Optimization and Characterization of "MYC Degraders" for Pediatric Medulloblastoma

项目总结 髓母细胞瘤(MB)是一种高度恶性的小脑肿瘤，最常见于儿童。 尽管在治疗方面取得了进步--包括手术、放射和化疗--但大约三分之一的 MB患者仍然死于这种疾病，幸存者因治疗而遭受严重的副作用。基因组学 对患者样本的分析和生物信息学分析已经确定了MB-WNT、Sonic Hedgehog(SHH)、第3组(MYC驱动)和第4组。这些亚组在突变、基因和 表达谱和患者结果，以及患者可以使用相关的基因和 免疫组织化学标志物。大约四分之一的MBS是第3组(G3)肿瘤，表现为 C-Myc(Myc)癌基因的过度表达或扩增。患有G3MB的患者更有可能出现 确诊时有转移性疾病的患者复发率较高，存活率最低。 因此，迫切需要更有效的治疗G3MB的方法。 为了确定在G3MB中有效的MYC抑制剂，我们开发了一种表型、靶标不可知的试验 使用从G3MB原位患者来源的异种移植物(PDX)中分离的疾病相关细胞。化验结果是 旨在识别降低内源性MYC水平的小分子--这是 G3MB-在4小时内，优先调制直接影响MYC稳定性的目标，避免间接或关闭- 稍后时间点的目标效果。我们应用这种分析方法筛选了100,000个化合物集合，并确定了 能显著降低细胞MYC水平的小分子支架。命中率在严格的测试中得到验证 漏斗设计以避免不受欢迎的作用机制，初步探索了几种支架的合成孔径雷达。 从这些研究中，最有希望的一系列活动也被优先安排在100 NM的能力范围内 作为具有良好BBB渗透性的化合物特性。我们进一步证实了这其中的化合物 系列在暴露48小时后降低细胞活性，并且这种影响与MYC中的潜能相关 化验。这一系列中最活跃的化合物SBI1242的初步数据表明，细胞的这种减少 G3MB患者细胞的活性比IPSC来源的神经元具有选择性，这表明可能是一个治疗窗口。 这项建议的目标是进一步优化SBI1242以进行临床前体内试验，并使用最好的模拟来 测试我们的假设G3MB标志性生物标记物MYC的抑制剂在与疾病高度相关的 CONTEXT可以安全有效地阻止或逆转G3MB特异性原位PDX小鼠的肿瘤生长 模特。我们期望这些研究的成功完成，将是迈向我们长远目标的重要一步。 目标是为MB和其他由MYC驱动的癌症确定新的、安全和有效的治疗方法。

PROJECT SUMMARY Medulloblastoma (MB) is a highly malignant tumor of the cerebellum that occurs most frequently in children. Despite advances in treatment – including surgery, radiation, and chemotherapy – approximately one-third of MB patients still die from the disease and survivors suffer severe side effects as a result of treatment. Genomic profiling and bioinformatic analyses of patient samples have identified four subgroups of MB – WNT, Sonic hedgehog (SHH), Group 3 (MYC-driven) and Group 4. These subgroups differ in terms of mutations, gene expression profiles and patient outcomes, and patients can be stratified using relevant genetic and immunohistochemical markers. Approximately one-quarter of MBs are Group 3 (G3) tumors, which exhibit overexpression or amplification of the c-Myc (MYC) oncogene. Patients with G3 MB are more likely to present with metastatic disease at time of diagnosis, have a higher incidence of recurrence and the poorest survival rate. Thus, more effective therapies for G3 MB are critically needed. To identify MYC inhibitors that would be effective in G3 MB, we developed a phenotypic, target-agnostic assay using disease-relevant cells isolated from G3 MB orthotopic patient-derived xenografts (PDXs). The assay was designed to identify small molecules that reduce endogenous MYC levels – the signature molecular marker of G3 MB – in 4 hours, to preferentially modulate targets directly affecting MYC stability and avoid indirect or off- target effects at later time points. We applied this assay to screen a 100,000 compound collection and identified small molecule scaffolds that robustly decrease cellular MYC levels. Hits were validated in a rigorous testing funnel designed to avoid undesired mechanisms of action, and initial SAR was explored for several scaffolds. From these studies the most promising series was prioritized with activities in the 100 nM potency range as well as compound properties indicative of good BBB penetration. We further confirmed that the compounds in this series decrease cell viability after 48 hours exposure and that this effect correlates with potency in the MYC assay. Preliminary data for the most active compound of this series, SBI1242, indicate that this decrease in cell viability of G3 MB patient cells is selective over iPSC-derived neurons, suggesting a possible therapeutic window. The goal of this proposal is to further optimize SBI1242 for preclinical in vivo testing and use the best analog to test our hypothesis that inhibitors of the G3 MB signature biomarker MYC identified in a highly disease-relevant context can safely and effectively arrest or reverse tumor growth in our G3 MB-specific orthotopic PDX mouse model. We anticipate that successful completion of these studies will be a significant step towards our long-term goal of identifying novel, safe, and effective treatments for MB and other MYC-driven cancers.