SLCO1B1 Genotype Research Articles

Differential effect of the rs4149056 variant in SLCO1B1 on myopathy associated with simvastatin and atorvastatin

Statins reduce cardiovascular morbidity and mortality in appropriately selected patients. However, statin-associated myopathy is a significant risk associated with these agents. Recently, variation in the SLCO1B1 gene was reported to predict simvastatin-associated myopathy. The aim of this study was to replicate association of the rs4149056 variant in SLCO1B1 with severe statin-associated myopathy in a cohort of patients using a variety of statin medications and to investigate the association with specific statin types. We identified 25 cases of severe statin-associated myopathy and 84 controls matched for age, gender, statin type and dose. The rs4149056 variant in SLCO1B1 was not significantly associated with myopathy in this group as a whole. However, when subjects were stratified by statin type, the SLCO1B1 rs4149056 genotype was significantly associated with myopathy in patients who received simvastatin, but not in patients who received atorvastatin. Our findings provide further support for a role for SLCO1B1 genotype in simvastatin-associated myopathy, and suggest that this association may be stronger for simvastatin compared with atorvastatin.

SLCO1B1 Polymorphism and Oral Antidiabetic Drugs

Organic anion-transporting polypeptide 1B1 (OATP1B1; gene: SLCO1B1) is an influx transporter expressed on the sinusoidal membrane of human hepatocytes, where it mediates the uptake of its substrates from blood into liver. In vitro, the SLCO1B1 c.521T>C (p.Val174Ala) single-nucleotide polymorphism (SNP) has been associated with reduced and the c.388A>G (p.Asn130Asp) SNP with both enhanced and reduced transport activity of OATP1B1. In vivo in humans, the c.521C allele (present in SLCO1B1*5 and *15 haplotypes) is associated with decreased hepatic uptake and increased plasma concentrations of several OATP1B1 substrates. The SLCO1B1*1B (c.388G-c.521T) haplotype is associated with enhanced hepatic uptake and decreased plasma concentrations of some OATP1B1 substrates. The SLCO1B1 c.521CC genotype has been associated with an about 60-190% increased, and the SLCO1B1*1B/*1B genotype with an about 30% decreased area under the plasma concentration-time curve of repaglinide. Moreover, SLCO1B1 polymorphism can affect the extent of interaction between OATP1B1 inhibitors and repaglinide. Accordingly, SLCO1B1 genotyping may help in choosing the optimal starting dose of repaglinide. In Chinese individuals, the SLCO1B1 c.521C allele has been associated with increased plasma concentrations of nateglinide, but the association could not be replicated in Caucasians. SLCO1B1 genotype has had no effect on the pharmacokinetics of rosiglitazone, pioglitazone or their metabolites. The hepatic uptake of metformin is mediated by organic cation transporters 1 and 3, and the liver is not important for the elimination or action of the dipeptidylpeptidase 4 inhibitors sitagliptin, vildagliptin and saxagliptin. Therefore, SLCO1B1 polymorphism unlikely affects the response to these antidiabetics. Possible effects of SLCO1B1 polymorphism on sulfonylureas remain to be investigated.

Effects of SLCO1B1 and ABCB1 genotypes on the pharmacokinetics of atorvastatin and 2-hydroxyatorvastatin in healthy Korean subjects

