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Rosiglitazone is an activator of nuclear peroxisome proliferator-activated (PPAR) receptor gamma used in the treatment of type 2 diabetes mellitus. The elimination of rosiglitazone occurs mainly via metabolism, with major contribution by enzyme cytochrome P450 (CYP) 2C8. Primary routes of rosiglitazone metabolism are N-demethylation and hydroxylation. Modulation of CYP2C8 activity by co-administered drugs lead to prominent changes in the exposure of rosiglitazone and its metabolites. Here, we attempt to develop mechanistic parent-metabolite physiologically based pharmacokinetic (PBPK) model for rosiglitazone. Our goal is to predict potential drug-drug interaction (DDI) and consequent changes in metabolite N-desmethyl rosiglitazone exposure. The PBPK modeling was performed in the PKSim® software using clinical pharmacokinetics data from literature. The contribution to N-desmethyl rosiglitazone formation by CYP2C8 was delineated using vitro metabolite formation rates from recombinant enzyme system. Developed model was verified for prediction of rosiglitazone DDI potential and its metabolite exposure based on observed clinical DDI studies. Developed model exhibited good predictive performance both for rosiglitazone and N-desmethyl rosiglitazone respectively, evaluated based on commonly acceptable criteria. In conclusion, developed model helps with prediction of CYP2C8 DDI using rosiglitazone as a substrate, as well as changes in metabolite exposure. In vitro data for metabolite formation can be successfully utilized to translate to in vivo conditions.

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Introduction: Initiating favipiravir in COVID-19 patients with long-term warfarin use can lead to increased INR. However, data on the onset and duration of the increasing INR are limited. Method: We reviewed patient charts to include COVID-19 adult patients who received favipiravir for at least 5 days and used warfarin at the same dose for at least 12 weeks. Data on demographics, comorbidities, other medical characteristics, international normalized ratio (INR), and signs of bleeding were collected. Result: Eight patients, with a mean age of 70.88 ± 8.49 years old, received the standard dose of favipiravir. The mean maximum INR (4.30 ± 1.26) was statistically different from the baseline INR (P = .00029) and the change was observed within 4.38 ± 1.99 days after initiating favipiravir. Warfarin was then discontinued without favipiravir discontinuation in most patients, allowing the INR to gradually decrease within 2 to 3 days. Conclusion: Concurrent use of favipiravir and warfarin led to INR prolongation within approximately 4 days. The effect of such interaction can be acute as the prolongation occurred within 1 day in 1 of the patients.

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A ligand-accessible space in the CYP2C8 active site was reconstituted as a fused grid-based Template∗ with the use of structural data of the ligands. An evaluation system of CYP2C8-mediated metabolism has been developed on Template with the introduction of the idea of Trigger-residue initiated ligand-movement and fastening. Reciprocal comparison of the data of simulation on Template with experimental results suggested a unified way of the interaction of CYP2C8 and its ligands through the simultaneous plural-contact with Rear-wall of Template. CYP2C8 was expected to have a room for ligands between vertically standing parallel walls termed Facial-wall and Rear-wall. Both the walls were separated by a distance corresponding to 1.5-Ring (grid) diameter size, which was termed Width-gauge. The ligand sittings were stabilized through contacts with Facial-wall and the left-side borders of Template including specific Position 29, left-side border of Rings I/J, or Left-end, after Trigger-residue initiated ligand-movement. Trigger-residue movement is suggested to force ligands to stay firmly in the active site and then to initiate CYP2C8 reactions. Simulation experiments for over 350 reactions of CYP2C8 ligands supported the system established.

