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The emergence of adrenergic β2-receptor (ADRB2) blockers has revolutionized glaucoma treatment, while the discovery of prostaglandin analogs has further expanded therapeutic options. Organic anion transporting polypeptide 2A1 (OATP2A1/SLCO2A1) facilitates the corneal transport of topical prostaglandins into anterior segment of eye. Our study aims to elucidate the prevalence of genetic polymorphisms in the ADRB2 and OATP2A1 to address variations in therapeutic responses among glaucoma patients. The study cohort comprised primary open-angle glaucoma patients (POAG, n = 77), compared to non-glaucomatous controls (n = 60) to identify polymorphisms rs1042713 (Arg16Gly, A > G) and rs1042714 (Gln27Glu, C > G) in the ADRB2 gene and rs34550074 (Ala396Thr, A > G) in OATP2A1 gene, using Sanger sequencing. Among the enrolled subjects (n = 137), the POAG group exhibited significantly elevated intraocular pressure ( P  < 0.001) and cup-to-disc ratio ( P  < 0.0001). The GA genotype of rs1042713 ( P  < 0.01) and the GG genotype of rs1042714 ( P  < 0.05) were positively associated with POAG, while rs34550074 ( P  > 0.05) showed no significant correlation with the disease. This study reveals the association of the ADRB2 gene polymorphisms with POAG, whereas OATP2A1 polymorphism did not show significant correlation., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Introduction: Citrin is a calcium-bound aspartate-glutamate carrier protein encoded by the gene SLC25A13, mutations of which can cause citrin deficiency, an autosomal recessive disorder. The manifestations of citrin deficiency include neonatal intrahepatic choledeposits caused by citrin deficiency (NICCD: OMIM#605814), intermediate growth disorders and dyslipidemia caused by citrin deficiency, and citrullinemia type II (OMIM#603471) in adults. NICCD is a classical metabolic disorder that causes cholestasis in newborns., Patient Concern and Clinical Findings: Here, we present the case of a 2-month-old male patient treated in our hospital on March 20, 2023, due to "postnatal skin xanthochromia and transaminases higher than normal values". Since birth, the child's skin had yellowed all over the body, and his condition did not improve after multiple medical treatments., Diagnosis/intervention/outcomes: The child underwent full exome gene testing at the age of 2 months and 13 days, and the results indicated heterozygous deletion of exon 3 of the SLC25A13 gene, while genetic testing of the parents revealed no gene mutations. The variant was preliminarily judged as being pathogenic according to the ACMG guidelines, and the patient was diagnosed with "citrin deficiency". Skin yellowing eventually subsided, and liver function returned to normal without special treatment., Conclusions: Here, we report a rare case of citrin deficiency caused by a heterozygous deletion of the SLC25A13 gene. This case increases the clinical phenotypic profile of NICCD, suggesting that clinicians must be vigilant regarding such genetic metabolic diseases in the clinic for early diagnosis and treatment. NICCD should always be considered in the differential diagnosis of neonatal cholestasis., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc.)

Objective: Statins are the first-choice therapy for dyslipidemia, but their effectiveness can be influenced by genetic polymorphisms. This study was conducted to assess the association of variants of the solute carrier anion transporter family 1B1 (SLCO1B1) gene, which encodes a transporter involving the hepatic clearance of the statins and their therapeutic efficacy., Method: A systematic review was performed on four electronic databases to identify relevant studies. The pooled mean difference with 95% confidence interval (CI) in percentage change of concentration of LDL-C, total cholesterol (TC), HDL-C, and triglycerides was calculated. Heterogeneity between studies and publication bias, subgroup analyses, and sensitivity analyses were also carried out using R software., Results: Twenty-one studies on 24 365 participants and four variants [rs4149056 (c.521T>C), rs2306283 (c.388A>G), rs11045819 (c.463C>A), rs4363657 (g.89595T>C)] were analyzed. A statistically significant association was found between the LDL-C-lowering effectiveness and the rs4149056 and rs11045819 in the heterozygote model; and the rs4149056, rs2306283, and rs11045819 in the homozygote model. In the subgroup analyses, non-Asian populations, simvastatin, and pravastatin showed significant associations between LDL-C-lowering efficacy and the rs4149056 or rs2306283. Significant associations between the rs2306283 and HDL-C-increasing effectiveness were found in the homozygote model. Regarding TC-reducing, significant associations were observed in the heterozygote and homozygote models of the rs11045819. There was no heterogeneity and publication bias among most studies., Conclusion: SLCO1B1 variants can be used as signals to predict the statins' effectiveness., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Although atorvastatin (ATV) is well-tolerated, patients may report muscle complaints. These are difficult to predict owing to high interindividual variability. Such side effects are linked to intramuscular accumulation of ATV. This study aimed to investigate the relative role of transporters expressed in muscle tissue in promoting or limiting drug access to cells. The impact of common single nucleotide polymorphisms (SNPs) in SLCO2B1 coding for OATP2B1 and ABCC1 coding for MRP1 on ATV transport was also evaluated., Methods: HEK293 cells were stably transfected with plasmids containing cDNA encoding wild-type or variant SLCO2B1 and/or ABCC1 to generate single and double stable transfectant HEK293 recombinant models overexpressing variant or wild-type OATP2B1 (influx) and/or MRP1 (efflux) proteins. Variant plasmids were generated by site-directed mutagenesis. Expression analyses were performed to validate recombinant models. Accumulation and efflux experiments were performed at different concentrations. ATV was quantified by LC-MS/MS, and kinetic parameters were compared between single and double HEK transfectants expressing wild-type and variant proteins., Results: The results confirm the involvement of OATP2B1 and MRP1 in ATV cellular transport because it was demonstrated that intracellular accumulation of ATV was boosted by OATP2B1 overexpression, whereas ATV accumulation was decreased by MRP1 overexpression. In double transfectants, it was observed that increased ATV intracellular accumulation driven by OATP2B1 influx was partially counteracted by MRP1 efflux. The c.935G > A SNP in SLCO2B1 was associated with decreased ATV OATP2B1-mediated influx, whereas the c.2012G > T SNP in ABCC1 seemed to increase MRP1 efflux activity against ATV., Conclusions: Intracellular ATV accumulation is regulated by OATP2B1 and MRP1 transporters, whose functionality is modulated by natural genetic variants. This is significant because it may play a role in ATV muscle side-effect susceptibility., Competing Interests: The authors declare no conflict of interest., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology.)

Objective: Drug transporters are important determinants of drug disposition and response. Tamoxifen is an antiestrogen for breast cancer therapy known for adverse drug reactions (ADRs). In this study, the involvement of OATP transporters in tamoxifen and endoxifen transport was studied in vitro while the impact of single nucleotide variation (SNV) in OATP and efflux transporters P-glycoprotein ( ABCB1 ) and Breast Cancer Resistance Protein ( ABCG2 ) on ADRs during tamoxifen therapy were assessed., Methods: Patients receiving tamoxifen for breast cancer, who were CYP2D6 normal metabolizers were enrolled ( n  = 296). Patients completed a survey that captured ADRs and a blood sample was collected. Tamoxifen and endoxifen plasma concentration were measured, while DNA was genotyped for SNVs in ABCB1, ABCG2, SLCO1A2, SLCO1B1 , and SLCO2B1 . HEK293T cells were used to determine the extent of OATP-mediated transport of tamoxifen and endoxifen., Results: Common SNVs of ABCB1, ABCG2, SLCO1A2 , and SLCO1B1 were not associated with tamoxifen or endoxifen concentration. However, tamoxifen concentration was significantly higher in carriers of SLCO2B1 c.935G>A (129.8 ng/mL) compared to wildtype (114.9 ng/mL; P  = 0.036). Interestingly, subjects who carried SLCO1A2 c.38A>G reported significantly less dizziness ( P  = 0.016). In-vitro analysis demonstrated increased cellular accumulation of tamoxifen in cells overexpressing OATP1A2 and 1B1, but endoxifen uptake was not effected in OATP overexpressing cells., Conclusions: We showed that OATP1A2 , a transporter known to be expressed at the blood-brain barrier, is capable of tamoxifen transport. Additionally, OATP1A2 c.38A>G was associated with reduced ADRs. Taken together, our findings suggest genetic variation in OATP transporters may be an important predictor of tamoxifen ADRs., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose of Review: Capsule endoscopy and more sensitive radiological techniques have resulted in more enteropathies being detected. A rare disease of unknown aetiology, 'cryptogenic multifocal ulcerating stenosing enteritis' or 'chronic nonspecific multiple ulcers of the small intestine' (CNSU), has long been recognised. This review aims to describe how disease can be better diagnosed and differentiated from other small bowel inflammatory disorders., Recent Findings: Genetic studies have shown that some patients with CNSU (the term used in Japanese studies) express SLCO2A1 gene mutations, a gene which encodes a prostaglandin transporter expressed on vascular endothelium, allowing a more specific diagnosis of 'chronic enteropathy associated with SLCO2A1'. Mutations in the PLA2G4A gene result in cytosolic phospholipase A2α deficiency and reduced arachidonic acid for prostaglandin synthesis leading to a severe ulcerating, stenosing and fistulating small bowel disease., Summary: A 'prostaglandin-related enteropathy' should be considered in patients with atypical small bowel ulceration and stenosis. Genetic analysis will allow the detection of SLCO2A1 and PLA2G4A gene mutations. However, a careful history of medication use and a urinary metabolite screen may reveal the use of nonsteroidal anti-inflammatory drugs, a common cause of small bowel injury which is well recognised as being mediated by prostaglandin inhibition., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Background: We have previously shown that activation of cell-autonomous innate immune signaling facilitates the transdifferentiation of fibroblasts into induced endothelial cells, and is required to generate induced endothelial cells with high fidelity for endothelial lineage. Recent studies indicate that a glycolytic switch plays a role in induced pluripotent stem cell generation from somatic cells., Methods: Seahorse and metabolomics flux assays were used to measure the metabolic changes during transdifferentiation in vitro, and Matrigel plug assay was used to assess the effects of glycolysis modulators on transdifferentiation in vivo., Results: The metabolic switch begins rapidly after activation of innate immunity, before the expression of markers of endothelial lineage. Inhibiting glycolysis impaired, whereas facilitating glycolysis enhanced, the generation of induced endothelial cells. The toll-like receptor 3 agonist poly I:C increased expression of the mitochondrial citrate transporter Slc25A1, and the nuclear ATP-citrate lyase, in association with intracellular accumulation of citrate, the precursor for acetyl coenzyme A. These metabolic changes were coordinated with increased histone acetylation during transdifferentiation., Conclusion: Innate immune signaling promotes a glycolytic switch that is required for transdifferentiation, both processes being attenuated by ATP-citrate lyase knockdown. These data shed light on a novel link between metabolism and epigenetic modulation in transdifferentiation.

