EIF4EBP1 and plasmacytoma: Additionally, levels of phospho-4EBP1 (Thr 37/46) were also lower in MM.1S plasmacytomas of two out of three mice treated with PIM-Pd for two consecutive days as compared to those from mice treated with the vehicle (control, C), PIM447 alone or the Pd doublet (Figure 3C).