A novel human hepatic organic anion transporting polypeptide (OATP2). Identification of a liver-specific human organic anion transporting polypeptide and identification of rat and human hydroxymethylglutaryl-CoA reductase inhibitor transporters

Identification of Genetic Variants Associated with Pravastatin and Pitavastatin Pharmacokinetics

A clinical trial was carried out to investigate the pharmacogenetics of single-dose pravastatin and pitavastatin pharmacokinetics in 173 and 164 healthy participants. Additionally, 96 participants were included from previous pharmacogenetic studies with pravastatin. In a genome-wide meta-analysis of pravastatin including all 269 participants, SLCO1B1 c.521T>C (rs4149056) was associated with increased AUC0-∞ (P = 9.8 × 10-12). Similarly, SLCO1B1 c.521T>C was genome-wide significantly associated with increased AUC0-∞ of pitavastatin (P = 9.7 × 10-15). Candidate gene analyses suggested that participants with increased function SLCO1B1 variants had decreased pravastatin exposure. Furthermore, decreased function CYP2C9 variants may increase pitavastatin and pitavastatin lactone exposure. Compared to participants with normal function SLCO1B1 genotype, the AUC0-∞ of pravastatin was 140% (90% confidence interval: 86-210%; P = 4.7 × 10-8) and 37% (20-56%; P = 1.1 × 10-4) greater in participants with poor and decreased function SLCO1B1 genotype, respectively, while participants with highly increased function SLCO1B1 genotype had a 60% (39-75%; P = 6.0 × 10-4) lower AUC0-∞. The AUC0-∞ of pitavastatin was 153% (100-222%; P = 1.6 × 10-9) and 35% (8-69%; P = 0.027) greater in participants with poor and decreased function SLCO1B1 genotype, respectively, than in those with normal function SLCO1B1 genotype. Participants with intermediate metabolizer CYP2C9 genotype had 18% (3-34%; P = 0.046) greater AUC0-∞ of pitavastatin than those with normal metabolizer CYP2C9 genotype. This study demonstrates the important role of SLCO1B1 in pravastatin and pitavastatin pharmacokinetics and suggests that CYP2C9 variants also affect the pharmacokinetics of pitavastatin.

Organic anion transporting polypeptides: Pharmacology, toxicology, structure, and transport mechanisms

Organic anion transporting polypeptides (OATPs) are membrane proteins that mediate the uptake of a wide range of substrates across the plasma membrane of various cells and tissues. They are classified into 6 subfamilies, OATP1 through OATP6. Humans contain 12 OATPs encoded by 11 solute carrier of organic anion transporting polypeptide (SLCO) genes: OATP1A2, OATP1B1, OATP1B3, the splice variant OATP1B3-1B7, OATP1C1, OATP2A1, OATP2B1, OATP3A1, OATP4A1, OATP4C1, OATP5A1, and OATP6A1. Most of these proteins are expressed in epithelial cells, where they mediate the uptake of structurally unrelated organic anions, cations, and even neutral compounds into the cytoplasm. The best-characterized members are OATP1B1 and OATP1B3, which have an important role in drug metabolism by mediating drug uptake into the liver and are involved in drug-drug interactions. In this review, we aimed to (1) provide a historical perspective on the identification of OATPs and their nomenclature and discuss their phylogenic relationships and molecular characteristics; (2) review the current knowledge of the broad substrate specificity and their role in drug disposition and drug-drug interactions, with a special emphasis on human hepatic OATPs; (3) summarize the different experimental systems that are used to study the function of OATPs and discuss their advantages and disadvantages; (4) review the available experimental 3-dimensional structures and examine how they can help elucidate the transport mechanisms of OATPs; and (5) finally, summarize the current knowledge of the regulation of OATP expression, discuss clinically important single-nucleotide polymorphisms, and outline challenges of physiologically based pharmacokinetic modeling and in vitro to in vivo extrapolation. SIGNIFICANCE STATEMENT: Organic anion transporting polypeptides (OATPs) are a family of 12 uptake transporters in the solute carrier superfamily. Several members, particularly the liver-expressed OATP1B1 and OATP1B3, are important drug transporters. They mediate the uptake of several endobiotics and xenobiotics, including statins and numerous other drugs, into hepatocytes, and their inhibition by other drugs or reduced expression due to single-nucleotide polymorphisms can lead to adverse drug effects. Their recently solved 3-dimensional structures should help to elucidate their transport mechanisms and broad substrate specificities.

Personalized statin therapy: Targeting metabolic processes to modulate the therapeutic and adverse effects of statins

Statins are widely used for treating lipid disorders and cardiovascular diseases. However, the therapeutic efficiency and adverse effects of statins vary among different patients, which numerous clinical and epidemiological studies have attributed to genetic polymorphisms in statin-metabolizing enzymes and transport proteins. The metabolic processes of statins are relatively complex, involving spontaneous or enzyme-catalyzed interconversion between more toxic lactone metabolites and active acid forms in the liver and bloodstream, influenced by multiple factors, including the expression levels of many metabolic enzymes and transporters. Addressing the variable statin therapeutic outcomes is a pressing clinical challenge. Transcription factors and epigenetic modifications regulate the metabolic enzymes and transporters involved in statin metabolism and disposition and, therefore, hold promise as 'personalized' targets for achieving optimized statin therapy. In this review, we explore the potential for customizing therapy by targeting the metabolism of statin medications. The biochemical bases of adverse reactions to statin drugs and their correlation with polymorphisms in metabolic enzymes and transporters are summarized. Next, we mainly focus on the regulatory roles of transcription factors and epigenetic modifications in regulating the gene expression of statin biochemical machinery. The recommendations for future therapies are finally proposed by targeting the central regulatory factors of statin metabolism.

Exploring flavonoids as potent SLC46A3 inhibitors: Insights from the structural characteristics of flavonoid-SLC46A3 interactions

SLC46A3, a transporter for lysosomal steroid conjugates and bile acids, plays a pivotal role in the pharmacological effects of noncleavable antibody-drug conjugates using maytansine as a payload. SLC46A3 may exert negative effects on various phenomena, including copper homeostasis, mitochondrial function in the liver, and the uptake of lipid-based nanoparticles (NPs) in tumor cells. Consequently, inhibiting SLC46A3 may be a promising strategy for treating hepatic disease or enhancing lipid NP delivery to tumor cells, although the underlying mechanisms remain unknown. This study investigates flavonoids, the largest subgroup of polyphenols characterized by a simple C6-C3-C6 structure, as potential SLC46A3 inhibitors and provides insights into the structural requirements for flavonoid-SLC46A3 interactions. Screening revealed several flavonoids, including dihydrochalcones, flavonols, isoflavones, flavanones, and flavones, as effective inhibitors of 5-carboxyfluorescein (5-CF) uptake in MDCKII (Mardin-Darby canine kidney type II) cells stably expressing a mutant SLC46A3 localized to the plasma membrane. Notably, apigenin and luteolin exhibited marked 5-CF uptake inhibition, with IC50 values of 10.8 and 8.7 µM, respectively. Additionally, 4',7-dihydroxyflavone significantly inhibited 5-CF uptake, exhibiting an IC50 value of 9.3 µM, whereas acacetin and genkwanin possessing methoxy group substitutions for the hydroxy group at the 4'- or 7-position of apigenin, respectively, did not affect the uptake. Luteolin's inhibition mechanism was found to be of a mixed type involving increased Km and decreased Vmax. These findings emphasize the importance of hydroxy groups at 4'- and 7-positions in flavone-SLC46A3 interactions.

SLCO1B1 Genetic Variation Influence on Atorvastatin Systemic Exposure in Pediatric Hypercholesterolemia

This clinical study examined the influence of SLCO1B1 c.521T>C (rs4149056) on plasma atorvastatin concentrations in pediatric hypercholesterolemia. The participants (8-21 years), including heterozygous (c.521T/C, n = 13), homozygous (c.521C/C, n = 2) and controls (c.521T/T, n = 13), completed a single-oral-dose pharmacokinetic study. Similar to in adults, the atorvastatin (AVA) area-under-concentration-time curve from 0 to 24 h (AUC0-24) was 1.7-fold and 2.8-fold higher in participants with c.521T/C and c.521C/C compared to the c.521T/T participants, respectively. The inter-individual variability in AVA exposure within these genotype groups ranged from 2.3 to 4.8-fold, indicating that additional factors contribute to the inter-individual variability in the AVA dose-exposure relationship. A multivariate model reinforced the SLCO1B1 c.521T>C variant as the central factor contributing to AVA systemic exposure in this pediatric cohort, accounting for ~65% of the variability in AVA AUC0-24. Furthermore, lower AVA lactone concentrations in participants with increased body mass index contributed to higher exposure within the c.521T/T and c.521T/C genotype groups. Collectively, these factors contributing to higher systemic exposure could increase the risk of toxicity and should be accounted for when individualizing the dosing of atorvastatin in eligible pediatric patients.

