The role of transporters in the pharmacokinetics of orally administered drugs

In vivo deposition of poorly soluble drugs

Administered drug molecules, whether dissolved or solubilized, have the potential to precipitate and accumulate as solid forms in tissues and cells within the body. This phase transition can significantly impact the pharmacokinetics of treatment. It is thus crucial to gain an understanding of how drug solubility/permeability, drug formulations and routes of administration affect in vivo behaviors of drug deposition. This review examines literature reports on the drug deposition in tissues and cells of poorly water-soluble drugs, as well as underlying physical mechanisms that lead to precipitation. Our work particularly highlights drug deposition in macrophages and the subcellular fate of precipitated drugs. We also propose a tissue permeability-based classification framework to evaluate precipitation potentials of poorly soluble drugs in major organs and tissues. The impact on pharmacokinetics is further discussed and needs to be considered in developing drug delivery systems. Finally, bioimaging techniques that are used to examine aggregated states and the intracellular trafficking of absorbed drugs are summarized.

ABCG2 polymorphism and rivaroxaban pharmacokinetics in healthy individuals after a single dose

Rivaroxaban is a direct factor Xa inhibitor. Its interindividual variability is large and may be connected to the occurrence of adverse drug reactions or drug inefficacy. Pharmacogenetics studies concentrating on the reasons underlying rivaroxaban's inadequate response could help explain the differences in treatment results and medication safety profiles. Against this background, this study evaluated whether polymorphisms in the gene encoding the ABCG2 transporter modify the pharmacokinetic characteristics of rivaroxaban. A total of 117 healthy volunteers participated in two bioequivalence experiments with a single oral dose of 20 mg rivaroxaban, with one group fasting and the other being fed. Ultra-high-performance liquid chromatography coupled with mass spectrometry was employed to determine the plasma concentrations of rivaroxaban, and the WinNonlin program was used to calculate the pharmacokinetics parameters. In the fasting group, the rivaroxaban pharmacokinetic parameters of Vd (508.27 vs 334.45 vs 275.59 L) and t1/2 (41.04 vs 16.43 vs 15.47 h) were significantly higher in ABCG2 421 A/A genotype carriers than in ABCG2 421 C/C and 421 C/A genotype carriers (P<0.05). The mean values of Cmax (145.81 vs 176.27 vs 190.19 ng/mL), AUC0-t (1193.81 vs 1374.69 vs 1570.77 ng/mL·h), and Cl (11.82 vs 14.50 vs 13.01 mL/h) for these groups were lower, but this difference was not statistically significant (P>0.05). These findings suggested that the ABCG2 421 A/A genotype may impact rivaroxaban parameters after a single dose in healthy subjects. This finding must be validated before it is applied in clinical practice.

Bioanalytical HPLC method with fluorescence detector for determination of Entresto™ when co-administered with ibuprofen and fexofenadine: a pharmacokinetic study

Entresto™ (LCZ696) has been approved globally for heart failure management. However, its lifelong use alongside over-the-counter (OTC) drugs like ibuprofen (IBU) and fexofenadine (FEX) necessitates an in-depth investigation of potential pharmacokinetic interactions, as they share the same metabolic and elimination pathways. This study aimed to develop a bioanalytical HPLC method with a fluorescence detector (FLD) to quantify LCZ696 analytes (valsartan, VAL; sacubitril, SAC; and sacubitril active metabolite, LBQ657) in rat plasma. Additionally, an in vivo study was performed to investigate the pharmacokinetic interactions of LCZ696 with IBU and FEX. Utilizing HPLC with a gradient-mode mobile phase of acetonitrile and 0.025 M phosphate buffer (pH 3), the study demonstrated a significant increase in the bioavailability of LCZ696 analytes (VAL and LBQ657) when co-administered with IBU (C max 0.23 ± 0.07 and 0.53 ± 0.21 μg mL-1, respectively) compared to the control (0.17 ± 0.03 and 0.33 ± 0.14 μg mL-1). A more significant increase in C max was noticed with FEX (0.38 ± 0.01 and 0.77 ± 0.18 μg mL-1, respectively). Moreover, a decrease in the clearance (Cl/F) of VAL and LBQ657 was observed (18.05 ± 1.94 and 12.42 ± 2.97 L h-1 kg, respectively) with a more pronounced effect in the case of FEX (30.87 ± 4.29 and 33.14 ± 9.57 L h-1 kg, respectively) compared to the control (49.99 ± 7.31 and 51.19 ± 9.12 L h-1 kg, respectively). In conclusion, our study underscores the importance of cautious administration and appropriate dose spacing of IBU and FEX in patients treated with LCZ696 to prevent elevated serum concentrations and potential toxicity. The novelty of this work lies in its dual contribution: developing a highly sensitive HPLC-FLD method and comprehensively elucidating significant pharmacokinetic interactions between LCZ696 and common OTC drugs.

The Use of Carboxyfluorescein Reveals the Transport Function of MCT6/SLC16A5 Associated with CD147 as a Chloride-Sensitive Organic Anion Transporter in Mammalian Cells

Oral drug absorption involves drug permeation across the apical and basolateral membranes of enterocytes. Although transporters mediating the influx of anionic drugs in the apical membranes have been identified, transporters responsible for efflux in the basolateral membranes remain unclear. Monocarboxylate transporter 6 (MCT6/SLC16A5) has been reported to localize to the apical and basolateral membranes of human enterocytes and to transport organic anions such as bumetanide and nateglinide in the Xenopus oocyte expression system; however, its transport functions have not been elucidated in detail. In this study, we characterized the function of MCT6 expressed in HEK293T cells and explored fluorescent probes to more easily evaluate MCT6 function. The results illustrated that MCT6 interacts with CD147 to localize at the plasma membrane. When the uptake of various fluorescein derivatives was examined in NaCl-free uptake buffer (pH 5.5), the uptake of 5-carboxyfluorescein (5-CF) was significantly greater in MCT6 and CD147-expressing cells. MCT6-mediated 5-CF uptake was saturable with a Km of 1.07 mM and inhibited by several substrates/inhibitors of organic anion transporters and extracellular Cl ion with an IC50 of 53.7 mM. These results suggest that MCT6 is a chloride-sensitive organic anion transporter that can be characterized using 5-CF as a fluorescent probe.

Screening oral drugs for their interactions with the intestinal transportome via porcine tissue explants and machine learning

In vitro systems that accurately model in vivo conditions in the gastrointestinal tract may aid the development of oral drugs with greater bioavailability. Here we show that the interaction profiles between drugs and intestinal drug transporters can be obtained by modulating transporter expression in intact porcine tissue explants via the ultrasound-mediated delivery of small interfering RNAs and that the interaction profiles can be classified via a random forest model trained on the drug-transporter relationships. For 24 drugs with well-characterized drug-transporter interactions, the model achieved 100% concordance. For 28 clinical drugs and 22 investigational drugs, the model identified 58 unknown drug-transporter interactions, 7 of which (out of 8 tested) corresponded to drug-pharmacokinetic measurements in mice. We also validated the model's predictions for interactions between doxycycline and four drugs (warfarin, tacrolimus, digoxin and levetiracetam) through an ex vivo perfusion assay and the analysis of pharmacologic data from patients. Screening drugs for their interactions with the intestinal transportome via tissue explants and machine learning may help to expedite drug development and the evaluation of drug safety.

Bioavailability of Orally Administered Drugs After Bariatric Surgery

PURPOSE OF REVIEW

Oral drug absorption after bariatric surgery is likely to be altered, but the impact of different bariatric surgery procedures on individual drugs is not uniform. The aim of this article is to describe factors influencing the bioavailability of orally administered drugs after bariatric surgery and to provide readers with practical recommendations for drug dosing. We also discuss the medications that may be harmful after bariatric surgery.

