PharmGKB summary: very important pharmacogene information for ABCG2

Breast cancer resistance protein polymorphism ABCG2 c.421C>A (rs2231142) moderates the effect of valproate on lamotrigine trough concentrations in adults with epilepsy

BACKGROUND

Valproate inhibits clearance of lamotrigine and greatly increases its concentrations. We assessed whether this effect was moderated by a polymorphism (ABCG2 c.421C>A) of the breast cancer resistance protein.

METHODS

In two consecutive independent studies in adults with epilepsy on lamotrigine monotherapy or cotreated with valproate: (i) Exposure to valproate was considered treatment, (ii) dose-adjusted lamotrigine troughs at steady state were the outcome, and (iii) ABCG2 c.421C>A genotype (wild-type [wt] homozygosity or variant carriage) was the tested moderator. We used entropy balancing (primary analysis) and exact/optimal full matching (secondary analysis) to control for confounding, including polymorphisms (and linked polymorphisms) suggested to affect exposure to lamotrigine (UGT1A4*3 c.142T>G, rs2011425; UGT2B7-161C>T, rs7668258; ABCB1 1236C>T, rs1128503) to generate frequentist and Bayesian estimates of valproate effects (geometric means ratios [GMR]).

RESULTS

The two studies yielded consistent results (replicated); hence, we analyzed combined data (total N = 471, 140 treated, 331 controls, 378 ABCG2 c.421C>A wt subjects, 93 variant carriers). Primary analysis: in variant carriers, valproate effect (GMR) on lamotrigine (treated, n = 21 vs. controls, n = 72) was around 60% higher than in wt subjects (treated, n = 119 vs. controls, n = 259)-ratio of GMRs 1.61 (95%CI 1.23-2.11) (frequentist) and 1.63 (95%CrI 1.26-2.10) (Bayes). Similar differences in valproate effects between variant carriers and wt subjects were found in the secondary analysis (valproate troughs up to 364 μmol/L vs. no valproate; or valproate ≥364 μmol/L vs. no valproate). Susceptibility of the estimates to unmeasured confounding was low.

CONCLUSION

Data suggest that polymorphism rs2231142 moderates the effect of valproate on exposure to lamotrigine.

Bearing variant alleles at uridine glucuronosyltransferase polymorphisms UGT2B7 -161C > T (rs7668258) or UGT1A4*3 c.142 T > G (rs2011425) has no relevant consequences for lamotrigine troughs in adults with epilepsy

PURPOSE

To estimate whether epilepsy patients with variant UGT2B7 -161C > T (rs7668258) or UGT1A4*3 c.142 T > G (rs2011425) alleles differ from their wild-type (wt) peers in exposure to lamotrigine.

METHODS

Consecutive adults on lamotrigine monotherapy or lamotrigine + valproate co-treatment undergoing routine therapeutic drug monitoring, otherwise generally healthy and free of interacting drugs, were genotyped for UGT2B7 -161C > T and UGT1A4*3 c.142 T > G. Heterozygous, variant homozygous, or combined heterozygous/variant homozygous subjects were compared to their wt controls for dose-adjusted lamotrigine troughs with adjustment for age, sex, body weight, rs7668258/rs2011425, polymorphisms of efflux transporter proteins ABCG2 c.421C > A (rs2231142) and ABCB1 1236C > T (rs1128503), and level of exposure to valproate using covariate entropy balancing.

RESULTS

Of the 471 included patients, 328 (69.6%) were on monotherapy and 143 were co-treated with valproate. Dose-adjusted lamotrigine troughs in UGT2B7 -161C > T heterozygous (CT, n = 237) or variant homozygous (TT, n = 115) subjects were closely similar to those in their wt controls (CC, n = 119): geometric means ratios (GMRs) (frequentist and Bayes) 1.00 (95%CI 0.86-1.16) and 1.00 (95%CrI 0.83-1.22) for CT vs. CC; and 0.97 (0.81-1.17) and 0.97 (0.80-1.20) for TT vs. CC subjects. Lamotrigine troughs were also closely similar in UGT1A4*3 c.142 T > G variant carriers (n = 106: 102 TG + 4 GG subjects) and wt controls (TT, n = 365): GMR = 0.95 (0.81-1.12) frequentist, 0.96 (0.80-1.16) Bayes. GMRs for variant carriers vs. wt controls were around unity also at different levels of exposure to valproate.

