Search Results (90)

Background: Baicalin (BG) has been used in the treatment of many diseases. However, the effect of hepatic insufficiency on its pharmacokinetics has not been reported, and there is a lack of clinical guidance for the use of BG in patients with hepatic impairment. Methods: Carbon tetrachloride (CCl₄)-induced rat models were used to simulate hepatic failure patients to assess the effect of hepatic impairment on the pharmacokinetics and distribution of BG. In vitro metabolism and transporter studies were employed to elucidate the potential mechanisms. Results: After intragastric administration of 10 mg/kg of BG, the peak plasma concentration and exposure (AUC_0–t) of BG decreased by 64.6% and 52.6%, respectively, in CCl₄-induced rats. After intravenous administration, the AUC_0–t decreased by 73.6%, and unlike in the control group, the second absorption peak of BG was not obvious in the concentration–time curve of CCl₄-induced rats. The cumulative excretion of BG in the feces increased, but that in the bile decreased. In vivo data indicated that the absorption and enterohepatic circulation of BG were affected. In vitro studies found that the hydrolysis of BG to the aglycone baicalein decreased significantly in the intestinal tissues and contents of the CCl₄-induced rats. And BG was identified as a substrate for multiple efflux and uptake transporters, such as breast cancer resistance protein (BCRP) and multidrug resistance-associated proteins (MRPs), organic anion transporting polypeptides (OATP1B1, 1B3, 2B1), and organic anion transporters (OATs). The bile acids accumulated by liver injury inhibited the uptake of BG by OATPs, especially that by OATP2B1. Conclusions: Hepatic impairment reduced BG hydrolysis by intestinal microflora and inhibited its transporter-mediated biliary excretion, which synergistically led to the attenuation of the enterohepatic circulation of BG, which altered its pharmacokinetics. Full article

Organic anion transporting polypeptide 1B1 (OATP1B1) is selectively expressed at the basolateral membrane of human hepatocytes and plays a crucial role in the absorption of various xenobiotic compounds, including many important clinical drugs. Oligomerization with regulatory proteins is a common mechanism for regulating membrane protein functions. In the present study, we found that knocking down the scaffold protein radixin, which is the major member of the ERM family expressed in the liver, significantly enhanced the uptake function of OATP1B1. On the other hand, the overexpression of the phospho-mimic form of radixin (radixin-D) reduced the uptake function and cell surface level of OATP1B1, while the wild-type and phospho-dormant form of radixin (radixin-A) did not exhibit the same effect. Further investigation revealed that radixin interacts with OATP1B1. Activation of protein kinase C (PKC), which our previous study showed accelerates the internalization of OATP1B1, was found to increase the phosphorylation level of radixin associated with OATP1B1. The knockdown of radixin significantly diminished the suppressive effect of PKC on the function and cell surface levels of OATP1B1. These results suggested that OATP1B1 forms complexes with radixin, which may be phosphorylated by PKC, leading to reduced cell surface expression and activity of the transporter. Full article

S-nitrosoglutathione (GSNO) is the S-nitrosated derivative of glutathione (GSH). GSNO is an endogenous class of NO donors and a natural NO depot in biological systems. Organic anion transporting polypeptide 1B1 (OATP1B1) is an influx transporter that is expressed in the liver. OATP1B1 plays an important role in the transport of endogenous and exogenous substances. Various pathways for the regulation of OATP1B1 have been described. In the present study, the involvement of OATP1B1 in GSNO transport and the regulation of OATP1B1 by GSNO was examined. For HEK293-OATP1B1, it has been shown that GSNO is not a substrate of OATP1B1, but OATP1B1 can participate in the transport of GSH across the cell membrane. GSNO at concentrations of 1–100 μM and exposure for 3 h do not affect the expression and activity of OATP1B1, but exposure for 24 and 72 h stimulates the expression of the SLCO1B1 gene, OATP1B1, and transporter activity. Up-regulation of OATP1B1 by GSNO is carried out through the NO-cGMP signaling pathway, Nrf2, and LXRa. Full article

