Evaluation of ¹⁸F-BCPP-EF for mitochondrial complex 1 imaging in the brain of conscious monkeys using PET

We have reported on the development of a novel PET probe, ¹⁸F-2-tert-butyl-4-chloro-5-{6-[2-(2-fluoroethoxy)-ethoxy]-pyridin-3-ylmethoxy}-2H-pyridazin-3-one (¹⁸F-BCPP-EF), for quantitative imaging of mitochondrial complex 1 (MC-1) activity in the brain of the living rat. For clinical application in humans, translational research in the monkey was conducted.

PET measurements with ¹⁸F-BCPP-EF were performed in young and old monkeys (Macaca mulatta) in a conscious state with arterial blood sampling. The binding specificity of ¹⁸F-BCPP-EF was evaluated with rotenone, a specific MC-1 inhibitor, in young animals. The binding (total distribution volume, V _T) of ¹⁸F-BCPP-EF was calculated using Logan graphical analysis, and one-tissue compartment model (1-TC) and two-tissue compartment model (2-TC) analyses using a metabolite-corrected plasma input function.

F-BCPP-EF was rapidly taken up into the brain just after intravenous injection, peaked between 10 and 20 min after injection, and was then gradually eliminated. The 2-TC analysis provided a better fit than the 1-TC analysis, and the V _T values from the 2-TC analysis correlated well with those from the Logan plot. With predosing with rotenone, ¹⁸F-BCPP-EF showed a higher uptake peak in the brain, followed by more rapid elimination thereafter than in the vehicle condition, resulting in significant reductions in 2-TC V _T values in all regions. In old animals, the kinetics of ¹⁸F-BCPP-EF were slightly slower with lower peak levels than in young animals, resulting age-related reductions in ¹⁸F-BCPP-EF binding in all brain regions.

The present study demonstrated that ¹⁸F-BCPP-EF may be a potential PET probe for quantitative imaging MC-1 activity in the living brain using PET.