Ibrutinib, a covalent inhibitor for Bruton’s tyrosine kinase (BTK), was approved by the FDA as one of the first inhibitors for treating relapsed or refractory (R/R) CLL after showing positive results in the RESONATE trial, a randomized phase III trial that compared ibrutinib with a single agent ofatumumab in R/R CLL patients [54]. The gene discussed is BTK; the disease is B-cell chronic lymphocytic leukemia.