This study aimed to evaluate the effect of genetic polymorphisms of SLCO1B1 and ABCB1 on the pharmacokinetics of atorvastatin and its metabolites. 290 Koreans were genotyped for SLCO1B1, ABCB1 and CYP3A5, and 28 subjects were selected for the pharmacokinetic study. Each subject received a single oral dose of 20 mg atorvastatin and blood samples were collected up to 48 hr after dosing. The relationship between the genotypes and atorvastatin pharmacokinetics was examined. For SLCO1B1 genotypes, the mean area under the concentration-time curve from time 0 to infinity (AUC0-infinity) of atorvastatin was 148.2 ng x hr/ml for *15/*15 subjects (n = 3), which was significantly larger than for 1a/*15 and *1b/*15 (n = 8) (80.7 ng x hr/ml, p = 0.0121) and also larger than for *1a/*1a, *1a/*1b and *1b/*1b (n = 17) (66.3 ng x hr/ml, p = 0.0018). The mean AUC0-infinity of 2-hydroxyatorvastatin for *15/*15 was also larger than in *1a/*1a, *1a/*1b and *1b/*1b (p = 0.012). In lactone forms, no significant pharmacokinetic difference was found among the genotypes. For ABCB1 genotypes, the half-lives of atorvastatin, atorvastatin lactone, 2-hydroxyatorvastatin and 2-hydroxyatorvastatin lactone were significantly longer in c.2677TT-c.3435TT (n = 3) vs. c.2677GG-c.3435CC and c.2677GT-c.3435CT (n = 10), yielding p = 0.049, 0.007, 0.007 and 0.007, respectively. This study shows that the SLCO1B1*15 allele may be associated with the individual difference in the AUC0-infinity of atorvastatin whereas the ABCB1 TT-TT diplotype may affect the elimination half-life of the drug in the Korean population.

Rifampicin alters atorvastatin plasma concentration on the basis of SLCO1B1 521T>C polymorphism

Background Both atorvastatin and rifampicin are substrates of OATP1B1 (organic anion transporting polypeptide 1B1) encoded by SLCO1B1 gene. Rifampicin is a potent inhibitor of SLCO1B1 (IC50 1.5 umol/l) and SLCO1B1 521T>C functional genetic polymorphism alters the kinetics of atorvastatin in vivo. We hypothesize that rifampicin might influence atorvastatin kinetics in a SLCO1B1 polymorphism dependent manner. Methods Sixteen subjects with known SLCO1B1 genotypes (6 c.521TT, 6 c.521TC and 4 c.521CC) were divided into 2 groups (atorvastatin–placebo group, n = 8; atorvastatin–rifampicin group, n = 8) randomly. In this 2-phase crossover study, atorvastatin (40 mg single-oral dose) pharmacokinetics after co-administration of placebo and rifampicin (600 mg single-oral dose) were measured for up to 48 h by liquid chromatography–mass spectrometry (LC–MS). In the third phase, rifampicin (450 mg single-oral dose) pharmacokinetics was measured additionally. Results Rifampicin increased atorvastatin plasma concentration in accordance with SLCO1B1 521T>C genotype while the increasing percentage of AUC (0–48) among c.521TT, c.521TC and c.521CC individuals were 833 ± 245% vs 468 ± 233% vs 330 ± 223% ( P = 0.007). However, SLCO1B1 521T>C exerted no impact on rifampicin pharmacokinetics ( P > 0.05). Conclusions These results suggested that rifampicin elevated the plasma concentration of atorvastatin depending on SLCO1B1 genotype and rifampicin pharmacokinetics were not altered by SLCO1B1 genotype.

Polymorphism of the hepatic influx transporter organic anion transporting polypeptide 1B1 is associated with increased cholesterol synthesis rate

We investigated the influence of SLCO1B1 polymorphism on cholesterol synthesis and absorption during baseline, and as affected by statins. In a crossover study, 32 healthy volunteers with different SLCO1B1 genotypes ingested a single dose of fluvastatin, pravastatin, simvastatin, rosuvastatin, and atorvastatin. Plasma total cholesterol, and cholesterol synthesis and absorption markers were measured before statin administration and up to 12 h thereafter. The mean fasting baseline plasma desmosterol to cholesterol ratio was 40% higher in participants with the SLCO1B1 c.521CC variant genotype than in those with the c.521TT genotype (P=0.043). The genotype had no significant effect on cholesterol absorption markers. All statins decreased lathosterol and avenasterol to cholesterol ratios, but no significant differences in the response existed between SLCO1B1 genotypes. In conclusion, the low activity SLCO1B1 c.521CC genotype is associated with an increased cholesterol synthesis rate. The short-term effects of statins on cholesterol homeostasis were not associated with the SLCO1B1 polymorphism.