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Background: Cervical cancer (CC) is currently the most common malignant tumour in the female reproductive tract, and paclitaxel (PTX) is a commonly used chemotherapeutic agent, but tumour cell resistance will seriously affect the therapeutic efficacy of PTX. Nanoparticle human serum albumin-bound paclitaxel (Nano-HSA-PTX) is a novel drug delivery modality that may have superior effects to PTX alone. Objective: To clarify the effect of Nano-HSA-PTX on cervical carcinoma (CC) cells and the underlying mechanisms. Methods: After the preparation of Nano-HSA-PTX, its morphology was observed by electron transmission microscope (TEM), and its entrapment efficiency (EE%) and drug loading rate (DL%) were detected. Nano-HSA-PTX was compared with conventional PTX for drug metabolism. Additionally, CC HeLa and SiHa cells were purchased and divided into three groups to treat with Nano-HSA-PTX, PTX and normal saline, respectively. MTT, cell cloning, Transwell and cell scratch assays were carried out to determine cell proliferation, invasion and migration, flow cytometry and Western blotting were performed to detect apoptosis rate and apoptosis-related protein expression, and PCR was conducted to quantify oxidative damage indicators. Further, CYP3A4 and CYP2C8 expression patterns in CC cells (HeLa and SiHa) and human normal cervical epithelia (End1/E6E7) and the changes of their levels under the intervention of Nano-HSA-PTX were measured. Subsequently, C57BL/6mice were purchased for subcutaneous tumorigenesis experiment to observe the impact of Nano-HSA-PTX on tumor growth. Results: Under TEM, Nano-HSA-PTX was complete and arranged compactly, with a stable structure and markedly higher EE% and DL% than PTX (P < 0.05). Under Nano-HSA-PTX intervention, the proliferation, invasion, migration and oxidative damage of HeLa and SiHa were significantly decreased compared with the control and PTX groups, while the apoptosis was increased (P < 0.05). Besides, elevated CYP3A4 and CYP2C8 levels were observed in CC cells, which were inhibited by Nano-HSA-PTX and PTX (P < 0.05). Finally, tumorigenesis experiments in nude mice revealed that Nano-HSA-PTX could inhibit tumor growth. Conclusion: Compared with PTX, Nano-HSA-PTX has a superior effect of inhibiting CC activity. And this mechanism of action was carried out by inhibiting the expression of CYP3A4 and CYP2C8.

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Resistance to anticancer agents is a major obstacle to efficacious tumour therapy and responsible for high cancer-related mortality rates. Some resistance mechanisms are associated with pharmacokinetic variability in anticancer drug exposure due to genetic polymorphisms of drug-metabolizing cytochrome P450 (CYP) enzymes, whereas variations in tumoural metabolism as a consequence of CYP copy number alterations are assumed to contribute to the selection of resistant cells. A high-throughput quantitative polymerase chain reaction (qPCR)-based method was developed for detection of CYP copy number alterations in tumours, and a scoring system improved the identification of inappropriate reference genes that underwent deletion/multiplication in tumours. The copy numbers of both the target (CYP2C8, CYP3A4) and the reference genes (ALB, B2M, BCKDHA, F5, CD36, MPO, TBP, RPPH1) established in primary lung adenocarcinoma by the qPCR-based method were congruent with those determined by next-generation sequencing (for 10 genes, slope = 0.9498, r2 = 0.72). In treatment naïve adenocarcinoma samples, the copy number multiplication of paclitaxel-metabolizing CYP2C8 and/or CYP3A4 was more prevalent in non-responder patients with progressive disease/exit than in responders with complete remission. The high-throughput qPCR-based method can become an alternative approach to next-generation sequencing in routine clinical practice, and identification of altered CYP copy numbers may provide a promising biomarker for therapy-resistant tumours.

