A substantial subset of primary AML displays primary resistance to MDM2 inhibitors. A total of 109 (MI219) and 60 (MI-63) AML samples were enriched to more than 90% blast purity through negative selection and incubated for 40 hours with various concentrations of either MI-219 or MI-63. Samples were prepared for annexin V and PI staining and analyzed by flow cytometry, and the residual live and nonapoptotic cell fraction was calculated for each concentration by comparison with the untreated control aliquots. (A) MI-219 assay results. Red represents p53 sequence mutants; green, cases with absent p53 mRNA; and black, wild-type p53 status. (B) MI-63 assay results. Red represents p53 sequence mutants; green, cases with absent p53 mRNA; and black, wild-type p53 status.