Response of splenic disease to CCI-779 treatment. Xenografted mice with established disease (> 5% peripheral blasts) were randomized to treatment with 5 to 10 mg/kg/d of CCI-779 versus control (vehicle). Lymphoblasts in spleen in treated and untreated mice were compared at time of death. Graph represents number of blasts in millions (× 10⁶), demonstrating statistically significant difference (P < .05) in 3 of 4 patient samples. Splenic blast counts were calculated by multiplying total number of cells in spleens by percent of anti-human CD19⁺ and anti-human CD45⁺ cells as determined by FACS analysis. Error bars depict SEM.