GS87 is a highly specific and potent GSK3 inhibitor that induces AML cell differentiation. GS87 is a highly specific and potent GSK3 inhibitor that induces AML cell differentiation. A, molecular structure of GS87. B, GS87 is a potent GSK3 inhibitor. In vitro kinase assay for GSK3α and GSK3β. C, GS87 leads to extensive AML differentiation as measured by respiratory burst capacity. OCI, HL-60, and NB4 cells were treated with GS87 (30 μmol/L), Li (10 mmol/L), or SB (20 μmol/L) for 72 hours and differentiation capacity was measured using the NBT reduction assay. D, GS87 leads to more effective AML differentiation than other clinically used GSK3 inhibitors. HL-60 cells were treated with GS87 (30 μmol/L), tideglusib (30 μmol/L), or LY-2090314 (30 μmol/L) for 72 hours and differentiation was measured by the NBT assay. **, P < 0.01. NBT, nitrotetrazolium blue. Sophia Hu et al. Mol Cancer Ther 2016;15:1485-1494 ©2016 by American Association for Cancer Research