S55746 hydrochloride is primarily utilized in the field of oncology research. It functions as a potent and selective inhibitor of B-cell lymphoma 2 (BCL-2) proteins, which play a critical role in regulating apoptosis, or programmed cell death. By inhibiting these proteins, it promotes the death of cancer cells, particularly in hematologic malignancies such as chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Its application is significant in preclinical studies and clinical trials aimed at developing targeted therapies for cancers that are resistant to conventional treatments. Additionally, it serves as a valuable tool in understanding the mechanisms of apoptosis and exploring new strategies for cancer treatment.