RT Journal Article SR Electronic T1 Evaluation of the novel 18F-labeled PET tracer SMBT-1 for imaging astrogliosis in Alzheimer's disease JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 457 OP 457 VO 61 IS supplement 1 A1 Nobuyuki Okamura A1 Ryuichi Harada A1 Vincent Dore A1 Shozo Furumoto A1 Rachel Mulligan A1 Yukitsuka Kudo A1 Natasha Krishnadas A1 Kun Huang A1 Kazuhiko Yanai A1 Christopher Rowe A1 Victor Villemagne YR 2020 UL http://jnm.snmjournals.org/content/61/supplement_1/457.abstract AB 457Background: Neuroinflammatory changes, characterized by reactive astrocytes and activated microglia, contribute greatly to neurodegeneration throughout the course of Alzheimer’s diseases (AD). Reactive astrocytes overexpress monoamine oxidase-B (MAO-B) in the outer mitochondrial membrane. For imaging astrogliosis in the human brain, we developed the novel MAO-B PET tracer named 18F-SMBT-1. We aimed to investigate the binding properties of 18F-SMBT-1 in healthy elderly controls and AD patients. Methods: In vitro binding assays and autoradiography using postmortem brain tissues were performed for the assessment of binding affinity and selectivity of 18F-SMBT-1. Nine participants, 5 healthy elderly controls (3F/2M, 78.5±6.0 yrs) and 4 AD patients (3F/1M, 76.8±1.4 yrs), underwent 18F-SMBT-1 PET, amyloid PET with 18F-NAV4694, tau PET with either 18F-MK6240 or 18F-PI2620. 18F-SMBT-1 studies were expressed as SUV or as tissue ratios using the cerebellar white matter as reference region. To ascertain 18F-SMBT-1 selective binding to MAO-B, participants underwent a second 18F-SMBT-1 scan after receiving 5mg selegiline twice daily for 5 days. Results: SMBT-1 showed strong and reversible binding to MAO-B (Kd = 3.7 nM), and low binding affinity to other enzymes, receptors and misfolded proteins such as amyloid-β and tau. Greater amount of 18F-SMBT-1 binding was observed in AD brain tissues than in control brains and these bindings were completely displaced with MAO-B inhibitor lazabemide. In clinical studies, 18F-SMBT-1 yielded high contrast images at 60-90 min post injection. In AD patients, 18F-SMBT-1 retention was significantly higher in parahippocampus, fusiform and inferior temporal gyrus. More than 85% of 18F-SMBT-1 signal was blocked and no residual cortical activity was observed after the selegiline regimen, indicating high selectivity for MAO-B. Conclusions: 18F-SMBT-1 is the highly selective MAO-B tracer, which will enable the assessment of astrogliosis in the human brain. The confirmation of these preliminary findings with 18F-SMBT-1 will require examination of a much larger series, including participants with MCI and prodromal AD.