CYP Induction-Mediated Drug Interactions: in Vitro Assessment and Clinical Implications

In Situ Self-Assembling Liver Spheroids with Synthetic Nanoscaffolds for Preclinical Drug Screening Applications

Drug-induced liver injury (DILI) is one of the most common reasons for acute liver failure and a major reason for the withdrawal of medications from the market. There is a growing need for advanced in vitro liver models that can effectively recapitulate hepatic function, offering a robust platform for preclinical drug screening applications. Here, we explore the potential of self-assembling liver spheroids in the presence of electrospun and cryomilled poly(caprolactone) (PCL) nanoscaffolds for use as a new preclinical drug screening tool. This study investigated the extent to which nanoscaffold concentration may have on spheroid size and viability and liver-specific biofunctionality. The efficacy of our model was further validated using a comprehensive dose-dependent acetaminophen toxicity protocol. Our findings show the strong potential of PCL-based nanoscaffolds to facilitate in situ self-assembly of liver spheroids with sizes under 350 μm. The presence of the PCL-based nanoscaffolds (0.005 and 0.01% w/v) improved spheroid viability and the secretion of critical liver-specific biomarkers, namely, albumin and urea. Liver spheroids with nanoscaffolds showed improved drug-metabolizing enzyme activity and greater sensitivity to acetaminophen compared to two-dimensional monolayer cultures and scaffold-free liver spheroids. These promising findings highlight the potential of our nanoscaffold-based liver spheroids as an in vitro liver model for drug-induced hepatotoxicity and drug screening.

Effect of P. corylifolia on the pharmacokinetic profile of tofacitinib and the underlying mechanism

This work aimed to explore the mechanisms underlying the interaction of the active furanocoumarins in P. corylifolia on tofacitinib both in vivo and in vitro. The concentration of tofacitinib and its metabolite M8 was determined using UPLC-MS/MS. The peak area ratio of M8 to tofacitinib was calculated to compare the inhibitory ability of furanocoumarin contained in the traditional Chinese medicine P. corylifolia in rat liver microsomes (RLMs), human liver microsomes (HLMs) and recombinant human CYP3A4 (rCYP3A4). We found that bergapten and isopsoralen exhibited more significant inhibitory activity in RLMs than other furanocoumarins. Bergapten and isopsoralen were selected to investigate tofacitinib drug interactions in vitro and in vivo. Thirty rats were randomly allocated into 5 groups (n = 6): control (0.5% CMC-Na), low-dose bergapten (20 mg/kg), high-dose bergapten (50 mg/kg), low-dose isopsoralen (20 mg/kg) and ketoconazole. 10 mg/kg of tofacitinib was orally intervented to each rat and the concentration level of tofacitinib in the rats were determined by UPLC-MS/MS. More imporrantly, the results showed that bergapten and isopsoralen significantly inhibited the metabolism of tofacitinib metabolism. The AUC(0-t), AUC(0-∞), MRT(0-t), MRT(0-∞) and Cmax of tofacitinib increased in varying degrees compared with the control group (all p < 0.05), but CLz/F decreased in varying degrees (p < 0.05) in the different dose bergapten group and isopsoralen group. Bergapten, isopsoralen and tofacitinib exhibit similar binding capacities with CYP3A4 by AutoDock 4.2 software, confirming that they compete for tofacitinib metabolism. P. corylifolia may considerably impact the metabolism of tofacitinib, which can provide essential information for the accurate therapeutic application of tofacitinib.

Comparative In Vitro Study of the Cytotoxic Effects of Doxorubicin's Main Metabolites on Cardiac AC16 Cells Versus the Parent Drug

Doxorubicin (DOX; also known as adriamycin) serves as a crucial antineoplastic agent in cancer treatment; however, its clinical utility is hampered by its' intrinsic cardiotoxicity. Although most DOX biotransformation occurs in the liver, a comprehensive understanding of the impact of DOX biotransformation and its' metabolites on its induced cardiotoxicity remains to be fully elucidated. This study aimed to explore the role of biotransformation and DOX's main metabolites in its induced cardiotoxicity in human differentiated cardiac AC16 cells. A key discovery from our study is that modulating metabolism had minimal effects on DOX-induced cytotoxicity: even so, metyrapone (a non-specific inhibitor of cytochrome P450) increased DOX-induced cytotoxicity at 2 µM, while diallyl sulphide (a CYP2E1 inhibitor) decreased the 1 µM DOX-triggered cytotoxicity. Then, the toxicity of the main DOX metabolites, doxorubicinol [(DOXol, 0.5 to 10 µM), doxorubicinone (DOXone, 1 to 10 µM), and 7-deoxydoxorubicinone (7-DeoxyDOX, 1 to 10 µM)] was compared to DOX (0.5 to 10 µM) following a 48-h exposure. All metabolites evaluated, DOXol, DOXone, and 7-DeoxyDOX caused mitochondrial dysfunction in differentiated AC16 cells, but only at 2 µM. In contrast, DOX elicited comparable cytotoxicity, but at half the concentration. Similarly, all metabolites, except 7-DeoxyDOX impacted on lysosomal ability to uptake neutral red. Therefore, the present study showed that the modulation of DOX metabolism demonstrated minimal impact on its cytotoxicity, with the main metabolites exhibiting lower toxicity to AC16 cardiac cells compared to DOX. In conclusion, our findings suggest that metabolism may not be a pivotal factor in mediating DOX's cardiotoxic effects.

A Review of CYP-Mediated Drug Interactions: Mechanisms and In Vitro Drug-Drug Interaction Assessment

Drug metabolism is a major determinant of drug concentrations in the body. Drug-drug interactions (DDIs) caused by the co-administration of multiple drugs can lead to alteration in the exposure of the victim drug, raising safety or effectiveness concerns. Assessment of the DDI potential starts with in vitro experiments to determine kinetic parameters and identify risks associated with the use of comedication that can inform future clinical studies. The diverse range of experimental models and techniques has significantly contributed to the examination of potential DDIs. Cytochrome P450 (CYP) enzymes are responsible for the biotransformation of many drugs on the market, making them frequently implicated in drug metabolism and DDIs. Consequently, there has been a growing focus on the assessment of DDI risk for CYPs. This review article provides mechanistic insights underlying CYP inhibition/induction and an overview of the in vitro assessment of CYP-mediated DDIs.

The Effect of Vitamin D3 and Valproic Acid on the Maturation of Human-Induced Pluripotent Stem Cell-Derived Enterocyte-Like Cells

Cytochrome P450 3A4 (CYP3A4) is involved in first-pass metabolism in the small intestine and is heavily implicated in oral drug bioavailability and pharmacokinetics. We previously reported that vitamin D3 (VD3), a known CYP enzyme inducer, induces functional maturation of iPSC-derived enterocyte-like cells (iPSC-ent). Here, we identified a Notch activator and CYP modulator valproic acid (VPA), as a promotor for the maturation of iPSC-ent. We performed bulk RNA sequencing to investigate the changes in gene expression during the differentiation and maturation periods of these cells. VPA potentiated gene expression of key enterocyte markers ALPI, FABP2, and transporters such as SULT1B1. RNA-sequencing analysis further elucidated several function-related pathways involved in fatty acid metabolism, significantly upregulated by VPA when combined with VD3. Particularly, VPA treatment in tandem with VD3 significantly upregulated key regulators of enterohepatic circulation, such as FGF19, apical bile acid transporter SLCO1A2 and basolateral bile acid transporters SLC51A and SLC51B. To sum up, we could ascertain the genetic profile of our iPSC-ent cells to be specialized toward fatty acid absorption and metabolism instead of transporting other nutrients, such as amino acids, with the addition of VD3 and VPA in tandem. Together, these results suggest the possible application of VPA-treated iPSC-ent for modelling enterohepatic circulation.

