Targeting BCL-2 and ABL/LYN in Philadelphia chromosome-positive acute lymphoblastic leukemia

Treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL) remains a challenge. Although the addition of targeted tyrosine kinase inhibitors (TKIs) to standard cytotoxic therapy has greatly improved upfront treatment, treatment-related morbidity and mortality remain high. TKI monotherapy provides only temporary responses and renders patients susceptible to the development of TKI resistance. Thus, identifying agents that could enhance the activity of TKIs is urgently needed. Recently, a selective inhibitor of B cell lymphoma 2 (BCL-2), ABT-199 (venetoclax), has shown impressive activity against hematologicmalignancies. We demonstrate that the combination of TKIs with venetoclax is highly synergistic in vitro, decreasing cell viability and inducing apoptosis in Ph+ALL. Furthermore, the multikinase inhibitors dasatinib and ponatinib appear to have the added advantage of inducing Lck/Yes novel tyrosine kinase (LYN)-mediated proapoptotic BCL-2-like protein 11 (BIM) expression and inhibiting up-regulation of antiapoptotic myeloid cell leukemia 1 (MCL-1), thereby potentially overcoming the development of venetoclax resistance. Evaluation of the dasatinib-venetoclax combination for the treatment of primary Ph+ALL patient samples in xenografted immunodeficientmice confirmed the tolerability of this drug combination and demonstrated its superior antileukemic efficacy compared to either agent alone. These data suggest that the combination of dasatinib and venetoclax has the potential to improve the treatment of Ph+ALL and should be further evaluated for patient care.