Orally Active CCR5 Antagonists as Anti-HIV-1 Agents 2: Synthesis and Biological Activities of Anilide Derivatives Containing a Pyridine N-Oxide Moiety

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In order to develop orally active CCR5 antagonists, we investigated 1-benzoxepine derivatives containing new polar substituents, such as phosphonate, phosphine oxide or pyridine N-oxide moieties, as replacements for the previoiusly reported quaternary ammonium moiety. Among these compounds, the 2-(α-hydroxybenzyl)pyridine N-oxide 5e exhibited moderate CCR5 antagonistic activity and had an acceptable pharmacokinetic profile in rats. Subsequent chemical modification was performed and compound (S)-5f possessing the (S)-configuration hydroxy group was found to be more active than the (R)-isomer. Replacement of the 1-benzoxepine ring with a 4-methylphenyl group by a 1-benzazepine ring with a 4-[2-(butoxy)ethoxy]phenyl group enhanced the activity in the binding assay. In addition, introduction of a 3-trifluoromethyl group on the phenyl group of the anilide moiety led to greatly increased activity in the HIV-1 envelope-mediated membrane fusion assay. In particular, compound (S)-5s showed the most potent CCR5 antagonistic activity (IC₅₀=7.2 nM) and inhibitory effect (IC₅₀=5.4 nM) in the fusion assay, together with good pharmacokinetic properties in rats.