Animal versus human oral drug bioavailability: do they correlate?

Tissue-Engineered Three-Dimensional Platforms for Disease Modeling and Therapeutic Development

Three-dimensional (3D) tissue-engineered models are under investigation to recapitulate tissue architecture and functionality, thereby overcoming limitations of traditional two-dimensional cultures and preclinical animal models. This review highlights recent developments in 3D platforms designed to model diseases in vitro that affect numerous tissues and organs, including cardiovascular, gastrointestinal, bone marrow, neural, reproductive, and pulmonary systems. We discuss current technologies for engineered tissue models, highlighting the advantages, limitations, and important considerations for modeling tissues and diseases. Lastly, we discuss future advancements necessary to enhance the reliability of 3D models of tissue development and disease.

Short Caco-2 model for evaluation of drug permeability: A sodium valerate-assisted approach

The human colorectal adenocarcinoma cell line Caco-2, widely used for studying intestinal drug permeability, is typically grown on permeable filter supports and matures in 21 days with frequent media changes. The process is labor-intensive, prone to contamination, and has low throughput, contributing to the overall high utilization cost. Efforts to establish a low-cost, high-throughput, and short-duration model have encountered obstacles, such as weaker tight junctions causing monolayer leaks, incomplete differentiation resulting in low transporter expression, intricate and challenging protocols, and cytotoxicity, limiting the usability. Hence, this study aimed to develop a low-cost, efficient, and short-duration model by addressing the aforementioned concerns by customizing the media and finding a safe differentiation inducer. We generated a new rapid model using sodium valerate, which demonstrated sufficient transporter activity, improved monolayer integrity, and higher levels of differentiation markers than the 21-day model. Furthermore, this model exhibited consistent and reliable results when used to evaluate drug permeability over multiple days of repeated use. This study demonstrates the potential of a sodium valerate-assisted abbreviated model for drug permeability assessment with economic and practical advantages.

Liver-on-chips for drug discovery and development

Recent FDA modernization act 2.0 has led to increasing industrial R&D investment in advanced in vitro 3D models such as organoids, spheroids, organ-on-chips, 3D bioprinting, and in silico approaches. Liver-related advanced in vitro models remain the prime area of interest, as liver plays a central role in drug clearance of compounds. Growing evidence indicates the importance of recapitulating the overall liver microenvironment to enhance hepatocyte maturity and culture longevity using liver-on-chips (LoC) in vitro. Hence, pharmaceutical industries have started exploring LoC assays in the two of the most challenging areas: accurate in vitro-in vivo extrapolation (IVIVE) of hepatic drug clearance and drug-induced liver injury. We examine the joint efforts of commercial chip manufacturers and pharmaceutical companies to present an up-to-date overview of the adoption of LoC technology in the drug discovery. Further, several roadblocks are identified to the rapid adoption of LoC assays in the current drug development framework. Finally, we discuss some of the underexplored application areas of LoC models, where conventional 2D hepatic models are deemed unsuitable. These include clearance prediction of metabolically stable compounds, immune-mediated drug-induced liver injury (DILI) predictions, bioavailability prediction with gut-liver systems, hepatic clearance prediction of drugs given during pregnancy, and dose adjustment studies in disease conditions. We conclude the review by discussing the importance of PBPK modeling with LoC, digital twins, and AI/ML integration with LoC.

Prediction of the First-Pass Metabolism of a Drug After Oral Intake Based on Structural Parameters and Physicochemical Properties

BACKGROUND AND OBJECTIVE

The oral first-pass metabolism is a crucial factor that plays a key role in a drug's pharmacokinetic profile. Prediction of the oral first-pass metabolism based on chemical structural parameters can be useful in the drug-design process. Developing an orally administered drug with an acceptable pharmacokinetic profile is necessary to reduce the cost and time associated with evaluating the extent of the first-pass metabolism of a candidate compound in preclinical studies. The aim of this study is to estimate the first-pass metabolism of an orally administered drug.

METHODS

A set of compounds with reported first-pass metabolism data were collected. Moreover, human intestinal absorption percentage and oral bioavailability data were extracted from the literature to propose a classification system that split the drugs up based on their first-pass metabolism extents. Various structural parameters were calculated for each compound. The relations of the structural and physicochemical values of each compound to the class the compound belongs to were obtained using logistic regression.

RESULTS

Initial analysis showed that compounds with logD7.4 > 1 or a rugosity factor of > 1.5 are more likely to have high first-pass metabolism. Four different models that can predict the oral first-pass metabolism with acceptable error were introduced. The overall accuracies of the models were in the range of 72% (for models with simple descriptors) to 78% (for models with complex descriptors). Although the models with simple descriptors have lower accuracies compared to complex models, they are more interpretable and easier for researchers to utilize.

CONCLUSION

A novel classification of drugs based on the extent of the oral first-pass metabolism was introduced, and mechanistic models were developed to assign candidate compounds to the appropriate proposed classes.

Trust your gut: Establishing confidence in gastrointestinal models - An overview of the state of the science and contexts of use

The webinar series and workshop titled “Trust Your Gut: Establishing Confidence in Gastrointestinal Models – An Overview of the State of the Science and Contexts of Use” was co-organized by NICEATM, NIEHS, FDA, EPA, CPSC, DoD, and the Johns Hopkins Center for Alternatives to Animal Testing (CAAT) and hosted at the National Institutes of Health in Bethesda, MD, USA on October 11-12, 2023. New approach methods (NAMs) for assessing issues of gastrointestinal tract (GIT)- related toxicity offer promise in addressing some of the limitations associated with animal-based assessments. GIT NAMs vary in complexity, from two-dimensional monolayer cell line-based systems to sophisticated 3-dimensional organoid systems derived from human primary cells. Despite advances in GIT NAMs, challenges remain in fully replicating the complex interactions and pro­cesses occurring within the human GIT. Presentations and discussions addressed regulatory needs, challenges, and innovations in incorporating NAMs into risk assessment frameworks; explored the state of the science in using NAMs for evaluating systemic toxicity, understanding absorption and pharmacokinetics, evaluating GIT toxicity, and assessing potential allergenicity; and discussed strengths, limitations, and data gaps of GIT NAMs as well as steps needed to establish confidence in these models for use in the regulatory setting.

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.

Evaluating physiochemical properties of FDA-approved orally administered drugs

INTRODUCTION

Analyses of orally administered FDA-approved drugs from 1990 to 1993 enabled the identification of a set of physiochemical properties known as Lipinski's Rule of Five (Ro5). The original Ro5 and extended versions still remain the reference criteria for drug development programs. Since many bioactive compounds do not conform to the Ro5, we validated the relevance of and adherence to these rulesets in a contemporary cohort of FDA-approved drugs.

AREAS COVERED

The authors noted that a significant proportion of FDA-approved orally administered parent compounds from 2011 to 2022 deviate from the original Ro5 criteria (~38%) or the Ro5 with extensions (~53%). They then evaluated if a contemporary Ro5 criteria (cRo5) could be devised to better predict oral bioavailability. Furthermore, they discuss many case studies showcasing the need for and benefit of increasing the size of certain compounds and cover several evolving strategies for improving oral bioavailability.

EXPERT OPINION

Despite many revisions to the Ro5, the authors find that no single proposed physiochemical rule has universal concordance with absolute oral bioavailability. Innovations in drug delivery and formulation have dramatically expanded the range of physicochemical properties and the chemical diversity for oral administration.

Overcoming Barriers Associated with Oral Delivery of Differently Sized Fluorescent Core-Shell Silica Nanoparticles

Oral delivery, while a highly desirable form of nanoparticle-drug administration, is limited by challenges associated with overcoming several biological barriers. Here, the authors study how fluorescent and poly(ethylene glycol)-coated (PEGylated) core-shell silica nanoparticles sized 5 to 50 nm interact with major barriers including intestinal mucus, intestinal epithelium, and stomach acid. From imaging fluorescence correlation spectroscopy studies using quasi-total internal reflection fluorescence microscopy, diffusion of nanoparticles through highly scattering mucus is progressively hindered above a critical hydrodynamic size around 20 nm. By studying Caco-2 cell monolayers mimicking the intestinal epithelia, it is observed that ultrasmall nanoparticles below 10 nm diameter (Cornell prime dots, [C' dots]) show permeabilities correlated with high absorption in humans from primarily enhanced passive passage through tight junctions. Particles above 20 nm diameter exclusively show active transport through cells. After establishing C' dot stability in artificial gastric juice, in vivo oral gavage experiments in mice demonstrate successful passage through the body followed by renal clearance without protein corona formation. Results suggest C' dots as viable candidates for oral administration to patients with a proven pathway towards clinical translation and may generate renewed interest in examining silica as a food additive and its effects on nutrition and health.

