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Eur J Nucl Med Mol Imaging. 2020 Feb;47(2):355-365. doi: 10.1007/s00259-019-04527-w. Epub 2019 Oct 12.

Characterization of the serotonin 2A receptor selective PET tracer (R)-[18F]MH.MZ in the human brain.

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Center for Nuclear Medicine & PET/CT Positronmed, Providencia, 7501068, Santiago, Chile.
Positronpharma SA, Providencia, 7500921, Santiago, Chile.
Center for Integrated Molecular Brain Imaging, Rigshospitalet and University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark.
Center for Nuclear Medicine & PET/CT Positronmed, Providencia, 7501068, Santiago, Chile.
Institute of Nuclear Chemistry, Johannes Gutenberg-University, Fritz-Strassmann-Weg 2, 55128, Mainz, Germany.
Positronpharma SA, Providencia, 7500921, Santiago, Chile.
Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark.
Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark.



The serotonin receptor subtype 2A antagonist (5-HT2AR) (R)-[18F]MH.MZ has in preclinical studies been identified as a promising PET imaging agent for quantification of cerebral 5-HT2ARs. It displays a very similar selectivity profile as [11C]MDL 100907, one of the most selective compounds identified thus far for the 5-HT2AR. As [11C]MDL 100907, (R)-[18F]MH.MZ also displays slow brain kinetics in various animal models; however, the half-life of fluorine-18 allows for long scan times and consequently, a more precise determination of 5-HT2AR binding could still be feasible. In this study, we aimed to evaluate the potential of (R)-[18F]MH.MZ PET to image and quantify the 5-HT2AR in the human brain in vivo.


Nine healthy volunteers underwent (R)-[18F]MH.MZ PET at baseline and four out of these also received a second PET scan, after ketanserin pretreatment. Regional time-activity curves of 17 brain regions were analyzed before and after pretreatment. We also investigated radiometabolism, time-dependent stability of outcomes measures, specificity of (R)-[18F]MH.MZ 5-HT2AR binding, and performance of different kinetic modeling approaches.


Highest uptake was determined in 5-HT2AR rich regions with a BPND of approximately 1.5 in cortex regions. No radiometabolism was observed. 1TCM and 2TCM resulted in similar outcome measure, whereas reference tissue models resulted in a small, but predictable bias. (R)-[18F]MH.MZ binding conformed to the known distribution of 5-HT2AR and could be blocked by pretreatment with ketanserin. Moreover, outcomes measures were stable after 100-110 min.


(R)-[18F]MH.MZ is a suitable PET tracer to image and quantify the 5-HT2AR system in humans. In comparison with [11C]MDL 100907, faster and more precise outcome measure could be obtained using (R)-[18F]MH.MZ. We believe that (R)-[18F]MH.MZ has the potential to become the antagonist radiotracer of choice to investigate the human 5-HT2AR system.


5-HT2A receptor; Kinetic modeling; MDL 100907; Positron emission tomography (PET); [18F]MH.MZ


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