Cabozantinib Overcomes Crizotinib Resistance in ROS1 Fusion-Positive Cancer

Purpose: ROS1 rearrangement leads to constitutive ROS1 activation with potent transforming activity. In an ongoing phase I trial, the ALK tyrosine kinase inhibitor (TKI) crizotinib shows remarkable initial responses in patients with non-small cell lung cancer (NSCLC) harboring ROS1 fusions; however, cancers eventually develop crizotinib resistance due to acquired mutations such as G2032R in ROS1. Thus, understanding the crizotinib-resistance mechanisms in ROS1-rearranged NSCLC and identification of therapeutic strategies to overcome the resistance are required. Experimental Design: The sensitivity of CD74-ROS1-transformed Ba/F3 cells to multiple ALK inhibitors was examined. Acquired ROS1 inhibitor-resistant mutations in CD74-ROS1 fusion were screened by N-ethyl-N-nitrosourea mutagenesis with Ba/F3 cells. To overcome the resistance mutation, we performed high-throughput drug screening with small-molecular inhibitors and anticancer drugs used in clinical practice or being currently tested in clinical trials. The effect of the identified drug was assessed in the CD74-ROS1-mutant Ba/F3 cells and crizotinib-resistant patient-derived cancer cells (MGH047) harboring G2032R-mutated CD74-ROS1. Results: We identified multiple novel crizotinib-resistance mutations in the ROS1 kinase domain, including the G2032R mutation. As the result of high-throughput drug screening, we found that the cMET/RET/VEGFR inhibitor cabozantinib (XL184) effectively inhibited the survival of CD74-ROS1 wild-type (WT) and resistant mutants harboring Ba/F3 and MGH047 cells. Furthermore, cabozantinib could overcome all the resistance by all newly identified secondary mutations. Conclusions: We developed a comprehensive model of acquired resistance to ROS1 inhibitors in NSCLC with ROS1 rearrangement and identified cabozantinib as a therapeutic strategy to overcome the resistance. (C) 2014 AACR.