Palivizumab efficacy shown in registry data

January 2003

BOSTON — Data presented from the Palivizumab Outcomes Registry reaffirmed that prophylaxis with palivizumab (Synagis, MedImmune) reduces the rate of respiratory syncytial virus (RSV)-related hospitalization among high-risk infants.

Mark Hudak, MD, of the University of Florida, presented the latest data in a poster at the AAP’s National Conference and Exhibition held here.

More than 5,000 infants, most of whom were younger than 35 weeks in gestational age, were enrolled in the study. Most of the infants had some type of identified risk factor for severe RSV, and a majority weighed less than 2,500 g at birth.

Despite the risk factors for RSV, the study found that the hospitalization rate for treated patients in the registry was 1.5%, compared with 5.0% in the initial randomized studies of the drug.

Effective in heart disease patients

Another study on palivizumab, which was also presented at the meeting, focused on preventing RSV-related hospitalizations in young children with congenital heart disease (CHD).

A four-year, double-blind, placebo-controlled study assessed the safety and efficacy of the drug in children younger than 2 years of age with serious CHD. The study was conducted at 76 centers in North America and Europe starting in 1998. In the study, 1,287 children were randomized to receive five monthly intramuscular injections (15mg/kg) of either palivizumab or placebo during the RSV season.

Compared with placebo, the palivizumab group had 45% fewer hospitalizations due to RSV (P=0.003). Further, the data showed there were significantly fewer RSV-related hospital days (P=0.003) and fewer days of increased oxygen usage (P=0.014) in the treated group than in the placebo group. The proportions of patients in the placebo and palivizumab groups who experienced any adverse events “were similar” company officials said.

“The results of this study in CHD children are very exciting for the pediatric cardiology community,” Henry M. Sondheimer, MD, of the University of Colorado Health Sciences Center and The Children’s Hospital of Denver said in a statement. “Children with CHD who are hospitalized with RSV have substantially higher rates of mortality and morbidity than those children who do not have CHD. They are also a more difficult patient group to study. As such, the results of the current study will be very useful in helping pediatricians and pediatric cardiologists identify CHD patients who will benefit from prophylaxis with Synagis to prevent RSV.”

Guidelines for palivizumab use

Palivizumab is a humanized monoclonal antibody licensed by the FDA in 1998 to prevent serious lower respiratory tract disease caused by RSV in pediatric patients at high risk of RSV disease. Earlier clinical studies that initially demonstrated that the product was safe and effective included children with chronic lung disease and premature infants (i.e., 35 weeks gestational age or less).

The AAP guidelines for using palivizumab are as follows:

Infants younger than 24 months of age with chronic lung disease (CLD) who have required medical therapy within the past six months.

Neonates born at 28 weeks’ gestation or less without CLD and who are <12 months of age at the start of the RSV season.

Neonates born at >28 weeks’ and <32 weeks’ gestation without CLD who are <6 months of age at the start of RSV season.

Neonates born between 32 and 35 weeks’ gestation without CLD who are <6 months of age and who have additional risk factors, including school-aged siblings, crowding in the home, day care attendance, exposure to tobacco smoke in the home and multiple births.

While guidelines have been issued, physicians are still deciding when to use the drug, since the drug’s cost is a factor.

For more information:

• Hudak M, et al. Palivizumab prophylaxis of RSV disease – results of 5,097 children, 2001-2002 Outcomes Registry. Abstract 700. Presented at the AAP National Conference and Exhibition. Oct. 19-23, 2002. Boston.