title: Synthesis and evaluation of 2-[18F]fluoro-CP-118,954 for the in vivo mapping of acetylcholinesterase.
abstract: 5,7-Dihydro-3-[2-[1-(2-fluorobenzyl)-4-piperidinyl]ethyl]-6H-pyrrolo[3,2,f]-1,2-benzisoxazol-6-one (2-flouro-CP-118,954; 1), a potent acetylcholinesterase (AChE) inhibitor, was prepared as a radioligand by reductive alkylation of CP-144,885 the debenzylated form of CP 118,954, with 2-[18F]fluorobenzaldehyde. The decay-corrected radiochemical yield was 25-30% and the effective specific activity was 41-53 GBq/micromol. Tissue distribution studies of 2-[18F]fluoro-CP-118,954 ([18F]1) in mice showed that the regional brain distribution correlated well with the known density of AChE in the mouse brain. A high level of uptake in the striatum was also shown at all time points in the olfactory tubercle, which is known to have dopaminergic neurons. Blocking studies showed that radioligand uptake in all brain regions was not altered by either the dopamine receptor antagonists or the sigma receptor agonist. On the other hand, radioligand uptake in both the striatum and the olfactory tubercle was significantly blocked (80%) by ligand 1. The low level of bone uptake over time suggested that [18F]1 underwent little in vivo metabolic defluorination. The lack of metabolite formation in the mouse brain indicated that the regional distribution was attributed to [18F]1. These results demonstrated that [18F]1 binds specifically and selectively to AChE in mice and appears to be a suitable radioligand for the in vivo mapping of AChE.
authors.affiliation: Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 135-710 Seoul, Republic of Korea.
authors.forename: Eun Kyoung
authors.initials: EK
authors.lastname: Ryu
authors.forename: Yearn Seong
authors.initials: YS
authors.lastname: Choe
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Park
authors.forename: Jin-Young
authors.initials: JY
authors.lastname: Paik
authors.forename: Yu Ri
authors.initials: YR
authors.lastname: Kim
authors.forename: Kyung-Han
authors.initials: KH
authors.lastname: Lee
authors.forename: Yong
authors.initials: Y
authors.lastname: Choi
authors.forename: Sang Eun
authors.initials: SE
authors.lastname: Kim
authors.forename: Byung-Tae
authors.initials: BT
authors.lastname: Kim
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005462:Fluorine Radioisotopes / Q000737:chemistry / Q000493:pharmacokinetics*; D007555:Isoxazoles / Q000493:pharmacokinetics*; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D008813:Mice, Inbred ICR; D009928:Organ Specificity; D010880:Piperidines / Q000493:pharmacokinetics*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics; D014018:Tissue Distribution
chemical_list: C095054:5,7-dihydro-3-(2-(1-(phenylmethyl)-4-piperidinyl)ethyl)-6H-pyrrolo(3,2-f)-1,2-benzisoxazol-6-one; D005462:Fluorine Radioisotopes; D007555:Isoxazoles; D010880:Piperidines; D019275:Radiopharmaceuticals; D000110:Acetylcholinesterase