Palivizumab (Synagis) is a humanized monoclonal anti-body directed against the highly conserved A antigenic site of the F protein on the surface of RSV. It contains 95% human and 5% murine antibody sequences and tends to have little immunogenicity in humans. Palivizumab is composed of the human framework re-gion of the IgG-1 -chain joined to the antigen-binding regions of a mouse monoclonal antibody. Palivizumab neutralizes RSV and inhibits its ability to fuse with host cell membranes. Resistant strains of RSV have been de-rived in vitro but have not been found in clinical isolates to date.
Palivizumab is administered prophylactically as a monthly intramuscular injection prior to and during RSV season (November to April in the northern hemi-sphere). The half-life of palivizumab is approximately 20 days.
Palivizumab is used to prevent serious lower respiratory tract infection due to RSV. It is used only in high-risk children who are younger than 24 months of age and have bronchopulmonary dysplasia or chronic lung dis-ease that required treatment in the previous 6 months. It is also indicated for premature infants (less than 32 weeks’ gestation) until the age of 6 to 12 months. Palivizumab can reduce the incidence of RSV-related hospitalization by approximately half. The safety and ef-ficacy of palivizumab in the treatment of RSV disease have not been established.
Serious adverse reactions caused by palivizumab are rare. Mild erythema and pain may occur at the injection site. Although no anaphylactoid reactions have been re-ported to date, the possibility of this reaction exists be-cause palivizumab is a protein.