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. 2018 Sep 5:157:898-908.
doi: 10.1016/j.ejmech.2018.08.019. Epub 2018 Aug 9.

Synthesis, pharmacology and preclinical evaluation of 11C-labeled 1,3-dihydro-2H-benzo[d]imidazole-2-ones for imaging γ8-dependent transmembrane AMPA receptor regulatory protein

Zhen Chen  1 , Wakana Mori  2 , Xiaofei Zhang  3 , Tomoteru Yamasaki  2 , Patrick J Dunn  4 , Genwei Zhang  5 , Hualong Fu  3 , Tuo Shao  3 , Yiding Zhang  2 , Akiko Hatori  2 , Longle Ma  3 , Masayuki Fujinaga  2 , Lin Xie  2 , Xiaoyun Deng  3 , Hua Li  3 , Qingzhen Yu  3 , Jian Rong  3 , Lee Josephson  3 , Jun-An Ma  6 , Yihan Shao  5 , Susumu Tomita  4 , Ming-Rong Zhang  7 , Steven H Liang  8
Affiliations

Synthesis, pharmacology and preclinical evaluation of 11C-labeled 1,3-dihydro-2H-benzo[d]imidazole-2-ones for imaging γ8-dependent transmembrane AMPA receptor regulatory protein

Zhen Chen et al. Eur J Med Chem. .

Abstract

a-Amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are implicated in the pathology of neurological diseases such as epilepsy and schizophrenia. As pan antagonists for this target are often accompanied with undesired effects at high doses, one of the recent drug discovery approaches has shifted to subtype-selective AMPA receptor (AMPAR) antagonists, specifically, via modulating transmembrane AMPAR regulatory proteins (TARPs). The quantification of AMPARs by positron emission tomography (PET) would help obtain insights into disease conditions in the living brain and advance the translational development of AMPAR antagonists. Herein we report the design, synthesis and preclinical evaluation of a series of TARP γ-8 antagonists, amenable for radiolabeling, for the development of subtype-selective AMPAR PET imaging agents. Based on the pharmacology evaluation, molecular docking studies and physiochemical properties, we have identified several promising lead compounds 3, 17-19 and 21 for in vivo PET studies. All candidate compounds were labeled with [11C]COCl2 in high radiochemical yields (13-31% RCY) and high molar activities (35-196 GBq/μmol). While tracers 30 ([11C]17) &32 ([11C]21) crossed the blood-brain barrier and showed heterogeneous distribution in PET studies, consistent with TARP γ-8 expression, high nonspecific binding prevented further evaluation. To our delight, tracer 31 ([11C]3) showed good in vitro specific binding and characteristic high uptake in the hippocampus in rat brain tissues, which provides the guideline for further development of a new generation subtype selective TARP γ-8 dependent AMPAR tracers.

Keywords: AMPA; Epilepsy; Ionotropic glutamate receptor; Positron emission tomography; TARP; Transmembrane AMPA receptor regulatory protein.

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Conflict of interest statement

Notes

The authors declare no competing financial interest.

