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-F-18-fluoropropoxy)-3-isobutyl-10-methoxy-2,3,4,6,7,11b-hexahydro-1H-pyrido[2,1-a]isoquinolin-2-ol (F-18-FP-(+)-dihydrotetrabenazine [DTBZ] or F-18-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 6 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 F-18-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 mGy/MBq, was the pancreas. The effective dose equivalent and effective dose for F-18-AV-133 were 36.5 +/- 2.8 and 27.8 +/- 2.5 mu Sv/MBq, respectively. These values are comparable to those reported for any other F-18-labeled radiopharmaceutical. Conclusion: F-18-AV-133 is safe, with appropriate biodistribution and radiation dosimetry for imaging VMAT2 sites in humans.