In vivo pharmacokinetic, pharmacodynamic, and CFU assay of hCD34⁺ cells from cord blood. (A) Plasma concentration of SJ6986 in NSG mouse dosed with a single dose of SJ6986 (either 1 mg/kg or 3 mg/kg) by oral gavage. (B) SJ6986 degrades GSPT1 in a dose-dependent manner in hCD19⁺ cells from the spleen and bone marrow. Tumor-bearing NSG mice were dosed by oral gavage with SJ6986, daily for 2 days and hCD19⁺ leukemic cells were harvested 6 hours after last dosing. (C-F) The morphology of CFUs derived from hCD34⁺ cells treated with vehicle (C), 10 nM of SJ6986 (D), 50 nM of SJ6986 (E), and 100 nM of SJ6986 (F); bar = 2 mm. Vehicle or different concentrations of SJ6986 were added once to the medium. (G-H) The total number of CFUs is shown in panel G and the number of burst-forming unit–erythroid (BFU-E) and CFU–granulocyte erythrocyte, monocyte, megakaryocyte (CFU-GEMM) is shown in panel H. (I) Western blot of GSPT1 in hCD34⁺ cells treated with SJ6986 for 4 hours in culture dish as well as cells harvested from CFUs derived from hCD34⁺ cells on day 14. Signal was normalized to β-actin. (J) Flow cytometry analysis of cells from CFUs treated with vehicle.