Autophagy (but not metabolism) is a key event in mitoxantrone-induced cytotoxicity in differentiated AC16 cardiac cells

Mitoxantrone (MTX) is an antineoplastic agent used to treat advanced breast cancer, prostate cancer, acute leukemia, lymphoma and multiple sclerosis. Although it is known to cause cumulative dose-related cardiotoxicity, the underlying mechanisms are still poorly understood. This study aims to compare the cardiotoxicity of MTX and its' pharmacologically active metabolite naphthoquinoxaline (NAPHT) in an in vitro cardiac model, human-differentiated AC16 cells, and determine the role of metabolism in the cardiotoxic effects. Concentration-dependent cytotoxicity was observed after MTX exposure, affecting mitochondrial function and lysosome uptake. On the other hand, the metabolite NAPHT only caused concentration-dependent cytotoxicity in the MTT reduction assay. When assessing the effect of different inhibitors/inducers of metabolism, it was observed that metyrapone (a cytochrome P450 inhibitor) and phenobarbital (a cytochrome P450 inducer) slightly increased MTX cytotoxicity, while 1-aminobenzotriazole (a suicide cytochrome P450 inhibitor) decreased fairly the MTX-triggered cytotoxicity in differentiated AC16 cells. When focusing in autophagy, the mTOR inhibitor rapamycin and the autophagy inhibitor 3-methyladenine exacerbated the cytotoxicity caused by MTX and NAPHT, while the autophagy blocker, chloroquine, partially reduced the cytotoxicity of MTX. In addition, we observed a decrease in p62, beclin-1, and ATG5 levels and an increase in LC3-II levels in MTX-incubated cells. In conclusion, in our in vitro model, neither metabolism nor exogenously given NAPHT are major contributors to MTX toxicity as seen by the residual influence of metabolism modulators used on the observed cytotoxicity and by NAPHT's low cytotoxicity profile. Conversely, autophagy is involved in MTX-induced cytotoxicity and MTX seems to act as an autophagy inducer, possibly through p62/LC3-II involvement.

Genetic polymorphism related to ethambutol outcomes and susceptibility to toxicity

The World Health Organization (WHO) stated that ensuring access to effective and optimal treatment is a key component to eradicate tuberculosis (TB) through the End TB Strategy. Personalized medicine that depends on the genetic profile of an individual is one way to optimize treatment. It is necessary because of diverse drug responses related to the variation in human DNA, such as single-nucleotide polymorphisms (SNPs). Ethambutol (EMB) is a drug widely used as the treatment for Mycobacterium Tuberculosis (Mtb) and/non-tuberculous mycobacteria and has become a potential supplementary agent for a treatment regimen of multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB. In human genetic polymorphism studies of anti-tuberculosis, the majority focus on rifampicin or isoniazid, which discuss polymorphisms related to their toxicity. Whereas there are few studies on EMB, the incidence of EMB toxicity is lower than that of other first-line anti-TB drugs. To facilitate personalized medicine practice, this article summarizes the genetic polymorphisms associated with alterations in the pharmacokinetic profile, resistance incidence, and susceptibility to EMB toxicity. This study includes 131 total human studies from 17 articles, but only eight studies that held in the low-middle income country (LMIC), while the rest is research conducted in developed countries with high incomes. Personalized medicine practices are highly recommended to maintain and obtain the optimal therapeutic effect of EMB.

Beyond the Michaelis-Menten: Accurate Prediction of Drug Interactions through Cytochrome P450 3A4 Induction

The US Food and Drug Administration (FDA) guidance has recommended several model-based predictions to determine potential drug-drug interactions (DDIs) mediated by cytochrome P450 (CYP) induction. In particular, the ratio of substrate area under the plasma concentration-time curve (AUCR) under and not under the effect of inducers is predicted by the Michaelis-Menten (MM) model, where the MM constant ( K m $$ {K}_{\mathrm{m}} $$ ) of a drug is implicitly assumed to be sufficiently higher than the concentration of CYP enzymes that metabolize the drug ( E T $$ {E}_{\mathrm{T}} $$ ) in both the liver and small intestine. Furthermore, the fraction absorbed from gut lumen ( F a $$ {F}_{\mathrm{a}} $$ ) is also assumed to be one because F a $$ {F}_{\mathrm{a}} $$ is usually unknown. Here, we found that such assumptions lead to serious errors in predictions of AUCR. To resolve this, we propose a new framework to predict AUCR. Specifically, F a $$ {F}_{\mathrm{a}} $$ was re-estimated from experimental permeability values rather than assuming it to be one. Importantly, we used the total quasi-steady-state approximation to derive a new equation, which is valid regardless of the relationship between K m $$ {K}_{\mathrm{m}} $$ and E T $$ {E}_{\mathrm{T}} $$ , unlike the MM model. Thus, our framework becomes much more accurate than the original FDA equation, especially for drugs with high affinities, such as midazolam or strong inducers, such as rifampicin, so that the ratio between K m $$ {K}_{\mathrm{m}} $$ and E T $$ {E}_{\mathrm{T}} $$ becomes low (i.e., the MM model is invalid). Our work greatly improves the prediction of clinical DDIs, which is critical to preventing drug toxicity and failure.

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.

In vitro evaluation suggests fenfluramine and norfenfluramine are unlikely to act as perpetrators of drug interactions

Studies support the safety and efficacy of fenfluramine (FFA) as an antiseizure medication (ASM) in Dravet syndrome, Lennox-Gastaut syndrome, or CDKL5 deficiency disorder, all pharmacoresistant developmental and epileptic encephalopathies. However, drug-drug interactions with FFA in multi-ASM regimens have not been fully investigated. We characterized the perpetrator potential of FFA and its active metabolite, norfenfluramine (nFFA), in vitro by assessing cytochrome P450 (CYP450) inhibition in human liver microsomes, CYP450 induction in cultured human hepatocytes, and drug transporter inhibition potential in permeability or cellular uptake assays. Mean plasma unbound fraction was ~50% for both FFA and nFFA, with no apparent concentration dependence. FFA and nFFA were direct in vitro inhibitors of CYP2D6 (IC₅₀ , 4.7 and 16 µM, respectively) but did not substantially inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, or CYP3A4/5. No time- or metabolism-dependent CYP450 inhibition occurred. FFA and nFFA did not induce CYP1A2; both induced CYP2B6 (up to 2.8-fold and up to 2.0-fold, respectively) and CYP3A4 (1.9- to 3.0-fold and 3.6- to 4.8-fold, respectively). Mechanistic static pharmacokinetic models predicted that neither CYP450 inhibition nor induction was likely to be clinically relevant at doses typically used for seizure reduction (ratio of area under curve [AUCR] for inhibition <1.25; AUCR for induction >0.8). Transporters OCT2 and MATE1 were inhibited by FFA (IC₅₀ , 19.8 and 9.0 μM) and nFFA (IC₅₀ , 5.2 and 4.6 μM) at concentrations higher than clinically achievable; remaining transporters were not inhibited. Results suggest that FFA and nFFA are unlikely drug-drug interaction perpetrators at clinically relevant doses of FFA (0.2-0.7 mg/kg/day).

