Structural Prerequisites for Pim-1 Kinase Inhibition and the Identification of a Pyrazolyl-Methylene-Indolinone Hit.

Introduction: Pim-1 is a serine/threonine kinase of the pan-Pim family (Pim-1, -2, and -3), whose overexpression is associated with various cancers. Its distinctive hinge-region architecture provides opportunities for selective inhibitor development, with several inhibitors reported as clinical candidates. Understanding structure-activity relationships is essential for distinguishing biologically active compounds from high-scoring docking hits, a major challenge in structure-based drug discovery. Methods: A virtual screening workflow comprising Glide docking and Induced Fit Docking (IFD) was applied to approximately 900,000 commercially available compounds. Six structurally diverse compounds were selected for in vitro Pim-1 inhibitory activity evaluation. Molecular dynamics (MD) simulations and quantum mechanical (QM) calculations were subsequently performed to investigate the structural determinants of inhibitory activity. Results: Among the tested compounds, compound Discussion: These findings provide insight into the structural and conformational requirements for productive Pim-1 inhibition and highlight the value of integrating docking, MD simulations, and QM calculations during the search for novel inhibitors. The identified hit represents a previously unreported scaffold for Pim-1 inhibition that may provide a starting point for future optimization.