Ponatinib

Ponatinib (AP 24534) is a potent, orally active pan-inhibitor of BCR-ABL kinase with IC50 of 0.37 and 2.0 nM for ABL and mutant ABLT315I, respectively; retains high potency against other ABL mutants Q252H, Y253F, M351T and H396P (IC50s<0.5 nM), also inhibits c-Src, Lyn, c-KIT, VEGFR2, FGFR1, PDGFRα (IC50s=0.2-5 nM) ; inhibits the growth of cells expressing native or mutant BCR-ABL (IC50s=0.5–36 nM) suppresses BCR-ABL (T315I) -driven tumor growth in mice, and completely abrogated resistance in cell-based mutagenesis screens. Blood Cancer Approved (In Vitro) :Ponatinib (AP24534) potently inhibits native ABL (IC50: 0.37 nM), ABLT315I (IC50: 2.0 nM), and other clinically important ABL kinase domain mutants (IC50: 0.30-0.44 nM) . Ponatinib also inhibits SRC (IC50: 5.4 nM) and members of the VEGFR, FGFR, and PDGFR families of receptor tyrosine kinases. Ponatinib potently inhibits proliferation of Ba/F3 cells expressing native BCR-ABL (IC50: 0.5 nM) . All BCR-ABL mutants tested remained sensitive to Ponatinib (IC50: 0.5-36 nM) including BCR-ABLT315I (IC50: 11 nM) .Ponatinib inhibits the in vitro kinase activity of FLT3, KIT, FGFR1, and PDGFRα with IC50 values of 13, 13, 2, and 1 nM, respectively. Ponatinib inhibits phosphorylation of all 4 RTKs in a dose-dependent manner, with IC50 values between 0.3 to 20 nM. Consistent with these activated receptors being important in driving leukemogenesis Ponatinib also potently inhibits the viability of all 4 cell lines with IC50 values of 0.5 to 17 nM. In contrast, the IC50 for inhibition of RS4;11 cells which express native (unmutated) FLT3, is more than 100 nM. (In Vivo) :In a survival model in which mice are instead injected with Ba/F3 BCR-ABLT315I cells, administration of Dasatinib at doses as high as 300 mg/kg has no effect on survival time. By contrast, treatment with Ponatinib (AP24534) prolongs survival in a dose-dependent manner. Ponatinib dosed orally for 19 days at 5, 15, and 25 mg/kg prolongs median survival to 19.5, 26, and 30 days, respectively compare to 16 days for vehicle-treated mice (p<0.01 for all three dose levels) . The anti-tumor activity of Ponatinib (AP24534) is further assessed in a xenograft model in which Ba/F3 BCR-ABLT315I cells are injected subcutaneously into mice. Tumor growth is inhibited by Ponatinib in a dose-dependent manner compare to vehicle-treated mice, with significant suppression of tumor growth upon daily oral dosing at 10 and 30 mg/kg (%T/C = 68% and 20%, respectively; p<0.01 for both dose levels) . Daily oral dosing of 50 mg/kg Ponatinib causes significant tumor regression (%T/C = 0.9%, p<0.01), with a 96% reduction in mean tumor volume at the final measurement compared to the start of treatment. Ponatinib is well tolerated at all efficacious dose levels for the duration of the study; maximal decreases in body weight are <5%, <5%, and <12% for the 10, 30, and 50 mg/kg dose groups, respectively, with no signs of overt toxicity.Ponatinib (1-25 mg/kg) is administered orally, once daily for 28 days, to mice bearing MV4-11 xenografts. Ponatinib potently inhibits tumor growth in a dose-dependent manner. Administration of 1 mg/kg, the lowest dose tested, leads to significant inhibition of tumor growth (TGI=46%, P<0.01) and doses of 2.5 mg/kg or greater results in tumor regression.