Contribution of the Dynamic Intestinal Absorption Model (Diamod) to the Development of a Patient-Centric Drug Formulation

Compound X is a weak basic drug targeting the early stages of Parkinson's disease, for which a theoretical risk assessment has indicated that elevated gastric pH conditions could potentially result in reduced plasma concentrations. Different in vitro dissolution methodologies varying in level of complexity and a physiologically based pharmacokinetic (PBPK) absorption model demonstrated that the dissolution, solubility, and intestinal absorption of compound X was indeed reduced under elevated gastric pH conditions. These observations were confirmed in a crossover pharmacokinetic study in Beagle dogs. As a result, the development of a formulation resulting in robust performance that is not sensitive to the exposed gastric pH levels is of crucial importance. The dynamic intestinal absorption MODel (Diamod), an advanced in vitro gastrointestinal transfer tool that allows to study the gastrointestinal dissolution and interconnected permeation of drugs, was selected as an in vitro tool for the formulation optimization activities given its promising predictive capacity and its capability to generate insights into the mechanisms driving formulation performance. Different pH-modifiers were screened for their potential to mitigate the pH-effect by decreasing the microenvironmental pH at the dissolution surface. Finally, an optimized formulation containing a clinically relevant dose of the drug and a functional amount of the selected pH-modifier was evaluated for its performance in the Diamod. This monolayer tablet formulation resulted in rapid gastric dissolution and supersaturation, inducing adequate intestinal supersaturation and permeation of compound X, irrespective of the gastric acidity level in the stomach. In conclusion, this study describes the holistic biopharmaceutics approach driving the development of a patient-centric formulation of compound X.

Advancing algorithmic drug product development: Recommendations for machine learning approaches in drug formulation

Artificial intelligence is a rapidly expanding area of research, with the disruptive potential to transform traditional approaches in the pharmaceutical industry, from drug discovery and development to clinical practice. Machine learning, a subfield of artificial intelligence, has fundamentally transformed in silico modelling and has the capacity to streamline clinical translation. This paper reviews data-driven modelling methodologies with a focus on drug formulation development. Despite recent advances, there is limited modelling guidance specific to drug product development and a trend towards suboptimal modelling practices, resulting in models that may not give reliable predictions in practice. There is an overwhelming focus on benchtop experimental outcomes obtained for a specific modelling aim, leaving the capabilities of data scraping or the use of combined modelling approaches yet to be fully explored. Moreover, the preference for high accuracy can lead to a reliance on black box methods over interpretable models. This further limits the widespread adoption of machine learning as black boxes yield models that cannot be easily understood for the purposes of enhancing product performance. In this review, recommendations for conducting machine learning research for drug product development to ensure trustworthiness, transparency, and reliability of the models produced are presented. Finally, possible future directions on how research in this area might develop are discussed to aim for models that provide useful and robust guidance to formulators.

Evaluating the bioequivalence of levetiracetam brand and generic oral tablets available in the Saudi market in vivo

Background

Epilepsy is a common global neurological disorder. About 30% of epileptic patients are managed with anti-epileptic Drugs (AEDs). Since 2000, Levetiracetam (LEV) has been marketed around the world as an AED under the brand name Keppra, and recently more generics are found in the Saudi market as cheaper alternatives. The objective of this study is to evaluate the bioequivalence of LEV brand and generics available in the Saudi market in mice.

Methods

Pharmacokinetics (PK), liver function test, and behavioral studies were conducted for LEV brand and generic in different groups of Blab/c mice.

Results

PK results show a significance difference in PK parameters mostly evidenced with generic 3, then generic 2. The only significant different between Keppra and generic 1 was in T1/2. In addition, Keppra did not significantly increase liver enzymes in comparison to other generics. On the other hand, other generics showed less favorable results in increasing liver enzymes. Keppra reduced the number and intensity of epileptic attacks, had no mortality rate due to epilepsy, and was associated with less sever seizures attacks.

Conclusion

Keppra, the brand form of LEV, has better safety and efficacy profiles in mice compared to 3 generics found in the Saudi market. Therefore, we recommend evaluating the same parameters tested in this study in patients utilizing similar generics and brand to establish the existence of bioequivalence between LEV brand and generics.

Methodical advances in reproducibility research: A proof of concept qualitative comparative analysis of reproducing animal data in humans

BACKGROUND

While the term reproducibility crisis mainly reflects reproducibility of experiments between laboratories, reproducibility between species also remains problematic. We previously summarised the published reproducibility between animal and human studies; i.e. the translational success rates, which varied from 0% to 100%. Based on analyses of individual factors, we could not predict reproducibility. Several potential analyses can assess effect of combinations of predictors on an outcome. Regression analysis (RGA) is common, but not ideal to analyse multiple interactions and specific configurations (≈ combinations) of variables, which could be highly relevant to reproducibility. Qualitative comparative analysis (QCA) is based on set theory and Boolean algebra, and was successfully used in other fields. We reanalysed the data from our preceding review with QCA.

RESULTS

This QCA resulted in the following preliminary formula for successful translation: ∼Old*∼Intervention*∼Large*MultSpec*Quantitative Which means that within the analysed dataset, the combination of relative recency (∼ means not; >1999), analyses at event or study level (not at intervention level), n < 75, inclusion of more than one species and quantitative (instead of binary) analyses always resulted in successful translation (>85%). Other combinations of factors showed less consistent or negative results. An RGA on the same data did not identify any of the included variables as significant contributors.

CONCLUSIONS

While these data were not collected with the QCA in mind, they illustrate that the approach is viable and relevant for this research field. The QCA seems a highly promising approach to furthering our knowledge on between-species reproducibility.

Quantitative Prediction of Intestinal Absorption of Drugs from In Vitro Study: Utilization of Differentiated Intestinal Epithelial Cells Derived from Intestinal Stem Cells at Crypts

Prediction of intestinal absorption of drugs in humans is one of the critical elements in the development process for oral drugs. However, it remains challenging, because intestinal absorption of drugs is influenced by multiple factors, including the function of various metabolic enzymes and transporters, and large species differences in drug bioavailability hinder the prediction of human bioavailability directly from in vivo animal experiments. For the screening of intestinal absorption properties of drugs, a transcellular transport assay with Caco-2 cells is still routinely used by pharmaceutical companies because of its convenience, but the predictability of the fraction of the oral dose that goes to the portal vein of metabolic enzyme/transporter substrate drugs was not always good because the cellular expression of metabolic enzymes and transporters is different from that in the human intestine. Recently, various novel in vitro experimental systems have been proposed such as the use of human-derived intestinal samples, transcellular transport assay with induced pluripotent stem-derived enterocyte-like cells, or differentiated intestinal epithelial cells derived from intestinal stem cells at crypts. Crypt-derived differentiated epithelial cells have an excellent potential to characterize species differences and regional differences in intestinal absorption of drugs because a unified protocol can be used for the proliferation of intestinal stem cells and their differentiation into intestinal absorptive epithelial cells regardless of the animal species and the gene expression pattern of differentiated cells is maintained at the site of original crypts. The advantages and disadvantages of novel in vitro experimental systems for characterizing intestinal absorption of drugs are also discussed. SIGNIFICANCE STATEMENT: Among novel in vitro tools for the prediction of human intestinal absorption of drugs, crypt-derived differentiated epithelial cells have many advantages. Cultured intestinal stem cells are rapidly proliferated and easily differentiated into intestinal absorptive epithelial cells simply by changing the culture media. A unified protocol can be used for the establishment of intestinal stem cell culture from preclinical species and humans. Region-specific gene expression at the collection site of crypts can be reproduced in differentiated cells.

