Whole-Body Biodistribution and Radiation Dosimetry of the Cannabinoid Type 2 Receptor Ligand [11C]-NE40 in Healthy Subjects

The type 2 cannabinoid receptor (CB2R) is part of the human endocannabinoid system and is involved in central and peripheral inflammatory processes. In vivo imaging of the CB2R would allow study of several (neuro)inflammatory disorders. In this study we have investigated the safety and tolerability of [C-11]-NE40, a CB2R positron emission tomography (PET) ligand, in healthy human male subjects and determined its biodistribution and radiation dosimetry. Six healthy male subjects (age 20-65 years) underwent a dynamic series of nine whole-body PET/CT scans for up to 140 min, after injection of an average bolus of 286 MBq of [C-11]-NE40. Organ absorbed and total effective doses were calculated through OLINDA. [C-11]-NE40 showed high initial uptake in the spleen and a predominant hepatobiliary excretion. In the brain, rapid uptake and swift washout were seen. Organ absorbed doses were largest for the small intestine and liver, with 15.6 and 11.5 mu Gy/MBq, respectively. The mean effective dose was 3.64 +/- 0.81 mu Sv/MBq. There were no changes with aging observed. No adverse events were encountered. This first-in-man study of [C-11]-NE40 showed an expected biodistribution compatible with lymphoid tissue uptake and appropriate fast brain kinetics in the healthy human brain, underscoring the potential of this tracer for further application in central and peripheral inflammation imaging. The effective dose is within the typical expected range for C-11 ligands.