Clinical responses in patients with p53 mutations, deletions, or both were noted in 6 (40%) of 15 versus 4 (19%) of 21 of patients without. The median response duration for this subset of patients was 8 months (range, 3-17 months). These data suggest that alemtuzumab may be an effective therapy for patients with CLL with p53 mutations or deletions...Clinical or laboratory features predicting response to alemtuzumab...Outside of patients with del(17)(p13.1) or p53 mutations, only those patients with del(11)(q22.3) had sufficient numbers to examine the effect of alemtuzumab on response.