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Following the publication of the above article, an interested reader drew to the authors' attention that, for the cell migration assay experiments shown in Fig. 5 on p. 731, the 'TNF­α' data panels in Fig. 5A and C appeared to be matching, where experiments performed under different conditions were intended to have been displayed. After having re­examined their original data, the authors have realized that the data files were mislabelled, although they were able to retrieve the correct data for Fig. 5C (where the error occurred). The revised version of Fig. 5, containing the correct data for the TNF­α experiment shown in Fig. 5C, is shown on the next page. Note that the error made during the assembly of this figure did not affect the overall conclusions reported in the paper. All the authors agree with the publication of this corrigendum, and are grateful to the Editor of International Journal of Molecular Medicine for allowing them the opportunity to publish this. They also apologize to the readership for any inconvenience caused. [International Journal of Molecular Medicine 34: 725­732, 2014; DOI: 10.3892/ijmm.2014.1844].

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In spite of unprecedented advances in modern cancer therapy, there is still a dearth of targeted therapy to circumvent triple-negative breast cancer (TNBC). Paclitaxel is the front-line therapy against TNBC, but the main constraints of its treatment are dose-related adverse effects and emerging chemoresistance. In this context, glabridin (phytoconstituent from Glycyrrhiza glabra) is reported to hit multiple signalling pathways at the in-vitro level, but hardly any information is known at the in-vivo level. We aimed here to elucidate glabridin potential with an underlying mechanism in combination with a low dose of paclitaxel using a highly aggressive mouse mammary carcinoma model. Glabridin potentiated the anti-metastatic efficacy of paclitaxel by substantially curtailing tumor burden and diminishing lung nodule formation. Moreover, glabridin remarkably attenuated epithelial-mesenchymal transition (EMT) traits of hostile cancer cells via up-regulating (E-cadherin & occludin) and down-regulating (Vimentin & Zeb1) vital EMT markers. Besides, glabridin amplified apoptotic induction effect of paclitaxel in tumor tissue by declining or elevating pro-apoptotic (Procaspase-9 or Cleaved Caspase-9 & Bax) and reducing anti-apoptotic (Bcl-2) markers. Additionally, concomitant treatment of glabridin and paclitaxel predominantly lessened CYP2J2 expression with marked lowering of epoxyeicosatrienoic acid (EET)'s levels in tumor tissue to reinforce the anti-tumor impact. Simultaneous administration of glabridin with paclitaxel notably enhanced plasma exposure and delayed clearance of paclitaxel, which was mainly arbitrated by CYP2C8-mediated slowdown of paclitaxel metabolism in the liver. The fact of intense CYP2C8 inhibitory action of glabridin was also ascertained using human liver microsomes. Concisely, glabridin plays a dual role in boosting anti-metastatic activity by augmenting paclitaxel exposure via CYP2C8 inhibition-mediated delaying paclitaxel metabolism and limiting tumorigenesis via CYP2J2 inhibition-mediated restricting EETs level. Considering the safety, reported protective efficacy, and the current study results of boosted anti-metastatic effects, further investigations are warranted as a promising neoadjuvant therapy for crux paclitaxel chemoresistance and cancer recurrence.

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CYP2C8 is a crucial CYP isoform responsible for the metabolism of xenobiotics and endogenous molecules. CYP2C8 converts arachidonic acid to epoxyeicosatrienoic acids (EETs) that cause cancer progression. Rottlerin possess significant anticancer actions. However, information on its CYP inhibitory action is lacking in the literature and therefore, we aimed to explore the same using in silico, in vitro, and in vivo approaches. Rottlerin showed highly potent and selective CYP2C8 inhibition (IC50 < 0.1 µM) compared to negligible inhibition (IC50 > 10 µM) for seven other experimental CYPs in human liver microsomes (HLM) (in vitro) using USFDA recommended index reactions. Mechanistic studies reveal that rottlerin could reversibly (mixed-type) block CYP2C8. Molecular docking (in silico) results indicate a strong interaction could occur between rottlerin and the active site of human CYP2C8. Rottlerin boosted the plasma exposure of repaglinide and paclitaxel (CYP2C8 substrates) by delaying their metabolism using the rat model (in vivo). Multiple-dose treatment of rottlerin with CYP2C8 substrates lowered the CYP2C8 protein expression and up-regulated & down-regulated the mRNA for CYP2C12 & CYP2C11 (rat homologs), respectively, in rat liver tissue. Rottlerin substantially hindered the EET formation in HLM. Overall results of rottlerin on CYP2C8 inhibition and EET formation insinuate further exploration for cancer therapy.

