The endocannabinoid system has emerged as a promising target for the treatment of numerous diseases, including cancer, neurodegenerative disorders, and metabolic syndromes. Thus far, two cannabinoid receptors, CB1 and CB2, have been discovered, which are found predominantly in the central nervous system (CB1) or the immune system (CB2), among other organs and tissues. CB1 receptor ligands have been shown to induce a complex pattern of intracellular effects. The binding of a ligand induces distinct conformational changes in the receptor, which will eventually translate into distinct intracellular signaling pathways through coupling to specific intracellular effector proteins. These proteins can mediate receptor desensitization, trafficking, or signaling. Ligand specificity and selectivity, complex cellular components, and the concomitant expression of other proteins (which either regulate the CB1 receptor or are regulated by the CB1 receptor) will affect the therapeutic outcome of its targeting. With an increased interest in G protein-coupled receptors (GPCR) research, in-depth studies using mutations, biological assays, and spectroscopic techniques (such as NMR, EPR, MS, FRET, and X-ray crystallography), as well as computational modelling, have begun to reveal a set of concerted structural features in Class A GPCRs which relate to signaling pathways and the mechanisms of ligand-induced activation, deactivation, or activity modulation. This review will focus on the structural features of the CB1 receptor, mutations known to bias its signaling, and reported studies of CB1 receptor ligands to control its specific signaling.

Hematopoietic progenitor kinase 1 (HPK1), a negative regulator of T-cells, B-cells, and dendritic cells, has gained attention in antitumor immunotherapy research over the past decade. No HPK1 inhibitor has yet reached clinical approval, largely due to selectivity and drug-like limitations. Leveraging the available structural insights into HPK1, we conducted a rational hit identification using a structure-based virtual screening of over 600,000 drug-like molecules from ASINEX and OTAVA databases. A series of molecular docking studies, in vitro kinase assays, and molecular dynamics simulations were conducted to identify viable HPK1 inhibitor hits. This approach resulted in two promising novel hit scaffolds, 4H-Pyrido[1,2-a] thieno[2,3-d] pyrimidin-4-one (ISR-05) and quinolin-2(1H)-one (ISR-03), neither of which has previously been reported as an HPK1 inhibitor. ISR-05 and ISR-03 exhibited IC50 values of 24.2 ± 5.07 and 43.9 ± 0.134 µM, respectively, in kinase inhibition assays. These hits constitute tractable starting points for future hit-to-lead optimization aimed at developing more effective HPK1 inhibitors for cancer therapy.

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 6, representing a previously unreported pyrazolyl-methylene-indolinone scaffold for Pim-1 inhibition, was identified as a Pim-1 inhibitory hit with an IC₅₀ value of 5.77 μM. QM calculations revealed differences in the energetic accessibility of coplanar geometries between the active and inactive compounds, providing a structural explanation for the discrepancy between docking predictions and experimental activity. Moreover, MD simulations of Pim-1 in complex with compound 6 revealed the formation of dual polar interactions between its pyrazole ring and catalytic-region residues K67 and E89. 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.