Background: Chronic kidney disease (CKD) increases cardiovascular risk. Underlying mechanisms, however, remain obscure. The uremic toxin indoxyl sulfate is an independent cardiovascular risk factor in CKD. We explored the potential impact of indoxyl sulfate on proinflammatory activation of macrophages and its underlying mechanisms., Methods: We examined in vitro the effects of clinically relevant concentrations of indoxyl sulfate on proinflammatory responses of macrophages and the roles of organic anion transporters and organic anion transporting polypeptides (OATPs). A systems approach, involving unbiased global proteomics, bioinformatics, and network analysis, then explored potential key pathways. To address the role of Delta-like 4 (Dll4) in indoxyl sulfate-induced macrophage activation and atherogenesis in CKD in vivo, we used 5/6 nephrectomy and Dll4 antibody in low-density lipoprotein receptor-deficient (Ldlr-/-) mice. To further determine the relative contribution of OATP2B1 or Dll4 to proinflammatory activation of macrophages and atherogenesis in vivo, we used siRNA delivered by macrophage-targeted lipid nanoparticles in mice., Results: We found that indoxyl sulfate-induced proinflammatory macrophage activation is mediated by its uptake through transporters, including OATP2B1, encoded by the SLCO2B1 gene. The global proteomics identified potential mechanisms, including Notch signaling and the ubiquitin-proteasome pathway, that mediate indoxyl sulfate-triggered proinflammatory macrophage activation. We chose the Notch pathway as an example of key candidates for validation of our target discovery platform and for further mechanistic studies. As predicted computationally, indoxyl sulfate triggered Notch signaling, which was preceded by the rapid induction of Dll4 protein. Dll4 induction may result from inhibition of the ubiquitin-proteasome pathway, via the deubiquitinating enzyme USP5. In mice, macrophage-targeted OATP2B1/Slco2b1 silencing and Dll4 antibody inhibited proinflammatory activation of peritoneal macrophages induced by indoxyl sulfate. In low-density lipoprotein receptor-deficient mice, Dll4 antibody abolished atherosclerotic lesion development accelerated in Ldlr-/- mice. Moreover, coadministration of indoxyl sulfate and OATP2B1/Slco2b1 or Dll4 siRNA encapsulated in macrophage-targeted lipid nanoparticles in Ldlr-/- mice suppressed lesion development., Conclusions: These results suggest that novel crosstalk between OATP2B1 and Dll4-Notch signaling in macrophages mediates indoxyl sulfate-induced vascular inflammation in CKD.

Introduction: Chronic nonspecific multiple ulcers of the small intestine (CNSU), an entity with female preponderance and manifestations including anemia and hypoproteinemia reflecting persistent gastrointestinal bleeding and intestinal protein loss, has been considered idiopathic. Umeno et al recently reported that CNSU is caused by loss-of-function mutations in the solute carrier organic anion transporter family member 2A1 gene (SLCO2A1) encoding a prostaglandin transporter, renaming the disorder "chronic enteropathy associated with SLCO2A1 gene mutation" (CEAS). Treatments for chronic enteropathies such as inflammatory bowel disease, including 5-aminosalicylic acid, corticosteroids, azathioprine, and anti-tumor necrosis factor-α antibody, often are ineffective in CEAS, which frequently requires surgery., Case Presentation: A 14-year-old girl had refractory anemia and hypoproteinemia for more than 2 years. Video capsule endoscopy showed nonspecific jejunal and ileal ulcers with varied sizes and shapes. She was diagnosed with CEAS resulting from compound heterozygous mutation of the SLCO2A1 gene. After corticosteroid treatment without improvement, azathioprine treatment improved her anemia and edema as hemoglobin and serum protein increased. Video capsule endoscopy 1 year after initiation of azathioprine showed improvement of small intestinal ulcers., Conclusion: Physicians should consider CEAS in patients with refractory anemia, hypoproteinemia, and multiple small intestinal ulcers. Why our patient responded to azathioprine but not to corticosteroids is unclear, but azathioprine might benefit some other patients with CEAS.

Objectives: Methotrexate (MTX), the key drug in childhood B-cell acute lymphoblastic leukemia (B-ALL) therapy, often causes toxicity. An association between genetic variants in MTX transport genes and toxicity has been found. It is known that these transporters are regulated by microRNAs (miRNAs), and miRNA single nucleotide polymorphisms (SNPs) interfere with miRNA levels or function. With regard to B-cell ALL, we have previously found rs56103835 in miR-323b that targets ABCC4 associated with MTX plasma levels. Despite these evidences and that nowadays a large amount of new miRNAs have been annotated, studies of miRNA polymorphisms and MTX toxicity are almost absent. Therefore, the aim of this study was to determine whether there are other variants in miRNAs associated with MTX levels., Patients and Methods: Blood samples of 167 Spanish patients with pediatric B-cell ALL treated with the LAL-SHOP protocol were analyzed. We selected all the SNPs described in pre-miRNAs with a minor allele frequency more than 1% (213 SNPs in 206 miRNAs) that could regulate MTX transporters because the miRNAs that target MTX transporter genes are not completely defined. Genotyping was performed with VeraCode GoldenGate platform., Results: Among the most significant results, we found rs56292801 in miR-5189, rs4909237 in miR-595, and rs78790512 in miR-6083 to be associated with MTX plasma levels. These miRNAs were predicted, in silico, to regulate genes involved in MTX uptake: SLC46A1, SLC19A1, and SLCO1A2., Conclusion: In this study, we detected three SNPs in miR-5189, miR-595, and miR-6083 that might affect SLC46A1, SLC19A1, and SLCO1A2 MTX transport gene regulation and could affect MTX levels in patients with pediatric B-cell ALL.

Objective: The effects of various polymorphisms in cytochrome P450 (CYP) enzyme and transporter genes on the pharmacokinetics (PK) of simvastatin were evaluated in healthy Korean men., Methods: Plasma concentration data for simvastatin and simvastatin acid were pooled from four phase I studies comprising 133 participants. The polymorphisms CYP2D6*4, CYP2D6*5, CYP2D6*14, CYP2D6*41, CYP3A5*3, CYP2C19*2, CYP2C19*3, CYP2A6*7, and CYP2A6*9; SLCO1B1 rs4149056, rs2306283, and rs4149015; ABCB1 rs1128503, rs2032582, and rs1045642; and ABCG2 rs2231142 were evaluated in each participant. Noncompartmental PK results were compared by genotype., Results: CYP2D6*5 and CYP2D6*14 were found to be associated with a higher area under the curve (AUC) for simvastatin, whereas the AUC of simvastatin acid was significantly increased in patients with the SLCO1B1 rs4149056, ABCG2 rs2231142, and CYP2D6*41 allele variants. Patients with the CYP2D6*41 variant showed a higher peak serum concentration (Cmax) of both simvastatin and simvastatin acid. The SLCO1B1 rs4149056 and rs4149015 polymorphisms were associated with an increased AUC ratio (i.e. ratio of simvastatin acid to simvastatin), whereas the SLCO1B1 rs4149056 and CYP2D6*5 variants were related to a higher Cmax ratio., Conclusion: The CYP2D6*5, CYP2D6*14, CYP2D6*41, CYP3A5*3, SLCO1B1 rs4149056 and rs4149015, and ABCG2 rs2231142 genetic polymorphisms are associated with the PK of both simvastatin and simvastatin acid. This could potentially be used as a basis for individualized simvastatin therapy by predicting the clinical outcomes of this treatment.

