CYP2D6 Genotyping in Natives and Immigrants from the Emilia-Romagna Region (Italy)

Meta-analysis of probability estimates of worldwide variation of CYP2D6 and CYP2C19

Extensive migration has led to the necessity of knowledge regarding the treatment of migrants with different ethnical backgrounds. This is especially relevant for pharmacological treatment, because of the significant variation between migrant groups in their capacity to metabolize drugs. For psychiatric medications, CYP2D6 and CYP2C19 enzymes are clinically relevant. The aim of this meta-analysis was to analyze studies reporting clinically useful information regarding CYP2D6 and CYP2C19 genotype frequencies, across populations and ethnic groups worldwide. To that end, we conducted a comprehensive meta-analysis using Embase, PubMed, Web of Science, and PsycINFO (>336,000 subjects, 318 reports). A non-normal metabolizer (non-NM) probability estimate was introduced as the equivalent of the sum-prevalence of predicted poor, intermediate, and ultrarapid metabolizer CYP2D6 and CYP2C19 phenotypes. The probability of having a CYP2D6 non-NM predicted phenotype was highest in Algeria (61%) and lowest in Gambia (2.7%) while the probability for CYP2C19 was highest in India (80%) and lowest in countries in the Americas, particularly Mexico (32%). The mean total probability estimates of having a non-NM predicted phenotype worldwide were 36.4% and 61.9% for CYP2D6 and CYP2C19, respectively. We provide detailed tables and world maps summarizing clinically relevant data regarding the prevalence of CYP2D6 and CYP2C19 predicted phenotypes and demonstrating large inter-ethnic differences. Based on the documented probability estimates, pre-emptive pharmacogenetic testing is encouraged for every patient who will undergo therapy with a drug(s) that is metabolized by CYP2D6 and/or CYP2C19 pathways and should be considered in case of treatment resistance or serious side effects.

An Explorative Study of CYP2D6’s Polymorphism in a Sample of Chronic Pain Patients

Background

A proper antalgic treatment is based on the use of titrated drugs to provide adequate relief and a good tolerability profile. Therapies have a variable effectiveness among subjects depending on medical and genetic conditions. CYP2D6 variations determine a different clinical response to most analgesic drugs commonly used in daily clinical practice by influencing the drugs’ pharmacokinetics. This study was a monocentric clinical trial exploring the CYP2D6 variants in 100 patients with a diagnosis of chronic pain.

Methods

DNA was extracted to evaluate the genotype and to classify patients as normal-fast (gNMs-F), normal-slow (gNMs-S), ultrarapid (gUMs), intermediate (gIMs), and poor metabolizers (gPMs) using the Activity Score (AS). Information on therapies and general side effects experienced by patients was collected. Nongenetic co-factors were evaluated to examine the discrepancy between metabolic profile predicted from genotype (gPh) and metabolic profile (phenocopying).

Results

The distribution of our data underlined the prevalence of the gNMs-F (67%), whereas gNMs-S were 24%, gIMs 6%, gPMs 3%, and no gUMs were found, resulting in 33% of patients with reduced metabolic activity. In the analyzed population sample, 86% and 56% of patients, respectively, took at least one or two drugs inhibiting in vitro activity of the CYP2D6 enzyme.

Conclusions

Over one-third of the enrolled patients showed altered CYP2D6 enzymatic metabolic activity, with a risk of phenocopying potentially due to polypharmacology.

Trial registration

ClinicalTrials.gov ID: NCT03411759.

Genetic variability of CYP2D6, CYP2B6, CYP2C9 and CYP2C19 genes across the Italian Peninsula

BACKGROUND

Environmental conditions and past migratory events may have shaped genetic heterogeneity of clinically relevant enzymes involved in the phase I metabolism of the most common therapeutic drugs.

AIM

To investigate the genetic variability of CYP2D6, CYP2B6, CYP2C19 and CYP2C9 across the Italian Peninsula, by sampling only ancestrally and geographically homogeneous individuals from northern, central and southern Italy.

SUBJECTS AND METHODS

A total of 25 SNPs were genotyped in 174 unrelated Italian individuals by means of multiplex PCR and minisequencing reactions. CYP2D6 genotypic data were used to predict phenotypes and the phylogenetic relationships among reconstructed haplotypes were represented by means of a Median Joining Network.

RESULTS

Pairwise Fisher Exact tests revealed significant differences between northern and southern Italy in the distribution of CYP2C19 genotypes, with the CYP2C19*2 allele appearing over-represented in northern Italy. Likewise, significant differences in the distribution of CYP2D6 genotypes (*4/*3, *4/*4 and *6/*4) responsible for the poor metabolizer phenotype were observed in northern with respect to both central and southern Italy.

CONCLUSIONS

The north-south structuring pattern showed by CYP2D6 and CYP2C19 underline how a deeper knowledge of the geographic distribution of alleles may improve clinical practice and help to avoid hypothetical bias in drug trials.

Development of a tetraplex PCR assay for CYP2D6 genotyping in degraded DNA samples

CYP2D6 polymorphism analysis is gaining increasing interest in forensic pharmacogenetics. Nevertheless, DNA recovered from forensic samples could be of poor quality and not suitable for long polymerase chain reaction required to type CYP2D6 gene prior to SNaPshot minisequencing analysis performed to define alleles with different enzymatic activity. We developed and validated following the guidelines of the Scientific Working Group on DNA Analysis Methods a tetraplex PCR yielding four amplicons of 597, 803, 1142, and 1659 bp encompassing the entire CYP2D6 gene to analyze eleven SNP positions by SNaPshot minisequencing. Concordance, sensitivity, and specificity were assessed. The method, applied to thirty-two forensic samples failed to amplify with long PCR, allowed the amplification of CYP2D6 gene in 62.5% of degraded samples. The new tetraplex PCR appears a suitable method for CYP2D6 analysis in forensic pharmacogenetics.

Human genetic variation of CYP450 superfamily: analysis of functional diversity in worldwide populations

AIM

The present study aimed to investigate the human genetic diversity of the CYP450 superfamily in order to identify functional interethnic differences and analyze the role of CYP450 enzymes in human adaptation.

MATERIALS & METHODS

A computational analysis of genetic and functional differences of the 57 CYP450 genes was performed using the Human Genome Diversity Project and HapMap data; comprising approximately 1694 individuals belonging to 62 human populations.

RESULTS

Twenty-six CYP450 SNPs with F-statistics significantly different than the general distribution were identified. Some showed high differentiation among human populations, suggesting that functional interethnic differences may be present. Indeed, some of these are significantly associated with drug response or disease risk. Furthermore, our data highlighted that TBXAS1 and genes in CYP3A cluster may have a role in some processes of human adaptation.

CONCLUSION

Our study provided an analysis of genetic diversity of CYP450 superfamily, identifying functional differences among ethnic groups and their related clinical phenotypes.