MDR1 pharmacogenetics: frequency of the C3435T mutation in exon 26 is significantly influenced by ethnicity

ABCB1 Polymorphism Is Associated with Higher Carbamazepine Clearance in Children

The aim of our study was to investigate the role of ABCB1 polymorphism in the pharmacokinetics of carbamazepine (CBZ) in children. The study enrolled 47 Serbian pediatric epileptic patients on CBZ treatment. Genotyping for ABCB1 1236C Collapse

Key Words

• ABCB1
• carbamazepine
• children
• genetic polymorphism
• population pharmacokinetics

Collapse

MESH Headings Collapse

Grants

• 175007 and 175056 the Ministry of Science and Technology of the Republic of Serbia
• 07/11 Faculty of Medical Sciences, University of Kragujevac, Serbia

Collapse

Affiliation(s)

Natasa Djordjevic Department of Pharmacology and Toxicology, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34 000 Kragujevac, Serbia; (J.R.M.); (S.J.); (D.M.)
Jelena Cukic Public Health Institute, Nikole Pasica 1, 34 000 Kragujevac, Serbia; (J.C.); (D.B.)
Dragana Dragas Milovanovic College of Professional Health Studies, Cara Dusana 254, 11 080 Belgrade, Serbia;
Marija Radovanovic Department of Pediatrics, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34 000 Kragujevac, Serbia; (M.R.); (S.O.)
Ivan Radosavljevic Department of Surgery, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34 000 Kragujevac, Serbia;
Jelena Vuckovic Filipovic Department of Internal Medicine, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34 000 Kragujevac, Serbia;
Slobodan Obradovic Department of Pediatrics, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34 000 Kragujevac, Serbia; (M.R.); (S.O.)
Dejan Baskic Public Health Institute, Nikole Pasica 1, 34 000 Kragujevac, Serbia; (J.C.); (D.B.) Department of Microbiology, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34 000 Kragujevac, Serbia
Jasmina R. Milovanovic Department of Pharmacology and Toxicology, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34 000 Kragujevac, Serbia; (J.R.M.); (S.J.); (D.M.)
Slobodan Jankovic Department of Pharmacology and Toxicology, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34 000 Kragujevac, Serbia; (J.R.M.); (S.J.); (D.M.)
Dragan Milovanovic Department of Pharmacology and Toxicology, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34 000 Kragujevac, Serbia; (J.R.M.); (S.J.); (D.M.)

Collapse

Collaborators Collapse

Variability in plasma rifampicin concentrations and role of SLCO1B1, ABCB1, AADAC2 and CES2 genotypes in Ethiopian patients with tuberculosis

BACKGROUND

Rifampicin, a key drug against tuberculosis (TB), displays wide between-patient pharmacokinetics variability and concentration-dependent antimicrobial effect. We investigated variability in plasma rifampicin concentrations and the role of SLCO1B1, ABCB1, arylacetamide deacetylase (AADAC) and carboxylesterase 2 (CES-2) genotypes in Ethiopian patients with TB.

METHODS

We enrolled adult patients with newly diagnosed TB (n = 119) who had received 2 weeks of rifampicin-based anti-TB therapy. Venous blood samples were obtained at three time points post-dose. Genotypes for SLCO1B1 (c.388A > G, c.521T > C), ABCB1 (c.3435C > T, c.4036A > G), AADACc.841G > A and CES-2 (c.269-965A > G) were determined. Rifampicin plasma concentration was quantified using LC-MS/MS. Predictors of rifampicin Cmax and AUC0-7 h were analysed.

RESULTS

The median rifampicin Cmax and AUC0-7 were 6.76 µg/mL (IQR 5.37-8.48) and 17.05 µg·h/mL (IQR 13.87-22.26), respectively. Only 30.3% of patients achieved the therapeutic efficacy threshold (Cmax>8 µg/mL). The allele frequency for SLCO1B1*1B (c.388A > G), SLCO1B1*5 (c.521T > C), ABCB1 c.3435C > T, ABCB1c.4036A > G, AADAC c.841G > A and CES-2 c.269-965A > G were 2.2%, 20.2%, 24.4%, 14.6%, 86.1% and 30.6%, respectively. Sex, rifampicin dose and ABCB1c.4036A > G, genotypes were significant predictors of rifampicin Cmax and AUC0-7. AADACc.841G > A genotypes were significant predictors of rifampicin Cmax. There was no significant influence of SLCO1B1 (c.388A > G, c.521T > C), ABCB1c.3435C > T and CES-2 c.269-965A > G on rifampicin plasma exposure variability.

CONCLUSIONS

Subtherapeutic rifampicin plasma concentrations occurred in two-thirds of Ethiopian TB patients. Rifampicin exposure varied with sex, dose and genotypes. AADACc.841G/G and ABCB1c.4036A/A genotypes and male patients are at higher risk of lower rifampicin plasma exposure. The impact on TB treatment outcomes and whether high-dose rifampicin is required to improve therapeutic efficacy requires further investigation.

Cardiac PET Imaging of ATP Binding Cassette (ABC) Transporters: Opportunities and Challenges

Adenosine triphosphate binding cassette (ABC) transporters are a broad family of membrane protein complexes that use energy to transport molecules across cells and/or intracellular organelle lipid membranes. Many drugs used to treat cardiac diseases have an affinity for these transporters. Among others, P-glycoprotein (P-gp) plays an essential role in regulating drug concentrations that reach cardiac tissue and therefore contribute to cardiotoxicity. As a molecular imaging modality, positron emission tomography (PET) has emerged as a viable technique to investigate the function of P-gp in organs and tissues. Using PET imaging to evaluate cardiac P-gp function provides new insights for drug development and improves the precise use of medications. Nevertheless, information in this field is limited. In this review, we aim to examine the current applications of ABC transporter PET imaging and its tracers in the heart, with a specific emphasis on P-gp. Furthermore, the opportunities and challenges in this novel field will be discussed.

Single-nucleotide polymorphisms in ABC drug transporters alter expression and circulating tenofovir in healthy South African women exposed to pre-exposure prophylaxis

Aim: We investigated if single-nucleotide polymorphisms (SNPs) in ATP-binding cassette (ABC) drug transporters alter gene expression and tenofovir disposition in South African women taking Truvada® for HIV prevention. Materials & methods: In 393 women, real-time PCR was used to determine the associations between six SNPs in ABC transporter genes, mRNA expression and circulating-tenofovir. Results: Univariable and multivariable analyses showed that CT and TT relative to CC genotypes for the ABCC4(3463C/T) SNP had significantly higher tenofovir levels. In contrast, the AA genotype for the ABCC4(4976A/G) SNP showed significantly less tenofovir, while mRNA expression was increased. Conclusion: SNPs in the ABCC4 gene may differentially affect gene expression and circulating tenofovir. Their impact may inform on low pre-exposure prophylaxis efficacy and discern effective drugs in clinical trials of African women enriched for certain genotypes.

Cannabis Pharmacogenomics: A Path to Personalized Medicine

Cannabis and related compounds have created significant research interest as a promising therapy in many disorders. However, the individual therapeutic effects of cannabinoids and the incidence of side effects are still difficult to determine. Pharmacogenomics may provide the answers to many questions and concerns regarding the cannabis/cannabinoid treatment and help us to understand the variability in individual responses and associated risks. Pharmacogenomics research has made meaningful progress in identifying genetic variations that play a critical role in interpatient variability in response to cannabis. This review classifies the current knowledge of pharmacogenomics associated with medical marijuana and related compounds and can assist in improving the outcomes of cannabinoid therapy and to minimize the adverse effects of cannabis use. Specific examples of pharmacogenomics informing pharmacotherapy as a path to personalized medicine are discussed.

