Structure-Based Design and Synthesis of C-1- and C-4-Modified Analogs of Zanamivir as Neuraminidase Inhibitors

In order to exploit the 430-cavity in the active sites of neuraminidases, 22 zanamivir analogs with C-1 and C-4 modification were synthesized, and their inhibitory activities against both group-1 (H5N1, H1N1) and group-2 neuraminidases (H3N2) were determined. Compound 9f exerts the most potency, with IC50 value of 0.013, 0.001, and 0.09 mu M against H3N2, H5N1, and H1N1, which is similar to that of zanamivir (H3N2 IC50 = 0.0014 mu M, H5N1 IC50 = 0.012 mu M, H1N1 IC50 = 0.001 mu M). Pharmacokinetic studies of compound 9f in rats showed a much longer plasma half-life (t(1/2)) than that of zanamivir following administration (po dose). Molecular modeling provided information about the binding model between the new inhibitors and neuraminidase, with the elongated groups at the C-1-position being projected toward the 430-loop region. This study may represent a novel starting point for the future development of improved antiflu agents.