Prediction of food effect by bile micelles on oral drug absorption considering free fraction in intestinal fluid

A high-throughput micro-scale workflow to quantify molecularly dissolved drug concentrations under solubilizing conditions

Physiological and artificial solubilizing agents usually enhance apparent solubility of poorly soluble drugs, and in many cases also oral drug exposure. However, exposure may decrease in cases where micellization reduces the molecularly dissolved drug fraction, overriding the solubility advantage. While this information is critical to accurately anticipate the effect of drug micellization on oral absorption, the experimental determination of molecularly dissolved drug concentrations is complex and time consuming. The present study aimed at developing a micro-scale in vitro workflow (comparative micro-scale mass transfer assay, CMMTA) to quantify molecularly dissolved (unbound) drug concentrations in the presence of solubilizing agents. A linear correlation was determined between the cumulative passive permeation of the model drug riluzole (RLZ) and its concentration in the donor buffer solution on a 96-well microtiter sandwich plate (PermeaPlain™). Next, the drug permeation from micellar drug solutions (in fasted and fed state simulated intestinal fluids, FaSSIF and FeSSIF) was measured and the concentration of unbound drug was derived from the aforementioned correlation. The results were validated against established methods to measure free (unbound) drug concentrations, namely equilibrium dialysis and microdialysis. The concentrations of molecularly dissolved RLZ were correctly captured on one single microtiter plate. Both, the standard curve and samples at different solubilizing conditions can be determined simultaneously within a few hours using small quantities of drug substance. Hence, the proposed CMMTA workflow represents a promising screening tool for early-stage drug development.

How the Magenstrasse is formed after meals: Protein aggregation hypothesis

Magenstrasse (stomach road) is reported to potentially influence the absorption of orally administered drugs by facilitating a gastric emptying of ingested water under postprandial condition. We hypothesized the Magenstrasse is a consequence of the formation of protein aggregates due to the decrease in gastric pH associated with stimulated gastric acid secretion. The formation mechanism of the Magenstrasse was examined in vitro using a gastric chamber system which reproduces postprandial conditions in the stomach. Oral liquid meals containing different amounts of proteins were mixed with simulated gastric fluid containing pepsin in the gastric chamber. When a high-protein liquid meal was used, infusion of gastric acid caused protein denaturation, generating semisolid aggregates. Then, to evaluate the impact of the aggregates, fluorescein isothiocyanate-dextran 4000 (FD-4) solution was added. The presence of protein aggregates facilitated the elution of FD-4 from the gastric chamber, indicating that the semisolid aggregates suppressed mixing of FD-4 solution with meals. In addition, formation of the same type of protein aggregates was observed in vivo in rat stomach after ingesting a high-protein liquid meal. These in vitro and in vivo results support the idea that protein aggregation of liquid meals in the stomach contributes the formation of the Magenstrasse.

Enhancing the pharmacokinetics of abiraterone acetate through lipid-based formulations: addressing solubility and food effect challenges

Abiraterone acetate, a prodrug of abiraterone, is an effective antiandrogen for treating metastatic prostate cancer. However, its poor aqueous solubility restricts oral bioavailability to under 10% in fasted conditions. Additionally, its pharmacokinetics are significantly influenced by food intake, leading to variable exposure that can impact treatment safety and efficacy. To overcome these challenges, we developed a series of lipid-based formulations aimed at reducing food effects and enhancing the fasted bioavailability of abiraterone acetate by incorporating the drug into colloidal delivery systems. Medium- and long-chain self-nanoemulsifying drug delivery systems (MC-SNEDDS and LC-SNEDDS) were formulated with abiraterone acetate loading at 80% of their respective preconcentrate equilibrium solubility. In-vitro gastrointestinal lipolysis experiments demonstrated that the SNEDDS formulations increased drug solubilisation by over 6-fold compared to pure abiraterone acetate and over 2-fold compared to the reference product after 60 min in the intestinal environment. In-vivo pharmacokinetic studies in rats revealed that both MC-SNEDDS and LC-SNEDDS formulations, along with their enteric-coated (EC) forms, exhibited enhanced bioavailability, with EC-LC-SNEDDS providing the highest performance, demonstrating a 7.32-fold increase in abiraterone exposure compared to the reference. Strong correlations were observed between in-vitro solubilisation and in-vivo AUC0 - 8 h (R2 = 0.980) and Cmax (R2 = 0.925). In-vivo pharmacokinetic studies in pigs demonstrated that EC-LC-SNEDDS improved drug systemic exposure in fasted conditions and mitigated positive food effects, showing a fed-to-fasted AUC0 - 8 h ratio of 108% compared to 334% with the reference. The developed lipid-based formulations hold promise in overcoming the pharmacokinetic challenges associated with abiraterone, potentially offering improved outcomes for patients.