The Effect of Original Russian Neurotropic Drugs on Organic Anion Transporting Polypeptides OATP1B1 and OATP1B3

In experiments on HepG2 cells, we studied the effect of the original domestic neurotropic drugs omberacetam, fabomotizole, and ethylmethylhydroxypyridine succinate (EMHPS) (1-500 μM) on the activity and content of organic anion transporting polypeptides OATP1B1 and OATP1B3. It was shown that omberacetam (500 μM) increased the content of OATP1B1 and OATP1B3, fabomotizole did not affect the level of both transporters, and EMHPS (500 μM) increased the content of OATP1B1 compared to the control and did not affect the level of OATP1B3. The tested substances also reduced the OATP1B1/OATP1B3 ratio, as evidenced by a decrease in the penetration of atorvastatin, a substrate of the transporters, into HepG2 cells in the presence of omberacetam (100-500 μM), fabomotizole (500 μM), and EMHPS (10-500 μM). Evaluation of clinical significance of the obtained results, according to the FDA approach based on the calculation of the Cmax/IC50 ratio, showed that the effect of the tested substances on OATP1B1/OATP1B3 is clinically insignificant.

The Role of Adopted Orphan Nuclear Receptors in the Regulation of an Organic Anion Transporting Polypeptide 1B1 (OATP1B1) under the Action of Sex Hormones

Organic anion transporting polypeptide 1B1 (OATP1B1) is an influx transporter protein of the SLC superfamily, expressed mainly in the liver and some tumor cells. The mechanisms of its regulation are being actively studied. In the present study, the effect of sex hormones (estradiol, progesterone and testosterone) on OATP1B1 expression in HepG2 cells was examined. The role of adopted orphan receptors, farnasoid X receptor (FXR), constitutive androstane receptor (CAR), pregnane X receptor (PXR) and liver X receptor subtype alpha (LXRa), was also evaluated. Hormones were used in concentrations of 1, 10 and 100 μM, with incubation for 24 h. The protein expression of OATP1B1, FXR, CAR, PXR and LXRa was analyzed by Western blot. It was shown that estradiol (10 and 100 μM) increased the expression of OATP1B1, acting through CAR. Testosterone (1, 10 and 100 μM) increased the expression of OATP1B1, acting through FXR, PXR and LXRa. Progesterone (10 and 100 μM) decreased the expression of OATP1B1 (10 and 100 μM) and adopted orphan receptors are not involved in this process. The obtained results have important practical significance and determine ways for targeted regulation of the transporter, in particular in cancer.

Generation of a Cell Line Selectively Producing Functionally Active OATP1B1 Transporter

The solute carrier organic anion transporter family member, OATP1B1, is one of the most important transporter proteins, which mediate penetration of many endogenous substances and xenobiotics into hepatocytes. A model system providing expression of the functional protein is needed to assess interaction of OATP1B1 with various substances. Based on the HEK293 cells, we obtained the HEK293-OATP1B1 cell line, constitutively expressing the SLCO1B1 gene encoding the OATP1B1 transporter. Expression of the SLCO1B1 gene was confirmed by real-time PCR analysis and Western blotting. Functionality of the transporter was assessed by the transport of atorvastatin, which is a substrate of OATP1B1. Cells of the resulting cell line, which selectively express the functionally active recombinant OATP1B1 transporter, can be used to study functions of the protein and to test drugs for being substrates, inducers, and inhibitors of OATP1B1, and to assess the risks of drug interactions.

Role of the Sodium-Dependent Organic Anion Transporter (SOAT/SLC10A6) in Physiology and Pathophysiology

The sodium-dependent organic anion transporter (SOAT, gene symbol SLC10A6) specifically transports 3'- and 17'-monosulfated steroid hormones, such as estrone sulfate and dehydroepiandrosterone sulfate, into specific target cells. These biologically inactive sulfo-conjugated steroids occur in high concentrations in the blood circulation and serve as precursors for the intracrine formation of active estrogens and androgens that contribute to the overall regulation of steroids in many peripheral tissues. Although SOAT expression has been detected in several hormone-responsive peripheral tissues, its quantitative contribution to steroid sulfate uptake in different organs is still not completely clear. Given this fact, the present review provides a comprehensive overview of the current knowledge about the SOAT by summarizing all experimental findings obtained since its first cloning in 2004 and by processing SOAT/SLC10A6-related data from genome-wide protein and mRNA expression databases. In conclusion, despite a significantly increased understanding of the function and physiological significance of the SOAT over the past 20 years, further studies are needed to finally establish it as a potential drug target for endocrine-based therapy of steroid-responsive diseases such as hormone-dependent breast cancer.

PharmVar GeneFocus: SLCO1B1

The Pharmacogene Variation Consortium (PharmVar) is now providing star (*) allele nomenclature for the highly polymorphic human SLCO1B1 gene encoding the organic anion transporting polypeptide 1B1 (OATP1B1) drug transporter. Genetic variation within the SLCO1B1 gene locus impacts drug transport, which can lead to altered pharmacokinetic profiles of several commonly prescribed drugs. Variable OATP1B1 function is of particular importance regarding hepatic uptake of statins and the risk of statin-associated musculoskeletal symptoms. To introduce this important drug transporter gene into the PharmVar database and serve as a unified reference of haplotype variation moving forward, an international group of gene experts has performed an extensive review of all published SLCO1B1 star alleles. Previously published star alleles were self-assigned by authors and only loosely followed the star nomenclature system that was first developed for cytochrome P450 genes. This nomenclature system has been standardized by PharmVar and is now applied to other important pharmacogenes such as SLCO1B1. In addition, data from the 1000 Genomes Project and investigator-submitted data were utilized to confirm existing haplotypes, fill knowledge gaps, and/or define novel star alleles. The PharmVar-developed SLCO1B1 nomenclature has been incorporated by the Clinical Pharmacogenetics Implementation Consortium (CPIC) 2022 guideline on statin-associated musculoskeletal symptoms.

Predicting disruptions to drug pharmacokinetics and the risk of adverse drug reactions in non-alcoholic steatohepatitis patients

The liver plays a central role in the pharmacokinetics of drugs through drug metabolizing enzymes and transporters. Non-alcoholic steatohepatitis (NASH) causes disease-specific alterations to the absorption, distribution, metabolism, and excretion (ADME) processes, including a decrease in protein expression of basolateral uptake transporters, an increase in efflux transporters, and modifications to enzyme activity. This can result in increased drug exposure and adverse drug reactions (ADRs). Our goal was to predict drugs that pose increased risks for ADRs in NASH patients. Bibliographic research identified 71 drugs with reported ADRs in patients with liver disease, mainly non-alcoholic fatty liver disease (NAFLD), 54 of which are known substrates of transporters and/or metabolizing enzymes. Since NASH is the progressive form of NAFLD but is most frequently undiagnosed, we identified other drugs at risk based on NASH-specific alterations to ADME processes. Here, we present another list of 71 drugs at risk of pharmacokinetic disruption in NASH, based on their transport and/or metabolism processes. It encompasses drugs from various pharmacological classes for which ADRs may occur when used in NASH patients, especially when eliminated through multiple pathways altered by the disease. Therefore, these results may inform clinicians regarding the selection of drugs for use in NASH patients.

Insights into the Dermal Absorption, Deposition, and Elimination of Poly- and Perfluoroalkyl Substances in Rats: The Importance of Skin Exposure

Humans are frequently exposed to poly- and perfluoroalkyl substances (PFASs) via direct skin contact with personal care and consumer products containing them. Here, we used a rat model to estimate the dermal penetration efficiency of 15 representative PFASs. After 144 h post-dosing, 4.1-18.0 and 5.3-15.1% of the applied PFASs in the low (L) and high (H) groups, respectively, were absorbed into the rats. PFAS absorption and permeation were parabolically associated with the perfluorinated carbon chain length (C_F), peaking for perfluoroheptanoic acid (PFHpA). The lipid-rich stratum corneum of the skin barrier substantially suppressed the penetration of less hydrophobic short-chain PFASs, whereas the water-rich viable epidermis and dermis served as obstacles to hydrophobic long-chain PFAS permeation. However, the renal clearance (CL_renal) of the target PFAS decreased with increasing C_F, suggesting that urinary excretion is crucial to eliminate less hydrophobic short-chain PFASs. Notably, the peak times of PFASs in the systemic circulation of rats (8-72 h) were remarkably longer than those after oral administration (1-24 h). These results suggest that dermal penetration can be long-lasting and contribute considerably to the body burden of PFASs, especially for those with moderate hydrophobicity due to their favorable skin permeation and unfavorable urinary excretion.

