Induction Of Cytochrome P450 Enzymes Research Articles

Interactions of Polychlorinated Biphenyls and Their Metabolites with the Brain and Liver Transcriptome of Female Mice.

Exposure to polychlorinated biphenyls (PCBs) is linked to neurotoxic effects. This study aims to close knowledge gaps regarding the specific modes of action of PCBs in female C57BL/6J mice (>6 weeks) orally exposed for 7 weeks to a human-relevant PCB mixture (MARBLES mix) at 0, 0.1, 1, and 6 mg/kg body weight/day. PCB and hydroxylated PCB (OH-PCBs) levels were quantified in the brain, liver, and serum; RNA sequencing was performed in the striatum, prefrontal cortex, and liver, and metabolomic analyses were performed in the striatum. Profiles of PCBs but not their hydroxylated metabolites were similar in all tissues. In the prefrontal cortex, PCB exposure activated the oxidative phosphorylation respiration pathways, while suppressing the axon guidance pathway. PCB exposure significantly changed the expression of genes associated with neurodevelopmental and neurodegenerative diseases in the striatum, impacting pathways like growth hormone synthesis and dendrite development. PCBs did not affect the striatal metabolome. In contrast to the liver, which showed activation of metabolic processes following PCB exposure and the induction of cytochrome P450 enzymes, the expression of xenobiotic processing genes was not altered by PCB exposure in either brain region. Network analysis revealed complex interactions between individual PCBs (e.g., PCB28 [2,4,4'-trichlorobiphenyl]) and their hydroxylated metabolites and specific differentially expressed genes (DEGs), underscoring the need to characterize the association between specific PCBs and DEGs. These findings enhance the understanding of PCB neurotoxic mechanisms and their potential implications for human health.

Human quad liver-on-chip system as a tool toward bridging the gap between animals and humans regarding toxicology and pharmacology of a cannabidiol-rich cannabis extract

Cannabidiol (CBD) is a major phytocannabinoid from Cannabis sativa. It is currently widely available and widely used in the USA, but despite its rapid progress to market, the pharmacology and toxicology of both CBD and cannabidiol-rich cannabis extracts (CRCE) remain largely unknown. The goals of this study were to investigate the potential of a novel human microphysiological system to emulate CRCE-induced hepatotoxicity and pharmacological properties demonstrated in animal models. For this purpose, C57BL6/J male mice were subjected to dosing with either 0, 61.5, 184.5, or 615 mg/kg of CRCE for 10 days. The liver-on-chip system, incorporating human primary hepatocytes, sinusoidal endothelial cells, as well as Kupffer and stellate cells was subjected to 0, 300, 1,200, or 4,400 ng/mL of CRCE (8 h exposure followed by 16 h washout) for 5 days. Administration of CRCE in mice resulted in nearly 4-fold elevations of plasma ALT at 615 mg/kg (p < 0.01) and a dose-dependent decrease in intrahepatic miR-122. Elevated levels of ALT, paralleled by decreased intrahepatic and increased effluent levels of miR-122, were also observed in the liver-on-chip, although these results were not statistically significant. Exposure to CRCE resulted in a robust and dose-dependent induction of key cytochrome P450 enzymes, namely Cyp1a2, Cyp2b6 (CYP2B10), Cyp2e1, and Cyp2c9 (CYP2C19) in both mouse livers and liver-on-chip. The results of this study demonstrate the congruence between the responses observed in mouse and human liver-on-chip experimental systems and provide evidence of the potential microphysiological systems hold for translating animal data into clinical practice.

Shining a Light on Inflammation as a Critical Modulator of Drug Metabolism.

Since his graduate studies on alcohol induction of a novel cytochrome P450 (P450) enzyme, through his postdoctoral work on hormonal regulation of sexually differentiated cytochrome P450s (P450s), the author has maintained an interest in the regulation of drug metabolizing enzymes. This article is a recounting of his scientific career and focuses on his laboratory's work on inflammatory regulation of P450 enzymes that formed the basis for the Bernard B. Brodie Award. Key findings and publications are identified and discussed that contributed to the elucidation of some important principles: 1) inflammatory stimuli generally downregulate P450 enzymes, resulting in reduced metabolism of substrate drugs; 2) the main mechanism for this downregulation is transcriptional and involves both the activation of negatively acting transcription factors and the suppression of positive transcription factors; 3) inflammatory cytokines such as interleukin 1, interleukin 6, and tumor necrosis factor α act on hepatocytes to mediate this regulation; 4) these cytokines selectively regulate different P450 enzymes, and therefore different P450s are downregulated in different inflammatory diseases or disease models; 5) nitric oxide formed by inducible nitric oxide synthase 2 reacts with P450s in an enzyme-specific manner to stimulate their proteolytic degradation; and 6) both tyrosine nitration and heme nitrosylation are likely required for this NO-stimulated degradation. Finally, findings from clinical studies are discussed that shine a light on the importance of P450 regulation by inflammation for drug development, clinical practice, and personalized medicine. SIGNIFICANCE STATEMENT: This article discusses the key publications and findings in the author's laboratory that helped to identify inflammation as an important factor contributing to interindividual variation in drug metabolism.