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PURPOSE: Many studies have shown that cytochrome P450 (CYP) gene polymorphisms are usually associated with an increased risk of cardiovascular and cerebrovascular diseases. To explore the association of CYP2C8 and CYP2J2 gene polymorphisms with hypertensive intracerebral hemorrhage (HICH) in the Han Chinese population. METHODS: Forty HICH patients and 40 control subjects were recruited for this study. Two single nucleotide polymorphisms (SNP) (rs1058932, rs2275622) in the CYP2C8 gene and two SNPs (rs2271800, rs1155002) in the CYP2J2 gene were selected for genotyping by direct sequencing. Statistical analysis was applied to examine the effect of genetic variation on HICH. RESULTS: We found that variant alleles of CYP2C8 rs1058932 (A) and rs2275622 (C) were both significantly associated with HICH, especially in females. We also found significant associations of CYP2C8 rs1058932 (A) and rs2275622 (C) variant alleles with poor outcomes in HICH patients, especially in males. CONCLUSIONS: CYP2C8 gene polymorphisms might increase the risk of HICH in the Han Chinese population and might lead to poor outcomes. This finding adds to the body of literature supporting novel therapeutic strategies for HICH.

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AIMS: Patients on treatment with oral fixed dose imatinib are frequently under- or overexposed to the drug. We investigated the association between the gene activity score (GAS) of imatinib-metabolizing cytochromes (CYP3A4, CYP3A5, CYP2D6, CYP2C9, CYP2C19, CYP2C8) and imatinib and nor-imatinib exposure. We also investigated the impact of concurrent drug-drug-interactions (DDIs) on the association between GAS and imatinib exposure. METHODS: Serial plasma samples were collected from 33 GIST patients treated with imatinib 400 mg daily within a prospective clinical trial. Imatinib and nor-imatinib Ctrough were quantified by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Genetic polymorphisms with a functional impact on imatinib-metabolizing cytochromes were identified and a GAS was calculated for each gene. A DDI-adjusted GAS was also generated. RESULTS: Imatinib and nor-imatinib Ctrough were measured in 161 plasma samples. CYP2D6 GAS and metabolizer status based on genotype were associated with imatinib and (imatinib + nor-imatinib) Ctrough . CYP2D6 poor and intermediate metabolizers were predicted to have a lower nor-imatinib/imatinib metabolic ratio than normal metabolizers (0.197 and 0.193 vs. 0.247, P = .0205), whereas CYP2C8*3 carriers had a higher ratio than CYP2C8*1/*1 patients (0.263 vs. 0.201, P = .0220). CYP2C9 metabolizer status was inversely related to the metabolic ratio with an effect probably driven by the linkage disequilibrium between CYP2C9*2 and CYP2C8*3. The CYP2D6 DDI-adjusted GAS was still predictive of imatinib exposure. CONCLUSIONS: These findings highlight that CYP2D6 plays a major role in imatinib pharmacokinetics, but other players (i.e., CYP2C8) may influence imatinib exposure. These findings could drive the selection of patients more susceptible to imatinib under- or overexposure who could be candidates for personalized treatment and intensified monitoring strategies.

