Introduction: Novel rearranged in transfection (RET)-specific tyrosine kinase inhibitors (TKIs) such as selpercatinib (LOXO-292) have shown unprecedented efficacy in tumors positive for RET fusions or mutations, notably RET fusion-positive NSCLC and RET-mutated medullary thyroid cancer (MTC). However, the mechanisms of resistance to these agents have not yet been described. Methods: Analysis was performed of circulating tumor DNA and tissue in patients with RET fusion-positive NSCLC and RET-mutation positive MTC who developed disease progression after an initial response to selpercatinib. Acquired resistance was modeled preclinically using a CCDC6-RET fusion-positive NSCLC patient-derived xenograft. The inhibitory activity of anti-RET multikinase inhibitors and selective RET TKIs was evaluated in enzyme and cell-based assays. Results: After a dramatic initial response to selpercatinib in a patient with KIF5B-RET NSCLC, analysis of circulating tumor DNA revealed emergence of RET G810R, G810S, and G810C mutations in the RET solvent front before the emergence of clinical resistance. Postmortem biopsy studies reported intratumor and intertumor heterogeneity with distinct disease subclones containing G810S, G810R, and G810C mutations in multiple disease sites indicative of convergent evolution on the G810 residue resulting in a common mechanism of resistance. Acquired mutations in RET G810 were identified in tumor tissue from a second patient with CCDC6-RET fusion-positive NSCLC and in plasma from patients with additional RET fusion-positive NSCLC and RET-mutant MTC progressing on an ongoing phase 1 and 2 trial of selpercatinib. Preclinical studies reported the presence of RET G810R mutations in a CCDC6-RET patient-derived xenograft (from a patient with NSCLC) model of acquired resistance to selpercatinib. Structural modeling predicted that these mutations sterically hinder the binding of selpercatinib, and in vitro assays confirmed loss of activity for both anti-RET multikinase inhibitors and selective RET TKIs. Conclusions: RET G810 solvent front mutations represent the first described recurrent mechanism of resistance to selective RET inhibition with selpercatinib. Development of potent inhibitor of these mutations and maintaining activity against RET gatekeeper mutations could be an effective strategy to target resistance to selective RET inhibitors.

中文翻译：

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RET 溶剂前沿突变介导 RET 驱动的恶性肿瘤中对选择性 RET 抑制的获得性抗性

简介：新型重排转染 (RET) 特异性酪氨酸激酶抑制剂 (TKI)，例如 selpercatinib (LOXO-292)，在 RET 融合或突变阳性的肿瘤中显示出前所未有的疗效，尤其是 RET 融合阳性 NSCLC 和 RET 突变的甲状腺髓样癌症（MTC）。然而，尚未描述对这些药剂的抗性机制。方法：对 RET 融合阳性 NSCLC 和 RET 突变阳性 MTC 患者的循环肿瘤 DNA 和组织进行分析，这些患者在对 selpercatinib 初始反应后出现疾病进展。使用 CCDC6-RET 融合阳性 NSCLC 患者来源的异种移植物在临床前模拟获得性耐药性。在酶和基于细胞的测定中评估了抗 RET 多激酶抑制剂和选择性 RET TKI 的抑制活性。结果：在一名 KIF5B-RET NSCLC 患者对 selpercatinib 产生了显着的初步反应后，对循环肿瘤 DNA 的分析显示，在出现临床耐药之前，RET 溶剂前沿出现了 RET G810R、G810S 和 G810C 突变。尸检活检研究报告了肿瘤内和肿瘤间异质性，在多个疾病部位含有不同的疾病亚克隆，其中包含 G810S、G810R 和 G810C 突变，表明 G810 残基趋同进化，导致共同的耐药机制。在第二名 CCDC6-RET 融合阳性 NSCLC 患者的肿瘤组织和其他 RET 融合阳性 NSCLC 和 RET 突变 MTC 患者的血浆中发现了 RET G810 获得性突变，正在进行的 selpercatinib 1 期和 2 期试验. 临床前研究报告在 CCDC6-RET 患者来源的异种移植物（来自 NSCLC 患者）模型中存在 RET G810R 突变，该模型对 selpercatinib 具有获得性耐药性。结构模型预测这些突变在空间上阻碍了 selpercatinib 的结合，体外试验证实抗 RET 多激酶抑制剂和选择性 RET TKI 均丧失活性。结论：RET G810 溶剂前沿突变代表了第一个描述的对 selpercatinib 选择性 RET 抑制抗性的复发机制。开发这些突变的强效抑制剂并保持对 RET 看门人突变的活性可能是针对选择性 RET 抑制剂抗性的有效策略。