Analgesics targeting truncated 6transmembrane exon 11 variants of MOR-1 (6TM-E11)

描述(申请人提供)：mU阿片受体(MOR-1)基因(OPRM1)的大量剪接变体可以根据负责它们产生的启动子分为两组。第一启动子与外显子1相关，并产生大量传统的7跨膜区受体。第二个启动子与外显子11相关，位于外显子1上游约30kb，产生多个截短的6个跨膜结构域。利用我们实验室合成的一种新的放射性配基125I-BNtxA，我们最近报道了一个新的与外显子11相关的结合位点，该结合位点在三重KO小鼠中缺失了所有包含外显子1的MOR-1剪接变异体以及Delta和kappa1受体，该结合位点在外显子11 KO小鼠中缺失。IBNtxA是一种有效的止痛剂，其效力是吗啡的10倍。这种止痛作用在三重KO小鼠中持续存在，但在外显子11 KO小鼠中消失。尽管IBNtxA有很强的止痛作用，但它缺乏呼吸抑制、严重便秘、身体依赖或奖励。它对吗啡没有交叉耐受性，可用于吗啡依赖小鼠，而不会减少其自身的镇痛作用或戒断沉淀。因此，这种配体通过靶向Mu阿片受体MOR-1(6TM/E11)的截短6个跨膜域剪接变体，避免了传统阿片类药物的许多有问题的副作用。我建议用它作为先导化合物来设计一个阿片类止痛药的库。尽管它具有良好的药理作用，但与传统药物相比，其对新靶点的选择性仅是温和的，而且可以提高。本项目的目标是获得选择性和有效的6TM/E11镇痛剂，建立SAR并产生有用的生化探针来研究这些部位的生物化学/分子药理学。类似物将包括基于IBNtxA的4，5-环氧吗啉支架和吗啡支架(缺少醚氧桥环A和C的4，5-环氧吗啉)的化合物。初步数据表明，阿片剂6位上的芳基氨基与芳基3位或4位上的碘结合可增强6TM/E11位点的亲和力。我们将探索具有不同取代基的4，5-环氧吗啉支架6位周围的化学空间。其他化合物包括叔氮原子上的取代基，14-OH，以及使用在7，8位之间具有双键的芳酰胺基-环氧吗烷。最后，还将合成芳基氨基吗啡。所有合成的化合物将使用体外放射配基结合分析来表征选择性，有用的化合物将在体内进行评估。

DESCRIPTION (provided by applicant): The vast array of splice variants of mu opioid receptors (MOR-1) gene (Oprm1) can be divided into two groups based upon the promoters responsible for their generation. The primary promoter is associated with exon 1 and generates a large number of traditional 7 transmembrane domain receptors. The second promoter, associated with exon 11, located approximately 30 kb upstream of exon 1, generates a number of truncated, 6 transmembrane domains. Using a novel radioligand 125I-BNtxA synthesized in our laboratories, we recently reported a novel exon 11-associated binding site in a triple KO mouse lacking all exon 1- containing MOR-1 splice variants as well as delta and kappa1 receptors, that was lost in the exon 11 KO mice. IBNtxA is an effective analgesic, with a potency 10-fold greater than morphine. This analgesia persists in the triple KO mice, but is lost in the exon 11 KO mice. Despite it potent analgesic actions, IBNtxA lacks respiratory depression, significant constipation, physical dependence or reward. It shows no cross tolerance to morphine and can be given to morphine-dependent mice without a decrease in its own analgesic actions or the precipitation of withdrawal. Thus, this ligand avoids many of the problematic side-effects seen with traditional opioids by targeting truncated 6 transmembrane domain splice variants of the mu opioid receptor MOR-1(6TM/E11). I propose to use it as a lead compound to design a library of opioid analgesics. In spite of its favorable pharmacology, its selectivity for the new target over the traditional ones is only modest and can be improved. The goal of this project is to obtain selective and potent 6TM/E11 analgesics, establish an SAR and generate useful biochemical probes to study the biochemistry/molecular pharmacology of these sites. Analogs will include compounds based upon the 4,5-epoxymorphinan scaffold of IBNtxA and the morphinan scaffold (4,5-epoxymorphinans lacking the ethereal oxygen bridging rings A and C). Preliminary data suggests that an aryl amido at the 6-position of the opiate coupled with an iodine at the 3 or 4 position of the aryl enhances the affinity for the 6TM/E11 site. We will explore the chemical space around the 6 position of the 4,5-epoxymorphinan scaffold with various substituents. Other compounds include substituents on the tertiary nitrogen atom, the14-OH, and using aryl amido- epoxymorphinans with a double bond between 7,8 position. Finally, aryl amido-morphinans will also be synthesized. All synthesized compounds will be characterized for selectivity using in vitro radioligand binding assays and useful compounds will be evaluated in vivo.