Objective: In a longitudinal case series of patients with progressive supranuclear palsy (PSP), a chronic challenge with the irreversible MAO-B inhibitor selegiline was used to probe the contribution of brain MAO-B availability to the uptake of ¹⁸F-Florzolotau – a second-generation tau PET tracer.

Background: Irreversible inhibition of monoamine oxidase B (MAO-B; EC 1.4.3.4) with selegiline is commonly utilized to enhance dopaminergic neurotransmission in patients with Parkinson’s disease (PD) and other PD-related disorders – including progressive supranuclear palsy (PSP). Unfortunately, MAO-B can also represent an off-target binding site for certain first-generation tau positron emission tomography (PET) tracers. While this limitation has put into question the reliability of signal interpretation and might be detrimental to the application of tau PET imaging for clinical and research use, the ability of MAO-B to act as an off-target binding site is tracer-dependent.

Method: Three patients with PSP had baseline and post-selegiline (time interval: 2 months) ¹⁸F-Florzolotau PET scans. The changes in ¹⁸F-Florzolotau standardized uptake value ratios (SUVRs) served as the main outcome measure.

Results: The patterns of ¹⁸F-Florzolotau uptake in areas typically affected by tau pathology among patients with PSP were unaffected by chronic MAO-B inhibition. Additionally, baseline and post-selegiline SUVRs did not change significantly.

Conclusion: The interpretation of ¹⁸F-Florzolotau PET images, with respect to tau pathology, is not confounded by MAO-B availability.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-monoamine-oxidase-b-inhibitor-selegiline-does-not-affect-18f-florzolotau-uptake-in-patients-with-progressive-supranuclear-palsy-a-longitudinal-case-series/