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 metabolism is a crucial strategy for Parkinson’s disease 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 levodopa 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. • A fluorescence-based visualization inhibitor screening method was developed to assess the inhibition activity on COMT both in vitro and in living cells. • Compared to the lead compound baicalein, BA24 demonstrated a 26-fold increase in cellular COMT inhibition and approximately 10-fold improvements in metabolic stability, membrane permeability and oral bioavailability, respectively. • BA24 competitively inhibited COMT by binding to the catechol pocket, with a K ᵢ of 89.28 nM and an IC 50 of 72.6 nM. • BA24 exhibited favorable safety profiles and significantly modulated levodopa metabolism in rats.