MAP Kinase Inhibitors in Cancer and Other Diseases

Mitogen-activated protein kinase (MAPK) cascades, including the ERK1/2, JNK, p38, and ERK5 subfamilies, are central regulators of cellular processes such as proliferation, differentiation, apoptosis, and inflammation. Dysregulation of these signaling pathways is a hallmark of human diseases, most notably cancer, where they drive tumorigenesis, metastasis, and drug resistance, as well as chronic inflammatory and neurodegenerative disorders. The therapeutic potential of targeting MAPKs has spurred the development of numerous small-molecule inhibitors. This review provides a focused analysis of key MAPK inhibitors in oncology, including JNK inhibitors, p38 inhibitors, BIRB-796, ERK1/2 inhibitors and ERK5 inhibitors. We detail their mechanisms of action, preclinical efficacy across diverse cancer models, and progress in clinical trials. Despite promising preclinical data and the entry of several compounds into clinical evaluation, challenges such as low kinase selectivity, off-target effects, and the emergence of resistance mechanisms have limited success, mirroring the difficulties encountered when developing p38 inhibitors for inflammatory diseases. However, emerging strategies, including rational combination therapies, computer-assisted structure-based design for isoform-specific inhibition, and the exploration of novel chemical scaffolds, offer renewed promise. This review concludes by discussing these future directions and the ongoing potential of MAPK inhibitors as a cornerstone of targeted therapy for cancer and other diseases.