A66 is primarily used as a selective inhibitor of the PI3Kα (phosphoinositide 3-kinase alpha) isoform in biochemical and pharmacological research. It is employed to study signaling pathways involved in cell growth, proliferation, and survival, particularly in cancer-related studies. Researchers use A66 to suppress PI3Kα activity in cell cultures and animal models to understand its role in tumor development and to evaluate potential therapeutic strategies for cancers with PIK3CA mutations. Its selectivity makes it a valuable tool for dissecting the specific contributions of PI3Kα within the broader PI3K pathway, aiding in the development of targeted cancer therapies.