Underestimation of glyphosate intake by the methods currently used by regulatory agencies

The acceptable daily intake (ADI) is an estimate of the amount of a substance in food or beverages that can be consumed daily over a lifetime without presenting an appreciable risk to health. To assess the risk of ingesting glyphosate, regulatory agencies compare glyphosate daily intake to ADI. Based on published data on urine glyphosate levels measured according to known quantities of ingested glyphosate, our objectives were to test the robustness of the mathematical model currently used to calculate glyphosate daily intake, and to propose alternative models based on urinary excretion kinetics. Our results support that the quantity of ingested glyphosate is systematically underestimated by the model currently used by regulatory agencies, whereas the other models evaluated showed better estimations, with differences according to gender. Our results also show a great variability between individuals, leading to some uncertainties notably with regards to the ADI, and further support that glyphosate excretion varies significantly among individuals who follow a similar dosing regimen. In conclusion, our study highlights the lack of reliability of assessment processes carried out by regulatory agencies for glyphosate in particular, and pesticides in general, and questions the relevance of such processes supposed to safeguard human health and the environment.

In vitro dissolution/permeation tools for amorphous solid dispersions bioavailability forecasting II: Comparison and mechanistic insights

Along with the increasing demand for complex formulations comes the need for appropriate in vitro methodologies capable of predicting their corresponding in vivo performance and the mechanisms controlling the drug release which can impact on in vivo drug absorption. In vitro dissolution-permeation (D/P) methodologies that can account for the effects of enabling formulations on the permeability of drugs are increasingly being used in performance ranking during early development stages. This work comprised the application of two different cell-free in vitro D/P setups: BioFLUX™ and PermeaLoop™ to evaluate the dissolution-permeation interplay upon drug release from itraconazole (ITZ)- HPMCAS amorphous solid dispersions (ASDs) of different drug loads. A solvent-shift approach was employed, from a simulated gastric environment to a simulated intestinal environment in the donor compartment. PermeaLoop™ was then combined with microdialysis sampling to separate the dissolved (free) drug from other species present in solution, like micelle-bound drug and drug-rich colloids, in real time. This setup was applied to clarify the mechanisms for drug release and permeation from these ASDs. In parallel, a pharmacokinetic study (dog model) was conducted to assess the drug absorption from these ASDs and to compare the in vivo results with the data obtained from each in vitro D/P setup, allowing to infer which would be the most adequate setup for ASD ranking. Even though both D/P systems resulted in the same qualitative ranking, BioFLUX™ overpredicted the difference between the in vivo AUC of two ASDs, whereas PermeaLoop™ permeation flux resulted in a good correlation with the AUC observed in pharmacokinetic studies (dog model) (R2 ≈ 0.98). Also, PermeaLoop™ combined with a microdialysis sampling probe clarified the mechanisms for drug release and permeation from these ASDs. It demonstrated that the free drug was the only driving force for permeation, while the drug-rich colloids kept permeation active for longer periods by acting as drug reservoirs and maintaining constant high levels of free drug in solution, which are then immediately able to permeate. Hence, the data obtained points BioFLUX™ and PermeaLoop™ applications to different momentums in the drug product development pipeline: while BioFLUX™, an automated standardized method, poses as a valuable tool for initial ASD ranking during the early development stages, PermeaLoop™ combined with microdialysis sampling allows to gain mechanistic understanding of the dissolution-permeation interplay, being crucial to fine tune and identify leading ASD candidates prior to in vivo testing.

Strain differences in the drug transport capacity of intestinal glucose transporters in Sprague-Dawley versus Wistar rats, C57BL/6J versus Kunming mice

Designing oral drug delivery systems using intestinal glucose transporters (IGTs) may be one of the strategies for improving oral bioavailability of drugs. However, little is known about the biological factors affecting the drug transport capacity of IGTs. Gastrodin is a sedative drug with a structure very similar to glucose. It is a highly water-soluble phenolic glucoside. It can hardly enter the intestine through simple diffusion but exhibits good oral bioavailability of over 80%. We confirmed that gastrodin is absorbed via the intestinal glucose transport pathway. It has the highest oral bioavailability among the reported glycosides' active ingredients through this pathway. Thus, gastrodin is the most selective drug substrate of IGTs and can be used to evaluate the drug transport capacity of IGTs. Obviously, strain is one of the main biological factors affecting drug absorption. This study firstly compared the drug transport capacity of IGTs between SD rats and Wistar rats and between C57 mice and KM mice by pharmacokinetic experiments and single-pass intestinal perfusion experiments of gastrodin. Then, the sodium-dependent glucose transporter type 1 (SGLT1) and sodium-independent glucose transporters type 2 (GLUT2) in the duodenum, jejunum, ileum and colon of these animals were quantified using RT-qPCR and Western blot. The results showed that the oral bioavailability of gastrodin in Wistar rats was significantly higher than in SD rats and significantly higher in KM mice than in C57 mice. Gastrodin absorption significantly differed among different intestinal segments in SD rats, C57 mice and KM mice, except Wistar rats. RT-qPCR and Western blot demonstrated that the intestinal expression distribution of SGLT1 and GLUT2 in SD rats and C57 mice was duodenum ≈ jejunum > ileum > colon. SGLT1 expression did not differ among different intestinal segments in KM mice, whereas the intestinal expression distribution of GLUT2 was duodenum ≈ jejunum ≈ ileum > colon. However, the expression of SGLT1 and GLUT2 did not differ among different intestinal segments in Wistar rats. It was reported that the intestinal expression distribution of SGLT1 and GLUT2 in humans is duodenum > jejunum > ileum > colon. Hence, the intestinal expression distribution of SGLT1 and GLUT2 of SD rats and C57 mice was more similar to that in humans. In conclusion, the drug transport capacity of IGTs differs in different strains of rats and mice. SD rats and C57 mice are more suitable for evaluating the pharmacokinetics of glycosides' active ingredients absorbed via the intestinal glucose transport pathway.

Assessment of food effects during clinical development

Food-drug interactions frequently hamper oral drug development due to various physicochemical, physiological and formulation-dependent mechanisms. This has stimulated the development of a range of promising biopharmaceutical assessment tools which, however, lack standardized settings and protocols. Hence, this manuscript aims to provide an overview of the general approach and the methodology used in food effect assessment and prediction. For in vitro dissolution-based predictions, the expected food effect mechanism should be carefully considered when selecting the level of complexity of the model, together with its drawbacks and advantages. Typically, in vitro dissolution profiles are then incorporated into physiologically based pharmacokinetic models, which can estimate the impact of food-drug interactions on bioavailability within 2-fold prediction error, at least. Positive food effects related to drug solubilization in the GI tract are easier to predict than negative food effects. Preclinical animal models also provide a good level of food effect prediction, with beagle dogs remaining the gold standard. When solubility-related food-drug interactions have large clinical impact, advanced formulation approaches can be used to improve fasted state pharmacokinetics, hence decreasing the fasted/fed difference in oral bioavailability. Finally, the knowledge from all studies should be combined to secure regulatory approval of the labelling instructions.

Prediction of Oral Drug Absorption in Rats from In Vitro Data

PURPOSE

In drug discovery, rats are widely used for pharmacological and toxicological studies. We previously reported that a mechanism-based oral absorption model, the gastrointestinal unified theoretical framework (GUT framework), can appropriately predict the fraction of a dose absorbed (Fa) in humans and dogs. However, there are large species differences between humans and rats. The purpose of the present study was to evaluate the predictability of the GUT framework for rat Fa.

METHOD

The Fa values of 20 model drugs (a total of 39 Fa data) were predicted in a bottom-up manner. Based on the literature survey, the bile acid concentration (C_bile) and the intestinal fluid volume were set to 15 mM and 4 mL/kg, respectively, five and two times higher than in humans. LogP, pK_a, molecular weight, intrinsic solubility, bile micelle partition coefficients, and Caco-2 permeability were used as input data.

RESULTS

The Fa values were appropriately predicted for highly soluble drugs (absolute average fold error (AAFE) = 1.65, 18 Fa data) and poorly soluble drugs (AAFE = 1.57, 21 Fa data). When the species difference in C_bile was ignored, Fa was over- and under-predicted for permeability and solubility limited cases, respectively. High C_bile in rats reduces the free fraction of drug molecules available for epithelial membrane permeation while increasing the solubility of poorly soluble drugs.

CONCLUSION

The Fa values in rats were appropriately predicted by the GUT framework. This result would be of great help for a better understanding of species differences and model-informed preclinical formulation development.