Unmet Need for Further LDL-C Lowering in India despite Statin Therapy: Lipid Association of India Recommendations for the Use of Bempedoic Acid

Lipid-lowering therapy plays a crucial role in reducing adverse cardiovascular (CV) events in patients with established atherosclerotic cardiovascular disease (ASCVD) and familial hypercholesterolemia. Lifestyle interventions along with high-intensity statin therapy are the first-line management strategy followed by ezetimibe. Only about 20-30% of patients who are on maximally tolerated statins reach recommended low-density lipoprotein cholesterol (LDL-C) goals. Several factors contribute to the problem, including adherence issues, prescription of less than high-intensity statin therapy, and de-escalation of statin dosages, but in patients with very high baseline LDL-C levels, including those with familial hypercholesterolemia and those who are intolerant to statins, it is critical to expand our arsenal of LDL-C-lowering medications. Moreover, in the extreme risk group of patients with an LDL-C goal of ≤30 mg/dL according to the Lipid Association of India (LAI) risk stratification algorithm, there is a significant residual risk requiring the addition of non-statin drugs to achieve LAI recommended targets. This makes bempedoic acid a welcome addition to the existing non-statin therapies such as ezetimibe, bile acid sequestrants, and PCSK9 inhibitors. A low frequency of muscle-related side effects, minimal drug interactions, a significant reduction in high-sensitivity C-reactive protein (hsCRP), and a lower incidence of new-onset or worsening diabetes make it a useful adjunct for LDL-C lowering. However, the CV outcomes trial results are still pending. In this LAI consensus document, we discuss the pharmacology, indications, contraindications, advantages, and evidence-based recommendations for the use of bempedoic acid in clinical practice.

Vitamin D Deficiency Impacts Exposure and Response of Pravastatin in Male Rats by Altering Hepatic OATPs

This study aimed to determine the effect of vitamin D (VD) deficiency on the efficacy and pharmacokinetics of pravastatin and clarify whether the effects are mediated by Organic anion-transporting polypeptides (OATPs). Experiments were conducted in rats to explore the effect of VD deficiency on the pharmacodynamics and pharmacokinetics of pravastatin. In the pharmacodynamic study, rats were fed a VD-free or VD-supplement high-fat diet for 25–30 days, and plasma 25(OH)VD was dynamically monitored. The response of pravastatin (changes in blood lipids) on rats were then examined after 15 days of pravastatin treatment. In the pharmacokinetic study, rats were fed a VD-free or VD-supplement diet for 25–30 days. The pharmacokinetics of single oral dose pravastatin was then studied, and intestinal and hepatic Oatp1a1 and Oatp2b1 expression was determined using quantitative polymerase chain reaction (qPCR) and western blot. Furthermore, OATP1B1 and OATP2B1 expression in Huh7 cells with or without 1.25(OH)₂D were assessed via qPCR and western blot. For the pharmacodynamic study, the decrease of total cholesterol and increase of high-density lipoprotein cholesterol in VD-deficient rats were smaller than in VD-sufficient rats, indicating that VD deficiency reduced the response of pravastatin in rats. For the pharmacokinetic study, the plasma exposure slightly increased, and liver exposure decreased in VD-deficient rats, but not significantly. VD deficiency decreased the Oatp1a1 and Oatp2b1 expression in the liver, but not in the small intestine. Similarly, OATP1B1 and OATP2B1 protein levels in Huh7 cells were reduced when 1.25(OH)₂D was absent. In conclusion, VD deficiency can decrease the response of pravastatin in rats by reducing the liver pravastatin exposure and expression of hepatic OATPs, consistent with the extended hepatic clearance model theory.

Effect of type 2 diabetes on Gd-EOB-DTPA uptake into liver parenchyma: replication study in human subjects

PURPOSE

Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) is a contrast agent for magnetic resonance imaging (MRI), which specifically taken up by hepatocytes through organic anion-transporting polypeptides (OATPs). Previous research in mice has shown that type 2 diabetes is associated with reduced uptake of Gd-EOB-DTPA into the liver parenchyma, reflecting reduced expression of OATP. Since considerable differences in OATP expression exist between mice and humans, human studies are necessary to clarify the effect of diabetes to Gd-EOB-DTPA uptake. The purpose of this study was to validate the effect of diabetes to Gd-EOB-DTPA liver uptake by a confirmatory study in humans.

METHODS

Patients who underwent Gd-EOB-DTPA-enhanced MRI were retrospectively reviewed and divided into two groups: severe or uncontrolled diabetic group (patients with insulin therapy and/or HbA1c ≥ 8.4%) and the control group. Liver-to-spleen ratio (LSR) and relative enhancement of the liver (REL) were calculated to represent Gd-EOB-DTPA liver uptake.

RESULTS

A total of 94 patients fulfilled the criteria. The severe or uncontrolled diabetic group (n = 15) showed significantly lower LSR (1.74 ± 0.26 vs. 1.98 ± 0.31, p = 0.007) and REL (0.69 ± 0.23 vs. 0.87 ± 0.31, p = 0.005), compared to the control group (n = 79).

CONCLUSION

Our study revealed decreased uptake of Gd-EOB-DTPA into liver parenchyma in the severe or uncontrolled diabetic patients. Further studies to determine the impact of the reduced liver enhancement on clinical diagnostic practice will be needed.

Performance of Plasma Coproporphyrin I and III as OATP1B1 Biomarkers in Humans

A previous study in 356 healthy Finnish volunteers showed that glycochenodeoxycholate 3‐O‐glucuronide (GCDCA‐3G) and glycodeoxycholate 3‐O‐glucuronide (GDCA‐3G) are promising biomarkers of organic anion transporting polypeptide 1B1 (OATP1B1). In the same cohort, we now evaluated the performances of two other OATP1B1 biomarkers, coproporphyrin I (CPI) and III (CPIII), and compared them with GCDCA‐3G and GDCA‐3G. Based on decreased (*5 and *15) and increased (*14 and *20) function SLCO1B1 haplotypes, we stratified the participants to poor, decreased, normal, increased, and highly increased OATP1B1 function groups. Fasting plasma CPI concentration was 68% higher in the poor (95% confidence interval, 44%, 97%; P = 1.74 × 10⁻¹⁰), 7% higher in the decreased (0%, 15%; P = 0.0385), 10% lower in the increased (3%, 18%; P = 0.0087), and 23% lower in the highly increased (1%, 40%; P = 0.0387) function group than in the normal function group. CPIII concentration was 27% higher (7%, 51%; P = 0.0071) in the poor function group than in the normal function group. CPI and CPIII detected poor OATP1B1 function with areas under the precision‐recall curve (AUPRC) of 0.388 (95% confidence interval, 0.197, 0.689) and 0.0798 (0.0485, 0.203), and receiver operating characteristic curve (AUROC) of 0.888 (0.851, 0.919) and 0.731 (0.682, 0.776). The AUPRC and AUROC of GCDCA‐3G were, however, 0.389 (0.258, 0.563) and 0.100 (−0.0046, 0.204; P = 0.0610) larger than those of CPI, and 0.697 (0.555, 0.831) and 0.257 (0.141, 0.373; P < 0.0001) larger than those of CPIII. In conclusion, these data indicate that plasma CPI outperforms CPIII in detecting altered OATP1B1 function, but GCDCA‐3G is an even more sensitive OATP1B1 biomarker than CPI.