CONCLUSION

Dose-adjusted lamotrigine troughs in epilepsy patients with variant UGT2B7 -161C > T or UGT1A4*3 c.142 T > G alleles are equivalent to those in their respective wt peers.

Loss of Function ABCG2 c.421C>A (rs2231142) Polymorphism Increases Steady-State Exposure to Mycophenolic Acid in Stable Renal Transplant Recipients: An Exploratory Matched Cohort Study

INTRODUCTION

Polymorphism ABCG2 c.421C>A (rs2231142) results in reduced activity of the important drug efflux transporter breast cancer-resistance protein (BCRP/ABCG2). One study has suggested that it may affect enterohepatic recirculation of mycophenolic acid (MPA). We evaluated the effect of rs2231142 on steady-state exposure to MPA in renal transplant recipients.

METHODS

Consecutive, stable adult (age ≥ 16 years) renal transplant recipients on standard MPA-based immunosuppressant protocols (N = 68; 43 co-treated with cyclosporine, 25 with tacrolimus) underwent routine therapeutic drug monitoring after a week of initial treatment, and were genotyped for ABCG2 c.421C>A and 11 polymorphisms in genes encoding enzymes and transporters implicated in MPA pharmacokinetics. ABCG2 c.421C>A variant versus wild-type (wt) patients were matched with respect to demographic, biopharmaceutic, and genetic variables (full optimal combined with exact matching) and compared for dose-adjusted steady-state MPA pharmacokinetics [frequentist and Bayes (skeptical neutral prior) estimates of geometric means ratios, GMR].

RESULTS

Raw data (12 variant versus 56 wt patients) indicated around 40% higher total exposure (frequentist GMR = 1.45, 95% CI 1.10-1.91; Bayes = 1.38, 95% CrI 1.07-1.81) and around 30% lower total body clearance (frequentist GMR = 0.66, 0.58-0.90; Bayes = 0.71, 0.53-0.95) in variant carriers than in wt controls. The estimates were similar in matched data (11 variant versus 43 wt patients): exposure GMR = 1.41 (1.11-1.79) frequentist, 1.39 (1.15-1.81) Bayes, with 90.7% and 85.5% probability of GMR > 1.20, respectively; clearance GMR = 0.73 (0.58-0.93) frequentist, 0.71 (0.54-0.95) Bayes. Sensitivity analysis indicated low susceptibility of the estimates to unmeasured confounding.

CONCLUSIONS

Loss-off-function polymorphism ABCG2 c.421C>A increases steady-state exposure to MPA in stable renal transplant patients.

Case report: Hepatotoxicity and nephrotoxicity induced by methotrexate in a paediatric patient, what is the role of precision medicine in 2023?

Methotrexate is an immunosuppressant and chemotherapeutic agent used in the treatment of a range of autoimmune disorders and cancers. Its main serious adverse effects, bone marrow suppression and gastrointestinal complications, arise from its antimetabolite effect. Nevertheless, hepatotoxicity and nephrotoxicity are two widely described adverse effects of methotrexate. Its hepatotoxicity has been studied mainly in the low-dose, chronic setting, where patients are at risk of fibrosis/cirrhosis. Studies of acute hepatoxicity of high dose methotrexate, such as during chemotherapy, are scarce. We present the case of a 14-year-old patient who received high-dose methotrexate and subsequently developed acute fulminant liver failure and acute kidney injury. Genotyping of MTHFR (Methylene tetrahydrofolate reductase gene), ABCB1 (codes for P-glycoprotein, intestinal transport and biliary excretion), ABCG2 (codes for BCRP, intestinal transporter and renal excretion) and SLCO1B1 (codes for OATP1B1, hepatic transporter) identified variants in all the genes analysed that predicted a reduced rate of methotrexate elimination and thus may have contributed to the clinical situation of the patient. Precision medicine involving pharmacogenomic testing could potentially avoid such adverse drug effects.

