News Pressroom

May 14, 2005

Additional Safety Data Presented at PAS Annual Meeting on MedImmune's Next-Generation Product to Help Prevent RSV Disease in High-Risk Infants

- Pivotal Phase 3 Efficacy Trial for Numax(TM) Underway -

WASHINGTON, May 14, 2005 /PRNewswire-FirstCall via COMTEX/ -- MedImmune, Inc. (Nasdaq: MEDI) announced today data from a Phase 1/2 study demonstrating that Numax appears to be safe and well tolerated, with an acceptable pharmacokinetic profile, in infants at high risk of respiratory syncytial virus (RSV) disease. MedImmune is developing Numax as a potential improvement to Synagis(R) (palivizumab), which it introduced to the market in 1998 and has become the standard of care for protecting high-risk infants against RSV. To date, Synagis has successfully helped to reduce the incidence of serious lower respiratory tract illness in more than 700,000 high-risk infants.

"Numax has been shown in preclinical studies to be more potent than Synagis in reducing RSV replication in both the lower and upper respiratory tract," said Genevieve Losonsky, M.D., senior director, clinical development. "Our development goals for Numax are to fully assess its safety and to evaluate if the increased potency seen in preclinical studies can be translated into better efficacy against RSV hospitalizations, medically attended lower respiratory tract illness and upper respiratory tract disease, such as otitis media (middle ear infections)."

An abstract presented today at the annual meeting of the Pediatric Academic Societies in Washington, DC was entitled "Phase 1/2 Trial in High- Risk Infants of MEDI-524 (Numax(TM)) an Enhanced Potency Respiratory Syncytial Virus (RSV) Specific Monoclonal Antibody." The dose-escalation trial was conducted in North and South America and included 217 preterm infants (32-35 weeks gestational age) and infants with chronic lung disease of prematurity two years of age or younger. Each participant received up to five monthly intramuscular injections of Numax and had completed evaluations through 90 days after the final dose for safety, immunogenicity and pharmacokinetics.

In March, MedImmune presented results from Phase 1 and 2 studies of Numax, including data that showed Numax was present in the nasal secretions of patients receiving the antibody and inhibited viral replication in the nose. These results were presented at the 7th International Symposium on Respiratory Viral Infections in Curacao. More recently, MedImmune also initiated a Phase 2, second-season study to determine the safety of re-dosing children who received Numax in a prior RSV season.

RSV is the most common respiratory infection in infancy or childhood, resulting in more than 125,000 hospitalizations in the U.S. annually in children less than one year of age. Children born prematurely as well as those with chronic lung disease or congenital heart disease are at highest risk of severe disease and hospitalization due to RSV.

About Numax

Numax is a humanized monoclonal antibody currently being developed to potentially prevent serious lower respiratory tract disease caused by RSV in pediatric patients at high-risk of RSV disease. In November 2004, MedImmune initiated a pivotal worldwide Phase 3 study comparing the safety and efficacy of Numax in reducing RSV disease in high-risk infants to that of Synagis. A Phase 3 study is also underway to evaluate the safety and efficacy of Numax in healthy Native American infants.

About Synagis

Synagis is marketed for the prevention of serious lower respiratory tract disease caused by RSV in pediatric patients at high-risk of RSV disease, which is prominent in the Northern Hemisphere during the winter months. Synagis is a humanized MAb given through an intramuscular injection once a month during the RSV season. Synagis was approved in 1998 by the U.S. Food and Drug Administration (FDA), in 1999, by the European Medicines Evaluation Agency, and in 2002, by the Japanese Ministry of Health, Labor and Welfare. In 2003, the FDA expanded the U.S. label for Synagis for use in young children with hemodynamically significant congenital heart disease at risk of RSV disease. To date, Synagis has been approved in 62 countries, including the United States. The adverse reactions most commonly observed in Synagis-treated patients have been upper respiratory tract infection, ear infection, fever, runny nose, rash, diarrhea, cough, vomiting, gastroenteritis and wheezing. Very rare cases of severe allergic reactions such as anaphylaxis (less than one case per 100,000 patients) and hypersensitivity reactions have been reported. Synagis should not be used in patients with a history of a severe prior reaction to Synagis or its components. For full prescribing information for Synagis, see the company's website at http://www.medimmune.com.

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 Numax. Such statements reflect management's current views 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, Numax will receive required regulatory clearance or, even if such regulatory clearance is received, that Numax will ultimately achieve commercial success.

SOURCE MedImmune, Inc.

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