To study whether S63845 might exert its antiviability effect through the enhancement of imatinib-induced apoptosis of CML cells, we tested the impact of the two drugs, alone or in combination on caspase-3/7 activation (cleavage) and caspase-specific cleavage of poly(ADP-ribose) polymerase (PARP) [21–23] in K562 and TCCS cells by western blot (Fig. 2). Here, CASP3 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.