Hydromethylthionine dihydrobromide (Leukomethylene blue dihydrobromide) is a potent inhibitor of TAU protein aggregation. Hydromethylthionine dihydrobromide reduces neurodegeneration by interacting with TAU proteins and preventing them from forming neurotoxic aggregates. Hydromethylthionine dihydrobromide can be used in the study of Alzheimer's disease and other TAU related disorders.