Identification of PET radiometabolites by cytochrome P450, UHPLC/Q-ToF-MS and fast radio-LC: applied to the PET radioligands [11C]flumazenil, [18F]FE-PE2I, and [11C]PBR28

• Published in: Analytical and bioanalytical chemistry Vol. 405; no. 4; pp. 1303 - 1310
• Main Authors: Amini, Nahid, Nakao, Ryuji, Schou, Magnus, Halldin, Christer
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.02.2013; Springer Nature B.V
• Subjects: Acetamides - chemistry; Acetamides - metabolism; Acids; Analytical Chemistry; Animals; Biochemistry; Biocompatibility; Biomedical materials; Brain research; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Chromatography; Chromatography, High Pressure Liquid - methods; Collectors; Cytochrome; Cytochrome P-450 Enzyme System - chemistry; Cytochrome P-450 Enzyme System - metabolism; Dehydrogenases; Female; Flumazenil - chemistry; Flumazenil - metabolism; Food Science; Glucose; Haplorhini; Humans; Identification; In vitro testing; In vivo testing; In vivo tests; Kinetics; Laboratory Medicine; Ligands; Liquid chromatography; Liver; Male; Mass spectrometry; Mass Spectrometry - methods; Metabolites; Microsomes, Liver - chemistry; Microsomes, Liver - metabolism; Monitoring/Environmental Analysis; Original Paper; Positron emission; Positron-Emission Tomography; Proteins; Pyridines - chemistry; Pyridines - metabolism; R&D; Radiopharmaceuticals - chemistry; Radiopharmaceuticals - metabolism; Research & development; Scientific imaging; Surgical implants; Tomography; Sweden; Positron emission tomography (PET) radioligands; Ultra high-performance liquid chromatography/quadrupole-time of flight-mass spectrometry (UHPLC/Q-ToF-MS); Radiometabolites; Fast radio-liquid chromatography (radio-LC); Cytochrome P450
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-012-6541-2

A general method is presented for the identification of radiometabolites in plasma of human and monkey subjects after administration of positron emission tomography (PET) radioligands. The radiometabolites are first produced in vitro, using liver microsomes, subsequently separated using fast radio-liquid chromatography (radio-LC), and individually collected and identified by ultra high-performance liquid chromatography/quadrupole-time of flight-mass spectrometry in MS and MS E mode. Fast radio-LC provided superior resolution compared to conventional radio-LC, resulting in separation of a greater number of metabolites. The radiometabolites produced in vivo are then compared to and identified based on the in vitro results. This approach was applied to three PET radioligands, [ 11 C]flumazenil, [ 18 F]FE-PE2I, and [ 11 C]PBR28, resulting in the identification of five, two, and one radiometabolites, respectively. This procedure can easily be adopted to identify the radiometabolites produced in vivo from a variety of PET radioligands.