大麻素CB1受体别构拮抗剂及其治疗尼古丁成瘾性作用研究

Tobacco smoking is the largest cause of avoidable death and disease in the world and is now viewed as a complex bio-psychosocial problem for which effective pharmacological treatments are needed.Several approaches for cessation are available but they either lack high levels of efficacy or possess significant side-effects and consequently, there is a compelling need for more effective and safer medications to aid smokers in achieving long-term abstinence. The cannabinoid CB1 receptor has been shown to play a critical role in smoking and nicotine addiction. Pre-clinical and clinical studies have clearly shown that antagonism of the CB1 receptor holds considerable promise in treating a range of diseases and adverse health conditions including smoking and nicotine addiction. Unfortunately, side effects observed in humans associated with CB1 receptor antagonist/inverse agonist use, including anxiety and depression, have severely dampened the outlook for their clinical application. Thus, an alternate approach is needed to enable alternative modulation of the CB1 receptor, which may still hold potential as a viable drug target. In this application we propose to target the allosteric site of the CB1 receptor and develop negative allosteric modulators (or allosteric antagonists) for the CB1 receptor that antagonize CB1 agonists but do not have the inverse agonist effects commonly associated with CB1 antagonists. The allosteric modulators proposed herein, once synthesized, will be evaluated in a series of functional assays to determine their potency and efficacy (Emax) in the Ca2+ assay, inverse agonist activity and antagonist potency in the GTPgS assay, CB1 receptor selectivity against select targets, bioavailability and ADME studies such as aqueous solubility and blood-brain barrier penetration. Given the urgent need for smoking cessation medications, these CB1 receptor allosteric antagonists represent a promising alternative to modulate the CB1 receptor function and may serve as much needed tools to identify more effective treatment strategies for smoking and nicotine addiction.

烟草危害是当今世界最严重的公共卫生问题之一，现有的戒烟药物疗效有限且有较大副作用，亟需寻找并开发新型的戒烟特效药物。大麻素CB1受体与尼古丁成瘾具有紧密联系，其拮抗剂也被证明对戒烟有显著的作用，是个很好的特异性药物靶标。由于CB1正位拮抗剂会引发包括焦虑和抑郁等副反应，因此本项目探究作用于CB1受体别构调解位点的别构拮抗剂。CB1受体别构拮抗剂的研究刚刚起步,目前只有两个系列的化合物被报道，而它们的生物活性较低。本申请将设计合成一系列衍生物，在钙动员和GTPgS实验中测试它们的生物活性并确定其不具有反向激动效应，测试它们在包括CB2，GPR55，TRPV1在内的其它"大麻"受体上的作用以确定其对CB1受体的选择性，最后进行初步的成药性研究。这一系列研究的顺利完成将会大大增加这些化合物的活性及其它药物特性，为证实CB1别构拮抗剂作为戒烟药物提供极具价值的工具。

鉴于烟草对健康的巨大危害及现有戒烟药物的有限疗效和较大副作用，研究开发新型戒烟药物刻不容缓。本课题基于大麻素CB1受体正位拮抗剂对戒烟具有显著作用，但会引发包括焦虑和抑郁等副反应，拟开发作用于CB1受体别构调解位点的别构拮抗剂。本课题组设计合成了已报道CB1受体别构拮抗剂PSNCBAM-1和ORG27569的一系列衍生物，深入研究了他们的构效关系，并针对它们生物活性较低或代谢稳定性较差的缺陷进行了针对性的结构改良。所有目标化合物都在钙动员和GTPgS实验中对它们的对激动剂CP55940的拮抗活性、反向激动效应、及对CB2受体等的选择性进行了测试，进行了初步的成药性研究，并开展了体内实验。研究结果表明，ORG27569中的哌啶基和氯原子可分别被二烷基胺和氟原子取代而保持化合物活性不变。而PSNCBAM-1结构中的砒咯基被证明为生物活性非必需基团，而砒啶基也可被苯基或取代苯基所取代，所得衍生物都具有相近甚至更高的生物活性。在钙动员或GTPgS实验中，这些衍生物剂量依赖性地降低了CB1受体激动剂CP55940曲线的顶端（Emax），证明其别构作用机理。与ORG27569和PSNCBAM-1相似，这两个系列的化合物都在CB2受体没有明显活性，显示了良好的CB1受体选择性。其中，4-氟苯基与PSNCBAM-1的体外活性相近，但在大鼠肝微粒体内的代谢稳定性大大提高，因而在阻断大鼠可卡因复吸的动物实验中显示了更好体内活性。此外，砒啶基也可以被比如砒咯基的五元杂环所取代，而活性不受影响，而放射配体结合实验表明，这些化合物可以与CB1受体结合并改变高亲和力和低亲和力受体之间的比率。通过本课题的研究，CB1别构拮抗剂的生物活性、成药性、体内活性等都获得了较大提高，为将来开发以CB1别构拮抗剂为基础的戒烟药物打下了坚实的基础。