Zanubrutinib (formerly known as BGB-3111) was developed by BeiGene as a small-molecule inhibitor of Bruton's tyrosine kinase (BTK). The drug forms a covalent bond with a cysteine residue in the BTK active site, leading to inhibition of BTK activity. BTK signaling results in activation of pathways necessary for B-cell proliferation, trafficking, chemotaxis, and adhesion, thus Zanubrutinib inhibits malignant B-cell proliferation and reduces tumor growth. Zanubrutinib was granted accelerated approval by the FDA in November 2019 based on clinical trial results that demonstrated an 84% overall response rate from zanubrutinib therapy in patients with mantle cell lymphoma (MCL). On August 31, 2021, the Food and Drug Administration approved zanubrutinib for adult patients with Waldenström’s macroglobulinemia (WM).