Assessment of the Effect of Filgotinib on the Pharmacokinetics of Atorvastatin, Pravastatin, and Rosuvastatin in Healthy Adult Participants

Filgotinib, an oral Janus kinase‐1 preferential inhibitor, is approved in Europe and Japan for adults with rheumatoid arthritis. Patients with rheumatoid arthritis are at higher risk of cardiovascular morbidity/mortality; thus, it is important to understand potential drug‐drug interactions of filgotinib with lipid‐lowering agents. This open‐label, randomized, 2‐way crossover study evaluated the pharmacokinetics of atorvastatin, pravastatin, and rosuvastatin with and without filgotinib coadministration. Healthy participants (N = 27) received single doses of atorvastatin (40 mg) and of a pravastatin (40 mg)/rosuvastatin (10 mg) cocktail—alone or with filgotinib (200 mg once daily for 11 days)—on 2 different occasions with washout in between. Serial pharmacokinetic blood samples were collected, and safety was assessed. Pharmacokinetic parameters were evaluated using 90% confidence intervals (CI) of the geometric least‐squares mean (GLSM) ratio of the test treatment (statin coadministration with filgotinib) vs statin alone, with prespecified lack‐of‐interaction bounds of 0.70 to 1.43. Coadministration of filgotinib did not affect atorvastatin area under the plasma concentration–time curve extrapolated to infinity (AUC_inf; [GLSM ratios (90% CI): 0.91 (0.84‐0.99)]), but maximum concentration [C_max] was slightly lower [0.82 (0.69‐0.99)]. The exposure of 2‐hydroxy‐atorvastatin was unaffected (GLSM ratios [90% CI], 0.98 [0.81‐1.19] for C_max; 1.11 [1.02‐1.22] for AUC_inf). Pravastatin AUC_inf was also unaffected (GLSM ratios, 1.22 [1.05‐1.41], but C_max was slightly higher 1.25 [1.01‐1.54]). Rosuvastatin exposure was moderately higher with filgotinib coadministration—GLSM ratios (90% CI), 1.68 (1.43‐1.97) for C_max; 1.42 (1.30‐1.57) for AUC_inf—but this was not considered clinically relevant. These results indicate that filgotinib has no clinically meaningful effect on exposure of atorvastatin, pravastatin, or rosuvastatin.

Effect of SLCO1B1 T521C on Statin-Related Myotoxicity With Use of Lovastatin and Atorvastatin

The association between the c.521T>C variant allele in SLCO1B1 (reference single nucleotide polymorphism (rs)4149056) and simvastatin-induced myotoxicity was discovered over a decade ago; however, whether this relationship represents a class effect is still not fully known. The aim of this study was to investigate the relationship between rs4149056 genotype and statin-induced myotoxicity in patients taking atorvastatin and lovastatin. Study participants were from the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort. A total of 233 statin-induced myopathy + rhabdomyolysis cases met the criteria for inclusion and were matched to 2,342 controls. To validate the drug response phenotype, we replicated the previously established association between rs4149056 genotype and simvastatin-induced myotoxicity. In particular, compared with homozygous T allele carriers, there was a significantly increased risk of simvastatin-induced myopathy + rhabdomyolysis in homozygous carriers of the C allele (CC vs. TT, odds ratio [OR] 4.62, 95% confidence interval [CI] 1.58-11.90, P = 0.003). For lovastatin users, homozygous carriers of the C allele were also at increased risk of statin-induced myopathy + rhabdomyolysis (CC vs. TT, OR 4.49, 95% CI 1.68-10.80, P = 0.001). In atorvastatin users, homozygous carriers of the C allele were twice as likely to experience statin-induced myopathy, though this association did not achieve statistical significance (CC vs. TT, OR 2.00, 95% CI 0.44-6.59, P = 0.30). In summary, our findings suggest that the association of rs4149056 with simvastatin-related myotoxicity may also extend to lovastatin. More data is needed to determine the extent of the association in atorvastatin users. Altogether, these data expand the evidence base for informing guidelines of pharmacogenetic-based statin prescribing practices.

Role of Bempedoic Acid in Clinical Practice

Many patients do not achieve optimal low-density lipoprotein cholesterol (LDL-C) levels with statins alone; others are unable to tolerate statin therapy. Additional non-statin treatment options including ezetimibe, proprotein convertase subtilisin/kexin type 9 inhibitors, and bile acid sequestrants are often necessary to further reduce the risk of atherosclerotic cardiovascular disease. This review provides practical guidance as to the use of bempedoic acid to lower LDL-C and includes direction as to which patients may benefit and advice for safety monitoring during treatment. Bempedoic acid, a new class of agent, is a prodrug converted to bempedoyl-CoA by very long-chain acyl-CoA synthetase 1, an enzyme with high expression in the liver but that is undetectable in the skeletal muscle. Bempedoic acid inhibits the enzyme adenosine triphosphate (ATP)-citrate lyase, which lies two steps upstream from β-hydroxy β-methylglutaryl-CoA reductase in the cholesterol biosynthesis pathway. In clinical trials conducted in patients with or at risk for atherosclerotic cardiovascular disease or familial heterozygous hypercholesterolemia, bempedoic acid in combination with statins and/or ezetimibe significantly reduced LDL-C, apolipoprotein B, and high-sensitivity C-reactive protein compared with placebo. Bempedoic acid is generally well tolerated with no clinically meaningful increase in muscle-related symptoms relative to placebo, even in patients taking maximally tolerated statins. A small increase in serum uric acid (mean increase 0.8 mg/dL) is the most noteworthy adverse effect. Bempedoic acid provides an effective and generally well-tolerated medication to further reduce LDL-C in patients taking maximally tolerated statins or manage LDL-C levels in those who are unable to take statins. The potential for a reduced incidence of major cardiovascular events with bempedoic acid is being investigated in the CLEAR Outcomes trial, with results expected in 2023.

Efficacy and safety of statins in ethnic differences: a lesson for application in Indigenous Australian patient care

Although statins are effective in treating high cholesterol, adverse effects do occur with their use. Efficacy and tolerability vary among statins in different ethnic groups. Indigenous Australians have a high risk for cardiovascular and kidney diseases. Prescribing statins to Indigenous Australians with multi-morbidity requires different strategies to increase efficacy and reduce their toxicity. Previous studies have reported that Indigenous Australians are more susceptible to severe statin-induced myopathies. However, there is a lack of evidence in the underlying genetic factors in this population. This review aims to identify: inter-ethnic differences in the efficacy and safety of statins; major contributing factors accounting for any identified differences; and provide an overview of statin-induced adverse effects in Indigenous Australians.

Zebrafish as a Model for the Study of Lipid-Lowering Drug-Induced Myopathies

Drug-induced myopathies are classified as acquired myopathies caused by exogenous factors. These pathological conditions develop in patients without muscle disease and are triggered by a variety of medicaments, including lipid-lowering drugs (LLDs) such as statins, fibrates, and ezetimibe. Here we summarise the current knowledge gained via studies conducted using various models, such as cell lines and mammalian models, and compare them with the results obtained in zebrafish (Danio rerio) studies. Zebrafish have proven to be an excellent research tool for studying dyslipidaemias as a model of these pathological conditions. This system enables in-vivo characterization of drug and gene candidates to further the understanding of disease aetiology and develop new therapeutic strategies. Our review also considers important environmental issues arising from the indiscriminate use of LLDs worldwide. The widespread use and importance of drugs such as statins and fibrates justify the need for the meticulous study of their mechanism of action and the side effects they cause.

The Food Contaminants Pyrrolizidine Alkaloids Disturb Bile Acid Homeostasis Structure-Dependently in the Human Hepatoma Cell Line HepaRG

Pyrrolizidine alkaloids (PAs) are a group of secondary plant metabolites being contained in various plant species. The consumption of contaminated food can lead to acute intoxications in humans and exert severe hepatotoxicity. The development of jaundice and elevated bile acid concentrations in blood have been reported in acute human PA intoxication, indicating a connection between PA exposure and the induction of cholestasis. Additionally, it is considered that differences in toxicity of individual PAs is based on their individual chemical structures. Therefore, we aimed to elucidate the structure-dependent disturbance of bile acid homeostasis by PAs in the human hepatoma cell line HepaRG. A set of 14 different PAs, including representatives of all major structural characteristics, namely, the four different necine bases retronecine, heliotridine, otonecine and platynecine and different grades of esterification, was analyzed in regard to the expression of genes involved in bile acid synthesis, metabolism and transport. Additionally, intra- and extracellular bile acid levels were analyzed after PA treatment. In summary, our data show significant structure-dependent effects of PAs on bile acid homeostasis. Especially PAs of diester type caused the strongest dysregulation of expression of genes associated with cholestasis and led to a strong decrease of intra- and extracellular bile acid concentrations.