Background: It has been documented that radiation can influence the pharmacokinetics of chemotherapy drugs, yet the underlying mechanisms remain poorly understood. In clinical practice, a considerable number of cancer patients undergo radiotherapy, and those with comorbid hypertension required antihypertensive drugs, including valsartan, an angiotensin II receptor blocker. However, there is no research investigating whether radiotherapy poses a risk of altering the pharmacokinetics. Objective: The objective of this study is to investigate the impact of X-ray abdominal irradiation on the pharmacokinetics of valsartan and to preliminarily elucidate the underlying mechanism. Methods: The pharmacokinetics of valsartan after X-ray irradiation was investigated in rats and in vitro by detecting the concentration of valsartan in biological samples by LC-MS/MS. The oxidative stress in the intestine and the mRNA expression of partial transporters and Nrf2 in the liver and small intestine were detected by biochemical reagent kit or RT-qPCR. Results: In vivo studies showed that X-ray irradiation resulted in a significant decrease in the AUC and C_max of valsartan, and the cumulative fractional excretion of valsartan in bile and urine, although there was no significant change in fecal excretion. In vitro studies showed that the uptake of valsartan by both intestine and Caco-2 cells decreased after irradiation, and the cellular uptake could be restored by Mrp2 inhibitor MK571. The levels of GSH, SOD, and CAT in the intestine decreased after irradiation. The mRNA expressions of Mrp2 and P-gp in the intestine or Caco-2 cells were significantly upregulated after irradiation while there was a downregulation of Mrp2 and oatp1b2 in liver. Nrf2 and HO-1 in the intestine were also significantly upregulated, which clarified the involvement of Mrp2 and the possible molecular mechanism. Conclusions: Abdominal X-ray irradiation can cause oxidative stress and upregulate intestinal Mrp2, which may be related to oxidative stress and upregulation of Nrf2, reducing intestinal absorption of valsartan and leading to a significant decrease in the blood concentration of valsartan. Full article

Background: Hepatitis D virus (HDV) is a defective virus requiring co-infection with hepatitis B virus (HBV) to replicate, occurring in 5% of HBV+ patients. Bulevirtide (BLV) is now the first-in-class specific anti-HDV agent, inhibiting HDV binding to NTCP, with good tolerability and good virological and biochemical response rates. Currently, little is known about its pharmacokinetic/pharmacodynamic (PK/PD), as well as potential drug-drug interaction (DDI) profile. In this work we provide a systematic review of the current knowledge on these aspects. Methods: A literature review of PK, PD and DDI profiles of BLV was conducted from Pubmed and EMA websites. Experimentally tested interactions and hypothetical mechanisms of interaction were evaluated, mostly focusing on usually co-administered anti-infective agents and other drugs interacting on NTCP. Results: BLV shows non-linear PK, due to target-mediated drug disposition, so its PK as well as PD is expected to be influenced by interactions of other drugs with NTCP, while it is not substrate of CYPs and ABC transporters. In-vivo investigated DDIs showed no clinically relevant interactions, but a weak inhibitory effect was suggested on CYP3A4 in a work when used at high doses (10 mg instead of 2 mg). In vitro, a weak inhibitory effect on OATP transporters was observed, but at much higher concentrations than the ones expected in vivo. Conclusions: The drug-drug interaction potential of BLV can be considered generally very low, particularly at the currently approved dose of 2 mg/day. Some attention should be paid to the coadministration of drugs with known binding and/or inhibition of NTCP. Full article

