The automated radiosynthesis and purification of the opioid receptor antagonist, [6-O-methyl-11C]diprenorphine on the GE TRACERlab FXFE radiochemistry module

• Published in: Journal of labelled compounds & radiopharmaceuticals Vol. 57; no. 5; pp. 388 - 396
• Main Authors: Fairclough, Michael, Prenant, Christian, Brown, Gavin, McMahon, Adam, Lowe, Jonathan, Jones, Anthony
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 15.05.2014; Wiley Subscription Services, Inc
• Subjects: [11C]diprenorphine; automated radiosynthesis; Carbon Radioisotopes - chemistry; Diprenorphine - chemistry; Equipment Design; Isotope Labeling - instrumentation; Isotope Labeling - methods; methyl triflate; Narcotic Antagonists; opioid receptors; positron emission tomography; Positron-Emission Tomography - methods; Radiopharmaceuticals - chemical synthesis; Robotics - instrumentation; Robotics - methods; opioid receptors; automated radiosynthesis; positron emission tomography; methyl triflate; [11C]diprenorphine
• DOI: 10.1002/jlcr.3194
• ISSN: 0362-4803

[6‐O‐Methyl‐11C]diprenorphine ([11C]diprenorphine) is a positron emission tomography ligand used to probe the endogenous opioid system in vivo. Diprenorphine acts as an antagonist at all of the opioid receptor subtypes, that is, μ (mu), κ (kappa) and δ (delta). The radiosynthesis of [11C]diprenorphine using [11C]methyl iodide produced via the ‘wet’ method on a home‐built automated radiosynthesis set‐up has been described previously. Here, we describe a modified synthetic method to [11C]diprenorphine performed using [11C]methyl iodide produced via the gas phase method on a GE TRACERlab FXFE radiochemistry module. Also described is the use of [11C]methyl triflate as the carbon‐11 methylating agent for the [11C]diprenorphine syntheses. [11C]Diprenorphine was produced to good manufacturing practice standards for use in a clinical setting. In comparison to previously reported [11C]diprenorphine radiosyntheisis, the method described herein gives a higher specific activity product which is advantageous for receptor occupancy studies. The radiochemical purity of [11C]diprenorphine is similar to what has been reported previously, although the radiochemical yield produced in the method described herein is reduced, an issue that is inherent in the gas phase radiosynthesis of [11C]methyl iodide. The yields of [11C]diprenorphine are nonetheless sufficient for clinical research applications. Other advantages of the method described herein are an improvement to both reproducibility and reliability of the production as well as simplification of the purification and formulation steps. We suggest that our automated radiochemistry route to [11C]diprenorphine should be the method of choice for routine [11C]diprenorphine productions for positron emission tomography studies, and the production process could easily be transferred to other radiochemistry modules such as the TRACERlab FX C pro. © 2014 The Authors. Journal of Labelled Compounds and Radiopharmaceuticals Published by John Wiley & Sons Ltd. [6‐O‐Methyl‐11C]diprenorphine ([11C]diprenorphine) is a positron emission tomography (PET) ligand used to probe the endogenous opioid system in vivo and has been used with PET for various physiological studies. Our work describes the automation and optimization of the radiosynthesis of [11C]diprenorphine with high‐specific activity, to give a robust and reliable production process which produces the ligand in compliance to good manufacturing practices, for clinical PET scans.