An inhibitor of the Lin28/let-7 interaction (IC50 = 8 μM in a competition ELISA); increases levels of endogenous let-7 miRNAs and decreases Lin28 expression in a dose-dependent manner in mESCs; inhibits clonogenic growth of 22Rv1, PC3, DU145, and Huh7 cancer cells and decreases tumor-sphere formation by 22Rv1 and Huh7 cells in vitro