MAO-B Inhibitors Do Not Block In Vivo Flortaucipir([18F]-AV-1451) Binding

Recent evidence suggests that the tau radiotracer [F-18]THK-5351 displays high affinity for the monoamine oxidase type B (MAO-B) enzyme. Utilizing another tau-tracer, flortaucipir ([F-18]AV-1451), we previously reported that non-demented Parkinson's disease patients show off-target binding in subcortical structures, but no appreciable cortical uptake. However, 59 % of these patients were receiving MAO-B inhibitors at the time of their scan. Here, we retrospectively investigated if MAO-B inhibitors in clinical doses affect flortaucipir binding. We compared the standard uptake values of flortaucipir at regional and voxel levels in Parkinson's disease patients who received MAO-B inhibitors with those who did not. Sixteen of 27 Parkinson's disease patients received MAO-B inhibitors at the time of scan. We found no significant flortaucipir uptake differences between the groups at voxel or regional levels. Use of MAO-B inhibitors at pharmaceutical levels did not significantly affect flortaucipir binding. Thus, MAO-B does not appear to be a significant binding target of flortaucipir.