Approaches for estimating the clinical starting dose of new dosage forms: An example of a long-acting injectable formulation of finasteride

In our previous study, a long-acting injectable (LAI) formulation of finasteride was prepared as a new dosage form of PROPECIA®, and in vivo pharmacokinetics (PKs)-pharmacodynamics (PDs) was evaluated in beagle dogs. The resulting PK-PD profiles of the formulation showed pharmacological effects and achievability for monthly delivery. In this study, a first-in-human (FIH) dose of the LAI formulation loaded with finasteride was predicted. The three approaches were used for estimating a FIH dose of the LAI formulation: (1) No observed adverse effect level (NOAEL)-based approach; (2) Pharmacokinetically-guided approach; (3) Pharmacokinetic/pharmacodynamic model-based approach. The advantage, assumptions, limitations, and estimated FIH dose from each approach was discussed and compared since there is no consensus on the best approach. For the prediction of clinical exposures and estimation of FIH doses, the clinical PK-PD parameters were allometrically scaled from the nonclinical data, extracted from reported clinical studies, or fixed from published literature. The starting dose range of the LAI formulation (as finasteride) was estimated to be 16.80-81.06 mg from the three approaches, and the PK/PD model-based approach suggests the most optimal starting dose (16.80 mg) of the LAI formulation. The approaches for estimating starting doses presented in the study could be used as a basis for an Investigational New Drug (IND) application of new dosage forms.

Development of 3D-Bioprinted Colitis-Mimicking Model to Assess Epithelial Barrier Function Using Albumin Nano-Encapsulated Anti-Inflammatory Drugs

Physiological barrier function is very difficult to replicate in vitro. This situation leads to poor prediction of candidate drugs in the drug development process due to the lack of preclinical modelling for intestinal function. By using 3D bioprinting, we generated a colitis-like condition model that can evaluate the barrier function of albumin nanoencapsulated anti-inflammatory drugs. Histological characterization demonstrated the manifestation of the disease in 3D-bioprinted Caco-2 and HT-29 constructs. A comparison of proliferation rates in 2D monolayer and 3D-bioprinted models was also carried out. This model is compatible with currently available preclinical assays and can be implemented as an effective tool for efficacy and toxicity prediction in drug development.

In Silico Prediction of Human Clinical Pharmacokinetics with ANDROMEDA by Prosilico: Predictions for an Established Benchmarking Data Set, a Modern Small Drug Data Set, and a Comparison with Laboratory Methods

There is an ongoing aim to replace animal and in vitro laboratory models with in silico methods. Such replacement requires the successful validation and comparably good performance of the alternative methods. We have developed an in silico prediction system for human clinical pharmacokinetics, based on machine learning, conformal prediction and a new physiologically-based pharmacokinetic model, i.e. ANDROMEDA. The objectives of this study were: a) to evaluate how well ANDROMEDA predicts the human clinical pharmacokinetics of a previously proposed benchmarking data set comprising 24 physicochemically diverse drugs and 28 small drug molecules new to the market in 2021; b) to compare its predictive performance with that of laboratory methods; and c) to investigate and describe the pharmacokinetic characteristics of the modern drugs. Median and maximum prediction errors for the selected major parameters were ca 1.2 to 2.5-fold and 16-fold for both data sets, respectively. Prediction accuracy was on par with, or better than, the best laboratory-based prediction methods (superior performance for a vast majority of the comparisons), and the prediction range was considerably broader. The modern drugs have higher average molecular weight than those in the benchmarking set from 15 years earlier (ca 200 g/mol higher), and were predicted to (generally) have relatively complex pharmacokinetics, including permeability and dissolution limitations and significant renal, biliary and/or gut-wall elimination. In conclusion, the results were overall better than those obtained with laboratory methods, and thus serve to further validate the ANDROMEDA in silico system for the prediction of human clinical pharmacokinetics of modern and physicochemically diverse drugs.

Discovery of Paltusotine (CRN00808), a Potent, Selective, and Orally Bioavailable Non-peptide SST2 Agonist

The discovery of a novel 4-(4-aminopiperidinyl)-3,6-diarylquinoline series of potent SST2 agonists is described. This class of molecules exhibit excellent selectivity over SST1, SST3, SST4, and SST5 receptors. The compound 3-[4-(4-aminopiperidin-1-yl)-3-(3,5-difluorophenyl)quinolin-6-yl]-2-hydroxybenzonitrile (22, paltusotine, formerly known as CRN00808) showed no direct inhibition of major cytochrome P450 enzymes or the hERG ion channel and had sufficient exposure in rats and excellent exposure in dogs upon oral dosing. In pharmacodynamic studies, compound 22 dose-dependently suppressed growth hormone (GH) secretion induced by an exogenous growth-hormone-releasing hormone (GHRH) challenge in both male and female rats following a single oral dose and suppressed IGF-1 levels with repeated oral administration in both rats and dogs. To the best of our knowledge, compound 22 is the first non-peptide SST2 agonist to advance to human clinical trials and is currently in Phase 3 trials in acromegaly patients and a Phase 2 trial in neuroendocrine tumor patients suffering from carcinoid syndrome.

In vivo pharmacokinetic analyses of placental transfer of three drugs of different physicochemical properties in pregnant rats

Although the use of medication during pregnancy is common, information on exposure to the developing fetus and potential teratogenic effects is often lacking. This study used a rat model to examine the placental transfer of three small-molecule drugs with molecular weights ranging from approximately 300 to 800 Da with different physicochemical properties. Time-mated Sprague Dawley (Hsd:SD) rats aged 11-13 weeks were administered either glyburide, rifaximin, or fentanyl at gestational day 15. Maternal blood, placentae, and fetuses were collected at 5 min, 30 min, 1 h, 4 h, 8 h, 24 h, 48 h, and 96 h post-dose. To characterize the rate and extent of placental drug transfer, we calculated several pharmacokinetic parameters such as maximum concentration (Cmax), time to maximum concentration (Tmax), area under the concentration-time curve (AUC), half-life (t_1/2), clearance (CL), and volume of distribution (Vd) for plasma, placenta, and fetus tissues. The results indicated showed that fetal exposure was lowest for glyburide, accounting for only 2.2 % of maternal plasma exposure as measured by their corresponding AUC ratio, followed by rifaximin (37.9 %) and fentanyl (172.4 %). The fetus/placenta AUC ratios were found to be 10.7 % for glyburide, 11.8 % for rifaximin, and 39.1 % for fentanyl. These findings suggest that although the placenta acts as a protective shield for the fetus, the extent of protection varies for different drugs and depends on factors such as molecular weight, lipid solubility, transporter-mediated efflux, and binding to maternal and fetal plasma proteins.

Sex Differences in Intestinal P-Glycoprotein Expression in Wistar versus Sprague Dawley Rats

Wistar and Sprague Dawley are the most common strains of rat used in pharmaceutical research and are used interchangeably in pre-clinical drug development. No studies have assessed whether Wistar and Sprague Dawley rats are equivalent in the gastrointestinal factors that influence oral drug absorption, specifically in relation to intestinal transporters. Enzyme-linked immunosorbent assay (ELISA) and liquid chromatography–tandem mass spectrometry (LC-MS/MS) are two reliable methods for quantifying intestinal protein levels with their own distinct advantages and limitations. In this study, P-glycoprotein (P-gp), a key efflux transporter, was quantified using ELISA and LC-MS/MS along the complete intestinal tract of male and female Wistar and Sprague Dawley rats. This work presents that Sprague Dawley rats have innately higher baseline P-gp expression than Wistar rats. Significant sex differences in P-gp expression were identified in the jejunum, ileum and colon between male and female Wistar rats using both techniques, with males exhibiting higher P-gp levels. Sprague Dawley rats showed no sex differences in P-gp expression through ELISA and LC-MS/MS. Both methods demonstrated similar trends for P-gp quantification, but ELISA could offer faster data acquisition. Our findings report significant sex differences between the strains and highlight that Wistar and Sprague Dawley rats are not equivalent in their P-gp expression. As humans exhibit distinct sex differences in intestinal P-gp levels, Wistar rats may therefore be a more suitable pre-clinical animal strain to model oral drug absorption of P-gp substrates in male and female subjects.

Developing Clinically Relevant Dissolution Specifications (CRDSs) for Oral Drug Products: Virtual Webinar Series

A webinar series that was organised by the Academy of Pharmaceutical Sciences Biopharmaceutics focus group in 2021 focused on the challenges of developing clinically relevant dissolution specifications (CRDSs) for oral drug products. Industrial scientists, together with regulatory and academic scientists, came together through a series of six webinars, to discuss progress in the field, emerging trends, and areas for continued collaboration and harmonisation. Each webinar also hosted a Q&A session where participants could discuss the shared topic and information. Although it was clear from the presentations and Q&A sessions that we continue to make progress in the field of CRDSs and the utility/success of PBBM, there is also a need to continue the momentum and dialogue between the industry and regulators. Five key areas were identified which require further discussion and harmonisation.

Evaluation of the Success of High-Throughput Physiologically Based Pharmacokinetic (HT-PBPK) Modeling Predictions to Inform Early Drug Discovery

Minimizing in vitro and in vivo testing in early drug discovery with the use of physiologically based pharmacokinetic (PBPK) modeling and machine learning (ML) approaches has the potential to reduce discovery cycle times and animal experimentation. However, the prediction success of such an approach has not been shown for a larger and diverse set of compounds representative of a lead optimization pipeline. In this study, the prediction success of the oral (PO) and intravenous (IV) pharmacokinetics (PK) parameters in rats was assessed using a “bottom-up” approach, combining in vitro and ML inputs with a PBPK model. More than 240 compounds for which all of the necessary inputs and PK data were available were used for this assessment. Different clearance scaling approaches were assessed, using hepatocyte intrinsic clearance and protein binding as inputs. In addition, a novel high-throughput PBPK (HT-PBPK) approach was evaluated to assess the scalability of PBPK predictions for a larger number of compounds in drug discovery. The results showed that bottom-up PBPK modeling was able to predict the rat IV and PO PK parameters for the majority of compounds within a 2- to 3-fold error range, using both direct scaling and dilution methods for clearance predictions. The use of only ML-predicted inputs from the structure did not perform well when using in vitro inputs, likely due to clearance miss predictions. The HT-PBPK approach produced comparable results to the full PBPK modeling approach but reduced the simulation time from hours to seconds. In conclusion, a bottom-up PBPK and HT-PBPK approach can successfully predict the PK parameters and guide early discovery by informing compound prioritization, provided that good in vitro assays are in place for key parameters such as clearance.

Nanocarrier Drug Delivery Systems: Characterization, Limitations, Future Perspectives and Implementation of Artificial Intelligence

There has been an increasing demand for the development of nanocarriers targeting multiple diseases with a broad range of properties. Due to their tiny size, giant surface area and feasible targetability, nanocarriers have optimized efficacy, decreased side effects and improved stability over conventional drug dosage forms. There are diverse types of nanocarriers that have been synthesized for drug delivery, including dendrimers, liposomes, solid lipid nanoparticles, polymersomes, polymer-drug conjugates, polymeric nanoparticles, peptide nanoparticles, micelles, nanoemulsions, nanospheres, nanocapsules, nanoshells, carbon nanotubes and gold nanoparticles, etc. Several characterization techniques have been proposed and used over the past few decades to control and predict the behavior of nanocarriers both in vitro and in vivo. In this review, we describe some fundamental in vitro, ex vivo, in situ and in vivo characterization methods for most nanocarriers, emphasizing their advantages and limitations, as well as the safety, regulatory and manufacturing aspects that hinder the transfer of nanocarriers from the laboratory to the clinic. Moreover, integration of artificial intelligence with nanotechnology, as well as the advantages and problems of artificial intelligence in the development and optimization of nanocarriers, are also discussed, along with future perspectives.

Effects of alpha lipoic acid on metabolic syndrome: A comprehensive review

Metabolic syndrome (MetS) is a multifactorial disease with medical conditions such as hypertension, diabetes, obesity, dyslipidemia, and insulin resistance. Alpha-lipoic acid (α-LA) possesses various pharmacological effects, including antidiabetic, antiobesity, hypotensive, and hypolipidemia actions. It exhibits reactive oxygen species scavenger properties against oxidation and age-related inflammation and refines MetS components. Also, α-LA activates the 5' adenosine monophosphate-activated protein kinase and inhibits the NFκb. It can decrease cholesterol biosynthesis, fatty acid β-oxidation, and vascular stiffness. α-LA decreases lipogenesis, cholesterol biosynthesis, low-density lipoprotein and very low-density lipoprotein levels, and atherosclerosis. Moreover, α-LA increases insulin secretion, glucose transport, and insulin sensitivity. These changes occur via PI3K/Akt activation. On the other hand, α-LA treats central obesity by increasing adiponectin levels and mitochondrial biogenesis and can reduce food intake mainly by SIRT1 stimulation. In this review, the most relevant articles have been discussed to determine the effects of α-LA on different components of MetS with a special focus on different molecular mechanisms behind these effects. This review exhibits the potential properties of α-LA in managing MetS; however, high-quality studies are needed to confirm the clinical efficacy of α-LA.

Swine models for translational oncological research: an evolving landscape and regulatory considerations

Swine biomedical models have been gaining in popularity over the last decade, particularly for applications in oncology research. Swine models for cancer research include pigs that have severe combined immunodeficiency for xenotransplantation studies, genetically modified swine models which are capable of developing tumors in vivo, as well as normal immunocompetent pigs. In recent years, there has been a low success rate for the approval of new oncological therapeutics in clinical trials. The two leading reasons for these failures are either due to toxicity and safety issues or lack of efficacy. As all therapeutics must be tested within animal models prior to clinical testing, there are opportunities to expand the ability to assess efficacy and toxicity profiles within the preclinical testing phases of new therapeutics. Most preclinical in vivo testing is performed in mice, canines, and non-human primates. However, swine models are an alternative large animal model for cancer research with similarity to human size, genetics, and physiology. Additionally, tumorigenesis pathways are similar between human and pigs in that similar driver mutations are required for transformation. Due to their larger size, the development of orthotopic tumors is easier than in smaller rodent models; additionally, porcine models can be harnessed for testing of new interventional devices and radiological/surgical approaches as well. Taken together, swine are a feasible option for preclinical therapeutic and device testing. The goals of this resource are to provide a broad overview on regulatory processes required for new therapeutics and devices for use in the clinic, cross-species differences in oncological therapeutic responses, as well as to provide an overview of swine oncology models that have been developed that could be used for preclinical testing to fulfill regulatory requirements.

Influence of methylxanthines isolated from Bancha green tea on the pharmacokinetics of sildenafil in rats

BACKGROUND

Sildenafil is used to treat erectile dysfunction and pulmonary arterial hypertension and is metabolized in the liver mainly by CYP3A4, thus co-administration with drugs or herbal extracts that affect CYP3A4 activity may lead to drug-drug or drug-herb interactions, respectively. The aim of the present study was to evaluate the influence of single and multiple oral doses of methylxanthine fraction, isolated from Bancha green tea leaves on the pharmacokinetics of sildenafil in rats.

METHODS

Rats were given sildenafil alone as well as simultaneously with methylxanthines or ketoconazole. The plasma concentrations of sildenafil were measured with high-performance liquid chromatography method with ultraviolet detection. The pharmacokinetic parameters of sildenafil were calculated by non-compartmental analysis.

RESULTS

Concomitant use of sildenafil with a single oral dose of methylxanthines resulted in a decrease in C_max (p > 0.05), AUC_0-t (p < 0.05) and AUC_0-inf (p < 0.05), while the administration of sildenafil after methylxanthines pretreatment resulted in an increase in C_max (p < 0.0001), AUC_0-t (p < 0.0001) and AUC_0-inf (p < 0.001) compared to the sildenafil group. After co-administration of sildenafil and ketoconazole, a significant increase in C_max, AUC_0-t and AUC_0-inf was observed in both of the experiments.

CONCLUSION

Drug-herb interactions were observed when sildenafil was co-administered with Bancha methylxanthines in rats. Further in vivo studies about the potential drug interactions between sildenafil and methylxanthines, especially caffeine, are needed to clarify mechanisms underlying the observed changes in sildenafil pharmacokinetics.

Recent Analytical Approaches for the Study of Bioavailability and Metabolism of Bioactive Phenolic Compounds

The study of the bioavailability of bioactive compounds is a fundamental step for the development of applications based on them, such as nutraceuticals, functional foods or cosmeceuticals. It is well-known that these compounds can undergo metabolic reactions before reaching therapeutic targets, which may also affect their bioactivity and possible applications. All recent studies that have focused on bioavailability and metabolism of phenolic and terpenoid compounds have been developed because of the advances in analytical chemistry and metabolomics approaches. The purpose of this review is to show the role of analytical chemistry and metabolomics in this field of knowledge. In this context, the different steps of the analytical chemistry workflow (design study, sample treatment, analytical techniques and data processing) applied in bioavailability and metabolism in vivo studies are detailed, as well as the most relevant results obtained from them.

Development of a Once-Daily Modified-Release Formulation for the Short Half-Life RIPK1 Inhibitor GSK2982772 using DiffCORE Technology

Purpose

GSK2982772 is a selective inhibitor of receptor-interacting protein kinase-1 (RIPK1) with a short 2- to 3-h half-life. In a previous modified-release (MR) study, a matrix monolithic formulation (80% GSK2982772 released over 12 h) provided a once-daily (QD) pharmacokinetic (PK) profile in the fasted state; however, it was susceptible to food effects. The current study evaluated the safety and PK of MR formulations using GSK proprietary DiffCORE™ technology.

Methods

Part A evaluated PK following single-dose (240 mg) fasted and fed (high-fat meal) administration of three DiffCORE MR formulations within pre-defined in vitro extremes of 80% GSK2982772 released over 12 h (MR-12 h) to 80% GSK2982772 released over 18 h (MR-18 h) versus an immediate-release formulation. Part B evaluated MR-16 h (120–960 mg) in different prandial states.

Results

Pharmacokinetic profiles for all MR formulations and doses tested in the fasted and fed states were consistent with QD dosing.

Conclusions

The DiffCORE technology overcame the food effect vulnerability observed with the matrix monolithic formulation. The MR-16 h formulation was selected for further clinical development as a QD dosing regimen (NCT03649412 September 26, 2018).

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-021-03124-7.

Pharmacokinetic/pharmacodynamic modeling for dose selection for the first-in-human trial of the activated Factor XII inhibitor garadacimab (CSL312)

Factor XII (FXII) is a serine protease involved in multiple cascades, including the kallikrein–kinin system. It may play a role in diseases in which the downstream cascades are dysregulated, such as hereditary angioedema. Garadacimab (CSL312) is a first‐in‐class, fully human, monoclonal antibody targeting activated FXII (FXIIa). We describe how translational pharmacokinetic (PK) and pharmacodynamic (PD) modeling enabled dose selection for the phase I, first‐in‐human trial of garadacimab. The PK/PD data used for modeling were derived from preclinical PK/PD and safety studies. Garadacimab plasma concentrations rose with increasing dose, and clear dose‐related PD effects were observed (e.g., a mechanism‐based prolongation of activated partial thromboplastin time). The PK/PD profile from cynomolgus monkeys was used to generate minimal physiologically‐based pharmacokinetic (mPBPK) models with target‐mediated drug disposition (TMDD) for data prediction in cynomolgus monkeys. These models were later adapted for prediction of human data to establish dose selection. Based on the final mPBPK model with TMDD and assuming a weight of 70 kg for an adult human, a minimal inhibition (<10%) of FXIIa with a starting dose of 0.1 mg/kg garadacimab and a near maximal inhibition (>95%) at 10 mg/kg garadacimab were predicted. The phase I study is complete, and data on exposure profiles and inhibition of FXIIa‐mediated kallikrein activity observed in the trial support and validate these simulations. This emphasizes the utility and relevance of translational modeling and simulation in drug development.

A White Paper on Collagen Hydrolyzates and Ultrahydrolyzates: Potential Supplements to Support Joint Health in Osteoarthritis?

PURPOSE OF REVIEW

Osteoarthritis (OA) is the most common forms of arthritis in the general population, accounting for more pain and functional disability than any other musculoskeletal disease. There are currently no approved disease modifying drugs for OA. In the absence of effective pharmacotherapy, many patients with OA turn to nutritional supplements and nutraceuticals, including collagen derivatives. Collagen hydrolyzates and ultrahydrolyzates are terms used to describe collagens that have been broken down into small peptides and amino acids in the presence of collagenases and high pressure.

RECENT FINDINGS

This article reviews the relevant literature and serves as a White Paper on collagen hydrolyzates and ultrahydrolyzates as emerging supplements often advertised to support joint health in OA. Collagen hydrolyzates have demonstrated some evidence of efficacy in a handful of small scale clinical trials, but their ability to treat and reverse advanced joint disease remains highly speculative, as is the case for other nutritional supplements. The aim of this White Paper is to stimulate research and development of collagen-based supplements for patients with OA and other musculoskeletal diseases at academic and industrial levels. This White Paper does not make any treatment recommendations for OA patients in the clinical context, but simply aims to highlight opportunities for scientific innovation and interdisciplinary collaboration, which are crucial for the development of novel products and nutritional interventions based on the best available and published evidence.

Progesterone Metabolism by Human and Rat Hepatic and Intestinal Tissue

Following oral administration, the bioavailability of progesterone is low and highly variable. As a result, no clinically relevant, natural progesterone oral formulation is available. After oral delivery, first-pass metabolism initially occurs in the intestines; however, very little information on progesterone metabolism in this organ currently exists. The aim of this study is to investigate the contributions of liver and intestine to progesterone clearance. In the presence of NADPH, a rapid clearance of progesterone was observed in human and rat liver samples (t_1/2 2.7 and 2.72 min, respectively). The rate of progesterone depletion in intestine was statistically similar between rat and human (t_1/2 197.6 min in rat and 157.2 min in human). However, in the absence of NADPH, progesterone was depleted at a significantly lower rate in rat intestine compared to human. The roles of aldo keto reductases (AKR), xanthine oxidase (XAO) and aldehyde oxidase (AOX) in progesterone metabolism were also investigated. The rate of progesterone depletion was found to be significantly reduced by AKR1C, 1D1 and 1B1 in human liver and by AKR1B1 in human intestine. The inhibition of AOX also caused a significant reduction in progesterone degradation in human liver, whereas no change was observed in the presence of an XAO inhibitor. Understanding the kinetics of intestinal as well as liver metabolism is important for the future development of progesterone oral formulations. This novel information can inform decisions on the development of targeted formulations and help predict dosage regimens.

Measuring the oral bioavailability of protein hydrolysates derived from food sources: A critical review of current bioassays

BACKGROUND

Food proteins are a source of hydrolysates with potentially useful biological attributes. Bioactive peptides from food-derived proteins are released from hydrolysates using exogenous industrial processes or endogenous intestinal enzymes. Current in vitro permeability assays have limitations in predicting the oral bioavailability (BA) of bioactive peptides in humans. There are also difficulties in relating the low blood levels of food-derived bioactive peptides detected in preclinical in vivo models to pharmacodynamic read-outs relevant for humans.

SCOPE AND APPROACH

In this review, we describe in vitro assays of digestion, permeation, and metabolism as indirect predictors of the potential oral BA of hydrolysates and their constituent bioactive peptides. We discuss the relationship between industrial hydrolysis processes and the oral BA of hydrolysates and their peptide by-products.

KEY FINDINGS

Hydrolysates are challenging for analytical detection methods due to capacity for enzymatic generation of peptides with novel sequences and also new modifications of these peptides during digestion. Mass spectrometry and peptidomics can improve the capacity to detect individual peptides released from complex hydrolysates in biological milieu.

Gastrointestinal Digestion Model Assessment of Peptide Diversity and Microbial Fermentation Products of Collagen Hydrolysates

Osteoarthritis (OA), the most common form of arthritis, is associated with metabolic diseases and gut microbiome dysbiosis. OA patients often take supplements of collagen hydrolysates (CHs) with a high peptide content. Following digestion, some peptides escape absorption to induce prebiotic effects via their colonic fermentation to generate short-chain fatty acids (SCFAs), branched-chain fatty acids (BCFAs) and colonic gases (NH₄ and H₂S). The capacity of CHs to generate microbial metabolites is unknown. Proteomic analysis of two CHs (CH-GL and CH-OPT) demonstrated different native peptide profiles with increased peptide diversity after in vitro gastric and small intestinal digestion. Subsequent 24 h fermentation of the CH digests in a dynamic gastrointestinal (GI) digestion model containing human fecal matter showed that CH-OPT increased (p < 0.05) H₂S, SCFAs (propionic, butyric and valeric acids), BCFAs, and decreased NH₄ in the ascending colon reactor with no major changes seen with CH-GL. No major effects were observed in the transverse and descending vessels for either CH. These findings signify that CHs can induce prebiotic effects in the ascending colon that are CH dependent. More studies are needed to determine the physiological significance of CH-derived colonic metabolites, in view of emerging evidence connecting the gut to OA and metabolic diseases.

