As a first-generation Bruton-kinase (BTK) inhibitor, ibrutinib was rapidly approved by the US Food and Drug Administration (FDA), firstly for the treatment of chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) and mantle-cell lymphoma (MCL) in 2013 and 2014. The gene discussed is BTK; the disease is mantle cell lymphoma.