Statin-related myopathy is an important adverse effect of statin which is classically unpredictable. The evidence of association between solute carrier organic anion transporter 1B1 (SLCO1B1) gene T521C polymorphism and statin-related myopathy risk remained controversial. This study aimed to investigate this genetic association. Databases of PubMed, EMBASE, Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), Chinese Scientific Journals Database, and Wanfang Data were searched till June 17, 2015. Case-control studies investigating the association between SLCO1B1 gene T521C polymorphism and statin-related myopathy risk were included. The Newcastle-Ottawa Scale (NOS) was used for assessing the quality of included studies. Data were pooled by odds ratios (ORs) and their 95% confidence intervals (CIs). Nine studies with 1360 cases and 3082 controls were included. Cases of statin-related myopathy were found to be significantly associated with the variant C allele (TC + CC vs TT: OR = 2.09, 95% CI = 1.27-3.43, P = 0.003; C vs T: OR = 2.10, 95% CI = 1.43-3.09, P < 0.001), especially when statin-related myopathy was defined as an elevation of creatine kinase (CK) >10 times the upper limit of normal (ULN) or rhabdomyolysis (TC + CC vs TT: OR = 3.83, 95% CI = 1.41-10.39, P = 0.008; C vs T: OR = 2.94, 95% CI = 1.47-5.89, P = 0.002). When stratified by statin type, the association was significant in individuals receiving simvastatin (TC + CC vs TT: OR = 3.09, 95% CI = 1.64-5.85, P = 0.001; C vs T: OR = 3.00, 95% CI = 1.38-6.49, P = 0.005), but not in those receiving atorvastatin (TC + CC vs TT: OR = 1.31, 95% CI = 0.74-2.30, P = 0.35; C vs T: OR = 1.33, 95% CI = 0.57-3.12, P = 0.52). The available evidence suggests that SLCO1B1 gene T521C polymorphism is associated with an increased risk of statin-related myopathy, especially in individuals receiving simvastatin. Thus, a genetic test before initiation of statins may be meaningful for personalizing the treatment.

Objective: Organic anion transporting polypeptide 1B1 (OATP1B1, encoded by SLCO1B1 gene) is a hepatic uptake transporter, and its genetic variability is associated with pharmacokinetics and muscle toxicity risk of simvastatin. We examined the possible effects of variations in the SLCO1B1 gene on the pharmacokinetics of lovastatin in a prospective genotype panel study., Participants and Methods: Seven healthy volunteers with the SLCO1B1*1B/*1B genotype, five with the SLCO1B1*5/*15 or *15/*15 genotype, and 15 with the SLCO1B1*1A/*1A genotype (controls) were recruited. Each study participant ingested a single 40-mg dose of lovastatin. Plasma concentrations of lovastatin (inactive lactone) and its active metabolite lovastatin acid were measured up to 24 h., Results: In the SLCO1B1*5/*15 or *15/*15 genotype group, the geometric mean Cmax and AUC0-24 of lovastatin acid were 340 and 286% of the corresponding values in the SLCO1B1*1A/*1A (reference) genotype group (P<0.005). In contrast, the AUC0-24 of lovastatin acid in the SLCO1B1*1B/*1B genotype group was only 68% of that in the reference genotype group (P=0.03). No statistically significant association was observed between the SLCO1B1 genotype and the pharmacokinetics of lovastatin lactone., Conclusion: SLCO1B1*5/*15 and *15/*15 genotypes markedly increase the exposure to active lovastatin acid, but have no significant effect on lovastatin lactone, similar to their effects on simvastatin and simvastatin acid. Accordingly, it is probable that the risk of muscle toxicity during lovastatin treatment is increased in individuals carrying the SLCO1B1*5 or *15 allele. The SLCO1B1*1B/*1B genotype is associated with reduced lovastatin acid concentrations, consistent with enhanced hepatic uptake.

Our objective was to evaluate the associations of genetic variants affecting simvastatin (SV) and simvastatin acid (SVA) metabolism [the gene encoding cytochrome P450, family 3, subfamily A, polypeptide 4 (CYP3A4)*22 and the gene encoding cytochrome P450, family 3, subfamily A, polypeptide 5 (CYP3A5)*3] and transport [the gene encoding solute carrier organic anion transporter family member 1B1 (SLCO1B1) T521C] with 12-hour plasma SV and SVA concentrations. The variants were genotyped, and the concentrations were quantified by high performance liquid chromatography-tandem mass spectrometry in 646 participants of the Cholesterol and Pharmacogenetics clinical trial of 40 mg/d SV for 6 weeks. The genetic variants were tested for association with 12-hour plasma SV, SVA, or the SVA/SV ratio using general linear models. CYP3A5*3 was not significantly associated with 12-hour plasma SV or SVA concentration. CYP3A4*1/*22 participants had 58% higher 12-hour plasma SV concentration compared with CYP3A4*1/*1 participants (P = 0.006). SLCO1B1 521T/C and 521C/C participants had 71% (P < 0.001) and 248% (P < 0.001) higher 12-hour plasma SVA compared with SLCO1B1 521T/T participants, respectively. CYP3A4 and SLCO1B1 genotypes combined categorized participants into low (<1), intermediate (≈1), and high (>1) SVA/SV ratio groups (P = 0.001). In conclusion, CYP3A4*22 and SLCO1B1 521C were significantly associated with increased 12-hour plasma SV and SVA concentrations, respectively. CYP3A5*3 was not significantly associated with 12-hour plasma SV or SVA concentrations. The combination of CYP3A4*22 and SLCO1B1 521C was significantly associated with SVA/SV ratio, which may translate into different clinical SV risk/benefit profiles.

Background: The efficacy of statins, which are used commonly in primary and secondary prevention of cardiovascular diseases, shows a wide range of interindividual variability. Genetic variants of OATP1B1, a hepatic uptake transporter, can modify access of statins to its therapeutic target, thereby potentially altering drug efficacy. We studied the impact of genetic variants of OATP1B1 on the lipid-lowering efficacy of statins in a population-based setting., Materials and Methods: The basis of the analysis was the Study of Health in Pomerania, a cohort of 2732 men and women aged 20-81 years. Included in the statistical analysis to evaluate the impact of OATP1B1 on therapeutic efficacy of statins were 214 individuals diagnosed with dyslipidaemia during initial recruitment and receiving statins during the 5-year follow-up., Results: Analysing the impact of the OATP1B1 genotype, we observed a trend for lower statin-induced total cholesterol reduction in carriers of the SLCO1B1 512C variant. Restricting the analysis to patients receiving simvastatin, pravastatin, lovastatin and fluvastatin indicated a statistically significant association of the OATP1B1 genotype on lipid parameters at the 5-year follow-up. No such effect was observed for atorvastatin. Calculation of achievement of treatment goals according to the NCEP-ATPIII guidelines showed a lower rate of successful treatment when harbouring the mutant allele for patients taking simvastatin (46.7 vs. 73.9%). A similar trend was observed for pravastatin (34.4 vs. 70.4%)., Conclusion: Genetic variants of OATP1B1 leading to impaired hepatic uptake of statins translated into reduced drug efficacy in a population-based cohort.

Purpose of Review: To examine the current evidence concerning the effects of genetic variation on statin-related low-density lipoprotein cholesterol reductions, clinical efficacy, and adverse events and the relevance for patient care., Recent Findings: Recent years have seen the emergence of large-scale genetic experiments, including genome-wide association studies and candidate gene studies, exploring the impact of common genetic variation on patient response to statins. These studies have built on previous smaller scale evidence, providing improved statistical power and enhanced ability to explore the genome. Current evidence suggests that common genetic variants do not alter low-density lipoprotein cholesterol response by more than a few percent, or materially alter the effect of statin on vascular risk reduction, and therefore that patients benefit from statins independent of common genetic variation. However, knowledge of SLCO1B1 genotypes is believed to have clinical utility for predicting myopathy risk and ensuring that statins are prescribed as safely as possible. Furthermore, new hypothesis-generating studies, such as those associating GATM with myopathy risk, offer potential insights for the future., Summary: Common genetic variation does not appear to be an important determinant of statin response, with the exception of SLCO1B1 and risk of myopathy. Future studies will help to determine the impact of low-frequency and rare genetic variation on statin response.