RECENT FINDINGS

The fundamental factors for enteral drug absorption are the production of gastric acid; the preserved length of the intestine, i.e., the size of the absorption surface and/or the preserved enterohepatic circulation; and the length of common loop where food and drugs are mixed with digestive enzymes and bile acids. Bypassing of metabolizing enzymes or efflux pumps and changes in intestinal motility can also play an important role. Significant changes of drug absorption early after the anatomic alteration may also be gradually ameliorated due to gradual intestinal adaptation. The most affected drugs are those with low or variable bioavailability and those undergoing enterohepatic circulation. Attention should also be paid to oral drug formulations, especially in the early postoperative period, when immediate-release and liquid formulations are preferred. The changes in oral bioavailability are especially clinically meaningful in patients treated with drugs possessing narrow therapeutic index (e.g., oral anticoagulants, levothyroxine, and anticonvulsants) or in acute conditions (e.g., anti-infectives); nevertheless, it may also influence the therapeutic value of chronic therapy (e.g., antidepressants. antihypertensives, antiplatelets, statins, PPIs, contraceptives, and analgesics); therapeutic effect of chronic therapy is further influenced by pharmacokinetic alterations resulting from weight loss. Therapeutic drug monitoring, periodical clinical evaluation, and adequate dose adjustments are necessary. Due to safety reasons, patients should avoid oral bisphosphonates, regular use of non-steroidal anti-inflammatory drugs, and, if possible, corticosteroids after bariatric surgery.

Integrating the gut microbiome and pharmacology

The gut microbiome harbors trillions of organisms that contribute to human health and disease. These bacteria can also affect the properties of medical drugs used to treat these diseases, and drugs, in turn, can reshape the microbiome. Research addressing interdependent microbiome-host-drug interactions thus has broad impact. In this Review, we discuss these interactions from the perspective of drug bioavailability, absorption, metabolism, excretion, toxicity, and drug-mediated microbiome modulation. We survey approaches that aim to uncover the mechanisms underlying these effects and opportunities to translate this knowledge into new strategies to improve the development, administration, and monitoring of medical drugs.

Distribution of lamivudine into lymph node HIV reservoir

Efficient delivery of antiretroviral agents to lymph nodes is important to decrease the size of the HIV reservoir within the lymphatic system. Lamivudine (3TC) is used in first-line regimens for the treatment of HIV. As a highly hydrophilic small molecule, 3TC is not predicted to associate with chylomicrons and therefore should have negligible uptake into intestinal lymphatics following oral administration. Similarly, negligible amounts of 3TC are predicted to be transported into peripheral lymphatics following subcutaneous (SC) injection due to the faster flow rate of blood in comparison to lymph. In this work, we performed pharmacokinetic and biodistribution studies of 3TC in rats following oral lipid-based, oral lipid-free, SC, and intravenous (IV) administrations. In the oral administration studies, mesenteric lymph nodes (MLNs) had significantly higher 3TC concentrations compared to other lymph nodes, with mean tissue:serum ratios ranging from 1.4 to 2.9. However, cells and chylomicrons found in mesenteric lymph showed low-to-undetectable concentrations. In SC studies, administration-side (right) draining inguinal and popliteal lymph nodes had significantly higher concentrations (tissue:serum ratios as high as 3.2) than corresponding left-side nodes. In IV studies, lymph nodes had lower mean tissue:serum ratios ranging from 0.9 to 1.4. We hypothesize that following oral or SC administration, slower permeation of this hydrophilic molecule into blood capillaries may result in considerable passive 3TC penetration into lymphatic vessels. Further studies will be needed to clarify the mechanism of delivery of 3TC and similar antiretroviral drugs into the lymph nodes.

TICBase: Integrated Resource for Data on Drug and Environmental Chemical Interactions with Mammalian Drug Transporters

Environmental health science seeks to predict how environmental toxins, chemical toxicants, and prescription drugs accumulate and interact within the body. Xenobiotic transporters of the ATP-binding cassette (ABC) and solute carrier (SLC) superfamilies are major determinants of the uptake and disposition of xenobiotics across the kingdoms of life. The goal of this study was to integrate drug and environmental chemical interactions of mammalian ABC and SLC proteins in a centralized, integrative database. We built upon an existing publicly accessible platform-the "TransPortal"-which was updated with novel data and searchable features on transporter-interfering chemicals from manually curated literature data. The integrated resource TransPortal-TICBase (https://transportal.compbio.ucsf.edu) now contains information on 46 different mammalian xenobiotic transporters of the ABC- and SLC-type superfamilies, including 13 newly added rodent and 2 additional human drug transporters, 126 clinical drug-drug interactions, and a more than quadrupled expansion of the initial in vitro chemical interaction data from 1,402 to 6,296 total interactions. Based on our updated database, environmental interference with major human and rodent drug transporters occurs across the ABC- and SLC-type superfamilies, with kinetics indicating that some chemicals, such as the ionic liquid 1-hexylpyridinium chloride and the antiseptic chlorhexidine, can act as strong inhibitors with potencies similar or even higher than pharmacological model inhibitors. The new integrated web portal serves as a central repository of current and emerging data for interactions of prescription drugs and environmental chemicals with human drug transporters. This archive has important implications for predicting adverse drug-drug and drug-environmental chemical interactions and can serve as a reference website for the broader scientific community of clinicians and researchers.

Solubility-Permeability Interplay in Facilitating the Prediction of Drug Disposition Routes, Extent of Absorption, Food Effects, Brain Penetration and Drug Induced Liver Injury Potential

Here I detail the use of measures of permeability rate and solubility in predicting drug disposition characteristics through the utilization of the Biopharmaceutics Drug Disposition Classification System (BDDCS) and the Extended Clearance Classification System (ECCS) as well as the accuracy of the systems in predicting the major route of elimination and the extent of oral absorption of a new small molecule therapeutics. I compare the BDDCS and ECCS with the FDA Biopharmaceutics Classification System (BCS). I also detail the use of the BCS in predicting food effects and the BDDCS in predicting brain disposition of small molecule therapeutics and in validating DILI predictive metrics. This review provides an update of the current status of these classification systems and their uses in the drug development process.

Clinical outcomes of chemotherapy in cancer patients with different ethnicities

BACKGROUND

Choosing the most effective chemotherapeutic agent with safest side effect profile is a common challenge in cancer treatment. Although there are standardized chemotherapy protocols in place, protocol changes made after extensive clinical trials demonstrate significant improvement in the efficacy and tolerability of certain drugs. The pharmacokinetics, pharmacodynamics, and tolerance of anti-cancer medications are all highly individualized. A driving force behind these differences lies within a person's genetic makeup.

RECENT FINDINGS

Pharmacogenomics, the study of how an individual's genes impact the processing and action of a drug, can optimize drug responsiveness and reduce toxicities by creating a customized medication regimen. However, these differences are rarely considered in the initial determination of standardized chemotherapeutic protocols and treatment algorithms. Because pharmacoethnicity is influenced by both genetic and nongenetic variables, clinical data highlighting disparities in the frequency of polymorphisms between different ethnicities is steadily growing.  Recent data suggests that ethnic variations in the expression of allelic variants may result in different pharmacokinetic properties of the anti-cancer medication. In this article, the clinical outcomes of various chemotherapy classes in patients of different ethnicities were reviewed.

CONCLUSION

Genetic and nongenetic variables contribute to the interindividual variability in response to chemotherapeutic drugs. Considering pharmacoethnicity in the initial determination of standard chemotherapeutic protocols and treatment algorithms can lead to better clinical outcomes of patients of different ethnicities.

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.

Gabapentin: Clinical Use and Pharmacokinetics in Dogs, Cats, and Horses

Gabapentin is an anticonvulsant drug, which presents an established clinical efficacy in human patients for the management of refractory partial seizures, secondarily generalized tonic-clonic seizures, and for the control of chronic neuropathic pain. Gabapentin was synthesized as a structural analogue of the inhibitory neurotransmitter GABA, with GABA-mimetic effects, able to cross the blood-brain barrier. In veterinary medicine, is extra-label used in combination with other treatments to control seizures when other drugs are no longer effective or become toxic or for neuropathic pain treatment and anxiety. This review aimed to clarify gabapentin use and pharmacokinetic aspects to promote conscious use in dogs, cats, and horses. In dogs, gabapentin was beneficial in the treatment of epilepsy, as well as chronic, neuropathic, and post-operative pain, as well as anxiety. In cats, it showed efficacy in post-ovariohysterectomy-related pain and in anxiety management. In horses, gabapentin has been administered as an analgesic for chronic pain management. In conclusion, when used in combination with other drugs, gabapentin can be considered an interesting therapeutic option for the treatment of neuropathic diseases and analgesia in postoperative and chronic pain. However, despite its beneficial use in different clinical settings, further trials and pharmacokinetic studies are needed for the definition of an effective dosage regimen through proper pharmacokinetic/pharmacodynamic correlation in dogs, cats, and horses.

