Maximizing cancer synthetic lethality using dual PI-3K/PARP inhibitors

PARP抑制剂（PARPi）在BRCA 1/2肿瘤抑制因子缺陷的肿瘤中特别有效 基因，但在BRCA活性肿瘤中活性有限。有一个未满足的医疗需求，以开发有针对性的 本发明提供了将增强PARPi对BRCA 1/2野生型癌症的活性并增加化疗的治疗剂， 这些恶性肿瘤的放射敏感性。BRCA 1/2蛋白是同源的BRCA 1/2蛋白的重要组成部分。 重组（HR）双链DNA修复机制。PARPi的合成杀伤力来自于防止 癌细胞无法克服的HR DNA双链断裂（DSB）修复机制， 致命的DNA损伤PARPi对BRCA 1/2缺陷或其他DNA修复的细胞具有选择性毒性 在一些三阴性乳腺癌中发现的通路突变。最近的一份报告表明，PI-3 激酶（PI-3 K）抑制可损害BRCA 1/2表达，并可使BRCA活性癌对PARP敏感 抑制作用因此，我们在本提案中要测试的中心假设是，组合双PI-3 K PARP抑制剂（PI-3 Ki）/ PARP抑制剂将通过至少两种途径攻击癌细胞的DNA修复机制。 正交途径，并将PARPi临床活性扩展到BRCA 1/2和/或其他 DNA修复缺陷。我们的建议的一个创新组成部分是，我们已经在计算机上开发了第一个 同时抑制PI-3 K和PARP活性的小分子抑制性化学型（例如 SRX 3128;初步结果）。我们已经证明了SRX 3128的“概念证明”：1）增加细胞 2）在同一肿瘤中同时抑制靶DNA修复和PI-3 K 细胞和3）在正常细胞中显示出较低的毒性相比，个别抑制化学型在相当 针对目标的效力。我们的建议的意义在于我们有能力提供一个优化的 通过多重正交机制有效抑制DNA修复的有前景的单一抗癌剂 和化学-放射敏感性肿瘤细胞的DNA损伤剂。本提案将通过以下方式对这一方法进行评估： 实现以下目标，为第二阶段优化预期的双重抑制剂先导奠定基础 将化合物转化为临床候选物：目标（任务）#1。开发PI-3激酶/PARP双重抑制剂。目标（任务） #2.开发预测性计算PARP模型，用于设计化合物的计算机对接。 方法：改进我们的PARP模型的计算机模拟PARP-配体拟合参数，直到高PARP-对接/PARP- 实现了测定-抑制相关性。目标（任务）#3。确定双重PI-3 K/PARP的治疗窗 抑制作用方法：比较神经元癌干细胞与正常神经元干细胞的毒性 图4示出了当暴露于单一PARP抑制剂或PI-3 K抑制剂与双重PARP/PI-3 K抑制条件时，神经干细胞（NSC）的生长曲线。 本研究的意义在于将PARP抑制的范围大大扩展到BRCA-精通 癌的这种创新的方法使用两种不同的已证实的机制来攻击癌症， 挑战一药一靶的教条。

PARP inhibitors (PARPi) are particularly efficacious in tumors deficient in the BRCA1/2 tumor suppressor genes but of limited activity in BRCA competent tumors. There is an unmet medical need to develop targeted therapeutic agents which will augment PARPi activity for BRCA1/2 wild type cancers and to increase chemo- radiosensitivity in these malignancies. BRCA1/2 proteins are essential components of the homologous recombination (HR) double-strand DNA repair mechanism. PARPi's synthetic lethality derives from preventing the HR DNA double-strand break (DSB) repair mechanism which the cancer cell cannot overcome resulting in lethal DNA damage. PARPi are selectively toxic to cells with BRCA1/2 deficiencies or other DNA repair pathway mutations as found in some triple negative breast cancers. A recent report demonstrated that PI-3 kinase (PI-3K) inhibition impairs BRCA1/2 expression and can sensitize BRCA-proficient cancers to PARP inhibition. Hence, our central hypothesis to be tested in this proposal is that a combination dual PI-3K inhibitors (PI-3Ki)/ PARP inhibitor will attack the cancer cell’s DNA repair mechanisms via at least two orthogonal pathways and extend PARPi clinical activity beyond just those deficient in BRCA1/2 and/or other DNA repair defects. An innovative component of our proposal is that we have developed in silico the first small-molecule inhibitory chemotype which inhibits both PI-3K and PARP activity simultaneously (e.g. SRX3128; preliminary results). We have demonstrated “proof of concept” that SRX3128: 1) augments cell death following DNA damage 2) Inhibits both targets DNA repair and PI-3K simultaneously in the same tumor cell and 3) displays less toxicity in normal cells compared with individual inhibitory chemotypes at equivalent potency against targets. The significance of our proposal lies in our capacity to provide an optimizable promising single anticancer agent which will potently inhibit DNA repair via multiple orthogonal mechanisms and chemo-radiosensitive tumor cells to DNA damaging agents. This proposal will evaluate this approach by achieving the following aims setting the stage for phase II efforts to optimize the expected dual inhibitor lead compound(s) to a clinical candidate: Aim (Task) #1. Develop a dual PI-3 kinase/PARP inhibitor. Aim (Task) #2. Develop a predictive computational PARP model for the in silico docking of designed compounds. Approach: Improve in silico PARP-ligand fit parameters of our PARP model until a high PARP-docking/PARP- assay-inhibition correlation is achieved. Aim (Task) #3. Determine therapeutic window for dual PI-3K/PARP inhibition. Approach: Compare toxicity towards neuronal cancer stem cells versus normal neuronal stem cells (NSCs) when exposed to single PARP inhibitor or PI-3K inhibitor versus dual PARP/PI-3K inhibition conditions. The significance of this research is it will greatly expand the reach of PARP inhibition into BRCA-proficient cancers. This innovative approach attacks cancer using two distinct proven mechanisms with a single compound challenging the one-drug one-target dogma.