High-throughput analysis of informative CYP2D6 compound haplotypes

Impact of CYP genotype and inflammatory markers on the plasma concentrations of tramadol and its demethylated metabolites and drug tolerability in cancer patients

PURPOSE

Clinical responses to oral tramadol show a large variation in cancer patients. This study aimed to evaluate the impacts of cytochrome P450 (CYP) genotype and serum inflammatory markers on the plasma concentrations of tramadol and its demethylated metabolites and drug tolerability in cancer patients.

METHODS

The predose plasma concentrations of tramadol and its demethylated metabolites were determined at day 4 or later in 70 Japanese cancer patients treated with oral tramadol. The CYP genotypes, serum interleukin-6 (IL-6) and C-reactive protein (CRP) levels, and the duration of tramadol treatment were evaluated.

RESULTS

The CYP2D6 genotype did not affect the plasma tramadol concentration. The plasma concentration of O-desmethyltramadol and its ratio to tramadol were lower in the CYP2D6 intermediate and poor metabolizer (IM + PM) group than in the normal metabolizer (NM) group (P = 0.002 and P = 0.023). The plasma concentration of N-desmethyltramadol and its ratio to tramadol were higher in the CYP2D6 IM + PM group than in the NM group (P = 0.001 and P = 0.001). The CYP2B6*6 and CYP3A5*3 alleles had no effect on the plasma concentrations of tramadol and its demethylated metabolites. The serum IL-6 and CRP levels were inversely correlated with the plasma concentration ratios of N-desmethyltramadol to tramadol and of N,O-didesmethyltramadol to O-desmethyltramadol. The serum IL-6 level was associated with the treatment duration of oral tramadol.

CONCLUSIONS

The CYP2D6 genotype but not the CYP2B6 and CYP3A5 genotypes affected the plasma concentrations of O- and N-desmethyltramadol through alteration of the tramadol metabolic pathway. The serum IL-6 level was associated with N-demethylation activity and tramadol tolerability.

Effects of Single Nucleotide Polymorphisms on Surgical and Postsurgical Opioid Requirements: A Systematic Review and Meta-Analysis

OBJECTIVES

There is great heterogeneity in the way individuals respond to medications. Inherited differences, such as single nucleotide polymorphisms (SNP), can influence the efficacy and toxicity of drugs. This meta-analysis aims to collate data from studies investigating the effect of SNPs on postoperative and/or intraoperative opioid requirements.

MATERIALS AND METHODS

A meta-analysis was conducted following PRISMA guidelines. Eligibility criteria for studies included were reporting amount of postoperative and/or intraoperative opioid used as the primary outcome and genotyping patients for SNPs in one of the following genes; OPRM1, CYP2D6, CYP3A4, CYP3A5, COMT, UGT2B7, or ABCB1. A comprehensive systematic search for articles using keywords "opioid-sensitivity," "polymorphisms," "post-operative opioid," "post-surgical opioid," "post-operative pain," and "post-surgical pain" was performed.

RESULTS

Fifty-one studies were included. Individuals homozygous for AA at the OPRMI (rs1799971) polymorphisms required less postsurgical opioid compared with those homozygous for GG (Hedges g, -0.270; 95% confidence interval, -0.433 to -0.108; P=0.001). Polymorphisms in CYP2D6, CYP3A4, CYP3A5, COMT, UGT2B7, and ABCB1 did not affect opioid requirements.

DISCUSSION

Investigation of single changes in 1 gene can only yield limited information regarding genetic effects on opioid requirements. Rapid development of whole genome sequencing enables information on all genetic modifications that may affect analgesic response to be collected. The information collected must include data on the individual's metabolic enzymes, as well as information on drug receptors and enzymes responsible for drug degradation, so that a personal profile can be built up which will predict individual response to drugs, and guide clinicians on the type and dosage of drug to use.

High frequency of CYP2D6 ultrarapid metabolizer genotypes in an Ashkenazi Jewish population from Argentina

A twofold higher frequency of CYP2D6 ultrarapid metabolizers (estimated from genotype: gUMs) was reported among Ashkenazi Jews (AJ) living in New York (USA) than in other North American Caucasians, which might be important to guide the prescription for CYP2D6 substrates in AJ communities around the world. This study was aimed to determine whether the high frequency of CYP2D6 gUMs described in AJ from USA was replicated in AJ from Argentina when compared with other multiethnic admixture Argentines (GA). The frequency of the most common allelic variants and of CYP2D6 gUMs (>2 active genes) and poor metabolizers (0 active genes, gPMs) was also compared among the studied Argentine populations. CYP2D6 genotyping was performed in 173 AJ and 246 GA DNA samples of unrelated donors from the metropolitan area of Buenos Aires. CYP2D6 alleles (*2, *3, *4, *5, *6, *10, *17, *35, *41 and multiple copies), genotypes and functional phenotype frequencies were determined. The frequencies of gUMs and gPMs in AJ from Argentina were 11.5% and 5.2%, respectively, whereas in GA, the frequencies of gUM and gPMs were 6.5% and 4.9%, respectively. Comparisons between AJ and GA showed that gUMs frequencies were twofold higher (P<0.05) in AJ than GA. CYP2D6*35 allele was more frequent in GA than AJ, whereas CYP2D6*41 and *1xN were more frequent in AJ than in GA (P<0.05). This study supports the previously reported high frequency of gUMs on another Ashkenazi population in New York. The present findings also support the interethnic variability of CYP2D6 genetic polymorphism in the overall Argentine population.