Pharmacogenetic Study of the Impact of ABCB1 Single Nucleotide Polymorphisms on the Response to Cyclosporine in Psoriasis Patients

Psoriasis is a chronic, T cell-mediated skin disease affecting 2-3% of the Caucasian population. Cyclosporine A is a calcineurin inhibitor that acts selectively on T cells. The cyclosporine A treatment response has been suggested to be modulated by single-nucleotide polymorphisms (SNPs) in the ABCB1 gene. The aim of this research was to evaluate the effect of ABCB1 genetic variants that could affect the response to a cyclosporine treatment in Russian psoriasis patients with the ABCB1 genotype status. The ABCB1 T-129C, G1199A, C1236T, G2677T/A and C3435T SNPs in the 168 patients with psoriasis were genotyped by PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) and TaqMan SNP genotyping assays. The ABCB1 C1236T, G2677T/A and C3435T SNPs were significantly associated with a negative response to cyclosporine therapy. A very strong association was evident for the C3435T SNP in the ABCB1 gene in the allele, dominant and recessive models (OR = 2.58, OR = 4.01, OR = 2.50, respectively). ABCB1 C1236T and G2677T/A polymorphisms were significantly associated with a negative response to the cyclosporine therapy in the codominant, dominant and recessive models (p ˂ 0.05). Additionally, the haplotype analysis identified that the TGC haplotype is significantly associated with a negative response to cyclosporine therapy in psoriasis patients (p ˂ 0.05). The current study to the best of our knowledge is the first of its kind to be performed in the Russian population. In conclusion, the present results suggest an association between the ABCB1 genetic variants and unresponsiveness to cyclosporine in the Russian population. Further, larger studies are necessary to confirm our findings and replicate them in various ethnic populations before its implementation in the clinical practice.

Pharmacogenomics of drug transporters for antiretroviral long-acting pre-exposure prophylaxis for HIV

The use of antiretrovirals (ARVs) as oral, topical, or long-acting pre-exposure prophylaxis (PrEP) has emerged as a promising strategy for HIV prevention. Clinical trials testing Truvada® [tenofovir disoproxil fumarate (TDF)/tenofovir (TFV) and emtricitabine (FTC)] as oral or topical PrEP in African women showed mixed results in preventing HIV infections. Since oral and topical PrEP effectiveness is dependent on adequate drug delivery and availability to sites of HIV infection such as the blood and female genital tract (FGT); host biological factors such as drug transporters have been implicated as key regulators of PrEP. Drug transporter expression levels and function have been identified as critical determinants of PrEP efficacy by regulating PrEP pharmacokinetics across various cells and tissues of the blood, renal tissues, FGT mucosal tissues and other immune cells targeted by HIV. In addition, biological factors such as genetic polymorphisms and genital inflammation also influence drug transporter expression levels and functionality. In this review, drug transporters and biological factors modulating drug transporter disposition are used to explain discrepancies observed in PrEP clinical trials. This review also provides insight at a pharmacological level of how these factors further increase the susceptibility of the FGT to HIV infections, subsequently contributing to ineffective PrEP interventions in African women.

Association between G2677T/A polymorphism in ABCB1 gene and the risk of drug resistance epilepsy: An updated systematic review and meta-analysis

PURPOSE

Epilepsy is a common serious brain condition characterized by the abnormal electrical activity of neurons. In most cases, epileptic patients respond to antiepileptic drugs. Approximately, one-third of patients prove medically intractable. The ABCB1 gene is a superfamily of ATP-binding cassette (ABC) transporters that encode a drug-transport protein, lead to cells and organs protects and eliminates toxic agents. We performed this meta-analysis to assess the association between G2677T/A in the ABCB1 gene and the risk of drug resistance in epileptic patients.

METHODS

Two online libraries (PubMed and Scopus) were used to identify studies that report the relationship between G2677T/A polymorphism in the MDR1 gene and the risk of antiepileptic drug resistance. The meta-analysis was performed using Review Manager 5.3 software. The pooled odds ratios and 95 % confidence intervals (CIs) were calculated using a random or fixed effects model according to the heterogeneity between studies.

RESULTS

A total of 33 eligible studies were included in this meta-analysis which 4192 patients were drug-resistant and 5079 patients were drug-responsive. As a result, a significant association was observed in overall population for the genetic model GG+GA vs AA (OR with 95 % CI = 0,56 [0.34,0.93]; P = 0.02). The subgroup ethnicity analysis showed a significant decrease in the risk of AEDs resistance in the Caucasian population.

CONCLUSION

In conclusion, our analysis demonstrates that G2677T/A polymorphism in the ABCB1 gene decreases the risk of drug resistance. More studies are needed in the different ethnic groups to clarify the role of polymorphism in AEDs resistance.

Pharmacogenomics Informs Cardiovascular Pharmacotherapy

Precision medicine exemplifies the emergence of personalized treatment options which may benefit specific patient populations based upon their genetic makeup. Application of pharmacogenomics requires an understanding of how genetic variations impact pharmacokinetic and pharmacodynamic properties. This particular approach in pharmacotherapy is helpful because it can assist in and improve clinical decisions. Application of pharmacogenomics to cardiovascular pharmacotherapy provides for the ability of the medical provider to gain critical knowledge on a patient's response to various treatment options and risk of side effects.

Prevalence of ABCB1 3435C>T polymorphism in the Cuban population

OBJECTIVES

ABCB1 gene polymorphisms can modify P-glycoprotein function with clinical consequences.

METHODS

The 3435C>T polymorphism prevalence was analyzed using oligonucleotide probes and next-generation sequencing in 421 unrelated healthy individuals living in Cuba. Data were stratified by gender, ethnic background and residence. The genotype and allelic frequencies were determined.

RESULTS

The genotype distribution met the Hardy-Weinberg equilibrium assumption. The allelic frequency was 63.5% for the 3435C variant. The genotype frequencies were 41.1% for CC, 44.9% for CT and 14.0% for TT. The allele and genotype distributions differed between individuals living in La Habana and Santiago de Cuba (p<0.05) when ethnic background was analyzed. The allelic distribution was similar among Admixed and Black subjects, and they differed from Caucasians. The CC genotype was equally distributed among Admixed and Black subjects, and they differed from Caucasians. The TT genotype frequency differed between Caucasians and Admixed. The CT genotype was distributed differently among the three groups. Similar distribution was obtained in Brazilians, whereas some similarities were observed in African, Spanish and Chinese populations, consistent with the mixed Cuban ethnic origin.

CONCLUSIONS

This is the first report on allele and genotype frequencies of the 3435C>T polymorphism in Cuba, which may support personalized medicine programs.

Predictive association of ABCB1 C3435T genetic polymorphism with the efficacy or safety of lopinavir and ritonavir in COVID-19 patients

Lopinavir and ritonavir are substrates of permeability glycoprotein encoded by ABCB1. The efficacy and safety of these drugs is unknown in COVID-19 patients affected by ABCB1 genetic variability. Patients carrying one or two copies of the ABCB1 C3435T were predictively considered as risk phenotypes. It was predicted that risk phenotypes due to carrying either one or two copies of ABCB1 C3435T were highly prevalent in Europe (76.8%; 95% CI: 75-78), followed by America (67%; 95% CI: 65-69), Asia (63.5%; 95% CI: 62-65) and Africa (41.4%; 95% CI: 37-46), respectively. It is hypothesized that a considerable proportion of COVID-19 patients treated with lopinavir/ritonavir inheriting ABCB1 C3435T genetic polymorphism may be predisposed to either therapeutic failure or toxicity.

