TRK xDFG Mutations Trigger a Sensitivity Switch from Type I to II Kinase Inhibitors

On-target resistance to next-generation kinase inhibitors, drugs specifically designed to maintain potency in the setting of kinase domain mutations, remains poorly characterized. Having identified that xDFG (TRKA G667) mutations confer second-generation TRK inhibitor resistance in patients with TRK fusion-positive cancers, we used computational modeling and biochemical assays to study how these affect drug binding. We found that xDFG mutations stabilize the inactive kinase conformation, hampering the binding of type I second-generation TRK inhibitors, while increasing the affinity for type II multikinase inhibitors. Type II drugs consistently inhibit the growth and TRK-mediated signaling of isogenic and patient-derived models harboring xDFG mutations. Collectively these data demonstrate that TRK xDFG substitutions trigger conformational changes that favor type II binding mechanisms. Given prior identification of paralogous xDFG resistance mutations in other oncogene addicted cancers, these findings provide insight into rational drug design to address these recalcitrant resistant alterations by leveraging inhibitor class affinity switching.