Design of the First Mdm2 Targeting PROTACs for treatment of p53 Mutant or Deficient Cancers

项目摘要/摘要 我们的建议集中在开发新型MDM2靶向蛋白水解靶向嵌合体(PROTACs) 有效地降解p53突变和缺陷癌细胞中的MDM2，并有望靶向p53- MDM2的独立功能。我们的先导化合物与高亲和力结合，降解MDM2，杀死癌细胞 缺乏功能性的p53，在体内是有效的。我们还在体内证明了安全性和耐受性， 在小鼠药代动力学研究中的合成可控性、代谢稳定性和适宜的体内暴露 活体疗效评价。肿瘤抑制因子P53，一种转录因子，在预防中起着至关重要的作用 人类癌症的风险。在没有细胞应激的情况下，由于其结合，P53蛋白保持在低水平 MDM2是一种E3泛素连接酶。然而，有一半的人类癌症通过突变或缺失使P53失活。 为了测试缺乏p53的癌细胞是否需要MDM2的生存，我们诱导性地删除了初级 小鼠P53阴性淋巴瘤和肉瘤细胞。MDM2缺失导致P53基因缺失的体内外细胞凋亡 癌症，显著减轻了肿瘤负担，提高了生存效益。我们和其他人已经报道了 MDM2通过结合和调节其他蛋白质，如p53家族，具有不依赖于p53的功能 Mre11-Rad50-Nbs1 DNA断裂修复复合体中的成员、p73和Nbs1。P73有一个同源的N-末端 反式激活结构域到结合在MDM2上相同位置的P53。此外，与p53不同的是，p73很少 在人类癌症中失活。由于MDM2-P53抑制剂对P53失活的肿瘤不起作用，我们 采用PROTAC方法，并提供初步数据以确认他们杀死突变或缺陷的p53的能力 癌细胞。我们的假设是，通过MDM2靶向的PROTAC降解MDM2将杀死癌症 通过激活MDM2的不依赖于P53的活性来突变或删除P53。我们将用两个例子来检验这一假设 明确的目标。目标1将专注于扩大我们的先导MDM2靶向化合物的特征，并 在体内异种移植模型中对这些进行评估。目标2将是对两个导致 P53突变型和缺失型癌症。这些目标的目标是拥有一个具有特色的、有效的和强大的MDM2 PROTAC用于P53失活癌症治疗的临床评价。

Project Summary / Abstract Our proposal focuses on the development of novel Mdm2-targeted proteolysis targeting chimeras (PROTACs) that efficiently degrade Mdm2 in p53 mutant and deficient cancer cells and are expected to target p53- independent functions of Mdm2. Our lead compounds bind with high affinity, degrade Mdm2, kill cancer cells that lack functional p53, and are efficacious in vivo. We have also demonstrated safety and tolerability in vivo, synthetic tractability, metabolic stability, and suitable in vivo exposure in mouse pharmacokinetic studies for in vivo efficacy evaluation. The tumor suppressor p53, a transcription factor, has an essential role in the prevention of human cancer. In the absence of cellular stress, the p53 protein is maintained at low levels due to its binding to Mdm2, an E3 ubiquitin ligase. However, half of all human cancers have inactivated p53 by mutation or deletion. To test if Mdm2 is required for the survival of cancer cells that lack p53 we inducibly deleted Mdm2 in primary murine p53-null lymphoma and sarcoma cells. Mdm2 loss resulted in apoptosis in vitro and in vivo in p53-null cancers, with significantly reduced tumor burden and increased survival benefit. We and others have reported that Mdm2 has p53-independent functions by binding and regulating other proteins, such as the p53 family member, p73, and Nbs1 in the Mre11-Rad50-Nbs1 DNA break repair complex. p73 has a homologous N-terminal transactivation domain to p53 which binds in the same site on Mdm2. Additionally, unlike p53, p73 is rarely inactivated in human cancers. Since Mdm2-p53 inhibitors are not responsive to tumors with inactivated p53, we pursued a PROTAC approach and provide preliminary data to confirm their ability to kill p53 mutated or deficient cancer cells. Our hypothesis is that the degradation of Mdm2 via Mdm2-targeted PROTACs will kill cancers with mutant or deleted p53 by activating the p53-independent activities of Mdm2. We will test this hypothesis with two Specific Aims. Aim 1 will focus on expanding the characterization of our lead Mdm2 targeting compounds and evaluate these in in vivo xenograft models. Aim 2 will be lead optimization of two Mdm2 PROTACs that killed p53 mutant and deleted cancers. The goal of these aims is to have a characterized, effective, and potent Mdm2 PROTAC for clinical evaluation for the treatment of p53-inactivated cancers.