Off-target screening of amyloid-beta plaque targeting [F-18]florapronol ([F-18]FC119S) in postmortem Alzheimer's disease tissues

We investigated the off-target binding of amyloid-beta (A beta) target [F-18]florapronol ([F-18]FC119S) using postmortem Alzheimer's disease (AD) brain tissue, compared with a known A beta target imaging agent, [I-125]TZDM and tau targeting [I-125]MK as positive and negative controls, respectively. Off-target binding of monoamine oxidase-A and -B (MAO-A and -B) was screened for FC119S and Pittsburgh compound B (PiB). Autoradiography (ARG) was performed to screen the A beta-binding potential using human AD postmortem brain tissue sections. Colocalization was quantitatively analyzed by using image analysis software. Pathological analysis was performed for screening of specific binding of amyloid-beta and phospho-tau. Amyloid-beta targeting [F-18]FC119S and [I-125]TZDM tracers were showed a similar binding pattern in ARG, but [I-125]MK was showed a different binding patterns. In the blocking experiment, [F-18]FC119S binding was effectively blocked by a cold TZDM compound. FC119S and PiB were not showed specific binding with MAO-A and MAO-B. The autoradiographic binding pattern was positively correlated with the A beta expression.