The Particle Drifting Effect: A Combined Function of Colloidal and Drug Properties

The particle drifting effect, where nanosized colloidal drug particles overcome the diffusional resistance of the aqueous boundary layer adjacent to the intestinal wall and increase drug absorption rates, is drawing increasing attention in pharmaceutical research. However, mechanistic understanding and accurate prediction of the particle drifting effect remain lacking. In this study, we systematically evaluated the extent of the particle drifting effect affected by drug and colloidal properties, including the size, number, and type of the moving species using biphasic diffusion experiments combined with computational fluid dynamics simulations and mass transport analyses. The results showed that the particle drifting effect is a sequential reaction of particle dissolution/dissociation in the diffusional boundary layer, followed by absorption of the free drug. Therefore, factors affecting the rate-limiting step, which can be either process or both under different circumstances, alter the particle drifting effect. Experimental results also agree with the theory that the particle dissolution rate is dependent on particle size, concentration, and drug solubility. In addition, rapid bile micelle dissociation and bile salt absorption facilitated drug absorption by the particle drifting effect. Our findings explain the highly dynamic nature of the particle drifting effect and will contribute to rational formulation development and better bioavailability prediction for formulations containing colloidal particles.

An Artificial Gut/Absorption Simulator: Understanding the Impact of Absorption on In Vitro Dissolution, Speciation, and Precipitation of Amorphous Solid Dispersions

Upon dissolution, amorphous solid dispersions (ASDs) of poorly water-soluble compounds can generate supersaturated solutions consisting of bound and free drug species that are in dynamic equilibrium with each other. Only free drug is available for absorption. Drug species bound to bile micelles, polymer excipients, and amorphous and crystalline precipitate can reduce the drug solute's activity to permeate, but they can also serve as reservoirs to replenish free drug in solution lost to absorption. However, with multiple processes of dissolution, absorption, and speciation occurring simultaneously, it may become challenging to understand which processes lead to an increase or decrease in drug solution concentration. Closed, nonsink dissolution testing methods used routinely, in the absence of drug removal, allow only for static equilibrium to exist and obscure the impact of each drug species on absorption. An artificial gut simulator (AGS) introduced recently consists of a hollow fiber-based absorption module and allows mass transfer of the drug from the dissolution media at a physiological rate after tuning the operating parameters. In the present work, ASDs of varying drug loadings were prepared with a BCS-II model compound, ketoconazole (KTZ), and hypromellose acetate succinate (HPMCAS) polymer. Simultaneous dissolution and absorption testing of the ASDs was conducted with the AGS, and simple analytical techniques were utilized to elucidate the impact of bound drug species on absorption. In all cases, a lower amount of crystalline precipitate was formed in the presence of absorption relative to the nonsink dissolution "control". However, formation of HPMCAS-bound drug species and crystalline precipitate significantly reduced KTZ absorption. Moreover, at high drug loading, inclusion of an absorption module was shown to enhance ASD dissolution. The rank ordering of the ASDs with respect to dissolution was significantly different when nonsink dissolution versus AGS was used, and this discrepancy could be mechanistically elucidated by understanding drug dissolution and speciation in the presence of absorption.

