UPDATE: Gilead Reports Investigational GS-5806 Reduces Viral Load, Clinical Syptoms in Phase 2 RSV Study, Says Study Reached Primary, Secondary Endpoints

Gilead Sciences, Inc. GILD today announced results from a placebo-controlled, Phase 2a challenge study in healthy adult patients intranasally infected with respiratory syncytial virus (RSV). The study of GS-5806, an investigational oral RSV fusion inhibitor, achieved its primary and secondary endpoints of lower viral load (the amount of virus detected in the nasal wash), improvements in total mucus weight (the amount of mucus produced by the nose) and also symptom diary score compared to placebo. Detailed results from this study (Poster #1008) will be presented today during a poster discussion session at the American Thoracic Society 2014 International Conference in San Diego. RSV is a pathogen that infects the human respiratory tract, potentially leading to bronchiolitis and pneumonia. While most otherwise healthy people recover from the virus, there is an increased risk of severe disease and death in premature infants, individuals with certain pulmonary diseases, the elderly and those who are immune suppressed. Globally, the clinical burden of RSV infection is comparable to that of influenza. “No effective antiviral treatment currently exists for RSV infection, which is a major cause of serious respiratory infections,” said John DeVincenzo, MD, Professor of Pediatrics and Professor of Microbiology, Immunology, and Biochemistry, University of Tennessee School of Medicine and Medical Director of the Molecular and Viral Diagnostics Laboratories at Le Bonheur Children's Hospital. “Based on the reductions in RSV viral load and clinical symptoms, as well as the safety profile observed in this adult challenge study, clinical trials in naturally infected patients should now be explored.” The primary efficacy analysis focused on the pre-specified quarantine phase of the study (Cohorts 1-4) of healthy volunteers with demonstrated RSV infection before treatment. Among 54 patients in Cohorts 1-4 (GS-5806: n=27; placebo: n=27), GS-5806 treatment resulted in a 99.9 percent reduction in the viral load (expressed as log transformed viral load area under the curve of 250.7 log10 plaque forming unit equivalents (PFUe*) hour/mL versus 757.7 log10 PFUe*hour/mL; p<0.001). Mean total mucus weight after treatment and mean change from baseline total symptom diary score (daily reporting of symptoms such as stuffy nose, cough and sore throat) also were significantly lower for GS-5806-treated patients. Mean total mucus weight during the five days after the first dose was 6.9 g for GS-5806 compared to 15.1 g for placebo-treated patients, a treatment difference of 8.2 g (p=0.028). Adjusted mean AUC of change in symptom diary score from after first dose through Day 12 was -20.2 for patients treated with GS-5806 compared to 204.9 score*hour for placebo-treated patients, a difference of 225.1 score*hour (p=0.005). There were no serious adverse events in the study. All adverse events were mild or moderate in severity, with the exception of one patient who received placebo. Grade 1 pulmonary function decrease was the only treatment-emergent adverse event experienced by two or more patients in either treatment group.