LY2109761 is a selective inhibitor of the transforming growth factor-beta (TGF-β) receptor type I and type II kinases. It is primarily used in research settings to study the role of TGF-β signaling in various biological processes and disease models. One of its key applications is in oncology research, where it helps investigate mechanisms of tumor progression, metastasis, and immune evasion, as TGF-β signaling is often dysregulated in cancer. The compound has been used in preclinical studies to evaluate the therapeutic potential of blocking TGF-β signaling in tumors such as pancreatic, breast, and liver cancers. It has shown ability to enhance the efficacy of other anticancer therapies, including radiation and chemotherapy, by modulating the tumor microenvironment and reducing epithelial-to-mesenchymal transition (EMT). Additionally, LY2109761 is used to explore fibrotic diseases, where excessive TGF-β activity contributes to tissue scarring in organs like the liver, lungs, and kidneys. By inhibiting TGF-β signaling, it helps assess the pathway’s contribution to fibrosis development and potential reversal. Due to its research-focused use, LY2109761 remains a tool compound and is not approved for clinical use in humans.