Expression of Cell-Adhesion Molecules in E. coli: A High Throughput Screening to Identify Paracellular Modulators

Cell-adhesion molecules (CAMs) are responsible for cell-cell, cell-extracellular matrix, and cell-pathogen interactions. Claudins (CLDNs), occludin (OCLN), and junctional adhesion molecules (JAMs) are CAMs' components of the tight junction (TJ), the single protein structure tasked with safeguarding the paracellular space. The TJ is responsible for controlling paracellular permeability according to size and charge. Currently, there are no therapeutic solutions to modulate the TJ. Here, we describe the expression of CLDN proteins in the outer membrane of E. coli and report its consequences. When the expression is induced, the unicellular behavior of E. coli is replaced with multicellular aggregations that can be quantified using Flow Cytometry (FC). Our method, called iCLASP (inspection of cell-adhesion molecules aggregation through FC protocols), allows high-throughput screening (HTS) of small-molecules for interactions with CAMs. Here, we focused on using iCLASP to identify paracellular modulators for CLDN2. Furthermore, we validated those compounds in the mammalian cell line A549 as a proof-of-concept for the iCLASP method.

Effects of aqueous extract from Baiyedancong-Oolong tea on cytochrome P450 enzymes activities, P-gp and OATs transport abilities and transcription levels in mice

Introduction

Recent studies have been conducted on its influence on drug metabolism and its potential mechanisms, among which the most studies have been focused on CYP3A enzymes.

Methods

In this study, Baiyedancong Oolong tea (BOT) was processed by freeze- and hot air-drying techniques separately to obtain the aqueous extracts of freeze-and hot-dried BOT (FBOT and HBOT, respectively). High and low doses of FBOT (1463.7 and 292.74 mg/kg/d, respectively) and HBOT (1454.46 mg/kg/d, 290.89, respectively) were administered to mice for 7 days.

Results

Aqueous extracts from BOT simultaneously improved liver CYP3A, CYP2E1, and CYP2C37 activities and weakened the transport ability of P-gp and OATs in a dose-dependent manner, thus affecting multiple links of oral drug metabolism in liver, intestinal absorption and metabolism, and renal excretion. Moreover, aqueous extracts from BOT significantly increased the mRNA expressions of liver CYP3A11 and CYP2C37 as well as intestinal CYP3A11. Decreased transcription levels of MDR1 encoding P-gp in small intestine and renal OAT1 and OAT3, which was in the same direction as the regulation of the above enzyme activities and transport capacities. Besides, the transcription level of liver CYP2E1 was weakened, which was inconsistent with its corresponding enzyme activity, suggesting that the increased CYP2E1 activity may be caused by other mechanisms.

Conclusion

Daily consumption or high dose administration of BOT and its related products may affect drug absorption, metabolisms, and excretion.

Clinical Pharmacokinetics of Approved RNA Therapeutics

RNA-mediated drugs are a rapidly growing class of therapeutics. Over the last five years, the list of FDA-approved RNA therapeutics has expanded owing to their unique targets and prolonged pharmacological effects. Their absorption, distribution, metabolism, and excretion (ADME) have important clinical im-plications, but their pharmacokinetic properties have not been fully understood. Most RNA therapeutics have structural modifications to prevent rapid elimination from the plasma and are administered intravenously or subcutaneously, with some exceptions, for effective distribution to target organs. Distribution of drugs into tissues depends on the addition of a moiety that can be transported to the target and RNA therapeutics show a low volume of distribution because of their molecular size and negatively-charged backbone. Nucleases metabolize RNA therapeutics to a shortened chain, but their metabolic ratio is relatively low. Therefore, most RNA therapeutics are excreted in their intact form. This review covers not only ADME features but also clinical pharmacology data of the RNA therapeutics such as drug-drug interaction or population pharmacokinetic analyses. As the market of RNA therapeutics is expected to rapidly expand, comprehensive knowledge will contribute to interpreting and evaluating the pharmacological properties.

Circulating miR-320a-3p and miR-483-5p level associated with pharmacokinetic-pharmacodynamic profiles of rivaroxaban

BACKGROUND

Novel biomarkers for personalizing anticoagulation remain undetermined. We aimed to investigate the association of plasma miRNAs with pharmacokinetic-pharmacodynamic (PK-PD) profiles of rivaroxaban.

METHODS

This is a multicenter, exploratory study of miRNAs in a Chinese population. Healthy volunteers and patients receiving rivaroxaban were enrolled in the study. The area under the plasma concentration-time curve from time 0-t h (AUC_0-t) and anti-Xa activity at 3 h (AXA_3h) were measured in healthy volunteers, and AXA_3h was measured in patients. MiRNAs were detected by miRNA microarray in 26 healthy volunteers with 20 mg rivaroxaban, and quantitative reverse transcription polymerase chain reaction was used to exclude undetectable ones. MiR-320a-3p and miR-483-5p were then quantified in 65 healthy volunteers and 71 patients. MiRNA levels at 3 h were compared between high and low AXA_3h or AUC_0-t subjects and in matched patients with or without bleeding during follow-up. The miRNA targets were predicted by TargetScan, miRTarBase, and miRDB. Validated genes were included in GO enrichment and KEGG analyses. The protein-protein interaction network was established by STRING and visualized by Cytoscape.

RESULTS

A total of 136 Chinese subjects completed the study. In healthy volunteers taking 15 mg rivaroxaban, the miR-320a level at 3 h was significantly positively correlated with AXA_3h and AUC_0-t (r = 0.359, p = 0.025; r = 0.370, p = 0.02, respectively). A positive correlation was also observed between miR-483 and AXA_3h or AUC_0-t (r = 0.372, p = 0.02; r = 0.523, p = 0.001, respectively). MiR-320a and miR-483 levels at 3 h in the higher AUC_0-t group were significantly higher than those at 0 h. MiR-483 levels at 3 h may distinguish healthy volunteers with high or low AXA_3h or AUC_0-t. In the 10 mg fed subgroup, higher 3 h mir-483 levels were also observed compared with the control group. No significant differences were found in the comparisons among patients. Bioinformatic analysis showed that these miRNAs may play a regulatory role by targeting ABCG2, ITGB3, PTEN, MAPK1/3, etc. CONCLUSIONS: MiR-320a and miR-483 levels were found to be associated with PK and PD profiles of rivaroxaban in healthy Chinese subjects. Further studies are required to verify these findings and explore the mechanisms.

Human Breast Milk Contamination with Aflatoxins, Impact on Children's Health, and Possible Control Means: A Review

Aflatoxins are natural toxicants produced mainly by species of the Aspergillus genus, which contaminate virtually all feeds and foods. Apart from their deleterious health effects on humans and animals, they can be secreted unmodified or carried over into the milk of lactating females, thereby posing health risks to suckling babies. Aflatoxin M1 (AFM1) is the major and most toxic aflatoxin type after aflatoxin B1 (AFB1). It contaminates human breast milk upon direct ingestion from dairy products or by carry-over from the parent molecule (AFB1), which is hydroxylated in the liver and possibly in the mammary glands by cytochrome oxidase enzymes and then excreted into breast milk as AFM1 during lactation via the mammary alveolar epithelial cells. This puts suckling infants and children fed on this milk at a high risk, especially that their detoxifying activities are still weak at this age essentially due to immature liver as the main organ responsible for the detoxification of xenobiotics. The occurrence of AFM1 at toxic levels in human breast milk and associated health conditions in nursing children is well documented, with developing countries being the most affected. Different studies have demonstrated that contamination of human breast milk with AFM1 represents a real public health issue, which should be promptly and properly addressed to reduce its incidence. To this end, different actions have been suggested, including a wider and proper implementation of regulatory measures, not only for breast milk but also for foods and feeds as the upstream sources for breast milk contamination with AFM1. The promotion of awareness of lactating mothers through the organization of training sessions and mass media disclosures before and after parturition is of a paramount importance for the success of any action. This is especially relevant that there are no possible control measures to ensure compliance of lactating mothers to specific regulatory measures, which can yet be appropriate for the expansion of breast milk banks in industrialized countries and emergence of breast milk sellers. This review attempted to revisit the public health issues raised by mother milk contamination with AFM1, which remains undermined despite the numerous relevant publications highlighting the needs to tackle its incidence as a protective measure for the children physical and mental health.

