HDAC Inhibitors Inspired by Natural Products

描述(申请人提供)：胃、结肠癌和肾癌等消化器官的癌症非常普遍，可能非常难以治疗，因此为寻求针对这些类型的恶性肿瘤的新药物提供了令人信服的理由。新出现的靶点是组蛋白脱乙酰酶(HDACs)，这是一个参与染色质重塑和表观遗传事件的酶家族。在这一领域已经有了相当多的工作，主要集中在异羟甲酸酯类，其中第一种已被批准用于皮肤T细胞淋巴瘤的治疗。HDAC同工酶之间较差的选择性被认为是当前HDAC抑制剂临床使用的大部分毒性的基础。具有优异活性的新的HDAC抑制剂可能会显著影响该靶点在癌症中的疗效。我们有兴趣开发一类全新的具有更高选择性的HDAC抑制剂。这些新的抑制剂是基于一种天然的产物化学型--特罗普隆系统。几个世纪以来，黄连(Chamaecyparis Taiwanesis)和日本黄木(Chamaecyparis Obtuse)的木材和提取物一直受到日本和中国的珍视。树的提取物(胡桃油)具有抗菌和抗增殖活性，目前被用于许多外用药物和化妆品。20世纪40年代初，人们对这些提取物的组成进行了研究，结果发现了一种不寻常的对旋体，名为hinokitiol(也称为侧柏蛋白)，它被证明是大部分生物活性的原因。人们已经认识到，天然生成的胡萝卜苷通过1-羟基酮的螯合作用与金属离子相互作用，并可以形成一个通用的平台，用于发现专门针对结合的金属离子的试剂，如金属酶中的金属离子。事实上，我们已经证明了特罗普隆类似物能够抑制HDAC-2。在R21的应用中，我们旨在研究这种非苯基芳香族化合物作为一种很好的先导化合物的潜力，以发现新的HDAC抑制剂。我们的初步分析表明，这一类的独特结构特征提供了将高水平的效力和选择性结合在一起的机会。我们的目标是利用R21机制来确定开发以特罗洛酮为基础的铅系列作为HDAC抑制剂的可行性。第一个具体目标将描述各种不同取代的特罗罗酮的合成，总共约40个，将在第二个目标中使用酶和基于细胞的分析进行评估。还将对排名前五位的抑制剂进行初步代谢稳定性研究。在第三个目标中，将尝试使HDAC与铅缓蚀剂形成络合物。随着我们推进先导优化，这些研究最终将支持基于结构的药物设计努力。实现这一R21应用中概述的目标将使我们能够高度控制对进一步化合物开发至关重要的关键合成、结构和生化方面。 公共卫生相关性：胃癌、结肠癌和肾癌是常见的恶性肿瘤，需要现代疗法。组蛋白脱乙酰酶抑制剂已被证明是有效的抗增殖剂，但仍需进一步开发选择性HDAC抑制剂。在这项提案中，我们的目标是评估一种天然产品特罗隆支架形成一类新型HDAC抑制剂的潜力。以天然产物为先导平台，我们将设计、合成和评估类似物对消化系癌细胞的选择性和效力。

DESCRIPTION (provided by applicant): Cancers of the digestive organs such as the stomach, colon and the kidney are prevalent and can be very difficult to treat, thus providing a compelling rationale for the pursuit of new agents that target these types of malignancies. Emerging targets that have generated considerable interest are histone deacetylases (HDACs), a family of enzymes that is involved in chromatin remodeling and epigenetic events. There has already been considerable work in this area, largely focusing on the hydroxamate class, the first of which has gained approval for the treatment of cutaneous T-cell lymphoma. Poor selectivity between HDAC isozymes is believed to underlie much of the toxicity associated with the clinical use of current HDAC inhibitors. New HDAC inhibitors with superior activities could significantly impact the efficacy of this target in cancer. We are interested in developing a completely novel class of HDAC inhibitors with enhanced levels of selectivity. These new inhibitors are based on a natural product chemotype, the tropolone system. For centuries, the wood and extracts from taiwanhinoki (Chamaecyparis taiwanesis) and Japanese hinoki (Chamaecyparis obtuse) have been prized in Japan and China. The extracts of the tree (hinoki oil) have been valued for antibacterial and antiproliferative activity and are currently used in numerous topical agents and cosmetics. The composition of these extracts was studied in the early 1940s, leading to the identification of an unusual tropolonoid termed hinokitiol (also known as thujaplicin) that was shown to be responsible for much of the biological activity. Naturally occurring tropolones such as thujaplicin have been recognized for their ability to interact with metal ions through chelation of the 1-hydroxy ketone and could form a versatile platform for the discovery of agents that specifically target bound metal ions such as those in metalloenzymes. In fact, we have already demonstrated that tropolone analogs are capable of inhibiting HDAC-2. In this R21 application, we aim to investigate the potential of this non-benzenoid aromatic to serve as a good lead compound for the discovery of new inhibitors of HDAC. Our preliminary analysis suggests that the unique structural features of this class offer opportunities to incorporate high levels of potency and selectivity. It is our aim to use the R21 mechanism to establish the feasibility of developing a tropolone-based lead series as HDAC inhibitors. The first specific aim will describe the synthesis of a variety of differentially substituted tropolones, approximately 40 in total, which will be evaluated in the second aim using enzymatic and cell- based assays. Preliminary metabolic stability studies will also be conducted on the top five inhibitors. In the third aim, attempts will be made to crystallize HDAC in complex with a lead inhibitor. These studies will ultimately support a structure-based drug design effort as we move forward with lead optimization. Realization of the goals outlined in this R21 application would position us with high levels of control over the key synthetic, structural and biochemical facets critical for further compound development. PUBLIC HEALTH RELEVANCE: Stomach, colon and kidney cancers are common malignancies needing modern therapeutics. Inhibitors of histone deacetylase enzymes have been shown to function as effective antiproliferative agents but further development of selective HDAC inhibitors is still needed. In this proposal we aim to evaluate the potential of a natural product tropolone scaffold to form a novel class of HDAC inhibitors. Using the natural product as a lead platform, we will design, synthesize and evaluate analogs for selectivity and potency against digestive cancer cell lines.