Automated radiosynthesis of [ C]MTP38-a phosphodiesterase 7 imaging tracer-using [ C]hydrogen cyanide for clinical applications.

We have developed 8-amino-3-(2S,5R-dimethyl-1-piperidyl)-[1,2,4]triazolo[4,3-a]pyrazine-5-[ C]carbonitrile ([ C]MTP38) as a positron emission tomography (PET) tracer for the imaging of phosphodiesterase 7. For the fully automated production of [ C]MTP38 routinely and efficiently for clinical applications, we determined the radiosynthesis procedure of [ C]MTP38 using [ C]hydrogen cyanide ([ C]HCN) as a PET radiopharmaceutical. Radiosynthesis of [ C]MTP38 was performed using an automated C-labeling synthesizer developed in-house within 40 min after the end of irradiation. [ C]MTP38 was obtained with a relatively high radiochemical yield (33 ± 5.5% based on [ C]CO at the end of irradiation, decay-corrected, n = 15), radiochemical purity (>97%, n = 15), and molar activity (47 ± 12 GBq/μmol at the end of synthesis, n = 15). All the results of the quality control (QC) testing for the [ C]MTP38 injection complied with our in-house QC and quality assurance specifications. We successfully automated the radiosynthesis of [ C]MTP38 for clinical applications using an C-labeling synthesizer and sterile isolator. Taken together, this protocol provides a new radiopharmaceutical [ C]MTP38 suitable for clinical applications.