lbrutinib is a small-molecule inhibitor of BTK. lbrutinib forms a covalent bond with a cysteine residue in the BTK active site, leading to inhibition of BTK enzymatic activity. BTK is a signaling molecule of the B-cell antigen receptor (BCR) and cytokine receptor pathways. BTK’s role in signaling through the B-cell surface receptors results in activation of pathways necessary for B-cell trafficking, chemotaxis, and adhesion. Nonclinical studies show that Ibrutinib inhibits malignant B-cell proliferation and survival In Vivo as well as cell migration and substrate adhesion In Vitro.