Abstract 121: Ponatinib Promotes Endothelial Cell Inflammation And Leukocyte Trafficking Via Tumor Necrosis Factor Signaling: A Potential Mechanism Of Vascular Toxicity

Background: ABL tyrosine kinase inhibitors (TKI) have dramatically improved chronic myeloid leukemia (CML) survival. Due to resistance to the first ABL-TKI imatinib (Ima), most patients are treated with newer agents, including ponatinib (Pon). Although Pon improves cancer remission, the survival benefit is mitigated by a 4-fold increase in arterial thrombosis. The mechanism of Pon-induced arterial thrombosis and the safety of Asciminib (Asc), a newly approved alternative, are not known. CML patients are older and have notably elevated serum TNFa levels. Hypothesis: Since arterial thrombotic events occur when inflamed vascular plaques rupture, we tested the hypothesis that Pon enhances endothelial cell (EC) response to TNFa, promoting EC inflammation and leukocyte trafficking. Methods and Results: In vitro: Human umbilical vein ECs (HUVECs) were treated with Pon, Ima, or Asc at concentrations observed in humans. Adhesion molecules that mediate leukocyte rolling (E- and P-selectin) and adhesion (ICAM1, VCAM1), and TNF receptors (TNFR) 1 and 2 were quantified at 24 hours by qPCR, flow cytometry (FC), and immunoblot. Pon increased TNFR2, P-selectin, VCAM, and ICAM by FC, qPCR, and immunoblot while Ima and Asc had no impact. In primary human coronary artery ECs Pon, but not Asc nor Ima, similarly increased VCAM and P-selectin mRNA. Pretreatment of HUVECs with a nonspecific TNFR inhibitor prevented Pon induction of ICAM1 and P-selectin mRNA. In vivo: Mice were treated with ABL TKIs by oral gavage to achieve drug plasma levels consistent with those in CML patients. After three days, leukocyte trafficking was quantified by intravital microscopy (IVM) in mouse mesenteric vessels. Pon, but not Asc, increased the number of rolling and adherent leukocytes, and increased serum TNFa by ELISA. Treatment with a TNFR inhibitor blocked Pon induced leukocyte trafficking by IVM. Conclusion: Pon, but not Ima nor Asc, induces expression of TNF receptors and adhesion molecules in human ECs in vitro and promotes leukocyte trafficking in vivo. Since inflamed plaques lead to acute arterial thrombosis, this mechanism could contribute to the high risk of arterial thrombosis in Pon-treated cancer patients. If so, Asc may be a safer choice as it does not induce EC inflammation.