Drug Interaction Between Favipiravir and Warfarin: A Case Series.

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.

CYP2D6 and CYP2C8 pharmacogenetics and pharmacological interactions to predict imatinib plasmatic exposure in GIST patients.

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.

CYP2C8 and CYP2J2 gene variations increase the risk of hypertensive intracerebral hemorrhage.

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.

Potential Association of Cytochrome P450 Copy Number Alteration in Tumour with Chemotherapy Resistance in Lung Adenocarcinoma Patients.

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.

Lovastatin enhances chemosensitivity of paclitaxel-resistant prostate cancer cells through inhibition of CYP2C8.

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.

Effects of the total flavonoid extracts and the monomers of Daphne genkwa on CYP2C8 activity.

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.

Effects of ginkgo leaf tablet on the pharmacokinetics of rosiglitazone in rats and its potential mechanism.

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.

Effect of quercetin on the pharmacokinetics of selexipag and its active metabolite in beagles.

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.

[Evaluation of the association of polymorphisms of the CYP2C8 gene with the efficacy and safety of ketorolac in patients with postoperative pain syndrome].

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.

Influence of cytochrome P450 (CYP) 2C8 polymorphisms on the efficacy and tolerability of artesunate-amodiaquine treatment of uncomplicated Plasmodium falciparum malaria in Zanzibar.

BACKGROUND: The anti-malarial drug, amodiaquine, a commonly used, long-acting partner drug in artemisinin-based combination therapy, is metabolized to active desethyl-amodiaquine (DEAQ) by cytochrome P450 2C8 (CYP2C8). The CYP2C8 gene carries several polymorphisms including the more frequent minor alleles, CYP2C8*2 and CYP2C8*3. These minor alleles have been associated with decreased enzymatic activity, slowing the amodiaquine biotransformation towards DEAQ. This study aimed to assess the influence of these CYP2C8 polymorphisms on the efficacy and tolerability of artesunate-amodiaquine (AS-AQ) treatment for uncomplicated Plasmodium falciparum malaria in Zanzibar. METHODS: Dried blood spots on filter paper were collected from 618 children enrolled in two randomized clinical trials comparing AS-AQ and artemether-lumefantrine in 2002-2005 in Zanzibar. Study participant were under five years of age with uncomplicated falciparum malaria. Human CYP2C8*2 and CYP2C8*3 genotype frequencies were determined by PCR-restriction fragment length polymorphism. Statistical associations between CYP2C8*2 and/or CYP2C8*3 allele carriers and treatment outcome or occurrence of adverse events were assessed by Fisher's exact test. RESULTS: The allele frequencies of CYP2C8*2 and CYP2C8*3 were 17.5 % (95 % CI 15.4-19.7) and 2.7 % (95 % CI 1.8-3.7), respectively. There was no significant difference in the proportion of subjects carrying either CYP2C8*2 or CYP2C8*3 alleles amongst those with re-infections (44.1 %; 95 % CI 33.8-54.8) or those with recrudescent infections (48.3 %; 95 % CI 29.4-67.5), compared to those with an adequate clinical and parasitological response (36.7 %; 95 % CI 30.0-43.9) (P = 0.25 and P = 0.31, respectively). However, patients carrying either CYP2C8*2 or CYP2C8*3 alleles were significantly associated with an increased occurrence of non-serious adverse events, when compared with CYP2C8 *1/*1 wild type homozygotes (44.9 %; 95 % CI 36.1-54.0 vs. 28.1 %; 95 % CI 21.9-35.0, respectively; P = 0.003). CONCLUSIONS: CYP2C8 genotypes did not influence treatment efficacy directly, but the tolerability to AS-AQ may be reduced in subjects carrying the CYP2C8*2 and CYP2C8*3 alleles. The importance of this non-negligible association with regard to amodiaquine-based malaria chemotherapy warrants further investigation.