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Background: Bladder cancer is the most common leading cause of mortality around the world. Previous studies have indicated that genetic factors are significantly associated with bladder cancer progression-for instance, the CYP2C8 gene is involved in bladder cancer progression. However, little is known about the impact of CYP2C8 genetic polymorphisms on bladder cancer risk. We aimed to detect the association between CYP2C8 variations and bladder cancer susceptibility. Methods: This study included 550 healthy subjects and 217 bladder cancer patients. The odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to determine the correlation of CYP2C8 polymorphisms with bladder cancer risk. Multifactor dimensionality reduction (MDR) was carried out to investigate the influence of single-nucleotide polymorphism (SNP)-SNP interactions on bladder cancer. Results: Our study showed that two SNPs were significantly associated with an increased risk of bladder cancer (rs1934951: OR 1.96, 95% CI 1.37-2.82, p = 2.67E-04; rs17110453: OR 1.89, 95% CI 1.35-2.67, p = 2.53E-04). On the contrary, two SNPs identified in the study had protective effects on bladder cancer (rs1934953: OR 0.26, 95% CI 0.14-0.47, p = 1.20E-05; rs2275620: OR 0.40, 95% CI 0.21-0.76, p = 0.005). The MDR analysis suggested that the combination of rs1934953, rs1934951, rs2275620, and rs17110453 was the best model to predict bladder cancer (CVC 10/10, testing accuracy 0.6720, p < 0.0001). Conclusion: There was a significant association between CYP2C8 polymorphisms (rs1934953, rs1934951, rs2275620, and rs17110453) and susceptibility to bladder cancer.

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AIM: To evaluate the possible association of CYP2C8 gene polymorphisms with the clinical efficacy and safety of ketorolac in relation to postoperative pain. MATERIALS AND METHODS: The study included 107 patients after video laparoscopic cholecystectomy, who received ketorolac (30 mg 2.0 w/m 3 r/d) as postoperative pain relief. All patients were genotyped for CYP2C8. The pain syndrome was assessed using the visual analog scale, the McGill pain questionnaire. The profile of adverse reactions was assessed by the dynamics of red blood counts, as a possible trigger for the development of gastrointestinal bleeding according to the method of global assessment of triggers (Global Trigger Tool GTT). RESULTS: According to visual analog scale data: in carriers of the genotype CYP2C8*3 (rs10509681) and CYP2C8*3 (rs11572080) after 12, 24, 36, 48 hours the intensity of pain syndrome is lower than in carriers of the wild type (p0.05). According to the McGill pain questionnaire, there were no statistically significant differences in pain intensity between the two groups. CONCLUSION: In carriers of the genotype CYP2C8*3 (rs10509681) and CYP2C8*3 (rs11572080), the effectiveness of anesthesia with ketorolac is higher than in carriers of the wild type. Carriage of the genotype CYP2C8*3 (rs10509681) and CYP2C8*3 (rs10509681) does not affect the risk of developing adverse reactions after ketorolac anesthesia.

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CONTEXT: Ginkgo leaf tablet (GLT), a traditional Chinese herbal formula, is often combined with rosiglitazone (ROS) for type 2 diabetes mellitus treatment. However, the drug-drug interaction between GLT and ROS remains unknown. OBJECTIVE: To investigate the effects of GLT on the pharmacokinetics of ROS and its potential mechanism. MATERIALS AND METHODS: The pharmacokinetics of 10 mg/kg ROS with 100/200 mg/kg GLT as single-dose and 10-day multiple-dose administration were investigated in Sprague-Dawley rats. In vitro, the effects of GLT on the activity of CYP2C8 and CYP2C9 were determined in recombinant human yeast microsomes and rat liver microsomes with probe substrates. RESULTS: The t1/2 of ROS increased from 2.14 ± 0.38 (control) to 2.79 ± 0.37 (100 mg/kg) and 3.26 ± 1.08 h (200 mg/kg) in the single-dose GLT administration. The AUC0-t (139.69 ± 45.46 vs. 84.58 ± 39.87 vs. 66.60 ± 15.90 h·µg/mL) and t1/2 (2.75 ± 0.70 vs. 1.99 ± 0.44 vs. 1.68 ± 0.35 h) decreased significantly after multiple-dose GLT treatment. The IC50 values of quercetin, kaempferol, and isorhamnetin, GLT main constituents, were 9.32, 7.67, and 11.90 µmol/L for CYP2C8, and 27.31, 7.57, and 4.59 µmol/L for CYP2C9. The multiple-dose GLT increased rat CYP2C8 activity by 44% and 88%, respectively. DISCUSSION AND CONCLUSIONS: The metabolism of ROS is attenuated in the single dose of GLT by inhibiting CYP2C8 and CYP2C9 activity, and accelerated after the multiple-dose GLT treatment via inducing CYP2C8 activity in rats, indicating that the clinical dose of ROS should be adjusted when co-administrated with GLT.

