(A) Approximately 3 million MDA‐MB‐468 LN cells were injected into the flank region of nude mice, and once the tumors reached ~ 50 mm3, the mice were treated either daily or twice a week for 21 days with KU711, KU758, or 17‐AAG. Tumor volumes were measured twice weekly and plotted. Six mice from each group were used, and the mean ± SE values were plotted. Treatment differences with respect to tumor size were assessed using two‐way ANOVA with a post hoc nonparametric test with P < 0.05 set as statistically significant. (B) Toxicity analysis using histology. At the end of the treatment, tissues were collected for toxicity analysis. The tissues were stained with H&E, and toxicity was analyzed by a pathologist. KU711, which demonstrated the best antitumor efficacy in vivo, was not toxic compared to 17‐AAG and KU758. (C) Kaplan–Meier survival curve. * represents P ≤ 0.05 and *** represents P ≤ 0.001.