Automated radiosynthesis of [C-11]MTP38-a phosphodiesterase 7 imaging tracer-using [C-11]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-11]carbonitrile ([C-11]MTP38) as a positron emission tomography (PET) tracer for the imaging of phosphodiesterase 7. For the fully automated production of [C-11]MTP38 routinely and efficiently for clinical applications, we determined the radiosynthesis procedure of [C-11]MTP38 using [C-11]hydrogen cyanide ([C-11]HCN) as a PET radiopharmaceutical. Radiosynthesis of [C-11]MTP38 was performed using an automated C-11-labeling synthesizer developed in-house within 40 min after the end of irradiation. [C-11]MTP38 was obtained with a relatively high radiochemical yield (33 +/- 5.5% based on [C-11]CO2 at the end of irradiation, decay-corrected, n = 15), radiochemical purity (>97%, n = 15), and molar activity (47 +/- 12 GBq/mu mol at the end of synthesis, n = 15). All the results of the quality control (QC) testing for the [C-11]MTP38 injection complied with our in-house QC and quality assurance specifications. We successfully automated the radiosynthesis of [C-11]MTP38 for clinical applications using an C-11-labeling synthesizer and sterile isolator. Taken together, this protocol provides a new radiopharmaceutical [C-11]MTP38 suitable for clinical applications.