Synthesis, biodistribution, and primate imaging of fluorine-18 labeled 2beta-carbo-1'-fluoro-2-propoxy-3beta-(4-chlorophenyl)tr opanes. Ligands for the imaging of dopamine transporters by positron emission tomography

J Med Chem. 2000 Feb 24;43(4):639-48. doi: 10.1021/jm9902234.

Abstract

2beta-(R)-Carbo-1-fluoro-2-propoxy-3beta-(4-chlorophenyl) tro pane ((R)-FIPCT, R-6) and 2beta-(S)-carbo-1-fluoro-2-propoxy-3beta-(4-chlorophenyl) tro pane ((S)-FIPCT, S-6) were prepared and evaluated in vitro and in vivo for dopamine transporter (DAT) selectivity and specificity. High specific activity [(18)F](R)-FIPCT and [(18)F](S)-FIPCT were synthesized in 5% radiochemical yield (decay-corrected to end of bombardment (EOB)) by preparation of the precursors 2beta-carbo-R-1-mesyloxy-2-propoxy-3beta-(4-chlorop hen yl)tropane (R-12) and 2beta-carbo-S-1-mesyloxy-2-propoxy-3beta-(4-chlorop hen yl)tropane (S-12) followed by treatment with no carrier-added potassium[(18)F]fluoride and kyrptofix K222 in acetonitrile. Competition binding in cells stably expressing the transfected human DAT and serotonin transporter (SERT) labeled by [(3)H]WIN 35428 and [(3)H]citalopram, respectively, demonstrated the following order of DAT affinity (K(i) in nM): GBR 12909 (0.36) > CIT (0.48) > (S)-FIPCT (0.67) >> (R)-FIPCT (3.2). The affinity of (S)-FIPCT and (R)-FIPCT for SERT was 127- and 20-fold lower, respectively, than for DAT. In vivo biodistribution studies were performed in male rats and demonstrated that the brain uptake of [(18)F](R)-FIPCT and [(18)F](S)-FIPCT were selective and specific for DAT rich regions (caudate and putamen). PET brain imaging studies in monkeys demonstrated high [(18)F](R)-FIPCT and [(18)F](S)-FIPCT uptake in the caudate and putamen which resulted in caudate-to-cerebellum and putamen-to-cerebellum ratios of 2.5-3.5 at 115 min. [(18)F](R)-FIPCT uptake in the caudate/putamen achieved transient equilibrium at 75 min. In an imaging experiment with [(18)F](S)-FIPCT in a rhesus monkey with its left hemisphere lesioned with MPTP, radioactivity was reduced to background in the caudate and putamen of the lesioned hemisphere. The high specific activity one-step radiolabeling preparation and high specificity and selectivity of [(18)F](R)-FIPCT and [(18)F](S)-FIPCT for DAT indicate [(18)F](R)-FIPCT and [(18)F](S)-FIPCT are potential radioligands for mapping brain DAT in humans using PET.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding, Competitive
  • Carrier Proteins / metabolism*
  • Cell Line
  • Dopamine / metabolism*
  • Dopamine Plasma Membrane Transport Proteins
  • Humans
  • In Vitro Techniques
  • Macaca mulatta
  • Male
  • Membrane Glycoproteins / metabolism
  • Membrane Transport Proteins*
  • Nerve Tissue Proteins*
  • Putamen / metabolism
  • Radiopharmaceuticals / chemical synthesis*
  • Radiopharmaceuticals / chemistry
  • Radiopharmaceuticals / metabolism
  • Radiopharmaceuticals / pharmacokinetics
  • Rats
  • Rats, Sprague-Dawley
  • Serotonin / metabolism
  • Serotonin Plasma Membrane Transport Proteins
  • Stereoisomerism
  • Structure-Activity Relationship
  • Tissue Distribution
  • Tomography, Emission-Computed
  • Transfection
  • Tropanes / chemical synthesis*
  • Tropanes / chemistry
  • Tropanes / metabolism
  • Tropanes / pharmacokinetics
  • Urodela / metabolism

Substances

  • Carrier Proteins
  • Dopamine Plasma Membrane Transport Proteins
  • Membrane Glycoproteins
  • Membrane Transport Proteins
  • N-methyl-2-carbo-1-fluoro-2-isopropanoxy-3-(4-chlorophenyl)tropane
  • Nerve Tissue Proteins
  • Radiopharmaceuticals
  • SLC6A3 protein, human
  • SLC6A4 protein, human
  • Serotonin Plasma Membrane Transport Proteins
  • Slc6a3 protein, rat
  • Slc6a4 protein, rat
  • Tropanes
  • Serotonin
  • Dopamine