BTK and B-cell chronic lymphocytic leukemia: Ibrutinib is a first-in-class Bruton’s tyrosine kinase (BTK) inhibitor that is indicated for use in adult patients with CLL, Waldenström’s macroglobulinemia, mantle cell lymphoma, and marginal zone lymphoma as single-agent therapy or in combination with other drugs (https://www.ema.europa.eu/documents/product-information/imbruvica-epar-product-information_en.pdf).