Harnessing Bile for Drug Absorption through Rational Excipient Selection

Bile solubilization and apparent solubility at resorption sites critically affect the bioavailability of orally administered and poorly water-soluble drugs. Therefore, identification of drug-bile interaction may critically determine the overall formulation success. For the case of the drug candidate naporafenib, drug in solution at phase separation onset significantly improved with polyethylene glycol-40 hydrogenated castor oil (RH40) and amino methacrylate copolymer (Eudragit E) but not with hydroxypropyl cellulose (HPC) in both phosphate-buffered saline (PBS) and PBS supplemented with bile components. Naporafenib interacted with bile as determined by 1H and 2D 1H-1H nuclear magnetic resonance spectroscopy and so did Eudragit E and RH40 but not HPC. Flux across artificial membranes was reduced in the presence of Eudragit E. RH40 reduced the naporafenib supersaturation duration. HPC on the other side stabilized naporafenib's supersaturation and did not substantially impact flux. These insights on bile interaction correlated with pharmacokinetics (PK) in beagle dogs. HPC preserved naporafenib bile solubilization in contrast to Eudragit E and RH40, resulting in favorable PK.

Development and Validation of an Explainable Machine Learning-Based Prediction Model for Drug-Food Interactions from Chemical Structures

Possible drug-food constituent interactions (DFIs) could change the intended efficiency of particular therapeutics in medical practice. The increasing number of multiple-drug prescriptions leads to the rise of drug-drug interactions (DDIs) and DFIs. These adverse interactions lead to other implications, e.g., the decline in medicament's effect, the withdrawals of various medications, and harmful impacts on the patients' health. However, the importance of DFIs remains underestimated, as the number of studies on these topics is constrained. Recently, scientists have applied artificial intelligence-based models to study DFIs. However, there were still some limitations in data mining, input, and detailed annotations. This study proposed a novel prediction model to address the limitations of previous studies. In detail, we extracted 70,477 food compounds from the FooDB database and 13,580 drugs from the DrugBank database. We extracted 3780 features from each drug-food compound pair. The optimal model was eXtreme Gradient Boosting (XGBoost). We also validated the performance of our model on one external test set from a previous study which contained 1922 DFIs. Finally, we applied our model to recommend whether a drug should or should not be taken with some food compounds based on their interactions. The model can provide highly accurate and clinically relevant recommendations, especially for DFIs that may cause severe adverse events and even death. Our proposed model can contribute to developing more robust predictive models to help patients, under the supervision and consultants of physicians, avoid DFI adverse effects in combining drugs and foods for therapy.

Food effects on gastrointestinal physiology and drug absorption

Food ingestion affects the oral absorption of many drugs in humans. In this review article, we summarize the physiological factors in the gastrointestinal (GI) tract that affect the in vivo performance of orally administered solid dosage forms in fasted and fed states in humans. In particular, we discuss the effects of food ingestion on fluid characteristics (pH, bile concentration, and volume) in the stomach and small intestine, GI transit of water and dosage forms, and microbiota. Additionally, case examples of food effects on GI physiology and subsequent changes in oral drug absorption are provided. Furthermore, the effects of food, especially fruit juices (e.g., grapefruit, orange, apple) and green tea, on transporter-mediated permeation and enzyme-catalyzed metabolism of drugs in intestinal epithelial cells are also summarized comprehensively.

Bile and excipient interactions directing drug pharmacokinetics in rats

Bile solubilization plays a major role in the absorption of poorly water-soluble drugs. Excipients used in oral drug formulations impact bile-colloidal properties and their molecular interactions. Polymer-induced changes of bile colloids, e.g., by Eudragit E, reduced the flux of the bile interacting drug Perphenazine whereas bile non-interacting Metoprolol was not impacted. This study corroborates these in vitro findings in rats. Eudragit E significantly reduced systemic availability of Perphenazine but not Metoprolol compared to the oral administrations without polymer. This study confirms the necessity to carefully select polymers for bile interacting drugs whereas non-bile interacting drugs are more robust in terms of excipient choice for formulation. The perspective of bile interaction may introduce interesting biopharmaceutical leverage for better performing oral formulations of tomorrow.