Fucoxanthin Is a Potential Therapeutic Agent for the Treatment of Breast Cancer

Breast cancer (BC) is one of the most common cancers diagnosed and the leading cause of cancer-related death in women. Although there are first-line treatments for BC, drug resistances and adverse events have been reported. Given the incidence of BC keeps increasing, seeking novel therapeutics is urgently needed. Fucoxanthin (Fx) is a dietary carotenoid commonly found in seaweeds and diatoms. Both in vitro and in vivo studies show that Fx and its deacetylated metabolite fucoxanthinol (Fxol) inhibit and prevent BC growth. The NF-κB signaling pathway is considered the major pathway contributing to the anti-proliferation, anti-angiogenesis and pro-apoptotic effects of Fx and Fxol. Other signaling molecules such as MAPK, MMP2/9, CYP and ROS are also involved in the anti-cancer effects by regulating the tumor microenvironment, cancer metastasis, carcinogen metabolism and oxidation. Besides, Fx also possesses anti-obesity effects by regulating UCP1 levels and lipid metabolism, which may help to reduce BC risk. More importantly, mounting evidence demonstrates that Fx overcomes drug resistance. This review aims to give an updated summary of the anti-cancer effects of Fx and summarize the underlying mechanisms of action, which will provide novel strategies for the development of Fx as an anti-cancer therapeutic agent.

Ways to Improve Insights into Clindamycin Pharmacology and Pharmacokinetics Tailored to Practice

Given the increase in bacterial resistance and the decrease in the development of new antibiotics, the appropriate use of old antimicrobials has become even more compulsory. Clindamycin is a lincosamide antibiotic approved for adults and children as a drug of choice for systemic treatment of staphylococcal, streptococcal, and gram-positive anaerobic bacterial infections. Because of its profile and high bioavailability, it is commonly used as part of an oral multimodal alternative for prolonged parenteral antibiotic regimens, e.g., to treat bone and joint or prosthesis-related infections. Clindamycin is also frequently used for (surgical) prophylaxis in the event of beta-lactam allergy. Special populations (pediatrics, pregnant women) have altered cytochrome P450 (CYP)3A4 activity. As clindamycin is metabolized by the CYP3A4/5 enzymes to bioactive N-demethyl and sulfoxide metabolites, knowledge of the potential relevance of the drug’s metabolites and disposition in special populations is of interest. Furthermore, drug–drug interactions derived from CYP3A4 inducers and inhibitors, and the data on the impact of the disease state on the CYP system, are still limited. This narrative review provides a detailed survey of the currently available literature on pharmacology and pharmacokinetics and identifies knowledge gaps (special patient population, drug–drug, and drug–disease interactions) to describe a research strategy for precision medicine.

Physiologically Based Pharmacokinetic (PBPK) Modeling of Clopidogrel and Its Four Relevant Metabolites for CYP2B6, CYP2C8, CYP2C19, and CYP3A4 Drug–Drug–Gene Interaction Predictions

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 AUC_last and 19/19 predicted DGI C_max ratios within 2-fold of their observed values. Furthermore, DDIs involving bupropion, omeprazole, montelukast, pioglitazone, repaglinide, and rifampicin showed 13/13 predicted DDI AUC_last and 13/13 predicted DDI C_max ratios within 2-fold of their observed ratios. After publication, the model will be made publicly accessible in the Open Systems Pharmacology repository.

Vitamin D levels do not cause vitamin-drug interactions with dexamethasone or dasatinib in mice

Vitamin D3 (VD3) induces intestinal CYP3A that metabolizes orally administered anti-leukemic chemotherapeutic substrates dexamethasone (DEX) and dasatinib potentially causing a vitamin-drug interaction. To determine the impact of VD3 status on systemic exposure and efficacy of these chemotherapeutic agents, we used VD3 sufficient and deficient mice and performed pharmacokinetic and anti-leukemic efficacy studies. Female C57BL/6J and hCYP3A4 transgenic VD3 deficient mice had significantly lower duodenal (but not hepatic) mouse Cyp3a11 and hCYP3A4 expression compared to VD3 sufficient mice, while duodenal expression of Mdr1a, Bcrp and Mrp4 were significantly higher in deficient mice. When the effect of VD3 status on DEX systemic exposure was compared following a discontinuous oral DEX regimen, similar to that used to treat pediatric acute lymphoblastic leukemia patients, male VD3 deficient mice had significantly higher mean plasma DEX levels (31.7 nM) compared to sufficient mice (12.43 nM) at days 3.5 but not at any later timepoints. Following a single oral gavage of DEX, there was a statistically, but not practically, significant decrease in DEX systemic exposure in VD3 deficient vs. sufficient mice. While VD3 status had no effect on oral dasatinib's area under the plasma drug concentration-time curve, VD3 deficient male mice had significantly higher dasatinib plasma levels at t = 0.25 hr. Dexamethasone was unable to reverse the poorer survival of VD3 sufficient vs. deficient mice to BCR-ABL leukemia. In conclusion, although VD3 levels significantly altered intestinal mouse Cyp3a in female mice, DEX plasma exposure was only transiently different for orally administered DEX and dasatinib in male mice. Likewise, the small effect size of VD3 deficiency on single oral dose DEX clearance suggests that the clinical significance of VD3 levels on DEX systemic exposure are likely to be limited.

Benzo[a]pyrene-Induced Genotoxicity in Rats Is Affected by Co-Exposure to Sudan I by Altering the Expression of Biotransformation Enzymes

The environmental pollutant benzo[a]pyrene (BaP) is a human carcinogen that reacts with DNA after metabolic activation catalysed by cytochromes P450 (CYP) 1A1 and 1B1 together with microsomal epoxide hydrolase. The azo dye Sudan I is a potent inducer of CYP1A1/2. Here, Wistar rats were either treated with single doses of BaP (150 mg/kg bw) or Sudan I (50 mg/kg bw) alone or with both compounds in combination to explore BaP-derived DNA adduct formation in vivo. Using ³²P-postlabelling, DNA adducts generated by BaP-7,8-dihydrodiol-9,10-epoxide were found in livers of rats treated with BaP alone or co-exposed to Sudan I. During co-exposure to Sudan I prior to BaP treatment, BaP-DNA adduct levels increased 2.1-fold in comparison to BaP treatment alone. Similarly, hepatic microsomes isolated from rats exposed to Sudan I prior to BaP treatment were also the most effective in generating DNA adducts in vitro with the activated metabolites BaP-7,8-dihydrodiol or BaP-9-ol as intermediates. DNA adduct formation correlated with changes in the expression and/or enzyme activities of CYP1A1, 1A2 and 1B1 in hepatic microsomes. Thus, BaP genotoxicity in rats in vivo appears to be related to the enhanced expression and/or activity of hepatic CYP1A1/2 and 1B1 caused by exposure of rats to the studied compounds. Our results indicate that the industrially employed azo dye Sudan I potentiates the genotoxicity of the human carcinogen BaP, and exposure to both substances at the same time seems to be hazardous to humans.

Classification of drugs for evaluating drug interaction in drug development and clinical management

During new drug development, clinical drug interaction studies are carried out in accordance with the mechanism of potential drug interactions evaluated by in vitro studies. The obtained information should be provided efficiently to medical experts through package inserts and various information materials after the drug's launch. A recently updated Japanese guideline presents general procedures that are considered scientifically valid at the present moment. In this review, we aim to highlight the viewpoints of the Japanese guideline and enumerate drugs that were involved or are anticipated to be involved in evident pharmacokinetic drug interactions and classify them by their clearance pathway and potential intensity based on systematic reviews of the literature. The classification would be informative for designing clinical studies during the development stage, and the appropriate management of drug interactions in clinical practice.

