Abstract P3105: Improving Cardiovascular Toxicity Of Chronic Myeloid Leukemia Therapy.

Introduction: Ponatinib is one of the most cardiotoxic Tyrosine Kinase Inhibitors (TKIs), but continues to be used in clinical practice as it is the only TKI effective against the most common ABL T315I mutation in Chronic Myeloid Leukemia (CML). Long-term exposure to ponatinib increases cardiovascular events including myocardial infarction, heart failure, stroke, peripheral vascular disease and venous thrombosis. Novel therapeutics are needed to provide treatment for this common form of CML while avoiding cardiovascular side effects. Hypothesis: Chemical reengineering can create novel TKIs effective against T315I mutant CML but with reduced cardiovascular toxicity. Methods: Using fragment-based approach, we generated new, safer analogues of ponatinib. The anti-tumor efficacy of these analogues was tested in 2 different CML cell lines (K562 T315I and KCL22 T315I) and in CML patient samples. We assayed for myocardial toxicity by measuring contractile function in human iPSC-cardiomyocytes (hiPSC-CMs) using high-throughput functional imaging, and assayed for vascular toxicity by measuring vasculogenesis in human microvascular endothelial cells (HMVECs). Finally, we confirmed the safer cardiovascular profile and adequate anti-tumor efficacy in an in vivo xenograft mouse model of CML. Results: The new analogues inhibited T315I BCR-ABL kinase activity similar to ponatinib and suppressed T315I mutant CML tumor growth in vitro and in vivo . Compared to ponatinib, the new compounds showed markedly decreased adverse effects on contractility of hiPSC-CMs and vasculogenesis in HMVECs in vitro . The therapeutic window was increased in vivo , leading to regression of human T315I mutant CML xenografts comparable to ponatinib but without increased levels of cardiac troponin. Additionally, we identified multiple kinases, including FGFR1, that were inhibited by ponatinib but not the analogues, suggesting that there is a specific set of kinases responsible for ponatinib toxicity. Conclusions: This study demonstrates that chemical reengineering can generate novel, cardiovascular-safe TKIs that retain effective therapeutic properties against CML carrying ABL T315I mutation, but that exhibit minimal cardiovascular toxicity compared to ponatinib.