Background: Triglycerides and their lipoprotein transport molecules are risk factors for heart disease. Observational studies have associated elevated levels of serum urate (SU) with triglycerides and risk of heart disease. However, owing to unmeasured confounding, observational studies do not provide insight into the causal relationship between SU and triglyceride. The aim of this study was to test for a causal role of SU in increasing triglyceride using Mendelian randomization that accounts for unmeasured confounding., Methods and Results: Subjects were of European ancestry from the atherosclerosis risk in communities (n=5237) and Framingham heart (n=2971) studies. Mendelian randomization by the 2-stage least squares regression method was done with SU as the exposure, a uric acid transporter genetic risk score as instrumental variable, and triglyceride as the outcome. In ordinary linear regression, SU was significantly associated with triglyceride levels (β=2.69 mmol/L change in triglyceride per mmol/L increase in SU). However, Mendelian randomization-based estimation showed no evidence for a direct causal association of SU with triglyceride concentration-there was a nonsignificant 1.01 mmol/L decrease in triglyceride per mmol/L increase in SU attributable to the genetic risk score (P=0.21). The reverse analysis using a triglyceride genetic risk score provided evidence of a causal role for triglyceride in raising urate in men (P(Corrected)=0.018)., Conclusions: These data provide no evidence for a causal role for SU in raising triglyceride levels, consistent with a previous Mendelian randomization report of no association between SU and ischemic heart disease., (© 2014 American Heart Association, Inc.)

Objectives: Osteosarcoma is the most common primary bone malignancy that occurs mostly in adolescents. Treatment protocols usually include multiagent preoperative and postoperative chemotherapy based on methotrexate, cisplatin, doxorubicin and ifosfamide. Despite a favourable prognosis, there are considerable interindividual differences in treatment outcome. Genetic variability of enzymes involved in the metabolism and transport of methotrexate could contribute towards observed differences in response to chemotherapy. Our aim was to evaluate how polymorphisms in the folate pathway and transporter genes influence treatment outcome in osteosarcoma patients., Patients and Methods: In total, 44 osteosarcoma patients treated with methotrexate were genotyped for eleven polymorphisms in four folate pathway and five folate transporter genes. Cox regression was used in survival analysis. Logistic regression was used to assess the influence of polymorphisms on treatment efficacy and toxicity and nonparametric tests were used to determine the influence on serum methotrexate levels., Results: Polymorphic SLCO1B1 rs4149056 and rs11045879 alleles were associated with significantly higher serum methotrexate area under the curve (P=0.001 and 0.011, respectively). Carriers of at least one polymorphic SLCO1B1 rs4149056 and rs11045879 allele tended to have longer event-free survival compared with patients with two wild-type alleles [P=0.040, hazard ratio (HR)=0.26, 95% confidence interval (CI)=0.07-0.94; and P=0.034, HR=0.20, 95% CI=0.05-0.89, respectively]. Compared with the most common haplotype, carriers of both polymorphic alleles had significantly longer event-free survival (P=0.009, HR=0.27, 95% CI=0.10-0.72)., Conclusion: We have shown that SLCO1B1 polymorphisms influence methotrexate disposition and survival in methotrexate-treated osteosarcoma patients and therefore might serve as pharmacogenetic markers of treatment outcome.

The CYP3A4*22 (c.522-191 C>T; rs35599367) single nucleotide polymorphism has been associated with lower CYP3A4 mRNA expression and activity. We investigated the association of CYP3A4*22 with the pharmacokinetics of lopinavir through a population pharmacokinetic approach. The minor allele frequency for CYP3A4*22 was 0.035, and seven of 375 patients had a combination of CYP3A4*22 and SLCO1B1 521T>C alleles. Lack of information on the ethnicity in this cohort should be considered as a limitation. However, in the final model, the population clearance was 5.9 l/h and patients with CYP3A4*22/*22 had 53% (P=0.023) lower clearance compared with noncarriers. In addition, the combined effect of CYP3A4*22 with SLCO1B1 521T>C (previously shown to be associated with lopinavir plasma concentration) was analysed. We observed a 2.3-fold higher lopinavir trough concentration (Ctrough) in individuals with CYP3A4*22/*22, a 1.8-fold higher Ctrough with SLCO1B1 521CC and a 9.7-fold higher Ctrough in individuals homozygous for both single nucleotide polymorphisms, compared with noncarriers. A simulated dose-reduction scenario showed that 200/100 mg lopinavir/ritonavir was adequate to achieve therapeutic concentration in individuals with CYP3A4*22/*22 alone or in combination with SLCO1B1 521CC. These data further our understanding of the genetic basis for variability in the pharmacokinetics of lopinavir.

Interpatient variability in drug response can be widely explained by genetically determined differences in metabolizing enzymes, drug transporters, and drug targets, leading to different pharmacokinetic and/or pharmacodynamic behaviors of drugs. Genetic variations affect or do not affect drug responses depending on their influence on protein activity and the relevance of such proteins in the pathway of the drug. Also, the frequency of such genetic variations differs among populations, so the clinical relevance of a specific variation is not the same in all of them. In this study, a panel of 33 single nucleotide polymorphisms in 14 different genes (ABCB1, ABCC2, ABCG2, CYP2B6, CYP2C19, CYP2C9, CYP3A4, CYP3A5, MTHFR, NOD2/CARD15, SLCO1A2, SLCO1B1, TPMT, and UGT1A9), encoding for the most relevant metabolizing enzymes and drug transporters relating to immunosuppressant agents, was analyzed to determine the genotype profile and allele frequencies in comparison with HapMap data. A total of 570 Spanish white recipients and donors of solid organ transplants were included. In 24 single nucleotide polymorphisms, statistically significant differences in allele frequency were observed. The largest differences (>100%) occurred in ABCB1 rs2229109, ABCG2 rs2231137, CYP3A5 rs776746, NOD2/CARD15 rs2066844, TPMT rs1800462, and UGT1A9 rs72551330. In conclusion, differences were recorded between the Spanish and other white populations in terms of allele frequency and genotypic distribution. Such differences may have implications in relation to dose requirements and drug-induced toxicity. These data are important for further research to help explain interindividual pharmacokinetic and pharmacodynamic variability in response to drug therapy.

Objective: The SLCO1B1 c.521T>C polymorphism is associated with statin plasma levels and simvastatin-induced adverse drug reactions. We studied whether the c.521T>C polymorphism is associated with dose decreases or switches to other cholesterol-lowering drugs during simvastatin and atorvastatin therapy, because these events are indicators of adverse drug reactions., Materials and Methods: We identified 1939 incident simvastatin and atorvastatin users in the Rotterdam Study, a population-based cohort study. Associations were studied using Cox proportional hazards analysis. Meta-analysis was performed with data from the Utrecht Cardiovascular Pharmacogenetics study., Results: Simvastatin users with the c.521 CC genotype had a significantly higher risk of a dose decrease or switch than users with the TT genotype [hazard ratio (HR) 1.74, 95% confidence interval (CI) 1.05-2.88]. Female sex, age below 70 years, and low starting dose were risk factors. In atorvastatin users with starting dose of more than 20 mg, the risk of a dose decrease or switch was higher in users carrying a C allele than in users with the TT genotype (HR 3.26, 95% CI 1.47-7.25). In the meta-analysis the association in simvastatin users remained, with a significantly higher risk of a dose decrease or switch in simvastatin users with two minor alleles (HR 1.69, 95% CI 1.05-2.73). For atorvastatin users no significant association was found., Conclusion: In simvastatin users in the Rotterdam Study, we demonstrated an association between the c.521T>C polymorphism and dose decrease or switching, as indicators of adverse drug reactions, and provided risk factors for this association. For atorvastatin, an association was found in users with a starting dose of more than 20 mg.

Objective: Membrane transporters are widely recognized as important determinants of drug disposition and response, generating increasing interest on the pharmacological implications of their genetic variations. The aim of this study was to elucidate the predictive/prognostic role of ATP-binding cassette (ABC) and solute carrier (SLC) protein polymorphisms on irinotecan (FOLFIRI regimen) outcome., Patients and Methods: A total of 250 White metastatic colorectal cancer patients homogenously treated with a first-line FOLFIRI regimen were genotyped for a panel of variants in five transporter genes. The primary study endpoints were the response rate (partial or complete response), overall survival, and time to progression. Toxicity was considered a secondary endpoint. Irinotecan pharmacokinetic data of 71 patients were used for polymorphism functional analysis., Results: Two variants of the ABCG2 (-15622C>T, rs7699188) gene were found to be predictive (P < 0.01) of the response rate. High-order relationships of ABC/SLC markers with previously investigated genetic (UGT1A1 polymorphisms) and nongenetic (primary tumor site) factors that helped determine the response rate were highlighted. A prognostic effect of the ABCB1 rs2032582 variant on patient overall survival emerged (P = 0.0074). The ABCG2 rs7699788 variant was also seen to be associated with grade 3-4 nonhematological toxicity (P = 0.0012). The ABCG2 (-15622C>T, rs7699188) and ABCB1 (rs2032582) polymorphisms were not found to be associated with pharmacokinetic parameters., Conclusion: This study showed that ABC/SLC polymorphisms have a crucial contribution toward the FOLFIRI outcome. This could represent a further step toward personalized therapy.

