HDAC Inhibitors Inspired by Natural Products

描述（由申请人提供）：消化器官的癌症，如胃、结肠和肾脏是普遍存在的，并且很难治疗，因此为追求针对这些类型的恶性肿瘤的新药提供了令人信服的理由。组蛋白去乙酰化酶（hdac）是一个涉及染色质重塑和表观遗传事件的酶家族，已经引起了相当大的兴趣。在这个领域已经有相当多的工作，主要集中在羟肟酸类，其中第一个已被批准用于治疗皮肤t细胞淋巴瘤。HDAC同工酶之间的低选择性被认为是当前临床使用的HDAC抑制剂的毒性的基础。具有优越活性的新型HDAC抑制剂可能会显著影响该靶点在癌症中的疗效。我们有兴趣开发一种全新的HDAC抑制剂，具有更高的选择性水平。这些新的抑制剂是基于一种天然产物化学型，即tropolone系统。几个世纪以来，台湾松木（Chamaecyparis台湾）和日本松木（Chamaecyparis钝角）的木材和提取物在日本和中国都很珍贵。这种树的提取物（桧木油）被认为具有抗菌和抗增殖活性，目前被用于许多局部用药和化妆品中。在20世纪40年代早期，人们对这些提取物的成分进行了研究，发现了一种不寻常的tropoloid，称为扁柏酚（也称为山茱萸素），它被证明对大部分生物活性负责。天然存在的tropolones（如thujaplicin）因其通过螯合1-羟基酮与金属离子相互作用的能力而被认可，并且可以形成一个多功能平台，用于发现特异性靶向结合金属离子（如金属酶中的金属离子）的药物。事实上，我们已经证明了tropolone类似物能够抑制HDAC-2。在这个R21应用中，我们的目的是研究这种非苯芳香族化合物作为发现新的HDAC抑制剂的良好先导化合物的潜力。我们的初步分析表明，该类的独特结构特征为纳入高水平的效力和选择性提供了机会。我们的目标是利用R21机制来确定开发以tropol酮为基础的先导系列作为HDAC抑制剂的可行性。第一个特定目标将描述各种差异取代的tropolones的合成，总共约40种，将在第二个目标中使用酶和基于细胞的测定进行评估。对前5种抑制剂也将进行初步的代谢稳定性研究。在第三个目标中，将尝试使HDAC与铅抑制剂配合物结晶。这些研究将最终支持基于结构的药物设计工作，因为我们将向前推进先导优化。实现R21应用程序中概述的目标将使我们对进一步化合物开发至关重要的关键合成，结构和生化方面具有高水平的控制。

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.