STAT5 inhibition abrogates IL-7–mediated T-ALL cell viability, cell growth, cell cycle progression, and proliferation. IL-7-deprived TAIL7 or primary T-ALL cells were cultured in medium, IL-7, or IL-7 plus S5i (100 µM and 150 µM, respectively). Cell viability (A-B), cell growth (C-D), cell cycle (E), and proliferation (F) were determined at 72 hours. Results are representative of at least 2 independent experiments or patients. Graphics represent average of triplicates ± SEM. **P < .01; ***P < .001.