ST1926 treatment prolongs survival in an ATL mouse model. ATL mice treated orally with ST1926 at the dose of 30 mg/kg (A) twice daily for 2 consecutive weeks or (B) once every other day for 3 weeks. Kaplan-Meier plots of overall survival are displayed. Reported between parentheses are median survival times. ***P < .001. (C-E) Effect of 3 weeks of ST1926 treatment at 30 mg/kg every other day on (C) spleen mass, (D) circulating WBC count, and (E) organ infiltration by histopathology. Rectangles in C and D represent mean values. ***P < .001. Scores of organ infiltration after histopathology analysis are shown in E: score I, 1% to 25% leukemic cell infiltrate; score II, 26% to 50%; score III, 51% to 75%; score IV, 76% to 100%.