ABCG2 and SLCO1B1 gene polymorphisms in the Croatian population

BACKGROUND

Organic anion-transporting polypeptide 1B1 (OATP1B1) and the ATP-binding cassette subfamily G member 2, ABCG2, are important transporters involved in the transport of endogenous substrates and xenobiotics, including drugs. Genetic polymorphisms of these transporters have effect on transporter activity. There is significant interethnic variability in the frequency of allele variants.

AIM

To determined allele and genotype frequencies of ABCG2 and SLCO1B1 genes in Croatian populations of European descent.

SUBJECTS AND METHODS

A total of 905 subjects (482 women) were included. Genotyping for ABCG2 c.421C > A (rs2231142) and for SLCO1B1 c.521T > C (rs4149056), was performed by real-time polymerase chain reaction (PCR) using TaqMan^® DME Genotyping Assays.

RESULTS

For ABCG2 c.421C > A, the frequency of CC, CA and AA genotypes was 81.4%, 17.8% and 0.8% respectively. The frequency of variant ABCG2 421 A allele was 9.7%. For SLCO1B1 c.521T > C, the frequency of TT, TC and CC genotypes was 61.7%, 34.8% and 3.5% respectively. The frequency of variant SLCO1B1 521 C allele was 20.9%.

CONCLUSION

The frequency of the ABCG2 and SLCO1B1 allelic variants and genotypes in the Croatian population is in accordance with other European populations. Pharmacogenetic analysis can serve to individualise drug therapy and minimise the risk of developing adverse drug reactions.

Pharmacogenomics of lipid-lowering agents: the impact on efficacy and safety

Hyperlipidemia is a significant risk factor for cardiovascular disease morbidity and mortality. The lipid-lowering drugs are considered the cornerstone of primary and secondary prevention of atherosclerotic cardiovascular disease. Unfortunately, the lack of efficacy and associated adverse effects, ranging from mild-to-moderate to potentially life-threatening, lead to therapy discontinuation. Numerous reports support the role of gene polymorphisms in drugs' pharmacokinetic parameters and their associated adverse reactions. Therefore, this study aims to understand the pharmacogenomics of lipid-lowering drugs and the impact of genetic variants of key genes on the drugs' efficacy and toxicity. Indeed, genetically guided lipid-lowering therapy enhances overall safety, improves drug adherence and achieves long-term therapy.

Drug metabolism and drug transport of the 100 most prescribed oral drugs

Safe and effective use of drugs requires an understanding of metabolism and transport. We identified the 100 most prescribed drugs in six countries and conducted a literature search on in vitro data to assess contribution of Phase I and II enzymes and drug transporters to metabolism and transport. Eighty-nine of the 100 drugs undergo drug metabolism or are known substrates for drug transporters. Phase I enzymes are involved in metabolism of 67 drugs, while Phase II enzymes mediate metabolism of 18 drugs. CYP3A4/5 is the most important Phase I enzyme involved in metabolism of 43 drugs followed by CYP2D6 (23 drugs), CYP2C9 (23 drugs), CYP2C19 (22 drugs), CYP1A2 (14 drugs) and CYP2C8 (11 drugs). More than half of the drugs (54 drugs) are known substrates for drug transporters. P-glycoprotein (P-gp) is known to be involved in transport of 30 drugs, while breast cancer resistance protein (BCRP) facilitates transport of 11 drugs. A considerable proportion of drugs are subject to a combination of Phase I metabolism, Phase II metabolism and/or drug transport. We conclude that the majority of the most frequently prescribed drugs depend on drug metabolism or drug transport. Thus, understanding variability of drug metabolism and transport remains a priority.