Predicting Bile and Lipid Interaction for Drug Substances

Predicting biopharmaceutical characteristics and food effects for drug substances may substantially leverage rational formulation outcomes. We established a bile and lipid interaction prediction model for new drug substances and further explored the model for the prediction of bile-related food effects. One hundred and forty-one drugs were categorized as bile and/or lipid interacting and noninteracting drugs using ¹H nuclear magnetic resonance (NMR) spectroscopy. Quantitative structure-property relationship modeling with molecular descriptors was applied to predict a drug's interaction with bile and/or lipids. Bile interaction, for example, was indicated by two descriptors characterizing polarity and lipophilicity with a high balanced accuracy of 0.8. Furthermore, the predicted bile interaction correlated with a positive food effect. Reliable prediction of drug substance interaction with lipids required four molecular descriptors with a balanced accuracy of 0.7. These described a drug's shape, lipophilicity, aromaticity, and hydrogen bond acceptor capability. In conclusion, reliable models might be found through drug libraries characterized for bile interaction by NMR. Furthermore, there is potential for predicting bile-related positive food effects.

Liposomal Formulation for Oral Delivery of Cyclosporine A: Usefulness as a Semisolid-Dispersion System

PURPOSE

This study aims to understand the process and mechanism of oral drug absorption from liposomes and to verify the usefulness of liposomal formulation for poorly soluble drugs.

METHODS

Cyclosporine A (CsA) was used as a model drug and entrapped into Dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC) liposomes. Molecular state of CsA in the liposomes was analyzed using powder X-ray diffraction (PXRD) and polarized light microscopy (PLM). Release profiles of CsA from liposomes were observed in fasted state simulated intestinal fluid (FaSSIF). Oral absorption of CsA from liposomal formulations were investigated in rats.

RESULTS

PXRD and PLM analyses suggested that CsA exists in the lipid layer of liposomes as a molecular dispersed state. Although both liposomes retained CsA stably in the simple buffer, DPPC liposomes quickly released CsA within 10 min in FaSSIF due to the interaction with bile acid. In contrast, effect of bile acid was negligible in DSPC, indicating a high resistivity to membrane perturbation. Oral bioavailability of CsA from liposomal formulations were almost comparable with that from a marketed product (Neoral). However, the absorption profiles were clearly different. CsA was absorbed quickly from DPPC liposomes and Neoral, while sustained absorption profile was observed from DSPC liposomes. Further study in which ritonavir was co-entrapped in the liposomes with CsA showed the higher efficacy of ritonavir to increase oral bioavailability of CsA.

CONCLUSION

Liposomes allows the appropriate formulation design for oral delivery of poorly soluble drugs, not only to increase the extent but also to control the rate of absorption.

Effect of Ingested Fluid Volume and Solution Osmolality on Intestinal Drug Absorption: Impact on Drug Interaction with Beverages

It was recently shown that osmolality-dependent fluid movement is a significant factor causing the clinically observed apple juice (AJ)-atenolol interaction. Here we examined whether osmolality-dependent fluid movement may also explain the AJ volume dependence of the AJ-atenolol interaction. In Wistar rats, the luminal fluid volume after administration of different volumes of purified water (0.5 and 1.0 mL) gradually reduced to a similar steady-state level, while that after administration of different volumes of AJ (0.5 and 1.0 mL) increased and attained different apparent steady-state levels. It was hypothesized that osmolality-dependent fluid secretion would account for the volume dependence of the apparent steady-state. Indeed, the luminal concentration of FD-4, a non-permeable compound, after administration in AJ was attenuated depending upon the ingested volume, whereas that after administration in purified water was independent of the ingested fluid volume. An in vivo pharmacokinetic study in rats showed that co-administration of AJ and hyperosmotic solution (adjusted to the osmolality of AJ) with atenolol volume-dependently reduced the AUC and C_max of atenolol significantly. These results show that osmolality-dependent variations in luminal fluid volume may indirectly influence the absorption characteristics of drugs, and can account for the observed volume dependence of beverage-drug interactions.

