Abstract
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Objectives The type 2 cannabinoid receptor (CB2R) is part of the endocannabinoid system and is expressed in tissues and organs related to the immune system. Upregulation of this receptor has been reported in (neuro)inflammatory diseases and its stimulation has anti-inflammatory properties in pharmacological and preclinical models. We have developed a new PET tracer, [11C]-NE40 to visualize and quantify CB2R in the brain and peripheral tissues. In this study we have investigated the safety and tolerability of a single intravenous dose of [11C]-NE40 in healthy human subjects, and determined the biodistribution and radiation dosimetry of [11C]-NE40 in vivo.
Methods Three healthy male subjects (average age 29.3 y) underwent a dynamic series of 9 whole-body (WB) PET/CT scans for up to 120 minutes, after injection of a bolus 252.6 MBq of [11C]-NE40. The organ absorbed dose per unit of administered radioactivity were determined by outlining significant source organs in 3D VOIs using PMOD 3.0. OLINDA was used to estimate the organ absorbed doses and effective dose. Safety was assessed by physical examinations, ECG and laboratory follow-up.
Results Organs receiving highest dose were intestine, liver, lungs, red marrow, lymph nodes, spleen and thyroid. Rapid uptake and washout of the healthy brain was seen. [11C]-NE40 shows a predominantly hepatobiliary excretion. Based on the retention data and OLINDA estimates, the effective dose of [11C]-NE40 in these subjects was 4.4 µSv/MBq, which is within the expected range for [11C]-labeled radioligands. No adverse events were encountered.
Conclusions This first in human CB2R PET scans show an expected biodistribution compatible with lymphoid tissue uptake and appropriate brain kinetics, underscoring the potential of this tracer. The ED is within the typical expected range for 11C ligands. Further imaging studies are planned in (neuro)inflammatory diseases
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