Coadministration of Voriconazole and Rifabutin Can Increase the Risk of Adverse Drug Reactions in Patients with Multiple Infections.

Coinfection of tuberculosis or nontuberculous mycobacteria and Aspergillus presents a challenge in medication selection because of the pharmacokinetic interactions between rifampin and voriconazole. Some researchers have suggested the use of rifabutin as an alternative to rifampin because of its lower hepatic cytochrome P450 enzyme induction potency despite its contraindication to drug labels. This study presents clinical cases of voriconazole and rifabutin coadministration and their potential risks. This retrospective study was conducted using clinical data from patients who met the following criteria: (1) admitted to Seoul National University Hospital between July 2014 and August 2023 and (2) concurrently administered rifabutin and voriconazole for more than 5 days. Among the 6 patients analyzed, 4 experienced adverse drug reactions (ADRs). Three patients experienced visual and auditory hallucinations, lower extremity numbness, or delirious behavior. Two patients had prolonged the time from the start of the Q wave to the end of the T wave intervals, and 1 had elevated aspartate aminotransferase and alanine aminotransferase levels. In addition, 2 patients experienced severe nausea, poor oral intake, and weight loss. Despite receiving 1.81-fold the recommended voriconazole dosage, a therapeutic concentration (1.0-5.5 mg/L) was not achieved because of cytochrome P450 induction by rifabutin. However, during septic shock, the voriconazole concentration increased by 13.7- to 36-fold. Concurrent use of rifabutin and voriconazole was associated with ADRs, including the time from the start of the Q wave to the end of the T wave prolongation, hallucinations, and severe nausea. Moreover, initially, there was a significant decrease in voriconazole concentrations; however, these concentrations substantially increased during septic shock. Therefore, it is essential to monitor drug concentrations and ADRs during concurrent use of voriconazole and rifabutin.

A review on drug interaction

Drug interaction occur when the response of one drug is altered by the simultaneous or closely time administration of another drug. Polypharmacy involving the simultaneous use of multiple drugs, raise concern due to unpredictable and potential severe internation. While some drug interactions are intentionally utilized in therapeutics strategies, their severity can vary making prediction challenging. Prescribing multiple medications increases the risk of drug interactions, which can occur with other drugs, foods, beverages, and herbs, both inside and outside the body. Understanding in vitro interactions is crucial to prevent drug activity loss before administration. While not all theoretical drug interactions may occur in practice, they remain a significant cause of adverse events associated with drug administration. Drug-drug interactions (DDIs) represent a significant source of medication errors in developed nations, especially among the elderly who often take multiple medications simultaneously, leading to a prevalence of 20-40%. The complexity of managing therapy increases with poly-therapy, elevating the risk of clinically significant DDIs that can either trigger adverse drug reactions or diminish clinical efficacy. DDIs are typically categorized into two groups: pharmacokinetic and pharmacodynamic. In vivo interactions at pharmacokinetic level affect absorption, distribution, biotransformation or excretion of drugs. Induction or inhibition of cytochrome P450 (CYP450) enzymes forms a major basis of drug interactions. Induction of metabolism of a substrate drug leads to treatment failure.

A web-based scoping review assessing the influence of smoking and smoking cessation on antidiabetic drug meabolism: implications for medication efficacy.

