Whole-body biodistribution and radiation dosimetry of ¹⁸F-FP-(+) -DTBZ (¹⁸F-AV-133): A novel vesicular monoamine transporter 2 imaging agent

Vesicular monoamine transporter 2 (VMAT2) is highly expressed in the endocrine cells and brain. We investigated the biodistribution and radiation dosimetry of (2R,3R,11bR)-9-(3-¹⁸F-fluoropropoxy)-3-isobutyl-10- methoxy-2,3,4,6,7, 11b-hexahydro-1H-pyrido[2,1-a]isoquinolin-2-ol ( ¹⁸F-FP-(+)-dihydrotetrabenazine [DTBZ] or ¹⁸F-AV-133), a potential VMAT2 imaging agent showing encouraging results in humans, to facilitate its future clinical use. Methods: Nine healthy human subjects (mean age ± SD, 58.6 ± 4.2 y) were enrolled for the whole-body PET scan. Serial images were acquired for 3 h immediately after a bolus injection of 390.7 ± 22.9 MBq of ¹⁸F-AV-133 per individual. The source organs were delineated on PET/CT images. The OLINDA/EXM application was used to determine the equivalent dose for individual organs. Results: The radiotracer did not show any noticeable adverse effects for the 9 subjects examined. The radioactivity uptake in the brain was the highest at 7.5% ± 0.6% injected dose at 10 min after injection. High absorbed doses were found in the pancreas, liver, and upper large intestine wall. The highest-dosed organ, which received 153.3 ± 23.8 μGy/MBq, was the pancreas. The effective dose equivalent and effective dose for ¹⁸F-AV-133 were 36.5 ± 2.8 and 27.8 ± 2.5 μSv/MBq, respectively. These values are comparable to those reported for any other ¹⁸F-labeled radiopharmaceutical. Conclusion: ¹⁸F-AV-133 is safe, with appropriate biodistribution and radiation dosimetry for imaging VMAT2 sites in humans. COPYRIGHT