Purpose of Review: Recent advances in genome technology have provided us with a list of molecules affecting urate handling in humans, many of which are unlikely to be identified through traditional physiological approach alone. Although this article is focused on urate, this can be viewed as a successful model of genomics-physiology collaboration., Recent Findings: URATv1/GLUT9 (SLC2A9) is shown to play a critical role in urate reabsorption at the proximal tubule, probably more prominent than its partner URAT1 (SLC22A12). The major site of action of ABCG2 (ABCG2), an influential urate secretion transporter, has been shown to be the intestine rather than the kidney proximal tubule. Accordingly, hypofunction of ABCG2 leads to increased fractional excretion of urate, a finding traditionally interpreted as overproduction hyperuricemia. Some SLC17 family members secrete urate in the kidney or intestine. OAT2 (SLC22A7) may take up urate from blood to the proximal tubular cell. In addition, how a common single-nucleotide polymorphisms in ABCG2 affects its function has been elucidated., Summary: A finer grained picture of urate handling in the human body is now emerging, which will help choosing novel targets for urate-lowering therapy.

Background: A barrier to statin therapy is myopathy associated with elevated systemic drug exposure. Our objective was to examine the association between clinical and pharmacogenetic variables and statin concentrations in patients., Methods and Results: In total, 299 patients taking atorvastatin or rosuvastatin were prospectively recruited at an outpatient referral center. The contribution of clinical variables and transporter gene polymorphisms to statin concentration was assessed using multiple linear regression. We observed 45-fold variation in statin concentration among patients taking the same dose. After adjustment for sex, age, body mass index, ethnicity, dose, and time from last dose, SLCO1B1 c.521T>C (P<0.001) and ABCG2 c.421C>A (P<0.01) were important to rosuvastatin concentration (adjusted R(2)=0.56 for the final model). Atorvastatin concentration was associated with SLCO1B1 c.388A>G (P<0.01) and c.521T>C (P<0.05) and 4β-hydroxycholesterol, a CYP3A activity marker (adjusted R(2)=0.47). A second cohort of 579 patients from primary and specialty care databases were retrospectively genotyped. In this cohort, genotypes associated with statin concentration were not differently distributed among dosing groups, implying providers had not yet optimized each patient's risk-benefit ratio. Nearly 50% of patients in routine practice taking the highest doses were predicted to have statin concentrations greater than the 90th percentile., Conclusions: Interindividual variability in statin exposure in patients is associated with uptake and efflux transporter polymorphisms. An algorithm incorporating genomic and clinical variables to avoid high atorvastatin and rosuvastatin levels is described; further study will determine whether this approach reduces incidence of statin myopathy.

Objective: Genetic variation in drug metabolizing enzymes and membrane transporters as well as concomitant drug therapy can modulate the beneficial and the deleterious effects of drugs. We investigated whether patients exhibiting rhabdomyolysis who were taking cerivastatin possess functional genetic variants in SLCO1B1 and whether they were on concomitant medications that inhibit OATP1B1, resulting in accumulation of cerivastatin., Methods: This study had three components: (a) resequencing the SLCO1B1 gene in 122 patients who developed rhabdomyolysis while on cerivastatin; (b) functional evaluation of the identified SLCO1B1 nonsynonymous variants and haplotypes in in-vitro HEK293/FRT cells stably transfected with pcDNA5/FRT empty vector, SLCO1B1 reference, variants, and haplotypes; and (c) in-vitro screening of 15 drugs commonly used among the rhabdomyolysis cases for inhibition of OATP1B1-mediated uptake of cerivastatin in HEK293/FRT cells stably transfected with reference SLCO1B1., Results: The resequencing of the SLCO1B1 gene identified 54 variants. In-vitro functional analysis of SLCO1B1 nonsynonymous variants and haplotypes showed that the V174A, R57Q, and P155T variants, a novel frameshift insertion, OATP1B1*14 and OATP1B1*15 haplotype were associated with a significant reduction (P<0.001) in cerivastatin uptake (32, 18, 72, 3.4, 2.1 and 5.7% of reference, respectively). Furthermore, clopidogrel and seven other drugs were shown to inhibit OATP1B1-mediated uptake of cerivastatin., Conclusion: Reduced function of OATP1B1 related to genetic variation and drug-drug interactions likely contributed to cerivastatin-induced rhabdomyolysis. Although cerivastatin is no longer in clinical use, these findings may translate to related statins and other substrates of OATP1B1.

Objective: Among HIV-positive patients prescribed ritonavir-boosted lopinavir, SLCO1B1 521T→C (rs4149056) is associated with increased plasma lopinavir exposure. Protease inhibitors (PIs) are also substrates for cytochrome P450 (CYP) 3A and ABCB1, which are induced by NR1I2. We characterized relationships between ABCB1, CYP3A4, CYP3A5, NR1I2, and SLCO1B1 polymorphisms and trough PI concentrations among AIDS Clinical Trials Group study A5146 participants., Methods: At study entry, subjects with virologic failure on PI-containing regimens initiated new ritonavir-boosted PI regimens. We studied associations between week 2 PI plasma trough concentrations and 143 polymorphisms in these genes, including 4 targeted polymorphisms., Results: Among 275 subjects with both drug concentrations and genetic data, allelic frequencies of SLCO1B1 521T→C were 15%, 1%, and 8% in whites, blacks, and Hispanics, respectively. Further analyses were limited to 268 white, black, or Hispanic subjects who initiated ritonavir-boosted lopinavir (n = 98), fosamprenavir (n = 69), or saquinavir (n = 99). Of targeted polymorphisms, SLCO1B1 521T→C tended to be associated with higher lopinavir concentrations, with a 1.38-fold increase in the mean per C allele (95% confidence interval, 0.97-1.96; n = 98; P = 0.07). With fosamprenavir, SLCO1B1 521T→C was associated with lower amprenavir concentrations, with a 35% decrease in the mean per C allele (geometric mean ratio 0.65; 95% confidence interval, 0.44-0.94; n = 69; adjusted P = 0.02). There was no significant association with saquinavir concentrations, and none of the remaining 139 exploratory polymorphisms were statistically significant after correcting for multiple comparisons., Conclusions: With ritonavir-boosted PIs, a SLCO1B1 polymorphism that predicts higher lopinavir trough concentrations seems to predict lower amprenavir trough concentrations. The mechanism underlying this discordant association is uncertain.

Objective: A nonsynonymous single nucleotide polymorphism (SNP) in the SLCO2B1 gene encoding organic anion transporting polypeptide 2B1 (OATP2B1), c.935G>A (p.R312Q; rs12422149), has been associated with reduced plasma concentrations of montelukast in patients with asthma. Our aim was to examine the possible effects of the SLCO2B1 c.935G>A SNP on the single-dose pharmacokinetics of the suggested OATP2B1 substrates montelukast and aliskiren., Methods: Sixteen healthy volunteers with the SLCO2B1 c.935GG genotype, 12 with the c.935GA genotype, and five with the c.935AA genotype ingested a single 10 mg dose of montelukast or a 150 mg dose of aliskiren, with a washout period of 1 week. Plasma montelukast concentrations were measured up to 24 h. Plasma and urine aliskiren concentrations were measured up to 72 and 12 h, respectively, and plasma renin activity up to 24 h after aliskiren intake., Results: The SLCO2B1 genotypes had no significant effect on the pharmacokinetics of montelukast or aliskiren. The geometric mean ratios with 90% confidence intervals of montelukast area under the plasma concentration-time curve from 0 h to infinity (AUC(0-∞)) in participants with the c.935GA or the c.935AA genotype to those with the c.935GG genotype were 1.02 (0.87, 1.21) or 0.88 (0.71, 1.10), respectively (P=0.557). The geometric mean ratios (90% confidence interval) of aliskiren AUC(0-∞) in participants with the c.935GA or the c.935AA genotype to those with the c.935GG genotype were 0.98 (0.74, 1.30) or 1.24 (0.85, 1.80), respectively (P=0.576)., Conclusion: These data do not support the suggested functional significance of the SLCO2B1 c.935G>A SNP on OATP2B1 activity in vivo., (© 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins.)

Whole-genome studies have identified several intronic single nucleotide polymorphisms (SNPs) in SLCO1B1 associated with simvastatin-induced myopathy. The present study determined the effect of an intronic SNP rs4149081 in SLCO1B1 on the lipid-lowering effects of simvastatin and rosuvastatin in Chinese patients with hypercholesterolaemia. Lipid profiles were determined off treatment and after at least 4 weeks of treatment with each of the statins at daily doses of rosuvastatin 10 mg and simvastatin 40 mg. In 247 patients with good adherence, the rs4149081 G>A polymorphism was significantly associated with a 4.6 and 4.0% greater low-density lipoprotein cholesterol (LDL-C) reduction compared with those with wild-type alleles in response to rosuvastatin and simvastatin, respectively (P<0.05 for both). The 388A>G and 521T>C polymorphisms were not associated with the LDL-C response to either statin. The intronic SNP rs4149081 in SLCO1B1 was associated with the LDL-C response to statins in Chinese patients and this association was independent of the 521T>C polymorphism.

