Design, Synthesis, and Evaluation of [18F]T-914 as a Novel Positron-Emission Tomography Tracer for Lysine-Specific Demethylase 1.

Satoru Matsuda,Vincent M Carroll,Alexandra Gouasmat,Tohru Yamashita,Jumpei Aida,Gilles Tamagnan,Tatsuki Koike,Paul Mcquade,Olivier Barret,Christine M Sandiego,Yasushi Hattori,Kouta Matsumiya,Haruhide Kimura

doi:10.1021/acs.jmedchem.1c00653

Abstract

Histone methylation is associated with the pathophysiology of neurodevelopmental disorders. Lysine-specific demethylase 1 (LSD1) catalyzes histone demethylation in a flavin adenine dinucleotide (FAD)-dependent manner. Thus, inhibiting LSD1 enzyme activity could offer a novel way to treat neurodevelopmental disorders. Assessing LSD1 target engagement using positron-emission tomography (PET) imaging could aid in developing therapeutic LSD1 inhibitors. In this study, PET probes based on 4-(2-aminocyclopropyl)benzamide derivatives that bind irreversibly to FAD found in LSD1 were examined. By optimizing the profiles of brain penetrance and brain-penetrant metabolites, T-914 (1g) was identified as a suitable PET tracer candidate. PET studies in nonhuman primates demonstrated that [18F]1g had heterogeneous brain uptake, which corresponded to known LSD1 expression levels. Moreover, brain uptake of [18F]1g was reduced by coadministration of unlabeled 1g, demonstrating blockable binding. These data suggest that [18F]1g warrants further investigation as a potential PET tracer candidate for assessing target engagement of LSD1.

Highlights

Neurodevelopmental disorders result in severe and lifelong disabilities, and epigenetic dysregulation is potentially associated with their pathophysiology.[1]
Lysine-specific demethylase 1 (LSD1) has scaffolding function for cofactors including growth factor independence 1B (GFI1B) which regulates hematopoiesis, and the cofactor binding occurs near the flavin adenine dinucleotide (FAD) binding site.[4−7] Known irreversible LSD1 inhibitors target FAD and produce bulky FAD adducts occupying the cofactor binding space in the vicinity of FAD, where they inhibit both LSD1 enzyme activity and its scaffolding activity for cofactors.[5,8−10] On the other hand, the novel irreversible LSD1 inhibitors found by Takeda Pharmaceutical Company Limited (T-448 and TAK-418; ClinicalTrials.gov Identifier: NCT03228433 and NCT03501069) have been designed to only inhibit the LSD1 enzyme activity without dissociating the cofactor GFI1B from LSD1 complex by generating compact formylated FAD adducts.[5,11]
The compound 1g was selected as a potential Positron-emission tomography (PET) tracer candidate, and baseline and self-blocking scans were conducted in nonhuman primates

Summary

■ INTRODUCTION

Neurodevelopmental disorders result in severe and lifelong disabilities, and epigenetic dysregulation is potentially associated with their pathophysiology.[1]. Derivatives of 1a were examined to minimize the production of brain-penetrable fluorine-containing metabolites From these efforts, the compound 1g was selected as a potential PET tracer candidate, and baseline and self-blocking scans were conducted in nonhuman primates. The MDR1 efflux ratios of all compounds tested here were ≤1.4, and these were not considered to be P-glycoprotein (Pgp) substrates Among these derivatives, 1c, 1f, and 1g, which displayed potent LSD1 inhibitory activity, were chosen for metabolite analysis in rats. In vitro metabolite analyses using human, rat, and monkey cryopreserved hepatocytes suggest that 1g will not generate human-specific brain-penetrating metabolites These results are consistent with the high performance of [18F]1g in nonhuman primate PET scanning, emphasizing the importance of detailed metabolite profiling in the medicinal chemistry optimization stage of tracer candidate evaluation. The potential of [18F]1g will be corroborated by further blocking studies with different LSD1 inhibitors in nonhuman primates and humans

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES