ABT-737 is a potent small-molecule inhibitor that targets anti-apoptotic Bcl-2 family proteins, including Bcl-2, Bcl-xL, and Bcl-w. It is primarily used in cancer research to induce apoptosis in tumor cells that overexpress these survival proteins. The compound has shown significant activity in hematological malignancies such as chronic lymphocytic leukemia (CLL), acute myeloid leukemia (AML), and lymphoma, where it promotes cell death by displacing pro-apoptotic proteins like Bax and Bak. It is widely employed as a research tool to study apoptosis signaling pathways and to evaluate the dependence of cancer cells on specific Bcl-2 family members. ABT-737 also enhances the efficacy of conventional chemotherapeutic agents and radiation by lowering the threshold for apoptosis, making it valuable in combination therapy studies. Due to its role in overcoming treatment resistance, it serves as a prototype for the development of clinically used drugs like navitoclax and venetoclax.