ABCB1 polymorphism in clopidogrel-treated Montenegrin patients

Clopidogrel is an antiplatelet drug that displays significant interindividual variability in treatment response. Its bioavailability depends on the function of P-glycoprotein (P-gp), which is coded by a highly polymorphic ABCB1 gene. Thus, the aim of this study was to investigate the effect of ABCB1 genetic polymorphism on clopidogrel efficacy and safety and to determine the frequency distribution of its most common single nucleotide polymorphisms (SNPs) in 106 Montenegrin cardiology patients. Clopidogrel efficacy and safety were followed up during 1 year after hospitalization, with the lack of efficacy and adverse drug reactions observed in 11 (10.4%) and 8 patients (7.5%), respectively. Genotyping for ABCB1 SNPs rs1128503 (1236C > T), rs2032582 (2677G > A/T), and rs1045642 (3435C > T) was performed by the real-time PCR method, and the variant alleles were detected with the frequencies of 42.9, 44.8, and 52.8%, respectively. No significant association was observed between any of the examined genotypes and clopidogrel efficacy (p = 0.253) or safety (p = 0.424). Due to small sample size, co-treatment with other drugs, and other genetic factors not taken into account, we believe the absence of correlation between ABCB1 genotypes and indicators of clopidogrel efficacy and safety in this study should be apprehended conditionally, and that larger and better-controlled studies are warranted.

Pharmacogenetics of tamoxifen therapy in Asian populations: from genetic polymorphism to clinical outcomes

BACKGROUND

Compared with western countries, Asian breast cancer patients have unique pathological and biological characteristics. Most of them are premenopausal women with HR positive. Tamoxifen as the first-line drug for premenopausal women with HR+ is involved in multiple enzymes and transporters during metabolizing and transporting process. Variants that cause decreased or inactive gene products leading to abnormal responses in tamoxifen therapy have well been studied in western countries, whereas such information is much less reported in Asian populations.

OBJECTIVE

In order to elucidate the relationship between genetic variants and tamoxifen-induced individual drug reactions in different Asian populations and further identify genotypes/phenotypes with potential therapeutic significance.

METHODS

We reviewed the frequencies of genetic variants in major enzymes and transporter genes involved in the metabolism and transport of tamoxifen across Asian populations as well as significant correlations between genotypes/metabolic phenotypes and metabolites concentrations or BC clinical outcomes.

RESULTS

Significant inter-ethnic differences in allele frequencies was found among Asian populations, such as CYP2D6*4, *10, *41, CYP2C9*2, ABCB1 C3435T and SLCO1B1*5, and CYP2D6*10/*10 is the most common genotype correlated with adverse clinical outcomes. Moreover, we summarized the barriers and controversies of implementing pharmacogenetics in tamoxifen therapy and concluded that more population-specific pharmacogenetic studies are needed in the future.

CONCLUSION

This review revealed more systematic pharmacogenomics of genes involved in the metabolism and transport besides CYP2D6, are required to optimize the genotyping strategies and guide the personalized tamoxifen therapy in Asian populations.

The pharmacogenetics of opioid treatment for pain management

BACKGROUND

Opioids are widely used as an analgesic for the treatment of moderate to severe pain. However, there are interindividual variabilities in opioid response. Current evidence suggests that these variabilities can be attributed to single nucleotide polymorphisms in genes involved in opioid pharmacodynamics and pharmacokinetics. Knowledge of these genetic factors through pharamacogenetic (PGx) testing can help clinicians to more consistently prescribe opioids that can provide patients with maximal clinical benefit and minimal risk of adverse effects.

AIM

The research outlined in this literature review identifies variants involved in opioid PGx, which may be an important tool to achieving the goal of personalized pain management.

RESULTS

Cytochrome P450 (CYP) 2D6, CYP3A4, CYP3A5, catechol-o-methyltransferase (COMT), adenosine triphosphate binding cassette transporter B1 (ABCB1), opioid receptor mu 1 (OPRM1), and opioid receptor delta 1 (OPRD1) are all important genes involved in opioid drug response, side effect profile and risk of dependence; these are important genetic factors that should be included in potential opioid PGx tests for pain management.

CONCLUSIONS

Employing a PGx-guided strategy for prescribing opioids can improve response rate, reduce side effects and increase adherence to treatment plans for pain; more research is needed to explore opioid-related PGx factors for the development and validation of an opioid genetic panel. Optimal prescriptions could also provide healthcare payers with beneficial savings, while reducing the risk of propagating the current opioid crisis.

Adult liver transplantation using pediatric donor livers after cardiac or brain death: A report of three cases

The present study reports on the experience at Jiangxi Provincial People's Hospital (Nanchang, China) with liver transplantation in adults using pediatric donor livers, including indications, technique and results. A total of three cases of liver transplantation performed between April 2008 and May 2016 were retrospectively reviewed. Liver procurement and trimming, recipient selection, surgical tips, prevention and treatment of small-for-size syndrome, selection of immunosuppressive regimens, prevention and treatment of vascular complications and anticoagulant therapy were discussed. The three pediatric donors were 8, 8 and 10 years old. The three recipients were confirmed to have primary liver cancer. In recipient 1 (female; age, 39 years), jaundice persisted in the recipient after the liver transplantation. A reduced dose of FK506 was then given to gradually decrease the total bilirubin level to the normal range. Recipient 1 recovered and was discharged from hospital; however, the patient died of liver cancer recurrence and bone metastasis 6 years post-transplantation. In recipient 2 (male; age, 56 years), the recipient experienced sudden abdominal distension on postoperative day 7. The patient's clotting time was prolonged and the transaminase level was sharply increased, peaking on day 9. The patient was suspected of having small-for-size syndrome and was treated symptomatically. The patient experienced a significant improvement in symptoms on postoperative day 13 and regular postoperative follow-ups were performed until now and the patient is now in remission. In recipient 3 (male; age, 48 years), the recipient recovered well and the liver function returned to normal on postoperative day 3. The patient was discharged from hospital and has been in remission thus far. Adult liver transplantations from pediatric donors are feasible treatments. Systematic donor and recipient assessments, sound surgical skills and optimal postoperative treatments are essential for success in the transplantation of livers from pediatric donors into adult recipients. Considering the condition of the donor liver, the selection of recipients and appropriate surgical methods are particularly important in these cases.

The impact of ABCB1 gene polymorphism and its expression on non-small-cell lung cancer development, progression and therapy - preliminary report

The ABCB1 gene belongs to ATP binding cassette (ABC) transporter genes that has been previously implicated in cancer progression and drug response. This study aimed to evaluate the association between the SNP 3435 and the expression of the ABCB1 gene in lung cancer patients in the Polish population in comparison to clinicopathological parameters and treatment. 150 RNA and 47 DNA samples were isolated from 49 lung cancer cases including both tissue samples and blood taken from the same patients at three time points: diagnosis, 100 days and one year after the surgical intervention. Qualitative and real-time PCR analysis of expression were done, also genotyping by PCR-RFLP. Mutant homozygous TT and allele T are present statistically significantly more frequently in the group of patients with lung cancer. There is no difference with expression level in lung cancer tissue and blood sample taken from the same patients before surgical treatment. On the basis of blood samples analysis it was observed that the expression level of ABCB1 mRNA was growing in time. Higher levels were marked after 100 days and one year after the surgical intervention. The complementary pharmacological treatment induced higher expression levels of ABCB1. The presented data suggest an important role of ABCB1 in lung cancer, the increasing level of ABCB1 mRNA which can be connected with induction of multidrug resistance mechanism is also significant, that observation must be confirmed in further analysis.