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This study aimed to assess the effects of total flavonoid extracts (TFDG) and the monomers of Daphne genkwa on the CYP2C8 activity in vitro and in vivo.The 50% inhibitory concentration (IC50) values were used to determine the inhibitory effect of TFDG and its four monomers for the CYP2C8 activity by recombinant human CYP2C8 (RHCYP2C8) yeast microsome system in vitro, and the volume per dose index (VDI) was predicted the potential inhibition in vivo. The effects of multiple-dose administration of TFDG on the pharmacokinetic parameters of rosiglitazone in rats were evaluated.The IC50 values of apigenin, luteolin, hydroxy-genkwanin, genkwanin, and TFDG were 7.27 µmol/L, 11.9 µmol/L, 28.1 µmol/L, 127 µmol/L, and 13.4 µg/mL, respectively. The VDI values of apigenin and TFDG were 2.15 L and 6.60 L. In vivo study, compared with the control group, the elimination phase half-life and mean residence time in the TFDG treatment group were significantly increased by 96.9% and 106.8% (p <.05), respectively.Apigenin showed a moderate inhibitory effect on the CYP2C8 activity in vitro, while the other three monomers were weak inhibitors. TFDG had a strong inhibitory effect on CYP2C8 in vitro and in vivo, and also inhibited the metabolism of rosiglitazone in rats.

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The antiplatelet agent clopidogrel is listed by the FDA as a strong clinical index inhibitor of cytochrome P450 (CYP) 2C8 and weak clinical inhibitor of CYP2B6. Moreover, clopidogrel is a substrate of-among others-CYP2C19 and CYP3A4. This work presents the development of a whole-body physiologically based pharmacokinetic (PBPK) model of clopidogrel including the relevant metabolites, clopidogrel carboxylic acid, clopidogrel acyl glucuronide, 2-oxo-clopidogrel, and the active thiol metabolite, with subsequent application for drug-gene interaction (DGI) and drug-drug interaction (DDI) predictions. Model building was performed in PK-Sim® using 66 plasma concentration-time profiles of clopidogrel and its metabolites. The comprehensive parent-metabolite model covers biotransformation via carboxylesterase (CES) 1, CES2, CYP2C19, CYP3A4, and uridine 5'-diphospho-glucuronosyltransferase 2B7. Moreover, CYP2C19 was incorporated for normal, intermediate, and poor metabolizer phenotypes. Good predictive performance of the model was demonstrated for the DGI involving CYP2C19, with 17/19 predicted DGI AUClast and 19/19 predicted DGI Cmax ratios within 2-fold of their observed values. Furthermore, DDIs involving bupropion, omeprazole, montelukast, pioglitazone, repaglinide, and rifampicin showed 13/13 predicted DDI AUClast and 13/13 predicted DDI Cmax ratios within 2-fold of their observed ratios. After publication, the model will be made publicly accessible in the Open Systems Pharmacology repository.

