CDK7 inhibitors as a new strategy to overcome treatment resistance in ER+ metastatic breast cancer

项目摘要 大多数乳腺癌是雌激素受体阳性（ER+），ER+乳腺癌是主要的乳腺癌。 导致乳腺癌死亡的原因。尽管辅助内分泌治疗被广泛采用， 对于ER+乳腺癌，几乎所有ER+转移性疾病患者最终都会对 内分泌治疗人们提出了许多内分泌抵抗的机制，但大多数情况下， 主要基于临床前证据。最近，我们的小组和其他一些小组发现， 雌激素受体（ER）配体结合域（LBD）突变是最普遍的基因组机制， 在ER+转移性乳腺癌患者中发现内分泌耐药。这些突变与 ER+转移性乳腺癌的总生存率降低。将CDK 4/6抑制剂（CDK 4/6 i）添加至 内分泌治疗已被证明可以改善转移性ER+乳腺癌患者的无进展生存期， 癌症，但尚未显示出改善总体生存率。尽管取得了这一进展， 疾病总是对这种联合治疗产生耐药性，用尽其他化疗选择， 最终死于疾病。迫切需要开发新的治疗策略来克服 对内分泌治疗和CDK 4/6 i的抵抗。 我们的初步数据表明，选择性抑制CDK 7可以克服内分泌抵抗， 由ER突变驱动的耐药性和对CDK 4/6 i的耐药性。CDK 7在转录和细胞凋亡中起关键作用， 周期调节SY 1365是一种选择性CDK 7抑制剂，处于癌症临床开发的早期阶段 治疗本研究旨在全面研究SY 1365作为单药的活性， 与氟维司群联合治疗ER突变型内分泌耐药和CDK 4/6 i耐药ER+ 转移性乳腺癌我们将研究CDK 7抑制发挥抗肿瘤活性的机制 并且克服了由ER突变驱动的对内分泌治疗的抗性和对CDK 4/6 i的抗性。 由于CDK 7磷酸化RNA聚合酶II，也作为CDK激活激酶发挥作用，我们将测试 SY 1365对新生RNA和mRNA转录、CDK 2磷酸化和细胞周期进程的影响 在ER+乳腺癌模型中。我们将研究对CDK 7抑制和合成致死的抗性机制， 在SY 1365存在的漏洞。最后，我们将测试SY 1365在内分泌抗性和 CDK 4/6 i抗性PDX模型源自ER+疾病患者的转移性肿瘤。 这项研究的结果有可能导致临床试验测试的疗效和目标活动 一类新的药物，选择性CDK 7抑制剂，用于治疗内分泌和CDK 4/6 i耐药ER+ 转移性乳腺癌这些结果可能会导致一种新的治疗策略，以改善预后， 大量转移性ER+乳腺癌患者。

Project Abstract The majority of breast cancers are estrogen receptor positive (ER+) and ER+ breast cancer is the leading cause of breast cancer mortality. Despite the widespread adoption of adjuvant endocrine therapy for patients with ER+ breast cancer, almost all patients with ER+ metastatic disease will eventually develop resistance to endocrine treatments. A number of mechanisms of endocrine resistance were proposed but for the most these were predominantly based on preclinical evidence. Recently, our group and a number of other groups identified estrogen receptor (ER) ligand-binding domain (LBD) mutations as the most prevalent genomic mechanism of endocrine resistance identified in patients with ER+ metastatic breast cancer. These mutations are associated with decreased overall survival in ER+ metastatic breast cancer. The addition of CDK4/6 inhibitors (CDK4/6i) to endocrine treatment has been shown to improve progression free survival in patients with metastatic ER+ breast cancer, but have not been shown to improve overall survival. Despite this advance, patients with metastatic disease invariably develop resistance to this combined therapy, exhaust other chemotherapy options, and ultimately die of their disease. There is an urgent need to develop new therapeutic strategies to overcome resistance to endocrine treatment and CDK4/6i. Our preliminary data suggests that selective inhibition of CDK7 can overcome resistance to endocrine resistance driven by the ER mutations and resistance to CDK4/6i. CDK7 has key roles in transcriptional and cell cycle regulation. SY1365 is a selective CDK7 inhibitor that is in early stages of clinical development for cancer treatment. This study is designed to comprehensively study the activity of SY1365 as a single agent and in combination with fulvestrant for the treatment of ER mutant endocrine resistant and CDK4/6i resistant ER+ metastatic breast cancer. We will investigate the mechanisms by which CDK7 inhibition exerts anti-tumor activity and overcomes resistance to endocrine treatment driven by the ER mutations and resistance to CDK4/6i. Because CDK7 phosphorylates RNA polymerase II and also functions as a CDK-activating kinase, we will test the effects of SY1365 on nascent RNA and mRNA transcripts, CDK2 phosphorylation and cell cycle progression in ER+ breast cancer models. We will study mechanisms of resistance to CDK7 inhibition and synthetic lethal vulnerabilities in the presence of SY1365. Lastly, we will test the activity of SY1365 in endocrine resistant and CDK4/6i resistant PDX models derived from metastatic tumors from patients with ER+ disease. Results from this study have the potential to lead to a clinical trial testing the efficacy and on target activity of a new class of drugs, selective CDK7 inhibitors, for the treatment of endocrine and CDK4/6i resistant ER+ metastatic breast cancer. These results could lead to a new therapeutic strategy to improve outcomes in a substantial number of patients with metastatic ER+ breast cancer.