Comparison of Predictions by BCS, rDCS and Machine Learning for the Effect of Food on Oral Drug Absorption Based on Features Calculated In silico

In this study, observed food effects of 473 drugs were categorized into positive, negative, or no effects and compared with the predictions made by machine learning (ML), the Biopharmaceutics Classification System (BCS) and refined Developability Classification System (rDCS). All methods used primarily in silico estimates for prediction, and for ML, four algorithms were evaluated using nested cross-validation to select important information from 371 features calculated based on the chemical structure. Approximately 18 features, including estimated solubility in biorelevant media, were selected as important, and the random forest classifier was the best among four algorithms with 36.6% error rate (ER) and 10.8% opposite prediction rate (OPR). The prediction by rDCS utilizing solubility in a biorelevant medium was somewhat inferior, but not by much; 41.0% ER and 11.4% OPR. Compared with these two methods, the prediction by BCS was inferior; 54.5% ER and 21.4% OPR. ER was improved modestly by using measured features instead of in silico estimates when BCS was applied to a subset of 151 drugs (46.4% from 55.0%). ML and rDCS predicted the food effects of the same subset using in silico estimates with ERs of 37.7% and 42.4%, respectively, suggesting that the predictions by ML and rDCS using in silico features are similar or more accurate than those by BCS using measured features. These results suggest that ML was useful in revealing essential features from complex information and, together with rDCS, is effective in predicting food effects during drug development, including early drug discovery.

Prediction of in vivo supersaturation and precipitation of poorly water-soluble drugs: Achievements and aspirations

This review focuses on options available to a pharmaceutical scientist to predict in vivo supersaturation and precipitation of poorly water-soluble drugs. As no single device or system can simulate the complex gastrointestinal environment, a combination of appropriate in vitro tools may be utilized to get optimal predictive information. To address the empirical issues encountered during small-scale and full-scale in vitro predictive testing, theoretical background and relevant case studies are discussed. The practical considerations for selection of appropriate tools at various stages of drug development are recommended. Upcoming technologies that have potential to further reduce in vivo studies and expedite the drug development process are also discussed.

In vitro-in vivo correlation in the effect of cyclodextrin on oral absorption of poorly soluble drugs

In this study the concentration effect of 2-Hydroxypropyl-beta-cyclodextrin (HP-βCyD) on oral drug absorption of the BCS class II drugs Danazol (DNZ) and Albendazole (ABZ) was evaluated. In vitro permeation of solutions and suspension systems was compared with their in vivo intestinal absorption in rats and their in vitro-in vivo correlation assessed. In solutions excess amounts of HP-βCyD decreased both in vitro permeation and in vivo absorption due to the decrease in free drug concentration, as expected. However, in suspension systems the contribution of HP-βCyD by drug complexation was found to be altered by further rate limiting steps for membrane permeation and intestinal absorption of each drug. In vitro permeation of DNZ was rate-limited by the diffusion into the unstirred water layer (UWL), while that of ABZ was rate-limited by the permeation across the lipid membrane. For the in vivo intestinal absorption, both drugs were rate-limited by the dissolution rate from undissolved drug. These differences in the rate-limiting process were considered to cause discrepancies in the result of in vitro and in vivo assays. In conclusion, it is quite important to understand the rate limiting process of oral absorption of the target drug for designing oral liquid formulations containing cyclodextrins.

Drug-Induced Dynamics of Bile Colloids

Bile colloids containing taurocholate and lecithin are essential for the solubilization of hydrophobic molecules including poorly water-soluble drugs such as Perphenazine. We detail the impact of Perphenazine concentrations on taurocholate/lecithin colloids using analytical ultracentrifugation, dynamic light scattering, small-angle neutron scattering, nuclear magnetic resonance spectroscopy, coarse-grained molecular dynamics simulations, and isothermal titration calorimetry. Perphenazine impacted colloidal molecular arrangement, structure, and binding thermodynamics in a concentration-dependent manner. At low concentration, Perphenazine was integrated into stable and large taurocholate/lecithin colloids and close to lecithin. Integration of Perphenazine into these colloids was exothermic. At higher Perphenazine concentration, the taurocholate/lecithin colloids had an approximately 5-fold reduction in apparent hydrodynamic size, heat release was less exothermic upon drug integration into the colloids, and Perphenazine interacted with both lecithin and taurocholate. In addition, Perphenazine induced a morphological transition from vesicles to wormlike micelles as indicated by neutron scattering. Despite these surprising colloidal dynamics, these natural colloids successfully ensured stable relative amounts of free Perphenazine throughout the entire drug concentration range tested here. Future studies are required to further detail these findings both on a molecular structural basis and in terms of in vivo relevance.

