A phase 2a challenge study for GS-5806, an investigational oral RSV fusion inhibitor, found that the drug safely reduced the viral load and clinical illness of healthy adult volunteers who were intranasally infected with respiratory syncytial virus, according to researchers at Le Bonheur Children’s Hospital and the University of Tennessee Health Science Center.

GS-5806, manufactured by Gilead Sciences Inc, achieved primary and secondary endpoints of lower viral load, improvements in total mucus weight and symptom diary score compared to placebo, according to the study.

Volunteers in the study were given the oral drug after being infected with RSV using the experimental challenge model – based on a clinical isolate from an infant hospitalized with RSV bronchiolitis which can be safely used to infect adults, and that was developed in 2007 to test proof-of-concept antivirals.

RSV is the most common cause of lower respiratory tract infections in young children in the United States and worldwide. It hospitalizes 125,000 children in the United States each year, and was the cause for 1.5 million outpatient visits, according to the Centers for Disease Control and Prevention (CDC).

“No effective antiviral treatments currently exist for RSV, which is the leading cause of severe childhood respiratory infections, and is increasingly recognized as a major cause of serious adult respiratory infections,” said lead researcher John DeVincenzo, MD, an infectious disease specialist. “Based on the reductions in viral load, reduced clinical symptoms, as well as the safety profile observed in this adult challenge study, clinical trials in naturally infected patients should now be explored.”