Protein kinases are essential regulators of cellular signaling pathways and are major therapeutic targets due to their central roles in cell growth, survival, angiogenesis, and stress response. They are high-priority drug targets in oncology, inflammatory conditions, and other diseases driven by dysregulated kinase signaling. These enzymes share a common adenosine triphosphate-binding pocket but differ in surrounding motifs. Thus, the challenge in designing selective inhibitors of these enzymes lies in the identification of key residues both in the pocket that binds adenosine triphosphate and its surroundings. One way to study the active site is to probe its interactions with known ligand molecules and rationalize the binding using the molecular hardness of the ligands. Thus, the present study has examined five clinically relevant kinases: cyclin dependent kinase 2, epidermal growth factor receptor kinase, mitogen-activated protein kinase 14, Src kinase, and vascular endothelial growth factor receptor 2. The study utilized an informatics database to analyze over 50 ligands per enzyme, calculating molecular hardness and predicting binding affinities. The relationships between the molecular hardness and binding affinities were studied in detail. Together, these results highlight the interplay of hardness in ligand–kinase interactions and provide insight that may aid rational design of selective kinase inhibitors for immense therapeutic potential.
