affinity therapies that minimize the potential for this type of immune response. Panitumumab is being evaluated in clinical trials as both a monotherapy and in combination with other agents for the treatment of various types of cancer, including colorectal, lung and kidney.

About the Epidermal Growth Factor Receptor (EGFr)

Although EGFr normally helps regulate the growth of many different cells in the body, EGFr also can 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, such as 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 the natural ligands such as 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.

About Colorectal Cancer

Colorectal cancer is the third most common cancer diagnosed in men and in women in the United States. The American Cancer Society estimates that about 104,950 new cases of colon cancer (48,290 men and 56,660 women) and 40,340 new cases of rectal cancer (25,530 men and 16,810 women) will be diagnosed in 2005.

About Amgen

Amgen discovers, develops and delivers innovative human therapeutics. A biotechnology pioneer since 1980, Amgen was one of the first companies to realize the new science's promise by bringing safe and effective medicines from lab, to manufacturing plant, to patient. Amgen therapeutics have changed the practice of medicine, helping millions of people around the world in the fight against cancer, kidney disease, rheumatoid arthritis and other serious illnesses. With a broad and deep pipeline of potential new medicines, Amgen remains committed to advancing science to dramatically improve people's lives. To learn more about our pioneering science and our vital medicines, visit

About Abgenix

Abgenix is a biopharmaceutical company focused on the discovery, development and manufacturing of fully 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 its own development efforts and the establishment of collaborations with multiple pharmaceutical and biotechnology companies. For more information on Abgenix, visit the company's website at

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(1) XenoMouse(R) is a registered trademark of Xenotech, a wholly-owned subsidiary of Abgenix, Inc.

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Amgen, Thousand Oaks
Trish Hawkins, 805-447-4587 (media)
Arvind Sood, 805-447-1060 (investors)
Abgenix, Fremont
Greg Mann, 510-284-6566 (media & investors)