ACT-128800 is a potent and selective inhibitor of the p38 mitogen-activated protein kinase (MAPK) pathway, which plays a key role in the production of pro-inflammatory cytokines. It has been investigated for its therapeutic potential in inflammatory and autoimmune diseases such as rheumatoid arthritis, inflammatory bowel disease, and chronic obstructive pulmonary disease (COPD). Due to its high selectivity and oral bioavailability, ACT-128800 has shown efficacy in preclinical models by reducing inflammation and tissue damage. It is also being explored for use in neurodegenerative conditions where neuroinflammation contributes to disease progression. Its development highlights the importance of targeting intracellular signaling pathways to modulate immune responses without broad immunosuppression.