Background/Objectives: Bempedoic acid (BA) is a novel cholesterol-lowering agent with proven positive effects on cardiovascular endpoints. Because it is an inhibitor of the hepatic transporters OATP1B1 and OATP1B3, two uptake transporters regulating the intrahepatic availability of statins, it increases the systemic exposure of co-administered statins. This interaction could raise the risk of myopathy. We hypothesized that the drug interaction between BA and statins could be mitigated by staggered administration. Methods: This was a single-centre, open-label, randomized, two-arm, cross-over, phase I drug interaction trial in healthy volunteers (EudraCT-No: 2022-001096-13). The primary objective was to evaluate the OATP1B1 inhibitory effect of BA on exposure to pravastatin after simultaneous administration versus different schedules of staggered administration. A secondary objective was to evaluate the impact of SLCO1B1 genotypes (*1, *5, *15, *37) on pravastatin exposure. Pravastatin was administered in single oral doses of 40 mg at six visits. After a baseline visit with pravastatin alone, BA was dosed to steady state at the approved oral dose of 180 mg. Outcome measures were the area under the plasma concentration–time curve, extrapolated to infinity (AUC_∞) and C_max of pravastatin, 3α-hydroxy-pravastatin (pravastatin 3-iso), and pravastatin lactone, and their geometric mean ratios (GMRs) of different schedules of administration. Log-transformed AUC_∞ and C_max were compared with one-way ANOVA with a 90% confidence interval (CI). Results: Fourteen participants completed all visits. At BA steady state, the GMRs of pravastatin AUC_∞ and C_max were 1.80 (90% CI 1.31–2.46) and 1.95 (90% CI 1.40–2.72), respectively, compared to baseline. There was no significant difference in pravastatin exposure between simultaneous vs. staggered administration. There was no statistically significant difference in pravastatin 3-iso or pravastatin lactone between different administration modes. For the AUC_∞ of pravastatin and pravastatin 3-iso, haplotype was a significant source of variation (63% and 20%, respectively), while the type of administration (simultaneous vs. staggered) had no significant impact. Conclusions: The increase in pravastatin exposure with concomitant intake of BA was larger than expected. There was no significant difference between simultaneous vs. staggered administration of pravastatin and BA, possibly due to a population that was heterogenous in SLCO1B1 haplotypes. Full article

The involvement of drug-metabolizing enzymes and transporters in plasma clozapine (CLZ) dynamics has not been well examined in Japanese patients with treatment-resistant schizophrenia (TRS). Therefore, this clinical study investigated the relationship between single nucleotide polymorphisms (SNPs) of various pharmacokinetic factors (drug-metabolizing enzymes and transporters) and dynamic changes in CLZ. Additionally, we aimed to determine whether CLZ acts as a substrate for pharmacokinetic factors using in vitro assays and molecular docking calculations. We found that 6 out of 10 patients with TRS and with multiple organic anion transporting polypeptide (OATP) variants (OATP1B1: *1b, *15; OATP1B3: 334T>G, 699G>A; and OATP2B1: *3, 935G>A, 601G>A, 76_84del) seemed to be highly exposed to CLZ and/or N-desmethyl CLZ. A CLZ uptake study using OATP-expressing HEK293 cells showed that CLZ was a substrate of OATP1B1 with K_m and V_max values of 38.9 µM and 2752 pmol/mg protein/10 min, respectively. The results of molecular docking calculations supported the differences in CLZ uptake among OATP molecules and the weak inhibitory effect of cyclosporine A, which is a strong inhibitor of OATPs, on CLZ uptake via OATP1B1. This is the first study to show that CLZ is an OATP1B1 substrate and that the presence of SNPs in OATPs potentially alters CLZ pharmacokinetic parameters. Full article

