Ultra-potent antibody motavizumab is safe after second season of rsv prophylaxis

Ultra-potent antibody motavizumab is safe after second season of rsv prophylaxis

The favorable safety profile of the investigational enhanced potency anti-respiratory synctial virus (RSV) monoclonal antibody (MAb) motavizumab, when given for a second consecutive season in high-risk children, is consistent with that seen during the first season, new data indicate.

The findings, from a phase I/II study reported at the 45th Annual Meeting of the Infectious Diseases Society of America (IDSA), also show that motavizumab is as safe as the treatment standard palivizumab (Synagis®).

"Respiratory synctial virus is a major source of lower respiratory infections among young children, with high rates of hospitalization seen in patients with chronic lung and congenital heart diseases," said co-author Genevieve A. Losonsky, MD, vice-president, clinical development, infectious disease, MedImmune, in Gaithersburg, Maryland.

"While prophylaxis of high-risk children with palivizumab is associated with an overall reduction in RSV hospitalization of about 50 percent and is safe and well tolerated, the development of new treatments that offer the potential for additional clinical benefits is desirable."

Dr. Losonsky shared findings in 136 infants who received at least three motavizumab doses in their first RSV season and were randomized to receive five monthly intramuscular injections of motavizumab or palivizumab 15 mg/kg in their second RSV season.

Participants in the trial were 24 months of age or less and were considered at high risk of RSV because they were born at 35 weeks gestation or less or had chronic lung disease because they were born prematurely.

Safety was assessed through 30 days after their fifth and final dose.

The two treatment groups were similar with respect to baseline demographic and clinical characteristics.

Results showed that the incidence and severity of adverse events was similar in motavizumab- and palivizumab-treated patients.

Specifically, the study found that 84.8 percent of the motavizumab group and 88.6 percent of the pavilizumab group experienced an adverse event (AE), with over 95 percent of all considered mild to moderate in both groups. Transient mild erythema at the injection site was the most common drug-related AE in each group, occurring in 15.2 percent versus 11.4 percent of the two groups, respectively.

Serious AEs occurred in four (6.1 percent) patients in the motavizumab group, only one of which was thought to be possibly related to the study treatment.

Anti-motavizumab binding activity was not detected during treatment through 90 to 120 days after the final dose in any patient who received motavizumab for a second RSV season.

In addition, motivizumab serum trough concentrations during a second season of treatment were comparable to those achieved during the first season.

"Based on our observations, it appears that motavizumab or palivizumab can be safely administered for a second consecutive RSV season in high-risk patients who received motavizumab during their first RSV season," Dr. Losonsky said.

To date, motavizumab has been shown to have clinical activity in preventing serious RSV disease in high-risk children in two efficacy trials. In a phase 3 trial that compared motavizumab and palivizumab, motavizumab demonstrated non-inferiority to palivizumab with a 26 percent relative reduction in the primary endpoint of RSV hospitalizations. In a placebo-controlled, phase 3 trial, motavizumab reduced RSV hospitalizations by 83 percent in high-risk Native American, full-term infants - a population known to be at high risk of RSV hospitalizations.

By Jill Stein

Jill Stein is a Paris-based medical writer

Jillstein03 at cs.com

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