Brukinsa 80 mg Brukinsa contains Zanubrutinib, a small-molecule, second-generation inhibitor of Bruton's tyrosine kinase (BTK). Zanubrutinib forms a covalent bond with a cysteine residue in the BTK active site, leading to irreversible inhibition of BTK enzymatic activity. BTK is a signaling molecule of the B-cell antigen receptor (BCR) and cytokine receptor pathways essential for B-cell proliferation, trafficking, chemotaxis, and adhesion. By blocking BTK, zanubrutinib inhibits malignant B-cell proliferation and induces apoptosis. It is indicated for the treatment of adult patients with mantle cell lymphoma (MCL), Waldenström's macroglobulinemia (WM), marginal zone lymphoma (MZL), and chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL).