Nonionic surfactants modulate the transport activity of ATP-binding cassette (ABC) transporters and solute carriers (SLC): Relevance to oral drug absorption

Single-dose comparative pharmacokinetic/pharmacodynamic study of a micellar formulation versus a native Boswellia serrata dry extract in healthy volunteers

BACKGROUND

Extracts of oleogum resins of Boswellia trees possess anti-inflammatory activities. Micellar formulations have been developed to increase the oral bioavailability of bioactive boswellic and lupeolic acids.

PURPOSE

The current single-dose crossover clinical trial compares for the first time pharmacokinetics/pharmacodynamics of two Boswellia serrata nutraceuticals, native Biotikon® BS-85 and micellar Boswellia-Loges®.

METHODS

After oral administration of the study preparations (800 mg) to 20 healthy volunteers, plasma concentrations of 8 boswellic and lupeolic acids were measured by using HPLC-MS/MS for up to 48 h Blood samples collected 2 and 5 h after drug administration were stimulated for 24 h with endotoxic lipopolysaccharide. The release of proinflammatory cytokines analyzed by flow cytometry was used as readout of the pharmacodynamic properties of the preparations.

REGISTRATION

German Clinical Trials Register (DRKS) No. DRKS00027369.

RESULTS

Administration of the micellar extract significantly increased Cmax, AUC0-48, and shortened Tmax for all boswellic and lupeolic acids compared to native extract. Accordingly, their relative bioavailability increased to 1,720-4,291 % with the highest difference for acetyl-11-keto-β-boswellic acid (AKBA). Both preparations reduced the release of TNF-α and the native formulation diminished also IL-1β and IL-6. However, no significant differences were observed between the preparations, except for a higher decrease in IL-1β by the native formulation Biotikon® BS-85. In a lymphocytic gene reporter cell line, both nutraceuticals similarly inhibited the NF-κB transcription factor activity as well as the TNF-α release, yet the native formulation Biotikon®BS-85 was more efficient in inhibiting TNF-α.

CONCLUSION

Administration of the micellar Boswellia serrata nutraceutical increased the oral bioavailability of boswellic and lupeolic acids. Yet, the increase in plasma concentration did not enhance the anti-inflammatory efficacy of the micellar extract compared to the native extract in this ex vivo model.

Effects of Commonly used Surfactants, Poloxamer 188 and Tween 80, on the Drug Transport Capacity of Intestinal Glucose Transporters

Some glycoside drugs can be transported through intestinal glucose transporters (IGTs). The surfactants used in oral drug preparations can affect the function of transporter proteins. This study aimed to investigate the effect of commonly used surfactants, Poloxamer 188 and Tween 80, on the drug transport capacity of IGTs. Previous studies have shown that gastrodin is the optimal drug substrate for IGTs. Gastrodin was used as a probe drug to evaluate the effect of these two surfactants on intestinal absorption in SD rats through pharmacokinetic and in situ single-pass intestinal perfusion. Then, the effects of the two surfactants on the expression of glucose transporters and tight-junction proteins were examined using RT-PCR and western blotting. Additionally, the effect of surfactants on intestinal permeability was evaluated through hematoxylin-eosin staining. The results found that all experimental for Poloxamer 188 (0.5%, 2.0% and 8.0%) and Tween 80 (0.1% and 2.0%) were not significantly different from those of the blank group. However, the AUC(0-∞) of gastrodin increased by approximately 32% when 0.5% Tween 80 was used. The changes in IGT expression correlated with the intestinal absorption of gastrodin. A significant increase in the expression of IGTs was observed at 0.5% Tween 80. In conclusion, Poloxamer 188 had minimal effect on the drug transport capacity of IGTs within the recommended limits of use. However, the expression of IGTs increased in response to 0.5% Tween 80, which significantly enhanced the drug transport capacity of IGTs. However, 0.1% and 2.0% Tween 80 had no significant effect.

Digestion of surfactants does not affect their ability to inhibit P-gp-mediated transport in vitro

While various non-ionic surfactants at low concentrations have been shown to increase the transport of P-gp substrates in vitro, in vivo studies in rats have shown that a higher surfactant concentration is needed to increase the oral absorption of e.g. the P-gp substrates digoxin and etoposide. The aim of the present study was to investigate if intestinal digestion of surfactants could be the reason for this deviation between in vitro and in vivo data. Therefore, Kolliphor EL, Brij-L23, Labrasol and polysorbate 20 were investigated for their ability to inhibit P-gp and increase digoxin absorption in vitro. Transport studies were performed in Caco-2 cells, while P-gp inhibition and cell viability assays were performed in MDCKII-MDR1 cells. Polysorbate 20, Kolliphor EL and Brij-L23 increased absorptive transport and decreased secretory digoxin transport in Caco-2 cells, whereas only polysorbate 20 and Brij-L23 showed P-gp inhibiting properties in the MDCKII-MDR1 cells. Polysorbate 20 and Brij-L23 were chosen for in vitro digestion prior to transport- or P-gp inhibiting assays. Brij-L23 was not digestible, whereas polysorbate 20 reached a degree of digestion around 40%. Neither of the two surfactants showed any significant difference in their ability to affect absorptive or secretory transport of digoxin after pre-digestion. Furthermore, the P-gp inhibiting effects of polysorbate 20 were not decreased significantly. In conclusion, the mechanism behind the non-ionic surfactant mediated in vitro P-gp inhibition seemed independent of the intestinal digestion and the results presented here did not suggest it to be the cause of the observed discrepancy between in vitro and in vivo.

Redefine the role of d-α-Tocopheryl polyethylene glycol 1000 succinate on P-glycoprotein, multidrug resistance protein 1, and breast cancer resistance protein mediated cancer multidrug resistance

Cancer drug resistance is an ever-changing problem that most patients need to face in their later stages of treatment, especially the multidrug resistant (MDR) type. The drug efflux transporters, including P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), and breast cancer resistance protein (BCRP), play the crucial roles in this sophisticated battle. In recent decades, researchers try to find potential inhibitors to impede the drug efflux function of above transporters. d-α-Tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS) is a prevalently used excipient in the formulation design. In the present study, the modulatory effects and mechanisms of vitamin E TPGS on the efflux transporters were investigated. And the cancer MDR reversing ability of vitamin E TPGS was evaluated as well. Stable-cloned transporter over-expressed cell lines were used for mechanisms study, while several types of MDR cancer cell lines were adopted as reversing evaluation models. The results exhibited that vitamin E TPGS significantly inhibited the efflux function of P-gp, MRP1, and BCRP under non-cytotoxic concentrations, but not influencing the protein expression levels. Through efflux assay and molecular docking, vitamin E TPGS was found to be an uncompetitive, non-competitive, and competitive inhibitor on chemotherapeutic drug doxorubicin efflux in P-gp, MRP1, and BCRP over-expressing cell lines, respectively. Furthermore, the basal ATPase activity of three transporters were significantly inhibited by vitamin E TPGS at 10 μM. And the cell membrane fluidity of P-gp over-expressing cell line was enhanced by 22.58% with 5 μM vitamin E TPGS treatment, compared to the parental Flp-In™-293 cell line (without P-gp). The resistance reversing ability of vitamin E TPGS was prominent in MCF-7/DOX MDR breast cancer cell line, which over-expressed P-gp, MRP1, and BCRP. These significant results suggested that vitamin E TPGS is a promising modulator on transporters mediated cancer MDR. Vitamin E TPGS is not an inert excipient, but possesses MDR-reversing pharmacological effects, and deserves a re-purposing application on the future combinatorial regimen design for MDR cancer treatment.

Recent advances in access to overcome cancer drug resistance by nanocarrier drug delivery system

Cancer is currently one of the most intractable diseases causing human death. Although the prognosis of tumor patients has been improved to a certain extent through various modern treatment methods, multidrug resistance (MDR) of tumor cells is still a major problem leading to clinical treatment failure. Chemotherapy resistance refers to the resistance of tumor cells and/or tissues to a drug, usually inherent or developed during treatment. Therefore, an urgent need to research the ideal drug delivery system to overcome the shortcoming of traditional chemotherapy. The rapid development of nanotechnology has brought us new enlightenments to solve this problem. The novel nanocarrier provides a considerably effective treatment to overcome the limitations of chemotherapy or other drugs resulting from systemic side effects such as resistance, high toxicity, lack of targeting, and off-target. Herein, we introduce several tumor MDR mechanisms and discuss novel nanoparticle technology applied to surmount cancer drug resistance. Nanomaterials contain liposomes, polymer conjugates, micelles, dendrimers, carbon-based, metal nanoparticles, and nucleotides which can be used to deliver chemotherapeutic drugs, photosensitizers, and small interfering RNA (siRNA). This review aims to elucidate the advantages of nanomedicine in overcoming cancer drug resistance and discuss the latest developments.

Combinational Inhibition of P-Glycoprotein-Mediated Etoposide Transport by Zosuquidar and Polysorbate 20

P-glycoprotein (P-gp) limits the oral absorption of drug substances. Potent small molecule P-gp inhibitors (e.g., zosuquidar) and nonionic surfactants (e.g., polysorbate 20) inhibit P-gp by proposedly different mechanisms. Therefore, it was hypothesised that a combination of zosuquidar and polysorbate 20 may potentiate inhibition of P-gp-mediated efflux. P-gp inhibition by zosuquidar and polysorbate 20 in combination was assessed in a calcein-AM assay and in a transcellular etoposide permeability study in MDCKII-MDR1 and Caco-2 cells. Furthermore, solutions of etoposide, zosuquidar, and polysorbate 20 were orally administered to Sprague Dawley rats. Zosuquidar elicited a high level of nonspecific adsorption to various labware, which significantly affected the outcomes of the in vitro studies. Still, at certain zosuquidar and polysorbate 20 concentrations, additive P-gp inhibition was observed in vitro. In vivo, however, oral etoposide bioavailability decreased by coadministration of both zosuquidar and polysorbate 20 when compared to coadministration of etoposide with zosuquidar alone. For future formulation development, the present study provided important and novel knowledge about nonspecific zosuquidar adsorption, as well as insights into combinational P-gp inhibition by a third-generation P-gp inhibitor and a P-gp-inhibiting nonionic surfactant.

Interaction of a Homologous Series of Amphiphiles with P-glycoprotein in a Membrane Environment-Contributions of Polar and Non-Polar Interactions

The transport of drugs by efflux transporters in biomembranes limits their bioavailability and is a major determinant of drug resistance development by cancer cells and pathogens. A large number of chemically dissimilar drugs are transported, and despite extensive studies, the molecular determinants of substrate specificity are still not well understood. In this work, we explore the role of polar and non-polar interactions on the interaction of a homologous series of fluorescent amphiphiles with the efflux transporter P-glycoprotein. The interaction of the amphiphiles with P-glycoprotein is evaluated through effects on ATPase activity, efficiency in inhibition of [¹²⁵I]-IAAP binding, and partition to the whole native membranes containing the transporter. The results were complemented with partition to model membranes with a representative lipid composition, and details on the interactions established were obtained from MD simulations. We show that when the total concentration of amphiphile is considered, the binding parameters obtained are apparent and do not reflect the affinity for P-gp. A new formalism is proposed that includes sequestration of the amphiphiles in the lipid bilayer and the possible binding of several molecules in P-gp's substrate-binding pocket. The intrinsic binding affinity thus obtained is essentially independent of amphiphile hydrophobicity, highlighting the importance of polar interactions. An increase in the lipophilicity and amphiphilicity led to a more efficient association with the lipid bilayer, which maintains the non-polar groups of the amphiphiles in the bilayer, while the polar groups interact with P-gp's binding pocket. The presence of several amphiphiles in this orientation is proposed as a mechanism for inhibition of P-pg function.

The Rat Continuous Intestine Model Predicts the Impact of Particle Size and Transporters on the Oral Absorption of Glyburide

Oral drug absorption is known to be impacted by the physicochemical properties of drugs, properties of oral formulations, and physiological characteristics of the intestine. The goal of the present study was to develop a mathematical model to predict the impact of particle size, feeding time, and intestinal transporter activity on oral absorption. A previously published rat continuous intestine absorption model was extended for solid drug absorption. The impact of active pharmaceutical ingredient particle size was evaluated with glyburide (GLY) as a model drug. Two particle size suspensions of glyburide were prepared with average particle sizes of 42.7 and 4.1 μm. Each suspension was dosed as a single oral gavage to male Sprague Dawley rats, and concentration-time (C-t) profiles of glyburide were measured with liquid chromatography coupled with tandem mass spectrometry. A continuous rat intestine absorption model was extended to include drug dissolution and was used to predict the absorption kinetics of GLY depending on particle size. Additional literature datasets of rat GLY formulations with particle sizes ranging from 0.25 to 4.0 μm were used for model predictions. The model predicted reasonably well the absorption profiles of GLY based on varying particle size and varying feeding time. The model predicted inhibition of intestinal uptake or efflux transporters depending on the datasets. The three datasets used formulations with different excipients, which may impact the transporter activity. Model simulations indicated that the model provides a facile framework to predict the impact of transporter inhibition on drug C-t profiles. Model simulations can also be conducted to evaluate the impact of an altered intestinal lumen environment. In conclusion, the rat continuous intestine absorption model may provide a useful tool to predict the impact of varying drug formulations on rat oral absorption profiles.

Safety and efficacy of a feed additive consisting of glyceryl polyethyleneglycol ricinoleate (PEG castor oil) for all animal species (FEFANA asbl)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of glyceryl polyethyleneglycol ricinoleate (PEG castor oil) as technological feed additive for all animal species. PEG castor oil is safe at a maximum concentration in complete feed of 90 mg/kg for chickens for fattening and other minor growing poultry; 134 mg/kg for laying hens and other laying/breeding birds kept for egg production/reproduction; 121 mg/kg for turkeys for fattening; 162 mg/kg for piglets and other minor growing Suidae; 194 mg/kg for pigs for fattening; 236 mg/kg for sows other minor reproductive Suidae; 231 mg/kg for dairy cows and other dairy ruminants (other than sheep/goats); 142 mg/kg in rabbits and 377 mg/kg in veal calves; 356 mg/kg for cattle for fattening and other growing ruminants, sheep, goat, horses and cats; 427 mg/kg for dogs; 407 mg/kg for salmonids and other fin fish; and 1,584 mg/kg for ornamental fish. For other growing species and non-food producing animals, the additive is considered safe at 90 mg/kg complete feed. The use of PEG castor oil as feed additive for all animal species would be of no concern for the consumer. The FEEDAP Panel considered inhalation exposure of the user to the additive unlikely. PEG castor oil is not considered a skin sensitiser. The panel was not in the position to conclude on the potential of the additive to be a skin or eye irritant. The additive is a readily biodegradable substance and is not expected to pose a risk for the environment. The lack of sufficient data does not allow the FEEDAP Panel to conclude on the efficacy of PEG castor oil as an emulsifier in feedingstuffs.

Investigation of the “Nose-to-Brain” Pathways in Intranasal HupA Nanoemulsions and Evaluation of Their in vivo Pharmacokinetics and Brain-Targeting Ability

Purpose

While developing huperzine A (HupA) to explore new approaches to treating Alzheimer’s disease (AD), intranasal administration was proposed as an alternative route to deliver drugs into the brain. This study aimed to prepare nanoemulsions (NEs) of HupA to investigate their potential “nose-to-brain” pathways and to evaluate their pharmacokinetic and brain-targeting parameters.

Methods

HupA-NE and Lf-HupA-NE that underwent surface modification with lactoferrin (Lf) were characterized to determine various physicochemical properties, such as their size, PDI, zeta potential, pH, and loading efficiency; in addition, transmission electron microscopy and stability assessments were performed. We utilized an aggregation-caused quenching (ACQ) probe to monitor intact NEs in the brains of olfactory nerve transection model and normal rats. Immunohistochemistry, pharmacokinetic and targeting index analyses were performed to investigate the in vivo effects of HupA-NE and Lf-HupA-NE.

Results

Based on the live imaging results, HupA-NE and Lf-HupA-NE could be transported into the brain via nerve and blood circulation pathways. Immunohistochemical staining tests demonstrated that the efflux proteins P-gp, MRP1, and BCRP were expressed in brain tissue. NEs can inhibit efflux pumps to improve drug concentrations in the brain. The findings of this study showed that NEs (especially Lf-HupA-NE) had better pharmacokinetic profiles and a better nose-to-brain drug transport efficiency than free HupA.

Conclusion

The newly designed formulations might contribute to the transport and accumulation of HupA to achieve therapeutic results. The delivery system may be a promising strategy for the brain-targeted delivery of HupA.

P-glycoprotein-mediated transport in a mucus-supplemented Caco-2 cell model in the presence of different surfactants

The aim of the present study was to investigate if mucus applied to Caco-2 cell monolayers protects cells from high concentrations of surfactants, while still allowing for an identification of the surfactant's inhibitory effects on P-glycoprotein (P-gp). Two types of porcine mucin and six surfactants (Polysorbate 20 (PS20) and 80 (PS80), Kolliphor EL (Kol. EL) and RH40 (Kol. RH40), Labrafil M 2125 CS (L.fil) and Labrasol (L.sol)) were applied to Caco-2 cells, and TEER, paracellular transport and P-gp mediated digoxin transport was measured. The results showed that 15% porcine mucin type II was incompatible with Caco-2 cell monolayer integrity, resulting in a dramatic drop in monolayer TEER and increased mannitol transport. In contrast, mucin type III was compatible with Caco-2 cell monolayers in the concentration range of 2.5-15% without substantially disturbing barrier properties. The highest concentration of mucin type III impaired the ability of all six surfactants to decrease P-gp mediated digoxin transport. Subsequently lowering the mucin concentration to 5% facilitated adequate protection of cells and enabled e.g., 5% PS20 to inhibit P-gp mediated digoxin transport. Overall, the present work is useful for early-stage permeability investigations on how mucus affects P-gp mediated transport in the presence of formulation excipients.

Mechanism behind Polysorbates' Inhibitory Effect on P-Glycoprotein

Much effort has been invested in the search for modulators of membrane transport proteins such as P-glycoprotein (P-gp) to improve drug bioavailability and reverse multidrug resistance in cancer. Nonionic surfactants, a class of pharmaceutical excipients, are known to inhibit such proteins, but knowledge about the exact mechanism of this inhibition is scarce. Here, we perform multiscale molecular dynamics simulations of one of these surfactants, polysorbate 20 (PS20), to reveal the behavior of such compounds on the molecular level and thereby discover the molecular mechanism of the P-gp inhibition. We show that the amphiphilic headgroup of PS20 is too hydrophobic to partition in the water phase, which drives the binding of PS20 to the amphiphilic drug-binding domain of P-gp and thereby causes the inhibition of the protein. Based on our findings, we conclude that PS20 primarily inhibits P-gp through direct binding to the drug-binding domain (DBD) from the extracellular leaflet.

Chemosensitizing effect and mechanism of imperatorin on the anti-tumor activity of doxorubicin in tumor cells and transplantation tumor model

Multidrug resistance of tumors has been a severe obstacle to the success of cancer chemotherapy. The study wants to investigate the reversal effects of imperatorin (IMP) on doxorubicin (DOX) resistance in K562/DOX leukemia cells, A2780/Taxol cells and in NOD/SCID mice, to explore the possible molecular mechanisms. K562/DOX and A2780/Taxol cells were treated with various concentrations of DOX and Taol with or without different concentrations of IMP, respectively. K562/DOX xenograft model was used to assess anti-tumor effect of IMP combined with DOX. MTT assay, Rhodamine 123 efflux assay, RT-PCR, and Western blot analysis were determined in vivo and in vitro. Results showed that IMP significantly enhanced the cytotoxicity of DOX and Taxol toward corresponding resistance cells. In vivo results illustrated both the tumor volume and tumor weight were significantly decreased after 2-week treatment with IMP combined with DOX compared to the DOX alone group. Western blotting and RT-PCR analyses indicated that IMP downregulated the expression of P-gp in K562/DOX xenograft tumors in NOD/SCID mice. We also evaluated glycolysis and glutamine metabolism in K562/DOX cells by measuring glucose consumption and lactate production. The results revealed that IMP could significantly reduce the glucose consumption and lactate production of K562/DOX cells. Furthermore, IMP could also remarkably repress the glutamine consumption, α-KG and ATP production of K562/DOX cells. Thus, IMP may sensitize K562/DOX cells to DOX and enhance the anti-tumor effect of DOX in K562/DOX xenograft tumors in NOD/SCID mice. IMP may be an adjuvant therapy to mitigate the multidrug resistance in leukemia chemotherapy.

Ionic co-aggregates (ICAs) based oral drug delivery: Solubilization and permeability improvement

Due to the overwhelming percentage of poorly water-soluble drugs, pharmaceutical industry is in urgent need of efficient approaches for solubilization and permeability improvement. Salts consisting of lipophilic fatty acid anions and hydrophilic choline cations are found to be surface active and able to form ionic co-aggregates (ICAs) in water. Choline oleate-based ICAs significantly enhance oral absorption of paclitaxel (PTX) as compared with cremophor EL-based micelles (MCs). Aggregation-caused quenching probes enable tracking of intact ICAs in in vivo transport and cellular interaction. Prolonged intestinal retention of ICAs than MCs implies stronger solubilizing capability in vivo. Ex vivo imaging of major organs and intestinal tracts suggests transepithelial transport of intact ICAs. Cellular studies support the enhanced absorption of PTX and transmembrane transport of intact ICAs. In conclusion, ICAs, consisting of lipophilic ions and hydrophilic counter-ions, are of great potential in delivery of poorly water-soluble drugs by enhancing solubility and permeability.

Overexpression of ABCB1 Associated With the Resistance to the KRAS-G12C Specific Inhibitor ARS-1620 in Cancer Cells

The KRAS-G12C inhibitor ARS-1620, is a novel specific covalent inhibitor of KRAS-G12C, possessing a strong targeting inhibitory effect on KRAS-G12C mutant tumors. Overexpression of ATP-binding cassette super-family B member 1 (ABCB1/P-gp) is one of the pivotal factors contributing to multidrug resistance (MDR), and its association with KRAS mutations has been extensively studied. However, the investigations about the connection between the inhibitors of mutant KRAS and the level of ABC transporters are still missing. In this study, we investigated the potential drug resistance mechanism of ARS-1620 associated with ABCB1. The desensitization effect of ARS-1620 was remarkably intensified in both drug-induced ABCB1-overexpressing cancer cells and ABCB1-transfected cells as confirmed by cell viability assay results. This desensitization of ARS-1620 could be completely reversed when co-treated with an ABCB1 reversal agent. In mechanism-based studies, [³H] -paclitaxel accumulation assay revealed that ARS-1620 could be competitively pumped out by ABCB1. Additionally, it was found that ARS-1620 remarkably stimulated ATPase activity of ABCB1, and the HPLC drug accumulation assay displayed that ARS-1620 was actively transported out of ABCB1-overexpressing cancer cells. ARS-1620 acquired a high docking score in computer molecular docking analysis, implying ARS-1620 could intensely interact with ABCB1 transporters. Taken all together, these data indicated that ARS-1620 is a substrate for ABCB1, and the potential influence of ARS-1620-related cancer therapy on ABCB1-overexpressing cancer cells should be considered in future clinical applications.

Predicting nanoemulsion formulation and studying the synergism mechanism between surfactant and cosurfactant: A combined computational and experimental approach

Nanoemulsion (NE) is a dosage form widely used in pharmaceutical, food, agrochemical, cosmetics, and personal care industries. NE systems are usually formulated through trial and error via numerous semi-empirical experiments. Moreover, the complex interaction mechanisms between the formulation surfactant and cosurfactant are difficult to understand. Dissipative particle dynamics (DPD) may be helpful in solving these formulation problems. Silibinin is a flavonolignan isolated from milk thistle, which has demonstrated antioxidant and antimicrobial effects. For this project, silibinin-loaded nanoemulsion (SBNE) was formulated by DPD, including surfactant and cosurfactant screening, pseudo-ternary phase construction, and SBNE characterization, all of which were verified by experimentation. Most importantly, this work shows that DPD can be adopted to explore the synergetic mechanisms between the surfactant and cosurfactant, including emulsification efficiency, distance, angle, arrangement, and order parameter. Additional verification experiments on the antioxidant and antimicrobial applications of simulation-designed SBNE were also carried out and confirmed DPD-predicted results. As such, predicting NE formulation by DPD has been proven to be feasible. For SBNE, the addition of PEG400 cosurfactant stretches the Cremophor RH40 surfactant molecules and assists in a more orderly arrangement. An enhanced interfacial thickness in SBNE could be attributed to the stretched hydrophilic head group and the decreased angle between the molecular axis and interface normal. These DPD and experimentally-verified results indicated that a proper cosurfactant will enhance the interfacial thickness, decrease the consumption of surfactant, and benefit NE formation. This new computationally applied knowledge should facilitate optimizing, designing, and understanding NE formulation more rationally and scientifically.

Non-ionic Surfactants as a P-Glycoprotein(P-gp) Efflux Inhibitor for Optimal Drug Delivery-A Concise Outlook

Significant research efforts have been devoted to unraveling the mystery of P-glycoprotein(P-gp) in drug delivery applications. The efflux membrane transporter P-gp is widely distributed in the body and accountable for restricting drug absorption and bioavailability. For these reasons, it is the primary cause of developing multidrug resistance (MDR) in most drug delivery applications. Therefore, P-gp inhibitors must be explored to address MDR and the low bioavailability of therapeutic substrates. Several experimental models in kinetics and dynamic studies identified the sensitivity of drug molecules and excipients as a P-gp inhibitor. In this review, we aimed to emphasize nonionic surface-active agents for effective reversal of P-gp inhibition. As it is inert, non-toxic, noncharged, and quickly reaching the cytosolic lipid membrane (the point of contact with P-gp efflux protein) enables it to be more efficient as P-gp inhibitors. Moreover, nonionic surfactant improves drug absorption and bioavailability through the various mechanism, involving (i) association of drug with surfactant improves solubilization, facilitating its cell penetration and absorption; (ii) weakening the lateral membrane packing density, facilitating the passive drug influx; and (iii) inhibition of the ATP binding cassette of transporter P-glycoprotein. The application of nonionic surfactant as P-gp inhibitors is well established and supported by various experiments. Altogether, herein, we have primarily focused on various nonionic surfactants and their development strategies to conquer the MDR-causing effects of P-gp efflux protein in drug delivery. Graphical Abstract.

Polysorbate-Based Drug Formulations for Brain-Targeted Drug Delivery and Anticancer Therapy

Polysorbates (PSs) are synthetic nonionic surfactants consisting of polyethoxy sorbitan fatty acid esters. PSs have been widely employed as emulsifiers and stabilizers in various drug formulations and food additives. Recently, various PS-based formulations have been developed for safe and efficient drug delivery. This review introduces the general features of PSs and PS-based drug carriers, summarizes recent progress in the development of PS-based drug formulations, and discusses the physicochemical properties, biological safety, P-glycoprotein inhibitory properties, and therapeutic applications of PS-based drug formulations. Additionally, recent advances in brain-targeted drug delivery using PS-based drug formulations have been highlighted. This review will help researchers understand the potential of PSs as effective drug formulation agents.

An Assessment of Occasional Bio-Inequivalence for BCS1 and BCS3 Drugs: What are the Underlying Reasons?

Despite having adequate solubility properties, bioequivalence (BE) studies performed on immediate release formulations containing BCS1/3 drugs occasionally fail. By systematically evaluating a set of 17 soluble drugs where unexpected BE failures have been reported and comparing to a set of 29 drugs where no such reports have been documented, a broad assessment of the risk factors leading to BE failure was performed. BE failures for BCS1/3 drugs were predominantly related to changes in C_max rather than AUC. C_max changes were typically modest, with minimal clinical significance for most drugs. Overall, drugs with a sharp plasma peak were identified as a key factor in BE failure risk. A new pharmacokinetic term (t½C_max) is proposed to identify drugs at higher risk due to their peak plasma profile shape. In addition, the analysis revealed that weak acids, and drugs with particularly high gastric solubility are potentially more vulnerable to BE failure, particularly when these features are combined with a sharp C_max peak. BCS3 drugs, which are often characterised as being more vulnerable to BE failure due to their potential for permeation and transit to be altered, particularly by excipient change, were not in general at greater risk of BE failures. These findings will help to inform how biowaivers may be optimally applied in the future.

Nanoplatform-based natural products co-delivery system to surmount cancer multidrug-resistant

The emergence of multidrug resistance (MDR) in malignant tumors is the primary reason for invalid chemotherapy. Antitumor drugs are often adversely affected by the MDR of tumor cells. Treatments using conventional drugs, which have specific drug targets, hardly regulate the complex signaling pathway of MDR cells because of the complex formation mechanism of MDR. However, natural products have positive advantages, such as high efficiency, low toxicity, and ability to target multiple mechanism pathways associated with MDR. Natural products, as MDR reversal agents, synergize with chemotherapeutics and enhance the sensitivity of tumor cells to chemotherapeutics, and the co-delivery of natural products and antitumor drugs with nanocarriers maximizes the synergistic effects against MDR in tumor cells. This review summarizes the molecular mechanisms of MDR, the advantages of natural products combined with chemotherapeutics in offsetting complicated MDR mechanisms, and the types and mechanisms of natural products that are potential MDR reversal modulators. Meanwhile, aiming at the low bioavailability of cocktail combined natural products and chemotherapeutic in vivo, the advantages of nanoplatform-based co-delivery system and recent research developments are illustrated on the basis of our previous research. Finally, prospective horizons are analyzed, which are expected to considerably improve the nano-co-delivery of natural products and chemotherapeutic systems for MDR reversal in cancer.

Changes of Transporters and Drug-metabolizing Enzymes in Nephrotic Syndrome

BACKGROUND

Drug-metabolizing enzymes and transporters play key roles in drug disposition and drug interactions. The alterations of their expression will influence drug pharmacokinetics and pharmacodynamics. However, the changes in the expression of enzymes and transporters in the disease state are still unclear.

OBJECTIVE

Our study was to investigate the changes in the expression of main enzymes and drug transporters distributed in Adriamycin nephropathy rat liver, kidney, and intestine.

METHODS

An intravenous injection with a single dose of Adriamycin (6mg/kg) was made to establish Adriamycin nephropathy (AN) model and normal groups were injected with normal saline. Serum was collected for lipid metabolism, renal, and hepatic function measurement. The real-time PCR and western blot were applied to determine the mRNA and protein expression of drug enzymes and transporters.

RESULTS

In the kidney, a greater expression of Mdr1, Mrp2, Mrp4 Oat2 and Oct2 mRNA was found in AN rats as compared with control rats. In the liver, the expression of Bcrp mRNA was more doubled or tripled than control groups and downregulation of Mdr1, Mrp2, Mrp4 and Bsep gene expression was found in AN rats. Besides, we observed a downward trend of Cyp1a2, Cyp3a4 and Cyp2c9 mRNA levels in AN groups. In the duodenum, the expression of Mdr1 and Mrp3 mRNA level was decreased, while Bcrp and Mrp2 mRNA were increased.

CONCLUSION

The changes in drug-metabolizing enzymes and transporters expression in AN rats were clarified, which may be beneficial for understanding the altered pharmacokinetics and pharmacodynamics of clinical drugs and reduce unexpected clinical findings for nephropathy patients.

Effect of Pharmaceutical Excipients on Intestinal Absorption of Metformin via Organic Cation-Selective Transporters

Growing evidence has shown that some pharmaceutical excipients can act on drug transporters. The present study was aimed at investigating the effects of 13 commonly used excipients on the intestinal absorption of metformin (MTF) and the underlying mechanisms using Caco-2 cells and an ex vivo mouse non-everted gut sac model. First, the uptake of MTF in Caco-2 cells was markedly inhibited by nonionic excipients including Solutol HS 15, polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 80, and crospovidone. Second, transport profile studies showed that MTF was taken up via multiple cation-selective transporters, among which a novel pyrilamine-sensitive proton-coupled organic cation (H⁺/OC⁺) antiporter played a key role. Third, Solutol HS 15, polysorbate 40, and polysorbate 60 showed cis-inhibitory effects on the uptake of either pyrilamine (prototypical substrate of the pyrilamine-sensitive H⁺/OC⁺ antiporter) or 1-methyl-4-phenylpyridinium (substrate of traditional cation-selective transporters including OCTs, MATEs, PMAT, SERT, and THTR-2), indicating that their suppression on MTF uptake is due to the synergistic inhibition toward multiple influx transporters. Finally, the pH-dependent mouse intestinal absorption of MTF was significantly decreased by Solutol HS 15, polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 80, and pyrilamine. In conclusion, this study revealed that a novel transport process mediated by the pyrilamine-sensitive H⁺/OC⁺ antiporter contributes to the intestinal absorption of MTF in conjunction with the traditional cation-selective transporters. Mechanistic understanding of the interaction of excipients with cation-selective transporters can improve the formulation design and clinical application of cationic drugs.

Dual Inhibition of P-gp and BCRP Improves Oral Topotecan Bioavailability in Rodents

P-glycoprotein (P-gp) inhibition has been studied to overcome multidrug resistance in cancer chemotherapy but failed in clinical trials due to low/toxic effects. Recently, a dual modulation of transporters and natural derivatives have been examined to surmount this limitation. We examined breast cancer resistance protein (BCRP) inhibition in vitro and in vivo by P-gp inhibitors derived from natural compounds in previous studies. P-gp inhibitors increased the accumulation of the anticancer drug, topotecan (TPT)-a substrate of P-gp and BCRP, albeit with higher affinity for BCRP-in BCRP-overexpressing cells, resulting in cell death. These dual inhibitors, when orally co-administered with TPT, enhanced TPT bioavailability with slightly reduced total oral clearance (Clt/F) in rats. In xenograft mice, they strengthened oral TPT-induced tumor reduction with no alterations in body weight. Moreover, we investigated the effects of an oral drug formulation (Cremophor® EL, Tween® 80, and polyethylene glycol 400) on the transporters function. The excipients increased TPT accumulation in P-gp- or BCRP-overexpressing cells. Oral TPT bioavailability was higher with the formulation than with a control, as shown by the increases in the maximum plasma concentration (Cmax) and the area under the plasma concentration-time curve from zero to infinity (AUCINF) (p< 0.01). Therefore, oral TPT bioavailability was enhanced by P-gp/BCRP dual inhibition, which resulted in a formulation-mediated increase in absorption and decrease in elimination, and a dual inhibitor-mediated decrease in elimination. These results suggest that the combination of dual inhibition by a natural derivative and the drug formulation can be a useful clinical approach.

Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Metformin Hydrochloride

Data are examined regarding possible waiver of in vivo bioequivalence testing (i.e. biowaiver) for approval of metformin hydrochloride (metformin) immediate-release solid oral dosage forms. Data include metformin's Biopharmaceutics Classification System (BCS) properties, including potential excipient interactions. Metformin is a prototypical transporter-mediated drug and is highly soluble, but only 50% of an orally administered dose is absorbed from the gut. Therefore, metformin is a BCS Class III substance. A BCS-based approval approach for major changes to marketed products and new generics is admissible if test and reference dosage forms have the identical active pharmaceutical ingredient and if in vitro dissolution from both are very rapid (i.e. at least 85% within 15 min at pH 1.2, 4.5, and 6.8). Recent International Council for Harmonisation BCS guidance indicates all excipients for Class III biowaivers are recommended to be qualitatively the same and quantitatively similar (except for preservatives, flavor agents, colorant, or capsule shell or film coating excipients). However, despite metformin being a prototypical transporter-mediated drug, there is no evidence that commonly used excipients impact metformin absorption, such that this restriction on excipients for BCS III drugs merits regulatory relief. Commonly used excipients in usual amounts are not likely to impact metformin absorption.

Physiologically Based Pharmacokinetic/Pharmacodynamic Modeling to Support Waivers of In Vivo Clinical Studies: Current Status, Challenges, and Opportunities

Physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) modeling has been extensively applied to quantitatively translate in vitro data, predict the in vivo performance, and ultimately support waivers of in vivo clinical studies. In the area of biopharmaceutics and within the context of model-informed drug discovery and development (MID3), there is a rapidly growing interest in applying verified and validated mechanistic PBPK models to waive in vivo clinical studies. However, the regulatory acceptance of PBPK analyses for biopharmaceutics and oral drug absorption applications, which is also referred to variously as "PBPK absorption modeling" [Zhang et al. CPT: Pharmacometrics Syst. Pharmacol. 2017, 6, 492], "physiologically based absorption modeling", or "physiologically based biopharmaceutics modeling" (PBBM), remains rather low [Kesisoglou et al. J. Pharm. Sci. 2016, 105, 2723] [Heimbach et al. AAPS J. 2019, 21, 29]. Despite considerable progress in the understanding of gastrointestinal (GI) physiology, in vitro biopharmaceutic and in silico tools, PBPK models for oral absorption often suffer from an incomplete understanding of the physiology, overparameterization, and insufficient model validation and/or platform verification, all of which can represent limitations to their translatability and predictive performance. The complex interactions of drug substances and (bioenabling) formulations with the highly dynamic and heterogeneous environment of the GI tract in different age, ethnic, and genetic groups as well as disease states have not been yet fully elucidated, and they deserve further research. Along with advancements in the understanding of GI physiology and refinement of current or development of fully mechanistic in silico tools, we strongly believe that harmonization, interdisciplinary interaction, and enhancement of the translational link between in vitro, in silico, and in vivo will determine the future of PBBM. This Perspective provides an overview of the current status of PBBM, reflects on challenges and knowledge gaps, and discusses future opportunities around PBPK/PD models for oral absorption of small and large molecules to waive in vivo clinical studies.

The advantages of nanomedicine in the treatment of visceral leishmaniasis: between sound arguments and wishful thinking

Introduction: Although life-threatening if left untreated, visceral leishmaniasis (VL) is still a neglected endemic disease in 98 countries worldwide. The number of drugs available is low and few are in clinical trials. In the last decades, efforts have been made on the development of nanocarriers as drug delivery systems to treat VL. Given the preferential intracellular location of the parasite in the liver and spleen macrophages, the rationale is sturdy. In a clinical setting, liposomal amphotericin B displays astonishing cure rates.Areas covered: A literature search was performed through PubMed and Google Scholar. We critically reviewed the main literature highlighting the success of nanomedicine in VL. We also reviewed the hurdles and yet unfulfilled promises rising awareness of potential drawbacks of nanomedicine in VL.Expert opinion: VL is a disease where nanomedicines successes shine through. However, there are a lot of obstacles on the road to developing more efficient strategies such as targeting functionalization, oral formulations, or combined therapies. And those strategies raise many questions.

Food Additives as Inhibitors of Intestinal Drug Transporter OATP2B1

Food additives are compounds that are added to food and beverage to improve the taste, color, preservation, or composition. Generally, food additives are considered safe for human use due to safety evaluations conducted by food safety authorities and high safety margins applied to permitted usage levels. However, the interaction potential of food additives with simultaneously administered medication has not received much attention. Even though many food additives are poorly absorbed into systemic circulation, high concentrations could exist in the intestinal lumen, making intestinal drug transporters, such as the uptake transporter organic anion transporting polypeptide 2B1 (OATP2B1), a possible site of food additive-drug interactions. In the present work, we aimed to characterize the interaction of a selection of 25 food additives including colorants, preservatives, and sweeteners with OATP2B1 in vitro. In human embryonic kidney 293 (HEK293) cells transiently overexpressing OATP2B1 or control, uptake of dibromofluorescein was studied with and without 50 μM food additive at pH 7.4. As OATP2B1 displays substrate- and pH-dependent transport functions and the intraluminal pH varies along the gastrointestinal tract, we performed the studies also at pH 5.5 using estrone sulfate as an OATP2B1 substrate. Food additives that inhibited OATP2B1-mediated substrate transport by ≥50% were subjected to dose-response studies. Six colorants were identified and validated as OATP2B1 inhibitors at pH 5.5, but only three of these were categorized as inhibitors at pH 7.4. One sweetener was validated as an inhibitor under both assay conditions, whereas none of the preservatives exhibited ≥50% inhibition of OATP2B1-mediated transport. Extrapolation of computed inhibitory constants (K_i values) to estimations of intestinal food additive concentrations implies that selected colorants could inhibit intestinal OATP2B1 also in vivo. These results suggest that food additives, especially colorants, could alter the pharmacokinetics of orally administered OATP2B1 substrate drugs, although further in vivo studies are warranted to understand the overall clinical consequences of the findings.