Pharmacokinetic interaction between pravastatin and olmesartan in relation to SLCO1B1 polymorphism

The impact of SLCO1B1 polymorphism on the pharmacokinetics of olmesartan and on the pharmacokinetic interaction between pravastatin and olmesartan was investigated. On day 1, ten healthy volunteers took an oral dose (10 mg) of pravastatin. After a 3-day washout period, each subject received olmesartan medoxomil (10 mg) for 3 days. On day 8, they received olmesartan medoxomil (10 mg) and pravastatin (10 mg) concurrently, and pharmacokinetic profiles were compared with those in each single-dose phase with regard to the SLCO1B1 genotypes (*1b/*1b, *1b/*15, and *15/*15). In the single-dose phase, the mean C (max) and AUC(0-24) of olmesartan tended to be higher in *15/*15 subjects than in *1b/*1b subjects, while the mean CL( t )/F (+/-SD) in *15/*15 subjects was significantly lower than that in *1b/*1b subjects. No statistically significant differences were observed in any pharmacokinetic parameters between single-dose and co-administration phases for both pravastatin and RMS-416. These results suggest that OATP1B1 plays a role in the pharmacokinetics of olmesartan, and the co-administration of olmesartan does not affect the pharmacokinetics of pravastatin or its metabolite, RMS-416, although larger scale clinical studies are needed to confirm these observations due to the small sample size in the present study.

The effect of SLCO1B1*15 on the disposition of pravastatin and pitavastatin is substrate dependent: the contribution of transporting activity changes by SLCO1B1*15

This study was addressed to understand the underlying mechanism of the substrate-dependent effect of genetic variation in SLCO1B1, which encodes OATP1B1 (organic anion transporting polypeptide) transporter, on the disposition of two OATP1B1 substrates, pravastatin and pitavastatin, in relation to their transport activities. The uptake of pravastatin, pitavastatin, and fluvastatin was measured in oocytes overexpressing SLCO1B1*1a and SLCO1B1*15 to compare the alterations of in-vitro transporting activity. After 40-mg pravastatin or 4-mg pitavastatin was administered to 11 healthy volunteers with homozygous genotypes of SLCO1B1*1a/*1a and SLCO1B1*15/*15, the pharmacokinetic parameters of pravastatin and pitavastatin were compared among participants with SLCO1B1*1a/*1a and SLCO1B1*15/*15 genotypes. The uptake of pravastatin and pitavastatin in SLCO1B1*15 overexpressing oocytes was decreased compared with that in SLCO1B1*15, but no change occurred with fluvastatin. The fold change of in-vitro intrinsic clearance (Clint) for pitavastatin in SLCO1B1*15 compared with SLCO1B1*1a was larger than that of pravastatin (P<0.0001). The clearance (Cl/F) of pitavastatin was decreased to a greater degree in participant with SLCO1B1*15/*15 compared with that of pravastatin in vivo (P<0.01), consistent with in-vitro study. As a result, Cmax and area under the plasma concentration-time curve of these nonmetabolized substrates were increased by SLCO1B1*15 variant. The greater decrease in the transport activity for pitavastatin in SLCO1B1*15 variant compared with SLCO1B1*1a was, however, associated with the greater effect on the pharmacokinetics of pitavastatin compared with pravastatin in relation to the SLCO1B1 genetic polymorphism. This study suggests that substrate dependency in the consequences of the SLCO1B1*15 variant could modulate the effect of SLCO1B1 polymorphism on the disposition of pitavastatin and pravastatin.

Effects of Gemfibrozil and Atorvastatin on the Pharmacokinetics of Repaglinide in Relation to SLCO1B1 Polymorphism

In a randomized crossover study, 24 SLCO181-genotyped healthy volunteers were given daily doses of 1,200 mg gemfibrozil, 40 mg atorvastatin, or placebo, followed by 0.25 mg of repaglinide on day 3. The mean increase in the repaglinide area under the plasma concentration-time curve from 0 h to infinity (AUC(0-infinity)) produced by gemfibrozil was larger in individuals with the SLCO1B1 c.521CC genotype (n = 6) than in those with the c.521TC (n = 6) and c.521TT (n = 12) genotypes, by factors of 1.56 (P = 0.004) and 1.54 (P = 0.002), respectively. Gemfibrozil prolonged the repaglinide elimination half-life 1.43 times more in the c.521 CC group than in the c.521TT group (P = 0.047), but no differences were seen in the effects on peak plasma concentration (C(max)). While on gemfibrozil, the minimum blood glucose concentration after repaglinide intake was 19% lower in the c.521CC participants than in the c.521TT participants (P = 0.009). In the c.521TT group, atorvastatin intake had the effect of increasing repaglinide Cmax and AUC(0-infinity) by41% (P = 0.001) and 18% (P = 0.033), respectively. In conclusion, the extent of gemfibrozil-repaglinide interaction depends on SLCO1B1 genotype. Atorvastatin raises plasma repaglinide concentrations, probably by inhibiting organic anion transporting polypeptide 1B1 (OATP1B1).

