Exploiting Mutant PPM1D-induced Metabolic Defects with Nanoparticle Encapsulated NAMPT Inhibitors

项目总结 弥漫性固有桥脑胶质瘤(DIPG)是导致儿童癌症死亡的主要原因，其发病率高达1%。 五年存活率。这种癌症的致命性源于缺乏有效的治疗选择，以及 虽然放射治疗是目前的治疗标准，但它可以被认为是最好的姑息性治疗。它很难使用 手术或化疗，因为这些肿瘤形成在血脑屏障(BBB)内，在脑桥区域 脑干。因此，人们一直致力于了解DIPG的分子图谱， 它可以靶向在这些肿瘤中选择性地杀伤肿瘤细胞。最近，宾德拉实验室发布了 一项新发现，截断PPM1D突变可导致全球CpG 岛状高甲基化表型(CIMP)样状态。这种突变导致一系列不同的细胞 表型，包括代谢缺陷，我们认为可以利用这些缺陷来获得治疗收益。为此， 我们发现突变的PPM1D诱导NAD+生物合成基因NAPRT的启动子超甲基化。 产生NAD+所需的重要酶。我们的团队证明了突变体PPM1D诱导的NAPRT 沉默使人对一类针对NAMPT的药物具有极高的敏感性，NAMPT是另一种关键的NAD+酶。这 这项研究最近发表在《自然通讯》(Fons等人，2019年)上。基于这些新的发现，以及 迫切需要新的DIPG疗法，我们建议开发NAMPT抑制剂(NAMPTi的)来治疗 PPM1D突变株DIPG的治疗。血脑屏障(BBB)渗透剂NAMPTI已经开发出来， 然而，在临床试验中，它们的成功受到骨髓中剂量限制毒性的限制。 还有视网膜。为了解决这些问题，这项提议旨在开发纳米颗粒包裹的NAMPT 用于直接输送到肿瘤微环境的抑制剂(NAMPTi-NPs)，并使用 体外和体内患者衍生模型。我的建议将通过两个目标来实现这一目标：在目标1中，我们 将创造和优化具有高药物包封率、NAMPTi-NP在体内的持续保留率的纳米粒 靶点，并在NHA等基因细胞模型和CCLE细胞系中证明了有效的细胞杀伤作用。目标2将 通过体内模型显示NAMPTi-NP的临床可行性，包括对游离药物的毒性筛选 NAMPTi和NAMPTi-NP，以及这些药物在大脑中的生物分布。最后，我们将展示 NAMPTi-NP治疗PPM1D突变肿瘤的疗效总之，这项工作将 利用全面和严格的基于基准的方法，结合计算和 生物工程方法，开发一种治疗DIPG的新方法。我的研究将成为关键的证据- 寻求建立一种全新的以NP为基础的战略，针对DIPG中的一个关键代谢缺陷。如果 如果成功，我们的方法未来可以应用于许多其他小分子和脑瘤。

PROJECT SUMMARY Diffuse Intrinsic Pontine Glioma (DIPG) is a leading cause of death from pediatric cancer, with an abysmal <1% five-year survival rate. The lethal nature of this cancer stems from the lack of effective treatment options, and while radiotherapy is the current standard of care, it can be considered is palliative at best. It is difficult to use surgery or chemotherapy as these tumors form within the blood brain barrier (BBB), in the pons region of the brainstem. Therefore, significant effort has been directed towards understanding the molecular profiles of DIPG, which can be targeted for selective tumor cell killing in these tumors. Recently, the Bindra laboratory published a novel discovery that truncating mutations in PPM1D, which are commonly found in DIPG, induce a global CpG Island hypermethylation phenotype (CIMP)-like state. This mutation leads to a diverse range of cellular phenotypes, including metabolic defects which we believe can be exploited for a therapeutic gain. To this end, we found that mutant PPM1D induces promoter hypermethylation in the NAD+ biosynthesis gene NAPRT, an important enzyme required to produce NAD+. Our group demonstrated that mutant PPM1D-induced NAPRT silencing confers exquisite sensitivity to a class of drugs which target NAMPT, another key NAD+ enzyme. This work was recently published in Nature Communications (Fons et al., 2019). Based on these novel findings, and the desperate need for new DIPG therapies, we propose to develop NAMPT inhibitors (NAMPTi’s) for the treatment of PPM1D-mutant DIPG. Blood-brain barrier (BBB)-penetrant NAMPTi’s have been developed and tested in clinical trials, however, their success has been limited by dose-limiting toxicities in the bone marrow and retina. To address these liabilities, this proposal aims to develop nanoparticle-encapsulated NAMPT inhibitors (NAMPTi-NPs) for direct delivery into the tumor microenvironment, and to validate them using in vitro and in vivo patient-derived models. My proposal will accomplish this goal with two aims: In Aim 1, we will create and optimize NPs that have high drug encapsulation efficiency, sustained retention of NAMPTi-NP in target sites, and demonstrate effective cell killing in NHA isogenic cell models and CCLE cell lines. Aim 2 will show the clinical feasibility of NAMPTi-NP via in vivo modeling that will encompass toxicity screens of free drug NAMPTi and NAMPTi-NP, as well as the biodistribution of these drugs within the brain. Lastly, we will show efficacy through reduction in size of PPM1D-mutant tumors treated with NAMPTi-NP. Altogether, this work will utilize a comprehensive and rigorous bench-based approach, coupled with computational and bioengineering methods, to develop a novel treatment for DIPG. My studies will serve as a critical proof-of- concept that seeks to establish an entirely new NP-based strategy targeting a key metabolic defect in DIPG. If successful, our approach can be applied to many other small molecules and brain tumors in the future.