Abstract 3583: Drug-resistant NPM/ALK mutants show different sensitivity to second generation tyrosine kinase inhibitors

Rearranged or mutated forms of the Anaplastic Lymphoma Kinase (ALK) are involved in the pathogenesis of various cancers, in particular anaplastic large cell lymphoma (ALCL), non-small-cell lung cancer (NSCLC) and neuroblastoma. ALK-positive tumors are currently treated with crizotinib (XalkoriTM, Pfizer) or ceritinib (ZykadiaTM, Novartis), two oral ALK inhibitors (ALKi). Additional inhibitors are in clinical trial. Despite high response rates, drug-resistant disease often develops in patients. In order to study the mechanisms that underlie resistance, we generated several ALKi-resistant cell lines in vitro. Here we present the selection of novel NPM/ALK-positive ALCL cells resistant to ASP3026 (Astellas) that grow in the presence of up to 2 μM ASP3026 and show 10 to 60 fold shift in IC50. The established ASP3026-resistant cell lines carry several point mutations in the ALK kinase domain (G1128S, C1156F, I1171N/T, F1174I, N1178H, E1210K, and C1156F/D1203N) that confer resistance to ASP3026 when reintroduced in a Ba/F3 cell model. Furthermore, the activity profile of ASP3026, crizotinib, ceritinib, alectinib, AP26113 and PF-06463922 against a panel of 20 NPM/ALK drug-resistant mutants will be presented. We report for each ALKi the IC50 value against the mutants, the IC50 fold increase over wild-type NPM/ALK (relative resistance, RR) and the IC50 ratio between parental Ba/F3 cells and mutants (therapeutic index, TI). From our screen, the G1202R and C1156F/D1203N mutations appear to be highly resistant to all tested inhibitors, therefore they are predicted to be the most challenging mutants for ALKi therapy.