Association study of genetic polymorphisms in proteins involved in oseltamivir transport, metabolism, and interactions with adverse reactions in Mexican patients with acute respiratory diseases

Oseltamivir, a pro-drug, is the best option for treatment and chemoprophylaxis for influenza outbreaks. However, many patients treated with oseltamivir developed adverse reactions, including hypersensitivity, gastritis, and neurological symptoms. The aim of this study was to determine the adverse drug reactions (ADRs) in Mexican patients treated with oseltamivir and whether these ADRs are associated with SNPs of the genes involved in the metabolism, transport, and interactions of oseltamivir. This study recruited 310 Mexican patients with acute respiratory diseases and treated them with oseltamivir (75 mg/day for 5 days) because they were suspected to have influenza A/H1N1 virus infection. Clinical data were obtained from medical records and interviews. Genotyping was performed using real-time polymerase chain reaction and TaqMan probes. The association was assessed under genetic models with contingency tables and logistic regression analysis. Out of 310 patients, only 38 (12.25%) presented ADRs to oseltamivir: hypersensitivity (1.9%), gastritis (10%), and depression and anxiety (0.9%). The polymorphism ABCB1-rs1045642 was associated with adverse drug reactions under the recessive model (P = 0.017); allele C was associated with no adverse drug reactions, while allele T was associated with adverse drug reactions. The polymorphisms SLC15A1-rs2297322, ABCB1-rs2032582, and CES1-rs2307243 were not consistent with Hardy-Weinberg equilibrium, and no other associations were found for the remaining polymorphisms. In conclusion, the polymorphism rs1045642 in the transporter encoded by the ABCB1 gene is a potential predictive biomarker of ADRs in oseltamivir treatment.

ABCB1 Gene Is Associated With Clinical Response to SNRIs in a Local Chinese Han Population

Background: The relation between the ATP-binding cassette subfamily B member 1 (ABCB1) gene and major depressive disorder (MDD) has been studied in a local Chinese Han population. MDD is associated with the rs2032582 (G2677T) and rs1128503 (C1236T) single-nucleotide polymorphisms (SNPs) of ABCB1 but not with rs1045642, rs2032583, rs2235040, and rs2235015. This study aims to explore the potential correlations of therapeutic responses with selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) in a local Chinese Han population.

Methods: The study population included 292 patients with MDD. All patients were assessed at baseline and at first, second, fourth, and sixth weeks according to the 17-item Hamilton Rating Scale for Depression (HAM-D17) to determine their therapeutic responses to SSRIs and SNRIs.

Results: In the SSRI therapy group, the genotype or allele distribution of six SNPs was not significantly different between responders and nonresponders. In the SNRI therapy group, only rs2032583 was associated with a therapeutic response to SNRIs. The C allele of the ABCB1 rs2032583 polymorphism was negatively correlated with therapeutic responses according to logistic regression analysis.

Conclusion: The ABCB1 gene polymorphisms may not be associated with therapeutic responses to SSRIs but not with SNRIs. The TT genotype of rs2032583 could be a predictive factor of improved treatment responses to SNRIs in the Chinese population. These findings should be replicated in future studies with larger patient groups.

NR3C1, ABCB1, TNF and CYP2C19 polymorphisms association with the response to the treatment of erythema nodosum leprosum

Aim: To evaluate the effects of gene polymorphisms in the treatment of erythema nodosum leprosum with prednisone/thalidomide. Patients & methods: A total of 152 patients from different regions of Brazil were included. Generalized estimating equation was used to evaluate the influence of polymorphisms and haplotypes on the drug dose variation throughout the treatment. Results: An association between the genotype tuberculoid of polymorphism ABCB1 3435C>T (rs1045642; p = 0.02) and prednisone dose was found in the recessive model. An association between the haplotypes 1031T/-863C/-857C/-308A/-238G (p = 0.006) and 1031T/-863C/-857T/-308A/-238G (p = 0.040) of the TNF gene and the CYP2C19*2 polymorphism were also identified, in relation to thalidomide dosage variation over the course of treatment. Conclusion: This work presents the first pharmacogenetic report of association between gene polymorphisms and erythema nodosum leprosum treatment with prednisone/thalidomide.

Opioid-related genetic polymorphisms do not influence postoperative opioid requirement: A prospective observational study

BACKGROUND

Among the various factors that may influence the pharmacological response to opioids, genetic polymorphisms [single nucleotide polymorphisms (SNP)] have generated some interest.

OBJECTIVES

To examine the influence on morphine dose requirements and adverse events in the postoperative period of four SNP [opioid receptor mu1 (OPRM1), ATP-binding cassette subfamily B, member 1 (ABCB1) ex-21 and ex-26, catechol-o-methyltransferase (COMT)] in candidate genes involved in morphine pharmacodynamics and pharmacokinetics.

DESIGN

A single centre prospective study.

SETTING

University Hospital, Paris, France, from 2 January 2007 to 15 November 2011.

PATIENTS

A total of 438 white adults scheduled for major orthopaedic surgery (spine, hip and knee) under general anaesthesia. The main exclusion criteria were receiving opioids for chronic pain, nonopioid drugs within 2 days prior to surgery, pregnancy, renal insufficiency, sleep apnoea obstruction syndrome, morbid obesity, severe hepatic impairment, cognitive dysfunction.

INTERVENTIONS

Assays of plasma concentrations of morphine and metabolites (morphine 3-glucuronide and morphine 6-glucuronide) were performed and common polymorphisms in four candidate genes [OPRM1 A118G rs1799971; P-glycoprotein (ABCB1) T3435C (rs1045642) and G2677T/A (rs2032582); COMT Val 158 Met (rs4680)] were analysed.Morphine was titrated by staff in the postanaesthesia care unit (PACU) and in the ward patient-controlled intravenous analgesia was used for 24 h.

MAIN OUTCOME MEASURES

The dose of morphine required to achieve pain relief and the influence of SNP in genes involved in morphine pharmacodynamics and kinetics on morphine dose requirements. Secondary endpoints were the concentrations of morphine, morphine 6-glucuronide and morphine 3-gluguronide, the proportion of patients requiring a rescue analgesic and the proportion of morphine-related adverse events.

RESULTS

A total of 404 patients completed the study to final analysis. The mean ± SD morphine dose to achieve pain relief was 15.8 ± 8.8 mg in the PACU and 22.7 ± 18.6 mg during patient-controlled intravenous administration. Morphine-related adverse events were observed in 37%. There was no relationship between any genetic polymorphisms and morphine dose, morphine 3-gluguronide and morphine 6-glucuronide concentration, morphine-related adverse events or pain level. In the PACU only, P-glycoprotein polymorphisms (ex-21; ex-26) were significantly associated with morphine concentration but the prediction of the model was poor (R = 0.04) CONCLUSION: No major relationship has been demonstrated between SNP of OPRM1, ABCB1, COMT and morphine requirement, pain level or adverse effects in the postoperative period.

TRIAL REGISTRATION

NCT00822549 (www.clinicaltrials.gov).

Influence of CYP450 Enzymes, CES1, PON1, ABCB1, and P2RY12 Polymorphisms on Clopidogrel Response in Patients Subjected to a Percutaneous Neurointervention

PURPOSE

Clopidogrel is a thienopyridine prodrug that inhibits platelet aggregation. It is prescribed to prevent atherothrombotic and thromboembolic events in patients receiving a stent implant in carotid, vertebral, or cranial arteries. The influence of cytochrome P-450 (CYP) 2C19 on the response to clopidogrel has been widely studied; however, the effect of other genes involved in clopidogrel absorption and metabolism has not been established in this cohort of patients.