Δ⁹-Tetrahydrocannabinol (THC) is the primary psychoactive component of cannabis which is being increasingly consumed by pregnant people. In humans, THC is sequentially metabolized in the liver to its circulating metabolites 11-hydroxy-THC (11-OH-THC, psychoactive) and 11-nor-9-carboxy-THC (THC-COOH, non-psychoactive). Human and macaque data show that fetal exposure to THC is considerably lower than the corresponding maternal exposure. Through perfused human placenta studies, we showed that this is due to the active efflux of THC (fetal-to-maternal) by a placental transporter(s) other than P-glycoprotein or breast cancer resistance protein. The identity of this placental transporter(s) as well as whether THC or its metabolites are substrates or inhibitors of hepatic solute carrier transporters is unknown. Therefore, we investigated whether 5 μM THC, 0.3 μM 11-OH-THC, and 2.5 μM THC-COOH are substrates and/or inhibitors of placental or hepatic solute carrier transporters at their pharmacologically relevant concentrations. Using HEK cells overexpressing human OATP1B1, OATP1B3, OATP2B1, OCT1, OCT3, OAT2, OAT4, or NTCP, and prototypic substrates/inhibitors of these transporters, we found that THC and THC-COOH were substrates but not inhibitors of OCT1. THC-COOH was a weak substrate of OCT3 and a weak inhibitor of OAT4. THC, 11-OH-THC, and THC-COOH were found not to be substrates/inhibitors of the remaining transporters investigated. Full article

Bempedoic acid is a new drug that improves the control of cholesterol levels, either as monotherapy or in combination with existing lipid-lowering therapies, and shows clinical efficacy in cardiovascular disease patients. Thus, patients with comorbidities and under multiple therapies may be eligible for bempedoic acid, thus facing the potential problem of drug–drug interactions (DDIs). Bempedoic acid is a prodrug administered orally at a fixed daily dose of 180 mg. The dicarboxylic acid is enzymatically activated by conjugation with coenzyme A (CoA) to form the pharmacologically active thioester (bempedoic acid–CoA). This process is catalyzed by very-long-chain acyl-CoA synthetase 1 (ACSVL1), expressed almost exclusively at the hepatic level. Bempedoic acid–CoA is a potent and selective inhibitor of ATP citrate lyase (ACL), a key enzyme in the biosynthetic pathway of cholesterol and fatty acids. The drug reduces low-density lipoprotein–cholesterol (LDL-C) (20–25%), non-high-density lipoprotein–cholesterol (HDL-C) (19%), apolipoprotein B (apoB) (15%), and total cholesterol (16%) in patients with hypercholesterolemia or mixed dyslipidemia. The drug has a favorable pharmacokinetics profile. Bempedoic acid and its metabolites are not substrates or inhibitors/inducers of cytochrome P450 (CYP450) involved in drug metabolism. On the other hand, bempedoic acid–glucuronide is a substrate for organic anion transporter 3 (OAT3). Bempedoic acid and its glucuronide are weak inhibitors of the OAT2, OAT3, and organic anion-transporting polypeptide 1B1 (OATP1B1) and 1B3 (OATP1B3). Thus, bempedoic acid could inhibit (perpetrator) the hepatic uptake of OATP1B1/3 substrate drugs and the renal elimination of OAT2 and OAT3 substrates and could suffer (victim) the effect of OAT3 transporter inhibitors, reducing its renal elimination. Based on these pharmacological characteristics, here, we describe the potential DDIs of bempedoic acid with concomitant medications and the possible clinical implications. Full article

Background/Objectives: One of the major risks associated with the concomitant use of herbal products and therapeutic drugs is herb–drug interactions (HDIs). The most common mechanism leading to HDIs is the inhibition and/or induction of transport proteins and drug-metabolizing enzymes by herbal ingredients, causing changes in the pharmacokinetic disposition of the victim drug. The present study aimed to determine the potential interactions of Uncaria tomentosa (UT) (cat’s claw), a popular herb due to its supposed health benefits. Methods: The effect of UT extract and its major oxindole alkaloids was investigated on multispecific solute carrier (SLC) and ATP-binding cassette (ABC) drug transporters, using SLC transporter-overexpressing cell lines and vesicles prepared from ABC transporter-overexpressing cells. Results: UT extract significantly inhibited all ABC transporters and the majority of the SLC transporters tested. Of the investigated oxindole alkaloids, isopteropodine significantly inhibited OATP, OCT1 and OCT2, OAT3, ENT4, MDR1, and BCRP transporters. OCTs, OCTN1-, ENT1-, and MDR1-mediated substrate accumulation was below 50% in the presence of mitraphylline. Conclusions: Based on the calculated intestinal concentration of UT extract, interactions with intestinal transporters, especially OATP2B1, ENTs, MRP1, MRP2, MDR1, and BCRP could be relevant in vivo. Our data can help to predict the clinical consequences of UT co-administration with drugs, such as increased toxicity or altered efficacy. In conclusion, the use of these in vitro models is applicable for the analysis of transporter-mediated HDIs similar to drug–drug interaction (DDI) prediction. Full article

