The first-in-class BTK inhibitor ibrutinib has been approved by the United States Food and Drug Administration for the treatment of mantle cell lymphoma (MCL), chronic lymphocytic leukemia (CLL), Waldenström’s macroglobulinemia (WM), marginal zone lymphoma (MZL) and chronic graft versus host disease (cGVHD) (Akinleye et al., 2013; Parmar et al., 2014; Wen et al., 2021). The gene discussed is BTK; the disease is marginal zone lymphoma.