Bacteriophage-derived dsRNA exerts anti-SARS-CoV-2 activity in vitro and in Golden Syrian hamsters in vivo

Purpose: Bacteriophage-derived dsRNA, also known as Larifan, is nationally well-known broad-spectrum antiviral medication. The goal of this study was to ascertain the antiviral activity of Larifan against the novel SARS-CoV-2. Methods: The antiviral activity of Larifan against SARS-CoV-2 in vitro was measured in human lung adenocarcinoma (Calu3) and primary human small airway epithelial cells (HSAEC) using cytopathic effect assay, viral RNA copy number detection by digital droplet PCR (ddPCR) and infectious virus titration in cells supernatants in Vero E6 cells by end-point titration method. The antiviral effect of Larifan in vivo was detected in SARS-CoV-2 infection model in Golden Syrian hamsters. Larifan (5 mg/kg) was administered either subcutaneously or intranasally twice before and after virus infection with a 24-hour interval between doses. The viral RNA copies and infectious virus titre were detected in animal lungs at day three and five post-infection using ddPCR and end-point titration in Vero E6 cells, respectively. Histopathology of lungs was analysed as well. Results: Larifan inhibited SARS-CoV-2 replication in Calu3 cells both after the drug addition pre- and pot-infection with a substantial drop in the supernatant viral RNA copy numbers from eight (p = 0.0013) to twenty (p = 0.0042) times, respectively. Similarly, infectious virus titre in Vero E6 cells dropped by 3.6log10 and 2.8log10 after the drug addition pre- and pot-infection, respectively. In HSAEC, Larifan inhibited SARS-CoV-2 replication at the similar level. Larifan also markedly reduced virus numbers in the lungs of infected hamsters (p = 0.0032) both at day three and five post-infection with a more pronounced effect after intranasal administration reaching a drop by 2.7log10 at day three and 2.0log10 at day five. The administration of Larifan also reduced the amount of infections virus titer in lungs (p = 0.0039) by 4.3log10 and 2.8log10 at day three and five post-infection, respectively. Improvements in the infection-induced pathological lesion severity in the lungs of animals treated with Larifan were also demonstrated by histological analyses. Conclusions: The inhibition of SARS-CoV-2 replication in vitro and the reduction of the viral load in the lungs of infected hamsters treated with Larifan alongside the improved lung histopathology, suggests a potential use of Larifan in controlling the COVID-19 disease in humans. ### Competing Interest Statement The authors have declared no competing interest.