First-in-human cannabinoid PET imaging aims for neuro-inflammation
A novel cannabinoid type 2 receptor (CB2R) ligand that binds to microglial and immuno cells could be a hit for neuro-inflammatory imaging, according to a study published in the August 2013 issue of Molecular Imaging and Biology.
Rawaha Ahmad, PhD, from the division of nuclear medicine at University Hospital Leuven in Leuven, Belgium, and colleagues tested the biodistribution, dosimetry and safety of C-11 NE40 and found the probe to be safe and useful for imaging central and peripheral neuro-inflammation. Not only is the CB2R involved in the inflammatory process, but it also plays a role in pain processing.
“In the present study we have evaluated the biodistribution and safety of C-11 NE40, indicating that this ligand can be used for brain imaging in healthy controls and pathological conditions. Such studies are underway,” wrote Ahmad to Molecular Imaging via email.
Researchers are not yet sure how this technique will be used, as results have been inconsistent, sometimes showing “abundant neuronal expression” and at other times revealing little neuronal concentration under normal conditions. There are correlations between the endocannibinoid system and neurodegenerative pathologies such as those involved in Alzheimer’s, Parkinson’s and Huntington’s disease. Further studies are needed to gain a greater understanding of the connections between neuronal pathology, inflammation and CB2R imaging.
“Therefore, imaging of CB2R in in vivo can give us some answers and clarify the role of CB2R in normal and pathological conditions,” noted Ahmad, et al.
For this study, six healthy male subjects were imaged nine times with C-11 NE40 whole-body PET to gauge biodistribution and dosimetry after injection of the CB2R ligand. Scan results showed a biodistribution suggestive of lymphoid tissue uptake and rapid brain uptake and washout, showing particular promise for brain imaging. High initial uptake was shown in the spleen and liver. Highest dose was found in the small intestine and the liver. A 300 MBq injection of C-11 NE40 corresponds with a 1.1 mSv radiation dose.