Genetic factors in treatment-related cardiovascular complications in survivors of childhood acute lymphoblastic leukemia

Aim: Cardiovascular disease represents one of the main causes of secondary morbidity and mortality in patients with childhood cancer. Patients & methods: To further address this issue, we analyzed cardiovascular complications in relation to common and rare genetic variants derived through whole-exome sequencing from childhood acute lymphoblastic leukemia survivors (PETALE cohort). Results: Significant associations were detected among common variants in the TTN gene, left ventricular ejection fraction (p ≤ 0.0005), and fractional shortening (p ≤ 0.001). Rare variants enrichment in the NOS1, ABCG2 and NOD2 was observed in relation to left ventricular ejection fraction, and in NOD2 and ZNF267 genes in relation to fractional shortening. Following stratification according to risk groups, the modulatory effect of rare variants was additionally found in the CBR1, ABCC5 and AKR1C3 genes. None of the associations was replicated in St-Jude Lifetime Cohort Study. Conclusion: Further studies are needed to confirm whether the described genetic markers may be useful in identifying patients at increased risk of these complications.

ABCB1 and ABCG2 Together Limit the Distribution of ABCB1/ABCG2 Substrates to the Human Retina and the ABCG2 Single Nucleotide Polymorphism Q141K (c.421C> A) May Lead to Increased Drug Exposure

The widely expressed and poly-specific ABC transporters breast cancer resistance protein (ABCG2) and P-glycoprotein (ABCB1) are co-localized at the blood-brain barrier (BBB) and have shown to limit the brain distribution of several clinically used ABCB1/ABCG2 substrate drugs. It is currently not known to which extent these transporters, which are also expressed at the blood-retinal barrier (BRB), may limit drug distribution to the human eye and whether the ABCG2 reduced-function single-nucleotide polymorphism (SNP) Q141K (c.421C > A) has an impact on retinal drug distribution. Ten healthy male volunteers (five subjects with the c.421CC and c.421CA genotype, respectively) underwent two consecutive positron emission tomography (PET) scans after intravenous injection of the model ABCB1/ABCG2 substrate [¹¹C]tariquidar. The second PET scan was performed with concurrent intravenous infusion of unlabelled tariquidar to inhibit ABCB1 in order to specifically reveal ABCG2 function.In response to ABCB1 inhibition with unlabelled tariquidar, ABCG2 c.421C > A genotype carriers showed significant increases (as compared to the baseline scan) in retinal radiotracer influx K₁ (+62 ± 57%, p = 0.043) and volume of distribution V_T (+86 ± 131%, p = 0.043), but no significant changes were observed in subjects with the c.421C > C genotype. Our results provide the first evidence that ABCB1 and ABCG2 may together limit the distribution of systemically administered ABCB1/ABCG2 substrate drugs to the human retina. Functional redundancy between ABCB1 and ABCG2 appears to be compromised in carriers of the c.421C > A SNP who may therefore be more susceptible to transporter-mediated drug-drug interactions at the BRB than non-carriers.

Oxypurinol pharmacokinetics and pharmacodynamics in healthy volunteers: Influence of BCRP Q141K polymorphism and patient characteristics

The missense variant, breast cancer resistance protein (BCRP) p.Q141K, which encodes a reduced function BCRP, has been linked to poor response to allopurinol. Using a multifaceted approach, we aimed to characterize the relationship(s) between BCRP p.Q141K, the pharmacokinetics (PK) and pharmacodynamics (PD) of oxypurinol (the active metabolite of allopurinol), and serum uric acid (SUA) levels. A prospective clinical study (NCT02956278) was conducted in which healthy volunteers were given a single oral dose of 300 mg allopurinol followed by intensive blood sampling. Data were analyzed using noncompartmental analysis and population PK/PD modeling. Additionally, electronic health records were analyzed to investigate whether clinical inhibitors of BCRP phenocopied the effects of the p.Q141K variant with respect to SUA. Subjects homozygous for p.Q141K had a longer half‐life (34.2 ± 12.2 h vs. 19.1 ± 1.42 h) of oxypurinol. The PK/PD model showed that women had a 24.8% lower volume of distribution. Baseline SUA was affected by p.Q141K genotype and renal function; that is, it changed by 48.8% for every 1 mg/dl difference in serum creatinine. Real‐world data analyses showed that patients prescribed clinical inhibitors of BCRP have higher SUA levels than those that have not been prescribed inhibitors of BCRP, consistent with the idea that BCRP inhibitors phenocopy the effects of p.Q141K on uric acid levels. This study identified important covariates of oxypurinol PK/PD that could affect its efficacy for the treatment of gout as well as a potential side effect of BCRP inhibitors on increasing uric acid levels, which has not been described previously.

