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

A novel series of cyclopentane derivatives have been found to exhibit poten t and selective inhibitory effects on influenza virus neuraminidase, These compounds, designated RWJ-270201, BCX-1827, BCX-1898, and BCX-1923, were te sted in parallel with zanamivir and oseltamivir carboxylate against a spect rum of influenza A (H1N1, H3N2, and H5N1) and influenza B viruses in MDCK c ells, inhibition of viral cytopathic effect ascertained visually and by neu tral red dye uptake was used, with 50% effective (virus-inhibitory) concent rations (EC50) determined. Against the H1N1 viruses A/Bayern/07/95, A/Beiji ng/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 s trains 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 inhibite d at < 0.2 <mu>M, with three other B virus strains inhibited at 0.8 to 8 mu M, The novel inhibitors were comparable in potency to (or slightly more pot ent than) zanamivir and oseltamivir carboxylate. No cytotoxicity was seen w ith the compounds at concentrations of less than or equal to 1 mM in cell p roliferation assays. The antiviral activity of RWJ-270201, chosen for clini cal development, was studied in greater detail. Its potency and that of ose ltamivir carboxylate decreased with increasing multiplicity of virus infect ion. Time-of-addition studies indicated that treatment with either compound needed to begin 0 to 12 h after virus exposure for optimal activity. Expos ure of cells to RWJ-270201 caused most of the virus to remain cell associat ed, with extracellular virus decreasing in a concentration-dependent manner . This is consistent with its effect as a neuraminidase inhibitor. RWJ-2702 01 shows promise in the treatment of human influenza virus infections.