Background/Objectives: YAT2150 is a first-in-class antiplasmodial compound that has been recently proposed as a new interesting drug for malaria therapy. Methods/Results: The fluorescence of YAT2150 rapidly increases upon its entry into Plasmodium, a property that can be of use for the design of highly sensitive diagnostic approaches. YAT2150 blocks the in vitro development of the ookinete stage of Plasmodium and, when added to an infected blood meal, inhibits oocyst formation in the mosquito. Thus, the compound could possibly contribute to future transmission-blocking antimalarial strategies. Cell influx/efflux studies in Caco-2 cells suggest that YAT2150 is internalized by endocytosis and also through the OATP2B1 transporter, whereas its main export route would be via OSTα. YAT2150 has an overall favorable drug metabolism and pharmacokinetics profile, and its moderate cytotoxicity can be significantly reduced upon encapsulation in immunoliposomes, which leads to a dramatic increase in the drug selectivity index to values close to 1000. Although YAT2150 binds amyloid-forming peptides, its in vitro fluorescence emission is stronger upon association with peptides that form amorphous aggregates, suggesting that regions enriched in unstructured proteins are the preferential binding sites of the drug inside Plasmodium cells. The reduction of protein aggregation in the parasite after YAT2150 treatment, which has been suggested to be directly related to the drug’s mode of action, is also observed following treatment with quinoline antimalarials like chloroquine and primaquine. Conclusions: Altogether, the data presented here indicate that YAT2150 can represent the spearhead of a new family of compounds for malaria diagnosis and therapy due to its presumed novel mode of action based on the interaction with functional protein aggregates in the pathogen. Full article

Taurine can ameliorate hypercholesterolemia by facilitating cholesterol efflux and increasing cytochrome P450 7A1 (CYP7A1) without clear underlying molecular mechanisms. This study aims to elucidate the molecular action of taurine in diet-induced hypercholesterolemia. Male Wistar rats were fed a high cholesterol diet containing 5% taurine for 14 days. Three-dimensional primary hepatocytes from rats were exposed to 10 mM taurine for 24 h. Transcriptome analyses of both the liver and hepatocytes were performed using DNA microarray. Taurine significantly decreased serum cholesterol levels and increased hepatic CYP7A1 mRNA levels and transcription rates in rats. Taurine altered the expression of seventy-seven genes in the liver, involving lipid, drug, amino acid metabolism, and gluconeogenesis pathways. The small heterodimer partner (SHP), a transcription factor regulated by taurine, was suppressed. “Network analysis” revealed a negative correlation between the SHP and induction of CYP7A1 and cytochrome P450 8B1 (CYP8B1). However, CYP7A1 and CYP8B1 levels were not altered by taurine in 3D-primary hepatocytes. Venn diagram analyses of the transcriptomes in both hepatocytes and the liver indicated a consistent upregulation of organic anion transporting polypeptide 2 (OATP2) and betaine homocysteine methyltransferase (BHMT). Taurine ameliorated hypercholesterolemia in rats fed a high cholesterol diet by directly enhancing the hepatic expression of BHMT and OATP2, which modulated the SHP and induced CYP7A1 and CYP8B1, thereby promoting cholesterol catabolism and lowering blood cholesterol levels. Full article