Intracellular Metabolomics Identifies Efflux Transporter Inhibitors in a Routine Caco-2 Cell Permeability Assay-Biological Implications

Caco-2 screens are routinely used in laboratories to measure the permeability of compounds and can identify substrates of efflux transporters. In this study, we hypothesized that efflux transporter inhibition of a compound can be predicted by an intracellular metabolic signature in Caco-2 cells in the assay used to test intestinal permeability. Using selective inhibitors and transporter knock-out (KO) cells and a targeted Liquid Chromatography tandem Mass Spectrometry (LC-MS) method, we identified 11 metabolites increased in cells with depleted P-glycoprotein (Pgp) activity. Four metabolites were altered with Breast Cancer Resistance (BCRP) inhibition and nine metabolites were identified in the Multidrug Drug Resistance Protein 2 (MRP2) signature. A scoring system was created that could discriminate among the three transporters and validated with additional inhibitors. Pgp and MRP2 substrates did not score as inhibitors. In contrast, BCRP substrates and inhibitors showed a similar intracellular metabolomic signature. Network analysis of signature metabolites led us to investigate changes of enzymes in one-carbon metabolism (folate and methionine cycles). Our data shows that methylenetetrahydrofolate reductase (MTHFR) protein levels increased with Pgp inhibition and Thymidylate synthase (TS) protein levels were reduced with Pgp and MRP2 inhibition. In addition, the methionine cycle is also affected by both Pgp and MRP2 inhibition. In summary, we demonstrated that the routine Caco-2 assay has the potential to identify efflux transporter inhibitors in parallel with substrates in the assays currently used in many DMPK laboratories and that inhibition of efflux transporters has biological consequences.

Studying the right transporter at the right time: an in vitro strategy for assessing drug-drug interaction risk during drug discovery and development

INTRODUCTION

Transporters are significant in dictating drug pharmacokinetics, thus inhibition of transporter function can alter drug concentrations resulting in drug-drug interactions (DDIs). Because they can impact drug toxicity, transporter DDIs are a regulatory concern for which prediction of clinical effect from in vitro data is critical to understanding risk.

AREA COVERED

The authors propose in vitro strategies to assist mitigating/removing transporter DDI risk during development by frontloading specific studies, or managing patient risk in the clinic. An overview of clinically relevant drug transporters and observed DDIs are provided, alongside presentation of key considerations/recommendations for in vitro study design evaluating drugs as inhibitors or substrates. Guidance on identifying critical co-medications, clinically relevant disposition pathways and using mechanistic static equations for quantitative prediction of DDI is compiled.

EXPERT OPINION

The strategies provided will facilitate project teams to study the right transporter at the right time to minimise development risks associated with DDIs. To truly alleviate or manage clinical risk, the industry will benefit from moving away from current qualitative basic static equation approaches to transporter DDI hazard assessment towards adopting the use of mechanistic models to enable quantitative DDI prediction, thereby contextualising risk to ascertain whether a transporter DDI is simply pharmacokinetic or clinically significant requiring intervention.

Analyzing the metabolic fate of oral administration drugs: A review and state-of-the-art roadmap

The key orally delivered drug metabolism processes are reviewed to aid the assessment of the current in vivo/vitro experimental systems applicability for evaluating drug metabolism and the interaction potential. Orally administration is the most commonly used state-of-the-art road for drug delivery due to its ease of administration, high patient compliance and cost-effectiveness. Roles of gut metabolic enzymes and microbiota in drug metabolism and absorption suggest that the gut is an important site for drug metabolism, while the liver has long been recognized as the principal organ responsible for drugs or other substances metabolism. In this contribution, we explore various experimental models from their development to the application for studying oral drugs metabolism of and summarized advantages and disadvantages. Undoubtedly, understanding the possible metabolic mechanism of drugs in vivo and evaluating the procedure with relevant models is of great significance for screening potential clinical drugs. With the increasing popularity and prevalence of orally delivered drugs, sophisticated experimental models with higher predictive capacity for the metabolism of oral drugs used in current preclinical studies will be needed. Collectively, the review seeks to provide a comprehensive roadmap for researchers in related fields.

An in-vivo microfluidic assay reveals cardiac toxicity of heavy metals and the protective effect of metal responsive transcription factor (MTF-1) in Drosophila model

Previous toxicity assessments of heavy metals on Drosophila are limited to investigating the survival, development rate, and climbing behaviour by oral administration while cardiac toxicity of these elements have not been investigated. We utilized a microfluidic device to inject known dosages of zinc (Zn) or cadmium (Cd) into the larvae's hemolymph to expose their heart directly and study their heart rate and arrhythmicity. The effect of heart-specific overexpression of metal responsive transcription factor (MTF-1) on different heartbeat parameters and survival of Drosophila larvae was investigated. The heart rate of wild-type larvae decreased by 24.8% or increased by 11.9%, 15 min after injection of 40 nL of 100 mM Zn or 10 mM Cd solution, respectively. The arrhythmicity index of wild-type larvae increased by 58.2% or 76.8%, after injection of Zn or Cd, respectively. MTF-1 heart overexpression ameliorated these effects completely. Moreover, it increased larvae's survival to pupal and adulthood stages and prolonged the longevity of flies injected with Zn and Cd. Our microfluidic-based cardiac toxicity assay illustrated that heart is an acute target of heavy metals toxicity, and MTF-1 overexpression in this tissue can ameliorate cardiac toxicity of Zn and Cd. The method can be used for cardiotoxicity assays with other pollutants in the future.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03336-7.

Causative Role of Anoxic Environment in Bacterial Regulation of Human Intestinal Function

Introduction

Life on Earth depends on oxygen; human tissues require oxygen signaling, whereas many microorganisms, including bacteria, thrive in anoxic environments. Despite these differences, human tissues and bacteria coexist in close proximity to each other such as in the intestine. How oxygen governs intestinal-bacterial interactions remains poorly understood.

Methods

To address to this gap, we created a dual-oxygen environment in a microfluidic device to study the role of oxygen in regulating the regulation of intestinal enzymes and proteins by gut bacteria. Two-layer microfluidic devices were designed using a fluid transport model and fabricated using soft lithography. An oxygen-sensitive material was integrated to determine the oxygen levels. The intestinal cells were cultured in the upper chamber of the device. The cells were differentiated, upon which bacterial strains, a facultative anaerobe, Escherichia coli Nissle 1917, and an obligate anaerobe, Bifidobacterium Adolescentis, were cultured with the intestinal cells.

Results

The microfluidic device successfully established a dual-oxygen environment. Of particular importance in our findings was that both strains significantly upregulated mucin proteins and modulated several intestinal transporters and transcription factors but only under the anoxic-oxic oxygen gradient, thus providing evidence of the role of oxygen on bacterial-epithelial signaling.

Conclusions

Our work that integrates cell and molecular biology with bioengineering presents a novel strategy to engineer an accessible experimental system to provide tailored oxygenated environments. The work could provide new avenues to study intestine-microbiome signaling and intestinal tissue engineering, as well as a novel perspective on the indirect effects of gut bacteria on tissues including tumors.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-022-00735-x.

