(–)BI97D6 effectively kills primary AML myeloblasts from refractory patients. (A) (–)BI97D6 IC₅₀ values in primary AML samples. Fresh mononuclear cells from AML patients were isolated and incubated with (–)BI97D6 for 48 hours. Calcusyn software was used to calculate the IC₅₀ values based on live cell numbers (Annexin V⁻/PI⁻). Patient information is provided in Table 1. (B) Protein expression measured by quantitative immunoblot was plotted against the corresponding (–)BI97D6 IC₅₀ values of patient samples (n = 12). No significant correlations were observed between IC₅₀ values and the expression levels of Bcl-2, Bcl-xL, or Mcl-1 (Spearman’s rank correlation). (C) The IC₅₀ values of (–)BI97D6 against refractory or nonrefractory primary AML samples. There is no significant difference in the median IC₅₀ values (Mann-Whitney test).