Currently 1.3 billion individuals globally engage in smoking, leading to significant morbidity and mortality, particularly among diabetic patients. There is urgent need for a better understanding of how smoking influences antidiabetic treatment efficacy. The review underscores the role of cigarette smoke, particularly polycyclic aromatic hydrocarbons (PAHs), in modulating the metabolic pathways of antidiabetic drugs, primarily through the induction of cytochrome P450 (CYP450) enzymes and uridine diphosphate (UDP)-glucuronosyltransferases (UGTs), thus impacting drug pharmacokinetics and therapeutic outcomes. Furthermore, the review addresses the relatively uncharted territory of how smoking cessation influences diabetes treatment, noting that cessation can lead to significant changes in drug metabolism, necessitating dosage adjustments. Special attention is given to the interaction between smoking cessation aids and antidiabetic medications, a critical area for patient safety and effective diabetes management. This scoping review aims to provide healthcare professionals with the knowledge to better support diabetic patients who smoke or are attempting to quit, ensuring tailored and effective treatment strategies. It also identifies gaps in current research, advocating for more studies to fill these voids, thereby enhancing patient care and treatment outcomes for this at-risk population.

Clinical pharmacokinetics and pharmacodynamics of venetoclax, a selective B-cell lymphoma-2 inhibitor.

Venetoclax, a highly potent BCL-2 inhibitor, is indicated for treatment of some hematologic malignancies as monotherapy, and/or in combination with other agents. Venetoclax pharmacokinetics has been extensively characterized in patients and healthy participants. After oral dosing, the median time to reach maximum plasma concentration ranged from 5 to 8 h and harmonic mean half-life ranged from 14 to 18 h. Food increases venetoclax bioavailability by 3-5-fold and venetoclax should be administered with food to ensure adequate and consistent bioavailability. Venetoclax is eliminated via cytochrome P450 (CYP)3A metabolism, and a negligible amount of unchanged drug is excreted in urine. Strong CYP3A/P-glycoprotein inhibitors increased venetoclax exposures (AUC) by 1.44- to 6.90-fold while a significant decrease (71%) has been observed when dosed with strong CYP3 inducers. Venetoclax does not inhibit or induce CYP enzymes or transporters. Venetoclax pharmacokinetics is not appreciably altered by age, weight, sex, but the exposure is up to twofold higher in participants from Asian countries. Mild-to-severe renal impairment or end-stage renal disease do not alter venetoclax exposures, and venetoclax is not cleared by dialysis. Although mild-to-moderate hepatic impairment does not affect venetoclax exposures, twofold higher exposure was observed in subjects with severe hepatic impairment. Venetoclax exposure is comparable across patients with different hematologic malignancies and healthy participants. Overall, venetoclax exposure is only affected by food and CYP3A modulators and is only higher in Asian subjects and subjects with severe hepatic impairment. Venetoclax exposure-response relationships are malignancy-dependent and can be different between monotherapy and combination therapy.

Assessment of cytochrome P450 induction in canine intestinal organoid models

Understanding cytochrome P450 (CYP) enzymes in the canine intestine is vital for predicting drug metabolism and developing safer oral medications. This study evaluates canine colonoids as a model to assess the expression and induction of essential intestinal CYP enzymes. Canine colonoids were cultured in expansion medium (EM) with Wnt-3A and in differentiation medium (DM) without Wnt-3A. We assessed the mRNA expression of CYP2B11, CYP2C21, CYP3A12, and CYP3A98 using qPCR and examined the effects of rifampicin and phenobarbital as inducers. Our findings show that DM significantly increased the mRNA expression of CYP3A98 and CYP2B11, but not CYP3A12, compared to EM. CYP2C21, not typically expressed in the intestine, remained unexpressed in colonoids. Rifampicin induced CYP3A98, aligning with pregnane x receptor (PXR) regulation, while phenobarbital did not, suggesting no constitutive androstane receptor (CAR) involvement. CYP2B11 did not respond to either inducer, suggesting alternative regulatory pathways in canine colonoids. This study is a pioneering effort to establish conditions for studying P450 expression in canine colonoids, confirming significant CYP3A98 expression in the canine intestine. It demonstrated colonoids can induce CYP activity post drug treatments. Further research is needed to enhance species-specific drug metabolism understanding and validate this model for broader applications.