CYP2D6 genotype in relation to hot flashes as tamoxifen side effect in a Dutch cohort of the tamoxifen exemestane adjuvant multinational (TEAM) trial

In tamoxifen-treated breast cancer patients the occurrence of hot flashes may be associated with effective estrogen receptor antagonism dependent on genetic variations of metabolic enzymes and the estrogen receptor. Early breast cancer patients who were randomized to receive tamoxifen, followed by exemestane within the tamoxifen exemestane adjuvant multinational trial were genotyped for five CYP2D6 alleles. CYP2D6 genotypes and phenotypes were related to the occurrence of hot flashes as adverse event during the first year of tamoxifen use (primary aim) and the time to the occurrence of hot flashes as AE during the complete time on tamoxifen (secondary aim). In addition, exploratory analyses on 22 genetic variants of other metabolic enzymes and two common polymorphisms in the estrogen receptor-1 were performed. No association was found between the CYP2D6 genotype/phenotype or any other genetic variant and hot flashes during the first year. Only higher age was related to a lower incidence of hot flashes in the first year (adjusted odds ratio 0.94, 95 % CI 0.92-0.96; p < 0.001). The ESR1 PvuII XbaI CG haplotype was associated with the time to the occurrence of hot flashes during the complete time on tamoxifen (CG/CG vs. CG/other + other/other: adjusted hazard ratio 0.49, 95 % CI 0.25-0.97; p = 0.04). In conclusion, the CYP2D6 genotypes and phenotypes were not associated with the occurrence of hot flashes. Common polymorphisms in the estrogen receptor-1 might predict hot flashes as common tamoxifen side effect, although this finding needs replication.

Rapid genotyping of CYP2D6, CYP2C19 and TPMT polymorphisms by primer extension reaction in a dipstick format

In recent years an increasing amount of interest has been directed at the study and routine testing of polymorphisms responsible for variations in drug metabolism. Most of the current methods involve either time-consuming electrophoresis steps or specialized and expensive equipment. In this context, we have developed a rapid, simple and robust method for genotyping of CYP2D6*3, CYP2D6*4, CYP2C19*2, CYP2C19*3 and TPMT*2 single nucleotide polymorphisms (SNP). Genomic DNA is isolated from whole blood and the segments that span the SNP of interest are amplified by PCR. The products are subjected directly (without purification) to two primer extension (PEXT) reactions (three cycles each) using normal and mutant primers in the presence of biotin-dUTP. The PEXT primers contain a (dA)(30) segment at the 5' end. The PEXT products are detected visually by a dry-reagent dipstick-type assay in which the biotinylated extension products are captured from immobilized streptavidin on the test zone of the strip and detected by hybridization with oligo(dT)-functionalized gold nanoparticles. Patient samples (76 variants in total) were genotyped and the results were fully concordant with those obtained by direct DNA sequencing.

Rapid detection of common cytochrome P450 2D6 alleles in Caucasians

CYP2D6 is a highly polymorphic enzyme that mediates the metabolism of around 20% of all currently prescribed drugs. Genetic variability within CYP2D6 results in poor (PM), intermediate (IM), extensive (EM) and ultra-rapid metabolisers (UM) of CYP2D6 substrates. Here we describe an assay which is able to detect the major PM (CYP2D6*3, *4, *5, *6), IM (CYP2D6*9, *10, *41) and UM (CYP2D6*nxn) alleles found in Caucasians. This assay is performed in two stages. The first stage is a multiplex long-range PCR which is used to simultaneously screen for whole gene deletions and duplications while isolating CYP2D6 from the CYP2D gene cluster to avoid pseudogene contamination. In the second stage, individuals with one or more copies of CYP2D6 are genotyped for PM and IM alleles using a two-tube multiplex Amplification Refractory Mutation System (ARMS). The specificity and reliability of the multiplex long-range PCR and subsequent ARMS were confirmed using a panel of positive controls that had been previously validated by PCR-RFLPs and DNA sequencing. This two-stage assay offers a robust and cheap alternative to many currently available CYP2D6 genotyping approaches. Our entire assay, once patient DNA has been extracted, can be run within 7 h using 10 microl PCRs.