Different Effects of SLCO1B1 Polymorphism on the Pharmacokinetics and Pharmacodynamics of Repaglinide and Nateglinide

Thirty-two healthy volunteers with different SLCO1B1 genotypes ingested a 0.5-mg dose of repaglinide and 60-mg dose of nateglinide with a washout period of 1 week. Participants with SLCO1B1 c.521CC genotype (n = 4) had a 59% (P = 0.001) or 72% (P < 0.001) greater mean area under the plasma repaglinide concentration-time curve (AUC(0-infinity)) than participants with c.521TC (n = 12) or c.521TT (n = 16) genotypes. The AUC(0-infinity) of repaglinide metabolites M2 and M4 were 112% (P = 0.004) and 81% (P = 0.002) larger in participants with c.521CC genotype than in those with c.521TT genotype, but no differences existed in the pharmacokinetics of M1. Maximum decrease in blood glucose concentration correlated with repaglinide AUC(0-infinity) (r = 0.412, P = 0.019). SLCO1B1 polymorphism had no significant effect on the pharmacokinetics or pharmacodynamics of nateglinide or its M7 metabolite. Thus, in contrast to repaglinide, the disposition of nateglinide is unaffected by the SLCO1B1 c.521T>C polymorphism.

OATP1B1 POLYMORPHISM IS A MAJOR DETERMINANT OF SERUM BILIRUBIN LEVEL BUT NOT ASSOCIATED WITH RIFAMPICIN‐MEDIATED BILIRUBIN ELEVATION

1. Elevated serum bilirubin levels are caused mainly by liver diseases, haematolysis, genetic defects and drug intake. Unconjugated bilirubin (UCB) is taken up into hepatocytes by human organic anion transporting polypeptide 1B1 (OATP1B1; encoded for by the SLCO1B1 gene). The present study was performed to determine the association between SLCO1B1 gene polymorphisms and serum bilirubin levels in vivo. Moreover, the effects of administration of low-dose rifampicin on serum bilirubin levels in different SLCO1B1 genotypes was examined. 2. Serum bilirubin levels were examined in 42 healthy volunteers who had been analysed for SLCO1B1 genotype (seven, 13, 14 and eight with SLCO1B1 genotypes *1a/*1a, *1b/*1b, *1b/*15 and *15/*15, respectively). Among them, 24 subjects (seven, seven, eight and two with SLCO1B1 genotypes *1a/*1a, *1b/*1b, *1b/*15 and *15/*15, respectively) were selected to participate in an open-label, two-phase clinical trial. Each was given 450 mg rifampicin orally once daily at 2000 hours for 5 consecutive days. Serum bilirubin concentrations at 0800 hours on the 1st and 6th days were compared between the different SLCO1B1 genotypes. 3. In the 42 volunteers, the mean (+/-SD) serum UCB in both SLCO1B1*1b/*15 and *15/*15 groups was significantly higher than that in the SLCO1B1*1b/*1b group (11.07 +/- 2.31, 13.01 +/- 3.87 and 8.21 +/- 2.68 micromol/L, respectively; P = 0.009 and P < 0.001). Total bilirum (T.BIL) in both the SLCO1B1*1b/*15 and *15/*15 groups was significantly higher than that in the SLCO1B1*1b/*1b group (16.69 +/- 4.09, 20.71 +/- 5.12 and 13.06 +/- 5.12 micromol/L, respectively; P = 0.029 and P < 0.001). The direct bilirubin (D.BIL) in the SLCO1B1*15/*15 group was significantly higher than that in the SLCO1B1*1b/*1b group (7.69 +/- 1.81 vs 4.85 +/- 1.81 micromol/L, respectively; P = 0.001). Rifampicin significantly increased UCB, T.BIL and D.BIL concentrations in 24 healthy volunteers (17.68 +/- 5.96 vs 13.95 +/- 4.44 micromol/L (P = 0.040), 5.72 +/- 2.01 vs 4.35 +/- 1.50 micromol/L (P = 0.028) and 12.00 +/- 4.26 vs 9.61 +/- 3.15 micromol/L (P = 0.035), respectively). However, the extent of the increase in serum bilirubin caused by 450 mg rifampicin for 5 days was not affected by SLCO1B1 genotype. 4. Genetic polymorphism in SLCO1B1 is a major determinant of interindividual variability in the serum bilirubin level. SLCO1B1*15 carriers had higher baseline serum UCB, T.BIL and D.BIL levels compared with subjects with the SLCO1B1*1a/*1a and SLCO1B1*1b/*1b genotypes. SLCO1B1*15/*15 homozygotes are more susceptible to hyperbilirubinaemia. Serum bilirubin levels could be increased by low-dose rifampicin administration, but the extent of the increase was not associated with SLCO1B1 genotype.

