In vivo assessment of the metabolic activity of CYP2D6 diplotypes and alleles

Daniel L. Hertz, Anna C. Snavely, Howard L. McLeod, Christine M. Walko, Joseph G. Ibrahim, Steven Anderson, Karen E. Weck, Gustav Magrinat, Oludamilola Olajide, Susan Moore, Rachel Raab, Daniel R. Carrizosa, Steven Corso, Garry Schwartz, Jeffrey M. Peppercorn, James P. Evans, David R. Jones, Zeruesenay Desta, David A. Flockhart, Lisa A. CareyWilliam J. Irvin

Research output: Contribution to journalArticle

27 Scopus citations


Aims A prospectively enrolled patient cohort was used to assess whether the prediction of CYP2D6 phenotype activity from genotype data could be improved by reclassification of diplotypes or alleles. Methods Three hundred and fifty-five patients receiving tamoxifen 20 mg were genotyped for CYP2D6 and tamoxifen metabolite concentrations were measured. The endoxifen: N-desmethly-tamoxifen metabolic ratio, as a surrogate of CYP2D6 activity, was compared across four diplotypes (EM/IM, EM/PM, IM/IM, IM/PM) that are typically collapsed into an intermediate metabolizer (IM) phenotype. The relative metabolic activity of each allele type (UM, EM, IM, and PM) and each EM and IM allele was estimated for comparison with the activity scores typically assigned, 2, 1, 0.5 and 0, respectively. Results Each of the four IM diplotypes have distinct CYP2D6 activity from each other and from the EM and PM phenotype groups (each P < 0.05). Setting the activity of an EM allele at 1.0, the relative activities of a UM, IM and PM allele were 0.85, 0.67 and 0.52, respectively. The activity of the EM alleles were statistically different (P < 0.0001), with the CYP2D62 allele (scaled activity = 0.63) closer in activity to an IM than an EM allele. The activity of the IM alleles were also statistically different (P = 0.014). Conclusion The current systems for translating CYP2D6 genotype into phenotype are not optimally calibrated, particularly in regards to IM diplotypes and the2 allele. Additional research is needed to improve the prediction of CYP2D6 activity from genetic data for individualized dosing of CYP2D6 dependent drugs.

Original languageEnglish (US)
Pages (from-to)1122-1130
Number of pages9
JournalBritish Journal of Clinical Pharmacology
Issue number5
StatePublished - Nov 1 2015


  • CYP2D6
  • N-desmethyl-tamoxifen
  • activity score
  • endoxifen
  • pharmacogenetic
  • tamoxifen

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)

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    Hertz, D. L., Snavely, A. C., McLeod, H. L., Walko, C. M., Ibrahim, J. G., Anderson, S., Weck, K. E., Magrinat, G., Olajide, O., Moore, S., Raab, R., Carrizosa, D. R., Corso, S., Schwartz, G., Peppercorn, J. M., Evans, J. P., Jones, D. R., Desta, Z., Flockhart, D. A., ... Irvin, W. J. (2015). In vivo assessment of the metabolic activity of CYP2D6 diplotypes and alleles. British Journal of Clinical Pharmacology, 80(5), 1122-1130.