STF-118804 is primarily used in biochemical and pharmacological research as a selective inhibitor of the enzyme ALK5 (transforming growth factor-beta type I receptor kinase). It plays a key role in studies related to TGF-β signaling pathways, which are involved in cell proliferation, differentiation, and apoptosis. Due to its specificity, STF-118804 is utilized to investigate fibrotic diseases, cancer progression, and epithelial-to-mesenchymal transition (EMT) in vitro and in vivo models. It helps researchers dissect the contribution of ALK5 activity without affecting other closely related kinases, making it a valuable tool compound in developing targeted therapies. Its application is mostly confined to laboratory research and is not used clinically.