Effect of drug transporter genotypes on pravastatin disposition in European- and African-American participants

Our aims were to evaluate the effects of polymorphisms in the hepatic drug uptake transporter organic anion transporting polypeptide 1B1 (OATP1B1, SLCO1B1) and efflux transporters multidrug resistance-associated protein 2 (MRP2, ABCC2), bile salt export pump (BSEP, ABCB11), and breast cancer-related protein (BCRP, ABCG2) on single-dose pravastatin pharmacokinetics in healthy European- and African-American participants. The pharmacokinetics of a single oral 40 mg dose of pravastatin was determined in 107 participants (69 European-Americans and 38 African-Americans). Participants were genotyped for known OATP1B1, MRP2, BSEP, and BCRP polymorphisms. Baseline serum total and unconjugated plasma bilirubin concentrations were also determined. OATP1B1 genotypes were ethnicity-dependent with a 521C allele frequency of approximately 15% in European-Americans and approximately 1% in African-Americans. SLCO1B1 521TC genotype was associated with significantly higher pravastatin area under the curve [AUC(0-5)] (P=0.01) and Cmax values (P<0.05). When analyzed by diplotype, SLCO1B1*1a/*15 (N=8) participants exhibited 45 and 80% higher AUC values than SLCO1B1*1a/*1a (N=29) (P=0.013) and SLCO1B1*1b/*1b (N=34) (P=0.001) carriers, respectively. SLCO1B1*15/*15 (N=2) participants exhibited 92 and 149% higher AUC values than SLCO1B1*1a/*1a (P=0.017) and SLCO1B1*1b/*1b (P=0.011) carriers, respectively. European-Americans had significantly higher plasma pravastatin AUC(0-5) (P=0.01) and Cmax values (P=0.009) than African-Americans. Neither ABCC2, ABCB11, nor ABCG2 genotypes were associated with differences in pravastatin pharmacokinetics. We did not observe an effect of SLCO1B1 genotype on baseline total or unconjugated bilirubin levels. SLCO1B1 genotype, in particular the 521C allele, had a significant effect on the pharmacokinetics of pravastatin. Even when adjusted for the presence of the SLCO1B1 521C or 388G variant allele, European-Americans demonstrated significantly higher pravastatin AUC and Cmax values than African-Americans.

Different Effects of SLCO1B1 Polymorphism on the Pharmacokinetics of Atorvastatin and Rosuvastatin

Thirty-two healthy volunteers with different SLCO1B1 genotypes ingested a 20 mg dose of atorvastatin and 10 mg dose of rosuvastatin with a washout period of 1 week. Subjects with the SLCO1B1 c.521CC genotype (n=4) had a 144% (P<0.001) or 61% (P=0.049) greater mean area under the plasma atorvastatin concentration-time curve from 0 to 48 h (AUC(0-48 h)) than those with the c.521TT (n=16) or c.521TC (n=12) genotype, respectively. The AUC(0-48 h) of 2-hydroxyatorvastatin was 100% greater in subjects with the c.521CC genotype than in those with the c.521TT genotype (P=0.018). Rosuvastatin AUC(0-48 h) and peak plasma concentration (Cmax) were 65% (P=0.002) and 79% (P=0.003) higher in subjects with the c.521CC genotype than in those with the c.521TT genotype. These results indicate that, unexpectedly, SLCO1B1 polymorphism has a larger effect on the AUC of atorvastatin than on the more hydrophilic rosuvastatin.