METHODS

This observational retrospective study assessed the antiplatelet response and the prevalence of hemorrhagic or ischemic events after percutaneous neurointervention in clopidogrel-treated patients, related to 35 polymorphisms in the genes encoding the clopidogrel-metabolizing enzymes (CYP2C19, CYP1A2, CYP2B6, CYP2C9, CYP2C9, CYP3A4, CYP3A5, carboxylesterase-1 [CES1], and paraoxonase-1 [PON1]), P-glycoprotein transporter (ABCB1), and platelet receptor P2Y₁₂. Polymorphisms were analyzed by quantitative real-time polymerase chain reaction and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. Antiplatelet response was documented with the VerifyNow system (Accriva, San Diego, California).

FINDINGS

We confirmed that CYP2C19 is the most important enzyme involved in clopidogrel response. The carriage of the CYP2C19*2 allele was strongly associated with hyporesponse to clopidogrel, while the CYP2C19*17 allele was a protective factor for the development of ischemic events (odds ratio = 0.149; P = 0.002) but a risk factor for bleeding (odds ratio = 3.60; P = 0.038). Patients carrying ABCB1 mutated alleles showed lower aggregation values, suggesting that clopidogrel absorption is influenced by P-glycoprotein. In fact, the percentage of responders was significantly higher in the group carrying the mutated haplotype compared to the wild type (80.8% vs 43.3%; P = 0.009). Patients with the CES1 G143E C/T genotype showed a considerably lower, aggregation value versus wild-type patients, although the difference was not significant likely due to the small sample size (59.0 [21.2] vs 165.2 [86.0] PRU; P = 0.084), which suggests an increased active metabolite formation. No relationship was found between polymorphisms in other CYP genes, PON1, or P2RY12 and response to clopidogrel in patients subjected to neurointervention procedures.

IMPLICATIONS

Therapeutic guidelines recommend that CYP2C19 intermediate and poor metabolizers with acute coronary syndromes undergoing percutaneous coronary intervention receive an alternative antiplatelet therapy; however, genotype-guided therapy is not a standard recommendation for neurovascular conditions. This is the first study to carry out a joint analysis of CYP2C19 and other genes involved in clopidogrel treatment in patients receiving percutaneous neurointervention. Our findings support routine genotyping in clopidogrel-treated patients. Moreover, we encourage considering an alternative antiplatelet therapy in CYP2C19 intermediate, poor and ultrarapid metabolizers. Additionally, ABCB1 polymorphisms could be considered for a better pharmacogenetic approach.

Effect of ABCB1 C3435T Polymorphism on Pharmacokinetics of Antipsychotics and Antidepressants

P-glycoprotein, encoded by ABCB1, is an ATP-dependent drug efflux pump which exports substances outside the cell. Some studies described connections between C3435T polymorphism T allele and lower P-glycoprotein expression; therefore, homozygous T/T could show higher plasma levels. Our aim was to evaluate the effect of C3435T on pharmacokinetics of 4 antipsychotics (olanzapine, quetiapine, risperidone and aripiprazole) and 4 antidepressants (trazodone, sertraline, agomelatine and citalopram). The study included 473 healthy volunteers receiving a single oral dose of one of these drugs, genotyped by real-time PCR. Multivariate analysis was performed to adjust the effect of sex and genotype of the main cytochrome P450 enzymes. C3435T polymorphism had an effect on olanzapine pharmacokinetics, as T/T individuals showed lower clearance and volume of distribution. T/T individuals showed lower T_1/2 of 9-OH-risperidone, but this difference disappeared after multivariate correction. T/T homozygous individuals showed lower dehydro-aripiprazole and trazodone area under the concentration-time curve, along with lower half-life and higher clearance of trazodone. C/T genotype was associated to higher citalopram maximum concentration. C3435T had no effect on quetiapine, sertraline or agomelatine pharmacokinetics. C3435T can affect the elimination of some drugs in different ways. Regarding risperidone, trazodone and dehydro-aripiprazole, we observed enhanced elimination while it was reduced in olanzapine and citalopram. However, in quetiapine, aripiprazole, sertraline and agomelatine, no changes were detected. These results suggest that P-glycoprotein polymorphisms could affect CNS drugs disposition, but the genetic factor that alters its activity is still unknown. This fact leads to consider the analysis of ABCB1 haplotypes instead of individual variants.

Clinical Relevant Polymorphisms Affecting Clopidogrel Pharmacokinetics and Pharmacodynamics: Insights from the Puerto Rico Newborn Screening Program

Background: Variations in several clopidogrel-pharmacogenes have been linked to clopidogrel response variability and clinical outcomes. We aimed to determine the frequency distribution of major polymorphisms on CYP2C19, PON1, ABCB1 and P2RY12 pharmacogenes in Puerto Ricans. Methods: This was a cross-sectional, population-based study of 200 unrelated "Guthrie" cards specimens from newborns registered in the Puerto Rican newborn screening program (PRNSP) between 2004 and 2014. Taqman® SNP assay techniques were used for genotyping. Results: Minor allele frequencies (MAF) were 46% for PON1 (rs662), 41% for ABCB1 (rs1045642), 14% for CYP2C19*17, 13% for CYP2C19*2, 12% for P2RY12-H2 and 0.3% for CYP2C19*4. No carriers of the CYP2C19*3 variants were detected. All alleles and genotype proportions were found to be in Hardy⁻Weinberg equilibrium (HWE). Overall, there were no significant differences between MAFs of these variants in Puerto Ricans and the general population (n = 453) of the 1000 Genome project, except when comparisons to each individual parental group were performed (i.e., Africans, Europeans and East-Asians; p < 0.05). As expected, the prevalence of these markers in Puerto Ricans most resembled those in the 181 subjects from reference populations of the Americas. Conclusions: These prevalence data provide a necessary groundwork for future clinical studies of clopidogrel pharmacogenetics in Caribbean Hispanics.

Associations between genetic polymorphisms of membrane transporter genes and prognosis after chemotherapy: meta-analysis and finding from Seoul Breast Cancer Study (SEBCS)

Membrane transporters can be major determinants of the pharmacokinetic profiles of anticancer drugs. The associations between genetic variations of ATP-binding cassette (ABC) and solute carrier (SLC) genes and cancer survival were investigated through a meta-analysis and an association study in the Seoul Breast Cancer Study (SEBCS). Including the SEBCS, the meta-analysis was conducted among 38 studies of genetic variations of transporters on various cancer survivors. The population of SEBCS consisted of 1338 breast cancer patients who had been treated with adjuvant chemotherapy. A total of 7750 SNPs were selected from 453 ABC and/or SLC genes typed by an Affymetrix 6.0 chip. ABCB1 rs1045642 was associated with poor progression-free survival in a meta-analysis (HR = 1.33, 95% CI: 1.07-1.64). ABCB1, SLC8A1, and SLC12A8 were associated with breast cancer survival in SEBCS (P_gene < 0.05). ABCB1 rs1202172 was differentially associated with survival depending on the chemotherapy (P_interaction = 0.035). Our finding provides suggestive associations of membrane transporters on cancer survival.

Recipient rs1045642 Polymorphism Is Associated With Office Blood Pressure at 1-Year Post Kidney Transplantation: A Single Center Pharmacogenetic Cohort Pilot Study

Background: Corticosteroids are associated with reduced bone mineral density (BMD), as well as water and salt retention, leading to hypertension. They are substrates for P-glycoprotein, a protein coded by the highly polymorphic ABCB1 gene. We hypothesized that one ABCB1 polymorphism, rs1045642, is associated with blood pressure and BMD parameters at 1-year post kidney transplantation (KT).

Methods: Rs1045642 was genotyped using pyrosequencing in 40 KT recipients. Both dominant (CC vs. CT + TT) and codominant (CC vs. CT vs. TT) genetic models (analysis of variance from linear regressions) were adjusted for confounding variables (age, sex, type of nephropathy, glomerular filtration rate, and corticosteroid use at 1 year).