An improved TK-NOG mouse as a novel platform for humanized liver that overcomes limitations in both male and female animals

We developed a novel immunodeficient NOG mouse expressing HSVtk mutant clone 30 cDNA under the control of mouse transthyretin gene enhancer/promoter (NOG-TKm30) to acquire fertility in males and high inducibility of liver injury in females. Maximum human albumin levels (approx. 15 mg/mL plasma) in both male and female NOG-TKm30 mice engrafted with human hepatocytes (humanized liver mice) were observed 8-12 weeks after transplantation. Immunohistochemical analyses revealed abundant expression of major human cytochrome P450 (CYP) enzymes (CYP1A2, CYP2C9, CYP2D6, CYP2E1, and CYP3A4) in reconstituted liver with original zonal distribution. In vivo drug-drug interactions were observed in humanized liver mice as decreased area under the curve of midazolam (CYP3A4/5 substrate) and omeprazole (CYP3A4/5 and CYP2C19 substrate) after oral administration of rifampicin. Furthermore, we developed a pregnant model for evaluating prenatal exposure to drugs. The detection of thalidomide metabolites in the fetuses of pregnant humanized liver mice indicates that the novel TK model can be used for developmental toxicity studies requiring the assessment of human drug metabolism. These results suggest that the limitations of traditional TK-NOG mice can be addressed using NOG-TKm30 mice, which constitute a novel platform for humanized liver for both in vivo and in vitro studies.

Acute Toxicity and DNA Instability Induced by Exposure to Low Doses of Triclosan and Phthalate DEHP, and Their Combinations, in vitro

Triclosan (TCS) is an antimicrobial agent widely used in personal care products (PCP) and the di-(2-ethyl hydroxy-phthalate) (DEHP) is a chemical compound derived from phthalic acid, used in medical devices and plastic products with polyvinyl chloride (PVCs). As result of their extensive use, TCS and DEHP have been found in the environment and previous studies demonstrated the association between their exposure and toxic effects, mostly in aquatic organisms, but there is a shortage in the literature concerning the exposure of TCS and DEHP in human cells. The aim of the present study was to assess the impact of exposure to TCS and DEHP, as well as their combinations, on biomarkers related to acute toxicity and DNA instability, in HepG2 cells, by use of cytokinesis-block micronucleus cytome (CBMNCyt) assay. For that, the cultures were exposed to TCS, DEHP and combinations at doses of 0.10, 1.0, and 10 μM for the period of 4 h and the parameters related to DNA damage (i.e., frequencies of micronuclei (MN) and nuclear buds (NBUDs), to cell division (i.e., nuclear division index (NDI) and nuclear division cytotoxic index (NDCI) and to cell death (apoptotic and necrotic cells) were scored. Clear mutagenic effects were seen in cells treated with TCS, DEHP at doses of 1.0 and 10 μM, but no combined effects were observed when the cells were exposed to the combinations of TCS + DEHP. On the other hand, the combination of the toxicants significantly increased the frequencies of apoptotic and necrotic cells, as well as induced alterations of biomarkers related to cell viability (NDI and NDCI), when compared to the groups treated only with TCS or DEHP. Taken together, the results showed that TCS and DEHP are also able to induce acute toxicity and DNA damage in human cells.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

Evaluation of Methods to Assess CYP3A Induction Risk in Clinical Practice Using in Vitro Induction Parameters

Established guidelines have recommended a number of methods based on in vitro data to assess the CYP3A induction risk of new chemical entities in clinical practice. In this study, we evaluated the predictability of various assessment methods. We collected in vitro parameters from a variety of literature that includes data on 19 batches of hepatocytes. Clinical CYP3A induction was predicted using 3 direct approaches-the fold-change, basic model, and mechanistic static models-as well as 5 correlation approaches, including the relative induction score (RIS) and the relative factor (RF) method. These predictions were then compared with data from 30 clinical inductions. Collected in vitro parameters varied greatly between hepatocyte batches. Direct assessment methods using fixed cut-off values provided a lot of false predictions due to hepatocyte variability, which can overlook induction risk or lead to needless clinical drug-drug interaction (DDI) studies. On the other hand, correlation methods with the cut-off values set for each batch of hepatocytes accurately predicted the induction risk. Among these, the AUC_u/inducer concentrations for half the maximum induction (EC₅₀) and the RF methods which use the area under the curve (AUC) of the unbound inducers for calculating induction potential showed an especially good correlation with clinical induction. Correlation methods were better at predicting clinical induction risk than the other methods, regardless of hepatocyte variability. The AUC_u/EC₅₀ and the RF methods in particular had a small number of false predictions, and can therefore be used to assess induction risk along with the other correlation methods recommended in guidelines.

Presence or absence of microbiome modulates the response of mice organism to administered drug nabumetone

The gut microbiota provides a wide range of beneficial functions for the host, and has an immense effect on the host's health status. The presence of microbiome in the gut may often influence the effect of an orally administered drug. Molecular mechanisms of this process are however mostly unclear. We investigated how the effect of a nonsteroidal drug nabumetone on expression of drug metabolizing enzymes (DMEs) in mice intestine and liver is changed by the presence of microbiota, here, using the germ free (GF) and specific pathogen free (SPF) BALB/c mice. First, we have found in a preliminary experiment that in the GF mice there is a tendency to increase bioavailability of the active form of nabumetone, which we have found now to be possibly influenced by differences in expression of DMEs in the GF and SPF mice. Indeed, we have observed that the expression of the most of selected cytochromes P450 (CYPs) was significantly changed in the small intestine of GF mice compared to the SPF ones. Moreover, orally administered nabumetone itself altered the expression of some CYPs and above all, in different ways in the GF and SPF mice. In the GF mice, the expression of the DMEs (CYP1A) responsible for the formation of active form of the drug are significantly increased in the small intestine and liver after nabumetone application. These results highlight the importance of gut microbiome in processes involved in drug metabolism in the both gastrointestinal tract and in the liver with possible clinical relevance.

A Simple Toxicokinetic Model Exhibiting Complex Dynamics and Nonlinear Exposure Response

Uncertainty in model predictions of exposure response at low exposures is a problem for risk assessment. A particular interest is the internal concentration of an agent in biological systems as a function of external exposure concentrations. Physiologically based pharmacokinetic (PBPK) models permit estimation of internal exposure concentrations in target tissues but most assume that model parameters are either fixed or instantaneously dose-dependent. Taking into account response times for biological regulatory mechanisms introduces new dynamic behaviors that have implications for low-dose exposure response in chronic exposure. A simple one-compartment simulation model is described in which internal concentrations summed over time exhibit significant nonlinearity and nonmonotonicity in relation to external concentrations due to delayed up- or downregulation of a metabolic pathway. These behaviors could be the mechanistic basis for homeostasis and for some apparent hormetic effects.