Regulation of Benzo[a]pyrene-Induced Hepatic Lipid Accumulation through CYP1B1-Induced mTOR-Mediated Lipophagy.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is caused by lipid accumulation within the liver. The pathogenesis underlying its development is poorly understood. Benzo[a]pyrene (B[a]P) is a polycyclic aromatic hydrocarbon and a group 1 carcinogen. The aryl hydrocarbon receptor activation by B[a]P induces cytochrome P450 (CYP) enzymes, contributing to hepatic lipid accumulation. However, the molecular mechanism through which the B[a]P-mediated induction of CYP enzymes causes hepatic lipid accumulation is unknown. This research was conducted to elucidate the role of CYP1B1 in regulating B[a]P-induced lipid accumulation within hepatocytes. B[a]P increased hepatic lipid accumulation, which was mitigated by CYP1B1 knockdown. An increase in the mammalian target of rapamycin (mTOR) by B[a]P was specifically reduced by CYP1B1 knockdown. The reduction of mTOR increased the expression of autophagic flux-related genes and promoted phagolysosome formation. Both the expression and translocation of TFE3, a central regulator of lipophagy, were induced, along with the expression of lipophagy-related genes. Conversely, enhanced mTOR activity reduced TFE3 expression and translocation, which reduced the expression of lipophagy-related genes, diminished phagolysosome production, and increased lipid accumulation. Our results indicate that B[a]P-induced hepatic lipid accumulation is caused by CYP1B1-induced mTOR and the reduction of lipophagy, thereby introducing novel targets and mechanisms to provide insights for understanding B[a]P-induced MASLD.

Pharmacokinetics and Drug-Drug Interaction of Ocedurenone (KBP-5074) in vitro and in vivo.

Ocedurenone (KBP-5074) is a novel nonsteroidal mineralocorticoid receptor antagonist that has demonstrated safety and efficacy in clinical trials in patients with uncontrolled hypertension and stage 3b/4 chronic kidney disease. This study evaluated the involvement of cytochrome P450 (CYP) isozymes and drug transporters in the biotransformation of ocedurenone, and whether ocedurenone inhibited or induced CYP enzymes and transporters. Clinical pharmacokinetic drug-drug interaction (DDI) of ocedurenone with CYP3A inhibitor and inducer were investigated in healthy volunteers. In vitro tests were conducted to determine which CYP enzymes were involved in ocedurenone's metabolism and whether ocedurenone inhibited or induced these CYP enzymes; ocedurenone substrate characteristics for efflux and uptake transporters and its inhibitory potential on major drug transporters were also assessed. A clinical DDI study was conducted in healthy volunteers to evaluate the effects of a strong CYP3A inhibitor (itraconazole) and inducer (rifampin) on ocedurenone's pharmacokinetics. The in vitro study showed that ocedurenone was primarily metabolized by CYP3A4 and that it did not inhibit CYP enzymes. Ocedurenone appeared to be a substrate of BCRP and P-gp efflux transporters and inhibited BCRP, BSEP, MDR1, MATE1 and 2-K, OATP1B1/3, and OCT1. The clinical DDI study showed that itraconazole reduced ocedurenone's oral clearance by 51% and increased area under the plasma concentration-time curve extrapolated to infinity(AUC0-inf) by104%, while rifampin increased its oral clearance by 6.4-fold and decreased plasma AUC0-inf by 84%. Ocedurenone was shown to be a CYP3A substrate, with no inhibition potential on major drug metabolizing CYP enzymes and transporters at clinical efficacious doses. Ocedurenone did not induce CYP1A2 and 3A4 activity in cultured human primary hepatocytes. Clinical DDI study indicated ocedurenone was well tolerated when administered as a single 0.5-mg dose both alone and with itraconazole or rifampin, and while itraconazole had a weak effect on ocedurenone's pharmacokinetics, rifampin had a significant effect reducing systemic exposures.

Flucloxacillin is a weak inducer of CYP3A4 in healthy adults and 3D spheroid of primary human hepatocytes.

Flucloxacillin is a widely used antibiotic. It is an agonist to the nuclear receptor Pregnane X Receptor (PXR) that regulates the expression of cytochrome P450 (CYP) enzymes. Treatment with flucloxacillin reduces warfarin efficacy and plasma concentrations of tacrolimus, voriconazole, and repaglinide. We conducted a translational study to investigate if flucloxacillin induces CYP enzymes. We also investigated if flucloxacillin induces its own metabolism as an autoinducer. We performed a randomized, unblinded, two-period, cross-over, clinical pharmacokinetic cocktail study. Twelve healthy adults completed the study. They ingested 1 g flucloxacillin three times daily for 31 days, and we assessed the full pharmacokinetics of the Basel cocktail drugs on days 0, 10, and 28, and plasma concentrations of flucloxacillin on days 0, 9, and 27. 3D spheroid of primary human hepatocytes (PHH) were exposed to flucloxacillin (concentration range: 0.15-250 μM) for 96 hours. Induction of mRNA expression, protein abundance, and enzyme activity of CYP enzymes were assessed. Flucloxacillin treatment reduced the metabolic ratio of midazolam (CYP3A4), (geometric mean ratio (GMR) 10 days (95% confidence interval (CI)): 0.75 (0.64-0.89)) and (GMR 28 days (95% CI): 0.72 (0.62-0.85)). Plasma concentrations of flucloxacillin did not change during 27 days of treatment. Flucloxacillin caused concentration-dependent induction of CYP3A4 and CYP2B6 (mRNA, protein, and activity), CYP2C9 (mRNA and protein), CYP2C19 (mRNA and activity), and CYP2D6 (activity) in 3D spheroid PHH. In conclusion, flucloxacillin is a weak inducer of CYP3A4, which may lead to clinically relevant drug-drug interactions for some narrow therapeutic range drugs that are substrates of CYP3A4.