Results: Rs1045642 genotypes were significantly associated with systolic (SBP) and diastolic (DBP) blood pressure 1-year post-transplantation, independent of the genetic model used (adjusted codominant model: SBP p-value = 0.015, DBP p-value = 0.038; adjusted dominant model: SBP p-value = 0.003, DBP p-value = 0.011). A non-statistically significant trend was observed for an association between rs1045642 and BMD change at 1-year post-KT.

Conclusions: Rs1045642 is significantly associated with higher BP 1 year after KT. Further investigations are necessary to confirm the role of rs1045642 in corticosteroid-related adverse effects.

Opioids Resistance in Chronic Pain Management

Chronic pain management represents a serious healthcare problem worldwide. Chronic pain affects approximately 20% of the adult European population and is more frequent in women and older people. Unfortunately, its management in the community remains generally unsatisfactory and rarely under the control of currently available analgesics. Opioids have been used as analgesics for a long history and are among the most used drugs; however, while there is no debate over their short term use for pain management, limited evidence supports their efficacy of long-term treatment for chronic non-cancer pain. Therapy with opioids is hampered by inter-individual variability and serious side effects and some opioids often result ineffective in the treatment of chronic pain and their use is controversial. Accordingly, for a better control of chronic pain a deeper knowledge of the molecular mechanisms underlying resistance to opiates is mandatory.

Comparison of CYP2C9, CYP2C19, CYP2D6, ABCB1, and SLCO1B1 gene-polymorphism frequency in Russian and Nanai populations

Background

The efficiency and safety of drug therapy depends on the peculiarities of functioning of the P450 cytochrome group and transporting proteins. There are significant differences for single-nucleotide polymorphism (SNP) frequency.

Materials and methods

We studied the peculiarities of P450 cytochrome polymorphisms, SLCO1B1 transporting protein, and P-glycoprotein carriage in healthy volunteers in the Nanai ethnic group living in Russia, and compared them to the carriage of SNPs in the Russian population according to literature data.

Results

After performing the real-time polymerase chain reactions on the samples from 70 healthy volunteers from the Nanai group, for the CYP2C9*2^C430T polymorphism we determined 70 CC-genotype carriers. As for the CYP2C9*3^A1075C polymorphism, we found 62 AA-genotype carriers and eight AC-genotype carriers. For the CYP2C19*2^G681A polymorphism, we determined 39 GG-genotype carriers and 28 GA-genotype carriers, for the CYP2C19*3^G636A polymorphism 58 GG-genotype carriers and 12 GA-genotype carriers, and for the CYP2C19*17^C806T polymorphism 67 CC-genotype carriers and three CT-genotype carriers. For the CYP2D6*4^G1846A polymorphism, the GG genotype had 68 carriers, and the GA genotype two carriers. For the ABCB1*6^C3435T polymorphism, there were 19 CC-genotype carriers and 39 CT-genotype carriers. For the SLCO1B1*5^T521C polymorphism, the TT genotype had 41 carriers and the CT genotype 25 carriers. The distribution of genotypes fitted the Hardy–Weinberg equilibrium for all the polymorphisms, except those of CYP2C9*2. There were also significant differences in allele frequencies for some polymorphisms between the Nanais and the Russians.

Conclusion

In the Nanai population, there are polymorphisms connected with the decrease in safety and efficiency of drug therapy. Studying the ethnic differences might influence the determination of priority in the introduction of pharmacogenetic tests in clinical practice in different regions of Russia.

Association of Single-Nucleotide Polymorhism C3435T in the ABCB1 Gene with Opioid Sensitivity in Treatment of Postoperative Pain

BACKGROUND

The minimal effective analgesic concentration of opioids required for satisfactory analgesia may differ significantly among the patients. Genetic factors may contribute to the variable response to opioids by affecting their pharmacokinetics or pharmacodynamics.

METHODS

Ninety nine patients undergoing abdominal surgery with colorectal anastomosis because of colorectal carcinoma were enrolled in the present study. C34535T was genotyped in all subjects and the patients were divided into three groups according to their genotype: CC-wild type homozygous, CT-mutant heterozygous and TT-mutant homozygous. Intravenous fentanyl, patient controlled analgesia was provided postoperatively for pain control in the first 24 hour after surgery. Opioid consumption, pain scores and the adverse side effects were evaluated.

RESULTS

Our main result is that the patients in the CC genotype group consumed significantly more fentanyl (375.0 μg ± 43.1) than the patients in the TT group (295.0 μg ± 49.1) and the CT (356.4 μg ± 41.8) group in the treatment of postoperative pain. The patients in the TT group had lower VAS scores at 6h, 12h, 18 h and 24h postoperatively. There were no significant differences in the side effects among the three groups regarding the vomiting and the sedation score. The patients in the TT group had more frequently nausea score 1, than the patients in the other two groups.

CONCLUSION

Our study indicates that the C3435T SNPs of the ABCB1 gene is associated with differences in the opioid sensitivity. The ABCB1 polymorphism may serve as an important genetic predictor to guide the acute pain therapy in postoperative patients.

Association between CYP3A5 polymorphisms and the risk of adverse events in patients undergoing clopidogrel therapy: Meta-analysis

INTRODUCTION

We wished to explore the relationship between CYP3A5 polymorphisms and adverse events in patients undergoing clopidogrel therapy.

METHODS

A Boolean search of the PubMed, EMbase, OVID and Cochrane Library databases was conducted in April 2016. The primary outcome was major adverse cardiovascular events (MACE). The secondary outcome was bleeding events and resistance to the effects of clopidogrel. The CYP3A5 polymorphism was classified into three types: wild-type (AA), heterozygote (AG) and homozygous mutant (GG). We estimated pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) using the Mantel-Haenszel model.

RESULTS

Twelve studies involving 8284 patients were eligible for our meta-analysis. CYP3A5 polymorphisms had no obvious influence on MACE (AA+AG vs. GG: OR=1.032, 95% CI=0.583-1.824, p=0.915; AA vs. AG+GG: 1.415, 0.393-5.094, 0.595). There was no significant relationship between CYP3A5 polymorphisms and bleeding (GG vs. AA+AG: OR=0.798, 95% CI=0.370-1.721, p=0.565) or clopidogrel resistance (AA+AG vs. GG: 1.009, 0.685-1.488, 0.963; AA vs. AG+GG, 0.618, 0.368-1.039, 0.069).

CONCLUSION

No significant correlation was found between CYP3A5 polymorphisms and adverse events due to clopidogrel therapy.

Association between ABCB1 C3435T polymorphism and breast cancer risk: a Moroccan case-control study and meta-analysis

BACKGROUND

Breast cancer is the most common cause of cancer death among women. Several studies have investigated the relationship between the C3435T polymorphism of ABCB1 gene and risk of breast cancer; but the results are conflicting. In the present study, we sought to assess the relationship between the C3435T polymorphism in ABCB1 gene and the risk of breast cancer in a sample of the Moroccan population.

METHODS

A case control study was performed on 60 breast cancer patients and 68 healthy women. The ABCB1 C3435T polymorphism was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Furthermore, a meta-analysis including 16 studies with 6094 cases of breast cancer and 8646 controls was performed.

