Finally, although necessarily limited to two patients by regulatory issues beyond our control, pre-treatment deuterium labeling showed that idelalisib therapy induces rapid release of recently-proliferated sIgMhi cells into PB, consistent with the observation that Ki67 [25] and sIgM expression [26] in circulating CLL cells rapidly rises following initiation of treatment with ibrutinib, likely as a consequence of release from lymphoid tissues. This evidence concerns the gene MKI67 and B-cell chronic lymphocytic leukemia.