Impact of Cytochrome P450 Enzymes on the Phase I Metabolism of Drugs

The cytochrome P450 (CYP) enzyme family is the major enzyme system catalyzing the phase I metabolism of xenobiotics, including pharmaceuticals and toxic compounds in the environment. A major part of the CYP-dependent xenobiotic metabolism is due to polymorphic and inducible enzymes, which may, quantitatively or qualitatively, alter or enhance drug metabolism and toxicity. Drug–drug interactions are major mechanisms caused by the inhibition and/or induction of CYP enzymes. Particularly, CYP monooxygenases catalyze hydroxylation reactions to form hydroxylated metabolites. The secondary metabolites are sometimes as active as the parent compound, or even more active. The aim of this review is to summarize some of the significative examples of common drugs used for the treatment of diverse diseases and underline the activity and/or toxicity of their metabolites.

Dicloxacillin-Warfarin Drug-Drug Interaction - A Register-Based Study and In Vitro Investigations in 3D Spheroid Primary Human Hepatocytes.

Dicloxacillin is used to treat staphylococcal infections and we have previously shown that dicloxacillin is an inducer of cytochrome P450 enzymes (CYPs). Here, we employed a translational approach to investigate the effect of a treatment with dicloxacillin on warfarin efficacy in Danish registries. Furthermore, we assessed dicloxacillin as an inducer of CYPs in vitro. We conducted a register-based study and analyzed international normalized ratio (INR) levels in chronic warfarin users before and after short- and long-term use of dicloxacillin (n=1023) and flucloxacillin (n=123). Induction of CYPs were investigated in a novel liver model of 3D spheroid primary human hepatocytes (PHHs) at the level of mRNA, and protein and enzyme activity. Short- and long-term dicloxacillin treatments decreased INR levels by -0.65 (95% CI: -0.57 to -0.74) and -0.76 (95% CI: -0.50 to -1.02), respectively. More than 90% of individuals experienced subtherapeutic INR levels (below 2) after long-term dicloxacillin treatment. Flucloxacillin decreased INR levels by -0.37 (95% CI: -0.14 to -0.60). In 3D spheroid PHHs, the maximal induction of CYP3A4 mRNA, protein and enzyme activity by dicloxacillin were 4.9-, 2.9- and 2.4-fold, respectively. Dicloxacillin also induced CYP2C9 mRNA by 1.7-fold. Dicloxacillin induces CYP enzymes and reduces the clinical efficacy of warfarin in patients. This effect is substantially exacerbated during long-term treatment with dicloxacillin. The in vitro results corroborated this drug-drug interaction and correlated to the clinical findings. Caution is warranted for warfarin patients that initiate dicloxacillin or flucloxacillin, especially for a long-term treatment of endocarditis.

3D Spheroid Primary Human Hepatocytes for Prediction of Cytochrome P450 and Drug Transporter Induction.

