Discovery and optimization of a novel non-nitrocatechol COMT inhibitor for modulating levodopa metabolism

Human catechol-O-methyltransferase (COMT) is a key target for neuropsychiatric disorders. Inhibiting COMT to prevent levodopa (L-DOPA) metabolism is a crucial strategy for Parkinson's disease (PD) treatment. While clinically used COMT inhibitors are primarily nitrocatechol-based, they often cause adverse effects, prompting efforts to develop safer non-nitrocatechol alternatives. In this study, baicalein (BA) was identified as a potent lead compound for COMT inhibition after screening a series of natural flavonoids using a fluorescence-based visualization inhibitor screening method. Subsequent multi-dimensional structural optimizations addressed the druggable deficiencies of BA, resulting in compound BA24, which demonstrated a 26-fold increase in cellular COMT inhibition and approximately 10-fold improvements in metabolic stability, membrane permeability and oral bioavailability, respectively, compared to BA. Mechanistically, BA24 competitively inhibited COMT by binding to the catechol pocket with a K _i of 89.28 nM. Furthermore, BA24 exhibited favorable safety profiles and significantly modulated L-DOPA metabolism in rats. Additionally, the relationships between the structural properties, inhibitory activity and metabolic stability of flavonoids as COMT inhibitors were comprehensively investigated. Collectively, this work not only presents a novel non-nitrocatechol COMT inhibitor with favorable safety profiles and potent anti-COMT effects both in vitro and in vivo, but also provides valuable insights into optimizing the druggability of flavonoids as lead compounds.