Impact of CYP3A5*3 and CYP2C8-HapC on paclitaxel/carboplatin-induced myelosuppression in patients with ovarian cancer.

The influence of genetic variants on paclitaxel-induced toxicity is of considerable interest for reducing adverse drug reactions. Recently, the genetic variants CYP2C8*3, CYP2C8-HapC, and CYP3A5*3 were associated with paclitaxel-induced neurotoxicity. We, therefore, investigated the impact of CYP2C8-HapC and CYP3A5*3 on paclitaxel/carboplatin-induced myelosuppression and neurotoxicity. Thirty-three patients from a prospective pharmacokinetics study were genotyped using pyrosequencing. Patients with variant alleles of CYP2C8-HapC were found to have significantly lower nadir values of both leukocytes and neutrophils (p < 0.05) than patients with the wild-type genotype. CYP3A5*3/*1 patients were shown to have borderline, significantly lower nadir values of leukocytes (p = 0.07) than *3/*3 patients. Combining the two genotypes resulted in a significant correlation with both leukopenia and neutropenia (p = 0.01). No effect of these genetic variants on neurotoxicity could be shown in this rather small study, but their importance for paclitaxel-induced toxicity could be confirmed.