Clopidogrel, a CYP2C8 inhibitor, causes a clinically relevant increase in the systemic exposure to the active metabolite of selexipag in healthy subjects.

AIMS: Selexipag is a prostacyclin receptor agonist approved for the treatment of pulmonary arterial hypertension. Cytochrome P450 (CYP) 2C8 is involved in the metabolism of selexipag and its active metabolite, ACT-333679. This study evaluated the interaction of selexipag and clopidogrel, a CYP2C8 inhibitor. METHODS: The study had a 2-treatment, 1-sequence, crossover design. Pharmacokinetics (PK) and CYP2C8 genotype were assessed in healthy male subjects administered selexipag (200 µg twice daily [b.i.d.]) alone or with clopidogrel (300 mg single dose or 75 mg once daily [o.d.]). PK modelling and simulation were conducted to support dosing recommendations. RESULTS: Clopidogrel had a comparatively small effect on selexipag (<1.5-fold difference in any PK variable). For ACT-333679, the major contributor to the drug effect, the area under the plasma concentration-time curve during a dose interval and the maximum plasma concentration increased 2.25-fold (90% confidence interval [CI] 2.06, 2.46) and 1.69-fold (90% CI 1.55, 1.84), respectively with clopidogrel 300 mg and 2.70-fold (90% CI 2.45, 2.96) and 1.90-fold (90% CI 1.72, 2.11), respectively with clopidogrel 75 mg. The effect of clopidogrel on selexipag and ACT-333679 exposure was comparable for all identified CYP2C8 genotypes. PK simulations predicted comparable exposure to ACT-333679 following selexipag 400 µg b.i.d., 400 µg o.d. in combination with clopidogrel 75 mg o.d and 200 µg b.i.d. with clopidogrel 75 mg o.d. CONCLUSION: Results suggest that ACT-333679 exposure can be maintained within the therapeutic range by reducing selexipag dosing frequency to o.d. or dose to half, when selexipag is coadministered with clopidogrel.

Comparison on Metabolism of Estradiol and Its 17-Sulfate by Recombinant Human CYP Isoforms.

To identify the CYP isoforms involved in the production of 2-hydroxyestradiol 17-sulfate (2-OH-ES), which we assume to be an antioxidant in vivo, the 2-hydroxylation reaction of estradiol 17-sulfate (ES) by human liver microsome was investigated. As a result, it was estimated that CYP2C8 and 2C9 were largely involved in the production of 2-OH-ES. Therefore, the 2-hydroxylation kinetic analysis of ES was performed for both CYPs, and the metabolic clearance Vmax/Km (µL/nmol CYP/min) was determined. On comparing the results of ES with those of estradiol (E2), it was found that CYP2C8 was about 2.5 times higher and CYP2C9 was about 3 times higher, and ES was more likely to be a substrate for the 2-hydroxylation reaction by both CYPs. The CYP isoforms involved in A-ring hydroxylation of E2 and ES differed. From this, it was speculated that 2-OH-ES plays a different role to 2-hydroxyestradiol (2-OH-E2), which is recognized as an antioxidant in the body.

The in vivo disposition of subcutaneous injected 14C-razuprotafib (14C-AKB-9778), a sulphamic acid phosphatase inhibitor, in nonclinical species and human.

The disposition of radioactivity following subcutaneous 14C-razuprotafib, a Tie2 activator, was explored in multiple species.The absorption and clearance of razuprotafib and total radioactivity in human plasma are rapid and pharmacokinetics support razuprotafib as primary circulating component. Radioactivity is distributed greater to human plasma than whole blood (B:P = 0.36).In pigmented rats, radioactivity distributes to whole-body tissues rapidly and, within 24 h, is localised to elimination pathway end organs and injection site.Overall recovery of radioactivity across species is >93%, with the majority recovered within 24-48 h, and >80% in faeces.The CYP2C8 enzyme contributes significantly to razuprotafib metabolism.A hydrolysis product of razuprotafib (m/z- 380) is the main component in rat plasma at 2 h (49% peak area radioactivity), while razuprotafib (m/z- 585) is the main component in plasma for dog (58%), monkey (99.3%), and human (100%).Razuprotafib is present in dog, monkey, and human faeces, with the greatest percentage of radioactivity as metabolites. The major metabolite (>25%) in monkey and human, m/z- 633, is an S-methylated oxidised derivative of razuprotafib and is localised in faeces.Overall disposition of 14C-razuprotafib in human is best modelled by monkey over lower order species.

