GW2580, chemically known as 5-[3-Methoxy-4-(4-methoxybenzyloxy)benzyl]pyrimidine-2,4-diamine, is a potent, selective, and orally bioavailable inhibitor of the colony-stimulating factor 1 receptor (CSF1R or c-Fms) tyrosine kinase. It functions by competitively binding to the ATP-binding site of CSF1R, thereby blocking its kinase activity. Its primary application is in biomedical research as a pharmacological tool to specifically inhibit CSF1R signaling. This pathway is crucial for the survival, proliferation, and differentiation of macrophages and microglia. Consequently, GW2580 is widely used in preclinical studies to investigate the role of these cells in various disease contexts, including cancer (e.g., tumor-associated macrophages), inflammatory diseases, autoimmune disorders, and neurological conditions. It serves as a key compound for validating CSF1R as a therapeutic target. Due to its specific mechanism of action targeting a key immunomodulatory pathway, GW2580 is also classified under the broader category of immunomodulatory and anti-inflammatory agents. It represents a research-stage pharmaceutical active ingredient for potential therapeutic development in inflammation and oncology.