The investigational second-generation humanized monoclonal antibody motavizumab significantly decreases hospitalizations due to respiratory syncytial virus (RSV) and outpatient acute lower respiratory tract infections (ALRIs) in term American Indian infants at high risk of RSV disease, according to interim results of an ongoing phase III study released at the annual meeting of the Pediatric Academic Societies (PAS).

The trial is the first to assess the use of an RSV antibody to prevent serious RSV disease in healthy American Indian infants thought to be at high risk for serious RSV disease.

Kate O'Brien, MD, at Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, along with the American Indian RSV Prevention Study Team, randomized 1,410 term, healthy American Indian infants in a 2:1 design to received five monthly intramuscular (IM) doses of motavizumab, 15 mg/kg, or placebo during their first RSV season.

"Respiratory syncytial virus is a leading cause of ALRIs, including hospitalization in infants," Dr. O'Brien, associate professor of medicine, said. "Otherwise healthy, full-term Navajo, White Mountain Apache and Alaska Native infants have rates of RSV hospitalization that are over three times higher than those of similarly aged children in the general U.S. population and on a par with those among children with underlying conditions."

Study participants were healthy, full-term children who were six months of age or younger at the time of randomization.

The primary endpoint was RSV hospitalizations through day 150.

In an interim intent-to-treat analysis, motavizumab-treated patients had an 83 percent reduction in the incidence of RSV hospitalizations compared to placebo-treated patients (8.3 percent for placebo versus 1.4 percent for motavizumab; p