ABC transporter superfamily. An updated overview, relevance in cancer multidrug resistance and perspectives with personalized medicine

The ATP binding-cassette superfamily corresponds the mostly transmembrane transporters family found in humans. These proteins actively transport endogenous and exogenous substrates through biological membranes in body tissues, so they have an important role in the regulation of many physiological functions necessary for human homeostasis, as well as in response regulation to several pharmacological substrates. The development of multidrug resistance has become one of the main troubles in conventional chemotherapy in different illnesses including cancer, being the increased efflux of antineoplastic drugs the main reason for this multidrug resistance, with a key role of the ABC superfamily. Likely, the interindividual variability in the pharmacological response among patients is well known, and may be due to intrinsically factors of the disease, genetic and environmental ones. Thus, the understanding of this variability, especially the genetic variability associated with the efficacy and toxicity of drugs, can provide a safer and more effective pharmacological treatment, so ABC genes are considered as important regulators due to their relationship with the reduction in pharmacological response. In this review, updated information about transporters belonging to this superfamily was collected, the possible role of these transporters in cancer, the role of genetic variability in their genes, as well as some therapeutic tools that have been tried to raise against main transporters associated with chemoresistance in cancer.

ABCB1, ABCG2 and CYP2D6 polymorphism effects on disposition and response to long-acting risperidone

The relevance of the multidrug resistance (ABCB1) and breast cancer resistance (ABCG2) protein transporter polymorphisms for treatment with long-acting intramuscular (LAI) risperidone is largely unknown. We explored the relationship between these polymorphisms and cytochrome P450 (CYP) 2D6 genotype-predicted phenotype in their effects on drug disposition and clinical outcomes in adults with schizophrenia. In a 24-week observational study, patients initiated on LAI-risperidone (n=101) were genotyped [enzymes (CYP2D6 dupl,*3,*4,*5,*6,*41; CYP3A4*22, CYP3A5*3), transporters (ABCG2 421C>A; ABCB1 1236C>T, 2677G>T/A, 3435C>T)] and evaluated for steady-state (weeks 6-8) serum levels of dose-corrected risperidone, 9-OH-risperidone, risperidone+9-OH-risperidone (active moiety), and for response to treatment (PANSS, reduction vs. baseline ≥30% at week 12 and ≥45% at week 24). CYP2D6 normal/ultrarapid metabolizers (NM/UM) (vs. other) had lower risperidone (29%) and active moiety levels (24%) (9-OH-risperidone not affected). The effect on the three analytes was mild (0 to 23% reduction) in ABCG2 wild-type homozygotes and pronounced (44-55% reduction) in ABCG2 variant allele carriers. ABCG2 variant had no effect on disposition in CYP2D6 "other" phenotypes, while the effect was pronounced in CYP2D6 NM/UM subjects (31-37% reduction). ABCB1 polymorphisms had no effect on exposure to risperidone. CYP2D6 NM/UM phenotype tended to lower odds of PANSS response, ABCG2 variant was associated with 4-fold higher odds and ABCB1 (1236C>T, 2677G>T/A, 3435C>T) overall mainly wild-type genotype was associated with around 4--fold lower odds of response. In patients treated with LAI-risperidone, CYP2D6 phenotype effect on systemic exposure is conditional on the ABCG2 421C>A polymorphism. ABCG2 and ABCB1 polymorphisms affect clinical response independently of systemic risperidone disposition.

