S-337395 Achieves Primary Endpoint

This trial was a randomized, placebo-controlled, double-blind human challenge study conducted in healthy adults who were actively inoculated with RSV. The antiviral efficacy and safety of S 337395 were evaluated when administered orally once daily for five days. The S 337395 treatment group showed a statistically significant reduction in viral load compared to the placebo group, achieving the primary endpoint. In the highest dose group of S 337395, there was an 88.94% reduction in viral load (P<0.0001), and also a statistically significant improvement in clinical symptom scores. Additionally, S 337395 was generally safe and well tolerated, there were no serious or severe adverse events, and no dose-dependent increase in incidence or severity of adverse events. No participants discontinued due to adverse events.

S337395 is an investigational oral antiviral candidate for RSV infection that inhibits the activity of the L protein, which is essential for virus replication.

Shionogi is committed to the principle “Protecting people worldwide from the threat of infectious diseases” as our key focus, and is working on the realization of total care for infectious diseases. In response to acute respiratory infections driving epidemics (such as influenza and COVID-19, RSV), we are working to build a new business model with an expanded portfolio of treatments achieving stable revenue.

About the Phase II Human Challenge Trial; A human challenge trial is a clinical study in which healthy subjects are intentionally infected with a pathogen, such as a virus, to investigate the onset of disease and the progression of symptoms, including the viral load, after administration of a treatment or placebo. This trial was a randomized, placebo-controlled, double-blind human challenge study conducted to verify the efficacy and safety of S 337395. It involved 114 healthy adults who were actively inoculated with RSV. Participants were administered S -337395 or placebo for five days. The primary endpoint was the area under the curve (AUC) of the viral load over time.

About S 337395; S 337395 is a novel investigational oral treatment for RSV infection discovered through joint research with UBE. It is a low-molecular-weight compound with a novel mechanism that inhibits the RNA-dependent RNA polymerase activity of the L protein possessed by the RSV , thereby inhibiting the transcription and replication of the viral genome. Unlike F protein inhibitors, which exert their effect by preventing new viral infection of cells extracellularly, S  37395 works by preventing viral proliferation within infected cells, thus potentially offering higher efficacy and a more rapid reduction in viral load.