ONO-4057 (also known as Tirabrutinib) is a potent, selective, covalent inhibitor of Bruton's Tyrosine Kinase (BTK), a critical enzyme in B-cell receptor (BCR) signaling pathways. It is primarily used in medical research for investigating B-cell malignancies such as lymphomas, autoimmune diseases, and inflammatory disorders. By irreversibly binding to BTK, it disrupts aberrant signaling, aiding in the study of disease mechanisms and preclinical evaluation of targeted therapies. Its high specificity makes it a valuable tool in drug development for precision immunomodulation.