Abstract
BACKGROUND: The cannabinoid type 2 receptors (CB2R) represent a target of increasing importance in neuroimaging due to its upregulation under various neuropathological conditions. Previous evaluation of [(18)F]JHU94620 for the non-invasive assessment of the CB2R availability by positron emission tomography (PET) revealed favourable binding properties and brain uptake, however rapid metabolism, and generation of brain-penetrating radiometabolites have been its main limitations. To reduce the bias of CB2R quantification by blood-brain barrier (BBB)-penetrating radiometabolites, we aimed to improve the metabolic stability by developing -d(4) and -d(8) deuterated isotopologues of [(18)F]JHU94620. RESULTS: The deuterated [(18)F]JHU94620 isotopologues showed improved metabolic stability avoiding the accumulation of BBB-penetrating radiometabolites in the brain over time. CB2R-specific binding with K(D) values in the low nanomolar range was determined across species. Dynamic PET studies revealed a CB2R-specific and reversible uptake of [(18)F]JHU94620-d(8) in the spleen and to a local hCB2R(D80N) protein overexpression in the striatal region in rats. CONCLUSION: These results support further investigations of [(18)F]JHU94620-d(8) in pathological models and tissues with a CB2R overexpression as a prerequisite for clinical translation.