Design of Orally Bioavailable IAP Antagonists for Cancer Treatment

描述（由申请人提供）：凋亡蛋白抑制剂（IAPs）是一类关键的凋亡调节因子。在这些IAP蛋白中，细胞IAP-1 （cIAP-1）和细胞IAP-2 （cIAP-2）在死亡受体介导的凋亡调控中起关键作用，X-linked IAP （XIAP）是死亡受体介导和线粒体介导的凋亡途径的中心调节剂。由于其作为细胞凋亡调节因子的核心作用，XIAP和cIAP-1/2是有希望的癌症治疗靶点。Smac是这些IAP蛋白的内源性拮抗剂，并通过其AVPI四肽结合基序与它们相互作用。近年来，研究人员致力于设计和开发被称为Smac模拟物的小分子，它模拟AVPI结合基序并作为IAP蛋白的拮抗剂。Smac模拟物不仅能够使癌细胞对其他治疗药物诱导的凋亡敏感，而且在体外和体内对不同肿瘤类型的一部分癌细胞系的诱导凋亡作为单一药物是有效的。Smac模拟物作为一类新的抗癌药物被认为具有很大的发展潜力。在这个R01竞争更新中，我们建议评估一类新的有效的，口服活性的，有前途的Smac模拟物作为治疗人类癌症的新疗法。我们的初步数据表明，我们有希望的先导化合物与XIAP和cIAP-1/2在低纳摩尔范围内结合，有效诱导癌细胞凋亡，对正常细胞具有最小的毒性，其细胞作用机制与靶向IAP蛋白诱导细胞凋亡高度一致。我们的一种先导化合物作为口服药物在诱导异种移植肿瘤组织凋亡和抑制MDA- MB-231异种移植模型中的肿瘤生长方面非常有效，同时在高剂量下对动物没有毒性。我们在这个项目中的最终目标是开发一种高效的，口服活性的Smac模拟物，作为治疗人类癌症的新疗法。为了最大限度地实现我们的最终目标，同时最有效地利用资源，我们将进行以下具体目标：目标1：测定体外微粒体和血浆稳定性，动物毒性和药代动力学，以及几种最有希望的先导化合物在多种人类癌症异种移植模型中的抗肿瘤活性。目的2：阐明几种最有前途的Smac模拟物诱导癌细胞凋亡的细胞机制。目标3：基于结构的设计和合成基于最有希望的新类似物，进一步定义这类有前途的Smac模拟物的结构-活性关系，并为体内研究确定更多新的和更好的类似物。Aim 4：对于Aim 3中获得的新类似物，测定其与IAP蛋白的结合亲和力和特异性，其拮抗XIAP的活性，其在癌细胞系中的活性以及对正常细胞的选择性。我们的初步数据为我们的中心假设、研究设计和策略提供了强有力的支持，为本项目的成功奠定了坚实的基础。如果成功实施，该项目将至少带来1-2种有效的、特性良好的、高度优化的、口服活性的Smac模拟物进入临床前开发阶段，作为一种新的抗癌疗法，用于治疗多种人类癌症。公共卫生相关性：癌症是美国第二大死亡原因。迫切需要更有效的治疗方法来改善数百万癌症患者的预后。本研究项目旨在设计、合成和开发一类新的小分子抗癌药物，用于治疗人类癌症，包括但不限于乳腺癌和前列腺癌。

DESCRIPTION (provided by applicant): Inhibitor of apoptosis proteins (IAPs) are a class of key apoptosis regulators. Among these IAP proteins, cellular IAP-1 (cIAP-1) and cellular IAP-2 (cIAP-2) play critical roles in the regulation of death-receptor-mediated apoptosis, and X-linked IAP (XIAP) is a central regulator of both death-receptor-mediated and mitochondria-mediated apoptosis pathways. Because of their central role as apoptosis regulators, XIAP and cIAP-1/2 are promising cancer therapeutic targets. Smac is an endogenous antagonist of these IAP proteins and interacts with them via its AVPI tetrapeptide binding motif. In recent years, intense research efforts have been devoted to the design and development of small molecules known as Smac mimetics, which mimic the AVPI binding motif and function as antagonists of IAP proteins. Smac mimetics are not only capable of sensitizing cancer cells to induction of apoptosis by other therapeutic agents but also are effective as single agents in induction of apoptosis in vitro and in vivo in a subset of cancer cell lines of diverse tumor types. Smac mimetics are considered to have great potential for development as a new class of anticancer drugs. In this R01 competing renewal, we propose to evaluate a novel class of potent, orally active, promising Smac mimetics as new therapies for the treatment of human cancer. Our preliminary data have shown that our promising lead compounds bind to XIAP and cIAP-1/2 with affinities in the low nanomolar range, effectively induce apoptosis in cancer cells, possess minimal toxicity to normal cells and have a cellular mechanism of action highly consistent with targeting IAP proteins for apoptosis induction. One of our lead compounds is highly effective as an oral agent in induction of apoptosis in xenograft tumor tissues and in inhibition of tumor growth in the MDA- MB-231 xenograft model, while showing no toxicity to animals at highly efficacious doses. Our ultimate goal in this project is to develop a highly potent, orally active Smac mimetic as a new therapy for the treatment of human cancer. To maximize the probability of achieving our ultimate goal while using resources most efficiently, we will carry out the following specific Aims: Aim 1: Determination of the microsomal and plasma stability in vitro, toxicity and pharmacokinetics in animals, and antitumor activity in multiple xenograft models of human cancer for several of the most promising lead compounds. Aim 2: Elucidation, for several of the most promising Smac mimetics, of the cellular mechanism of action for apoptosis induction in cancer cells. Aim 3: Structure-based design and synthesis of new analogues based upon the most promising leads to further define the structure-activity relationship for this class of promising Smac mimetics and to identify additional new and superior analogues for in vivo studies. Aim 4: For the new analogues obtained in Aim 3, determination of the binding affinities and specificity to IAP proteins, their activity in antagonizing XIAP, their activity in cancer cell lines and selectivity over normal cells. Our preliminary data provide strong support for our central hypothesis, research design and strategy and have laid a solid foundation for the success of this project. Successfully carried out, this project will bring, at a minimum, 1-2 potent, well-characterized, highly optimized, orally active Smac mimetics into advanced preclinical development as a new class of anticancer therapy for the treatment of many types of human cancer. PUBLIC HEALTH RELEVANCE: Cancer is the second leading cause of death in the United State of America. More effective treatments are urgently needed to improve the outcome of millions of cancer patients. This research project aims at the design, synthesis and development of a new class of small-molecule anti-cancer drugs for the treatment of human cancer, including but not limited to breast cancer and prostate cancer.