Cyclopentane neuraminidase inhibitors with potent in vitro anti-influenza virus activities

A novel series of cyclopentane derivatives have been found to exhibit potent and selective inhibitory effects on influenza virus neuraminidase, These compounds, designated RWJ-270201, BCX-1827, BCX-1898, and BCX-1923, were tested in parallel with zanamivir and oseltamivir carboxylate against a spectrum of influenza A (H1N1, H3N2, and H5N1) and influenza B viruses in MDCK cells, inhibition of viral cytopathic effect ascertained visually and by neutral red dye uptake was used, with 50% effective (virus-inhibitory) concentrations (EC50) determined. Against the H1N1 viruses A/Bayern/07/95, A/Beijing/262/95, A/PR/8/34, and A/Texas/36/91, EC(50)s (determined by neutral red assay) of the novel compounds were less than or equal to 1.5 muM. Twelve strains of H3N2 and two strains of avian H5N1 viruses were inhibited at < 0.3 <mu>M Influenza B/Beijing/184/93 and B/Harbin/07/94 viruses were inhibited at < 0.2 <mu>M, with three other B virus strains inhibited at 0.8 to 8 muM, The novel inhibitors were comparable in potency to (or slightly more potent than) zanamivir and oseltamivir carboxylate. No cytotoxicity was seen with the compounds at concentrations of less than or equal to 1 mM in cell proliferation assays. The antiviral activity of RWJ-270201, chosen for clinical development, was studied in greater detail. Its potency and that of oseltamivir carboxylate decreased with increasing multiplicity of virus infection. Time-of-addition studies indicated that treatment with either compound needed to begin 0 to 12 h after virus exposure for optimal activity. Exposure of cells to RWJ-270201 caused most of the virus to remain cell associated, with extracellular virus decreasing in a concentration-dependent manner. This is consistent with its effect as a neuraminidase inhibitor. RWJ-270201 shows promise in the treatment of human influenza virus infections.