Novel selective alpha4beta2 nicotinic receptor antagonists for smoking cessation

描述（由申请人提供）：吸烟仍然是美国头号可避免的死亡原因。目前的治疗包括尼古丁替代、用安非他酮抑制多巴胺系统和用伐尼克兰部分激活4 2神经元烟碱乙酰胆碱受体（nAChR）都不是特别有效，无论治疗药物或疗法如何，复发率都接近80%。此外，最有效的药物伐尼克兰具有严重的精神副作用。显然，需要新的治疗方法。与香烟成瘾性最密切相关的nAChR是4 2 nAChR。该受体的激活是尼古丁奖赏的主要介质，并且选择性但低亲和力的4 2 nAChR拮抗剂DH E已被证明在啮齿动物模型中阻断尼古丁自我给药。目前，没有高亲和力和选择性的4 - 2拮抗剂可用于检查作为戒烟药物。从一个小分子组合库包含超过500万个单独的化合物，我们已经确定了选择性4 - 2 nAChR化合物。使用这些筛选命中沿着药物化学和分子建模，我们已经确定了两个先导化合物（2187.397和2187.202），一个在结合试验中具有非常高的亲和力（37 nM）和中等选择性（23倍），第二个具有优异的选择性（>500倍），但在4 2 nAChR的亲和力略低（114 nM）。这两种化合物都是4 - 2 nAChRs的拮抗剂，具有显着的体外选择性。在体外功能测定表明，202有400倍的选择性，在4 - 2超过3 - 4 nAChR。此外，202减弱尼古丁自我给药并阻断大鼠中尼古丁引发诱导的复吸。体外选择性和缺乏激动剂活性使我们的化合物与伐尼克兰不同，并且可能产生更少的副作用。在这个I期SBIR中，我们建议优化我们的先导化合物，以进一步提高亲和力，选择性和药物样性质。在具体目标1中，我们将基于当前的铅支架合成其他新的类似物。在具体目标2A中，我们将确定在4 2和3 4 nAChR的结合亲和力，使用[3 H]epibatidine结合从HEK细胞转染适当的受体产生的膜。在额外的nAChR的选择性将被确定的化合物表现出最高的亲和力4 - 2和最大的选择性对3 - 4 nAChR。在目标2B中，我们将确定在结合试验中显示高亲和力和选择性的化合物的功能选择性。拮抗剂活性和功能选择性将通过使用FlexStation在完整HEK细胞上测量配体诱导的膜电位变化来确定。最后，在目标2C中，我们将测量生物利用度和血脑屏障渗透率，以优化我们的先导化合物的药物样特性。这些研究将为随后的尼古丁奖赏模型体内疗效测定以及其他药代动力学研究做准备，这些研究将在随后的II期申请中完成。

DESCRIPTION (provided by applicant): Smoking remains the number one avoidable cause of death in the United States. Current therapies including nicotine replacement, inhibition of the dopamine system with bupropion, and partial activation of the 4 2 neuronal nicotinic acetylcholine receptor (nAChR) with varenicline have not been particularly effective, with relapse rates at nearly 80% regardless of the treatment drugs or therapies. Furthermore, varenicline, the most efficacious drug, has serious psychiatric side effects. Clearly new treatments are needed. The nAChR most closely associated with the addictive nature of cigarettes is the 4 2 nAChR. Activation of this receptor is the primary mediator of nicotine reward and the selective but low affinity 4 2 nAChR antagonist DH E has been demonstrated to block nicotine self-administration in rodent models. Currently there are no high affinity and selective 4 2 antagonists available to examine as smoking cessation medications. Starting from a small molecule combinatorial library containing over 5 million individual compounds, we have identified selective 4 2 nAChR compounds. Using these screening hits along with medicinal chemistry and molecular modeling, we have identified two lead compounds (2187.397 and 2187.202), one with very high affinity (37 nM) and moderate selectivity (23 fold) in binding assays, and a second with excellent selectivity (>500 fold) but slightly lower affinity (114nM) at the 4 2 nAChR. Both of these compounds are antagonists at 4 2 nAChRs with remarkable in vitro selectivity. In vitro functional assays showed that 202 has 400 fold selectivity at 4 2 over 3 4 nAChR. Furthermore, 202 attenuates nicotine self-administration and blocks nicotine prime-induced reinstatement in rats. Both in vitro selectivity and lack of agonist activity differentiateour compounds from varenicline and might produce fewer side effects. In this Phase I SBIR, we propose to optimize our lead compounds to further improve affinity, selectivity, and drug-like properties. In Specific Aim 1, we will synthesize additional novel analogs based upon the current lead scaffolds. In Specific Aim 2A we will determine binding affinities at 4 2 and 3 4 nAChR, using [3H]epibatidine to bind to membranes produced from HEK cells transfected with the appropriate receptors. Selectivity at additional nAChRs will be determined for the compounds exhibiting the highest affinity for 4 2 and the greatest selectivity against 3 4 nAChR. In Aim 2B we will determine the functional selectivity of compounds showing high affinity and selectivity in the binding assays. Antagonist activity and functional selectivity will be determined by measuring ligand-induced membrane potential changes using a FlexStation on intact HEK cells. Finally in Aim 2C we will measure bioavailability and blood brain barrier penetration to optimize drug-like properties of our lead compounds. These studies will be in preparation for subsequent in vivo efficacy determinations in nicotine reward models as well as additional pharmacokinetic studies, to be completed in a subsequent Phase II application.