MA09.10 Comprehensive Analysis of Secondary Mutation as Resistance Mechanism to Seven MET-TKIs for MET Exon 14 Skipping in Vitro

MET exon 14 skipping mutation have been attracting attentions of thoracic oncologists as a new target of therapy for lung cancer. The efficacy of MET-TKI has been reported, while these tumors, almost always acquire resistance, as in the case of other oncogene-addicted lung cancers. However, its resistance mechanisms are not fully understood. MET exon14 skipping mutation was introduced to Ba/F3 cell retrovirally. Using N-ethyl-N-nitrosourea mutagenesis, we derived resistant clones to seven MET-TKIs and searched for secondary MET mutations. We evaluated their sensitivities to following different TKIs. Type Ia, crizotinib; Type Ib, capmatinib, tepotinib and savolitinib; Type II, cabozantinib, merestinib and glesatinib. We sequenced 201 resistant clones and could obtain 80 clones which had secondary mutations in the MET tyrosine kinase domain. A total of 26 different missense mutations occurring at 12 codons were identified. Of them, D1228 and Y1230 in the activation loop were common sites for type I TKIs that bind to active kinase form (DFG-in), while L1195 and F1200 were those for type II TKIs that bind to inactive form (DFG-out). In general, resistant mutations against type I were sensitive to type II, and vice versa. We identified mutation sites specific for TKI types as resistance mechanisms and complementary activities between type I and type II inhibitors against those mutations. These finding should provide relevant clinical implication for treating patients with lung cancer harboring MET exon 14 skipping.