A validated CYP3A genotype classification system allows clustering patients into poor, intermediate and extensive metabolizer phenotypes. However, substantial overlap exists between the clusters. A rare CYP3A4 allele, named CYP3A4∗20 (rs67666821), has been specifically described in the Spanish population. The authors investigated the relevance of CYP3A4∗20 testing to see if the above-mentioned metabolic CYP3A classification system can be improved. In a cohort of 204 kidney transplant recipients, one male patient carrying a CYP3A4∗20 allele was detected. This patient was receiving very low doses of tacrolimus to maintain therapeutic levels from day 7 onward when compared with the majority of the patients. These data suggest that this patient should be regarded as a CYP3A-poor metabolizer.

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doi.org/10.2217/pgs-2017-0301, hdl.handle.net/1765/105139
Department of Internal Medicine

Lloberas, N. (Nuria), Hesselink, D., van Schaik, R., Grinyo, J., Colom, H. (Helena), van Gelder, T., & Elens, L. (2018). Detection of a rare CYP3A4 variant in a transplant patient characterized by a tacrolimus poor metabolizer phenotype. Pharmacogenomics, 19(4), 305–310. doi:10.2217/pgs-2017-0301