Ibrutinib, a small-molecule inhibitor of Bruton’s tyrosine kinase (BTK) and bone marrow X-linked (BMX) non-receptor tyrosine kinase, has been approved for the treatment of patients with chronic lymphocytic leukemia (CLL) and mantle cell lymphoma [235]. The gene discussed is NTRK1; the disease is B-cell chronic lymphocytic leukemia.