Severe Vincristine-Induced Neuropathic Pain in a CYP3A5 Nonexpressor With Reduced CYP3A4/5 Activity: Case Study.

Peripheral neuropathy is a frequent vincristine-induced adverse effect. Vincristine is a substrate of P-glycoprotein and is metabolized by the cytochrome P-450 (CYP) 3A5 and 3A4 isoforms, with CYP3A5 contributing to 75% of the intrinsic clearance of vincristine. Alterations in the function of these proteins may lead to an increase in vincristine toxicity. CYP3A5 nonexpressor status has been associated with vincristine-induced peripheral neuropathy. The severity of neuropathy has been reported to be inversely correlated to vincristine metabolite concentrations. Recently, the presence of a mutation in the CEP72 gene, which encodes for a protein involved in microtubule formation, has also been associated with vincristine-induced peripheral neuropathy. However, a clear correlation between genetic polymorphisms and vincristine toxicity has not been established.Here we report the case of a 21-year old patient in whom severe neuropathic pain developed after vincristine treatment.The patient was a CYP3A5 nonexpressor and presented with reduced CYP3A4/5 functional activity, a likely reason for the occurrence of the adverse event, as genotyping showed that his status was wild type for the ABCB1 and CEP72 genes.CYP phenotype and genotype may explain the occurrence of severe neuropathy in some patients treated with vincristine.