The activation of the B cell receptor (BCR) is nowadays known to play a primary role in the etiopathogenesis of a multitude of B cell malignancies, being one of the main factors responsible for the enhanced proliferation and survival of transformed cells. Thanks to the characterization and continuous discovery of the pathways driving B cell proliferation in consequence to BCR activation, it has been possible to develop a small molecule inhibitor specifically antagonizing the Bruton's tyrosine kinase (BTK), an enzyme located in an early strategic position within the whole pathway. Ibrutinib, formerly PCI-32765, is a first in class, potent, specific, irreversible and relatively safe BTK inhibitor, demonstrating so far an impressive efficacy in the treatment of chronic lymphocytic leukemia, diffuse large B cell lymphoma, follicular lymphoma, mantle cell lymphoma (MCL), Waldenström macroglobulinemia and multiple myeloma. This review will summarize the most important pharmacological evidences available as of today and will take in consideration the latest findings regarding the mechanism of action of ibrutinib.
