WEHI-539 is primarily used in research settings to study the mechanisms of apoptosis, particularly in relation to the BCL-2 family of proteins. It functions as a selective inhibitor of BCL-XL, a protein that plays a crucial role in preventing programmed cell death. By inhibiting BCL-XL, WEHI-539 helps researchers understand how cancer cells evade apoptosis and develop resistance to treatments. This compound is valuable in exploring potential therapeutic strategies for cancers that overexpress BCL-XL, as it can sensitize cancer cells to apoptosis-inducing agents. Additionally, it aids in investigating the role of BCL-XL in various cellular processes and diseases beyond cancer, such as neurodegenerative disorders and immune responses. Its application is largely confined to laboratory studies, contributing to the development of targeted therapies and a deeper understanding of cell survival mechanisms.