Primary human hepatocytes (PHHs) have been the gold standard in vitro model for the human liver and are crucial to predict hepatic drug-drug interactions. The aim of this work was to assess the utility of 3D spheroid PHHs to study induction of important cytochrome P450 (CYP) enzymes and drug transporters. 3D spheroid PHHs from three different donors were treated for four days with rifampicin, dicloxacillin, flucloxacillin, phenobarbital, carbamazepine, efavirenz, omeprazole or β-naphthoflavone. Induction of CYP1A1, CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, and transporters P-glycoprotein (P-gp)/ABCB1, multidrug resistance-associated protein 2 (MRP2)/ABCC2, ABCG2, organic cation transporter 1 (OCT1)/SLC22A1, SLC22A7, SLCO1B1 and SLCO1B3 were evaluated at mRNA and protein levels. Enzyme activity of CYP3A4, CYP2B6, CYP2C19 and CYP2D6 were also assessed. Induction of CYP3A4 protein and mRNA correlated well for all donors and compounds and had a maximal induction of 5- to 6-fold for rifampicin, which closely correlates to induction observed in clinical studies. Rifampicin induced the mRNA of CYP2B6 and CYP2C8 by 9- and 12-fold, while the protein levels of these CYPs reached 2- and 3-fold induction, respectively. Rifampicin induced CYP2C9 protein by 1.4-fold, while the induction of CYP2C9 mRNA was over 2-fold in all donors. Rifampicin induced ABCB1, ABCC2 and ABCG2 by 2-fold. In conclusion, 3D spheroid PHHs is a valid model to investigate mRNA and protein induction of hepatic drug-metabolizing enzymes and transporters, and this model provides a solid basis to study induction of CYPs and transporters, which translates to clinical relevance.

Hypothyroidism induced by antituberculosis drugs

Tuberculosis is an infectious disease that affects practically all organs, including the thyroid gland. In the same time, the hypofunction of the thyroid gland may increase susceptibility to infection with Mycobacterium tuberculosis. Antituberculosis treatment, especially with second-line drugs, can lead to hypothyroidism. It has been found that rifampicin, ethionamide, prothionamide and para-aminosalicylic acid are among the most common antituberculosis drugs responsible for the development of hypothyroidism. These preparations/agents can cause thyroid dysfunction by increasing the metabolism and clearance of thyroid hormones by inducing cytochrome P-450 enzymes, deregulating/ iodine uptake and synthesis of thyroid hormones, altering hormone receptor action and intracellular signal transduction. The treatment with these medications requires the monitoring of the function of the thyroid gland during the treatment, especially in the first 3 months, but also in the post-treatment period. The installation of clinical and/or subclinical hypothyroidism will require the use of appropriate doses of levothyroxine during antituberculosis treatment.

Metabolite Profiling of Clozapine in Patients Switching Versus Maintaining Treatment: A Retrospective Pilot Study.

Purpose/BackgroundPharmacokinetics may be of relevance for the risk of clozapine discontinuation. We compared metabolite profiles, accounting for smoking habits, in patients switching versus maintaining clozapine treatment at therapeutic concentrations.Methods/ProceduresAdult patients with clozapine serum levels above 1070 nmol/L (350 ng/mL) were retrospectively included from a Norwegian therapeutic drug monitoring service during 2018–2020. Inclusion criteria were (1) known smoking habits, (2) blood sample drawn within 10 to 30 hours after last clozapine intake, and (3) detectable levels of N-desmethylclozapine, clozapine-N-oxide, clozapine-5N-glucuronide, or clozapine-N+-glucuronide. Patients comedicated with cytochrome P450 enzyme inducers, inhibitors, or valproic acid were excluded. The high-resolution mass spectrometry assay enabled detection of 21 clozapine metabolites. Metabolite profiles were compared between patients switching treatment (switchers), measured as clozapine being replaced by another antipsychotic drug in blood samples, versus maintaining clozapine treatment (nonswitchers) during the study period.Findings/ResultsOf the 84 patients fulfilling the study criteria, 7 patients (8.3%) were identified as clozapine switchers. After correcting for smoking habits, the clozapine-5N-glucuronide/clozapine ratio was 69% lower (P < 0.001), while the clozapine-N+-glucuronide/clozapine-5N-glucuronide ratio was 143% higher (P = 0.026), respectively, in switchers versus nonswitchers. The other metabolite ratios did not significantly differ between switchers and nonswitchers.Implications/ConclusionsThe present study found a significantly reduced 5N-glucuronidation phenotype in patients switching from clozapine at therapeutic serum concentrations (>1070 nmol/L) to other antipsychotic drugs. This may indicate that glucuronidation, as a potential detoxification mechanism, is related to clozapine tolerability. However, the causality of this observation needs to be investigated in future studies with larger patient populations.