Structure and Function of Hepatobiliary ATP Binding Cassette Transporters

The liver is beyond any doubt the most important metabolic organ of the human body. This function requires an intensive crosstalk within liver cellular structures, but also with other organs. Membrane transport proteins are therefore of upmost importance as they represent the sensors and mediators that shuttle signals from outside to the inside of liver cells and/or vice versa. In this review, we summarize the known literature of liver transport proteins with a clear emphasis on functional and structural information on ATP binding cassette (ABC) transporters, which are expressed in the human liver. These primary active membrane transporters form one of the largest families of membrane proteins. In the liver, they play an essential role in for example bile formation or xenobiotic export. Our review provides a state of the art and comprehensive summary of the current knowledge of hepatobiliary ABC transporters. Clearly, our knowledge has improved with a breath-taking speed over the last few years and will expand further. Thus, this review will provide the status quo and will lay the foundation for new and exciting avenues in liver membrane transporter research.

Functional Consequences of Pravastatin Isomerization on OATP1B1-Mediated Transport

Pravastatin acid (PVA) can be isomerized to its inactive metabolite 3'α-iso-pravastatin acid (3αPVA) under acidic pH conditions. Previous studies reported interindividual differences in circulating concentrations of PVA and 3αPVA. This study investigated the functional consequences of PVA isomerization on OATP1B1-mediated transport. We characterized 3αPVA inhibition of OATP1B1-mediated PVA uptake into human embryonic kidney 293 cells expressing the four different OATP1B1 proteins (*1a, *1b, *5, and *15). 3αPVA inhibited OATP1B1-mediated PVA uptake in all four OATP1B1 gene products but with lower IC50/Ki values for OATP1B1*5 and *15 than for the reference proteins (*1a and *1b). PVA and 3αPVA were transported by all four OATP1B1 proteins. Kinetic experiments revealed that maximal transport rates (Vmax values) for OATP1B1 variants *5 and *15 were lower than for *1a and *1b for both substrates. Apparent affinities for 3αPVA transport were similar for all four variants. However, the apparent affinity of OATP1B1*5 for 3αPVA was higher (lower Km value) than for PVA. These data confirm that PVA conversion to 3αPVA can have functional consequences on PVA uptake and impacts OATP1B1 variants more than the reference protein, thus highlighting another source variation that must be taken into consideration when optimizing the PVA dose-exposure relationship for patients. SIGNIFICANCE STATEMENT: 3'α-iso-pravastatin acid inhibits pravastatin uptake for all OATP1B1 protein types; however, the IC50 values were significantly lower in OATP1B1*5 and *15 transfected cells. This suggests that a lower concentration of 3'α-iso-pravastatin is needed to disrupt OATP1B1-mediated pravastatin uptake, secondary to decreased cell surface expression of functional OATP1B1 in variant-expressing cells. These data will refine previous pharmacokinetic models that are utilized to characterize pravastatin interindividual variability with an ultimate goal of maximizing efficacy at the lowest possible risk for toxicity.

Identification of Glycochenodeoxycholate 3-O-Glucuronide and Glycodeoxycholate 3-O-Glucuronide as Highly Sensitive and Specific OATP1B1 Biomarkers

The aim of this study was to investigate the sensitivity and specificity of endogenous glycochenodeoxycholate and glycodeoxycholate 3-O-glucuronides (GCDCA-3G and GDCA-3G) as substrates for organic anion transporting polypeptide 1B1 (OATP1B1) in humans. We measured fasting levels of plasma GCDCA-3G and GDCA-3G using liquid chromatography-tandem mass spectrometry in 356 healthy volunteers. The mean plasma levels of both compounds were ~ 50% lower in women than in men (P = 2.25 × 10^-18 and P = 4.73 × 10^-9 ). In a microarray-based genome-wide association study, the SLCO1B1 rs4149056 (c.521T>C, p.Val174Ala) variation showed the strongest association with the plasma GCDCA-3G (P = 3.09 × 10^-30 ) and GDCA-3G (P = 1.60 × 10^-17 ) concentrations. The mean plasma concentration of GCDCA-3G was 9.2-fold (P = 8.77 × 10^-31 ) and that of GDCA-3G was 6.4-fold (P = 2.45x10^-13 ) higher in individuals with the SLCO1B1 c.521C/C genotype than in those with the c.521T/T genotype. No other variants showed independent genome-wide significant associations with GCDCA-3G or GDCA-3G. GCDCA-3G was highly efficacious in detecting the SLCO1B1 c.521C/C genotype with an area under the receiver operating characteristic curve of 0.996 (P < 0.0001). The sensitivity (98-99%) and specificity (100%) peaked at a cutoff value of 180 ng/mL for men and 90 ng/mL for women. In a haplotype-based analysis, SLCO1B1*5 and *15 were associated with reduced, and SLCO1B1*1B, *14, and *35 with increased OATP1B1 function. In vitro, both GCDCA-3G and GDCA-3G showed at least 6 times higher uptake by OATP1B1 than OATP1B3 or OATP2B1. These data indicate that the hepatic uptake of GCDCA-3G and GDCA-3G is predominantly mediated by OATP1B1. GCDCA-3G, in particular, is a highly sensitive and specific OATP1B1 biomarker in humans.

Beverage-Drug Interaction: Effects of Green Tea Beverage Consumption on Atorvastatin Metabolism and Membrane Transporters in the Small Intestine and Liver of Rats

Green tea (GT) beverages are popular worldwide and may prevent the development of many chronic diseases including cardiovascular disease and cancer. To investigate whether the consumption of a GT beverage causes drug interactions, the effects of GT beverage consumption on atorvastatin metabolism and membrane transporters were evaluated. Male rats were fed a chow diet with tap water or the GT beverage for 3 weeks. Then, the rats were given a single oral dose (10 mg/kg body weight (BW)) of atorvastatin (ATV), and blood was collected at various time points within 6 h. The results show that GT consumption increased the plasma concentrations (AUC_0–6h) of ATV (+85%) and 2-OH ATV (+93.3%). GT also increased the 2-OH ATV (+40.9%) and 4-OH ATV (+131.6%) contents in the liver. Decreased cytochrome P450 (CYP) 3A enzyme activity, with no change in P-glycoprotein expression in the intestine, was observed in rats treated with GT. Additionally, GT increased hepatic CYP3A-mediated ATV metabolism and decreased organic anion transporting polypeptides (OATP) 2 membrane protein expression. There was no significant difference in the membrane protein expression of OATP2B1 and P-glycoprotein in the intestine and liver after the GT treatment. The results show that GT consumption may lower hepatic OATP2 and, thus, limit hepatic drug uptake and increase plasma exposure to ATV and 2-OH ATV.

Combined QSAR Model and Chemical Similarity Search for Novel HMG-CoA Reductase Inhibitors for Coronary Heart Disease

Background:

Coronary heart disease generally occurs due to cholesterol accumulation in the walls of the heart arteries. Statins are the most widely used drugs which work by inhibiting the active site of 3-Hydroxy-3-methylglutaryl-CoA reductase (HMGCR) enzyme that is responsible for cholesterol synthesis. A series of atorvastatin analogs with HMGCR inhibition activity have been synthesized experimentally which would be expensive and time-consuming.

Methods:

In the present study, we employed both the QSAR model and chemical similarity search for identifying novel HMGCR inhibitors for heart-related diseases. To implement this, a 2D QSAR model was developed by correlating the structural properties to their biological activity of a series of atorvastatin analogs reported as HMGCR inhibitors. Then, the chemical similarity search of atorvastatin analogs was performed by using PubChem database search.

Results and Discussion:

The three-descriptor model of charge (GATS1p), connectivity (SCH-7) and distance (VE1_D) of the molecules is obtained for HMGCR inhibition with the statistical values of R2= 0.67, RMSEtr= 0.33, R2 ext= 0.64 and CCCext= 0.76. The 109 novel compounds were obtained by chemical similarity search and the inhibition activities of the compounds were predicted using QSAR model, which were close in the range of experimentally observed threshold.

Conclusion:

The present study suggests that the QSAR model and chemical similarity search could be used in combination for identification of novel compounds with activity by in silico with less computation and effort.