Exploring the Impact of Surfactant Type and Digestion: Highly Digestible Surfactants Improve Oral Bioavailability of Nilotinib

The scientific rationale for selection of the surfactant type during oral formulation development requires an in-depth understanding of the interplay between surfactant characteristics and biopharmaceutical factors. Currently, however, there is a lack of comprehensive knowledge of how surfactant properties, such as hydrophilic-lipophilic balance (HLB), digestibility, and fatty acid (FA) chain length, translate into in vivo performance. In the present study, the relationship between surfactant properties, in vitro characteristics, and in vivo bioavailability was systematically evaluated. An in vitro lipolysis model was used to study the digestibility of a variety of nonionic surfactants. Eight surfactants and one surfactant mixture were selected for further analysis using the model poorly water-soluble drug nilotinib. In vitro lipolysis of all nilotinib formulations was performed, followed by an in vivo pharmacokinetic evaluation in rats. The in vitro lipolysis studies showed that medium-chain FA-based surfactants were more readily digested compared to long-chain surfactants. The in vivo study demonstrated that a Tween 20 formulation significantly enhanced the absolute bioavailability of nilotinib up to 5.2-fold relative to an aqueous suspension. In general, surfactants that were highly digestible in vitro tended to display higher bioavailability of nilotinib in vivo. The bioavailability may additionally be related to the FA chain length of digestible surfactants with an improved exposure in the case of medium-chain FA-based surfactants. There was no apparent relationship between the HLB value of surfactants and the in vivo bioavailability of nilotinib. The impact of this study's findings suggests that when designing surfactant-based formulations to enhance oral bioavailability of the poorly water-soluble drug nilotinib, highly digestible, medium chain-based surfactants are preferred. Additionally, for low-permeability drugs such as nilotinib, which is subject to efflux by intestinal P-glycoprotein, the biopharmaceutical effects of surfactants merit further consideration.

Overexpression of ABCB1 Transporter Confers Resistance to mTOR Inhibitor WYE-354 in Cancer Cells

The overexpressing ABCB1 transporter is one of the key factors leading to multidrug resistance (MDR). Thus, many ABCB1 inhibitors have been found to be able to overcome ABCB1-mediated MDR. However, some inhibitors also work as a substrate of ABCB1, which indicates that in order to achieve an effective reversal dosage, a higher concentration is needed to overcome the pumped function of ABCB1, which may concurrently increase the toxicity. WYE-354 is an effective and specific mTOR (mammalian target of rapamycin) inhibitor, which recently has been reported to reverse ABCB1-mediated MDR. In the current study, 3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay was carried out to determine the cell viability and reversal effect of WYE-354 in parental and drug-resistant cells. Drug accumulation was performed to examine the effect of WYE-354 on the cellular accumulation of chemotherapeutic drugs. The ATPase (adenosine triphosphatase) activity of the ABCB1 transporter in the presence or absence of WYE-354 was conducted in order to determine the impact of WYE-354 on ATP hydrolysis. Western blot analysis and immunofluorescence assay were used to investigate the protein molecules related to MDR. In addition, the interaction between the WYE-354 and ABCB1 transporter was investigated via in silico analysis. We demonstrated that WYE-354 is a substrate of ABCB1, that the overexpression of the ABCB1 transporter decreases the efficacy of WYE-354, and that the resistant WYE-354 can be reversed by an ABCB1 inhibitor at a pharmacological achievable concentration. Furthermore, WYE-354 increased the intracellular accumulation of paclitaxel in the ABCB1-mediated MDR cell line, without affecting the corresponding parental cell line, which indicated that WYE-354 could compete with other chemotherapeutic drugs for the ABCB1 transporter substrate binding site. In addition, WYE-354 received a high score in the docking analysis, indicating a strong interaction between WYE-354 and the ABCB1 transporter. The results of the ATPase analysis showed that WYE-354 could stimulate ABCB1 ATPase activity. Treatment with WYE-354 did not affect the protein expression or subcellular localization of the ABCB1. This study provides evidence that WYE-354 is a substrate of the ABCB1 transporter, implicating that WYE-354 should be avoided for use in ABCB1-mediated MDR cancer.

Synthesis of Tilmicosin Nanostructured Lipid Carriers for Improved Oral Delivery in Broilers: Physiochemical Characterization and Cellular Permeation

This study aimed to develop nanostructured lipid carriers (NLCs) for improved oral absorption of tilmicosin (TMS) in broilers. Thus, palmitic acid, lauric acid, and stearic acid were selected as solid lipids to formulate TMS-pNLCs, TMS-lNLCs, and TMS-sNLCs, respectively. They showed similar physicochemical properties and meanwhile possessed excellent storage and gastrointestinal stability. The TMS interacted with the lipid matrix and was encapsulated efficiently in NLCs in an amorphous structure. NLCs could enhance oral absorption of TMS compared to 10% tilmicosin phosphate solution in broilers, among which the TMS-sNLCs were the most efficient drug delivery carriers, with a relative oral bioavailability of 203.55%. NLCs could inhibit the efflux of P-glycoprotein (P-pg) toward TMS, which may be involved with improved oral absorption. Taken together, these types of solid lipids influenced the enhanced level of NLCs toward oral bioavailability of TMS, and the sNLCs proved to be the most promising oral delivery carriers of TMS.

Paclitaxel-loaded sodium deoxycholate-stabilized zein nanoparticles: characterization and in vitro cytotoxicity

Paclitaxel (PTX) is one of the most successful antineoplastic drugs and is widely used for the treatment of many forms of advanced and refractory cancer. Unfortunately, various drawbacks including non-selective cytotoxicity, poor water solubility and low bioavailability limit its clinical use. The aim of this study was to characterize a novel colloidal system made up of the natural protein zein, that would be able to efficiently retain the anticancer compound and increase its in vitro pharmacological effects. In fact, zein has promising characteristics that render it a potential material to be used in drug delivery application. The influences of temperature, pH and serum incubation on the stability of these particles, entrapment efficiency of PTX and in vitro toxicity on different cancer cell lines were evaluated. The nanosystems containing PTX demonstrated suitable storage stability, and were not destabilized by temperatures of up to 50 °C, pH alterations, the freeze-drying process or serum proteins. The encapsulation of PTX did not destabilize the structure of the zein nanoparticles and a suitable drug entrapment efficiency resulted. PTX-loaded zein nanoparticles showed an increased toxicity on different cancer cell lines with respect to the free drug, confirming its potential application in preclinical and clinical investigations.