Revisiting Quantification of Phenylalanine/Tyrosine Flux in the Ochronotic Pathway during Long-Term Nitisinone Treatment of Alkaptonuria

Changes in the phenylalanine (PHE)/tyrosine (TYR) pathway metabolites before and during homogentisic acid (HGA)-lowering by nitisinone in the Suitability of Nitisinone in Alkaptonuria (AKU) 2 (SONIA 2) study enabled the magnitude of the flux in the pathway to be examined. SONIA 2 was a 48-month randomised, open-label, evaluator-blinded, parallel-group study performed in the UK, France and Slovakia recruiting patients with confirmed AKU to receive either 10 mg nitisinone or no treatment. Site visits were performed at 3 months and yearly thereafter. Results from history, photographs of eyes/ears, whole body scintigraphy, echocardiography and abdomen/pelvis ultrasonography were combined to produce the Alkaptonuria Severity Score Index (cAKUSSI). PHE, TYR, hydroxyphenylpyruvate (HPPA), hydroxyphenyllactate (HPLA) and HGA metabolites were analysed by liquid chromatography/tandem mass spectrometry in 24 h urine and serum samples collected before and during nitisinone. Serum metabolites were corrected for total body water (TBW), and the sum of 24 h urine plus total body water metabolites of PHE, TYR, HPPA, HPLA and HGA were determined. The sum of urine metabolites (PHE, TYR, HPPA, HPLA and HGA) were similar pre- and peri-nitisinone. The sum of TBW metabolites and sum TBW + URINE metabolites were significantly higher peri-nitisinone (p < 0.001 for both) compared with pre-nitisinone baseline. Significantly higher concentrations of metabolites from the tyrosine metabolic pathway were observed during treatment with nitisinone. Arguments for unmasking of the ochronotic pathway and biliary elimination of HGA are put forward.

"Mango in all her majesty"-the potential of mangiferin and its analogues in the inhibition of Eimeria tenella hexokinase-a computational approach

The potential of natural products in mitigating infections and diseases are being considered lately. Herein, via in silico methods, we report the possible molecular mechanism of mangiferin (isolated from the fruit, peel, bark and leaves of mango tree) and its derivatives in inhibiting Eimeria tenella hexokinase. We evaluated the binding affinity of these inhibitors to the glucose binding site of EtHK and thereafter proceeded to molecular dynamics simulation. The Molecular Mechanics/Poisson-Boltzmann Surface Area (MM/PBSA) reveals that three of the derivatives (CPAMM, MxPAMM and NAMM) had better total binding free energy than mangiferin. The ADMET and physicochemical properties assessed shows that inhibitors also hold a potential to be drug-likely. Finally, in mediating their inhibitory potentials, the ligands stabilize both the global and local structures of the protein. This study provides a theoretical premise on which the anti-coccidial propensities of mangiferin most especially its derivatives can be investigate in vitro and in vivo.Communicated by Ramaswamy H. Sarma.

Effect of Genetic Variations in Drug-Metabolizing Enzymes and Drug Transporters on the Pharmacokinetics of Rifamycins: A Systematic Review

Background

Rifamycins are a novel class of antibiotics clinically approved for tuberculosis chemotherapy. They are characterized by high inter-individual variation in pharmacokinetics. This systematic review aims to present the contribution of genetic variations in drug-metabolizing enzymes and transporter proteins to the inter-individual variation of rifamycin pharmacokinetics.

Method

We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. The search for relevant studies was done through PubMed, Embase, Web of Science, and Scopus databases. Studies reporting single nucleotide polymorphism in drug transporters and metabolizing enzymes' influence on rifamycin pharmacokinetics were solely included. Two reviewers independently performed data extraction.

Results

The search identified 117 articles of which 15 fulfilled the eligibility criteria and were included in the final data synthesis. The single nucleotides polymorphism in the drug transporters SLCO1B1 rs4149032, rs2306283, rs11045819, and ABCB1 rs1045642 for rifampicin, drug metabolizing enzyme AADAC rs1803155 for rifapentine and CES2 c.-22263A>G (g.738A>G) for rifampicin partly contributes to the variability of pharmacokinetic parameters in tuberculosis patients.

Conclusion

The pharmacokinetics of rifamycins is influenced by genetic variation of drug-metabolizing enzymes and transporters. Controlled clinical studies are, however, required to establish these relationships.

Nano-hydroxyapatite improves intestinal absorption of acetazolamide (BCS Class IV drug)–but how?

We earlier reported that coating poorly water-soluble drugs with nano-hydroxyapatite (nano-HAP) improves bioavailability after oral administration. In the present study, we coated BCS Class IV drug acetazolamide (AZ) with nano-HAP (AZ/HAP formulation), and investigated its bioavailability and nano-HAP’s role in promoting it. We tested AZ bioavailability after a single oral dose of the AZ/HAP formulation in rats, followed by a series of in vitro, ex vivo and in vivo testing. The binding state of AZ and nano-HAP was analyzed by gel filtration chromatography. AZ permeability was studied using a Caco-2 cell monolayer assay kit, to test for tight junction penetration, then using an Ussing chamber mounted with intestinal epithelium, both with and without Peyer’s patch tissue, to examine the role of intracellular transport. Fluorescence-labeled nano-HAP particles were administered orally in rats to investigate their localization in the intestinal tract. The area under the blood concentration time-curve in rats was about 4 times higher in the AZ/HAP formulation group than in the untreated AZ group. Gel filtration analysis showed AZ and nano-HAP were not bound. The Caco-2 study showed equivalent AZ permeability for both groups, but without significant change in transepithelial electrical resistance (TEER), indicating that tight junctions were not penetrated. In the Ussing chamber study, no significant difference in AZ permeability between the two groups was observed for epithelium containing Peyer’s patch tissue, but for epithelium without Peyer’s patch tissue, at high concentration, significantly higher permeability in the AZ/HAP formulation group was observed. Fluorescent labeling showed nano-HAP particles were present in both intestinal villi and Peyer’s patch tissue 30 min after oral administration. Our results suggest that nano-HAP’s enhancement of drug permeability from the small intestine occurs not via tight junctions, but intracellularly, via the intestinal villi. Further study to elucidate the mechanism of this permeability enhancement is required.

State of the Art and Uses for the Biopharmaceutics Drug Disposition Classification System (BDDCS): New Additions, Revisions, and Citation References

The Biopharmaceutics Drug Disposition Classification system (BDDCS) is a four-class approach based on water solubility and extent of metabolism/permeability rate. Based on the BDDCS class to which a drug is assigned, it is possible to predict the role of metabolic enzymes and transporters on the drug disposition of a new molecular entity (NME) prior to its administration to animals or humans. Here, we report a total of 1475 drugs and active metabolites to which the BDDCS is applied. Of these, 379 are new entries, and 1096 are revisions of former classification studies with the addition of references for the approved maximum dose strength, extent of the systemically available drug excreted unchanged in the urine, and lowest solubility over the pH range 1.0–6.8 when such information is available in the literature. We detail revised class assignments of previously misclassified drugs and the literature analyses to classify new drugs. We review the process of solubility assessment for NMEs prior to drug dosing in humans and approved dose classification, as well as the comparison of Biopharmaceutics Classification System (BCS) versus BDDCS assignment. We detail the uses of BDDCS in predicting, prior to dosing animals or humans, disposition characteristics, potential brain penetration, food effect, and drug-induced liver injury (DILI) potential. This work provides an update on the current status of the BDDCS and its uses in the drug development process.

Gutsy science: In vitro systems of the human intestine to model oral drug disposition

The intestine has important gate-keeping functions that can profoundly affect the systemic blood exposure of orally administered drugs. Thus, characterizing a new molecular entity's (NME) disposition within the intestine is of utmost importance in drug development. While currently used in vitro systems, such as Ussing chamber, precision-cut intestinal slices, immortalized cell lines, and primary enterocytes provide substantial knowledge about drug absorption and the intestinal first-pass effect, they remain sub-optimal for quantitatively predicting this process and the oral bioavailability of many drugs. Use of novel in vitro systems such as intestinal organoids and intestinal microphysiological systems have provided substantial advances over the past decade, expanding our understanding of intestinal physiology, pathology, and development. However, application of these emerging in vitro systems in the pharmaceutical science is in its infancy. Preliminary work has demonstrated that these systems more accurately recapitulate the physiology and biochemistry of the intact intestine, as it relates to oral drug disposition, and thus they hold considerable promise as preclinical testing platforms of the future. Here we review currently used and emerging in vitro models of the human intestine employed in pharmaceutical science research. We also highlight aspects of these emerging tools that require further study.