Leveraging bile solubilization of poorly water-soluble drugs by rational polymer selection

Poorly water-soluble drugs frequently solubilize into bile colloids and this natural mechanism is key for efficient bioavailability. We tested the impact of pharmaceutical polymers on this solubilization interplay using proton nuclear magnetic resonance spectroscopy, dynamic light scattering, and by assessing the flux across model membranes. Eudragit E, Soluplus, and a therapeutically used model polymer, Colesevelam, impacted the bile-colloidal geometry and molecular interaction. These polymer-induced changes reduced the flux of poorly water-soluble and bile interacting drugs (Perphenazine, Imatinib) but did not impact the flux of bile non-interacting Metoprolol. Non-bile interacting polymers (Kollidon VA 64, HPMC-AS) neither impacted the flux of colloid-interacting nor colloid-non-interacting drugs. These insights into the drug substance/polymer/bile colloid interplay potentially point towards a practical optimization parameter steering formulations to efficient bile-solubilization by rational polymer selection.

Use of Physiologically Based Pharmacokinetic (PBPK) Modeling for Predicting Drug-Food Interactions: an Industry Perspective

The effect of food on pharmacokinetic properties of drugs is a commonly observed occurrence affecting about 40% of orally administered drugs. Within the pharmaceutical industry, significant resources are invested to predict and characterize a clinically relevant food effect. Here, the predictive performance of physiologically based pharmacokinetic (PBPK) food effect models was assessed via de novo mechanistic absorption models for 30 compounds using controlled, pre-defined in vitro, and modeling methodology. Compounds for which absorption was known to be limited by intestinal transporters were excluded in this analysis. A decision tree for model verification and optimization was followed, leading to high, moderate, or low food effect prediction confidence. High (within 0.8- to 1.25-fold) to moderate confidence (within 0.5- to 2-fold) was achieved for most of the compounds (15 and 8, respectively). While for 7 compounds, prediction confidence was found to be low (> 2-fold). There was no clear difference in prediction success for positive or negative food effects and no clear relationship to the BCS category of tested drug molecules. However, an association could be demonstrated when the food effect was mainly related to changes in the gastrointestinal luminal fluids or physiology, including fluid volume, motility, pH, micellar entrapment, and bile salts. Considering these findings, it is recommended that appropriately verified mechanistic PBPK modeling can be leveraged with high to moderate confidence as a key approach to predicting potential food effect, especially related to mechanisms highlighted here.

Prediction of negative food effect induced by bile micelle binding on oral absorption of hydrophilic cationic drugs

The purpose of the present study was to quantitatively predict the negative food effect induced by bile micelle binding on the oral absorption of hydrophilic cationic drugs. The intrinsic membrane permeability and bile micelle unbound fraction of 12 model drugs (7 tertiary amines, 3 quaternary ammoniums, and 2 neutral drugs) were calculated from the experimental Caco-2 permeability data (P_app) under fasted and fed conditions. From these input data, the fraction of a dose absorbed (Fa) was predicted using the gastrointestinal unified theoretical framework, a mechanism-based oral absorption model. The predicted Fa ratio (fed/fasted) was then compared with the in vivo fed/fasted area under the plasma concentration-time curve ratio (AUCr). The AUCr values of tertiary amines and neutral drugs were appropriately predicted (absolute average fold error (AAFE) = 1.19), whereas those of quaternary ammoniums were markedly underestimated (AAFE = 4.70). The P_app ratio (fed/fasted) predicted AUCr less quantitatively (AAFE = 1.30 for tertiary amines and neutral drugs). The results of the present study would lead to a better understanding of negative food effect on oral drug absorption.

