Advances in Small-Molecule Inhibitors for Targeted Cancer Therapy

Small molecule inhibitors (SMIs) have emerged as powerful tools in modern oncology, offering precise regimens that selectively disrupt key molecular pathways involved in the induction and progression of neoplasms. Over the years, these compounds have evolved from early kinase inhibitors to a wide range of agents targeting signaling cascades, DNA repair systems, and cancer epigenetic regulators. This chapter provides a comprehensive overview of the principles of design, mechanisms of action, and therapeutic uses of small-molecule immunosuppressants in cancer. It covers the main classes of drugs, such as tyrosine kinase inhibitors (TKIs), poly (ADP-ribose) polymerase (PARP) inhibitors, and epigenetic modulators, as well as emerging modalities such as covalent inhibitors, proteolytic targeting chimeras (PROTACs), and allosteric modulators. This chapter also explores structural and fragment-based drug design, computational modeling, and artificial intelligence as transformative tools for driving the discovery of new-generation inhibitors. Clinical observations highlight issues such as bioavailability, tumor heterogeneity, resistance development, and the relevance of treatment guided by biomarkers. Together, these advances highlight the fact that molecular innovation is further improving cancer treatment. Ultimately, Small-molecule inhibitors (SMIs) are a combination of mechanistic knowledge and translational success, bridging laboratory discovery with patient-oriented care and shaping the future of personalized cancer therapies.