Species differences in the drug-drug interaction between atorvastatin and cyclosporine: In vivo study using a stable isotope-IV method in rats and dogs

In this study, drug-drug interaction (DDI) between atorvastatin (ATV) and cyclosporine (CsA) was kinetically analyzed using a stable isotope-IV method in rats and dogs. Obtained results were compared with the clinical data quoted from literatures to clarify the species difference in DDI both qualitatively and quantitatively. ATV only or ATV with CsA was orally administered to rats or dogs, and at 90 minutes after administration, a small amount of deuterium labeled ATV (ATV-d5) was intravenously injected. Assuming that ATV-d5 exhibits the same pharmacokinetic (PK) profile with ATV, PK parameters for absorption and elimination of ATV were calculated. Plasma levels of orally administered ATV were significantly enhanced by co-administration of CsA both in rats, dogs and humans, resulted in 9.8, 31, and 8.7-fold increase in systemic exposure calculated as AUC_po. High intensity of the DDI in dogs was mainly attributed to the marked decrease of the intrinsic hepatic clearance (to 1/10 of the control), which was induced by the inhibition of hepatic uptake of ATV via organic anion transporting polypeptide 1B1 (OATP1B1). CsA also affected the absorption of ATV form GI tract. Absorbed fraction of ATV into portal vein (calculated as F_a*F_g) was increased almost same extent in rats and dogs (around 3.0-fold) by co-administration of CsA. Inhibition of efflux transport via breast cancer resistance protein as well as the intestinal metabolism mediated by CYP enzymes contributed to the DDI occurred in the intestinal tract. In conclusion, PK analysis on the DDI between ATV and CsA in rats and dogs clearly demonstarted the factors to cause species differences in the extent of DDI. This type of quantitative analysis of DDIs in both small and large animals can be a great help to predict the extent of DDI in humans in the clinical study.

Influence of SLCO1B1 polymorphisms on lopinavir Ctrough in Serbian HIV/AIDS patients

AIMS

Lopinavir (LPV) is not a first-line regimen. According to recent WHO data, LPV usage in low- and middle-income countries accounted for approximately 52% of the adult and 23% of the paediatric protease inhibitor market in 2017. Since LPV is a substrate for the SLCO1B1 (OATP1B1) transporter, the aim of this study was to assess the impact of SLCO1B1 polymorphisms (rs11045819, rs4149032 and rs4149056) on LPV trough plasma concentrations (C_trough ) in Serbian patients.

METHODS

Plasma samples from 104 HIV/AIDS Caucasians were collected. LPV C_trough was quantified using liquid-chromatography-mass spectrometry. Genotyping was carried out using real-time-PCR-based allelic discrimination. One-way analysis of variance, t test and linear regression were used for data analysis.

RESULTS

The overall mean (SD) LPV C_trough was 5885 ± 2755 ng/mL. Significant differences were between patients with different rs11045819 genotypes: CC (LPV median C_trough = 6072 ng/mL, interquartile range (IQR) = 4318-7617 ng/mL), CA (LPV median C_trough = 4987 ng/mL, IQR = 4300-6295 ng/mL) and AA (LPV median C_trough = 3648 ng/mL, IQR = 1949-4072 ng/mL) (P = .005). Significant differences were also observed according to rs4149032 genotype: CC (LPV median C_trough = 6027 ng/mL, IQR =4548-8250 ng/mL), CT (LPV median C_trough = 5553 ng/mL, IQR = 4300-6888 ng/mL) and TT (LPV median C_trough = 4408 ng/mL, IQR = 3361-5233 ng/mL) (P = .007). For rs4149056 a statistically significant difference between T-homozygotes (LPV median C_trough = 5434 ng/mL, IQR = 3855-6830 ng/mL), heterozygotes (LPV median C_trough = 6707 ng/mL, IQR = 5088-8063 ng/mL) and C-homozygotes (LPV median C_trough = 13906 ng/mL, IQR = 12946-14866 ng/mL) was observed (P = .002). In multivariate regression analysis, only the SLCO1B1 rs4149056 polymorphism was independently associated with higher LPV C_trough (β = 2834.5 [1442-4226.9] ng/mL [P = .001]).

CONCLUSIONS

Our results demonstrate a statistically significant influence of the SLCO1B1 rs4149056 polymorphism on higher LPV C_trough in Caucasian HIV/AIDS patients.

Interaction of Oatp1b2 expression and nonalcoholic steatohepatitis on pravastatin plasma clearance

The downregulation of hepatic uptake transporters, including those of the OATP family, are a well known consequence of nonalcoholic steatohepatitis (NASH). Prior studies have shown that the combination of NASH and Oatp1b2 knockout synergistically reduces the clearance of pravastatin (PRAV) in the methionine and choline deficient (MCD) mouse model of NASH, and the current study therefore aimed to determine the impact of NASH and genetic heterozygosity of Oatp1b2 on PRAV clearance, modeling the overlap between the 24% of the human population who are heterozygous for non-functioning OATP1B1, and the ~15% with NASH, potentially placing these people at higher risk of statin-induced myopathy. Therefore, male C57BL/6 wild-type (WT), Oatp1b2+/- (HET), and Oatp1b2-/- (KO) mice were fed either a control (methionine and choline sufficient) or methionine and choline-deficient (MCD) diet to induce NASH. After six weeks of feeding, pravastatin was administered via the carotid artery. Blood and bile samples were collected throughout 90 min after PRAV administration. The concentration of PRAV in plasma, bile, liver, kidney, and muscle was determined by liquid chromatography-tandem mass spectrometry. MCD diet did not alter the plasma AUC values of PRAV in either WT or HET mice. However, the MCD diet increased plasma AUC by 4.4-fold in KO mice. MCD diet and nonfunctional Oatp1b2 synergistically increased not only plasma AUC but also the extrahepatic tissue concentration of pravastatin, whereas the partially decreased function of Oatp1b2 and NASH together were insufficient in significantly altering PRAV pharmacokinetics. These data suggest that a single copy of fully functional OATP1B1 in NASH patients may be sufficient to avoid the increase of pravastatin toxicity.

A hybrid model to evaluate the impact of active uptake transport on hepatic distribution of atorvastatin in rats

1. Mathematical modeling remains a useful tool to study the impact of transporters on overall and intracellular drug disposition. The impact of organic anion transporter protein mediated uptake on atorvastatin systemic and intracellular pharmacokinetics, specifically distribution volume, was studied in rats with mathematical modeling and conducting in vivo pharmacokinetic studies for atorvastatin in presence and absence of rifampicin. A previously developed 5-compartment explicit membrane model for the liver was combined with a compartmental model to develop a semi-physiological hybrid model for atorvastatin disposition. 2. Rifampicin treatment resulted in a decrease in systemic clearance and steady-state distribution volume, and an increase in half-life of atorvastatin. The hybrid model predicted higher unbound intracellular liver atorvastatin concentrations than unbound plasma concentrations in both rifampicin treated and untreated groups, indicating involvement of uptake transporters. The intracellular unbound concentrations during the distributive phase were unaffected by rifampicin. The dependence of clearance on blood flow as well as hepatic uptake for atorvastatin (a moderate-to-high extraction ratio drug) can explain this lack of change in intracellular concentrations if there is incomplete inhibition of transport at the tested rifampicin dose. 3. The hybrid model successfully allowed the evaluation of effect of active uptake on intracellular and plasma atorvastatin disposition.

Understanding Cell Penetration of Cyclic Peptides

Approximately 75% of all disease-relevant human proteins, including those involved in intracellular protein-protein interactions (PPIs), are undruggable with the current drug modalities (i.e., small molecules and biologics). Macrocyclic peptides provide a potential solution to these undruggable targets because their larger sizes (relative to conventional small molecules) endow them the capability of binding to flat PPI interfaces with antibody-like affinity and specificity. Powerful combinatorial library technologies have been developed to routinely identify cyclic peptides as potent, specific inhibitors against proteins including PPI targets. However, with the exception of a very small set of sequences, the vast majority of cyclic peptides are impermeable to the cell membrane, preventing their application against intracellular targets. This Review examines common structural features that render most cyclic peptides membrane impermeable, as well as the unique features that allow the minority of sequences to enter the cell interior by passive diffusion, endocytosis/endosomal escape, or other mechanisms. We also present the current state of knowledge about the molecular mechanisms of cell penetration, the various strategies for designing cell-permeable, biologically active cyclic peptides against intracellular targets, and the assay methods available to quantify their cell-permeability.

The influence of bariatric surgery on oral drug bioavailability in patients with obesity: A systematic review

Anatomical changes in the gastrointestinal tract and subsequent weight loss may influence drug disposition and thus drug dosing following bariatric surgery. This review systematically examines the effects of bariatric surgery on drug pharmacokinetics, focusing especially on the mechanisms involved in restricting oral bioavailability. Studies with a longitudinal before-after design investigating the pharmacokinetics of at least one drug were reviewed. The need for dose adjustment following bariatric surgery was examined, as well as the potential for extrapolation to other drugs subjected to coinciding pharmacokinetic mechanisms. A total of 22 original articles and 32 different drugs were assessed. The majority of available data is based on Roux-en-Y gastric bypass (RYGBP) (18 of 22 studies), and hence, the overall interpretation is more or less limited to RYGBP. In the case of the majority of studied drugs, an increased absorption rate was observed early after RYGBP. The effect on systemic exposure allows for a low degree of extrapolation, including between drugs subjected to the same major metabolic and transporter pathways. On the basis of current understanding, predicting the pharmacokinetic change for a specific drug following RYGBP is challenging. Close monitoring of each individual drug is therefore recommended in the early postsurgical phase. Future studies should focus on the long-term effects of bariatric surgery on drug disposition, and they should also aim to disentangle the effects of the surgery itself and the subsequent weight loss.

