Bestatin is a competitive aminopeptidase B inhibitor with an IC50 of 100 mg/ml for K562 cells.

benimex is a competitive aminopeptidase B inhibitor with an IC50 of 100 mg/ml for K562 cells. Proliferation of all the cell lines except KG1 was inhibited by bestatin. P39/TSU, HL60 and U937 were highly sensitive, with 50% growth inhibitory concentrations (IC50) close to the maximum serum concentration when bestatin was orally administered at 30 mg in clinical application. All cell lines except for K562 highly expressed CD13, but a clear correlation between the sensitivity to bestatin and expression of CD13 was not observed. Other aminopeptidase inhibitors such as amastatin A, arphamenine B and WM15 antibody showed no growth inhibitory effects.