An overview of in vitro, ex vivo and in vivo models for studying the transport of drugs across intestinal barriers

Oral administration is the most commonly used route for drug delivery owing to its cost-effectiveness, ease of administration, and high patient compliance. However, the absorption of orally delivered compounds is a complex process that greatly depends on the interplay between the characteristics of the drug/formulation and the gastrointestinal tract. In this contribution, we review the different preclinical models (in vitro, ex vivo and in vivo) from their development to application for studying the transport of drugs across intestinal barriers. This review also discusses the advantages and disadvantages of each model. Furthermore, the authors have reviewed the selection and validation of these models and how the limitations of the models can be addressed in future investigations. The correlation and predictability of the intestinal transport data from the preclinical models and human data are also explored. With the increasing popularity and prevalence of orally delivered drugs/formulations, sophisticated preclinical models with higher predictive capacity for absorption of oral formulations used in clinical studies will be needed.

Oral Pharmacokinetics of Enriched Secoisolariciresinol Diglucoside and Its Polymer in Rats

Secoisolariciresinol diglucoside (SDG) is the principal lignan of flaxseed and precursor of its aglycone, secoisolariciresinol (SECO), and the mammalian lignans enterolactone (EL) and enterodiol (ED), the putative bioactive forms of oral administration of SDG. SDG is present in the seed hull as an ester-linked polymer. Although extraction and purification of SDG monomer is costly, the use of naturally occurring SDG in polymer form may offer a more economical approach for delivery of this precursor. The extent of SDG release from the polymer and subsequent bioavailability of SDG metabolites are unknown. To understand the relative bioavailability of SDG polymer, this study examined the comparative bioavailability of enriched SDG and SDG polymer in rats after a single oral SDG equivalent dose (40 mg/kg). A validated LC-MS/MS method quantified SDG and its metabolites in rat plasma following serial blood collections. SDG remained undetectable in rat plasma samples. Unconjugated SECO was detected in plasma after 0.25 h. Unconjugated ED was observed after 8 h (3.4 ± 3.3 ng/mL) and 12 h (6.2 ± 3.3 ng/mL) for enriched SDG and SDG polymer, respectively. Total (conjugated and unconjugated) ED and EL resulting from enriched SDG and SDG polymer reached similar maximal concentrations between 11 and 12 h and demonstrated similar total body exposures (AUC values). These data suggest a similar pharmacokinetic profile between the enriched and polymer form of SDG, providing support for the use of SDG polymer as a more economical precursor for SECO, ED, and EL in applications of chronic disease management.

Global Analysis of Models for Predicting Human Absorption: QSAR, In Vitro, and Preclinical Models

Models intended to predict intestinal absorption are an essential part of the drug development process. Although many models exist for capturing intestinal absorption, many questions still exist around the applicability of these models to drug types like "beyond rule of 5" (bRo5) and low absorption compounds. This presents a challenge as current models have not been rigorously tested to understand intestinal absorption. Here, we assembled a large, structurally diverse dataset of ∼1000 compounds with known in vitro, preclinical, and human permeability and/or absorption data. In silico (quantitative structure-activity relationship), in vitro (Caco-2), and in vivo (rat) models were statistically evaluated for predictive performance against this human intestinal absorption dataset. We expect this evaluation to serve as a resource for DMPK scientists and medicinal/computational chemists to increase their understanding of permeability and absorption model utility and applications for academia and industry.

Meta-Assessment of Metformin Absorption and Disposition Pharmacokinetics in Nine Species

The objective of this study was to systematically assess literature datasets and quantitatively analyze metformin PK in plasma and some tissues of nine species. The pharmacokinetic (PK) parameters and profiles of metformin in nine species were collected from the literature. Based on a simple allometric scaling, the systemic clearances (CL) of metformin in these species highly correlate with body weight (BW) (R2 = 0.85) and are comparable to renal plasma flow in most species except for rabbit and cat. Reported volumes of distribution (VSS) varied appreciably (0.32 to 10.1 L/kg) among species. Using the physiological and anatomical variables for each species, a minimal physiologically based pharmacokinetic (mPBPK) model consisting of blood and two tissue compartments (Tissues 1 and 2) was used for modeling metformin PK in the nine species. Permeability-limited distribution (low fd1 and fd2) and a single tissue-to-plasma partition coefficient (Kp) value for Tissues 1 and 2 were applied in the joint mPBPK fitting. Nonlinear regression analysis for common tissue distribution parameters along with species-specific CL values reasonably captured the plasma PK profiles of metformin across most species, except for rat and horse with later time deviations. In separate fittings of the mPBPK model to each species, Tissue 2 was considered as slowly-equilibrating compartment consisting of muscle and skin based on in silico calculations of the mean transit times through tissues. The well-fitted mPBPK model parameters for absorption and disposition PK of metformin for each species were compared with in vitro/in vivo results found in the literature with regard to the physiological details and physicochemical properties of metformin. Bioavailability and absorption rates decreased with the increased BW among the species. Tissues such as muscle dominate metformin distribution with low permeability and partitioning while actual tissue concentrations found in rats and mice show likely transporter-mediated uptake in liver, kidney, and gastrointestinal tissues. Metformin has diverse pharmacologic actions, and this assessment revealed allometric relationships in its absorption and renal clearance but considerable variability in actual and modeled tissue distribution probably caused by transporter differences.

Effect of fresh pomegranate juice on the pharmacokinetic profile of artemether: An open-label, randomized, 2- period crossover study in healthy human volunteers

This study was designed to evaluate the effect of fresh pomegranate (Punica granatum L.) juice on the pharmacokinetic profile of artemether in healthy volunteers. A randomized, open-label, crossover study was conducted on healthy subjects (n = 26). Each volunteer received 250 mL of fresh pomegranate juice twice daily for 2 weeks. On day 14, they were administered a single oral dose of artemether (80 mg) with either water or 250 mL of pomegranate juice. Thirteen blood samples were collected up to 12 h and 6 electrocardiograms were recorded. Plasma concentrations of artemether and its metabolite dihydroartemisinin were analyzed by a noncompartmental method using LC-MS/MS. The lower limit of detection (LLOD) and lower limit of quantification (LLOQ) for artemether were estimated as 0.3 and 0.8 ng/mL, respectively, while for dihydroartemisinin it was 0.2 and 0.6 ng/mL, respectively. The pharmacokinetic parameters of artemether and dihydroartemisinin were not significantly altered when co-administered with the fresh pomegranate juice. AUC _(0-∞) was slightly increased from 742 to 859 ng/mL for artemether [geometric mean ratio: 1.14 (95 % CI, 1.08,1.18); P = 0.45] and from 699 to 818 ng/mL for dihydroartemisinin [geometric mean ratio: 1.15 (95 % CI, 1.09, 1.15); P = 0.4]. Difference in C_max for artemether was also statistically non-significant [173 vs 195 ng/mL; geometric mean ratio: 1.09 (95 % CI, 0.91, 1.15); P = 0.61]. Likewise, elimination half-life (t_1/2) for both artemether and dihydroartemisinin remained unchanged (P = 0.43 and 0.31, respectively). In addition, there was no significant difference in t_max for artemether (P = 0.66) and its metabolite (P = 0.65). In conclusion, findings of the present study demonstrated that the administration of pomegranate juice had no significant effect on the pharmacokinetic profile of artemether.

Advances in Predictions of Oral Bioavailability of Candidate Drugs in Man with New Machine Learning Methodology

Oral bioavailability (F) is an essential determinant for the systemic exposure and dosing regimens of drug candidates. F is determined by numerous processes, and computational predictions of human estimates have so far shown limited results. We describe a new methodology where F in humans is predicted directly from chemical structure using an integrated strategy combining 9 machine learning models, 3 sets of structural alerts, and 2 physiologically-based pharmacokinetic models. We evaluate the model on a benchmark dataset consisting of 184 compounds, obtaining a predictive accuracy (Q²) of 0.50, which is successful according to a pharmaceutical industry proposal. Twenty-seven compounds were found (beforehand) to be outside the main applicability domain for the model. We compare our results with interspecies correlations (rat, mouse and dog vs. human) using the same dataset, where animal vs. human-correlations (R²) were found to be 0.21 to 0.40 and maximum prediction errors were smaller than maximum interspecies differences. We conclude that our method has sufficient predictive accuracy to be practically useful with applications in human exposure and dose predictions, compound optimization and decision making, with potential to rationalize drug discovery and development and decrease failures and overexposures in early clinical trials with candidate drugs.

