Preliminary data from our group indicate that approximately two‐thirds of “real‐world” CLL patients initiating ibrutinib therapy are on concomitant medications that could increase ibrutinib levels (such as CYP3A inhibitors) and ~ 3% are on drugs that could decrease ibrutinib efficacy (such as CYP3A inducers).6 This evidence concerns the gene CYP3A4 and B-cell chronic lymphocytic leukemia.