RESULTS

Genotype frequencies were 50 % for CC, 33.3 % for CT and 16.7 % for TT in patients and 41.2 % for CC, 48.5 % for CT and 10.3 % for TT respectively in the control group. This difference was not statistically significant. The same trend as observed in the allele distribution between patients and controls (P = 0.84). Findings from the meta-analysis showed that the ABCB1 C3435T polymorphism was not associated with an increased risk of breast cancer in the dominant model (OR = 0.907; 95 % CI = 0.767-1.073; P = 0.25) as well as in the recessive model (OR = 1.181; 95 % CI = 0.973-1.434; P = 0.093) and in the allele contrast model (OR = 1.098; 95 % CI = 0.972-1.240; P = 0.133). However, the stratification of studies on ethnic basis showed that the TT genotype was associated with the risk of breast cancer in Asians (OR = 1.405; 95 % CI = 1.145-1.725; P = 0.001), Caucasians (OR = 1.093; 95 % CI = 1.001-1.194; P = 0.048) and North African (OR = 2.028; 95 % CI = 1.220-3.371; P = 0.006).

CONCLUSIONS

We have noted that the implication of C3435T variant on the risk of breast cancer was ethnicity-dependent. However, there is no evidence that ABCB1 C3435T polymorphism could play a role in susceptibility to breast cancer in Morocco. Further studies with a larger sample size, extended to other polymorphisms are needed to understand the influence of ABCB1 genetic variants on the risk of breast cancer.

Clinical Pharmacogenetics of the Major Adenosine Triphosphate−Binding Cassette and Solute Carrier Drug Transporters

Interindividual variability in drug response is a significant problem in clinical practice, and it is likely that genetic variation among the drug transport genes are major contributors to such variability. Numerous genetic alterations affecting the members of the adenosine triphosphate-binding cassette (ABC) and solute carrier (SLC) families of transporters have been identified. Considerable data exist regarding how mutations in the ABCB1 gene that encodes p-glycoprotein impact drug disposition and response in vivo, but many study reports are conflicting on both the direction of any effect as well as the significance of any alteration. Many possible reasons for such discrepant study results have been identified, and efforts to improve the quality of such pharmacogenetic clinical association studies are ongoing. For most other clinically important transporters relatively, little clinical data exist regarding the significance of known genetic variants despite in vitro evidence of altered function for many of these transporters. What clinical data do exist suggest that certain mutations in ABCG2 and SLCO1B1 may be of importance clinically. Until the current uncertainties regarding the importance of genetic variants in drug transporter genes are clarified, the clinical application of existing pharmacogenetic data should be done with caution.

Single Nucleotide Polymorphisms in Pediatric Idiopathic Nephrotic Syndrome

Polymorphic variants in several molecules involved in the glomerular function and drug metabolism have been implicated in the pathophysiology of pediatric idiopathic nephrotic syndrome (INS), but the results remain inconsistent. We analyzed the association of eleven allelic variants in eight genes (angiopoietin-like 4 (ANGPTL4), glypican 5 (GPC5), interleukin-13 (IL-13), macrophage migration inhibitory factor (MIF), neural nitric oxide synthetase (nNOS), multidrug resistance-1 (MDR1), glucocorticoid-induced transcript-1 (GLCCI1), and nuclear receptor subfamily-3 (NR3C1)) in 100 INS patients followed up till adulthood. We genotyped variants using PCR and direct sequencing and evaluated estimated haplotypes of MDR1 variants. The analysis revealed few differences in SNP genotype frequencies between patients and controls, or in clinical parameters among the patients. Genotype distribution of MDR1 SNPs rs1236, rs2677, and rs3435 showed significant (p < 0.05) association with different medication regimes (glucocorticoids only versus glucocorticoids plus additional immunosuppressives). Some marginal association was detected between ANGPTL4, GPC5, GLCCI1, and NR3C1 variants and different medication regimes, number of relapses, and age of onset. Conclusion. While MDR1 variant genotype distribution associated with different medication regimes, the other analyzed gene variants showed only little or marginal clinical relevance in INS.

POLYMORPHISMS OF DRUG-METABOLIZING ENZYMES CYP1A2, CYP2D6, GST, NAT2 AND TRANSPORTER MDR1 IN POPULATION OF BELARUS: COMPARISON WITH SELECTED EUROPEAN AND ASIAN POPULATIONS

Drug therapeutic efficiency and development of unfavorable pharmacologic responses as well as the disease predisposition are caused first of all by patient’s genetic features. Genetic variations in genes encoding drug-metabolizing enzymes and transporter proteins are essential to understand the ethnic differences in disease occurrence, development, prognosis, therapeutic response and toxicity of drugs. For that reason, it is necessary to establish the normative frequency distribution of genotypes and alleles of these genes in a particular population. Data on frequency of pharmacogenetic polymorphisms in the of Belarus population are limited. The goal of our investigation was to analyze the frequency distribution of genotypes and alleles of genes encoding drug-metabolizing enzymes (CYP1А2, CYP2D6 – I phase; GSTs, NAT2 – II phase) and transporter protein MDR1 in the population of Belarus and comparisons with other ethnic populations. Our results indicate that clinically important genes are genetically highly variable and differ considerably between populations. Differences in allele frequencies across continents should be considered when designing clinical trials of new drugs continents should be considered when designing clinical trials of new drugs.

Impact of Genetic Polymorphisms of ABCB1 (MDR1, P-Glycoprotein) on Drug Disposition and Potential Clinical Implications: Update of the Literature

ATP-binding cassette transporter B1 (ABCB1; P-glycoprotein; multidrug resistance protein 1) is an adenosine triphosphate (ATP)-dependent efflux transporter located in the plasma membrane of many different cell types. Numerous structurally unrelated compounds, including drugs and environmental toxins, have been identified as substrates. ABCB1 limits the absorption of xenobiotics from the gut lumen, protects sensitive tissues (e.g. the brain, fetus and testes) from xenobiotics and is involved in biliary and renal secretion of its substrates. In recent years, a large number of polymorphisms of the ABCB1 [ATP-binding cassette, sub-family B (MDR/TAP), member 1] gene have been described. The variants 1236C>T (rs1128503, p.G412G), 2677G>T/A (rs2032582, p.A893S/T) and 3435C>T (rs1045642, p.I1145I) occur at high allele frequencies and create a common haplotype; therefore, they have been most widely studied. This review provides an overview of clinical studies published between 2002 and March 2015. In summary, the effect of ABCB1 variation on P-glycoprotein expression (messenger RNA and protein expression) and/or activity in various tissues (e.g. the liver, gut and heart) appears to be small. Although polymorphisms and haplotypes of ABCB1 have been associated with alterations in drug disposition and drug response, including adverse events with various ABCB1 substrates in different ethnic populations, the results have been majorly conflicting, with limited clinical relevance. Future research activities are warranted, considering a deep-sequencing approach, as well as well-designed clinical studies with appropriate sample sizes to elucidate the impact of rare ABCB1 variants and their potential consequences for effect sizes.

OPRM1 and ABCB1 Polymorphisms and Their Effect on Postoperative Pain Relief With Piritramide

Genetic factors may contribute to the differential response to opioids. The aim of this study was to evaluate the association between polymorphisms of µ1-opioid receptor gene OPRM1 (rs1799971), and P-glycoprotein transporter gene ABCB1 (rs1045642, rs2032582), and piritramide efficacy under postoperative patient-controlled analgesia (PCA). In 51 patients, OPRM1 variant was associated with decreased efficacy in early postoperative period evidenced by sum of pain intensity difference in the 0-6 h postoperative period (SPID0-6), (F=3.27, p=0.029). Mean (SD) SPID0-6 was observed in the 118AA genotype 22.9 (6.1) mm, which was significantly higher from the 118GG genotype 10.0 (4.4) mm, p=0.006. The lowest cumulative dose was recorded in 118AA genotype 19.1 (9.8) mg, which was significantly less than in the 118GG genotype group 36.6 (6.1) mg, p=0.017. Opioid–induced adverse effects were observed in 11, 30, and 100 % of patients in 118AA, 118AG, and 118GG genotype groups, respectively (p<0.05). Piritramide efficacy and safety was not significantly affected by ABCB1 (rs1045642, rs2032582) polymorphisms. Variant OPRM1 118G allele is associated with decreased acute postoperative pain relief after piritramide. Decreased efficacy leads to higher drug consumption under PCA settings, which however, does not fully compensate insufficient pain relief, but increases incidence of adverse effects.