Inducibility of cytochrome P450-mediated 7-methoxycoumarin-O-demethylase activity in zebrafish (Danio rerio) embryos

The zebrafish (Danio rerio) embryo has increasingly been used as an alternative model in human and environmental toxicology. Since the cytochrome P450 (CYP) system is of fundamental importance for the understanding and correct interpretation of the outcome of toxicological studies, constitutive and xenobiotic-induced 7-methoxycoumarin-O-demethylase (MCOD), i.e. 'mammalian CYP2-like', activities were monitored in vivo in zebrafish embryos via confocal laser scanning microscopy. In order to elucidate molecular mechanisms underlying the MCOD induction, dose-dependent effects of the prototypical CYP inducers β-naphthoflavone (aryl hydrocarbon receptor (AhR) agonist), rifampicin (pregnane X receptor (PXR) agonist), carbamazepine and phenobarbital (constitutive androstane receptor (CAR) agonists) were analyzed in zebrafish embryos of varying age. Starting from 36 h of age, all embryonic stages of zebrafish could be shown to have constitutive MCOD activity, albeit with spatial variation and at distinct levels. Whereas carbamazepine, phenobarbital and rifampicin had no effect on in vivo MCOD activity in 96 h old zebrafish embryos, the model aryl hydrocarbon receptor agonist β-naphthoflavone significantly induced MCOD activity in 96 h old zebrafish embryos at 46-734 nM, however, without a clear concentration-effect relationship. Induction of MCOD activity by β-naphthoflavone gradually decreased with progression of embryonic development. By in vivo characterization of constitutive and xenobiotic-induced MCOD activity patterns in 36, 60, 84 and 108 h old zebrafish embryos, this decrease could primarily be attributed to an age-related decline in the induction of MCOD activity in the cardiovascular system. Results of this study provide novel insights into the mechanism and extent, by which specific CYP activities in early life-stages of zebrafish can be influenced by exposure to xenobiotics. The study thus lends further support to the view that zebrafish embryos- at least from an age of 36 h - have an elaborate and inducible biotransformation system.

Dapsone for Pneumocystis jirovecii pneumonia prophylaxis - applying theory to clinical practice with a focus on drug interactions

Pneumocystis jirovecii pneumonia (PJP) is a potentially life-threatening infection that occurs in immunocompromised individuals. The incidence can be as high as 80% in some groups but can be reduced to less than 1% with appropriate prophylaxis. HIV-infected patients with a low CD4 count are at the highest risk of PJP. Others at substantial risk include haematopoietic stem cell and solid organ transplant recipients, those with cancer (particularly haematologic malignancies), and those receiving glucocorticoids, chemotherapeutic agents, and other immunosuppressive medications. Trimethoprim-sulfamethoxazole is an established first-line line agent for prevention and treatment of PJP. However, in some situations, this medication cannot be used and dapsone is considered a suitable cost-effective second line agent. However, information on potential interactions with drugs commonly used in immunosuppressed patients is lacking or contradictory. In this this article we review the metabolic pathway of dapsone with a focus on interactions and clinical significance particularly in patients with haematological malignancies. An understanding of this process should optimise the use of this agent.

Psychopharmacological Treatment in Older People: Avoiding Drug Interactions and Polypharmacy

BACKGROUND

As the elderly population increases, so, too, does the number of multimorbid patients and the risk of polypharmacy. The consequences include drug interactions, undesired side effects of medication, health impairment, and the need for hospital- ization. 5-10% of hospital admissions among the elderly are attributable to undesired side effects of medication.

METHODS

This review is based on publications retrieved by a selective search in PubMed and the Cochrane Library that employed the search terms "drug interaction," "undesired side effect," "polypharmacy," "pharmacokinetics," and "pharmacody- namics."

RESULTS

Elderly patients are particularly at risk of polypharmacy, both because of the prevalence of multimorbidity in old age and because of physicians' uncritical implementation of guidelines. The more drugs a person takes, the greater the risk of drug interactions and undesired side effects. Age-associated changes in pharmacokinetics and pharmacodynamics elevate this risk as well. Physicians prescribing drugs for elderly patients need to know about the drugs' catabolic pathways, protein binding, and inductive and inhibitory effects on cytochrome P450 in order to avoid drug interactions and polypharmacy.

CONCLUSION

Multiple aids and instruments are available to ensure practical and reasonable drug monitoring, so that the risks of drug interactions and undesired side effects can be detected early and avoided.

Design, Synthesis, and Pharmacological Evaluation of Second Generation EZH2 Inhibitors with Long Residence Time

Histone methyltransferase EZH2, which is the catalytic subunit of the PRC2 complex, catalyzes the methylation of histone H3K27-a transcriptionally repressive post-translational modification (PTM). EZH2 is commonly mutated in hematologic malignancies and frequently overexpressed in solid tumors, where its expression level often correlates with poor prognosis. First generation EZH2 inhibitors are beginning to show clinical benefit, and we believe that a second generation EZH2 inhibitor could further build upon this foundation to fully realize the therapeutic potential of EZH2 inhibition. During our medicinal chemistry campaign, we identified 4-thiomethyl pyridone as a key modification that led to significantly increased potency and prolonged residence time. Leveraging this finding, we optimized a series of EZH2 inhibitors, with enhanced antitumor activity and improved physiochemical properties, which have the potential to expand the clinical use of EZH2 inhibition.

Repeated dose multi-drug testing using a microfluidic chip-based coculture of human liver and kidney proximal tubules equivalents

A microfluidic multi-organ chip emulates the tissue culture microenvironment, enables interconnection of organ equivalents and overcomes interspecies differences, making this technology a promising and powerful tool for preclinical drug screening. In this study, we established a microfluidic chip-based model that enabled non-contact cocultivation of liver spheroids and renal proximal tubule barriers in a connecting media circuit over 16 days. Meanwhile, a 14-day repeated-dose systemic administration of cyclosporine A (CsA) alone or in combination with rifampicin was performed. Toxicity profiles of the two different doses of CsA on different target organs could be discriminated and that concomitant treatment with rifampicin from day6 onwards decreased the CsA concentration and attenuated the toxicity compared with that after treatment with CsA for 14 consecutive days. The latter is manifested with the changes in cytotoxicity, cell viability and apoptosis, gene expression of metabolic enzymes and transporters, and noninvasive toxicity biomarkers. The on chip coculture of the liver and the proximal tubulus equivalents showed its potential as an effective and translational tool for repeated dose multi-drug toxicity screening in the preclinical stage of drug development.

Cytotoxicity and Antimycobacterial Properties of Pyrrolo[1,2-a]quinoline Derivatives: Molecular Target Identification and Molecular Docking Studies

A series of ethyl 1-(substituted benzoyl)-5-methylpyrrolo[1,2-a]quinoline-3-carboxylates 4a–f and dimethyl 1-(substituted benzoyl)-5-methylpyrrolo[1,2-a]quinoline-2,3-dicarboxylates 4g–k have been synthesized and evaluated for their anti-tubercular (TB) activities against H37Rv (American Type Culture Collection (ATCC) strain 25177) and multidrug-resistant (MDR) strains of Mycobacterium tuberculosis by resazurin microplate assay (REMA). Molecular target identification for these compounds was also carried out by a computational approach. All test compounds exhibited anti-tuberculosis (TB) activity in the range of 8–128 µg/mL against H37Rv. The test compound dimethyl-1-(4-fluorobenzoyl)-5-methylpyrrolo[1,2-a]quinoline-2,3-dicarboxylate 4j emerged as the most promising anti-TB agent against H37Rv and multidrug-resistant strains of Mycobacterium tuberculosis at 8 and 16 µg/mL, respectively. In silico evaluation of pharmacokinetic properties indicated overall drug-likeness for most of the compounds. Docking studies were also carried out to investigate the binding affinities as well as interactions of these compounds with the target proteins.

In vitro inhibition of human cytochrome P450 enzymes by the novel atypical antipsychotic drug asenapine: a prediction of possible drug-drug interactions

BACKGROUND

Inhibition of cytochrome P450 (CYP) enzymes is the most common cause of harmful drug-drug interactions. The present study aimed at examining the inhibitory effect of the novel antipsychotic drug asenapine on the main CYP enzymes in human liver.

