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August 29, 2005

MedImmune Licenses Worldwide Rights for Anti-Staphylococcal Antibody Program From GlaxoSmithKline

Company Reinforces Commitment to Fighting Pediatric Infectious Diseases

GAITHERSBURG, Md., Aug 29, 2005 /PRNewswire-FirstCall via COMTEX/ -- MedImmune, Inc. (Nasdaq: MEDI) announced today that it has licensed worldwide rights from GlaxoSmithKline (NYSE: GSK) to develop certain anti-staphylococcal monoclonal antibodies (MAbs). The program includes BSYX-A110, which is in Phase 2 clinical development for the prevention of serious bloodstream infections caused by Staphylococcus in low-birthweight infants. MedImmune will be responsible for future research and development of BSYX-A110 and any resulting second-generation MAbs as well as all future sales and marketing activities worldwide.

Under the terms of the agreement, MedImmune will pay GSK an upfront payment upon signing as well as potential milestone payments and royalties on future marketed products. MedImmune has also assumed responsibility for future milestone and royalty payment obligations to Biosynexus, from which GSK originally licensed the BSYX-A110 antibody and related rights in 2002. Biosynexus may continue to provide scientific input regarding future R&D activities for the program.

"Adding BSYX-A110 into the pipeline provides an opportunity for us to leverage MedImmune's clinical, regulatory and commercial experience in the development of monoclonal antibodies in pediatrics," said Edward M. Connor, M.D., executive vice president and chief medical officer. "BSYX-A110 is targeted against Staphylococcus, including coagulase negative Staphylococcus (CONS), which is a leading cause of bloodstream infections among infants in the neonatal intensive care unit (NICU). If we succeed in bringing this antibody to market, we may be able to provide pediatricians with a new tool for protecting the health of these infants."

According to the United States Census Bureau, approximately 43,000 infants weighing less than 1,250 grams at birth were born in 2001. These low- birthweight infants are particularly susceptible to hospital-acquired infections, such as those caused by Staphylococcus. Among infants in the NICU, hospital-acquired infection rates range from six to 25 percent. Reports in medical literature suggest that CONS increases an infant's hospital stay by 20 to 40 days at an additional cost of $60,000 to $200,000.

About BSYX-A110

BSYX-A110 is a monoclonal antibody in development for the prevention of staphylococcal infections in premature infants. BSYX-A110 binds to staphylococci and promotes ingestion and destruction of the bacteria. Data acquired from Phase 1 and 2 clinical studies conducted to date with BSYX-A110 suggest that the antibody is well-tolerated in adults and infants. Data are currently being analyzed from a Phase 2 double-blind, placebo-controlled safety/pharmacokinetic study in infants and an epidemiological study of the incidence of bloodstream infections in premature infants.

About MedImmune, Inc.

MedImmune strives to provide better medicines to patients, new medical options for physicians, rewarding careers to employees, and increased value to shareholders. Dedicated to advancing science and medicine to help people live better lives, the company is focused on the areas of infectious diseases, cancer and inflammatory diseases. With approximately 2,000 employees worldwide, MedImmune is headquartered in Maryland. For more information, visit the company's website at http://www.medimmune.com.

This announcement contains, in addition to historical information, certain forward-looking statements that involve risks and uncertainties, in particular, related to the research and development of BSYX-A110 and future related products. Such statements reflect the current views of MedImmune management and are based on certain assumptions. Actual results could differ materially from those currently anticipated as a result of a number of factors, including risks and uncertainties discussed in MedImmune's filings with the U.S. Securities and Exchange Commission. There can be no assurance that such development efforts will succeed, that the products will receive required regulatory clearance or, even if such regulatory clearance is received, that the subsequent products will ultimately achieve commercial success.

SOURCE MedImmune, Inc.

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