Characterization of Plasma Membrane Localization and Phosphorylation Status of Organic Anion Transporting Polypeptide (OATP) 1B1 c.521 T>C Nonsynonymous Single-Nucleotide Polymorphism

PURPOSE

Membrane transport protein organic anion transporting polypeptide (OATP) 1B1 mediates hepatic uptake of many drugs (e.g. statins). The OATP1B1 c.521 T > C (p. V174A) polymorphism has reduced transport activity. Conflicting in vitro results exist regarding whether V174A-OATP1B1 has reduced plasma membrane localization; no such data has been reported in physiologically relevant human liver tissue. Other potential changes, such as phosphorylation, of the V174A-OATP1B1 protein have not been explored. Current studies characterized the plasma membrane localization of V174A-OATP1B1 in genotyped human liver tissue and cell culture and compared the phosphorylation status of V174A- and wild-type (WT)-OATP1B1.

METHODS

Localization of V174A- and WT-OATP1B1 were determined in OATP1B1 c.521 T > C genotyped human liver tissue (n = 79) by immunohistochemistry and in transporter-overexpressing human embryonic kidney (HEK) 293 and HeLa cells by surface biotinylation and confocal microscopy. Phosphorylation and transport of OATP1B1 was determined using 32P-orthophosphate labeling and [3H]estradiol-17β-glucuronide accumulation, respectively.

RESULTS

All three methods demonstrated predominant plasma membrane localization of both V174A- and WT-OATP1B1 in human liver tissue and in cell culture. Compared to WT-OATP1B1, the V174A-OATP1B1 has significantly increased phosphorylation and reduced transport.

CONCLUSIONS

We report novel findings of increased phosphorylation, but not impaired membrane localization, in association with the reduced transport function of the V174A-OATP1B1.

Genome-wide association meta-analysis for total thyroid hormone levels in Croatian population

Thyroid hormones (THs) are key regulators of cellular growth, development, and metabolism. The thyroid gland secretes two THs, thyroxine (T4) and triiodothyronine (T3), into the plasma where they are almost all bound reversibly to plasma proteins. Free forms of THs are metabolically active, however, they represent a very small fraction of total TH levels. No genome-wide studies have been performed to date on total TH levels, comprising of protein-bound and free forms of THs. To detect genetic variants associated with total TH levels, we carried out the first GWAS meta-analysis of total T4 levels in 1121 individuals from two Croatian cohorts (Split and Korcula). We also performed GWAS analyses of total T3 levels in 577 individuals and T3/T4 ratio in 571 individuals from the Split cohort. The top association in GWAS meta-analysis of total T4 was detected for an intronic variant within SLC22A9 gene (rs12282281, P = 4.00 × 10^-7). Within the same region, a genome-wide significant variant (rs11822642, P = 2.50 × 10^-8) for the T3/T4 ratio was identified. SLC22A9 encodes for an organic anion transporter protein expressed predominantly in the liver and belongs to the superfamily of solute carriers (SLC), a large group of transport membrane proteins. The transport of THs across the plasma membrane in peripheral tissues is facilitated by the membrane proteins, and all TH transport proteins known to date belong to the same SLC superfamily as SLC22A9. These results suggest a potential role for SLC22A9 as a novel transporter protein of THs.

Impact of Genetic Variation on Pravastatin Systemic Exposure in Pediatric Hypercholesterolemia

This study investigated the impact of SLCO1B1 genotype on pravastatin systemic exposure in children and adolescents with hypercholesterolemia. Participants (8-20 years) with at least one allelic variant of SLCO1B1 c.521T>C (521TC, n = 15; 521CC, n = 2) and wild-type controls (521TT, n = 15) completed a single oral dose pharmacokinetic study. Interindividual variability of pravastatin acid (PVA) exposure within SLCO1B1 genotype groups exceeded the approximately twofold difference in mean PVA exposure observed between SLCO1B1 genotype groups (P > 0.05, q > 0.10). The 3'α-iso-pravastatin acid and lactone isomer formation in the acidic environment of the stomach prior to absorption also was variable and affected PVA exposure in all genotype groups. The SLCO1B1 c.521 gene variant contributing to variability in systemic exposure to PVA in our pediatric cohort was comparable to previous studies in adults. However, other demographic and physicochemical factors seem to also contribute to interindividual variability in the dose-exposure relationship.

Application of the relationship between pharmacokinetics and pharmacodynamics in drug development and therapeutic equivalence: a PEARRL review

Objectives

The objective of this review was to provide an overview of pharmacokinetic/pharmacodynamic (PK/PD) models, focusing on drug-specific PK/PD models and highlighting their value added in drug development and regulatory decision-making.

Key findings

Many PK/PD models, with varying degrees of complexity and physiological understanding have been developed to evaluate the safety and efficacy of drug products. In special populations (e.g. paediatrics), in cases where there is genetic polymorphism and in other instances where therapeutic outcomes are not well described solely by PK metrics, the implementation of PK/PD models is crucial to assure the desired clinical outcome. Since dissociation between the pharmacokinetic and pharmacodynamic profiles is often observed, it is proposed that physiologically based pharmacokinetic and PK/PD models be given more weight by regulatory authorities when assessing the therapeutic equivalence of drug products.

Summary

Modelling and simulation approaches already play an important role in drug development. While slowly moving away from ‘one-size fits all’ PK methodologies to assess therapeutic outcomes, further work is required to increase confidence in PK/PD models in translatability and prediction of various clinical scenarios to encourage more widespread implementation in regulatory decision-making.

Association between SLCO1B1 rs4149056 and tegafur-uracil-induced hepatic dysfunction in breast cancer

Aim: The aim of this study was to identify pharmacogenomic biomarkers to predict tegafur-uracil (UFT)-induced liver dysfunction. Patients & methods: A total of 68 patients, who were administered UFT, were evaluated using a two-step pharmacogenomics analysis. Results: The first screening revealed the association between five SNPs and UFT-induced hepatic dysfunction. In the second step, SLCO1B1 (rs4149056) was found to be the only SNP associated with UFT treatment-related elevation of aspartate aminotransferase (odds ratio: C/C vs T/T = 7.8, C/T vs T/T = 5.7; p = 0.037) and alanine transaminase (odds ratio: C/C vs T/T = 12.2, C/T vs T/T = 4.1; p = 0.034) levels. Conclusion: The SLCO1B1 polymorphisms are possible predictors of UFT treatment-related hepatic dysfunction.

Protein expression and function of organic anion transporters in short-term and long-term cultures of Huh7 human hepatoma cells

Human-derived hepatic cell lines are a valuable alternative to primary hepatocytes for drug metabolism, transport and toxicity studies. However, their relevance for investigations of drug-drug and drug-organic anion (e.g., bile acid, steroid hormone) interactions at the transporter level remains to be established. The aim of the present study was to determine the suitability of the Huh7 cell line for transporter-dependent experiments. Huh7 cells were cultured for 1 to 4 weeks and subsequently were analyzed for protein expression, localization and activity of solute carrier (SLC) and ATP-binding cassette (ABC) transporters involved in organic anion transport using liquid chromatography-tandem mass spectroscopy, immunocytochemistry, and model substrates [³H]taurocholate (TCA), [³H]dehydroepiandrosterone sulfate (DHEAS) and 5(6)-carboxy-2',7'-dichlorofluorescein (CDF) diacetate. The extended 4-week culture resulted in a phenotype resembling primary hepatocytes and differentiated HepaRG cells: cuboidal hepatocyte-like cells with elongated bile canaliculi-like structures were surrounded by epithelium-like cells. Protein expression of OSTα, OSTβ and OATP1B3 increased over time. Moreover, the uptake of the SLC probe substrate DHEAS was higher in 4-week than in 1-week Huh7 cultures. NTCP, OATP1B1, BSEP and MRP3 were barely or not detectable in Huh7 cells. OATP2B1, MRP2 and MRP4 protein expression remained at similar levels over the four weeks of culture. The activity of MRP2 and the formation of bile canaliculi-like structures were confirmed by accumulation of CDF in the intercellular compartments. Results indicate that along with morphological maturation, transporters responsible for alternative bile acid secretion pathways are expressed and active in long-term cultures of Huh7 cells, suggesting that differentiated Huh7 cells may be suitable for studying the function and regulation of these organic anion transporters.

