Cyclophosphamide for CLL: to be or not CYP2B activated?

In this issue of Blood, Johnson et al1 report their findings of the hepatic cytochrome P450 (CYP) enzyme gene polymorphisms in patients with chronic lymphocytic leukemia (CLL) treated with fludarabine and cyclophosphamide (FC) within a clinical trial. Patients with at least one *6 allele had significantly lower rates of complete response and also less toxicity than patients with *1/*1 alleles, as well as a trend of shorter progression-free survival (PFS). Albeit indirect, this is the first indication in a controlled clinical trial of a significant impact of cyclophosphamide (CPA) bioactivation in CLL and a step toward tailored therapy of cancer. Copyright © 2011 by The American Society of Hematology; all rights reserved.