This study was designed to determine whether genetic polymorphisms of multidrug-resistant protein 2 (ABCC2), organic anion transporting polypeptide 1B1 (SLCO1B1), and breast cancer resistance protein (ABCG2) have an effect on olmesartan pharmacokinetics in Korean subjects. Sixty-eight healthy male volunteers who participated in previous pharmacokinetics studies of olmesartan medoxomil (single dose, 20 mg or 40 mg) were enrolled. All subjects were analyzed and grouped according to the genotypes of ABCC2, SLCO1B1, and ABCG2. The dose-normalized peak plasma concentration (C(max)) and area under the plasma concentration-time curve (AUCt) values were analyzed. The dose-normalized mean C(max) and AUC(t) in the ABCC2 -24CT genotype group were higher than those in the -24CC genotype group [C(max,dn): CT 26.1 ± 6.5 (ng/mL)/mg versus CC 22.1 ± 6.7 (ng/mL)/mg, P = 0.010, AUC(t,dn): CT 178.7 ± 45.6 (hr·ng(-1)·mL(-1))/mg versus CC 149.9 ± 39.8 (hr·ng(-1)·mL(-1))/mg, P = 0.010]. The difference in AUC(t,dn) between the ABCC2 -1549GG and -1549GA genotype groups was statistically significant [GG 149.0 ± 41.0 (hr·ng(-1)·mL(-1))/mg versus GA 174.1 ± 43.3 (hr·ng(-1)·mL(-1))/mg, P = 0.019]. No significant differences were observed for any other single nucleotide polymorphism in ABCC2, SLCO1B1, or ABCG2. The ABCC2 -24CC genotype group exhibited lower systemic exposure of olmesartan than the -24CT genotype group, whereas no significant differences were observed in the other transporter genotype groups.

Objective: We investigated the association between genetic polymorphisms in ABCB1 and SLCO1B and mycophenolic acid (MPA) pharmacokinetics, and MPA-related diarrhea and leukopenia in 338 kidney transplant recipients., Methods: A total of 338 patients participating in an international, randomized-controlled clinical trial were genotyped for ABCB1 and SLCO1B. Patients were all treated with mycophenolate mofetil and either cyclosporine or tacrolimus. MPA-area under the curve (AUCs), MPA-glucuronide AUCs and acylglucuronide-AUCs were measured on days 3 and 10, and months 1, 3, 6, and 12 after kidney transplantation., Results: The risk of developing diarrhea was 1.8-fold higher in patients cotreated with tacrolimus compared with patients cotreated with cyclosporine (95% confidence interval: 1.03-3.13; P=0.038). ABCB1 and SLCO1B SNPs were not associated with dose-adjusted exposure to MPA, MPA-glucuronide, nor acylglucuronide-MPA nor with the incidence of diarrhea or leukopenia., Conclusion: Genotyping for ABCB1 or SLCO1B pretransplantation is unlikely to be of clinical value for individualization of MPA therapy.

Objective: Interactions between coadministered drugs may unfavorably affect pharmacokinetics. This study evaluated whether fimasartan, an angiotensin receptor II antagonist, affected the pharmacokinetics of atorvastatin., Methods: A randomized, open-label, 2-period, 2-sequence, crossover, multiple-dosing study was conducted with 24 healthy male volunteers. Twelve subjects received 80-mg atorvastatin once daily for 7 days; later, they received 80-mg atorvastatin with 240-mg fimasartan for 7 days. Twelve other subjects received the same drugs in the opposite sequence. Blood samples were collected scheduled intervals for 24 hours after the last dosing to determine plasma concentrations of atorvastatin acid, atorvastatin lactone, 2-hydroxy atorvastatin acid, and 2-hydroxy atorvastatin lactone., Results: Compared with atorvastatin alone, coadministration of fimasartan and atorvastatin increased the atorvastatin acid mean (95% confidence interval) maximum concentration (Cmax,ss) by 1.89-fold (1.49-2.39) and the area under the concentration curve (AUCτ,ss) by 1.19-fold (0.96-1.48). Fimasartan also increased the mean 2-hydroxy atorvastatin acid Cmax,ss and AUCτ,ss by 2.45-fold (1.80-3.35) and 1.42-fold (1.09-1.85), respectively. The Cmax,ss and AUCτ,ss of the lactone forms of atorvastatin showed smaller changes than those observed for the acidic forms., Conclusion: We showed that fimasartan raised plasma atorvastatin concentrations. In vitro tests suggested that this effect may have been mediated by fimasartan inhibition of organic anion-transporting polypeptide 1B1.

Objective: Telmisartan is mainly taken up into the liver by organic anion transporting polypeptide (OATP) 1B3, conjugated with glucuronate, and excreted into the bile. We investigated the relationship between genotypes of metabolizing enzymes and transporters and pharmacokinetics of telmisartan in clinical study. We also checked which enzymes are responsible for telmisartan glucuronidation., Materials and Methods: We collected blood samples from 57 healthy volunteers who had participated in a clinical trial of telmisartan and examined the relationship between 14 mutations in six transporters/metabolic enzymes and pharmacokinetics of telmisartan. We also performed an in-vitro glucuronidation assay with recombinant uridine 5'-diphospho-glucuronosyltransferases isoforms and human liver microsomes., Results: In the clinical study, area under the plasma concentration-time curve value from time zero to infinity, of telmisartan in heterozygotes of SLCO1B3 (encoding protein: OATP1B3) rs11045585 tended to be larger than that in homozygotes of wild-type alleles. Unexpectedly, 19 heterozygotes of UGT1A1*28, whose function was decreased, significantly increased its oral clearance compared with homozygotes of UGT1A1*1 alleles (1090±690 vs. 620±430 ml/min/body). Metabolic clearance of telmisartan in human liver microsomes obtained from individuals with UGT1A1*28/*28 was higher compared with that of UGT1A1*1/*1 (168±33 vs. 93.3±27.3 μl/min/mg protein). Although telmisartan was metabolized by multiple UGT isoforms, in-vitro experiments revealed that UGT1A3 was estimated to be predominantly involved in telmisartan glucuronidation in human hepatocytes., Conclusion: UGT1A1*28 was thought to enhance the protein expression of UGT1A3 as reported most recently (Riedmaier et al. Clin Pharmacol Ther 2010; 87:65-73) and thereby increase glucuronidation activity of telmisartan and decrease the plasma concentration of telmisartan.

Objective: CYP3A5, MDR1 (ABCB1), and OATP1 (SLCO1B1) polymorphisms have been associated with variability in the pharmacokinetics (PK) of protease inhibitors. The aim of this study was to investigate the influence of CYP3A5 A6986G, ABCB1 (C3435T and G2677T), and SLCO1B1 (T521C and A388AG) polymorphisms on the PK and virologic outcome of lopinavir/ritonavir (LPV/RTV) in HIV-infected children., Design and Methods: We conducted a prospective cohort study in children (4-18 years old) on stable antiretroviral therapy with LPV/RTV. CYP3A5, ABCB1, and SLCO1B1 genotypes were determined using polymerase chain reaction amplification with allelic discrimination assays. The 12-hour plasma area under the concentration-time curves (AUC) and clearances (CL) of LPV and RTV were estimated using noncompartmental models. HIV RNA viral load was evaluated every 12 weeks for a total study period of 52 weeks. Analysis of covariance models with adjustment for age and adherence and allometric adjustment of CL were used to assess associations between studied polymorphisms and AUC, CL, and HIV RNA., Results: Fifty children (median age 11.2 years) were enrolled. Allele frequencies of the genotypes studied were in Hardy-Weinberg equilibrium. There was no statistically significant association between LPV or RTV AUC or CL, and CYP3A5, ABCB1, or SLCO1B1 A388G polymorphisms. There was a significant association between SLCO1B1 T521C genotype and increased LPV AUC (P = 0.042) and a nearly significant association with decreased LPV CL (P = 0.063). None of the studied polymorphisms, including SLCO1B1 T521C, were associated with virologic outcome during 52 weeks of study follow-up., Conclusions: There was no statistically significant influence of the CYP3A5, ABCB1, or SLCO1B1 A388AG polymorphisms on the PK and virologic outcome of LPV/RTV in HIV-infected children. SLCO1B1 T521C polymorphism was significantly associated with an increase in LPV AUC but was not associated with undetectable HIV RNA during the study period.

