Although the study was designed to establish noninferiority, motavizumab reduced the risk of RSV hospitalization by 26% and the risk of outpatient RSV-related lower respiratory tract infection by 50%.
Prior research has established that palivizumab reduces RSV hospitalizations in children at high risk for severe RSV disease. Preclinical studies, however, have suggested that motavizumab may have even greater efficacy.
In the new study, Dr. Xavier Carbonell-Estrany, from Hospital de Sant Joan de Deu, Barcelona, and colleagues assessed RSV hospitalization and other outcomes in 6635 children who were randomly assigned to receive 15 mg/kg of palivizumab or motavizumab monthly. In terms of eligibility criteria, all of the subjects were born preterm and were either no more than 6 months of age, or up to 24 months of age with chronic lung disease that needed medical treatment within 6 months before randomization.
No significant difference in overall adverse events was noted between the groups. Motavizumab recipients, however, were more likely to have adverse skin effects: 7.2% vs. 5.1% in palivizumab recipients. Most of the skin effects were mild, but 0.3% did lead to drug discontinuation.
Testing for anti-drug antibodies was performed in the motavizumab group, with antibodies found in 1.8%. The presence of anti-motavizumab antibodies correlated with higher rates of RSV hospitalization (6.9% vs. 1.3% without antibodies) and RSV-related lower respiratory tract infection (9.7% vs. 1.9%).
In light of these findings, the authors conclude that “motavizumab may offer an improved alternative in prophylaxis for serious RSV disease in infants and children at high risk.”
The study was sponsored by MedImmune, the developer of both palivizumab and motavizumab. Palivizumab has been available in the US since 1998, while motavizumab is currently in phase II and III studies and being reviewed by the US Food and Drug Administration.