Relationship between initial CLL count and alemtuzumab blood concentration: intravenous study. The numbers of CLL cells in the blood directly before intravenous therapy are plotted against the peak concentration of alemtuzumab measured directly after the first 30-mg dose (•). In 8 patients the concentration was below the limit of quantitation, and these have all been plotted at an arbitrary level of 0.25 μg/mL (○). Pearson correlation coefficient for log (initial CLL count) versus log (alemtuzumab concentration) was –0.44, P = .01.