In Vivo Assessment and Dosimetry of 2 Novel PDE10A PET Radiotracers in Humans: F-18-MNI-659 and F-18-MNI-654

Olivier Barret*, David Thomae, Adriana Tavares, David Alagille, Caroline Papin, Rikki Waterhouse, Timothy McCarthy, Danna Jennings, Ken Marek, David Russell, John Seibyl, Gilles Tamagnan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Phosphodiesterase (PDE) 10A is an enzyme involved in the regulation of cyclic adenosine monophosphate and cyclic guanosine monophosphate and is highly expressed in medium-sized spiny neurons of the striatum, making it an attractive target for novel therapies for a variety of neurologic and psychiatric disorders that involve striatal function. Potential ligands for PET imaging of PDE10A have been reported. Here, we report the first-in-human characterization of 2 new PDE10A radioligands, 2-(2-(3-(1-(2-fluoroethyl)-1H-indazol-6-yl)-7-methyl-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione (F-18-MNI-654) and 2-(2-(3-(4-(2-fluoroethoxy)phenyl)-7-methyl-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione (F-18-MNI-659), with the goal of selecting the best one for use in future studies interrogating pathophysiologic changes in neuropsychiatric disorders and aiding pharmaceutical development targeting PDE10A. Methods: Eleven healthy volunteers participated in this study (F-18-MNI-654 test-retest, 2 men; F-18-MNI-659 test-retest, 4 men and 1 woman; F-18-MNI-659 dosimetry, 2 men and 2 women). Brain PET images were acquired over 5.5 h for F-18-MNI-654 and over 3.5 h for F-18-MNI-659, and pharmacokinetic modeling with plasma- and reference-region (cerebellar cortex)-based methods was performed. Whole-body PET images were acquired over 6 h for F-18-MNI-659 and radiation dosimetry estimated with OLINDA. Results: Both radiotracers were similarly metabolized, with about 20% of intact parent remaining at 120 min after injection. PET time activity data demonstrated that F-18-MNI-654 kinetics were much slower than F-18-MNI-659 kinetics. For F-18-MNI-659, there was good agreement between the Logan and simplified reference tissue models for nondisplaceable binding potential (BPND), supporting noninvasive quantification, with test-retest variability less than 10% and intraclass correlation greater than 0.9. The F-18-MNI-659 effective dose was estimated at 0.024 mSv/MBq. Conclusion: PET imaging in the human brain with 2 novel PDE10A F-18 tracers is being reported. Noninvasive quantification of F-18-MNI-659 with the simplified reference tissue model using the cerebellum as a reference is possible. In addition, F-18-MNI-659 kinetics are fast enough for a good estimate of BPND with 90 min of data, with values around 3.0 in the basal ganglia. Finally, F-18-MNI-659 dosimetry is favorable and consistent with values reported for other PET radiotracers currently used in humans.

Original languageEnglish
Pages (from-to)1297-1304
Number of pages8
JournalJournal of Nuclear Medicine
Volume55
Issue number8
DOIs
Publication statusPublished - Aug 2014

Keywords

  • PDE10A
  • PET imaging
  • kinetic modeling
  • test-retest
  • dosimetry
  • STRIATUM-ENRICHED PHOSPHODIESTERASE
  • EMISSION-TOMOGRAPHY RADIOLIGAND
  • REFERENCE TISSUE MODEL
  • REFERENCE REGION
  • HUMAN BRAIN
  • 10A
  • QUANTIFICATION
  • IDENTIFICATION
  • RECEPTOR
  • LIGAND

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