Objective: The withdrawal of cerivastatin involved an uncommon but serious adverse reaction, rhabdomyolysis. The bimodal response, rhabdomyolysis in a small proportion of users, points to genetic factors as a potential cause. We conducted a case-control study to evaluate genetic markers for cerivastatin-associated rhabdomyolysis., Methods: This study had two components: a candidate gene study to evaluate variants in CYP2C8, UGT1A1, UGT1A3, and SLCO1B1; and a genome-wide association study to identify risk factors in other regions of the genome. A total of 185 rhabdomyolysis cases were frequency matched to statin-using controls from the Cardiovascular Health Study (n=374) and the Heart and Vascular Health Study (n=358). Validation relied on functional studies., Results: Permutation test results suggested an association between cerivastatin-associated rhabdomyolysis and variants in SLCO1B1 (P=0.002), but not variants in CYP2C8 (P=0.073) or UGTs (P=0.523). An additional copy of the minor allele of SLCO1B1 rs4149056 (p.Val174Ala) was associated with the risk of rhabdomyolysis (odds ratio: 1.89; 95% confidence interval: 1.40-2.56). In transfected cells, this variant reduced cerivastatin transport by 40% compared with the reference transporter (P<0.001). The genome-wide association study identified an intronic variant (rs2819742) in the ryanodine receptor 2 gene (RYR2) as significant (P=1.74E-07). An additional copy of the minor allele of the RYR2 variant was associated with a reduced risk of rhabdomyolysis (odds ratio: 0.48; 95% confidence interval: 0.36-0.63)., Conclusion: We identified modest genetic risk factors for an extreme response to cerivastatin. Disabling genetic variants in the candidate genes were not responsible for the bimodal response to cerivastatin.

This study explored the association of 14 single nucleotide polymorphisms in three genes coding for influx transporters (SLC22A1, SLCO1B1, and SLCO1B3), two genes coding for efflux transporters (ABCB1 and ABCG2), and four genes coding for enzymes (CYP2C9, CYP2C19, CYP2D6, and CYP3A5) with the pharmacokinetics of imatinib in Japanese patients with chronic myeloid leukemia. Pharmacokinetic parameters were estimated by a population pharmacokinetic analysis based on 622 plasma samples from 34 patients at steady state. Approximately 4.6-fold variability in individual clearance was observed (range, 3.4-15.5 L/hr). The individual estimated clearance was significantly increased in patients with the SLCO1B3 334GG genotype (median value ± standard deviation, 9.5 ± 3.1 L/hr; n = 19) compared with SLCO1B3 334TT and TG genotypes (7.0 ± 3.1 L/hr; n = 15) (P = 0.019). Patients with the ABCB1 3435CC genotype had significantly higher imatinib clearance (12.7 ± 3.0 L/hr; n = 7) compared with patients with ABCB1 3435CT and TT genotypes (7.9 ± 2.7 L/hr; n = 27) (P = 0.035). In conclusion, the present study suggests that single nucleotide polymorphisms of the influx transporter SLCO1B3 and the efflux transporter ABCB1 were functionally associated with individual variability of imatinib pharmacokinetics in Japanese patients with chronic myeloid leukemia.

Objective: The objective was to determine the effects of the SLCO2B1 c.1457C> T polymorphism and apple juice on the pharmacokinetics of fexofenadine and midazolam in humans., Methods: Individuals were divided based on the genotype of SLCO2B1 c.1457C> T (n = 14, c.[1457C]+ c.[= ] 5,c.[1457C]+ c.[1457C> T] 5, and c.[1457C> T]+c.[1457C> T] 4). The oral pharmacokinetics of 60 mg fexofenadine and 5mg midazolam were assessed with water or apple juice (1200 ml/day) in a randomized crossover study. OATP2B1-mediated uptake of fexofenadine and midazolam was evaluated with Xenopus laevis oocyte gene-expression system., Results: When fexofenadine was administered with water, subjects with c.[1457C> T] allele showed a significant decrease in fexofenadine in the area under the plasma concentration-time curve (AUC) compared with c.[1457C] + c[= ] subjects (1110 ± 347 vs. 1762 ± 542 ng . h/ml, P< 0.05). When administered with apple juice, a significant decrease in the fexofenadine AUC was observed compared with water (1342 ± 519 vs. 284 ± 79.2 ng . h/ml, P < 0.05). The apple juice induced decrease in fexofenadine AUC was significantly lower in subjects carrying the c.[1457C> T] allele. Neither the genotype nor the apple juice showed significant effects on the pharmacokinetics of midazolam except for a marginally significant decrease in Cmax after administration with apple juice. The uptake of fexofenadine by OATP2B1 cRNA-injected oocytes was significantly higher than that by water-injected oocytes. Apple juice, but not midazolam, significantly decreased the uptake of fexofenadine by OATP2B1 cRNA-injected oocytes., Conclusion: The results suggest that fexofenadine is a substrate of OATP2B1, and the transport function of OATP2B1 is subject to the genotype of SLCO2B1 c.1457C> T and apple juice. It is likely that apple juice has little effect on CYP3A.

Background: Organic anion transporting polypeptides (OATPs) are emerging as major determinants of pharmacokinetics for numerous drugs, with the 1B1 isoform-mediating hepatic uptake. The 521 T>C polymorphism has been correlated earlier with higher plasma concentrations of several drugs and the aim of this study was to determine whether this polymorphism influences trough concentrations of maraviroc., Methods: The uptake of maraviroc by OATP1B1 was assessed using a heterologous Xenopus laevis oocyte expression system and quantified using a novel liquid chromatography-mass spectrometry method. Regression analyses were conducted to identify factors associated with maraviroc Ctrough in 59 patients treated with maraviroc at 150, 300, or 600 mg twice daily., Results: Maraviroc was identified as a substrate for OATP1B1 with a Km of 33.9 μmol/l. A dose of 600 mg of etravirine or efavirenz [odds ratio (OR) = 0.22, 95% confidence interval (95% CI): 0.06-0.76; P = 0.016] and SLCO1B1 521 heterozygosity were both associated with maraviroc Ctrough, above the suggested target concentration of 50 ng/ml (OR = 20.3, 95% CI: 2.2-182; P = 0.007)., Conclusion: These findings show the importance of OATP1B1 for variability in maraviroc pharmacokinetics. Furthermore, the SLCO1B1 521 T>C polymorphism maybe useful in predicting higher plasma concentrations but these data should be confirmed before prospective clinical studies to define the clinical usefulness.

Purpose of Review: This review summarizes the recent progress in understanding of myopathies induced by therapeutic agents, the underlying pathogenetic mechanisms and the management of iatrogenic muscle disorders, focussing on statin-associated myopathies., Recent Findings: Recent reports from observational studies have provided further information on the frequency of statin-associated myalgia and myopathy, which is the most important group of iatrogenic muscle disorders in current clinical practice, and on the relative myotoxicity of different statins and interactions with other therapeutic agents. However, there is still a need for further prospective studies with more clearly defined diagnostic criteria for statin myopathy and comparative studies of patient cohorts treated with different statins to determine the true incidence of myopathy as an adverse effect. Other important advances include recognition that genetic variants and mutations in the SLCO1B1, CYP and COQ2 genes may determine individual susceptibility to statin myopathy, and that statins may also initiate immune-mediated forms of necrotizing and inflammatory myopathy and unmask or aggravate various metabolic myopathies and other neuromuscular disorders., Summary: Recent reports have broadened the spectrum of iatrogenic myopathies and neuromuscular disorders associated with statins, and have thrown further light on the role of genetic predisposing factors, the mechanisms of myotoxicity and the management of such cases.

Adverse drug reactions are a significant public health problem that leads to mortality, hospital admissions, an increased length of stay, increasing healthcare costs, and withdrawal of drugs from market. Intensive care unit patients are particularly vulnerable and are at an elevated risk. Critical care practitioners, regulatory agencies, and the pharmaceutical industry aggressively seek biomarkers to mitigate patient risk. The rapidly expanding field of pharmacogenomics focuses on the genetic contributions to the variability in drug response. Polymorphisms may explain why some groups of patients have the expected response to pharmacotherapy whereas others experience adverse drug reactions. Historically, genetic association studies have focused on characterizing the effects of variation in drug metabolizing enzymes on pharmacokinetics. Recent work has investigated drug transporters and the variants of genes encoding drug targets, both intended and unintended, that comprise pharmacodynamics. This has led to an appreciation of the role that genetics plays in adverse drug reactions that are either predictable extensions of a drug's known therapeutic effect or idiosyncratic.This review presents the evidence for a genetic predisposition to adverse drug reactions, focusing on gene variants producing alterations in drug pharmacokinetics and pharmacodynamics in intensive care unit patients. Genetic biomarkers with the strongest associations to adverse drug reaction risk in the intensive care unit are presented along with the medications involved. Variant genotypes and phenotypes, allelic frequencies in different populations, and clinical studies are discussed. The article also presents the current recommendations for pharmacogenetic testing in clinical practice and explores the drug, patient, research study design, regulatory, and practical issues that presently limit more widespread implementation.