Pharmacogenetics of Statin-Induced Myotoxicity

Statins, a class of lipid-lowering medications, have been a keystone treatment in cardiovascular health. However, adverse effects associated with statin use impact patient adherence, leading to statin discontinuation. Statin-induced myotoxicity (SIM) is one of the most common adverse effects, prevalent across all ages, genders, and ethnicities. Although certain demographic cohorts carry a higher risk, the impaired quality of life attributed to SIM is significant. The pathogenesis of SIM remains to be fully elucidated, but it is clear that SIM is multifactorial. These factors include drug-drug interactions, renal or liver dysfunction, and genetics. Genetic-inferred risk for SIM was first reported by a landmark genome-wide association study, which reported a higher risk of SIM with a polymorphism in the SLCO1B1 gene. Since then, research associating genetic factors with SIM has expanded widely and has become one of the foci in the field of pharmacogenomics. This review provides an update on the genetic risk factors associated with SIM.

Role of Genetic Variations in the Hepatic Handling of Drugs

The liver plays a pivotal role in drug handling due to its contribution to the processes of detoxification (phases 0 to 3). In addition, the liver is also an essential organ for the mechanism of action of many families of drugs, such as cholesterol-lowering, antidiabetic, antiviral, anticoagulant, and anticancer agents. Accordingly, the presence of genetic variants affecting a high number of genes expressed in hepatocytes has a critical clinical impact. The present review is not an exhaustive list but a general overview of the most relevant variants of genes involved in detoxification phases. The available information highlights the importance of defining the genomic profile responsible for the hepatic handling of drugs in many ways, such as (i) impaired uptake, (ii) enhanced export, (iii) altered metabolism due to decreased activation of prodrugs or enhanced inactivation of active compounds, and (iv) altered molecular targets located in the liver due to genetic changes or activation/downregulation of alternative/compensatory pathways. In conclusion, the advance in this field of modern pharmacology, which allows one to predict the outcome of the treatments and to develop more effective and selective agents able to overcome the lack of effect associated with the existence of some genetic variants, is required to step forward toward a more personalized medicine.

Alternative Polyadenylation of ABC Transporters of the C-Family (ABCC1, ABCC2, ABCC3) and Implications on Posttranscriptional Micro-RNA Regulation

ATP-binding cassette (ABC) transporters represent a large group of efflux pumps that are strongly involved in the pharmacokinetics of various drugs and nutrient distribution. It was recently shown that micro-RNAs (miRNAs) may significantly alter their expression as proven, e.g., for miR-379 and ABCC2 However, alternative mRNA polyadenylation may result in expression of 3'-untranslated regions (3'-UTRs) with varying lengths. Thus, length variants may result in presence or absence of miRNA binding sites for regulatory miRNAs with consequences on posttranscriptional control. In the present study, we report on 3'-UTR variants of ABCC1, ABCC2, and ABCC3 mRNA. Applying in vitro luciferase reporter gene assays, we show that expression of short ABCC2 3'-UTR variants leads to a significant loss of miR-379/ABCC2 interaction and subsequent upregulation of ABCC2 expression. Furthermore, we show that expression of ABCC2 3'-UTR lengths varies significantly between human healthy tissues but is not directly correlated to the respective protein level in vivo. In conclusion, the presence of altered 3'-UTR lengths in ABC transporters could lead to functional consequences regarding posttranscriptional gene expression, potentially regulated by alternative polyadenylation. Hence, 3'-UTR length variability may be considered as a further mechanism contributing to variability of ABCC transporter expression and subsequent drug variation in drug response. SIGNIFICANCE STATEMENT: micro-RNA (miRNA) binding to 3'-untranslated region (3'-UTR) plays an important role in the control of ATP-binding cassette (ABC)-transporter mRNA degradation and translation into proteins. We disclosed various 3'-UTR length variants of ABCC1, C2, and C3 mRNA, with loss of mRNA seed regions partly leading to varying and tissue-dependent interaction with miRNAs, as proven by reporter gene assays. Alternative 3'-UTR lengths may contribute to variable ABCC transporter expression and potentially explains inconsistent findings in miRNA studies.

