Repurposed catechol‐O‐methyltransferase inhibitors tolcapone and entacapone preferentially suppress aggregation and seeding of P301 mutant tau in human neuronal models

Background and purpose Pathogenic aggregation and propagation of seed‐competent TAU assemblies drive tauopathies. MAPT P301 mutations accelerate aggregation and enhance seed competence, yet pharmacological strategies selectively targeting these pathogenic species remain limited. We investigated whether the clinically approved catechol‐O‐methyltransferase inhibitors tolcapone (TOL) and entacapone (ENT) preferentially modulate mutant TAU aggregation and seeding. Experimental Approach TOL and ENT effects on TAU aggregation were evaluated via cell‐free assays, surface plasmon resonance (SPR), and in silico docking. Functional consequences of compound‐modified fibrils were assessed in mutant TAU‐expressing SH‐SY5Y cells. Translational relevance was examined in human induced pluripotent stem cell (hiPSC)‐derived neurons exposed to pathogenic K18 fibrils, followed by post‐seeding compound treatment. Key Results Both compounds dose‐dependently inhibited TAU aggregation, exhibiting greater potency, stronger SPR binding affinities, and more favourable computed interaction energies for P301S mutant versus wild‐type TAU. Fibrils formed with TOL or ENT induced less downstream TAU oligomerization and phosphorylation in SH‐SY5Y cells, with TOL showing superior protection. In hiPSC‐derived neurons, post‐seeding treatment with either compound decreased fibril‐induced, sarkosyl‐insoluble, TAU aggregation and phosphorylation without overt cytotoxicity. Conclusion and Implications TOL and ENT preferentially reduced the aggregation and seeding of pathogenic P301 mutant TAU in the experimental models examined. These findings provide proof‐of‐concept support for mutation‐focused pharmacological approaches and identify catechol scaffolds as starting points for developing more potent and safer TAU‐directed compounds. Further studies are required to define the relevant molecular interactions, confirm the neuronal findings across additional hiPSC lines and determine whether effective CNS exposure can be achieved in vivo.