METHODS

The experiments were performed in vitro using pooled human liver microsomes and the human cDNA-expressed CYP enzymes: CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 (Supersomes). Activities of CYP enzymes were determined using the CYP-specific reactions: caffeine 3-N-demethylation (CYP1A2), diclofenac 4'-hydroxylation (CYP2C9), perazine N-demethylation (CYP2C19), bufuralol 1'-hydroxylation (CYP2D6), and testosterone 6β-hydroxylation (CYP3A4). The rates of the CYP-specific reactions were assessed in the absence and presence of asenapine using HPLC.

RESULTS

The obtained results showed that both in human liver microsomes and Supersomes asenapine potently and to a similar degree inhibited the activity of CYP1A2 via a mixed mechanism (K_i = 3.2 μM in liver microsomes and Supersomes) and CYP2D6 via a competitive mechanism (K_i = 1.75 and 1.89 μM in microsomes and Supersomes, respectively). Moreover, asenapine attenuated the CYP3A4 activity via a non-competitive mechanism (K_i = 31.3 and 27.3 μM in microsomes and Supersomes, respectively). In contrast, asenapine did not affect the activity of CYP2C9 or CYP2C19.

CONCLUSION

The potent inhibition of CYP1A2 and CYP2D6 by asenapine, demonstrated in vitro, will most probably be observed also in vivo, since the calculated K_i values are close to the presumed concentration range for asenapine in the liver in vivo. Therefore, pharmacokinetic interactions involving asenapine and CYP2D6 or CYP1A2 substrates are likely to occur during their co-administration to patients.

In silico Design and Synthesis of Tetrahydropyrimidinones and Tetrahydropyrimidinethiones as Potential Thymidylate Kinase Inhibitors Exerting Anti-TB Activity Against Mycobacterium tuberculosis

Background and Purpose

Tuberculosis has been reported to be the worldwide leading cause of death resulting from a sole infectious agent. The emergence of multidrug-resistant tuberculosis and extensively drug-resistant tuberculosis has made the battle against the infection more difficult since most currently available therapeutic options are ineffective against these resistant strains. Therefore, novel molecules need to be developed to effectively treat tuberculosis disease. Preliminary docking studies revealed that tetrahydropyrimidinone derivatives have favorable interactions with the thymidylate kinase receptor. In the present investigation, we report the synthesis and the mycobacterial activity of several pyrimidinones and pyrimidinethiones as potential thymidylate kinase inhibitors.

Methods

The title compounds (1a-d) and (2a-b) were synthesized by a one-pot three-component Biginelli reaction. They were subsequently characterized and used for whole-cell anti-TB screening against H37Rv and multidrug-resistant (MDR) strains of Mycobacterium tuberculosis (MTB) by the resazurin microplate assay (REMA) plate method. Molecular modeling was conducted using the Accelry's Discovery Studio 4.0 client program to explain the observed bioactivity of the compounds. The pharmacokinetic properties of the synthesized compounds were predicted and analyzed.

Results

Of the compounds tested for anti-TB activity, pyrimidinone 1a and pyrimidinethione 2a displayed moderate activity against susceptible MTB H37Rv strains at 16 and 32 µg/mL, respectively. Only compound 2a was observed to exert modest activity at 128 µg/mL against MTB strains with cross-resistance to rifampicin and isoniazid. The presence of the trifluoromethyl group was essential to retain the inhibitory activity of compounds 1a and 2a. Molecular modeling studies of these compounds against thymidylate kinase targets demonstrated a positive correlation between the bioactivity and structure of the compounds. The in-silico ADME (absorption, distribution, metabolism, and excretion) prediction indicated favorable pharmacokinetic and drug-like properties for most compounds.

Conclusion

Pyrimidinone 1a and pyrimidinethione 2a were identified as the leading compounds and can serve as a starting point to develop novel anti-TB therapeutic agents.

Novel Series of Methyl 3-(Substituted Benzoyl)-7-Substituted-2-Phenylindolizine-1-Carboxylates as Promising Anti-Inflammatory Agents: Molecular Modeling Studies

The cyclooxygenase-2 (COX-2) enzyme is considered to be an important target for developing novel anti-inflammatory agents. Selective COX-2 inhibitors offer the advantage of lower adverse effects that are commonly associated with non-selective COX inhibitors. In this work, a novel series of methyl 3-(substituted benzoyl)-7-substituted-2-phenylindolizine-1-carboxylates was synthesized and evaluated for COX-2 inhibitory activity. Compound 4e was identified as the most active compound of the series with an IC50 of 6.71 M, which is comparable to the IC50 of indomethacin, a marketed non-steroidal anti-inflammatory drug (NSAID). Molecular modeling and crystallographic studies were conducted to further characterize the compounds and gain better understanding of the binding interactions between the compounds and the residues at the active site of the COX-2 enzyme. The pharmacokinetic properties and potential toxic effects were predicted for all the synthesized compounds, which indicated good drug-like properties. Thus, these synthesized compounds can be considered as potential lead compounds for developing effective anti-inflammatory therapeutic agents.

Evaluation of cytochrome P450 3A4‑mediated drug‑drug interaction potential between P2Y12 inhibitors and statins

Ticagrelor and prasugrel are widely used in the treatment of acute coronary syndrome. The co‑administration of ticagrelor or prasugrel with statins in the clinic has already drawn a great deal of attention. The aims of the present study were to evaluate the safety and effectiveness, and guide the rational clinical use of, co‑administration of ticagrelor or prasugrel with statins by exploring potential drug interactions. The activity of cytochrome P450 family 3 subfamily A member 4 (CYP3A4) was detected, and its protein and mRNA expression levels were measured in a rat model and liver microsomes to evaluate the effect of the drug combinations on CYP3A4. High performance liquid chromatography, western blotting and reverse transcription‑quantitative PCR were used to perform these investigations. The in vitro experiments suggested that ticagrelor inhibited CYP3A4 activity, with IC50 and inhibitor constant (Ki) values of 68.74 and 26.47 µM, respectively; prasugrel also inhibited CYP3A4, activity with IC50 and Ki values of 16.24 and 10.84 µM, respectively. When different dosages of the antagonists were combined with simvastatin or atorvastatin, the metabolic rate was reduced more effectively at higher dosages when compared with lower dosages. An in vivo pharmacokinetic study demonstrated that the co‑administration of ticagrelor or prasugrel with simvastatin caused an increase in the principal pharmacokinetic parameters of the probe drug dapsone [area under the concentration/time curve (AUC)0‑t, AUC0‑∞ and t1/2] and a decrease in clearance compared with ticagrelor, prasugrel or simvastatin alone. Additional studies confirmed that the two investigated P2Y12 inhibitors were able to decrease the protein level of CYP3A4 by promoting protein degradation through the proteasomal pathway, and combination with statins such as simvastatin had a synergistic inhibitory effect on CYP3A4 activity. These results demonstrated that the co‑administration of P2Y12 inhibitors with simvastatin could markedly inhibit the activity of CYP3A4, and these findings will further influence the assessment of the clinical effectiveness (reduced or enhanced efficacy) and safety (bleeding and rhabdomyolysis) in the clinic.

