Targeting MEK to Restore Radioiodine Efficacy for RAI-Refractory Thyroid Cancer

描述(由申请人提供)：这是一项为期3年的新的R01申请，涉及NCI/CTEP授予的II期研究，该研究将评估MEK 1/2抑制剂曲美替尼(GlaxoSmithKline，GSK1120212)恢复放射性碘(RAI)掺入的能力和对RAS突变(MUT)或BRAF/RAS野生型(WT)、RAI-难治(RAIR)甲状腺癌患者的疗效。这项试验将作为一项多中心研究进行，MSKCC作为牵头中心，NIH作为合作地点。转移性疾病是甲状腺癌相关死亡的最常见原因，RAI(或131I)仍然是这些患者的主要治疗方法。不幸的是，许多甲状腺癌患者的肿瘤不再捕获碘，因此对RAI无效，这预示着预后很差。甲状腺乳头状癌(PTC)与编码丝裂原活化蛋白激酶(MAPK)信号通路效应因子(即RET、NTRK、RAS和BRAF)的癌基因互斥突变有关。甲状腺细胞中MAPK信号通路的致癌激活通过抑制碘摄取和滞留所需基因的表达而导致RAI的难治性。在小鼠甲状腺癌模型中，我们发现，对MAPK通路的药物抑制恢复了这些基因的表达，并恢复了肿瘤捕获RAI的能力。基于这些观察，我们进行了一项先导性临床试验，证明MEK抑制剂selumetinib(阿斯利康)可以恢复部分RAIR患者的RAI疗效。124I PET/CT扫描被用来量化塞鲁米替尼引起的单个甲状腺肿瘤内碘掺入的变化，并预测131I治疗的临床疗效。131I是一种被称为“皮损剂量学”的创新分析技术。这种方法对RAS-MUT肿瘤特别有效；在BRAF/RAS-WT肿瘤中观察到了更多的异质性结果。现在需要的是一项概念验证、以基因型为重点的临床试验，以确定这是否是治疗RAS MUT病的临床有效靶向方法，并探索以下假设：更有效的MEK抑制可以优化BRAF/RAS WT患者的RAI疗效。中心假设需要最大程度的MEK抑制才能以最佳方式恢复RAI对RAS MUT和BRAF/RAF/RAS WT RAIR甲状腺癌患者的疗效，我们建议进行一项临床试验，使用更有效的MEK抑制剂曲美替尼来恢复这些患者的RAI掺入(通过124I PET皮损剂量学测量)和疗效(AIM#1)。我们还将进行相关的组织研究，以确定基因组格局和曲美替尼诱导的基因表达变化如何与药物对肿瘤内RAI作用的临床影响相关(AIM#2)。使用靶向治疗来恢复RAI的疗效，进行124I PET损伤剂量学来指导RAI的临床使用，以及开发一种新的靶向治疗RAI MUT病的方法，这些都是RAIR甲状腺癌治疗的范式转变进展，也可能对其他癌症具有借鉴意义，在这些癌症中，“再分化”的概念可能被探索为新的治疗方法。

DESCRIPTION (provided by applicant): This is a new 3-year R01 application involving a NCI/CTEP awarded phase II study that will evaluate the ability of the MEK 1/2 inhibitor trametinib (GlaxoSmithKline, GSK1120212) to restore radioiodine (RAI) incorporation and efficacy for patients with RAS mutant (MUT) or BRAF/RAS wild-type (WT), RAI-refractory (RAIR) thyroid cancers. This trial will be conducted as a multicenter study with MSKCC as the lead center and the NIH a collaborating site. Metastatic disease represents the most frequent cause of thyroid cancer-related death, and RAI (or 131I) remains a mainstay of therapy for these patients. Unfortunately, many thyroid cancer patients have tumors that no longer trap iodine, and are hence refractory to RAI, heralding a poor prognosis. Papillary thyroid cancers (PTC) are associated with mutually exclusive mutations of oncogenes encoding effectors of the mitogen activated protein kinase (MAPK) signaling pathway (i.e. RET, NTRK, RAS and BRAF). Oncogenic activation of MAPK signaling in thyroid cells contributes to RAI refractoriness by suppressing the expression of genes required for iodine uptake and retention. In mouse models of thyroid cancer, we discovered that pharmacologic inhibition of the MAPK pathway restored the expression of these genes and the ability of tumors to trap RAI. Based on these observations, we conducted a pilot clinical trial which demonstrated that the MEK inhibitor selumetinib (AstraZeneca) can restore RAI efficacy in a subset of RAIR patients. 124I PET/CT scans were used to quantify selumetinib-induced changes in iodine incorporation within individual thyroid tumors and predict the clinical efficacy of therapeutic 131I, an innovative analytic technique termed "lesional dosimetry". This approach was particularly effective for RAS MUT cancers; more heterogeneous results were observed for BRAF/RAS WT tumors. What is now required is a proof-of-concept, genotype-focused clinical trial to determine if this is a clinically effective targeted approach for treating RAS MUT disease, and explore the hypothesis that more potent MEK inhibition can optimize RAI efficacy for BRAF/RAS WT patients. With the central hypothesis that maximal MEK inhibition is required to optimally restore RAI efficacy for RAS MUT and BRAF/RAS WT RAIR thyroid cancer patients, we propose to conduct a clinical trial using the more potent MEK inhibitor trametinib to restore RAI incorporation (measured by 124I PET lesional dosimetry) and efficacy in these patients (AIM #1). We will also perform correlative tissue studies to determine how the genomic landscape and trametinib-induced changes in gene expression correlate to the clinical impact of the drug upon RAI action within tumors (AIM #2). Using a targeted therapy to restore RAI efficacy, conducting 124I PET lesional dosimetry to guide clinical use of RAI, and developing a novel targeted approach for treating RAS MUT disease represent paradigm-shifting advances for the treatment of RAIR thyroid cancers that could also hold implications for other cancers in which "re-differentiation" concepts may be explored as novel therapies.