Dopamine D3 receptor antagonists: the quest for a potentially selective PET ligand. Part 3: Radiosynthesis and in vivo studies.

Compound 1 is a potent and selective antagonist of the dopamine D(3) receptor. With the aim of developing a carbon-11 labeled ligand for the dopamine D(3) receptor, 1 was selected as a potential PET probe. [(11)C]1 was obtained by palladium catalyzed cross coupling using [(11)C]cyanide and 4 with a specific activity of 55.5+/-25.9GBq/micromol (1.5+/-0.7Ci/micromol). [(11)C]1 was tested in porcine and non-human primate models to assess its potential as a radioligand for PET imaging of the dopamine D(3) receptor. We conclude that in both species and despite appropriate in vitro properties, [(11)C]1 does not show any specific signal for the dopamine D(3) receptor.