Of the 450 cell membrane transporters responsible for shuttling substrates, nutrients, hormones, neurotransmitters, antioxidants, and signaling molecules, approximately nine are associated with clinically relevant drug–drug interactions (DDIs) due to their role in drug and metabolite transport. Therefore, a clinical study evaluating potential transporter DDIs is recommended if an investigational product is intestinally absorbed, undergoes renal or hepatic elimination, or is suspected to either be a transporter substrate or perpetrator. However, many of the transporter substrates and inhibitors administered during a DDI study also affect cytochrome P450 (CYP) activity, which can complicate data interpretation. To overcome these challenges, the assessment of endogenous biomarkers can help elucidate the mechanism of complex DDIs when multiple transporters or CYPs may be involved. This perspective article will highlight how creative study designs are currently being utilized to address complex transporter DDIs and the role of physiology-based -pharmacokinetic (PBPK) models can play. Full article

Expression of the breast cancer resistance protein (BCRP/ABCG2) transporter is downregulated in placentas from women with preeclampsia (PE) and in an immunological rat model of PE. While many drugs are substrates of this important efflux transporter, the impact of PE associated BCRP downregulation on maternal and fetal drug exposure has not been investigated. Using the PE rat model, we performed a pharmacokinetic study with rosuvastatin (RSV), a BCRP substrate, to investigate this impact. PE was induced in rats during gestational days (GD) 13 to 16 with daily low-dose endotoxin. On GD18, RSV (3 mg/kg) was administrated intravenously, and rats were sacrificed at time intervals between 0.5 and 6 h. As compared to controls, placental expression of Bcrp and Oatp2b1 significantly decreased in PE rats. A corresponding increase in RSV levels was seen in fetal tissues and amniotic fluid of the PE group (p < 0.05), while maternal plasma concentrations remained unchanged from the controls. An increase in Bcrp expression and decreased RSV concentration were seen in the livers of PE dams. This suggests that PE-mediated transporter dysregulation leads to significant changes in the maternal and fetal RSV disposition. Overall, our findings demonstrate that altered placental expression of transporters in PE can increase fetal accumulation of their substrates. Full article

Zastaprazan (JP-1366), a novel potassium-competitive acid blocker, is a new drug for the treatment of erosive esophagitis. JP-1366 is highly metabolized in human, mouse, and dog hepatocytes but moderately metabolized in rat and monkey hepatocytes when estimated from the metabolic stability of this compound in hepatocyte suspension and when 18 phase I metabolites and 5 phase II metabolites [i.e., N-dearylation (M6), hydroxylation (M1, M19, M21), dihydroxylation (M7, M8, M14, M22), trihydroxylation (M13, M18), hydroxylation and reduction (M20), dihydroxylation and reduction (M9, M16), hydrolysis (M23), hydroxylation and glucuronidation (M11, M15), hydroxylation and sulfation (M17), dihydroxylation and sulfation (M10, M12), N-dearylation and hydroxylation (M3, M4), N-dearylation and dihydroxylation (M5), and N-dearylation and trihydroxylation (M2)] were identified from JP-1366 incubation with the hepatocytes from humans, mice, rats, dogs, and monkeys. Based on the cytochrome P450 (CYP) screening test and immune-inhibition analysis with CYP antibodies, CYP3A4 and CYP3A5 played major roles in the metabolism of JP-1366 to M1, M3, M4, M6, M8, M9, M13, M14, M16, M18, M19, M21, and M22. CYP1A2, 2C8, 2C9, 2C19, and 2D6 played minor roles in the metabolism of JP-1366. UDP-glucuronosyltransferase (UGT) 2B7 and UGT2B17 were responsible for the glucuronidation of M1 to M15. However, JP-1366 and active metabolite M1 were not substrates for drug transporters such as organic cation transporter (OCT) 1/2, organic anion transporter (OAT) 1/3, organic anion transporting polypeptide (OATP)1B1/1B3, multidrug and toxic compound extrusion (MATE)1/2K, P-glycoprotein (P-gp), and breast cancer-resistant protein (BCRP). Only M1 showed substrate specificity for P-gp. The findings indicated that drug-metabolizing enzymes, particularly CYP3A4/3A5, may have a significant role in determining the pharmacokinetics of zastaprazan while drug transporters may only have a small impact on the absorption, distribution, and excretion of this compound. Full article