In vivo PET Imaging of [11C]CIMBI-5, a 5-HT2AR Agonist Radiotracer in Nonhuman Primates
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In vivo PET Imaging of [11C]CIMBI-5, a 5-HT2AR Agonist Radiotracer in Nonhuman Primates. / Prabhakaran, Jaya; DeLorenzo, Christine; Zanderigo, Francesca; Knudsen, Gitte M; Gilling, Nic; Pratap, Mali; Jorgensen, Matthew J; Daunais, James; Kaplan, Jay R; Parsey, Ramin V; Mann, J John; Kumar, Dileep.
In: Journal of Pharmacy and Pharmaceutical Sciences, Vol. 22, 2019, p. 352-364.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - In vivo PET Imaging of [11C]CIMBI-5, a 5-HT2AR Agonist Radiotracer in Nonhuman Primates
AU - Prabhakaran, Jaya
AU - DeLorenzo, Christine
AU - Zanderigo, Francesca
AU - Knudsen, Gitte M
AU - Gilling, Nic
AU - Pratap, Mali
AU - Jorgensen, Matthew J
AU - Daunais, James
AU - Kaplan, Jay R
AU - Parsey, Ramin V
AU - Mann, J John
AU - Kumar, Dileep
PY - 2019
Y1 - 2019
N2 - PURPOSE: 5-HT2AR exists in high and low affinity states. Agonist PET tracers measure binding to the active high affinity site and thus provide a functionally relevant measure of the receptor. Limited in vivo data have been reported so far for a comparison of agonist versus antagonist tracers for 5-HT2AR used as a proof of principle for measurement of high and low affinity states of this receptor. We compared the in vivo binding of [11C]CIMBI-5, a 5-HT2AR agonist, and of the antagonist [11C]M100907, in monkeys and baboons.METHODS: [11C]CIMBI-5 and [11C]M100907 baseline PET scans were performed in anesthetized male baboons (n=2) and male vervet monkeys (n=2) with an ECAT EXACT HR+ and GE 64-slice PET/CT Discovery VCT scanners. Blocking studies were performed in vervet monkeys by pretreatment with MDL100907 (0.5 mg/kg, i.v.) 60 minutes prior to the scan. Regional distribution volumes and binding potentials were calculated for each ROI using the likelihood estimation in graphical analysis and Logan plot, with either plasma input function or reference region as input, and simplified reference tissue model approaches.RESULTS: PET imaging of [11C]CIMBI-5 in baboons and monkeys showed the highest binding in 5-HT2AR-rich cortical regions, while the lowest binding was observed in cerebellum, consistent with the expected distribution of 5-HT2AR. Very low free fractions and rapid metabolism were observed for [11C]CIMBI-5 in baboon plasma. Binding potential values for [11C]CIMBI-5 were 25-33% lower than those for [11C]MDL100907 in the considered brain regions.CONCLUSION: The lower binding potential of [11C]CIMBI-5 in comparison to [11C]MDL100907 is likely due to the preferential binding of the former to the high affinity site in vivo in contrast to the antagonist, [11C]MDL100907, which binds to both high and low affinity sites.
AB - PURPOSE: 5-HT2AR exists in high and low affinity states. Agonist PET tracers measure binding to the active high affinity site and thus provide a functionally relevant measure of the receptor. Limited in vivo data have been reported so far for a comparison of agonist versus antagonist tracers for 5-HT2AR used as a proof of principle for measurement of high and low affinity states of this receptor. We compared the in vivo binding of [11C]CIMBI-5, a 5-HT2AR agonist, and of the antagonist [11C]M100907, in monkeys and baboons.METHODS: [11C]CIMBI-5 and [11C]M100907 baseline PET scans were performed in anesthetized male baboons (n=2) and male vervet monkeys (n=2) with an ECAT EXACT HR+ and GE 64-slice PET/CT Discovery VCT scanners. Blocking studies were performed in vervet monkeys by pretreatment with MDL100907 (0.5 mg/kg, i.v.) 60 minutes prior to the scan. Regional distribution volumes and binding potentials were calculated for each ROI using the likelihood estimation in graphical analysis and Logan plot, with either plasma input function or reference region as input, and simplified reference tissue model approaches.RESULTS: PET imaging of [11C]CIMBI-5 in baboons and monkeys showed the highest binding in 5-HT2AR-rich cortical regions, while the lowest binding was observed in cerebellum, consistent with the expected distribution of 5-HT2AR. Very low free fractions and rapid metabolism were observed for [11C]CIMBI-5 in baboon plasma. Binding potential values for [11C]CIMBI-5 were 25-33% lower than those for [11C]MDL100907 in the considered brain regions.CONCLUSION: The lower binding potential of [11C]CIMBI-5 in comparison to [11C]MDL100907 is likely due to the preferential binding of the former to the high affinity site in vivo in contrast to the antagonist, [11C]MDL100907, which binds to both high and low affinity sites.
U2 - 10.18433/jpps30329
DO - 10.18433/jpps30329
M3 - Journal article
C2 - 31356761
VL - 22
SP - 352
EP - 364
JO - Journal of Pharmacy and Pharmaceutical Sciences
JF - Journal of Pharmacy and Pharmaceutical Sciences
SN - 1482-1826
ER -
ID: 237516928