Synthesis and Evaluation of Bicyclic Hydroxypyridones as Inhibitors of Catechol O-Methyltransferase

A series of bicyclic pyridones were identified as potent inhibitors of catechol O-methyltransferase (COMT). Substituted benzyl groups attached to the basic nitrogen of the core scaffold gave the most potent inhibitors within this series. Rat pharmacokinetic studies showed medium to high levels of clearance for this series, but with high free fraction due to remarkably low levels of protein and tissue binding. In rat biomarker studies, levels of unbound drug exposure are seen in the brain, which exceed their respective IC₅₀s, leading to changes in the levels of dopamine metabolites in a manner consistent with COMT inhibition.