Kainate receptors play a crucial role in mediating synaptic transmission within the central nervous system. However, the lack of selective pharmacological tool compounds for the GluK3 subunit represents a significant challenge in studying these receptors. Recently presented compound 1 stands out as a potent antagonist of GluK3 receptors, exhibiting nanomolar affinity at GluK3 receptors and strongly inhibiting glutamate-induced currents at homomeric GluK1 and GluK3 receptors in HEK293 cells with Kb values of 65 and 39 nM, respectively. This study presents the synthesis of two potent GluK3-preferring iodine derivatives of compound 1, serving as precursors for radiolabelling. Furthermore, we demonstrate the optimisation of dehalogenation conditions using hydrogen and deuterium, resulting in [2H]-1, and demonstrate the efficient synthesis of the radioligand [3H]-1 with a specific activity of 1.48 TBq/mmol (40.1 Ci/mmol). Radioligand binding studies conducted with [3H]-1 as a radiotracer at GluK1, GluK2, and GluK3 receptors expressed in Sf9 and rat P2 membranes demonstrated its potential applicability for selectively studying native GluK3 receptors in the presence of GluK1 and 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-blocking ligands.

Department of Drug Design and Pharmacology Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark

Department of Technology and Biotechnology of Drugs Jagiellonian University Medical College in Kraków Kraków Poland

Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences Prague Czech Republic

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Watkins JC, Jane DE. The glutamate story. Br J Pharmacol. 2006;147(S1):S100‐S108. doi:10.1038/sj.bjp.0706444

Jane DE, Lodge D, Collingridge GL. Kainate receptors: pharmacology, function and therapeutic potential. Neuropharmacology. 2009;56(1):90‐113. doi:10.1016/j.neuropharm.2008.08.023

Schoepp DD, Jane DE, Monn JA. Pharmacological agents acting at subtypes of metabotropic glutamate receptors. Neuropharmacology. 1999;38(10):1431‐1476. doi:10.1016/s0028‐3908(99)00092‐1

Valbuena S, Lerma J. Kainate receptors, homeostatic gatekeepers of synaptic plasticity. Neuroscience. 2021;456:17‐26. doi:10.1016/j.neuroscience.2019.11.050

Hansen KB, Wollmuth LP, Bowie D, et al. Structure, function, and pharmacology of glutamate receptor ion channels. Pharmacol Rev. 2021;73(4):298‐487. doi:10.1124/pharmrev.120.000131

Stawski P, Janovjak H, Trauner D. Pharmacology of ionotropic glutamate receptors: a structural perspective. Bioorg Med Chem. 2010;18(22):7759‐7772. doi:10.1016/j.bmc.2010.09.012

Catarzi D, Colotta V, Varano F. Competitive AMPA receptor antagonists. Med Res Rev. 2007;27(2):239‐278. doi:10.1002/med.20084

Kristensen O, Kristensen LB, Møllerud S, Frydenvang K, Pickering DS, Kastrup JS. The structure of a high‐affinity kainate receptor: GluK4 ligand‐binding domain crystallized with kainate. Structure. 2016;24(9):1582‐1589. doi:10.1016/j.str.2016.06.019

Møllerud S, Kastrup JS, Pickering DS. A pharmacological profile of the high‐affinity GluK5 kainate receptor. Eur J Pharmacol. 2016;788:315‐320. doi:10.1016/j.ejphar.2016.06.049

Sagot E, Pickering DS, Pu X, et al. Chemo‐enzymatic synthesis of a series of 2,4‐syn‐functionalized (S)‐glutamate analogues: new insight into the structure‐activity relation of ionotropic glutamate receptor subtypes 5, 6, and 7. J Med Chem. 2008;51(14):4093‐4103. doi:10.1021/jm800092x

Toms NJ, Reid ME, Phillips W, Kemp MC, Roberts PJ. A novel kainate receptor ligand [3H]‐(2S,4R)‐4‐methylglutamate: pharmacological characterization in rabbit brain membranes. Neuropharmacology. 1997;36(11‐12):1483‐1488. doi:10.1016/s0028‐3908(97)00161‐5

Hoo K, Legutko B, Rizkalla G, et al. [3H]ATPA: a high affinity ligand for GluR5 kainate receptors. Neuropharmacology. 1999;38(12):1811‐1817. doi:10.1016/s0028‐3908(99)00133‐1

Alcaide A, Marconi L, Marek A, et al. Synthesis and pharmacological characterization of the selective GluK1 radioligand (S)‐2‐amino‐3‐(6[3H]‐2,4‐dioxo‐3,4‐dihydrothieno[3,2‐d]pyrimidin‐1(2H)‐yl)propanoic acid ([3H]‐NF608). Med Chem Commun. 2016;7(11):2136‐2144. doi:10.1039/c6md00339g

Pallesen J, Møllerud S, Frydenvang K, et al. N1‐substituted quinoxaline‐2,3‐diones as kainate receptor antagonists: X‐ray crystallography, structure‐affinity relationships, and in vitro pharmacology. ACS Chem Nerosci. 2019;10(3):1841‐1853. doi:10.1021/acschemneuro.8b00726

Møllerud S, Hansen RB, Pallesen J, et al. N‐(7‐(1H‐imidazol‐1‐yl)‐2,3‐dioxo‐6‐(trifluoromethyl)‐3,4‐dihydroquinoxalin‐1(2H)‐yl)benzamide, a new kainate receptor selective antagonist and analgesic: synthesis, X‐ray crystallography, structure‐affinity relationships, and in vitro and in vivo pharmacology. ACS Chem Nerosci. 2019;10(11):4685‐4695. doi:10.1021/acschemneuro.9b00479

Chalupnik P, Vialko A, Pickering DS, et al. Discovery of the first highly selective antagonist of the GluK3 kainate receptor subtype. Int J Mol Sci. 2022;23(15):8797. doi:10.3390/ijms23158797

Møllerud S, Pinto A, Marconi L, et al. Structure and affinity of two bicyclic glutamate analogues at AMPA and kainate receptors. ACS Chem Nerosci. 2017;8(9):2056‐2064. doi:10.1021/acschemneuro.7b00201

Quattropani A, Swinnen D, Inventors. Imidazo‐oxadiazole and imidazo‐thiadiazole derivatives. US‐2015175628‐A1. 25 june 2015.

Zarrinmayeh H, Bleakman D, Gates MR, et al. [3H]N‐2‐(4‐(N‐benzamido)phenyl)propyl‐2‐propanesulfonamide: a novel AMPA receptor potentiator and radioligand. J Med Chem. 2001;44(3):302‐304. doi:10.1021/jm000462n