Astodrimer sodium, dendrimer antiviral, inhibits replication of SARS-CoV-2 in vitro

Abstract

An effective response to the ongoing coronavirus disease (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) will require a range of complementary preventive modalities. The current studies were conducted to evaluate the in vitro SARS-CoV-2 antiviral activity of astodrimer sodium, a dendrimer with broad spectrum antimicrobial activity, including against enveloped viruses in in vitro and in vivo models, that is marketed for antiviral and antibacterial applications. We report that astodrimer sodium inhibits replication of SARS-CoV-2 in Vero E6 cells when added to cells 1-hour prior to or 1-hour post infection, with 50% effective concentrations reducing virus-induced cytopathic effect (EC ₅₀) ranging from 0.090 to 0.742 μM (0.002 to 0.012 mg/mL). The selectivity index (SI) in these assays was as high as 2197. Astodrimer sodium was also effective in a virucidal evaluation when mixed with virus for 1 hour prior to infection of cells (EC ₅₀ 1.83 μM [0.030 mg/mL]). Results from a time of addition study, which showed infectious virus was below the lower limit of detection at all time points tested, were consistent with the compound inhibiting early virus entry steps. The data were similar for all investigations and were consistent with the potent antiviral activity of astodrimer sodium being due to inhibition of virus-host cell interactions, as previously demonstrated for other viruses. Further studies will confirm if astodrimer sodium binds to SARS-CoV-2 spike protein and physically blocks initial association of the virus with heparan sulfate proteoglycans on the host cell. Given the in vitro effectiveness and significantly high SI, astodrimer sodium warrants further investigation for potential as a nasally administered or inhaled antiviral agent for SARS-CoV-2 prevention and treatment applications.