In addition, ibrutinib can be combined with other agents, including PI3K inhibitor umbralisib [212] and buparlisib [241], cyclin-dependent kinase 4/6 (CDK4/6) inhibitor palbociclib [242], and proteasome enzyme inhibitors carfilzomib [243], which showed preliminary activities and good tolerability in R/R MCL patients in early-phase studies. The gene discussed is CDK4; the disease is mantle cell lymphoma.