Identification of Common Liver Metabolites of the Natural Bioactive Compound Erinacine A, Purified from Hericium erinaceus Mycelium

Metabolite identification, in the early stage, for compound discovery is necessary to assess the knowledge for the pharmaceutical improvement of drug safety and efficacy. Even if the drug has been released into the market, identification and continuous evaluation of the metabolites are required to avoid the risk of post-marketing withdrawal. Hericium erinaceus (HE), a medicinal mushroom, has broadly documented nutraceutical benefits, including anti-oxidant, anti-tumor, anti-aging, hypolipidemic, and gastric mucosal protection effects. Recently, erinacine A has been reported as the main natural bioactive compound in the mycelium of HE for functional food development. In neurological studies, the consumption of enrinacine A enriched HE mycelium demonstrates its significant nutraceutical effects in Alzheimer’s disease, Parkinson’s disease, and ischemic stroke. For the first time, we explored the metabolic process of erinacine A molecule and identified its metabolites from the rat and human liver S9 fraction. Using a liquid chromatography/triple quadrupole mass spectrometer for quantitative analysis, we observed that 75.44% of erinacine A was metabolized within 60 min in rat, and 32.34% of erinacine A was metabolized within 120 min in human S9. Using an ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS) to identify the metabolites of erinacine A, five common metabolites were identified, and their possible structures were evaluated. Understanding the metabolic process of erinacine A and establishing its metabolite profile database will help promote the nutraceutical application and discovery of related biomarkers in the future.

All layers matter: Innovative three-dimensional epithelium-stroma-endothelium intestinal model for reliable permeability outcomes

Drug development is an ever-growing field, increasingly requesting reliable in vitro tools to speed up early screening phases, reducing the need for animal experiments. In oral delivery, understanding the absorption pattern of a new drug in the small intestine is paramount. Classical two-dimensional (2D) in vitro models are generally too simplistic and do not accurately represent native tissues. The main goal of this work was to develop an advanced three-dimensional (3D) in vitro intestinal model to test absorption in a more reliable manner, by better mimicking the native environment. The 3D model is composed of a collagen-based stromal layer with embedded fibroblasts mimicking the intestinal lamina propria and providing support for the epithelium, composed of enterocytes and mucus-secreting cells. An endothelial layer, surrogating the absorptive capillary network, is also present. The cellular crosstalk between the different cells present in the model is unveiled, disclosing key players, namely those involved in the contraction of collagen by fibroblasts. The developed 3D model presents lower levels of P-glycoprotein (P-gp) and Multidrug Resistance Protein 2 (MRP2) efflux transporters, which are normally overexpressed in traditional Caco-2 models, and are paramount in the absorption of many compounds. This, allied with transepithelial electrical resistance (TEER) values closer to physiological ranges, leads to improved and more reliable permeability outcomes, which are observed when comparing our results with in vivo data.

Sensitive LC-MS/MS Methods for Amphotericin B Analysis in Cerebrospinal Fluid, Plasma, Plasma Ultrafiltrate, and Urine: Application to Clinical Pharmacokinetics

Neurocryptococcosis, a meningoencephalitis caused by Cryptococcus spp, is treated with amphotericin B (AmB) combined with fluconazole. The integrity of the brain-blood barrier and the composition of the cerebrospinal fluid (CSF) may change due to infectious and/or inflammatory diseases such as neurocryptococcosis allowing for the penetration of AmB into the central nervous system. The present study aimed to develop LC-MS/MS methods capable of quantifying AmB in CSF at any given time of the treatment in addition to plasma, plasma ultrafiltrate, with sensitivity compatible with the low concentrations of AmB reported in the CSF. The methods were successfully validated in the four matrices (25 μl, 5-1,000 ng ml-1 for plasma or urine; 100 μl, 0.625-250 ng ml-1 for plasma ultrafiltrate; 100 μl, 0.1-250 ng ml-1 for CSF) using protein precipitation. The methods were applied to investigate the pharmacokinetics of AmB following infusions of 100 mg every 24 h for 16 days administered as a lipid complex throughout the treatment of a neurocryptococcosis male patient. The methods allowed for a detailed description of the pharmacokinetic parameters in the assessed patient in the beginning (4th day) and end of the treatment with AmB (16th day), with total clearances of 7.21 and 4.25 L h-1, hepatic clearances of 7.15 and 4.22 L h-1, volumes of distribution of 302.94 and 206.89 L, and unbound fractions in plasma ranging from 2.26 to 3.25%. AmB was quantified in two CSF samples collected throughout the treatment with concentrations of 12.26 and 18.45 ng ml-1 on the 8th and 15th days of the treatment, respectively. The total concentration of AmB in plasma was 31 and 20 times higher than in CSF. The unbound concentration in plasma accounted for 77 and 44% of the respective concentrations in CSF. In conclusion, the present study described the most complete and sensitive method for AmB analysis in plasma, plasma ultrafiltrate, urine, and CSF applied to a clinical pharmacokinetic study following the administration of the drug as a lipid complex in one patient with neurocryptococcosis. The method can be applied to investigate the pharmacokinetics of AmB in CSF at any given time of the treatment.

Neuroinflammation as a Therapeutic Target in Retinitis Pigmentosa and Quercetin as Its Potential Modulator

The retina is a multilayer neuronal tissue located in the back of the eye that transduces the environmental light into a neural impulse. Many eye diseases caused by endogenous or exogenous harm lead to retina degeneration with neuroinflammation being a major hallmark of these pathologies. One of the most prevalent retinopathies is retinitis pigmentosa (RP), a clinically and genetically heterogeneous hereditary disorder that causes a decline in vision and eventually blindness. Most RP cases are related to mutations in the rod visual receptor, rhodopsin. The mutant protein triggers inflammatory reactions resulting in the activation of microglia to clear degenerating photoreceptor cells. However, sustained insult caused by the abnormal genetic background exacerbates the inflammatory response and increases oxidative stress in the retina, leading to a decline in rod photoreceptors followed by cone photoreceptors. Thus, inhibition of inflammation in RP has received attention and has been explored as a potential therapeutic strategy. However, pharmacological modulation of the retinal inflammatory response in combination with rhodopsin small molecule chaperones would likely be a more advantageous therapeutic approach to combat RP. Flavonoids, which exhibit antioxidant and anti-inflammatory properties, and modulate the stability and folding of rod opsin, could be a valid option in developing treatment strategies against RP.

Identification of the organic anion transporting polypeptides responsible for the hepatic uptake of the major metabolite of epyrifenacil, S-3100-CA, in mice

Epyrifenacil is a novel herbicide that acts as an inhibitor of protoporphyrinogen oxidase (PPO) and produces hepatotoxicity in rodents by inhibiting PPO. Our previous research revealed that the causal substance of hepatotoxicity is S-3100-CA, a major metabolite of epyrifenacil, and that human hepatocyte uptake of S-3100-CA was significantly lower than rodent one, suggesting less relevant to hepatotoxicity in humans. To clarify the species difference in the uptake of S-3100-CA, we focused on organic anion transporting polypeptides (OATPs) and carried out an uptake assay using human, rat, and mouse OATP hepatic isoforms-expressing 293FT cells. As a result, all the examined OATPs were found to contribute to the S-3100-CA uptake, suggesting that the species difference was not due to the differences in selectivity toward OATP isoforms. When [14 C]epyrifenacil was administered to mice, the liver concentration of S-3100-CA was higher in males than in females. Furthermore, when [14 C]epyrifenacil was administered with OATP inhibitors, the liver/plasma ratio of S-3100-CA was significantly decreased by rifampicin, an Oatp1a1/Oatp1a4 inhibitor in mice, but not by digoxin, an Oatp1a4-specific inhibitor. This result indicates that Oatp1a1, the predominant transporter in male mice, is the main contributor to the hepatic transport of S-3100-CA, and consequently to the gender difference. Moreover, we conclude that the species difference in the hepatic uptake of S-3100-CA observed in our previous research is not due to differences in the selectivity toward OATP isoforms but rather to the significantly higher expression of OATPs which mediate uptake of S-3100-CA in rodents than in humans.