A review: drug-drug interactions of epithelial growth factor receptor-tyrosine kinase inhibitors

Mutations in the epithelial growth factor receptor (EGFR) is a driving factor that causes non-small cell lung carcinoma (NSCLC). The epithelial growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) is a crucial discovery in the treatment of lung cancer, particularly the efficacy of EGFR-TKIs is superior to that of the standard chemotherapy for patients with EGFR mutation-positive advanced NSCLC. Patients with NSCLC use EGFR-TKIs and other medications simultaneously is commonly seen, especially among those with comorbidities, which increases the risk of drug-drug interactions (DDIs) of EGFR-TKIs. The most common mechanisms underlying the DDIs of EGFR-TKIs are modulations of cytochrome P450 (CYP) and drug transporters [including P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP)], as well as gastrointestinal acid-inhibitory drugs [proton pump inhibitors (PPIs) and H(2) receptor antagonists (H(2)RA)]. Inhibitors or inducers of CYP enzymes and drug transporters can inhibit or accelerate the metabolism of EGFR-TKIs, which increase or reduce the exposure of EGFR-TKIs, thereby affect the efficacy and safety of EGFR-TKIs. In addition, PPIs or H(2)RA can decrease the solubility, bioavailability and efficacy of EGFR-TKIs. This review summarizes the mechanisms of DDIs of gefitinib, erlotinib, icotinib, afatinib, dacomitinib and osimertinib; the management recommendations for DDIs of those EGFR-TKIs from the Chinese and global guideline, as well as from the recent pre-clinical and clinical studies, which provide the reference and evidence for managing the combination therapies of EGFR-TKIs and other medications in clinics.

Retrospective Review of ART Regimens in HIV-Positive to HIV-Positive Kidney Transplant Recipients

IntroductionThe management of complex interactions between antiretroviral therapy (ART) and calcineurin inhibitor (CNI) immunosuppression regimens in HIV-positive to HIV-positive renal transplant recipients can be challenging. Literature describing ART regimens and indications for regimen switching in these patients is limited.MethodsThis retrospective review included 53 HIV-positive to HIV-positive renal transplant recipients. Data on ART regimens, reasons for ART switching, and timing of switches were described from day of transplant to study endpoint (end of study date, death, or graft failure). The association between rejection and ART regimen (protease inhibitor [PI] -based vs. non-PI-based regimen) was analyzed using negative binomial regression.ResultsThere were a total of 46 switches in 31 of 53 patients (58%). Protocol switches (n = 17 of 46, 37%) accounted for most switches, of which the majority were from non-nucleoside reverse transcriptase inhibitors (NNRTIs) to PIs. Other common reasons for switching include cytochrome P450 enzyme induction from efavirenz (EFV) (9 of 46, 20%), tenofovir disoproxil fumarate (TDF) nephrotoxicity (8 of 46, 17%) or side effects (6 of 46, 13%). Of the 46 switches, nearly half (n = 21, 46%) occurred during the transplant admission period, and approximately two-thirds (n = 28, 62%) were during the first year post-transplantation. There was an association between rejection and being maintained on a PI-based regimen (incidence rate ratio 2.77 (95% confidence interval 1.03–7.48), P = 0.044).ConclusionDespite frequent switching of ART regimens, HIV viral loads remained supressed and graft function remained stable in most HIV-positive kidney transplant recipients in our cohort. There was however a concerning signal for increased rejection rates in those on a PI-based regimen.

Candidate Proficiency Test Chemicals to Address Industrial Chemical Applicability Domains for in vitro Human Cytochrome P450 Enzyme Induction.

Cytochrome P450 (CYP) enzymes play a key role in the metabolism of both xenobiotics and endogenous chemicals, and the activity of some CYP isoforms are susceptible to induction and/or inhibition by certain chemicals. As CYP induction/inhibition can bring about significant alterations in the level of in vivo exposure to CYP substrates and metabolites, CYP induction/inhibition data is needed for regulatory chemical toxicity hazard assessment. On the basis of available human in vivo pharmaceutical data, a draft Organisation for Economic Co-operation and Development Test Guideline (TG) for an in vitro CYP HepaRG test method that is capable of detecting the induction of four human CYPs (CYP1A1/1A2, 2B6, and 3A4), has been developed and validated for a set of pharmaceutical proficiency chemicals. However to support TG adoption, further validation data was requested to demonstrate the ability of the test method to also accurately detect CYP induction mediated by industrial and pesticidal chemicals, together with an indication on regulatory uses of the test method. As part of “GOLIATH”, a European Union Horizon-2020 funded research project on metabolic disrupting chemical testing approaches, work is underway to generate supplemental validated data for an additional set of chemicals with sufficient diversity to allow for the approval of the guideline. Here we report on the process of proficiency chemical selection based on a targeted literature review, the selection criteria and considerations required for acceptance of proficiency chemical selection for OECD TG development (i.e. structural diversity, range of activity, relevant chemical sectors, global restrictions etc). The following 13 proposed proficiency chemicals were reviewed and selected as a suitable set for use in the additional validation experiments: tebuconazole, benfuracarb, atrazine, cypermethrin, chlorpyrifos, perfluorooctanoic acid, bisphenol A, N,N-diethyl-m-toluamide, benzo-[a]-pyrene, fludioxonil, malathion, triclosan, and caffeine. Illustrations of applications of the test method in relation to endocrine disruption and non-genotoxic carcinogenicity are provided.

