Crizotinib-resistan NPM-ALK mutants confer differential sensitivity to unrelated alk inhibitors

The dual ALK/MET inhibitor Crizotinib was recently approved for the treatment of metastatic and late stage ALK+ NSCLC, and is currently in clinical trial for other ALK‐related diseases. As predicted after other TKIs clinical experience, the first mutations that confer resistance to Crizotinib have been described in Non Small Cell Lung Cancer (NSCLC) and in one Inflammatory Myofibroblastic Tumor (IMT) patients. Here we focused our attention on Anaplastic Large Cell Lymphoma (ALCL), where the oncogenic fusion protein NPM-ALK, responsible for 70-80% of cases, represents an ideal Crizotinib target. We selected and characterized two human NPM-ALK+ ALCL cell lines, KARPAS299 and SUP-M2, able to survive and proliferate at different Crizotinib concentrations. Sequencing of ALK kinase domain revealed that a single mutation became predominant at high Crizotinib doses in each cell line, namely L1196Q and I1171N in Karpas299 and SUP-M2 cells, respectively. These mutations also conferred resistance to Crizotinib in Ba/F3 cells expressing human NPM‐ALK. The resistant cell populations, as well as mutated Ba/F3 cells, were characterized for sensitivity to two additional ALK inhibitors: the dual ALK/EGFR inhibitor AP26113 and NVPTAE684. While L1196Q-positive cell lines were sensitive to both inhibitors, cells carrying I1171N substitution showed cross-resistance to all ALK inhibitors tested. This study provides potential relevant information for the management of ALCL patients that may relapse after Crizotinib treatment.