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PURPOSE: Tucatinib, a small molecule for the treatment of metastatic HER2-positive breast cancer, was extensively metabolized in humans to multiple oxidative metabolites. To fully understand the elimination and biotransformation pathways of tucatinib, we investigated the in vitro and in vivo metabolism of tucatinib, and also conducted a Phase I trial using [14C]tucatinib. METHODS: To identify the responsible enzymes for tucatinib clearance, we investigated the in vitro metabolism of tucatinib including enzyme phenotyping, which facilitated the discovery of several metabolites in human and monkey plasma and excreta, in particular M1 (ONT-993, an aliphatic hydroxylated metabolite). Stereoselective formation of M1 was further investigated in vitro, in vivo, and in silico. RESULTS: In humans, approximately 86% of the total radiolabeled dose was recovered in feces and 4% in urine; in plasma, approximately 76% of radioactivity circulated as parent drug, with 19% attributed to multiple metabolites. The primary isoforms responsible for the elimination of tucatinib were CYP2C8 and CYP3A4/5. CYP2C8 was shown to possess sole catalytic activity for the formation of M1, whereas CYP3A4/5 and aldehyde oxidase catalyzed the formation of the remaining metabolites. Subsequent investigation revealed that M1 was formed in a stereoselective manner. Examination of the enantiomeric ratio of M1 stereoisomers observed in humans relative to cynomolgus monkeys revealed comparable results, suggesting that the enantiomers that comprise M1 were not considered to be unique or disproportionately high in human. CONCLUSION: CYP2C8 and CYP3A4/5 are the primary drug-metabolizing enzymes involved in the in vitro metabolism of tucatinib, which provided the basis to describe human disposition of tucatinib and formation of the observed metabolites.

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BACKGROUND: Enzalutamide, registered for the treatment of metastatic castration-resistant prostate cancer (mCRPC), is an inducer of multiple CYP-enzymes. Enzalutamide itself is mainly converted by CYP2C8 to the active metabolite N-desmethylenzalutamide (NDME). Due to a pharmacokinetic interaction, combining enzalutamide with a moderate CYP2C8 inhibitor might result in higher enzalutamide concentrations. Addressing this interaction is challenging since pharmacokinetic data are missing. CASE PRESENTATION: We present a case of a Caucasian male with mCRPC who was treated with enzalutamide and a moderate CYP2C8 inhibitor, clopidogrel, concomitantly. Plasma trough levels (Ctrough) of enzalutamide and its active metabolite N-desmethylenzalutamide (NDME) were determined and compared when treated with and without clopidogrel. The sum concentration of enzalutamide and NDME was not affected by coadministration of a moderate CYP2C8 inhibitor. Both treatments were well tolerated and no major side effect were observed. CONCLUSION: This case report shows that enzalutamide can be safely prescribed while cotreated with a moderate CYP2C8-inhibitor, without reducing the dose. More research is warranted to make a statement about the effect of enzalutamide on clopidogrel.

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CYP2C8 is a member of Cytochrome P450 enzymes system. It plays an important role in metabolizing a wide range of exogenous and endogenous compounds. CYP2C8 is involved in the metabolism of more than 100 drugs, typical substrates include: anticancer agents, antidiabetic agents, antimalarial agents, lipid lowering drugs and many others that constitute 20% of clinically prescribed drugs. Genetic variations of CYP2C8 have been reported with different frequencies in different populations. These genetic polymorphisms can lead to differences in the efficacy and safety of different types of medications metabolized by CYP2C8. The aim of this study was to investigate the allele frequencies of CYP2C8*3 (rs10509681 and rs11572080) and CYP2C8*4 (rs1058930) polymorphisms in three populations living in Jordan; Circassians and Chechens and Jordanian-Arabs and compare those frequencies with other populations. A total of 200 healthy Jordanians, 93 Circassians and 88 Chechens were included in this study. Genotyping of CYP2C8*3 and CYP2C8*4 polymorphisms was done by using polymerase chain reaction (PCR) followed by Restriction Fragment Length Polymorphism (RFLP). Using the Chi-square test, we found that the prevalence of CYP2C8*3 and *4 among the three populations were significantly different. Moreover, the mutant allele CYP2C8*3 (416A) was only detected in the Jordanian-Arab population with an allele frequency of 0.082, while the mutant allele CYP2C8*4 (792G) was detected with frequencies of 0.065, 0.122, 0.017 in Jordanian-Arabs, Circassians and Chechens, respectively. As our results show, CYP2C8*3 was undetectable in our Circassians and Chechens samples, on the other hand, Circassians had the highest allele frequency of CYP2C8*4 compared to Chechens and Jordanian-Arabs. These genetic variations of the gene encoding the CYP2C8 drug metabolizing enzymes can lead to clinical differences in drug metabolism and ultimately variations in drug effectiveness and toxicities. This study provides evidence for the importance of personalized medicine in these populations and can be the foundation for future clinical studies.

