Prioritizing the Catalytic Gatekeepers through Pan- Inhibitory Mechanism of Entrectinib against ALK, ROS1 and TRKA Tyrosine Kinases.

Despite the remarkable clinical activity of kinase inhibitors against anaplastic lymphoma kinase (ALK) and the closely related Ros1 and TRKA kinases, the emergence of resistance to these inhibitors often leads to relapse in most patients. Resistance is usually in the form of mutations and brain metastasis or inhibitors failing to penetrate the blood-brain barrier. The discovery of entrectinib has recently paved way for further exploration of kinase inhibitors that target ALK after it has reportedly demonstrated potency against ALK, Ros1, and TRKA kinases. However, the molecular mechanism surrounding its multi-targeting activity remains unresolved. As such, in this study, we investigate the pan-inhibitory mechanism of entrectinib towards ALK, Ros1, and TRKA, using in silico techniques. Findings show strong binding affinities of ALK = -40.92 kcal/mol, Ros1 = -36.60 kcal/mol, and TRKA = -45.99 kcal/mol for entrectinib towards ALK, Ros1, and TRKA, respectively. Pan-inhibitory binding of entrectinib is characterized by close interaction with peculiar gatekeeper residues on each tyrosine kinase. Entrectinib induced structural stability and rigidity in the backbone conformation of all three tyrosine kinases by showing a consistent pattern of structural alterations. These structural insights provided presents a baseline for the understanding of the pan-inhibitory activity of entrectinib. Establishing the cruciality of the interactions between the phenyl ring and gatekeeper residues could guide the structure-based design of novel tyrosine kinase inhibitors with improved therapeutic activities.