Genetic factors affecting drug disposition in Asian cancer patients

INTRODUCTION

In the era of genomic medicine, it is increasingly recognized that ethnogeographic differences in drug pharmacology exist between Asian and other populations. This is particularly pertinent to oncology, where drugs forming the backbone of chemotherapy often have narrow therapeutic windows and are frequently dosed close to maximally tolerable levels.

AREAS COVERED

At the population level, ancestry is important because historical-biogeographical confluences have shaped population genetics and pharmacoethnicity in the Asian race through allelic differentiation and interethnic differences in inheritance patterns of linkage disequilibrium. At the individual level, cis- and trans-acting germline polymorphisms and somatic mutations in genes encoding drug-metabolizing enzymes and transporters act in a multifactorial manner to determine drug disposition phenotype and clinical response in Asian cancer patients. A growing body of evidence also finds that complex genetic interactions and regulation, including a multiplicity of gene control mechanisms, are increasingly implicated in genotype-phenotype correlates than has hitherto been appreciated--potentially serving as the mechanistic links between hits in non-coding regions of genome-wide association studies and drug toxicity. Together, these genetic factors contribute to the clinical heterogeneity of drug disposition in Asian cancer patients.

EXPERT OPINION

This topic has broad relevance for the optimization and individualization of anticancer strategies in Asians.

Diltiazem augments the influence of MDR1 genotype status on cyclosporine concentration in Chinese patients with renal transplantation

AIM

Co-administration of diltiazem can reduce the dosage of cyclosporine (CsA) in patients with renal transplantation. In this study, we investigated how diltiazem altered the relationship between MDR1 genetic polymorphisms and CsA concentration in Chinese patients with renal transplantation.

METHODS

A total of 126 renal transplant patients were enrolled. All the patients received CsA (2-4 mg·kg(-1)·d(-1)), and diltiazem (90 mg/d) was co-administered to 76 patients. MDR1-C1236T, G2677T/A, and C3435T polymorphisms were genotyped. The whole blood concentration was measured using the FPIA method, and the adjusted trough concentrations were compared among the groups with different genotypes.

RESULTS

In all patients, MDR1-C1236T did not influence the adjusted CsA trough concentration. With regard to MDR1-3435, the adjusted CsA trough concentration was significantly higher in TT carriers than in CC and CT carriers when diltiazam was co-administered (58.83±13.95 versus 46.14±7.55 and 45.18±12.35 ng/mL per mg/kg, P=0.011), and the differences were not observed in patients without diltiazam co-administered. With regard to MDR1-2677, the adjusted CsA trough concentration was significantly higher in TT carriers than in GG and GT carriers when diltiazam was co-administered (61.31±12.93 versus 52.25±7.83 and 39.70±7.26 ng/mL per mg/kg, P=0.0001). The differences were also observed in patients without diltiazam co-administered (43.27±5.95 versus 35.22±7.55 and 29.54±5.35 ng/mL per mg/kg, P=0.001). The adjusted CsA trough blood concentration was significantly higher in haplotype T-T-T and haplotype T-T-C carriers than in non-carriers, regardless of diltiazem co-administered.

CONCLUSION

MDR1 variants influence the adjusted CsA trough concentration in Chinese patients with renal transplant, and the influence more prominent when diltiazem is co-administered.

Investigation of CYP 3A5 and ABCB1 gene polymorphisms in the long-term following renal transplantation: Effects on tacrolimus exposure and kidney function

The clinical use of tacrolimus (Tac) is complicated by the large inter-individual variability in its pharmacokinetics as well as by chronic adverse effects on renal function. The main goal of this study was to evaluate the potential influence of cytochrome P450 3A5 (CYP 3A5) and ATP-binding cassette transporter B1 (ABCB1) gene polymorphisms on Tac dose requirements and dose-adjusted concentrations in different long-term periods following renal transplantation. Another aim was to investigate whether these polymorphisms affect renal function in late post-transplant period. A total of 91 renal transplant recipients were enrolled for genotyping analysis, and 53 of these entered into a pharmacokinetic-pharmacogenetic study. Allele-specific polymerase chain reaction was used for CYP 3A5 and ABCB1 polymorphism determination. Pharmacokinetic data (dose, trough concentration and dose-adjusted concentration of Tac) and renal function parameters [creatinine (Cre) clearance and serum Cre level] were analyzed in relation to patient genotype at 6, 12 and 24 months after transplantation. Also, linear regression analysis was performed to evaluate the effect of CYP 3A5 and ABCB1 genotypes on Tac exposure and renal function up to 24 months post-transplant. Individuals carrying the CYP 3A5*1/*3 genotype had higher Tac dose requirements than CYP 3A5*3/*3 carriers at 6, 12 and 24 months after renal transplantation. The results revealed that ABCB1 polymorphism did not influence Tac dose requirements independently. Regression analysis showed that CYP 3A5 influenced the Tac dose-adjusted concentration as well as renal function up to 24 months post-transplant. These findings confirmed that CYP 3A5 polymorphism represents the most important determinant of Tac dose and exposure in the late period following renal transplantation. Furthermore, the obtained results indicate that the decline in renal function may be more pronounced in patients with CYP 3A5*1 in the long-term period after renal transplantation.

Association of ABCB1 C3435T polymorphism with phenobarbital resistance in Thai patients with epilepsy

WHAT IS KNOWN AND OBJECTIVE

One-third of patients with epilepsy are resistant to anti-epileptic drugs (AEDs). Drug-resistant epilepsy is believed to be multifactorial involving both genetic and non-genetic factors. Genetic variations in the ABCB1 gene encoding the drug efflux transporter, p-glycoprotein (p-gp), may influence the interindividual variability in AED response by limiting drugs from reaching their target. Phenobarbital (PB), one of the most cost-effective and widely used AEDs in developing countries, has been reported to be transported by p-gp. This study aimed to investigate the association of a genetic variant, ABCB1 3435C>T, and non-genetic factors with phenobarbital response in Thai patients with epilepsy.

METHODS

One hundred and ten Thai patients with epilepsy who were treated with PB maintenance doses were enrolled in this study. Two phenotypic groups, PB-responsive epilepsy and PB-resistant epilepsy, were defined according to the International League Against Epilepsy (ILAE) criteria. Subjects were genotyped for ABCB1 3435C>T (rs1045642). Multiple logistic regression analysis was tested for the association of ABCB1 3435C>T polymorphism and non-genetic factors with PB response.

RESULTS AND DISCUSSION

Sixty-two PB-responsive epilepsy subjects and 48 PB-resistant epilepsy subjects were identified. All genotype frequencies of the ABCB1 3435C>T SNP were consistent with the Hardy-Weinberg equilibrium (P > 0·05). The ABCB1 3435C>T polymorphism and type of epilepsy were associated with response to PB. Patients with PB-resistant epilepsy had a significantly higher frequency of ABCB1 3435CC genotype and had focal epilepsy more often than patients with PB-responsive epilepsy (adjusted OR = 3·962, 95% CI = 1·075-14·610, P-value = 0·039; adjusted OR = 5·936, 95% CI = 2·272-15·513, P-value < 0·001, respectively). The model explained 25·5% of the variability in response to PB (R(2)  = 0·255).

WHAT IS NEW AND CONCLUSION

Thai patients of ABCB1 3435CC genotype and with focal epilepsy were more often PB resistant. Those two factors partly account for the variability in Thai epilepsy patients' response to phenobarbital.