SLCO1B1 polymorphism markedly affects the pharmacokinetics of simvastatin acid

Organic anion transporting polypeptide 1B1 (OATP1B1) is an uptake transporter located at the sinusoidal membrane of human hepatocytes. This study aimed to investigate the effects of genetic polymorphism in the SLCO1B1 gene encoding OATP1B1 on the pharmacokinetics of simvastatin. Four healthy volunteers with the homozygous SLCO1B1 c.521CC genotype, 12 with the heterozygous c.521TC genotype and 16 with the homozygous c.521TT genotype (controls) were recruited. Each study participant ingested a single 40-mg dose of simvastatin. Plasma concentrations of simvastatin (inactive lactone) and its active metabolite simvastatin acid were measured for 12 h. The AUC0-infinity of simvastatin acid was 120 and 221% higher in participants with the SLCO1B1 c.521CC genotype than in those with the c.521TC and c.521TT (reference) genotypes, respectively (P<0.001). The Cmax of simvastatin acid was 162 and 200% higher in participants with the c.521CC genotype than in those with the c.521TC and c.521TT genotypes (P<0.001). The Cmax of simvastatin acid occurred earlier in participants with the c.521CC and c.521TC genotypes than in those with the c.521TT genotype (P<0.05). No association existed between the SLCO1B1 genotype and the elimination half-life of simvastatin acid. Moreover, no statistically significant association was seen between the SLCO1B1 genotype and the pharmacokinetics of simvastatin lactone. SLCO1B1 polymorphism markedly affects the pharmacokinetics of active simvastatin acid, but has no significant effect on parent simvastatin. Raised plasma concentrations of simvastatin acid in patients carrying the SLCO1B1 c.521C variant allele may enhance the risk of systemic adverse effects during simvastatin treatment. In addition, reduced uptake of simvastatin acid by OATP1B1 into the liver in patients with the c.521C allele could reduce its cholesterol-lowering efficacy.

SLCO1B1 polymorphism and sex affect the pharmacokinetics of pravastatin but not fluvastatin

Pravastatin is a hydrophilic substrate and fluvastatin a lipophilic substrate of the hepatic uptake transporter organic anion transporting polypeptide 1B1 encoded by SLCO1B1. Our aim was to compare the effects of SLCO1B1 polymorphism on the pharmacokinetics of pravastatin and fluvastatin. We recruited 4 healthy volunteers (3 men and 1 woman) with the homozygous SLCO1B1 c.521CC genotype, 12 (7 men and 5 women) with the heterozygous c.521TC genotype, and 16 (8 men and 8 women) with the homozygous c.521TT genotype (control subjects). In a crossover study each subject ingested a single 40-mg dose of fluvastatin and pravastatin with a washout period of at least 1 week. Plasma fluvastatin and pravastatin concentrations were measured for 12 hours. In men with the c.521CC genotype, the mean peak concentration in plasma and area under the plasma concentration-time curve from time 0 to infinity of pravastatin were 274% (95% confidence interval [CI], 92%-456%; P = .001) and 232% (95% CI, 74%-391%; P = .002) greater than those in men with the c.521TT genotype and 120% (95% CI, 11%-230%; P = .026) and 102% (95% CI, 3%-200%; P = .040) greater than those in men with the c.521TC genotype. In addition, women with the c.521TT genotype had a 147% (95% CI, 12%-281%; P = .028) greater peak concentration in plasma and a 142% (95% CI, 7%-242%; P = .034) greater area under the plasma concentration-time curve from time 0 to infinity than men with the c.521TT genotype. The pharmacokinetic variables of pravastatin were approximately similar among women with different SLCO1B1 genotypes. No significant differences were seen in the pharmacokinetics of fluvastatin between subjects with different SLCO1B1 genotypes or between the sexes. SLCO1B1 polymorphism has a large effect on the pharmacokinetics of pravastatin but not fluvastatin. This suggests that the lipophilic fluvastatin can penetrate the hepatocyte plasma membrane via passive diffusion or that uptake transporters other than organic anion transporting polypeptide 1B1 mainly mediate its hepatic uptake. Moreover, the results suggest that sex may affect the pharmacokinetics of pravastatin and possibly the functional consequences of SLCO1B1 polymorphism.

