Influenza A virus (IAV) is a major cause of respiratory infections worldwide. Current preventive measures, though effective for decades, face limitations due to the continuous evolution of viral strains and challenges in targeting specific viral proteins. In this study, we conducted in vivo screenings to evaluate the antiviral properties of various promising polymers to overcome the limitations of current virus infection prevention strategies. Subsequently, we performed detailed physiological and pathological assessments over an extended infection period. In the animal experiments regarding weight loss, a key symptom of viral infection, the group treated with xanthan gum (XG) showed significant suppression of weight loss compared to the untreated group starting from 3 DPI. Throughout the experiment, the treated group maintained a body weight similar to that of the uninfected group. In the virus titration and lung tissue pathology analysis, the group treated with the test substance showed a significantly lower viral load and tissue pathology results closer to normal compared to the untreated group. Additionally, we conducted in vitro combination treatment experiments to evaluate the antiviral ability of XG in conjunction with camostat, a previously known TMPRSS2 inhibitor. The results demonstrated that in the combination-treated groups, XG and camostat exhibited significantly higher cell viability at lower concentrations compared to the single-treatment groups for influenza A H1N1, A H3N2, and B type. These results indicate that XG possesses potential capabilities in inhibiting respiratory viruses and may be utilized in conjunction with existing antiviral treatments.

In recent years, numerous researchers have investigated various preventive strategies against respiratory viruses that pose a threat to human health. This study aims to develop a nasal spray formulation based on the natural polysaccharide xanthan gum (XG) and camostat, and to evaluate its dual protective mechanism at the nasal mucosa, the primary entry point for respiratory viral infections. The efficacy of the formulation was assessed through physicochemical characterization, cell-based assays, and animal experiments. Initially, muco-adhesiveness was evaluated by monitoring the drying dispersion area of the test formulation over time on a Petri dish. The combination of XG and camostat exhibited a dispersion area more than ten times larger than that of each component used alone. The antiviral efficacy was demonstrated in both human nasal epithelial cells (HNEc) and an influenza-infected mouse model. The cell-based experiment demonstrated a significant inhibition of viral penetration and replication. Furthermore, suppression of transmembrane protease, serine 2 (TMPRSS2) expression, a key factor in influenza virus entry, was observed in mouse lung tissues. These findings suggest that the Camostat–Polysaccharide Dual-Action Nasal Spray (CPNS), currently under development, holds promise as a non-invasive, first-line barrier to prevent the initial infection and replication of respiratory viruses.

Extensive efforts have been undertaken by numerous researchers to control respiratory viruses across the domains of diagnosis, prevention, and treatment. In this study, we developed a niclosamide–polysaccharide nasal spray (NPNS) formulation based on xanthan gum (XG), a naturally derived polysaccharide, and niclosamide, a conventional anthelmintic agent. We then evaluated its therapeutic efficacy following intranasal administration under influenza virus-infected conditions. NPNS was assessed for cytotoxicity under Good Laboratory Practice (GLP) conditions in accordance with ISO 10993-5, and no cytotoxic effects were observed. In influenza virus-infected human nasal epithelial cells (HNEc), NPNS treatment resulted in at least 92.5% suppression of viral gene expression. Furthermore, NPNS demonstrated significantly greater antiviral activity compared to Placebo 1 and Placebo 2, which were formulated by excluding niclosamide and XG, respectively. Owing to the physicochemical properties conferred by XG, NPNS exhibited prolonged retention on the nasal mucosa in a mouse model. Consistently, NPNS showed potent antiviral efficacy in influenza-infected mice. In addition, NPNS treatment was associated with the downregulation of S-phase kinase-associated protein 2 (SKP2), a host factor known to facilitate intracellular viral replication. Collectively, these findings suggest that NPNS may serve as a first-line protective barrier during the early stage of influenza infection by simultaneously blocking viral entry and suppressing viral replication through its dual physicochemical and molecular mechanisms.