Risk Assessment of the Pesticide Coragen 20 SC with the Active Substance Chlorantraniliprole

Coragen 20 SC is a new product in Norway containing the active substance chlorantraniliprole. It is applied for use in apples against codling moth (Cydia pomonella), apple fruit moth (Argyresthia conjugella) and free leaf living larvae. The Norwegian Scientific Committee for Food Safety (VKM) was asked by the Norwegian Food Safety Authority to perform a risk assessment on human health, environmental fate and ecotoxicological of the active substance and the product. The risk assessment of the product was approved at a meeting 11th of May 2010 by VKMs Scientific Panel on Pesticides (Panel 2). VKMs Panel 2 concludes as following: The product and the active substance have low acute oral, dermal and inhalation toxicities. Both are non-irritating to the skin, and no allergenic potential by skin contact were shown. Coragen was non-irritating to the eyes, while chlorantraniliprole showed a weak irritating potential. Chlorantraniliprole is not shown to have any genotoxic or carcinogenic potential, or to be teratogenic or toxic to the reproduction of female animals. The potential for testicular toxicity of chlorantraniliprole is unclear because the study design and the limited number of young dogs (2/sex/group) do not provide basis for a firm conclusion. No particular target organ for toxicity in any species in the sub-chronic and chronic toxicity studies was seen. The observed dose- and time dependent increased degree of microvesiculation in the zona fasiculata of the adrenal cortex in male rats, is however of uncertain biological significance. All test species (rat, mice, dog) showed physiological adaption to chlorantraniliprole administration (increased liver metabolism with induction of cytochrome P450 enzymes) which was manifested as increased liver weight and hepatocellular hypertrophy. In the chronic toxicity study in mice, the increased liver weight and hepatocellular hypertophy was accompanied with eosinofilic foci, which was assessed as an adverse effect. The no observed effect level (NOAEL) derived from this study serves as basis for calculations of values for acceptable daily intake (ADI) and acceptable operator exposure level (AOEL). &#x0D; In Panel 2‘s opinion a sub-chronic study (90 days) with the technical material (E2Y45-282) including relevant concentration of the impurity IN-G2S78 should be performed. This would bring information on possible influence of the impurity on the toxicological profile of the technical material, and consequently on the assessment of the NOAELs in the various toxic studies. &#x0D; The estimated risk for operator and for bystanders or for workers re-entering treated crops is assessed as minimal. &#x0D; Chlorantraniliprole is persistent in soil with half live of about 1 year. The long half life indicates high potential for accumulation in soil after repeated use, which is confirmed by both model simulations and field studies. The Panel considers field data from the south of Europe not to be relevant for the Nordic conditions based on different climate conditions and soil properties contributing in different directions.&#x0D; The Panel considers that the existing documentation is not sufficient for a firm conclusion on the use of normalised field data for modelling purposes. However, the substance is persistent and expected to accumulate in soil. The Panel concludes that there is minimal risk for toxic effects on mammals, birds, bees, and microorganisms in soil due to chlorantraniliprole exposure with the proposed exposure regime. Panel concludes that there is “very high risk” for effects on in-field non target arthropods from chlorantraniliprole exposure. &#x0D; For soil living invertebrates, earthworms seem rather insensitive to chlorantraniliprole and the Panel considers the toxic effects to be minimal. Panel considers the risk for toxic effects on soil living arthropods to be high. Crustaceans and insects larvae are the aquatic organisms most sensitive to chlorantraniliprole. The Panel concludes that there is a minimal risk of toxic effects on aquatic organisms due to exposure to chlorantraniliprole with the proposed application regime provided that a buffer zone of 30 m to surface water is applied.