Amgen to Acquire Abgenix for $22.50 Per Share; Provides Amgen With Full Ownership of Panitumumab and Eliminates a Denosumab Royalty

Amgen (Nasdaq: AMGN), the world's largest biotechnology company,and Abgenix, Inc. (Nasdaq: ABGX), a company specializing in thediscovery, development and manufacture of human therapeuticantibodies, today announced that they have signed a definitive mergeragreement under which Amgen will acquire Abgenix for approximately$2.2 billion in cash plus the assumption of debt. Under the terms ofthe agreement, shareholders of Abgenix will receive $22.50 in cash percommon share.

The acquisition of Abgenix provides Amgen with full ownership ofone of its most important advanced pipeline products, panitumumab.Working closely with Abgenix under a co-development agreement thatAmgen assumed as a result of its acquisition of Immunex Corporation in2002, Amgen has led the development and commercialization strategy forpanitumumab. The acquisition provides additional value to Amgen byeliminating a tiered royalty that Amgen would have paid to Abgenix onfuture sales of denosumab (formerly AMG 162), which was created usingAbgenix's XenoMouse(R) antibody technology.

"Abgenix is a natural strategic fit for Amgen given our strongexisting relationship. Amgen has been intimately involved in allaspects of the development and commercialization of panitumumab overthe last few years, providing us with substantial and realisticinsight into the value of, and significant opportunities for, thiscancer therapeutic. This investment reflects Amgen's commitment to ourpipeline and our growing confidence in the future success of bothpanitumumab and denosumab," said Kevin Sharer, president and chiefexecutive officer of Amgen.

Amgen and Abgenix believe panitumumab has substantial commercialopportunity, including potential in the first-line treatment ofmetastatic colorectal cancer (CRC) in combination with other agents,including anti-angiogenic therapies. Panitumumab is the firstepidermal growth factor receptor (EGFr) inhibitor to demonstrate astatistically significant improvement in progression-free survival formetastatic colorectal cancer patients who have failed standardchemotherapy. Panitumumab is also the first fully human monoclonalantibody in cancer clinical trials that targets the epidermal growthfactor receptor. Amgen believes that potential peak worldwide salesfor panitumumab could reach $2 billion or more, assuming success ofpanitumumab in several clinical trials evaluating multiple lines oftherapy in colorectal cancer and head and neck cancer.

Later this week, Amgen and Abgenix expect to initiate a biologicslicense application (BLA) for the treatment of metastatic colorectalcancer patients who have failed standard chemotherapy. Panitumumab isAmgen's and Abgenix's most advanced cancer therapeutic and is anatural extension from Amgen's existing oncology supportive carefranchise.

"Combining with Amgen provides an attractive valuation for ourshareholders. We believe this transaction will allow us to advancepanitumumab to its full potential for patients and to maximize thevalue of both Abgenix's growing portfolio of antibody productcandidates and our exceptional scientific platform," said Bill Ringo,president and chief executive officer of Abgenix. "We have workedclosely with Amgen for many years and are very excited about combiningAbgenix with the leader in the biotech industry."

The transaction includes the Abgenix 100,000 square footmanufacturing plant in Fremont, Calif., which will produce panitumumaband add to Amgen's protein manufacturing capabilities. Abgenix alsobrings scientific knowledge and assets, such as the ownership andcapabilities of the proprietary fully human monoclonal antibodytechnology, XenoMouse.

Transaction Terms

Under the terms of the agreement, which has been unanimouslyapproved by the Boards of Directors of both companies, Amgen will payshareholders of Abgenix $22.50 in cash per common share for a totalvalue of approximately $2.2 billion and will assume Abgenixoutstanding debt. The acquisition is subject to the approvals ofAbgenix's shareholders and regulatory authorities, and to othercustomary closing conditions. The transaction is expected to becompleted by the end of the first quarter of 2006. Funds will beprovided from Amgen's cash on hand at the time of closing.

Amgen expects dilution of adjusted earnings per share in 2006 and2007 in the range of $0.05 to $0.10, with impact to adjusted earningsper share expected to be accretive thereafter, assuming commercialsuccess of panitumumab.

Amgen expects to retain substantially all of the Abgenixmanufacturing employees. Amgen and Abgenix will be reviewing ongoingbusiness needs and opportunities at Amgen with Abgenix's employees inthe coming months.

Conference Call and Webcast Information

Amgen and Abgenix will host a conference call and webcast forinvestors and analysts today at 2:00 PM Pacific Time to discuss thetransaction. Live audio of the conference call will be simultaneouslybroadcast over the Internet and will be available to members of thenews media, investors and the general public.

To participate in the conference call, please dial 877-817-2450(U.S. and Canada) or 706-634-7548 (international) fifteen minutesbefore start time. The pass code for the live call is 3416104. Atelephonic replay of the call will be available by dialing800-642-1687 (U.S. and Canada) or 706-645-9291 (international). Thereplay participant code is 3416104.