The mechanisms of pharmacokinetic food-drug interactions - A perspective from the UNGAP group

The simultaneous intake of food and drugs can have a strong impact on drug release, absorption, distribution, metabolism and/or elimination and consequently, on the efficacy and safety of pharmacotherapy. As such, food-drug interactions are one of the main challenges in oral drug administration. Whereas pharmacokinetic (PK) food-drug interactions can have a variety of causes, pharmacodynamic (PD) food-drug interactions occur due to specific pharmacological interactions between a drug and particular drinks or food. In recent years, extensive efforts were made to elucidate the mechanisms that drive pharmacokinetic food-drug interactions. Their occurrence depends mainly on the properties of the drug substance, the formulation and a multitude of physiological factors. Every intake of food or drink changes the physiological conditions in the human gastrointestinal tract. Therefore, a precise understanding of how different foods and drinks affect the processes of drug absorption, distribution, metabolism and/or elimination as well as formulation performance is important in order to be able to predict and avoid such interactions. Furthermore, it must be considered that beverages such as milk, grapefruit juice and alcohol can also lead to specific food-drug interactions. In this regard, the growing use of food supplements and functional food requires urgent attention in oral pharmacotherapy. Recently, a new consortium in Understanding Gastrointestinal Absorption-related Processes (UNGAP) was established through COST, a funding organisation of the European Union supporting translational research across Europe. In this review of the UNGAP Working group "Food-Drug Interface", the different mechanisms that can lead to pharmacokinetic food-drug interactions are discussed and summarised from different expert perspectives.

Pharmacogenetics of artemether-lumefantrine influence on nevirapine disposition: Clinically significant drug-drug interaction?

AIMS

In this study the influence of first-line antimalarial drug artemether-lumefantrine on the pharmacokinetics of the antiretroviral drug nevirapine was investigated in the context of selected single nucleotide polymorphisms (SNPs) in a cohort of adult HIV-infected Nigerian patients.

METHODS

This was a two-period, single sequence crossover study. In stage 1, 150 HIV-infected patients receiving nevirapine-based antiretroviral regimens were enrolled and genotyped for seven SNPs. Sparse pharmacokinetic sampling was conducted to identify SNPs independently associated with nevirapine plasma concentration. Patients were categorized as poor, intermediate and extensive metabolizers based on the numbers of alleles of significantly associated SNPs. Intensive sampling was conducted in selected patients from each group. In stage 2, patients received standard artemether-lumefantrine treatment with nevirapine, and intensive pharmacokinetic sampling was conducted on day 3.

RESULTS

No clinically significant changes were observed in key nevirapine pharmacokinetic parameters, the 90% confidence interval for the measured changes falling completely within the 0.80-1.25 no-effect boundaries. However, the number of patients with trough plasma nevirapine concentration below the 3400 ng ml^-1 minimum effective concentration increased from 10% without artemether-lumefantrine (all extensive metabolizers) to 21% with artemether-lumefantrine (14% extensive, 4% intermediate, and 3% poor metabolizers).

CONCLUSIONS

This approach highlights additional increase in the already existing risk of suboptimal trough plasma concentration, especially in extensive metabolizers when nevirapine is co-administered with artemether-lumefantrine.

Enhanced Hepatic Differentiation of Human Induced Pluripotent Stem Cells Using Gas-Permeable Membrane

IMPACT STATEMENT

Although oxygen is a vital nutrient for the hepatocytes in vitro, few reports have focused on its effect during hepatic differentiation of induced pluripotent stem cells (iPSCs). In this report, we performed the hepatic differentiation of human iPSCs (hiPSCs) under different atmospheric oxygen concentrations and oxygen supply fluxes to investigate the effects of oxygen in terms of both the concentration and the supply flux. Results demonstrate that direct oxygenation through a polydimethylsiloxane (PDMS) membrane enhances the maturation and efficient production of hiPSC-derived hepatocyte-like cells (iHeps). Thus, direct oxygenation through a PDMS membrane is a better alternative culture method over conventional tissue culture-treated polystyrene (TCPS) plates for the maturation of hiPSC-derived hepatocytes in vitro.

Failure to Respond after Reinstatement of Antidepressant Medication: A Systematic Review

BACKGROUND

Following remission of an anxiety disorder or a depressive disorder, antidepressants are frequently discontinued and in the case of symptom occurrence reinstated. Reinstatement of antidepressants seems less effective in some patients, but an overview is lacking. This systematic review aimed to provide insight into the magnitude and risk factors of response failure after reinstatement of antidepressants in patients with anxiety disorders, depressive disorders, obsessive-compulsive disorder (OCD), or posttraumatic stress disorder (PTSD).

METHOD

PubMed, Embase, and trial registers were systematically searched for studies in which patients: (1) had an anxiety disorder, a depressive disorder, OCD, or PTSD and (2) experienced failure to respond after reinstatement of a previously effective antidepressant.

RESULTS

Ten studies reported failure to respond following antidepressant reinstatement. The phenomenon was observed in 16.5% of patients with a depressive disorder, OCD, and social phobia and occurred in all common classes of antidepressants. The range of response failure was broad, varying between 3.8 and 42.9% across studies. No risk factors for failure to respond were investigated. The overall study quality was limited.

CONCLUSION

Research investigating response failure is scarce and the study quality limited. Response failure occurred in a substantial minority of patients. Contributors to the relevance of this phenomenon are the prevalence of the investigated disorders, the number of patients being treated with antidepressants, and the occurrence of response failure for all common classes of antidepressants. This systematic review highlights the need for studies systematically investigating this phenomenon and associated risk factors.

Potential Metabolic Drug-Drug Interaction of Citrus aurantium L. (Rutaceae) Evaluating by Its Effect on 3 CYP450

Aim:Fructus aurantii (FA) is widely used in clinic as an expectorant and digestant herb in traditional Chinese medicine and proven to have a variety of pharmacological functions. FA is close to grapefruit either by botanical taxonomy or by their same components (flavonoids, etc.) and grapefruit has been proven to cause drug-drug interaction when co-administrated with CYP3A4 substrates. Besides, FA contains many compounds, such as flavonoids, which have been reported to impact the expressions of CYP450. However, the effect of FA on CYP450, whose change may affect drug safety and clinical efficacy attributed to drug-drug interaction, still remains unknown. Methods: The protein, mRNA expression and enzyme activity of CYP1A2, CYP3A4, and CYP2E1 in rat were determined by Western Blotting, RT-PCR method, the cocktail method, respectively, after orally administration of FA in succession for 7 days. CYP1A2, CYP3A4, and CYP2E1 mRNA expression were investigated in HepG2 cells following FA-medicated serum incubation for 24 h. Results: In rat, compared to the control group, CYP1A2, CYP3A4 protein, and mRNA expression were significantly induced consistent with the corresponding CYP activities; the protein expression of CYP2E1 was significantly upregulated, while the corresponding mRNA expression and enzyme activity showed no significant change. In HepG2 cells, compared to the control group, the mRNA expression of CYP1A2 and CYP3A4 was up-regulated statistically while CYP2E1 mRNA expression was not significantly induced or inhibited. Conclusion: FA may be a potential slight inducer of CYP1A2 and CYP3A4 and is unlikely to impact CYP2E1 until clinical researches are conducted.

