Institute of Pharmacy , University of Regensburg , D-93053 Regensburg , Germany.
Department of Chemistry, School of Science , University of Tokyo , 7-3-1 Bunkyo-ku , Hongo , Tokyo 113-0033 , Japan.
J Med Chem. 2019 Sep 12;62(17):8338-8356. doi: 10.1021/acs.jmedchem.9b01342. Epub 2019 Aug 30.
Differences in sequence homology between human (h), mouse (m), and rat (r) histamine H receptors (HR) cause discrepancies regarding affinities, potencies, and/or efficacies of ligands and therefore compromise translational animal models and the applicability of radioligands. Aiming at a radioligand enabling robust and comparative binding studies at the h/m/rHRs, 2,4-diaminopyrimidines were synthesized and pharmacologically investigated. The most notable compounds identified were two (partial) agonists with comparable potencies at the h/m/rHRs: UR-DEBa148 (-neopentyl-4-(1,4,6,7-tetrahydro-5-imidazo[4,5-]pyridin-5-yl)pyrimidin-2-amine bis(2,2,2-trifluoroacetate), ), the most potent [pEC (reporter gene assay) = 9.9/9.6/10.3] compound in the series being slightly G-protein biased and UR-DEBa176 [()-4-[3-(dimethylamino)pyrrolidin-1-yl]--neopentylpyrimidin-2-amine bis(2,2,2-trifluoroacetate), , pEC (reporter gene assay) = 8.7/9.0/9.2], a potential "cold" form of a tritiated HR ligand. After radiolabeling, binding studies with [H]UR-DEBa176 ([H]) at the h/m/rHRs revealed comparable values (41/17/22 nM), low nonspecific binding (11-17%, ∼), and fast associations/dissociations (25-30 min) and disclosed [H]UR-DEBa176 as useful molecular tool to determine h/m/rHR binding affinities for HR ligands.
人类（h）、小鼠（m）和大鼠（r）组胺 H 受体（HR）之间序列同源性的差异导致配体的亲和力、效力和/或功效存在差异，从而影响了转化动物模型和放射性配体的适用性。为了开发一种能够在 h/m/rHR 上进行强大且可比的结合研究的放射性配体，我们合成并研究了 2,4-二氨基嘧啶。鉴定出的最显著的化合物是两种（部分）激动剂，它们在 h/m/rHR 上具有相当的效力：UR-DEBa148（-正戊基-4-（1,4,6,7-四氢-5-咪唑并[4,5-d]嘧啶-5-基）嘧啶-2-胺双（2,2,2-三氟乙酸酯）），该系列中最有效的 [pEC（报告基因测定）=9.9/9.6/10.3] 化合物略微偏向 G 蛋白，而 UR-DEBa176 [()-4-[3-（二甲基氨基）吡咯烷-1-基]- -正戊基嘧啶-2-胺双（2,2,2-三氟乙酸酯）]，pEC（报告基因测定）=8.7/9.0/9.2]，是一种潜在的 HR 配体的“冷”形式。放射性标记后，用 [H]UR-DEBa176 ([H]) 在 h/m/rHR 上进行的结合研究显示出相当的 Kd 值（41/17/22 nM），低非特异性结合（11-17%，∼），快速的缔合/解离（25-30 min），并揭示 [H]UR-DEBa176 是一种有用的分子工具，可用于确定 HR 配体与 HR 受体的结合亲和力。