Fed or fasted state for oral therapies in breast cancer treatment? A comprehensive review of clinical practice recommendations

In the last decades several anti-cancer drugs have been developed to treat patients with breast cancer, many of them orally administered, with ongoing efforts to substitute parenteral drugs with oral therapy. The latter is attractive because of its convenience and ease of administration, finally improving quality of life. The drawback of oral administration is that exposure to the drug is affected by different factors and the high variability, combined with the relatively narrow therapeutic index of most of these agents, would predispose some individuals to risk for treatment inefficacy or increase toxicity. Among these factors, food plays a central role since it can influence the pharmacokinetic profile of several drugs. Consequently, health care providers and patients should be aware of possible interaction to optimize treatment. In this review a systematic evaluation of package inserts and literature have been performed to analyse the effect of fed or fasted state on pharmacokinetic of all oral drugs currently approved for breast cancer, offering clear recommendations for their use daily practice.

Review of Transporter Substrate, Inhibitor, and Inducer Characteristics of Cladribine

Cladribine is a nucleoside analog that is phosphorylated in its target cells (B- and T-lymphocytes) to its active adenosine triphosphate form (2-chlorodeoxyadenosine triphosphate). Cladribine tablets 10 mg (Mavenclad^®) administered for up to 10 days per year in 2 consecutive years (3.5-mg/kg cumulative dose over 2 years) are used to treat patients with relapsing multiple sclerosis. The ATP-binding cassette, solute carrier, and nucleoside transporter substrate, inhibitor, and inducer characteristics of cladribine are reviewed in this article. Available evidence suggests that the distribution of cladribine across biological membranes is facilitated by a number of uptake and efflux transporters. Among the key ATP-binding cassette efflux transporters, only breast cancer resistance protein has been shown to be an efficient transporter of cladribine, while P-glycoprotein does not transport cladribine well. Intestinal absorption, distribution throughout the body, and intracellular uptake of cladribine appear to be exclusively mediated by equilibrative and concentrative nucleoside transporters, specifically by ENT1, ENT2, ENT4, CNT2 (low affinity), and CNT3. Renal excretion of cladribine appears to be most likely driven by breast cancer resistance protein, ENT1, and P-glycoprotein. The latter may play a role despite its poor cladribine transport efficiency in view of the renal abundance of P-glycoprotein. There is no evidence that solute carrier uptake transporters such as organic anion transporting polypeptides, organic anion transporters, and organic cation transporters are involved in the transport of cladribine. Available in vitro studies examining the inhibitor characteristics of cladribine for a total of 13 major ATP-binding cassette, solute carrier, and CNT transporters indicate that in vivo inhibition of any of these transporters by cladribine is unlikely.

Inherent Dangers of Using Non-US Food and Drug Administration-Approved Substances of Abuse

Use of US Food and Drug Administration-approved substances of abuse has innate risks due to pharmacologic and pharmacokinetic properties of the medications, but the risk when using nonapproved drug products is much greater. Unbeknownst to the user, the dose of active ingredients in substances of abuse can vary substantially between different products because of manufacturing practices or improper storage. Even naturally occurring substances of abuse can have extensive dosage variability because of effects of the growing season and conditions, or differences in harvesting, storage, or manufacture of the finished products. Many illicit substances are adulterated, to make up for intentional underdosing or to enhance the effect of the intended active ingredient. These adulterants can be dangerous and produce direct cardiovascular, neurologic, hematologic, or dermatologic reactions or obscure adverse effects. Finally, an illicit substance can be contaminated or substituted for another one during its manufacture, leading to differences in adverse events, adverse event severity, or the drug interaction profile. Substances can be contaminated with microbes that induce infections or heavy metals that can damage organs or cause cancer. This milieu of undisclosed substances can also induce drug interactions. For reasons that are discussed, individuals who use substances of abuse are at increased risk of morbidity or mortality if they develop coronavirus disease 2019. Health professionals who treat patients with acute, urgent events associated with substances of abuse, or those treating the chronic manifestations of addiction, need to appreciate the complex and variable composition of substances of abuse and their potential health effects.

Species Differences in Metabolism of Soluble Epoxide Hydrolase Inhibitor, EC1728, Highlight the Importance of Clinically Relevant Screening Mechanisms in Drug Development

There are few novel therapeutic options available for companion animals, and medications rely heavily on repurposed drugs developed for other species. Considering the diversity of species and breeds in companion animal medicine, comprehensive PK exposures in the companion animal patient is often lacking. The purpose of this paper was to assess the pharmacokinetics after oral and intravenous dosing in domesticated animal species (dogs, cats, and horses) of a novel soluble epoxide hydrolase inhibitor, EC1728, being developed for the treatment of pain in animals. Results: Intravenous and oral administration revealed that bioavailability was similar for dogs, and horses (42 and 50% F) but lower in mice and cats (34 and 8%, respectively). Additionally, clearance was similar between cats and mice, but >2× faster in cats vs. dogs and horses. Efficacy with EC1728 has been demonstrated in mice, dogs, and horses, and despite the rapid clearance of EC1728 in cats, analgesic efficacy was demonstrated in an acute pain model after intravenous but not oral dosing. Conclusion: These results demonstrate that exposures across species can vary, and investigation of therapeutic exposures in target species is needed to provide adequate care that addresses efficacy and avoids toxicity.

Effects of Single Dose Rifampin on the Pharmacokinetics of Fluvastatin in Healthy Volunteers

The objective of this study was to determine the effects of the OATP inhibitor rifampin on pharmacokinetic of Biopharmaceutics Drug Disposition Classification System Class 1 compound fluvastatin. A crossover study was carried out in 10 healthy subjects who were randomized to 2 phases to receive fluvastatin 20 mg orally alone and following a 30-minute 600 mg i.v. infusion of rifampin. The results demonstrated that i.v. rifampin increased the mean area under the plasma fluvastatin concentration-time curve (AUC0-∞ ) by 255%, mean peak plasma concentration (Cmax ) by 254%, decreased oral volume of distribution by 71%, whereas the mean elimination terminal half-life (T1/2 ), mean absorption time (MAT), and time to peak concentration (Tpeak ) of fluvastatin did not significantly change. The study demonstrated that rifampin exhibited a significant drug interaction with fluvastatin. The mechanism of the increased plasma concentrations is likely due to inhibition of OATP transporters in hepatocytes.

An update on oral drug delivery via intestinal lymphatic transport

Orally administered drug entities have to survive the harsh gastrointestinal environment, penetrate the enteric epithelia and circumvent hepatic metabolism before reaching the systemic circulation. Whereas the gastrointestinal stability can be well maintained by taking proper measures, hepatic metabolism presents as a formidable barrier to drugs suffering from first-pass metabolism. The pharmaceutical academia and industries are seeking alternative pathways for drug transport to circumvent problems associated with the portal pathway. Intestinal lymphatic transport is emerging as a promising pathway to this end. In this review, we intend to provide an updated overview on the rationale, strategies, factors and applications involved in intestinal lymphatic transport. There are mainly two pathways for peroral lymphatic transport-the chylomicron and the microfold cell pathways. The underlying mechanisms are being unraveled gradually and nowadays witness increasing research input and applications.

Intestinal Excretion, Intestinal Recirculation, and Renal Tubule Reabsorption Are Underappreciated Mechanisms That Drive the Distribution and Pharmacokinetic Behavior of Small Molecule Drugs

Drug reabsorption following biliary excretion is well-known as enterohepatic recirculation (EHR). Renal tubular reabsorption (RTR) following renal excretion is also common but not easily assessed. Intestinal excretion (IE) and enteroenteric recirculation (EER) have not been recognized as common disposition mechanisms for metabolically stable and permeable drugs. IE and intestinal reabsorption (IR:EHR/EER), as well as RTR, are governed by dug concentration gradients, passive diffusion, active transport, and metabolism, and together they markedly impact disposition and pharmacokinetics (PK) of small molecule drugs. Disruption of IE, IR, or RTR through applications of active charcoal (AC), transporter knockout (KO), and transporter inhibitors can lead to changes in PK parameters. The impacts of intestinal and renal reabsorption on PK are under-appreciated. Although IE and EER/RTR can be an intrinsic drug property, there is no apparent strategy to optimize compounds based on this property. This review seeks to improve understanding and applications of IE, IR, and RTR mechanisms.

