Abgenix and Amgen Clarify Responsibilities for ABX-EGF

FREMONT and THOUSAND OAKS, Calif. – October 14, 2003 – Abgenix (Nasdaq: ABGX) and Amgen Inc. (Nasdaq: AMGN) today announced that Abgenix and Amgen's wholly owned subsidiary, Immunex Corporation, have amended their agreement for ABX-EGF to clarify clinical development, manufacturing and commercialization responsibilities. ABX-EGF, a fully human monoclonal antibody directed against the epidermal growth factor receptor (EGFr), is in multiple clinical studies for several oncology indications.

Under the amended agreement, Immunex will have decision-making authority for development and commercialization activities. Under a separate agreement, Abgenix will manufacture both clinical and early commercial supplies of ABX-EGF with Immunex's support and assistance. The companies will continue to share program costs equally, as well as worldwide operating profits from future sales of ABX-EGF.

“We believe this amended agreement provides the optimal structure to advance the ABX-EGF program quickly and efficiently,” said Dr. Raymond Withy, CEO and President of Abgenix. “Our manufacturing capabilities will be critical to the late stage development and potential launch of this exciting product candidate.”
Under the amendment, Immunex will make available to Abgenix $60 million in the form of advances that may be used by Abgenix to fund its share of development and commercialization costs for ABX-EGF after Abgenix has contributed $20 million toward development costs in 2004. The amount of any advances drawn by Abgenix, plus interest, may be repaid out of profits resulting from future product sales. However, Abgenix is not obligated to repay any portion of the loan if ABX-EGF does not reach commercialization.

ABX-EGF targets the epidermal growth factor receptor (EGFr), which is over-expressed in a variety of cancers including lung, breast, pancreatic, bladder, prostate, colorectal, kidney, and head and neck cancers. Research has demonstrated that cancer cells can become dependent on growth signals mediated through EGFr for their survival. In preclinical research, ABX-EGF monotherapy has been shown to inhibit the growth of human tumors in mice.

Co-developed by Abgenix and Immunex, ABX-EGF is being evaluated in a comprehensive clinical program in several indications. Results of several clinical studies have demonstrated single-agent activity and a favorable pharmacokinetic and tolerability profile.

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 website at www.abgenix.com.

Statements made in this press release about Abgenix's technologies, product development activities, collaborative arrangements and manufacturing activities, other than statements of historical fact, and about its projected financial results, are forward-looking statements and are subject to a number of uncertainties that could cause actual results to differ materially from the statements made, including risks associated with the success of clinical trials, the progress of research and product development programs, product manufacturing, the regulatory approval process, competitive products, future capital requirements and the extent and breadth of Abgenix's patent portfolio. Please see Abgenix's public filings with the Securities and Exchange Commission for information about risks that may affect Abgenix.

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.

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, 2002, 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 we project. Amgen's results may be affected by its ability to successfully market both new and existing products domestically and internationally, sales growth of recently launched products, difficulties or delays in manufacturing its products, and regulatory developments (domestic or foreign) involving current and future products and manufacturing facilities. In addition, sales of Amgen's products are affected by 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. Furthermore, Amgen's research, testing, pricing, marketing and other operations are subject to extensive regulation by domestic and foreign government regulatory authorities. Amgen or others could identify side effects or manufacturing problems with its products after they are on the market. In addition, Amgen competes with other companies with respect to some of its marketed products as well as for the discovery and development of new products. Discovery or identification of new product candidates cannot be guaranteed and movement from concept to product is uncertain; consequently, there can be no guarantee that any particular product candidate will be successful and become a commercial product. In addition, while Amgen routinely obtain patents for its products and technology, the protection offered by its patents and patent applications may be challenged, invalidated or circumvented by its competitors. Further, some raw materials, medical devices and component parts for Amgen's products are supplied by sole third party suppliers.