Genetic polymorphisms analysis of pharmacogenomic VIP variants in Bai ethnic group from China

Background

The pharmacogenomics study has been widely used for the study of very important pharmacogenetic (VIP) variants among different ethnic groups. However, there is little known about the pharmacogenomics information regarding Bai family. Our study aimed to screen the polymorphism of the VIP gene in Bai nationality.

Methods

We genotyped 81 VIP variants (selected from the PharmGKB database) in the Bai population and then compared them to the other 11 major HapMap populations by chi‐square test, structure and F‐statistics (Fst) analysis.

Results

Our results indicated that rs20417 (PTGS2), rs4148323 (UGT1A), and rs1131596 (SLC19A1) were most different in Bai compared with most of the 11 populations from the HapMap data set. Furthermore, population structure and F‐statistics (Fst) analysis also demonstrated that the Bai population has the closest genetic relationship with Han Chinese in Beijing, China (CHB), followed by Japanese in Tokyo, Japan (JPT), and the farthest population from the Yoruba in Ibadan, Nigeria (YRI).

Conclusions

Our study not only presented the genotype frequency difference between the selected population of the Bai population and the other 11 populations, but also showed that the Bai population is most similar to the CHB populations, followed by JPT. These findings would contribute to the development of individualized medicine for the Bai population.

ABCG2 c.421C>A polymorphism alters nifedipine transport to breast milk in hypertensive breastfeeding women

Nifedipine, a known substrate to breast cancer resistance protein (ABCG2/BCRP), is used for the treatment of hypertension during breastfeeding. This study aimed to evaluate the effect of ABCG2 c.421C>A on nifedipine transfer to breast milk (BM) in hypertensive women. Nineteen hypertensive breastfeeding women treated with 20 mg nifedipine every 12 hours were investigated. Blood and BM samples were collected simultaneously 15-30 days after delivery and at least 15 days after drug treatment. Patients genotyped as ABCG2 c.421CC showed nifedipine plasma and BM concentrations ranging from 8.32-178.1 ng/mL and 4.8-58.5 ng/mL, respectively. ABCG2 c.421C>A showed a trend towards significance (p = 0.0793) on nifedipine in BM, with concentrations approximately 3 times higher in the heterozygous 421 CA (29 ng/mL) in comparison to 421 CC (10.5 ng/mL). Nifedipine BM/plasma ratio was significantly lower in 421CC when compared to 421CA (p = 0.01). In conclusion, ABCG2 c.421C>A polymorphism is associated with higher transfer of nifedipine to BM.

ATP-Binding Cassette Transporters in the Clinical Implementation of Pharmacogenetics

ATP-binding cassette (ABC) transporters are involved in a large number of processes and contribute to various human genetic diseases. Among other functions, ABC proteins are involved in the transport of multiple drugs through cells. Most of the genes coding for these transporters are highly polymorphic and DNA variants in these genes can affect the normal functioning of these proteins, affecting the way drugs are transported, increasing or decreasing drug levels. These changes in the intracellular and extracellular drug levels may be associated with altered drug effectiveness or severe drug-induced adverse events. This review presents a state-of-art of the most pharmacogenetics clinically relevant ABC transporters closed to the clinical implementation.

The fruit fly Drosophila melanogaster as an innovative preclinical ADME model for solute carrier membrane transporters, with consequences for pharmacology and drug therapy

Solute carrier membrane transporters (SLCs) control cell exposure to small-molecule drugs, thereby contributing to drug efficacy and failure and/or adverse effects. Moreover, SLCs are genetically linked to various diseases. Hence, in-depth knowledge of SLC function is fundamental for a better understanding of disease pathophysiology and the drug development process. Given that the model organism Drosophila melanogaster (fruit fly) expresses SLCs, such as for the excretion of endogenous and toxic compounds by the hindgut and Malpighian tubules, equivalent to human intestine and kidney, this system appears to be a promising preclinical model to use to study human SLCs. Here, we systematically compare current knowledge of SLCs in Drosophila and humans and describe the Drosophila model as an innovative tool for drug development.