Oxidative metabolism of razuprotafib (AKB-9778), a sulfamic acid phosphatase inhibitor, in human microsomes and recombinant human CYP2C8 enzyme.

Razuprotafib, a sulphamic acid-containing phosphatase inhibitor, is shown in vivo to undergo enzymatic oxidation and methylation to form a major metabolite in monkey and human excreta with an m/z- value of 633.LC-MS/MS analysis of samples derived from incubations of razuprotafib with human liver microsomes and recombinant CYP2C8 enzyme has elucidated the metabolic pathway for formation of the thiol precursor to the S-methyl metabolite MS633 (m/z- 633).Under in vitro conditions, the major pathway of razuprotafib metabolism involves extensive oxidation of the thiophene and phenyl rings.A single oxidation takes place at one of the phenyl groups. Multiple oxidations occur at the thiophene moiety: initial oxidation results in the formation of a thiolactone followed by a second oxidation giving rise to an S-oxide of the thiolactone, which is further metabolised to the ring-opened form and ultimate formation of a thiol (m/z- 619).An additional mono-oxidation pathway involves epoxidation of the thiophene followed by hydrolysis to a diol.The thiol and diol metabolites are trapped by the addition of a nucleophilic trapping agent, 3-methoxyphenacyl bromide (MPB), giving adducts with m/z- 767.The thiol is a likely precursor to the major in vivo razuprotafib metabolite, MS633.

[CYP2C8, PTGS-1, 2 gene polymorphisms prevalence associated with sensitivity to non-steroidal anti-inflammatory drugs among North Caucasus ethnic groups].

AIM: Find the prevalence of CYP2C8*3 (rs10509681; rs11572080), PTGS-1 (rs10306135; rs12353214) and PTGS-2 (rs20417) alleles and genotypes in four ethnic groups among Laks, Avars, Dargins and Kumyks. MATERIALS AND METHODS: The study involved 400 volunteers from four ethnic groups living in Republic of Dagestan: 100 participants from each group. Carriage of polymorphic markers was determined by reverse transcription polymerase chain reaction. RESULTS: Minor allele frequency of the CYP2C8 (rs10509681) was 5.5% in Avars, 10% in Dargins, Laks and Kumyks 6.5% both; CYP2C8 (rs11572080) was 5.5% in Avars, 9.5% in Dargins, 6.5% in Laks, 8.5% in Kumyks; PTGS-1 (rs10306135) in Avars 10.5%, in Dargins 13.0%, in Laks 9.5% and Kumyks 7.5%; PTGS-1 (rs12353214) in Avars 9.0%, in Dargins 4.5%, in Laks 7.5%, in Kumyks 8.0%; PTGS-2 (rs20417) in Avars 1.0%, in Dargins 2.5%, in Laks 3.5%, in Kumyks 5.0%. There were no significant differences between groups. CONCLUSION: The study of CYP2C8 and PTGS-1 and 2 gene polymorphisms is promising for predicting the effectiveness and safety of non-steroidal anti-inflammatory drug therapy, due to the high prevalence of these polymorphisms in ethnic groups in the North Caucasus.

In vitro inhibitory effect of lysionotin on the activity of cytochrome P450 enzymes.

