GAITHERSBURG, Md., — MedImmune, Inc. has announced that it has begun dosing adult volunteers in a Phase 1 clinical trial with its respiratory syncytial virus (RSV) vaccine candidate. The vaccine was developed using an attenuated parainfluenza virus type-3 (PIV-3), which was previously evaluated in a Phase 1 clinical trial in infants and recently modified to induce immunity to RSV. Data from preclinical studies indicate that the vaccine protects against both RSV and PIV-3.

“Our vaccine candidate is unique because it leverages MedImmune’s novel intranasal technology to target RSV, and possibly PIV-3, through a single intranasal immunization,” said Edward M. Connor, M.D., chief medical officer. “If successfully developed and approved, this vaccine may offer pediatricians an intranasal option to protect children broadly against respiratory disease caused by two important respiratory pathogens. These pathogens are responsible for significant illnesses in children and significant healthcare expenditures annually.”

The Phase 1 clinical study is designed to evaluate the vaccine’s safety, tolerability, and immunogenicity. It is a randomized, double-blind, placebo- controlled, dose-escalation study in approximately 120 healthy men and women between the ages of 18 and 40 years. MedImmune filed an investigational new drug application with the U.S. Food and Drug Administration (FDA) for the vaccine candidate in January 2005.

The combination vaccine is expected to offer ease of administration for pediatricians and their patients, and may help reduce RSV/PIV-3-associated illnesses and hospital costs in the United States. RSV and PIV-3 are viruses that cause serious respiratory disease. RSV is the most common cause of lower respiratory tract infections in infants and children worldwide, typically occurring during the fall and winter months. There are approximately 125,000 RSV-associated hospitalizations each year in the United States. Lower respiratory tract disease due to PIV-3 is responsible for as many as 50,000 hospitalizations annually in the United States with approximately half of those in infants less than one year old.

The advancement of MedImmune’s vaccine candidate into a Phase 1 clinical study underscores the company’s efforts to leverage the latest vaccine technologies with its proven experience in developing options for the prevention of respiratory infectious disease. MedImmune products have helped to protect children from RSV since 1996. Now the standard of care for the prevention of RSV in high-risk infants, Synagis&reg (pavilizumab) was the first monoclonal antibody approved by the FDA to combat an infectious disease.

To date, Synagis has helped protect more than 700,000 premature and/or high-risk infants against RSV disease. MedImmune is also the developer and manufacturer of FluMist&reg (Influenza Virus Vaccine Live, Intranasal), the first FDA- approved intranasal influenza vaccine in the United States.