An ex Vivo Model Enables Systematic Investigation of the Intestinal Absorption and Transcytosis of Oral Particulate Nanocarriers

Nanoparticulate formulations are being developed toward enhancing the bioavailability of orally administrated biologics. However, the processes mediating particulate carriers' intestinal uptake and transport remains to be fully elucidated. Herein, an optical clearing-based whole tissue mount/imaging strategy was developed to enable high quality microscopic imaging of intestinal specimens. It enabled the distribution of nanoparticles within intestinal villi to be quantitatively analyzed at a cellular level. Two-hundred and fifty nm fluorescent polystyrene nanoparticles were modified with polyethylene glycol (PEG), Concanavalin A (ConA), and pectin to yield mucopenetrating, enterocyte targeting, and mucoadhesive model nanocarriers, respectively. Introducing ConA on the PEGylated nanoparticles significantly increased their uptake in the intestinal epithelium (∼4.16 fold for 200 nm nanoparticle and ∼2.88 fold for 50 nm nanoparticles at 2 h). Moreover, enterocyte targeting mediated the trans-epithelial translocation of 50 nm nanoparticles more efficiently than that of the 200 nm nanoparticles. This new approach provides an efficient methodology to obtain detailed insight into the transcytotic activity of enterocytes as well as the barrier function of the constitutive intestinal mucus. It can be applied to guide the rational design of particulate formulations for more efficient oral biologics delivery.

Particle Forming Amorphous Solid Dispersions: A Mechanistic Randomized Pharmacokinetic Study in Humans

Amorphous solid dispersions (ASDs) are a promising drug-delivery strategy to overcome poor solubility through formulation. Currently, the understanding of drug absorption mechanisms from ASDs in humans is incomplete. Aiming to gain insights in this matter, we conducted a randomized cross-over design open-label clinical study (NCT03886766) with 16 healthy male volunteers in an ambulatory setting, using micro-dosed efavirenz as a model drug. In three phases, subjects were administered (1) solid ASD of efavirenz 50 mg or (2) dissolved ASD of efavirenz 50 mg or (3) a molecular solution of efavirenz 3 mg (non-ASD) as a control in block-randomized order. Endpoints were the pharmacokinetic profiles (efavirenz plasma concentration vs. time curves) and derived pharmacokinetic parameters thereof (AUC0-t, Cmax, tmax, and ka). Results showed that the dissolved ASD (intervention 2) exhibited properties of a supersaturated solution (compared to aqueous solubility) with rapid and complete absorption of the drug from the drug-rich particles. All interventions showed similar AUC0-t and were well tolerated by subjects. The findings highlight the potential of particle forming ASDs as an advanced drug-delivery system for poorly soluble drugs and provide essential insights into underlying mechanisms of ASD functioning in humans, partially validating current conceptual models.

A versatile, compartmentalised gut-on-a-chip system for pharmacological and toxicological analyses

A novel, integrated, in vitro gastrointestinal (GI) system is presented to study oral bioavailability parameters of small molecules. Three compartments were combined into one hyphenated, flow-through set-up. In the first compartment, a compound was exposed dynamically to enzymatic digestion in three consecutive microreactors, mimicking the processes of the mouth, stomach, and intestine. The resulting solution (chyme) continued to the second compartment, a flow-through barrier model of the intestinal epithelium allowing absorption of the compound and metabolites thereof. The composition of the effluents from the barrier model were analysed either offline by electrospray-ionisation-mass spectrometry (ESI-MS), or online in the final compartment using chip-based ESI-MS. Two model drugs, omeprazole and verapamil, were used to test the integrated model. Omeprazole was shown to be broken down upon treatment with gastric acid, but reached the cell barrier unharmed when introduced to the system in a manner emulating an enteric-coated formulation. In contrast, verapamil was unaffected by digestion. Finally, a reduced uptake of verapamil was observed when verapamil was introduced to the system dissolved in apple juice, a simple food matrix. It is envisaged that this integrated, compartmentalised GI system has potential for enabling future research in the fields of pharmacology, toxicology, and nutrition.

Guidance on safety evaluation of sources of nutrients and bioavailability of nutrient from the sources (Revision 1)

[Table: see text] This guidance describes the scientific data required to allow an evaluation of the safety of new substances that are proposed for use as sources of nutrients in food supplements, foods for the general population or foods for specific groups and an assessment of the bioavailability of the nutrient from the proposed source. This guidance describes the scientific data required to allow an evaluation of the safety of the source within the established framework for risk assessment of food additives and novel food ingredients and the bioavailability of the nutrient from this source. This document is arranged in five main sections: one on technical data aimed at characterising the proposed source and at identifying potential hazards resulting from its manufacture and stability in food; one on existing authorisations and evaluation, providing an overview of previous assessments on the proposed source and their conclusions; one on proposed uses and exposure assessment section, allowing an estimate of the dietary exposure to the source and the nutrient based on the proposed uses and use levels; one on toxicological data, describing approaches which can be used to identify (in conjunction with data on manufacture and composition) and to characterise hazards of the source and any relevant breakdown products; the final section on bioavailability focuses on determining the extent to which the nutrient from the proposed source is available for use by the body in comparison with one or more forms of the same nutrient that are already permitted for use on the positive lists. This guidance was adopted by the Panel on Food Additives and Nutrient Sources added to Food (ANS Panel) on 16 May 2018. Upon request from EFSA, the present guidance has been revised to inform applicants of new provisions set out in Regulation (EC) No 178/2002, as amended by Regulation (EU) 2019/1381 on the transparency and sustainability of the EU risk assessment in the food chain.

"Mucus-on-Chip": A new tool to study the dynamic penetration of nanoparticulate drug carriers into mucus

The mucus covering of epithelial tissues presents one significant biological barrier to the uptake and absorption of particulate carriers. Improved understanding of the mechanisms mediating the transport of nanoparticles across such mucus layers would accelerate their development as optimised mucosal drug delivery formulations (e.g. via oral and rectal routes). Herein, an in vitro mucus model ("Mucus-on-Chip") was developed to enable the interaction and transport of functionalised nanoparticles and reconstituted mucus to be quantitatively investigated in real-time. We verified that the diffusion of nanoparticles into mucus is highly dependent on their biointerfacial properties. Muco-inert modification (PEGylation) significantly enhanced the mucopenetration of 50 nm and 200 nm nanoparticles, whereas limited mucopenetration was observed for pectin coated mucoadhesive nanoparticles. Furthermore, this model can be easily adapted to mimic specific physiological mucus environments. Mucus pre-treated with a mucolytic agent displayed reduced barrier function and therefore significantly accelerated mucopenetration of nanoparticles, which was independent of their size and biointerfacial properties. This new "Mucus-on-Chip" methodology provides detailed insight into the dynamics of nanoparticle-mucus interaction, which can be applied to refine the design of particulate formulations for more efficient mucosal drug delivery.

Nanoparticles that do not compete with endogenous ligands - Molecular characterization in vitro, acute safety in canine, and interspecies pharmacokinetics modeling to humans

A vast majority, if not all of the receptor-mediated drug delivery systems utilize nanoparticles that are conjugated to physiological mimic ligands, with testing restricted to in vitro and rodent models. In this report, we present for the first time, a full spectrum characterization of transferrin receptor 1 (TfR1)-targeted polymeric nanoparticles (abbreviated, P2Ns-GA) that do not compete with endogenous transferrin, and serve as a versatile platform for oral drug delivery. Based on endocytosis inhibitors and receptor knockdown, the cellular uptake of P2Ns-GA is clathrin-mediated and dependent on TfR1 expression, but other trafficking mechanisms, particularly those involving caveolae/lipid rafts, can also play a role. The utility of P2Ns-GA in promoting the oral bioavailability of encapsulated compounds is demonstrated with a hydrophobic polyphenol, urolithin A (UA). When compared against plain UA or UA in ligand-free nanoparticles, UA-loaded P2Ns-GA led to markedly higher plasma concentrations among healthy canines, with no adverse health effects observed after oral dosing. Finally, a semi-mechanistic pharmacokinetic model was developed using both rat and dog datasets to quantitatively evaluate the effect of P2Ns-GA on oral bioavailability of UA. The model was allometrically scaled to humans to simulate clinical pharmacokinetics of plain UA and UA-loaded P2Ns-GA following oral administration.