Effect of SLCO1B1 genetic polymorphism on the pharmacokinetics of nateglinide

Nateglinide is a meglitinide analogue with antidiabetic action. A recent study showed that SLCO1B1 (which codes the OATP1B1 gene, also known as OATP-C, OATP2) is a major determinant which markedly affects the pharmacokinetics of repaglinide. Our objective was to assess the association between single nucleotide polymorphisms (SNPs) of SLCO1B1 and the pharmacokinetics of nateglinide. Seventeen healthy volunteers with different SLCO1B1 genotypes (11 with 521TT, four with 521TC and two with 521CC) were enrolled in this study. Each was given a single oral dose of 90 mg nateglinide. Plasma concentrations of nateglinide were measured up to 8 h by HPLC. The C(max) and AUC(0,infinity) of nateglinide were 83% (P = 0.002) and 82% (P = 0.001) higher in the SLCO1B1521TC subjects (n = 4), and 76% (P = 0.016) and 108% (P = 0.001) higher in the SLCO1B1521CC subjects (n = 2) than in the SLCO1B1521TT subjects (n = 11), respectively. The t(1/2) of nateglinide in SLCO1B1521CC subjects was 78% longer than that in 521TT subjects (P = 0.036). The difference in t(max) values among the three genotypic groups was not statistically significant. Our results suggest that OATP1B1-mediated hepatic uptake of nateglinide may be the prior step for its metabolism and elimination. SLCO1B1521T > C SNP might play an important role in the pharmacokinetics of nateglinide.

Organic anion transporting polypeptide 1B1 activity classified by SLCO1B1 genotype influences atrasentan pharmacokinetics

Our objective was to learn whether genetic polymorphisms of metabolic enzymes or transport proteins provide a mechanistic understanding of the in vivo disposition of atrasentan, a selective endothelin A receptor antagonist. Atrasentan uptake was measured in HeLa cells transfected to express major alleles of organic anion transporting polypeptide 1B1 (OATP1B1). The results were used to classify individuals as extensive, intermediate, or poor OATP1B1 transporters according to their SLCO1B1 genotypes. Analysis of covariance including genotype, study, age, weight, sex, and ethnicity was used to identify factors influencing atrasentan single-dose (n = 44) and steady-state (n = 38) pharmacokinetic parameters. Genotypes for cytochrome P450 3A5, uridine diphosphate-glucuronosyltransferase (UGT) 1A1, UGT2B4, UGT2B15, adenosine triphosphate-binding cassette subfamily B (ABCB) 1, solute carrier organic anion transporter (SLCO) 1B1, and solute carrier family 22 (SLC22) A2 were each assessed. Single-dose atrasentan exposure (P = .0244), steady-state atrasentan exposure (P = .0108), and maximum postdose plasma concentration (P = .0002) were associated with OATP1B1 activity classified by SLCO1B1 genotype. No other tested genotypes were observed to be associated with both single-dose and steady-state atrasentan pharmacokinetics. OATP1B1 is a meaningful factor for atrasentan disposition. Individuals may be classified as having extensive, intermediate, or poor OATP1B1 transport phenotypes according to SLCO1B1 genotypes. Increased exposures of OATP1B1 substrates might be expected in individuals who have the poor transporter phenotype or are treated with an OATP1B1 inhibitor.

