US-based biopharmaceutical firm Gilead Sciences has reported results from a placebo-controlled, Phase IIa challenge trial of its investigational oral RSV fusion inhibitor 'GS-5806' in healthy adult patients intranasally infected with respiratory syncytial virus (RSV).
The trial achieved its primary and secondary endpoints of lower viral load, improvements in total mucus weight and also symptom diary score compared to placebo.
RSV is a pathogen that infects the human respiratory tract, leading to bronchiolitis and pneumonia.
The double-blind, placebo-controlled challenge trial was designed to evaluate the effect of GS-5806 on AUC RSV viral load (primary endpoint), as well as on mucus weight and total symptom score (secondary endpoints).
A total of 140 healthy adults aged 18-45 were admitted into a clinical research quarantine unit where they received a clinical strain of RSV intranasally and were then monitored for 12 days.
In the trial, patients in the first four groups were randomised 1:1 to receive GS-5806 (50mg on day one and 25mg on days two to five) or matching placebo for five days.
University of Tennessee School of Medicine professor of pediatrics John DeVincenzo said no effective antiviral treatment currently exists for RSV infection, which is a major cause of serious respiratory infections.
"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," DeVincenzo said.
Primary efficacy analysis focused on the pre-specified quarantine phase of the trial (Cohorts 1-4) of healthy volunteers with demonstrated RSV infection before treatment.
From 54 patients in Cohorts 1-4, GS-5806 treatment resulted in a 99.9% reduction in the viral load, according to the company.
The results showed that mean total mucus weight after treatment and mean change from baseline total symptom diary score also were significantly lower for GS-5806-treated patients.
The company said that mean total mucus weight during the five days after the first dose was 6.9g for GS-5806 compared to 15.1g for placebo-treated patients, a treatment difference of 8.2g.
Image: This electron micrograph depicts the Respiratory Syncytial Virus (RSV) pathogen. Photo: courtesy of Kauczuk.