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 Denosumab

Denosumab is designed to target RANK Ligand, a protein that actsas the primary signal to promote bone removal. Preclinical models havedemonstrated that inhibiting RANK Ligand leads to improvements incortical and trabecular bone density, volume and strength. Denosumabis currently being studied for its potential in the treatment of abroad range of bone loss conditions including osteoporosis, treatmentinduced bone loss, bone metastases, multiple myeloma, and rheumatoidarthritis.

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.

Amgen Forward-Looking Statement

This press release contains forward-looking statements within themeaning of the "safe harbor" provisions of the Private SecuritiesLitigation Reform Act of 1995, including statements about futurefinancial and operating results and Amgen's anticipated acquisition ofAbgenix. These statements are based on management's currentexpectations and beliefs and are subject to a number of risks,uncertainties and assumptions that could cause actual results todiffer materially from those described in the forward-lookingstatements. All statements other than statements of historical factare statements that could be deemed forward-looking statements. Forexample, statements of expected synergies, dilution and accretion,financial guidance, peak sales, timing of closing, industry ranking,execution of integration plans and management and organizationalstructure are all forward-looking statements. Risks, uncertainties andassumptions include the possibility that the development of certainproducts may not develop as expected or proceed as planned; that theacquisition does not close or that the companies may be required tomodify aspects of the transaction to achieve regulatory approval; thatprior to the closing of the acquisition, the businesses of thecompanies suffer due to uncertainty; that the parties are unable tosuccessfully execute their integration strategies, or achieve plannedsynergies, as well as other risks that are discussed below and othersthat can be found in Amgen's and Abgenix's

Form 10-K for the year ended December 31, 2004, and in Amgen'speriodic reports on Form 10-Q and Form 8-K. Amgen is providing thisinformation as of the date of this news release and does not undertakeany obligation to update any forward-looking statements contained inthis document as a result of new information, future events orotherwise.

No forward-looking statement can be guaranteed and actual resultsmay differ materially from those we project. Amgen's results may beaffected by its ability to successfully market both new and existingproducts domestically and internationally, sales growth of recentlylaunched products, difficulties or delays in manufacturing ourproducts, and regulatory developments (domestic or foreign) involvingcurrent and future products and manufacturing facilities. Discovery oridentification of new product candidates or development of newindications for existing products cannot be guaranteed and movementfrom concept to product is uncertain; consequently, there can be noguarantee that any particular product candidate or development of anew indication for an existing product will be successful and become acommercial product. The length of time that it takes for Amgen tocomplete clinical trials and obtain regulatory approval for productmarketing has in the past varied and Amgen expects similar variabilityin the future. Further, only the FDA can determine whether the productcandidates are safe and effective for the use(s) being investigated.In addition, sales of Amgen's products are affected by reimbursementpolicies imposed by third party payors, including governments, privateinsurance plans and managed care providers, and may be affected bydomestic and international trends toward managed care and healthcarecost containment as well as possible U.S. legislation affectingpharmaceutical pricing and reimbursement. Government regulations andreimbursement policies may affect the development, usage and pricingof our products. In addition, Amgen competes with other companies withrespect to some of Amgen's marketed products as well as for thediscovery and development of new products. Amgen, or others couldidentify side effects or manufacturing problems with Amgen's productsafter they are on the market. Furthermore, our research, testing,pricing, marketing and other operations are subject to extensiveregulation by domestic and foreign government regulatory authorities.In addition, while we routinely obtain patents for our products andtechnology, the protection offered by our patents and patentapplications may be challenged, invalidated or circumvented by ourcompetitors. Further, some raw materials, medical devices, andcomponent parts for our products are supplied by sole first partysuppliers.

Abgenix Forward-Looking Statement

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.

Participants in Solicitation

Amgen Inc. ("Amgen") and Abgenix, Inc. ("Abgenix") and theirrespective directors and executive officers may be deemed to beparticipants in the solicitation of proxies from Abgenix stockholdersin connection with the merger. Information about the directors andexecutive officers of Amgen and their ownership of Amgen's stock isset forth in the proxy statement for Amgen's 2005 Annual Meeting ofStockholders. Information about the directors and executive officersof Abgenix and their ownership of Abgenix's stock is set forth in theproxy statement for Abgenix's 2005 Annual Meeting of Stockholders.

Additional Information About the Acquisition and Where to Find It

This communication may be deemed to be solicitation material inrespect of the proposed acquisition of Abgenix by Amgen. In connectionwith the proposed acquisition, Amgen and Abgenix intend to filerelevant materials with the SEC, including Abgenix's proxy statement.STOCKHOLDERS OF ABGENIX ARE URGED TO READ ALL RELEVANT DOCUMENTS FILEDWITH THE SEC, INCLUDING ABGENIX'S PROXY STATEMENT, BECAUSE THEY WILLCONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION.Investors will be able to obtain the documents free of charge at theSEC's web site, http://www.sec.gov, and Abgenix stockholders willreceive information at an appropriate time on how to obtaintransaction-related documents for free from Abgenix. Such documentsare not currently available.

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