Peramivir conjugates as orally available agents against influenza H275Y mutant.

Peramivir is an efficacious neuraminidase (NA) inhibitor for treatment of influenza by intravenous administration. However, the efficacy of peramivir toward the H275Y mutant is appreciably reduced. To address this drawback, conjugation of peramivir with caffeic acid is devised in this study to enhance the binding affinity with neuraminidases. The C2-OH group of peramivir is elaborated to link with caffeate derivatives, giving the desired conjugates 8 and 9 that possess potent NA inhibitory activity against both wild-type and H275Y viruses with the IC values in nanomolar range. The molecular modeling reveals that the caffeate moiety of conjugate 9 prefers to reside in the 295-cavity of H275Y neuraminidase, thus providing additional hydrogen bonds and hydrophobic interactions to compensate the reduced binding affinity of the peramivir moiety due to Glu-276 dislocation in H275Y mutant. In comparison with peramivir, the lipophilicity of conjugates 8 and 9 also increases by incorporation of the caffeate moiety. Thus, conjugates 8 and 9 offer better effect to protect MDCK cells from infection of H275Y virus with low EC value (∼17 nM). Administration of conjugates 8 or 9 by oral gavage is effective in treatment of mice that are infected by lethal dose of wild-type or H275Y influenza viruses. Considering drug metabolism, since the ester linkage in conjugate 8 is susceptible to hydrolysis in plasma, conjugate 9 with robust amide linkage may be a better candidate for development into orally available anti-influenza drug that is also active to mutant viruses.