Rosuvastatin pharmacokinetics and pharmacogenetics in white and Asian subjects residing in the same environment

Systemic exposure to rosuvastatin had been observed to be approximately 2-fold higher in Japanese subjects living in Japan compared with white subjects in Western Europe or the United States. The organic anion transporting polypeptide 1B1 contributes to the hepatic uptake of rosuvastatin. Polymorphisms in the SLCO1B1 gene can lead to reduced transport function in vitro (T 521>C). This study was conducted to determine whether the pharmacokinetic differences between Japanese and white subjects extended to other Asian ethnic groups and to determine whether polymorphisms in the SLCO1B1 gene contribute to any pharmacokinetic differences observed. Rosuvastatin pharmacokinetics was studied in an open-label, parallel-group, single-oral dose (40 mg) study in 36 white, 36 Chinese, 35 Malay, and 35 Asian-Indian subjects living in Singapore, Singapore. Plasma concentrations of rosuvastatin and metabolites were determined by HPLC-mass spectrophotometry. Two SLCO1B1 polymorphisms (A 388>G and T 521>C) were genotyped. Ratios for rosuvastatin area under the plasma concentration-time curve from time 0 to the time of the last quantifiable concentration were 2.31, 1.91, and 1.63 and ratios for maximum plasma concentration were 2.36, 2.00, and 1.68 in Chinese, Malay, and Asian-Indian subjects, respectively, compared with white subjects. Similar increases in exposure to N-desmethyl rosuvastatin and rosuvastatin-lactone were observed. SLCO1B1 genotypes did not account for the observed pharmacokinetic differences between Asians and white subjects. Plasma exposure to rosuvastatin and its metabolites was significantly higher in Chinese, Malay, and Asian-Indian subjects compared with white subjects living in the same environment.

Irinotecan (CPT-11) pharmacokinetics (PK) and neutropenia: interaction among UGT1A1 and transporter genes

2006 Background: We have previously shown that UGT1A1 and ABCC2 gene polymorphisms are likely to play an important role in CPT-11 PK variability. Among several variants tested, -3156G>A in UGT1A1 and 3972C>T in ABCC2 showed the strongest phenotypic effect. However, several other ABCC2 variants have been shown to affect ABCC2 expression in vitro. The organic anion transporter polypeptide-1B1 (OATP-1B1, SLCO1B1) is involved in the liver uptake of several compounds. This study aims to evaluate the effects of ABCC2 haplotypes and SLCO1B1 genotypes on CPT-11 PK and neutropenia. Methods: We studied 65 pts previously assessed for PK and toxicity (JCO, 2004). Six SNPs in ABCC2 were genotyped [-1549G>A, -1019A>G, -24C>T, 1249G>A, intron 27 -34C>T, 3972C>T] and haplotypes were estimated. Two SNPs in SLCO1B1 [*1b (388A>G) and *5 (521T>C)] were also genotyped. Results: Twelve ABCC2 haplotypes were identified, with haplotypes 2, 3, 4, 7, and 6 having a frequency of 0.33, 0.22, 0.14, 0.12, and 0.05, respectively. Haplotype 4 was correlated with SN-38G/SN-38 AUC ratios (p<0.0001). SLCO1B1*5 genotype was correlated with SN-38G AUC (p=0.001) and CPT-11 AUC (p<0.0001). Pts with SLCO1B1*5 CT+CC genotype had a higher CPT-11 AUC compared to TT genotype (29.5±8.8 vs. 22.3±5.1 μg*h/ml, p=0.0001). SLCO1B1*1b was associated with an increased ln(ANC nadir), although with borderline significance (p=0.07). The best multivariate model for ln(ANC nadir) included UGT1A1 -3156G>A (p=0.03), SLCO1B1*1b (p=0.03), ABCC2 haplotype 4 (p=0.02), total bilirubin (p<0.0001), and gender (p=0.04) (r2=0.49, p<0.0001). Conclusions: SLCO1B1*5 appears to affect CPT-11 clearance. SLCO1B1, ABCC2 and UGT1A1 gene variants may have additive effects on neutropenia. Additional studies of the relationship of common ABCC2 and SLCO1B1 variants to CPT-11 PK and toxicity are warranted. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration FDA

Fexofenadine pharmacokinetics are associated with a polymorphism of the SLCO1B1 gene (encoding OATP1B1)

Fexofenadine pharmacokinetics are associated with a polymorphism of the <i>SLCO1B1</i> gene (encoding OATP1B1)