Statins and the Brain: More than Lipid Lowering Agents?

BACKGROUND

Statins represent a class of medications widely prescribed to efficiently treat dyslipidemia. These drugs inhibit 3-βhydroxy 3β-methylglutaryl Coenzyme A reductase (HMGR), the rate-limiting enzyme of mevalonate (MVA) pathway. Besides cholesterol, MVA pathway leads to the production of several other compounds, which are essential in the regulation of a plethora of biological activities, including in the central nervous system. For these reasons, statins are able to induce pleiotropic actions, and acquire increased interest as potential and novel modulators in brain processes, especially during pathological conditions.

OBJECTIVE

The purpose of this review is to summarize and examine the current knowledge about pharmacokinetic and pharmacodynamic properties of statins in the brain. In addition, effects of statin on brain diseases are discussed providing the most up-to-date information.

METHODS

Relevant scientific information was identified from PubMed database using the following keywords: statins and brain, central nervous system, neurological diseases, neurodegeneration, brain tumors, mood, stroke.

RESULTS

315 scientific articles were selected and analyzed for the writing of this review article. Several papers highlighted that statin treatment is effective in preventing or ameliorating the symptomatology of a number of brain pathologies. However, other studies failed to demonstrate a neuroprotective effect.

CONCLUSION

Even though considerable research studies suggest pivotal functional outcomes induced by statin therapy, additional investigation is required to better determine the pharmacological effectiveness of statins in the brain, and support their clinical use in the management of different neuropathologies.

Genetic variability and population diversity of the human SLCO (OATP) transporter family

Organic anion transporting polypeptides (OATP) encoded by the SLCO gene family constitute clinically important transporters involved in the disposition of endogenous compounds and many commonly prescribed drugs, including statins, methotrexate and antihypertensive medications. Common genetic polymorphisms in SLCO genes are known to affect OATP function and modulate efficacy and safety of OATP substrates. However, current frequency data of these variants and haplotypes is generally based on few rather heterogenous populations of relatively small sample size. Furthermore, the genetic variability beyond these selected pharmacogenetic biomarkers has not been systematically analyzed. Here, we provide a global consolidated map of SLCO variability by leveraging fully compatible Next Generation Sequencing data from 138,632 unrelated individuals across seven major human populations. Overall, we find 9811 exonic single nucleotide variants and 155 copy number variations of which 99.3% were rare with frequencies <1%. Using orthogonal computational functionality predictors optimized for pharmacogenetic assessments, we find that four out of five individuals carry at least one deleterious variant in an SLCO transporter gene and rare variants contribute 23% to the genetically encoded functional variability. Moreover, 74.9% of all variants were found to be population-specific with important consequences for population-specific genotyping strategies and precision public health approaches. Combined, our analyses provide the most comprehensive data set of SLCO variability published to date and incentivize the integration of comprehensive NGS-based genotyping into personalized predictions of OATP substrate disposition.

Associations of the SLCO1B1 Polymorphisms With Hepatic Function, Baseline Lipid Levels, and Lipid-lowering Response to Simvastatin in Patients With Hyperlipidemia

Our goal was to examine the associations of the 388A>G and 521T>C polymorphisms in the solute carrier organic anion transporter 1B1 (SLCO1B1) gene with hepatic function, baseline lipid levels, and the lipid-lowering efficiency of simvastatin. We recruited 542 patients with hyperlipidemia. The 388A>G and 521T>C polymorphisms were genotyped. Serum alanine aminotransferase (ALT) and aspartate transaminase (AST), Serum triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) levels were measured before and after an oral 20-mg dose of simvastatin. Individuals with the 388AA genotype had higher ALT and AST levels than those with the 388AG or 388GG genotypes (P = .037 and P = .002, respectively). Individuals with both the 388AA and the 521TT genotypes had the highest levels of ALT and AST (P = .001 and P = .001, respectively). Moreover, we divided all patients into normal and abnormal subgroups based on elevated ALT and AST values (≥ 40 U/L), participants in the abnormal subgroup had a higher frequency of the 388A/521T haplotype and a lower frequency of the 388G/521T haplotype compared to those in the normal subgroup.  In addition, compared to 388G allele and 521C allele carriers, individuals with the 388G allele and 521TT genotype carriers had greater TC and LDL-C reduction in response to simvastatin after 4 weeks of treatment. Our conclusion suggests that the interaction between the SLCO1B1 388A>G and 521T>C polymorphisms could be an important genetic determinant of hepatic function and the therapeutic efficiency of simvastatin in Chinese patients with hyperlipidemia.

Comparison of uptake transporter functions in hepatocytes in different species to determine the optimal model for evaluating drug transporter activities in humans

A thorough understanding of species-dependent differences in hepatic uptake transporters is critical for predicting human pharmacokinetics (PKs) from preclinical data. In this study, the activities of organic anion transporting polypeptide (OATP/Oatp), organic cation transporter 1 (OCT1/Oct1), and sodium-taurocholate cotransporting polypeptide (NTCP/Ntcp) in cultured rat, dog, monkey and human hepatocytes were compared. The activities of hepatic uptake transporters were evaluated with respect to culture duration, substrate and species-dependent differences in hepatocytes. Longer culture duration reduced hepatic uptake transporter activities across species except for Oatp and Ntcp in rats. Comparable apparent Michaelis-Menten constant (K_m,app) values in hepatocytes were observed across species for atorvastatin, estradiol-17β-glucuronide and metformin. The K_m,app values for rosuvastatin and taurocholate were significantly different across species. Rat hepatocytes exhibited the highest Oatp percentage of uptake transporter-mediated permeation clearance (PS_inf,act) while no difference in %PS_inf,act of probe substrates were observed across species. The in vitro hepatocyte inhibition data in rats, monkeys and humans provided reasonable predictions of in vivo drug-drug interaction (DDIs) between atorvastatin/rosuvastatin and rifampin. These findings suggested that using human hepatocytes with a short culture time is the most robust preclinical model for predicting DDIs for compounds exhibiting active hepatic uptake in humans.

A Clinical Quantitative Evaluation of Hepatobiliary Transport of [11C]Dehydropravastatin in Humans Using Positron Emission Tomography

Various positron emission tomography (PET) probes have been developed to assess in vivo activities in humans of drug transporters, which aid in the prediction of pharmacokinetic properties of drugs and the impact of drug-drug interactions. We developed a new PET probe, sodium (3R, 5R)-3, 5-dihydroxy-7-((1S, 2S, 6S, 8S)-6-hydroxy-2-methyl-8- ((1-[11C]-(E)-2-methyl-but-2-enoyl) oxy) -1, 2, 6, 7, 8, 8a-hexahydronaphthalen-1-yl) heptanoate ([11C]DPV), and demonstrated its usefulness for the quantitative investigation of Oatps (gene symbol SLCO) and Mrp2 (gene symbol ABCC2) in rats. To further analyze the species differences and verify the pharmacokinetic parameters in humans, serial PET scanning of the abdominal region with [11C]DPV was performed in six healthy volunteers with and without an OATP1Bs and MRP2 inhibitor, rifampicin (600 mg, oral), in a crossover fashion. After intravenous injection, [11C]DPV rapidly distributed to the liver and kidney followed by secretion into the bile and urine. Rifampicin significantly reduced the liver distribution of [11C]DPV 3-fold, resulting in a 7.5-fold reduced amount of excretion into the bile and the delayed elimination of [11C]DPV from the blood circulation. The hepatic uptake clearance (CLuptake, liver) and canalicular efflux clearance (CLint, bile) of [11C]DPV (544 ± 204 and 10.2 ± 3.5 µl/min per gram liver, respectively) in humans were lower than the previously reported corresponding parameters in rats (1800 and 298 µl/min per gram liver, respectively) (Shingaki et al., 2013). Furthermore, rifampicin treatment significantly reduced CLuptake, liver and CLint, bile by 58% and 44%, respectively. These results suggest that PET imaging with [11C]DPV is an effective tool for quantitatively characterizing the OATP1Bs and MRP2 functions in the human hepatobiliary transport system.