However, the utility of this regimen may lie in its ability to enhance therapeutic responses to cytotoxic drugs.5, 31 Neither ibrutinib, ruxolitinib, nor the combination is cytotoxic to CLL cells in vitro5 and it is not well‐understood how CLL cells are eliminated by ibrutinib in vivo.25 Ibrutinib may sensitize CLL cells to cytotoxic stresses in the body by flushing them out of protective microenvironments in part by blocking CXCR4‐signaling.25 Since CXCR4 also signals through JAKs,26 ruxolitinib may flush additional CLL cells from protective microenvironments. This evidence concerns the gene CXCR4 and B-cell chronic lymphocytic leukemia.