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CONTEXT: As an inhibitor cytochrome P450 family 2 subfamily C polypeptide 8 (CYP2C8), quercetin is a naturally occurring flavonoid with its glycosides consumed at least 100 mg per day in food. However, it is still unknown whether quercetin and selexipag interact. OBJECTIVE: The study investigated the effect of quercetin on the pharmacokinetics of selexipag and ACT-333679 in beagles. MATERIALS AND METHODS: The ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to investigate the pharmacokinetics of orally administered selexipag (2 mg/kg) with and without quercetin (2 mg/kg/day for 7 days) pre-treatment in beagles. The effect of quercetin on the pharmacokinetics of selexipag and its potential mechanism was studied through the pharmacokinetic parameters. RESULTS: The assay method was validated for selexipag and ACT-333679, and the lower limit of quantification for both was 1 ng/mL. The recovery and the matrix effect of selexipag were 84.5-91.58% and 94.98-99.67%, while for ACT-333679 were 81.21-93.90% and 93.17-99.23%. The UPLC-MS/MS method was sensitive, accurate and precise, and had been applied to the herb-drug interaction study of quercetin with selexipag and ACT-333679. Treatment with quercetin led to an increased in Cmax and AUC0-t of selexipag by about 43.08% and 26.92%, respectively. While the ACT-333679 was about 11.11% and 18.87%, respectively. DISCUSSION AND CONCLUSION: The study indicated that quercetin could inhibit the metabolism of selexipag and ACT-333679 when co-administration. Therefore, the clinical dose of selexipag should be used with caution when co-administered with foods high in quercetin.

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Chemotherapy is the mainstay of treatment for prostate cancer, with paclitaxel being commonly used for hormone-resistant prostate cancer. However, drug resistance often develops and leads to treatment failure in a variety of prostate cancer patients. Therefore, it is necessary to enhance the sensitivity of prostate cancer to chemotherapy. Lovastatin (LV) is a natural compound extracted from Monascus-fermented foods and is an inhibitor of HMG-CoA reductase (HMGCR), which has been approved by the FDA for hyperlipidemia treatment. We have previously found that LV could inhibit the proliferation of refractory cancer cells. Up to now, the effect of LV on chemosensitization and the mechanisms involved have not been evaluated in drug-resistant prostate cancer. In this study, we used prostate cancer cell line PC3 and its paclitaxel-resistant counterpart PC3-TxR as the cell model. Alamar Blue cell viability assay showed that LV and paclitaxel each conferred concentration-dependent inhibition of PC3-TxR cells. When paclitaxel was combined with LV, the proliferation of PC3-TxR cells was synergistically inhibited, as demonstrated by combination index <1. Moreover, colony formation decreased while apoptosis increased in paclitaxel plus LV group compared with paclitaxel alone group. Quantitative RT-PCR showed that the combination of paclitaxel and LV could significantly reduce the expression of CYP2C8, an important drug-metabolizing enzyme. Bioinformatics analysis from the TCGA database showed that CYP2C8 expression was negatively correlated with progression-free survival (PFS) in prostate cancer patients. Our results suggest that LV might increase the sensitivity of resistant prostate cancer cells to paclitaxel through inhibition of CYP2C8 and could be utilized as a chemosensitizer for paclitaxel-resistant prostate cancer cells.

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