A Physiologically Based Pharmacokinetic Model of Vismodegib: Deconvoluting the Impact of Saturable Plasma Protein Binding, pH-Dependent Solubility and Nonsink Permeation

Vismodegib displays unique pharmacokinetic characteristics including saturable plasma protein binding to alpha-1 acid glycoprotein (AAG) and apparent time-dependent bioavailability leading to non-linear PK with dose and time, significantly faster time to steady-state and lower than predicted accumulation. Given these unique characteristics, a PBPK model was developed to explore mechanistic insights into saturable protein binding and complex oral absorption processes and de-convolute the impact of these independent non-linear processes on vismodegib exposure. Simcyp V18 was used for model development; oral absorption was characterized using the multi-layer gut wall (M-ADAM) model and mechanistic permeability model, incorporating transport across an unstirred boundary layer (UBL) between the luminal fluid and enterocyte in each segment of the gastrointestinal tract. PBPK simulations were compared with observed PK data from clinical trials in oncology patients and healthy subjects. Saturation of vismodegib protein binding to AAG led to substantially lower total drug accumulation, time to steady-state, and Css_total. For free exposure, Css_free and accumulation were unchanged, but time to steady-state was substantially reduced. Vismodegib oral absorption declined with both dose and dosing frequency; the concentration gradient driving vismodegib oral absorption declined with multiple doses, leading to a 32% decrease in vismodegib f_a from first dose to steady-state. Fed simulations suggested that increased solubility and dissolution are partially offset by reduced permeability across the UBL due to slower diffusion of micelle-bound drug. This work demonstrates the value of PBPK modeling to simultaneously capture and de-convolute multi-faceted absorption and disposition processes and provide mechanistic insights for compounds with complex pharmacokinetics.

Mifepristone polymorph with enhanced solubility, dissolution and oral bioavailability

Mifepristone is one of potent anti-progesterone agents, which binds to progesterone receptors and glucocorticoid receptors. Until now, there are a lot of research focusing on enhancing the solubility and oral bioavailability of Mifepristone. However, poor solubility and oral bioavailability has some undesirable consequences. In this work, Mifepristone in form D was discovered for the first time and characterized by PXRD, TGA, DSC, FT-IR, SEM and SS NMR. Form D was a metastable crystal type which manifested favorable stability under ambient conditions. Form D had better dissolution characteristic compared with commercial Mifepristone in 0.5% SDS solution. In addition, Mifepristone in form D exhibited a 1.43-fold higher peak plasma concentration (C_max) and 1.46-fold higher area under the curve (AUC) in rats. The work in this paper is a complement to the present understanding of drug polymorphism on the in vitro and in vivo behavior, and establishes the ground work for future development of Mifepristone in form D as a promising drug for the market.

Prediction Characteristics of Oral Absorption Simulation Software Evaluated Using Structurally Diverse Low-Solubility Drugs

The purpose of the present study was to characterize current biopharmaceutics modeling and simulation software regarding the prediction of the fraction of a dose absorbed (Fa) in humans. As commercial software products, GastroPlus™ and Simcyp® were used. In addition, the gastrointestinal unified theoretical framework, a simple and publicly accessible model, was used as a benchmark. The Fa prediction characteristics for a total of 96 clinical Fa data of 27 model drugs were systematically evaluated using the default settings of each software product. The molecular weight, dissociation constant, octanol-water partition coefficient, solubility in biorelevant media, dose, and particle size of model drugs were used as input data. Although the same input parameters were used, GastroPlus™, Simcyp®, and the gastrointestinal unified theoretical framework showed different Fa prediction characteristics depending on the rate-limiting steps of oral drug absorption. The results of the present study would be of great help for the overall progression of physiologically based absorption models.

Simultaneous Evaluation of Dissolution and Permeation of Oral Drug Solid Formulations for Predicting Absorption Rate-Limiting Factors and In Vitro-In Vivo Correlations: Case Study Using a Poorly Soluble Weakly Basic Drug

