BH3I-1 is a selective inhibitor targeting the Bcl-2 family protein Bcl-xL, which plays a key role in regulating apoptosis. Its primary application lies in cancer research, particularly in studies involving tumor cell survival and resistance to chemotherapy. By inhibiting Bcl-xL, BH3I-1 promotes apoptosis in cancer cells that overexpress this anti-apoptotic protein, making it a valuable tool for probing apoptotic pathways and evaluating potential therapeutic strategies. It is widely used in preclinical studies to sensitize cancer cells to other cytotoxic agents, enhancing the effectiveness of chemotherapy in models of solid tumors and hematological malignancies. Due to its selectivity, BH3I-1 helps researchers dissect the specific contributions of Bcl-xL versus other Bcl-2 family members in cell survival and drug resistance. Its application extends to combination therapy experiments, where it is used to overcome resistance mechanisms and induce mitochondrial outer membrane permeabilization, leading to programmed cell death.