Non-peptide Mu Opioid Receptor Selective Antagonists

描述(申请人提供)：阿片依赖是最严重的慢性和复发性成瘾障碍之一。已经证明，对于许多临床上可用的阿片类药物，它们的镇痛功能和臭名昭著的副作用(如成瘾和滥用倾向)主要是由于它们与Mu阿片受体(Mor)的相互作用。我们的长期目标是开发高选择性的MOR拮抗剂，作为化学探针来研究MOR的构效关系，以帮助开发副作用更少、成瘾和滥用倾向更小的新型潜在止痛药。这项研究背后的具体假设是，6-杂芳基取代的纳曲胺衍生物可能是MOR的选择性拮抗剂。我们的假设是基于以下事实：首先，设计和合成了一系列作为6-杂芳基取代的纳曲胺衍生物的初级配体，表现出对MOR的高选择性。其次，部分配体对MOR表现出较强的拮抗作用。第三，分子模拟研究表明，这些配体可能与受体的胞外环(EL)结构域，特别是EL2和EL3具有特异性相互作用。研究发现，MOR的EL3对MOR选择性激动剂的结合非常关键。定点突变研究表明EL3上的某些氨基酸残基可能是配体(包括激动剂和拮抗剂)选择性所必需的。基于这些观察，本建议的重点是6-杂芳基取代的纳曲胺衍生物作为MOR非肽拮抗剂的合成和评价。具体目标是：1.以初步合成和药理筛选得到的先导化合物为基础，设计合成新型Mu阿片受体拮抗剂化合物。MOR的同源建模和纳曲酮与MOR模型的对接允许假想地识别结合口袋中独特的氨基酸残基，与Delta和kappa阿片受体拮抗剂结合部位的相应(或保守)基因座相比较。设计、合成和测试了两个系列的新型配体，它们携带了独特的结构特征与MOR的EL3(和/或EL2)相互作用，从而满足了MOR结合口袋的要求。已为初步研究确定了两种先导化合物。根据这两个先导化合物的化学结构，设计了几个新的系列配体。为了实现这些新的配体，提出了化学合成路线。2.作为MOR选择性拮抗剂合成的化合物的药理评价将集中在体外放射配基结合试验以确定亲和力和选择性，功能性35S-GTP[3S]结合试验以确定疗效，以及体内行为试验。3.将进行分子模拟研究辅助的定点突变研究，以验证配体的结合方式，并进一步表征MOR的拮抗剂结合部位，为下一代拮抗剂的设计提供依据。与公众健康相关我们的长期目标是开发高度选择性的非肽类阿片受体拮抗剂作为化学探针，研究其结构和功能之间的关系，以帮助开发没有或较少成瘾和滥用倾向的潜在止痛药。本研究计划的重点是合成和测试具有结构特征的u阿片受体非肽拮抗剂，以与受体的胞外环区相互作用，我们预计这将赋予u阿片受体高的选择性。我们相信，这些配体将作为重要的药理学工具来研究Mu阿片受体的结构-功能关系。

DESCRIPTION (provided by applicant): Opioid dependence is one of the most serious chronic and relapsing addictive disorders. It has been proven that for many clinical available opiates, both their analgesic function and their notorious side effects (such as addiction and abuse liability) are primarily due to their interaction with the mu opioid receptor (MOR). Our long- term goal is to develop highly selective antagonists for MOR as chemical probes to study MOR structure- efficacy relationship to assist the development of novel potential analgesics with fewer side effects and less addiction and abuse liability. The specific hypothesis behind the proposed research is that 6-heteroaromatic substituted naltrexamine derivatives may act as selective antagonist of MOR. Our hypothesis is based on the following facts: First, a primary series of ligands designed and synthesized as 6-heteroaromatic substituted naltrexamine derivatives have shown high selectivity to MOR. Second, some of these ligands showed strong antagonism to MOR. Third, molecular modeling studies have showed that these ligands may have specific interaction with the extracellular loop (EL) domains of the receptor, especially EL2 and EL3. It has been found out that EL3 of the MOR is very critical for the binding of MOR selective agonists. Site-directed mutagenesis studies have revealed that certain amino acid residues on EL3 may be essential for ligand (including agonist and antagonist) selectivity to MOR. Based on these observations, the focus of this proposal is the synthesis and evaluation of 6-heteroaromatic substituted naltrexamine derivatives as MOR non-peptide antagonists. The specific aims are: 1. Design and synthesis of novel compounds as mu opioid receptor antagonists based on lead compounds that have been identified from the primary synthesis and pharmacological screening. Homology modeling of MOR and the docking of naltrexone into the MOR model allowed the hypothetical identification of the unique amino acid residues in the binding pocket compared with corresponding (or conserved) loci in the delta and kappa opioid receptor antagonist binding sites. Two series of novel ligands satisfying the requirement of the MOR binding pocket by carrying the unique structural features to interact with EL3 (and/or EL2) of MOR have been designed, synthesized and tested. Two lead compounds have been identified for the preliminary studies. Several new series of ligands have been designed based on the chemical structures of these two lead compounds. The chemical synthesis routes have been proposed in order to materialize these new ligands. 2. Pharmacological evaluation of the compounds synthesized as selective MOR antagonist will be focused on in vitro radioligand-binding assays to determine affinity and selectivity, functional 35S-GTP[3S]-binding assay to determine efficacy, and in vivo behavioral tests. 3. Molecular modeling study- assisted site-directed mutagenesis studies will be conducted to verify the binding mode of the ligands and further characterize the antagonist binding site of the MOR for the next generation antagonist design. PUBLIC HEALTH RELEVANCE Our long-term goal is to develop highly selective non-peptide antagonists for the mu opioid receptor as chemical probes to study its structure and function relationship in order to assist the development of the potential analgesics without or with less addiction and abuse liability. The focus of this research program is to synthesize and test mu opioid receptor non-peptide antagonists carrying structural features to interact with the extracellular loop region of the receptor, which we anticipate will impart high selectivity for the mu opioid receptor. We believe such ligands will be useful as important pharmacological tools to study the structure-function relationship of the mu opioid receptor.