Simple and fully automated preparation of [carbonyl-11C]WAY-100635

Summary. So far, [carbonyl- 11 C]WAY-100635 is the PET-tracer of choice for 5HT 1A -receptor-imaging. Since thepreparation is still a challenge, we aimed at (1) the eval-uation of various essential parameters for the successfulpreparation, (2) the simplification of the radiosynthesis and(3) the establishment of a safe and fully automated system.The preparation is based on a commercial synthesizer andall chemicals are used without further processing. We founda low failure rate (7 . 7%), high average yield (4 . 0±1 . 0GBq)and a specific radioactivity of 292 ±168 GBq / µmol (both atthe end of synthesis, EOS). Introduction Carbon-11 labelled WAY-100635 ( N -(2-(1-(4-(2-methoxy-phenyl)-1-piperazinyl)ethyl))- N -(2-pyridyl)-cyclohexane-carboxamide; WAY) was introduced into positron emis-sion tomography (PET) as a highly potent and selectiveantagonist at the 5HT 1A receptors more than a decade ago.Since 5HT 1A receptors are implicated in the pathogenesisof anxiety, depression, eating disorders and motion sick-ness, they are an important target for drug therapy [1,2].The visualisation and quantification of this receptor is a ba-sis for further exploration of molecular pathologies causingpsychiatric conspicuousness. The most extensively studiedtracers are two carbon-11 labelled WAY-100635 derivatives,[O-methyl