Poseltinib (Cat No.:I008829) is an oral, covalent inhibitor of Bruton’s tyrosine kinase (BTK), a key enzyme in B-cell receptor signaling that regulates B-cell activation, proliferation, and survival. By irreversibly binding to BTK, poseltinib suppresses abnormal immune responses, making it a candidate therapy for autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus. Preclinical and early clinical studies demonstrated effective modulation of B-cell function and reduced inflammatory activity. Although its development in certain indications has been limited, poseltinib remains valuable in exploring BTK-targeted immunomodulation strategies.