Background: Pharmacogenetics aims to maximize benefits and minimize risks of drug treatment. Our objectives were to examine the influence of common variants of hepatic metabolism and transporter genes on the lipid-lowering response to statin therapy., Methods and Results: The Genetic Effects On STATins (GEOSTAT-1) Study was a genetic substudy of Secondary Prevention of Acute Coronary Events-Reduction of Cholesterol to Key European Targets (SPACE ROCKET) (a randomized, controlled trial comparing 40 mg of simvastatin and 10 mg of rosuvastatin) that recruited 601 patients after myocardial infarction. We genotyped the following functional single nucleotide polymorphisms in the genes coding for the cytochrome P450 (CYP) metabolic enzymes, CYP2C9*2 (430C>T), CYP2C9*3 (1075A>C), CYP2C19*2 (681G>A), CYP3A5*1 (6986A>G), and hepatic influx and efflux transporters SLCO1B1 (521T>C) and breast cancer resistance protein (BCRP; 421C>A). We assessed 3-month LDL cholesterol levels and the proportion of patients reaching the current LDL cholesterol target of <70 mg/dL (<1.81 mmol/L). An enhanced response to rosuvastatin was seen for patients with variant genotypes of either CYP3A5 (P=0.006) or BCRP (P=0.010). Furthermore, multivariate logistic-regression analysis revealed that patients with at least 1 variant CYP3A5 and/or BCRP allele (n=186) were more likely to achieve the LDL cholesterol target (odds ratio: 2.289; 95% CI: 1.157, 4.527; P=0.017; rosuvastatin 54.0% to target vs simvastatin 33.7%). There were no differences for patients with variants of CYP2C9, CYP2C19, or SLCO1B1 in comparison with their respective wild types, nor were differential effects on statin response seen for patients with the most common genotypes for CYP3A5 and BCRP (n=415; odds ratio: 1.207; 95% CI: 0.768, 1.899; P=0.415)., Conclusion: The LDL cholesterol target was achieved more frequently for the 1 in 3 patients with CYP3A5 and/or BCRP variant genotypes when prescribed rosuvastatin 10 mg, compared with simvastatin 40 mg. Clinical Trial Registration- URL: http://isrctn.org. Unique identifier: ISRCTN 89508434.

Background: An ADME (absorption, distribution, metabolism and excretion)-pharmacogenetics association study may identify functional variants relevant to the pharmacokinetics of lopinavir co-formulated with ritonavir (LPV/r), a first-line anti-HIV agent., Methods: An extensive search of literature and web resources helped select ADME genes and single nucleotide polymorphisms (SNPs, functional and HapMap tagging SNPs) with a proven or potentially relevant role in LPV/r pharmacokinetics. The study followed a two-stage design. Stage 1 (discovery) considered a Caucasian population (n=638) receiving LPV/r, where we selected 117 individuals with low LPV clearance (cases) and 90 individuals with high clearance (controls). Genotyping was performed by a 1536-SNP customized GoldenGate Illumina BeadArray. Stage 2 (confirmation) represented a replication study of candidate SNPs from the stage 1 in 148 individuals receiving LPV/r. The analysis led to formal population pharmacokinetic-pharmacogenetic modeling of demographic, environmental and candidate SNP effects., Results: One thousand three hundred and eighty SNPs were successfully genotyped. Nine SNPs prioritized by the stage 1 analysis were brought to replication. Stage 2 confirmed the contribution of two functional SNPs in SLCO1B1, one functional SNP in ABCC2 and a tag SNP of the CYP3A locus in addition to body weight effect and ritonavir coadministration. According to the population pharmacokinetic-pharmacogenetic model, genetic variants explained 5% of LPV variability. Individuals homozygous rs11045819 (SLCO1B1*4) had a clearance of 12.6 l/h, compared with 5.4 l/h in the reference group, and 3.9 l/h in individuals with two or more variant alleles of rs4149056 (SLCO1B1*5), rs717620 (ABCC2) or rs6945984 (CYP3A). A subanalysis confirmed that although a significant part of the variance in LPV clearance was attributed to fluctuation in ritonavir levels, genetic variants had an additional effect on LPV clearance., Conclusion: The two-stage strategy successfully identified genetic variants affecting LPV/r pharmacokinetics. Such a general approach of ADME pharmacogenetics should be generalized to other drugs.

Rationale: The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, or statins, are important drugs used in the treatment and prevention of cardiovascular disease. Although statins are well tolerated, many patients develop myopathy manifesting as muscle aches and pain. Rhabdomyolysis is a rare but severe toxicity of statins. Interindividual differences in the activities of hepatic membrane drug transporters and metabolic enzymes are known to influence statin plasma pharmacokinetics and risk for myopathy. Interestingly, little is known regarding the molecular determinants of statin distribution into skeletal muscle and its relevance to toxicity., Objective: We sought to identify statin transporters in human skeletal muscle and determine their impact on statin toxicity in vitro., Methods and Results: We demonstrate that the uptake transporter OATP2B1 (human organic anion transporting polypeptide 2B1) and the efflux transporters, multidrug resistance-associated protein (MRP)1, MRP4, and MRP5 are expressed on the sarcolemmal membrane of human skeletal muscle fibers and that atorvastatin and rosuvastatin are substrates of these transporters when assessed using a heterologous expression system. In an in vitro model of differentiated, primary human skeletal muscle myoblast cells, we demonstrate basal membrane expression and drug efflux activity of MRP1, which contributes to reducing intracellular statin accumulation. Furthermore, we show that expression of human OATP2B1 in human skeletal muscle myoblast cells by adenoviral vectors increases intracellular accumulation and toxicity of statins and such effects were abrogated when cells overexpressed MRP1., Conclusions: These results identify key membrane transporters as modulators of skeletal muscle statin exposure and toxicity.

Background: Prostaglandin E(2) (PGE(2)) plays a major role both in maintaining patency of the fetal ductus arteriosus and in closure of the ductus arteriosus after birth. The rate-limiting step in PGE(2) signal termination is PGE(2) uptake by the transporter PGT., Methods and Results: To determine the role of PGT in ductus arteriosus closure, we used a gene-targeting strategy to produce mice in which PGT exon 1 was flanked by loxP sites. Successful targeting was obtained because neither mice hypomorphic at the PGT allele (PGT Neo/Neo) nor global PGT knockout mice (PGT(-/-)) exhibited PGT protein expression; moreover, embryonic fibroblasts isolated from targeted mice failed to exhibit carrier-mediated PGE(2) uptake. Although born in a normal mendelian ratio, no PGT(-/-) mice survived past postnatal day 1, and no PGT Neo/Neo mice survived past postnatal day 2. Necropsy revealed patent ductus arteriosus with normal intimal thickening but dilated cardiac chambers. Both PGT Neo/Neo and PGT(-/-) mice could be rescued through the postnatal period by giving the mother indomethacin before birth. Rescued mice grew normally and had no abnormalities by gross and microscopic postmortem analyses. In accordance with the known role of PGT in metabolizing PGE(2), rescued adult PGT(-/-) mice had lower plasma PGE(2) metabolite levels and higher urinary PGE(2) excretion rates than wild-type mice., Conclusions: PGT plays a critical role in closure of the ductus arteriosus after birth by ensuring a reduction in local and/or circulating PGE(2) concentrations.

Objective: OATP1B1 and OATP1B3 are major hepatic drug transporters whilst OATP1A2 is mainly located in the brain but is also located in liver and several other organs. These transporters affect the distribution and clearance of many endobiotics and xenobiotics and have been reported to have functional single nucleotide polymorphisms (SNPs). We have assessed the substrate specificities of these transporters for a panel of antiretrovirals and investigated the effects of SNPs within these transporters on the pharmacokinetics of lopinavir., Methods: SLCO1A2, SLCO1B1 and SLCO1B3 were cloned, verified and used to generate cRNA for use in the Xenopuslaevis oocyte transport system. Using the oocyte system, antiretrovirals were tested for their substrate specificities. Plasma samples (n=349) from the Liverpool therapeutic drug monitoring registry were genotyped for SNPs in SLCO1A2, SLCO1B1 and SLCO1B3 and associations between SNPs and lopinavir plasma concentrations were analysed., Result: Antiretroviral protease inhibitors, but not non-nucleoside reverse transcriptase inhibitors, are substrates for OATP1A2, OATP1B1 and OATP1B3. Furthermore, ritonavir was not an inhibitor of OATP1B1. The 521T>C polymorphism in SLCO1B1 was significantly associated with higher lopinavir plasma concentrations. No associations were observed with functional variants of SLCO1A2 and SLCO1B3., Conclusion: These data add to our understanding of the factors that contribute to variability in plasma concentrations of protease inhibitors. Further studies are now required to confirm the association of SLCO1B1 521T>C with lopinavir plasma concentrations and to assess the influence of other polymorphisms in the SLCO family.