Medicinal Chemistry Strategies in Targeting TGF-βR1 Kinase Domain: Unveiling Insights into Inhibitor Structure-Activity Relationship (SAR).

The transforming growth factor-β (TGF-β) signaling pathway is involved in various cellular functions, including immunological response, extracellular matrix formation, differentiation, growth and development, and cell cycle regulation. The TGF β receptor type 1 (TGF-βR1) has emerged as a key component of this pathway, exhibiting significant overexpression in diverse malignancies, including hepatocellular carcinoma, gastric cancer, breast cancer, and colon cancer. Multiple therapeutic targets have been identified for the TGF-β signaling pathway, encompassing antibodies, ligand traps, vaccines, antisense oligonucleotides, and small-molecule TGF-βR1 kinase inhibitors. This review delineates the structural and functional characteristics of the small-molecule TGF-βR1 kinase inhibitors. The inhibitors discussed herein are categorized based on shared pharmacophoric features, notably a five-membered heterocyclic ring linked to three distinct features (R1, R2, and R3). These features interact with amino acids within the selectivity pocket, hinge region, or solvent-exposed area, respectively. These insights contribute to a clearer understanding of the structural requirements for selective TGF-βR1 inhibition. The presented findings in this review article offer a valuable foundation for future drug discovery efforts targeting the TGF-β signaling pathway.