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

Amgen (Nasdaq:AMGN) and Abgenix, Inc. (Nasdaq:ABGX) todayannounced that a pivotal Phase 3 study of panitumumab met the primaryendpoint of improving progression-free survival in patients withmetastatic colorectal cancer (mCRC) who had failed standardchemotherapy. In this randomized Phase 3 trial involving 463 patients,those who received panitumumab every two weeks showed a 46 percentdecrease in tumor progression rate versus those who received bestsupportive care alone (p less than 0.000000001).

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

"Amgen is dedicated to developing safe and effective cancertherapies that significantly improve cancer patients' outcomes," saidWillard Dere, M.D., chief medical officer and senior vice president ofGlobal Development at Amgen. "We are excited that panitumumab, ourmost advanced investigational cancer therapeutic, improvedprogression-free survival and response rate in metastatic colorectalcancer patients who had failed multiple prior chemotherapy regimens.These results will support a BLA submission, which we plan to initiateby the end of the year."

"We are very encouraged by the results of this pivotal study andwhat panitumumab could mean for patients with advanced colorectalcancer," said Bill Ringo, president and chief executive officer ofAbgenix. "The improvement in progression-free survival shown bypanitumumab in this study highlights the value of our proprietarytechnology and product development capabilities. We continue to workclosely with our partner, Amgen, towards the regulatory filing andpotential commercialization of panitumumab."

Per protocol, administration of panitumumab did not requireadministration of pre-medication or a loading dose, and the incidenceof infusion reactions (of any severity) was low. An initial safetyevaluation showed that the adverse events observed were consistentwith previous clinical studies of panitumumab. The most common sideeffect was acneiform rash. Other side effects less commonly observedwere 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 forpresentation at a medical meeting in 2006.

Panitumumab received Fast Track designation from the U.S. Food andDrug Administration (FDA) in July 2005. Amgen and Abgenix are workingtoward initiating the submission of the Biologics License Application(BLA) to the FDA for panitumumab in patients who have failed priorstandard chemotherapy, including oxaliplatin and irinotecan, by theend of 2005. FDA has previously indicated that data from one pivotaltrial, once completed, could be acceptable with additional data fromother ongoing studies to support a submission for marketing approvalin the United States. The completed submission of the BLA is expectedin the first quarter of 2006.

Currently, panitumumab is being investigated as a single agent orin combination with other agents across multiple lines of treatmentfor various cancers. Patients and physicians can accesswww.amgentrials.com for more information about ongoing panitumumabclinical trials.

About the Phase 3 Study

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

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

Conference Call Information

Amgen and Abgenix will host a conference call with the investmentcommunity today at 8:00 a.m. Pacific Time. Participating in the callwill be Roger M. Perlmutter, M.D., Ph.D., executive vice president ofResearch and Development at Amgen, and Bill Ringo, president and chiefexecutive officer at Abgenix.

Live audio of the conference call will be simultaneously broadcastover 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 or706-634-7548 fifteen minutes before start time. The pass code for thelive call is 2201994. A telephonic replay of the call will beavailable by dialing 800-642-1687 or 706-645-9291. The replayparticipant code is 2201994.

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

About Panitumumab

Co-developed by Amgen and Abgenix, panitumumab is the first fullyhuman monoclonal antibody that targets the epidermal growth factorreceptor (EGFr), a protein that plays an important role in cancer cellsignaling. Panitumumab, an IgG2 monoclonal antibody, binds with highaffinity to the EGFr. Panitumumab was generated with Abgenix'sXenoMouse(R)(1) technology, which creates a fully human monoclonalantibody that contains no murine (mouse) protein. The body's immunesystem can recognize the mouse protein found in chimeric antibodies asforeign and launches an immune response in the form of infusionreactions, allergic reactions or anaphylaxis. The goal of developingfully human monoclonal antibodies, which by definition contain nomouse protein, is to offer effective, high affinity therapies thatminimize the potential for this type of immune response. Panitumumabis being evaluated in clinical trials as both a monotherapy and incombination with other agents for the treatment of various types ofcancer, including colorectal, lung and kidney.

About the Epidermal Growth Factor Receptor (EGFr)

Although EGFr normally helps regulate the growth of many differentcells in the body, EGFr also can stimulate cancer cells to grow. Infact, many cancer cells actually require signals mediated by EGFr fortheir survival. Residing on the surface of these tumor cells, EGFr isactivated when naturally occurring proteins in the body, such asepidermal 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 stimulatetumor cell growth. Panitumumab binds to EGFr, preventing the naturalligands such as EGF and TGF-alpha from binding to the receptor andinterfering with the signals that would otherwise stimulate growth ofthe cancer cell and allow it to survive.

About Colorectal Cancer

Colorectal cancer is the third most common cancer diagnosed in menand in women in the United States. The American Cancer Societyestimates that about 104,950 new cases of colon cancer (48,290 men and56,660 women) and 40,340 new cases of rectal cancer (25,530 men and16,810 women) will be diagnosed in 2005.

About Amgen

Amgen discovers, develops and delivers innovative humantherapeutics. A biotechnology pioneer since 1980, Amgen was one of thefirst companies to realize the new science's promise by bringing safeand effective medicines from lab, to manufacturing plant, to patient.Amgen therapeutics have changed the practice of medicine, helpingmillions 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, Amgenremains committed to advancing science to dramatically improvepeople's lives. To learn more about our pioneering science and ourvital medicines, visit www.amgen.com.

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 leadingtechnology and state-of-the-art manufacturing capabilities that enablethe rapid generation, selection and production of high affinity, fullyhuman antibody product candidates to a variety of disease targets.Abgenix leverages its leadership position in human antibody technologyto build a diversified product portfolio through its own developmentefforts and the establishment of collaborations with multiplepharmaceutical and biotechnology companies. For more information onAbgenix, visit the company's website at www.abgenix.com.

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Statements made in this press release about Abgenix'stechnologies, product development activities and collaborativearrangements, other than statements of historical fact, areforward-looking statements and are subject to a number ofuncertainties that could cause actual results to differ materiallyfrom the statements made, including risks associated with the timingand success of clinical trials, the progress of research and productdevelopment programs, product manufacturing, timing and outcomes ofregulatory approval processes, competitive products and services, andthe extent and breadth of Abgenix's patent portfolio. Please seeAbgenix's public filings with the Securities and Exchange Commissionfor information about risks that may affect Abgenix, including itsForm 10-K for the year ended December 31, 2004, and periodic reportson Form 10-Q and Form 8-K.

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

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