VX-680 (Tozasertib, MK-0457)S1

Although its multi-kinase profile, VX-680 induces similar cytotoxicity with IC50 of approximately 300 nM and exhibits an AUR B-like inhibitory phenotype of G2/M arrest, endoreduplication and apoptosis in BaF3 cells transfected with ABL or FLT-3 (mutant and wild type) kinases. VX-680 prevents the CAL-62 proliferation in a time-dependent manner. VX-680 treatment for 14 days significantly decreases the number and size of colonies by approximately 70% in the 8305C and 90% in the CAL-62, 8505C and BHT-101. Treatment of the different ATC cells with VX-680 inhibits proliferation with the IC50 between 25 and 150  nM. The VX-680 significantly impairs the ability of the different cell lines to form colonies in soft agar. Analysis of caspase-3 activity indicates that VX-680 induces apoptosis in the different cell lines. CAL-62 cells exposed for 12  hours to VX-680 showed an accumulation of cells with ≥4N DNA content. Time-lapse analysis demonstrates that VX-680-treated CAL-62 cells exit metaphase without dividing. Moreover, histone H3 phosphorylation is abrogated following VX-680 treatment. ^[2] VX-680 has significant inhibitory activity against BCR-Abl bearing the T315I mutation in patient-derived samples. ^[3]