Prophylactic motavizumab associated with lower RSV hospitalization rates

June 2007

At-risk infants who received motavizumab or palivizumab experienced lowered rates of respiratory syncytial virus-related hospitalization, according to results from a phase-3 trial presented at the Pediatric Academic Societies’ Annual Meeting in Toronto.

Researchers from the Hopital Clinic–Barcelona in Spain and MedImmune Inc. in Gaithersburg, Md., presented safety and efficacy of palivizumab (Synagis, MedImmune) and the humanized monoclonal antibody motavizumab in a multicenter, multinational, randomized, double blind study.

Preclinical study data showed that motavizumab was associated with a 20- to 100-fold increase in activity against RSV, according to the researchers.

“We’re pleased with the results of this trial,” Jessie R. Groothuis, MD, vice president of medical affairs and head of infectious disease/vaccines at MedImmune, said in an interview with Infectious Diseases in Children.

The study included 6,635 preterm infants at 326 clinical sites in 24 countries enrolled over two consecutive RSV seasons. The researchers included 3,326 infants in the palivizumab (Synagis, MedImmune) group and 3,329 infants in the motavizumab group to compare the safety and efficacy of motavizumab and its effects on hospitalizations and medically attended lower respiratory tract infections. Secondary endpoints included immunogenicity, otitis media and medically-attended lower respiratory infections.

All of the infants were preterm infants. The researchers administered either 15 mg/kg of motavizumab or palivizumab to the infants in five monthly intramuscular doses and followed them for 150 days after treatment. They identified RSV by obtaining nasal secretions. Most of the infants (98%) completed the study, according to the researchers.

Infants in the motavizumab experienced a 26% relative reduction in RSV hospitalizations; (P<.01 for non-inferiority compared with the palivizumab group).

The motavizumab group experienced a 50% relative reduction associated with the secondary endpoint of medically attended lower respiratory tract infections, which was a superior efficacy compared with the palivizumab group (2% vs 3.9%, P<.01). The researchers found no other differences in endpoints between the two groups, but there were similar rates of adverse events, serious adverse events and mortality between the two groups. The researchers also found low detectable immunogenicity to motavizumab, which was less than 1% and similar to palivizumab.

For more information:

• Carbonell X, Losonsky G, Micki H, et al. Phase 3 trial of motavizumab (MEDI-524), an enhanced potency respiratory syncytial virus (RSV) specific monoclonal antibody (Mab) for the prevention of serious RSV disease in high risk infants. Abstract 8220.9. Presented at: The Pediatric Academic Societies’ Annual Meeting. May 5-8, 2007; Toronto.