Amgen and Abgenix Complete Biologics License Application for FDA Approval of Panitumumab.

THOUSAND OAKS, Calif. & FREMONT, Calif. -- Amgen (Nasdaq: AMGN) and Abgenix, Inc. (Nasdaq: ABGX) today announced that Amgen has completed the Biologic License Application (BLA) submission with the U.S. Food and Drug Administration (FDA) for panitumumab. The potential indication is for the treatment of metastatic colorectal cancer in patients who have failed prior chemotherapy, including oxaliplatin and/or irinotecan containing regimens. The rolling BLA submission was initiated in December 2005.

"The pivotal Phase 3 study of panitumumab not only met the primary endpoint of improving progression-free survival in patients with metastatic colorectal cancer, but the results surpassed our expectations based on preset measurement criteria in the protocol," said Willard Dere, M.D., chief medical officer and senior vice president of Global Development at Amgen. "Completing the BLA brings us one step closer to realizing our goal of making panitumumab accessible to patients with metastatic colorectal cancer who have failed available treatment options."

Amgen and Abgenix previously announced that data from a randomized Phase 3 trial involving 463 patients showed that 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 0.000 000 001). The most common side effect was acneiform rash. Other side effects less commonly observed were fatigue, nausea and mild diarrhea.

Results from this pivotal Phase 3 study will be presented in a Clinical Plenary Session at the 97th Annual Meeting of the American Association for Cancer Research on April 3, 2006. Amgen will host a webcast with the investment community to discuss the results on Monday, April 3, 2006, at 12:30 P.M. EDT. Open to members of the news media, investors and the general public, the webcast can be found on Amgen's Web site, www.amgen.com, under Investors. It will be archived and available for replay at least 72 hours after the event.

About Panitumumab

Panitumumab is an investigational 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 XenoMouse(R) 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 and humanized antibodies as foreign and launch an immune response in the form of infusion reactions, allergic reactions or anaphylaxis. The goal of developing fully human monoclonal antibodies is to offer effective, high affinity therapies that minimize the potential for this type of immune response.

Panitumumab received Fast Track designation from the U.S. Food and Drug Administration (FDA) in July 2005 for patients with metastatic colorectal cancer who have failed standard chemotherapy treatment. It 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 head and neck.

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 106,680 new cases of colon cancer and 41,930 new cases of rectal cancer will be diagnosed in 2006.

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 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 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 www.abgenix.com.

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, 2005, 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.

No forward-looking statement can be guaranteed and actual results may differ materially from those Amgen projects. Discovery or identification of new product candidates or development of new indications for existing products cannot be guaranteed and movement from concept to product is uncertain; consequently, there can be no guarantee that any particular product candidate or development of a new indication for an existing product will be successful and become a commercial product. Further, preclinical results do not guarantee safe and effective performance of product candidates in humans. The complexity of the human body cannot be perfectly, or sometimes, even adequately modeled by computer or cell culture systems or animal models. The length of time that it takes for Amgen to complete clinical trials and obtain regulatory approval for product marketing has in the past varied and Amgen expects similar variability in the future. Amgen develops product candidates internally and through licensing collaborations, partnerships and joint ventures. Product candidates that are derived from relationships may be subject to disputes between the parties or may prove to be not as effective or as safe as Amgen may have believed at the time of entering into such relationship. Also, Amgen or others could identify side effects or manufacturing problems with Amgen's products after they are on the market. In addition, sales of Amgen's products are affected by the availability of reimbursement and the reimbursement policies imposed by third party payors, including governments, private insurance plans and managed care providers, and may be affected by domestic and international trends toward managed care and healthcare cost containment as well as possible U.S. legislation affecting pharmaceutical pricing and reimbursement. Government regulations and reimbursement policies may affect the development, usage and pricing of Amgen's products. In addition, Amgen competes with other companies with respect to some of Amgen's marketed products as well as for the discovery and development of new products. Amgen believes that some of the newer products, product candidates or new indications for existing products, may face competition when and as they are approved and marketed. Amgen products may compete against products that have lower prices, established reimbursement, superior performance, are easier to administer, or that are otherwise competitive with our products. In addition, while Amgen routinely obtains patents for Amgen's products and technology, the protection offered by Amgen's patents and patent applications may be challenged, invalidated or circumvented by Amgen's competitors and there can be no guarantee of Amgen's ability to obtain or maintain patent protection for Amgen's products or product candidates. Amgen cannot guarantee that it will be able to produce commercially successful products or maintain the commercial success of Amgen's existing products. Amgen's stock price may be affected by actual or perceived market opportunity, competitive position, and success or failure of Amgen's products or product candidates. Further, the discovery of significant problems with a product similar to one of Amgen's products that implicate an entire class of products could have a material adverse effect on sales of the affected products and on Amgen's business and results of operations.

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 FDA can 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 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

Statements made in this press release about Abgenix's technologies, product development activities, collaborative arrangements and the proposed merger with Amgen, other than statements of historical fact, are forward-looking statements and are subject to a number of uncertainties that could cause actual results to differ materially from the statements made. For example, statements regarding the expected timing of the closing of the merger are forward-looking statements. Factors that could cause actual results to differ materially from those contemplated above include, among others, the risks associated with the timing and success of clinical trials, the progress of research and product development programs, product manufacturing, consummating the merger with Amgen, timing and outcomes of regulatory approval processes, competitive products and services, litigation and the extent and breadth of Abgenix's patent portfolio. Please see Abgenix's public filings with the Securities and Exchange Commission (SEC) for information about risks that may affect Abgenix, including its Form 10-K for the year ended December 31, 2005, and reports on Form 10-Q and Form 8-K.

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