CONTEXT: Lysionotin, a major extraction of Lysionotus pauciflorus Maxim (Gesneriaceae), has a variety of pharmacological properties commonly used in the treatment of lung disease. A study of lysionotin on the activity of human liver cytochrome P450 (CYP) enzymes can provide guidance on the clinical application of lysionotin. OBJECTIVE: This study investigated the interaction between lysionotin and CYPs. MATERIAL AND METHOD: The effects of 100 µM lysionotin on eight human liver CYP isoforms (i.e., 1A2, 3A4, 2A6, 2E1, 2D6, 2C9, 2C19 and 2C8) were investigated in vitro using human liver microsomes (HLMs) with specific inhibitor as positive control and untreated HLMs as control. Meanwhile, the enzyme kinetic parameters were calculated. A time-dependent study was performed with a time interval of 5 min in 30 min. RESULTS: Lysionotin was found to inhibit the activity of CYP3A4, 2C19, and 2C8, with IC50 values of 13.85, 24.95, and 30.05 µM, respectively. The inhibition of CYP3A4 was performed in a non-competitive manner with the Ki value of 6.83 µM, while the inhibition of CYP2C19 and 2C8 was performed in a competitive manner with Ki values of 12.41 and 14.51 µM. Moreover, it was found that the inhibition of CYP3A4 was time-dependent with K I/K inact value of 6.618/0.048 min/µM. Discussion and conclusions: The in vitro inhibitory effect of lysionotin on the activity of CYP3A4, 2C19, and 2C8 indicated potential drug interactions between lysionotin and drugs metabolised by CYP3A4, 2C19, and 2C8. Further in vivo experiments are needed to assess the potential interactions.

Impact of gene polymorphisms on the systemic toxicity to paclitaxel/carboplatin chemotherapy for treatment of gynecologic cancers.

PURPOSE: Gynecologic malignancies are often detected in advanced stages, requiring chemotherapy with taxane/platinum combinations, which may cause severe toxicities, such as neutropenia and peripheral neuropathy. Gene polymorphisms are suspected as possible causes for the interindividual variability on chemotherapy toxicities. OBJECTIVE: To evaluate the role of ABCB1 1236C>T, 3435C>T; CYP2C8*3; CYP3A5*3C variants on paclitaxel/carboplatin toxicities. METHODS: A cohort of 503 gynecologic cancer patients treated with paclitaxel/carboplatin at the Brazilian National Cancer Institute (INCA-Brazil) was recruited (2013-2017). Polymorphisms were genotyped by real-time PCR, and toxicities were evaluated by patients' interviews at each chemotherapy cycle and by data collection from electronic records. The association of clinical features and genotypes with severe toxicities was estimated using Pearson's Chi square tests and multiple regression analyses, with calculation of adjusted odds ratios (ORadjusted), and respective 95% confidence intervals (95% CI). RESULTS: CYP2C8*3 was significantly associated with increased risks of severe (grades 3-4) neutropenia (ORadjusted 2.11; 95% CI 1.24-3.6; dominant model) and severe thrombocytopenia (ORadjusted 4.93; 95% CI 1.69-14.35; recessive model), whereas ABCB1 variant genotypes (ORadjusted 2.13; 95% CI 1.32-3.42), in association with CYP2C8*3 wild type (GG) (ORadjusted 1.93; 95% CI 1.17-3.19), were predictive of severe fatigue. CONCLUSIONS: The present study suggests that CYP2C8*3 is a potential predictor of hematological toxicities related to paclitaxel/carboplatin treatment. Since hematological toxicities, especially neutropenia, may lead to dose delay or treatment interruption, such prognostic evaluation may contribute to clinical management of selected patients with paclitaxel-based chemotherapy.

Polymorphisms of CYP2C8 Alter First-Electron Transfer Kinetics and Increase Catalytic Uncoupling.

