Motavizumab Cuts RSV Burden In High-Risk Infants

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Main Category: Pediatrics / Children's Health
Also Included In: Respiratory / Asthma;  Infectious Diseases / Bacteria / Viruses;  Clinical Trials / Drug Trials
Article Date: 05 May 2008 - 1:00 PST

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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<0.001).

Investigators also documented a 71 percent reduction in outpatient RSV-specific medically-attended ALRIs (9.5 percent for placebo versus 2.8 percent for motavizumab; p<0.001), a secondary study endpoint.

Mortality rates were similarly low in the two treatment groups (0.4 percent for placebo versus 0.3 percent for motavizumab). No deaths were considered to be related to RSV or the active treatment.

Except for a higher rate of skin and subcutaneous reactions occurring within two days of dosing, the monoclonal antibody was well tolerated.

In addition to demonstrating good efficacy and tolerability with motavizumab, the study showed a significant RSV disease burden among Navajo and Apache children. Notably, the RSV hospitalization rate was 83 per 1,000 infants less than one year of age, and the outpatient RSV medically attended lower respiratory infection visit rate among control subjects was 95 per 1,000 infants less than one year of age.

"While the cause of the increased rate RSV infection in this population is not known, what is known is that there is presently no RSV prevention in use for these American Indian infants," Genevieve Losonsky, MD, Vice-President, Clinical Development, Infectious Disease at MedImmune in Gaithersburg, Maryland, noted. "The results are exciting because they show that motavizumab can safely and effectively prevent serious disease caused by RSV in this high-risk population."

She added that this trial is still underway to determine whether children who have undergone immunoprophylaxis with motavizumab have lower rates of recurrent wheezing three years later compared to children who have not been given immunoprophylaxis. "Prior research has suggested that serious RSV disease may be linked to recurrent wheezing in early childhood," she said.

http://www.medimmune.com

Written by Jill Stein
Jill Stein is a Paris based freelance medical writer.
jillstein03{at}gmail.com
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