Figures

Figure 1.
Figure 1.
Representative AMPAR antagonists
Figure 2.
Figure 2.
Representative AMPAR PET tracers
Figure 3.
Figure 3.
Inhibition of TARPγ−8-dependent AMPAR activity by antagonists. GluA1 and TARPγ−8 were co-expressed in HEK293 cells and stimulated by glutamate and cyclothiazide. Maximal inhibition was defined by the noncompetitive AMPAR antagonist GYKI53655. A) Inhibition by 300 nM candidate compounds. B) Dose-response curves of 3, 17–19 and 21 for inhibition of AMPA TARPγ−8. IC50 values were 19.5 nM (3), 235.3 nM (17), 90.9 nM (18), 103.3 nM (19), and 42.6 nM (21). C) Dose-response curves of 3, 17–19 and 21 for inhibition of AMPA TARPγ−2.
Figure 4.
Figure 4.
Homology model of TARP γ−8. (A) Viewed parallel to the membrane; (B) Viewed from the extracellular side of the membrane.
Figure 5.
Figure 5.
Interactions between TARP γ−8 and candidate compounds 3, 17–19 and 21. A) The overview of the docking pose of the candidate compounds 3, 17–19 and 21 onto TARP γ−8, and B) the zoom-in view of potential interacting residues of TARP γ−8 with the candidate compounds.
Figure 6.
Figure 6.
Representative PET images and time-activity curves of 30–32 in rat brain: (A) baseline PET images (summed 0–60 min) of 32; (B and C) time-activity curve of 32 and 30 under baseline in the region of hippocampus (high expression) and cerebellum (low expression); (D) baseline PET images (summed 0–60 min) of 31 and (E) whole brain time-activity curve of 31 under baseline and blocking conditions (1 mg/kg, JNJ56022486).
Figure 7.
Figure 7.
Ex vivo biodistribution in mice at four different time points (5, 15, 30 and 60 min) post injection of 31. All data are mean ± SD, n = 4. Asterisks indicate statistical significance. * p < 0.05, and ** p ≤ 0.01.
Figure 8.
Figure 8.
Ex vivo biodistribution in mice at four different time points (5, 15, 30 and 60 min) post injection of 31. All data are mean ± SD, n = 4. Asterisks indicate statistical significance. * p < 0.05, and ** p ≤ 0.01.
Scheme 1.
Scheme 1.
Synthesis of TARP ɣ8-dependent AMPA antagonists. Conditions: (i) PdCl2(dtbpf), K3PO4, 1,4-dioxane/H2O, 100 oC, 2 h; <10% yield for 3; 53% yield for 9; 74% yield for 10; 86% yield for 11; 42% yield for 12; 46% yield for 13; 75% yield for 14; 66% yield for 15; 85% yield for 16; 62% yield for 27 over two steps; 83% yield for 28 over two steps; 78% yield for 29 over two steps; (ii) PdCl2(dppf), Na2CO3, 1,4-dioxane/H2O, 80 oC, 16 h; (iii) Fe, conc. HCl, EtOH/H2O, reflux for 2 h; 67% yield for 5 over two steps; 46% yield for 9 over two steps; (iv) CDI, THF, rt, 16h; 90% yield for 3; 68% yield for 17; 52% yield for 18; 64% yield for 19; 78% yield for 20; 67% yield for 21; 63% yield for 22; 63% yield for 23; 82% yield for 24; (v) (Boc)2O, NaH, DMF, rt, 2 h. dtbpf = 1,1′-bis(di-tert-butylphosphino)ferrocene; dppf = 1,1′-bis(diphenylphosphino)ferrocene; DMF = N,N-dimethylformamide; CDI = 1,1’-carbonyldiimidazole; (Boc)2O = di-tert-butyl dicarbonate.
Scheme 2.
Scheme 2.
Radiolabeling of tracers 30–33. Conditions: [11C]COCl2, Et3N, THF; 30 oC, 1 min.
Scheme 3.
Scheme 3.
brain efflux transporter inhibition experiments
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References

    1. Meldrum BS, Glutamate as a neurotransmitter in the brain: review of physiology and pathology, J. Nutr, 130 (2000) 1007S–1015S. - PubMed
    1. Watkins JC, Jane DE, The glutamate story, Br. J. Pharmacol, 147 (2006) S100–S108. - PMC - PubMed
    1. Dingledine R, Borges K, Bowie D, Traynelis SF, The glutamate receptor ion channels, Pharmacol. Rev, 51 (1999) 7–61. - PubMed
    1. Mayer ML, Armstrong N, Structure and function of glutamate receptor ion channels, Annu. Rev. Physiol, 66 (2004) 161–181. - PubMed
    1. Traynelis SF, Wollmuth LP, McBain CJ, Menniti FS, Vance KM, Ogden KK, Hansen KB, Yuan HJ, Myers SJ, Dingledine R, Glutamate receptor ion channels: structure, regulation, and function, Pharmacol. Rev, 62 (2010) 405–496. - PMC - PubMed

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