Cytochrome P450 2C8 (CYP2C8) epoxygenase is responsible for the metabolism of over 60 clinically relevant drugs, notably the anticancer drug Taxol (paclitaxel, PAC). Specifically, there are naturally occurring polymorphisms, CYP2C8*2 and CYP2C8*3, that display altered PAC hydroxylation rates despite these mutations not being located in the active site. Herein, we demonstrate that these polymorphisms result in a greater uncoupling of PAC metabolism by increasing the amount of hydrogen peroxide formed per PAC turnover. Anaerobic stopped-flow measurements determined that these polymorphisms have altered first electron transfer kinetics, compared to CYP2C8*1 (wildtype), that suggest electron transfer from cytochrome P450 reductase (CPR) is disfavored. Therefore, these data demonstrate that these polymorphisms affect the catalytic cycle of CYP2C8 and suggest that redox interactions with CPR are disrupted.

The Effect of Flavonoid Aglycones on the CYP1A2, CYP2A6, CYP2C8 and CYP2D6 Enzymes Activity.

Cytochromes P450 are major metabolic enzymes involved in the biotransformation of xenobiotics. The majority of xenobiotics are metabolized in the liver, in which the highest levels of cytochromes P450 are expressed. Flavonoids are natural compounds to which humans are exposed through everyday diet. In the previous study, selected flavonoid aglycones showed inhibition of CYP3A4 enzyme. Thus, the objective of this study was to determine if these flavonoids inhibit metabolic activity of CYP1A2, CYP2A6, CYP2C8, and CYP2D6 enzymes. For this purpose, the O-deethylation reaction of phenacetin was used for monitoring CYP1A2 enzyme activity, coumarin 7-hydroxylation for CYP2A6 enzyme activity, 6-α-hydroxylation of paclitaxel for CYP2C8 enzyme activity, and dextromethorphan O-demethylation for CYP2D6 enzyme activity. The generated metabolites were monitored by high-performance liquid chromatography coupled with diode array detection. Hesperetin, pinocembrin, chrysin, isorhamnetin, and morin inhibited CYP1A2 activity; apigenin, tangeretin, galangin, and isorhamnetin inhibited CYP2A6 activity; and chrysin, chrysin-dimethylether, and galangin inhibited CYP2C8. None of the analyzed flavonoids showed inhibition of CYP2D6. The flavonoids in this study were mainly reversible inhibitors of CYP1A2 and CYP2A6, while the inhibition of CYP2C8 was of mixed type (reversible and irreversible). The most prominent reversible inhibitor of CYP1A2 was chrysin, and this was confirmed by the docking study.

Effect of pterostilbene on in vitro drug metabolizing enzyme activity.

Pterostilbene is a natural polyphenol compound found in small berries that is related to resveratrol, but has better bioavailability and a longer half-life. The purpose of this study was to assess the potential inhibitory effect of pterostilbene on in vitro drug metabolism. The effect of pterostilbene on cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) enzyme activities were studied using the enzyme-selective substrates amodiaquine (CYP2C8), midazolam (CYP3A4), estradiol (UGT1A1), serotonin (UGT1A6) and mycophenolic acid (UGT1A8/9/10). The IC50 value was used to express the strength of inhibition. Further, a volume per dose index (VDI) was used to estimate the potential for in vivo interactions. Pterostilbene significantly inhibited CYP2C8 and UGT1A6 activities. The IC50 (mean ±â€¯SE) values for CYP2C8 and UGT1A6 inhibition were 3.0 ±â€¯0.4 µM and 15.1 ±â€¯2.8 µM, respectively; the VDI exceeded the predefined threshold of 5 L/dose for both CYP2C8 and UGT1A6, suggesting a potential for interaction in vivo. Pterostilbene did not inhibit the metabolism of the other enzyme-selective substrates. The results of this study indicate that pterostilbene inhibits CYP2C8 and UTG1A6 activity in vitro and may inhibit metabolism by these enzymes in vivo. Clinical studies are warranted to evaluate the in vivo relevance of these interactions.