ONO-4059 is primarily used in the field of medical research and drug development, particularly in the study of cancer therapies. It functions as a potent and selective inhibitor of BTK (Bruton's tyrosine kinase), an enzyme that plays a critical role in the signaling pathways of B-cells. By inhibiting BTK, ONO-4059 helps to disrupt the growth and survival of malignant B-cells, making it a potential therapeutic agent for treating B-cell malignancies such as chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Its application extends to preclinical studies aimed at understanding the mechanisms of BTK inhibition and evaluating its efficacy in combination with other anticancer drugs. Additionally, ONO-4059 is utilized in immunological research to explore its effects on autoimmune diseases where B-cell activity is implicated.