HONOLULU, HI, May 4, 2008 – MedImmune today announced that researchers are currently presenting results from a MedImmune-sponsored Phase 3 study involving motavizumab, an investigational monoclonal antibody (MAb) that is being evaluated for its potential to prevent serious disease caused by respiratory syncytial virus (RSV) in high-risk pediatric patients. Kate O’Brien, M.D., M.P.H., associate professor at the Center for American Indian Health, Johns Hopkins Bloomberg School of Public Health, is the study’s principal investigator. Aruna Chandran, M.D., M.P.H., a trial co-investigator, presents the data today at the Pediatric Academic Societies (PAS) Annual Meeting in Honolulu, HI.

This randomized Phase 3 study demonstrated that motavizumab reduced hospitalizations due to RSV by 83 percent as compared to placebo (8.3 percent in placebo arm versus 1.4 percent in motavizumab; p<0.001), as the trial’s primary endpoint. In addition, the trial showed a 71-percent reduction in the incidence of RSV-specific lower respiratory infections (LRIs) requiring outpatient management (9.5 percent in placebo group and 2.8 percent in the motavizumab group; p<0.001), which was a secondary endpoint.

The randomized, double-blind Phase 3 study involving 1,410 full-term healthy infants less than six months of age in some Southwest Native American populations was designed to compare monthly intramuscular injections of motavizumab against placebo. In previous epidemiologic studies these populations were shown to have high rates of hospitalization due to RSV. This study confirmed the high rates of serious RSV disease in this population. An interim analysis, reviewed by an independent data safety monitoring committee, concluded there was statistical evidence demonstrating that motavizumab reduced RSV hospitalizations and LRIs requiring outpatient medical management within this population.

The overall incidence and severity of adverse events (AEs) were similar between the motavizumab and the placebo groups in these Native American infants. The mortality rates were not statistically different between groups (0.4 percent in the placebo arm, n=2 and 0.3 percent in the motavizumab arm, n=3) and were not considered to be related to the study drug. As was suggested in the pivotal Phase 3 trial conducted in high-risk, preterm infants, rates of skin reactions were more common following motavizumab than placebo (by an approximately 2 percent increase in frequency). Motavizumab was otherwise well tolerated.