Consequences of Phenytoin Exposure on Hepatic Cytochrome P450 Expression during Postnatal Liver Maturation in Mice

The induction of cytochrome P450 (P450) enzymes in response to drug treatment is a significant contributing factor to drug-drug interactions, which may reduce therapeutic efficacy and/or cause toxicity. Since most studies on P450 induction are performed in adults, enzyme induction at neonatal, infant, and adolescent ages is not well understood. Previous work defined the postnatal ontogeny of drug-metabolizing P450s in human and mouse livers; however, there are limited data on the ontogeny of the induction potential of each enzyme in response to drug treatment. Induction of P450s at the neonatal age may also cause permanent alterations in P450 expression in adults. The goal of this study was to investigate the short- and long-term effects of phenytoin treatment on mRNA and protein expressions and enzyme activities of CYP2B10, 2C29, 3A11, and 3A16 at different ages during postnatal liver maturation in mice. Induction of mRNA immediately following phenytoin treatment appeared to depend on basal expression of the enzyme at a specific age. While neonatal mice showed the greatest fold changes in CYP2B10, 2C29, and 3A11 mRNA expression following treatment, the levels of induced protein expression and enzymatic activity were much lower than that of induced levels in adults. The expression of fetal CYP3A16 was repressed by phenytoin treatment. Neonatal treatment with phenytoin did not permanently induce enzyme expression in adulthood. Taken together, our data suggest that inducibility of drug-metabolizing P450s is much lower in neonatal mice than it is in adults and neonatal induction by phenytoin is not permanent.

Immortalized common marmoset (Callithrix jacchus) hepatic progenitor cells possess bipotentiality in vitro and in vivo

Common marmoset (Callithrix jacchus) is emerging as a clinically relevant nonhuman primate model for various diseases, but is hindered by the availability of marmoset cell lines, which are critical for understanding the disease pathogenesis and drug/toxicological screening prior to animal testing. Here we describe the generation of immortalized marmoset hepatic progenitor cells (MHPCs) by lentivirus-mediated transfer of the simian virus 40 large T antigen gene in fetal liver polygonal cells. MHPCs proliferate indefinitely in vitro without chromosomal alteration and telomere shortening. These cells possess hepatic progenitor cell-specific gene expression profiles with potential to differentiate into both hepatocytic and cholangiocytic lineages in vitro and in vivo and also can be genetically modified. Importantly, injected MHPCs repopulated the injured liver of fumarylacetoacetate hydrolase (Fah)-deficient mice with hepatocyte-like cells. MHPCs also engraft as cholangiocytes into bile ducts of 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced bile ductular injured mice. MHPCs provide a tool to enable efficient derivation and genetic modification of both hepatocytes and cholangiocytes for use in disease modeling, tissue engineering, and drug screening.

In vitro inhibitory mechanisms and molecular docking of 1'-S-1'-acetoxychavicol acetate on human cytochrome P450 enzymes

BACKGROUND

The compound, 1'-S-1'-acetoxychavicol acetate (ACA), isolated from the rhizomes of a Malaysian ethno-medicinal plant, Alpinia conchigera Griff. (Zingiberaceae), was previously shown to have potential in vivo antitumour activities. In the development of a new drug entity, potential interactions of the compound with the cytochrome P450 superfamily metabolizing enzymes need to be ascertain.

PURPOSE

The concomitant use of therapeutic drugs may cause potential drug-drug interactions by decreasing or increasing plasma levels of the administered drugs, leading to a suboptimal clinical efficacy or a higher risk of toxicity. Thus, evaluating the inhibitory potential of a new chemical entity, and to clarify the mechanism of inhibition and kinetics in the various CYP enzymes is an important step to predict drug-drug interactions.

STUDY DESIGN

This study was designed to assess the potential inhibitory effects of Alpinia conchigera Griff. rhizomes extract and its active constituent, ACA, on nine c-DNA expressed human cytochrome P450s (CYPs) enzymes using fluorescent CYP inhibition assay.

METHODS/RESULTS

The half maximal inhibitory concentration (IC₅₀) of Alpinia conchigera Griff. rhizomes extract and ACA was determined for CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2D6, CYP2E1, CYP3A4 and CYP3A5. A. conchigera extract only moderately inhibits on CYP3A4 (IC₅₀ = 6.76 ± 1.88µg/ml) whereas ACA moderately inhibits the activities of CYP1A2 (IC₅₀ = 4.50 ± 0.10µM), CYP2D6 (IC₅₀ = 7.50 ± 0.17µM) and CYP3A4 (IC₅₀ = 9.50 ± 0.57µM) while other isoenzymes are weakly inhibited. In addition, mechanism-based inhibition studies reveal that CYP1A2 and CYP3A4 exhibited non-mechanism based inhibition whereas CYP2D6 showed mechanism-based inhibition. Lineweaver-Burk plots depict that ACA competitively inhibited both CYP1A2 and CYP3A4, with a K_i values of 2.36 ± 0.03 µM and 5.55 ± 0.06µM, respectively, and mixed inhibition towards CYP2D6 with a K_i value of 4.50 ± 0.08µM. Further, molecular docking studies show that ACA is bound to a few key amino acid residues in the active sites of CYP1A2 and CYP3A4, while one amino residue of CYP2D6 through predominantly Pi-Pi interactions.

CONCLUSION

Overall, ACA may demonstrate drug-drug interactions when co-administered with other therapeutic drugs that are metabolized by CYP1A2, CYP2D6 or CYP3A4 enzymes. Further in vivo studies, however, are needed to evaluate the clinical significance of these interactions.

Considerations from the IQ Induction Working Group in Response to Drug-Drug Interaction Guidance from Regulatory Agencies: Focus on Downregulation, CYP2C Induction, and CYP2B6 Positive Control

The European Medicines Agency (EMA), the Pharmaceutical and Medical Devices Agency (PMDA), and the Food and Drug Administration (FDA) have issued guidelines for the conduct of drug-drug interaction studies. To examine the applicability of these regulatory recommendations specifically for induction, a group of scientists, under the auspices of the Drug Metabolism Leadership Group of the Innovation and Quality (IQ) Consortium, formed the Induction Working Group (IWG). A team of 19 scientists, from 16 of the 39 pharmaceutical companies that are members of the IQ Consortium and two Contract Research Organizations reviewed the recommendations, focusing initially on the current EMA guidelines. Questions were collated from IQ member companies as to which aspects of the guidelines require further evaluation. The EMA was then approached to provide insights into their recommendations on the following: 1) evaluation of downregulation, 2) in vitro assessment of CYP2C induction, 3) the use of CITCO as the positive control for CYP2B6 induction by CAR, 4) data interpretation (a 2-fold increase in mRNA as evidence of induction), and 5) the duration of incubation of hepatocytes with test article. The IWG conducted an anonymous survey among IQ member companies to query current practices, focusing specifically on the aforementioned key points. Responses were received from 19 companies. All data and information were blinded before being shared with the IWG. The results of the survey are presented, together with consensus recommendations on downregulation, CYP2C induction, and CYP2B6 positive control. Results and recommendations related to data interpretation and induction time course will be reported in subsequent articles.

Discovery and Pre-Clinical Characterization of Third-Generation 4-H Heteroaryldihydropyrimidine (HAP) Analogues as Hepatitis B Virus (HBV) Capsid Inhibitors

Described herein are the discovery and structure-activity relationship (SAR) studies of the third-generation 4-H heteroaryldihydropyrimidines (4-H HAPs) featuring the introduction of a C6 carboxyl group as novel HBV capsid inhibitors. This new series of 4-H HAPs showed improved anti-HBV activity and better drug-like properties compared to the first- and second-generation 4-H HAPs. X-ray crystallographic study of analogue 12 (HAP_R01) with Cp149 Y132A mutant hexamer clearly elucidated the role of C6 carboxyl group played for the increased binding affinity, which formed strong hydrogen bonding interactions with capsid protein and coordinated waters. The representative analogue 10 (HAP_R10) was extensively characterized in vitro (ADMET) and in vivo (mouse PK and PD) and subsequently selected for further development as oral anti-HBV infection agent.