Changes in digoxin pharmacokinetics associated with hepatic P-glycoprotein upregulation in rats with non-alcoholic fatty liver disease

BACKGROUND & OBJECTIVES

Upregulation of hepatic P-glycoprotein (P-gp) expression has been reported in patients with non-alcoholic fatty liver disease (NAFLD) and rodent models thereof. Here, we explored the changes hepatic P-gp expression and activity in a NAFLD rat model and the effects thereof on the pharmacokinetics of digoxin (a probe substrate of P-gp).

METHODS

Rats were fed a 1% (w/w) orotic acid-containing diet for 20 days to induce NAFLD; control rats received a normal diet. P-gp expression and biliary digoxin excretion were examined. The pharmacokinetics of digoxin were evaluated after it had been administered intravenously (10 μg·kg^-1 ) and orally (200 μg·kg^-1 ) to control and NAFLD rats.

RESULTS

The total areas under the plasma concentration-time curves (AUCs) of digoxin after intravenous and oral administration were significantly smaller (by 39.1% and 73.0%, respectively) in NAFLD rats because of faster biliary digoxin excretion, reflecting elevations of hepatic P-gp expression and activity. Notably, the steady-state volume of distribution rose by 98.2%, while extent of oral bioavailability fell by 55.5% in NAFLD rats.

CONCLUSION

This is the first study to report digoxin pharmacokinetic changes caused by hepatic P-gp upregulation in NAFLD. Further studies are needed to explore the clinical impact of enhanced P-gp-mediated biliary excretion on pharmacotherapies using P-gp substrates in patients with NAFLD.

Development of a Pediatric Relative Bioavailability/Bioequivalence Database and Identification of Putative Risk Factors Associated With Evaluation of Pediatric Oral Products

Generally, bioequivalence (BE) studies of drug products for pediatric patients are conducted in adults due to ethical reasons. Given the lack of direct BE assessment in pediatric populations, the aim of this work is to develop a database of BE and relative bioavailability (relative BA) studies conducted in pediatric populations and to enable the identification of risk factors associated with certain drug substances or products that may lead to failed BE or different pharmacokinetic (PK) parameters in relative BA studies in pediatrics. A literature search from 1965 to 2020 was conducted in PubMed, Cochrane Library, and Google Scholar to identify BE studies conducted in pediatric populations and relative BA studies conducted in pediatric populations. Overall, 79 studies covering 37 active pharmaceutical ingredients (APIs) were included in the database: 4 bioequivalence studies with data that passed BE evaluations; 2 studies showed bioinequivalence results; 34 relative BA studies showing comparable PK parameters, and 39 relative BA studies showing differences in PK parameters between test and reference products. Based on the above studies, common putative risk factors associated with differences in relative bioavailability (DRBA) in pediatric populations include age-related absorption effects, high inter-individual variability, and poor study design. A database containing 79 clinical studies on BE or relative BA in pediatrics has been developed. Putative risk factors associated with DRBA in pediatric populations are summarized.

Investigating Intestinal Transporter Involvement in Rivaroxaban Disposition through Examination of Changes in Absorption

PURPOSE

The involvement of the intestinally expressed xenobiotic transporters P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) have been implicated in rivaroxaban disposition based on in vitro studies, similar to what had previously been proposed for apixaban. We recently showed that these efflux transporters were not clinically relevant for apixaban disposition and examine here their relevance for this second Factor Xa inhibitor.

METHODS

Using recently published methodologies to discern metabolic- from transporter- mediated drug interactions, a critical evaluation was undertaken of 9 rivaroxaban studies reporting 12 DDIs, one study of food effects and one study of hepatic function.

RESULTS

Rationale examination of these clinical studies using basic pharmacokinetic theory finds little support for the clinical significance of intestinal efflux transporters in rivaroxaban disposition. Drug-drug interactions are most likely adequately predicted based on the level of CYP 3A metabolism.

CONCLUSION

These analyses indicate that inhibition of efflux transporters appears to have negligible, clinically insignificant effects on the rivaroxaban absorption process, which is consistent with the concern that predictions based on in vitro measures may not translate to a clinically relevant interaction in vivo. We emphasize the need to evaluate gastric emptying, dissolution and other processes related to absorption when using MAT changes to indicate efflux transporter inhibition.

Phosphonofluoresceins: Synthesis, Spectroscopy, and Applications

Xanthene fluorophores, like fluorescein, have been versatile molecules across diverse fields of chemistry and life sciences. Despite the ubiquity of 3-carboxy and 3-sulfonofluorescein for the last 150 years, to date, no reports of 3-phosphonofluorescein exist. Here, we report the synthesis, spectroscopic characterization, and applications of 3-phosphonofluoresceins. The absorption and emission of 3-phosphonofluoresceins remain relatively unaltered from the parent 3-carboxyfluorescein. 3-Phosphonofluoresceins show enhanced water solubility compared to 3-carboxyfluorescein and persist in an open, visible light-absorbing state even at low pH and in low dielectric media while 3-carboxyfluoresceins tend to lactonize. In contrast, the spirocyclization tendency of 3-phosphonofluoresceins can be modulated by esterification of the phosphonic acid. The bis-acetoxymethyl ester of 3-phosphonofluorescein readily enters living cells, showing excellent accumulation (>6x) and retention (>11x), resulting in a nearly 70-fold improvement in cellular brightness compared to 3-carboxyfluorescein. In a complementary fashion, the free acid form of 3-phosphonofluorescein does not cross cellular membranes, making it ideally suited for incorporation into a voltage-sensing scaffold. We develop a new synthetic route to functionalized 3-phosphonofluoresceins to enable the synthesis of phosphono-voltage sensitive fluorophores, or phosVF2.1.Cl. Phosphono-VF2.1.Cl shows excellent membrane localization, cellular brightness, and voltage sensitivity (26% ΔF/F per 100 mV), rivaling that of sulfono-based VF dyes. In summary, we develop the first synthesis of 3-phosphonofluoresceins, characterize the spectroscopic properties of this new class of xanthene dyes, and utilize these insights to show the utility of 3-phosphonofluoresceins in intracellular imaging and membrane potential sensing.

The effect of hypergravity in intestinal permeability of nanoformulations and molecules

The oral administration of drugs remains a challenge due to rapid enzymatic degradation and minimal absorption in the gastrointestinal tract. Mechanical forces, namely hypergravity, can interfere with cellular integrity and drug absorption, and there is no study describing its influence in the intestinal permeability. In this work, it was studied the effect of hypergravity on intestinal Caco-2 cells and its influence in the intestinal permeability of different nanoformulations and molecules. It was shown that the cellular metabolic activity and integrity were maintained after exposure to different gravity-levels (g-levels). Expression of important drug transporters and tight junctions' proteins was evaluated and, most proteins demonstrated a switch of behavior in their expression. Furthermore, paracellular transport of FITC-Dextran showed to significantly increase with hypergravity, which agrees with the decrease of transepithelial electrical resistance and the increase of claudin-2 at higher g-levels. The diffusion of camptothecin released from polymeric micelles revealed a significant decrease, which agrees with the increased expression of the P-gp observed with the increase in g-levels, responsible for pumping this drug out. The neonatal Fc receptor-mediated transport of albumin-functionalized nanoparticles loaded with insulin showed no significant changes when increasing the g-levels. Thus, this study supports the effect of hypergravity on intestinal permeability is dependent on the molecule studied and the mechanism by which it is absorbed in the intestine.

Advances in Oral Drug Delivery

The oral route is the most common route for drug administration. It is the most preferred route, due to its advantages, such as non-invasiveness, patient compliance and convenience of drug administration. Various factors govern oral drug absorption including drug solubility, mucosal permeability, and stability in the gastrointestinal tract environment. Attempts to overcome these factors have focused on understanding the physicochemical, biochemical, metabolic and biological barriers which limit the overall drug bioavailability. Different pharmaceutical technologies and drug delivery systems including nanocarriers, micelles, cyclodextrins and lipid-based carriers have been explored to enhance oral drug absorption. To this end, this review will discuss the physiological, and pharmaceutical barriers influencing drug bioavailability for the oral route of administration, as well as the conventional and novel drug delivery strategies. The challenges and development aspects of pediatric formulations will also be addressed.