PTPA and acute lymphoblastic leukemia: This increase in PP2A activity with OP449 treatment correlated with a decrease in cell viability in a dose-dependent manner, with an IC50 value of 1.25 μM at 72 hrs across all of these T-ALL cell lines (Figure 2B, p < 0.001 compared to untreated control), together with a dose-dependent increase in cellular apoptosis as reflected by annexin V staining (Supplementary Figure S3).