Combined dissolution and permeation systems are designed to simultaneously assess the dissolution of a pharmaceutical dosage form and the permeation of dissolved drugs therefrom. However, there were still some limitations on predicting the possible absorption rate-limiting steps and improving the in vitro-in vivo correlation (IVIVC) of a complete dosage form. In this study, the modified biorelevant media with some solubilizers and pH modifiers were integrated into the drug dissolution/absorption simulating system (DDASS). Indapamide, a poorly soluble compound (pKa = 8.8), was selected to validate the applicability of the modified biorelevant media. The elution and permeation dynamics of indapamide were investigated by using appropriate solubilizing agents in the DDASS. The absorption behaviors were analyzed after oral administration of indapamide in beagle dogs. The absorption rate-limiting steps and IVIVCs were predicted from the dissolution-permeation-absorption dynamic parameters. As a result, the absorption fraction of indapamide in the FaSSIF_mod of DDASS was estimated to be approximately 100%, in accordance with its high permeability. The ratios of permeation rate to elution rate were 2.55 and 3.34 for the immediate- and sustained-release tablets of indapamide, respectively, suggesting a dissolution rate-limiting absorption for indapamine. In addition, point-to-point correlations were established between in vitro elution and in vivo absorption by the nonlinear and linear regression analysis ways (r > 0.85). The findings indicate that DDASS is a promising technique to develop improved IVIVCs of a complete dosage form, and the FaSSIF_mod is suitable to predict the possible absorption rate-limiting steps of poorly soluble drugs in DDASS.

Drug supersaturation during formulation digestion, including real-time analytical approaches

Self-emulsifying and other lipid-based drug delivery systems have drawn considerable interest from pharmaceutical scientists for managing oral delivery of poorly water-soluble compounds. Following administration, self-emulsifying systems exhibit complex aqueous dispersion and digestion in the gastro-intestinal tract. These processes generally result in drug supersaturation, which leads to enhanced absorption or the high drug concentrations may cause precipitation with erratic and variable oral bioavailability. This review briefly outlines drug supersaturation obtained from self-emulsifying and other lipid-based formulations; recent advancements of in vitro lipolysis testing are also discussed. Further, a main focus is mechanisms by which supersaturation is triggered from gastro-intestinal processes, as well as analytical techniques that are promising from a research and development perspective. Comparatively simple approaches are presented together with more sophisticated process analytics to enable direct examination of kinetic changes. The analytical methods together with their sensor probes are discussed in detail to clarify opportunities as well as technical limitations. Some of the more sophisticated methods, including those based on synchrotron radiation, are primarily research oriented despite interesting experimental findings from an industrial viewpoint. The availability of kinetic data further opens the door to mathematical modeling of supersaturation and precipitation versus permeation, which lays the groundwork for better in vitro to in vivo correlations as well as for physiologically-based modeling of lipid-based systems.

Preparation and Characterization of Novel Pharmaceutical Co-Crystals: Ticagrelor with Nicotinamide

Two new co-crystals, Ticagrelor with Nicotinamide, have been prepared with improved solubility. Because Ticalegor has a poor solubility and dissolution rate, a novel co-crystallization method with structurally homogenous crystalline material, an active pharmaceutical ingredient (API), and co-former indefinite stoichiometric amount has been made to improve Ticagrelor’s solubility. The co-crystal of Ticagrelor (TICA) with Nicotinamide (NCA) was prepared in ratio (1:1) and confirmed by FTIR, DSC, and XRD characterization. Furthermore, the single crystal structure of TICA-NCA hydrate was analyzed. The solubility of co-crystals was investigated in pH 2 acidic medium, which was a significant improvement as compared to the solubility of a free drug. The in vitro dissolution rate of co-crystal was larger than that of the commercial product.

Food for thought: formulating away the food effect - a PEARRL review

OBJECTIVES

Co-ingestion of oral dosage forms with meals can cause substantial changes in bioavailability relative to the fasted state. Food-mediated effects on bioavailability can have significant consequences in drug development, regulatory and clinical settings. To date, the primary focus of research has focused on the ability to mechanistically understand the causes and predict the occurrence of these effects.

KEY FINDINGS

The current review describes the mechanisms underpinning the occurrence of food effects, sheds new insights on the relative frequency for newly licensed medicines and describes the various methods by which they can be overcome. Analysis of oral medicines licensed by either the EMA or FDA since 2010 revealed that over 40% display significant food effects. Due to altered bioavailability, these medicines are often required to be dosed, rather restrictively, in either the fed or the fasted state, which can hinder clinical usefulness.

SUMMARY

There are clinical and commercial advantages to predicting the presence of food effects early in the drug development process, in order to mitigate this risk of variable food effect bioavailability. Formulation approaches aimed at reducing variable food-dependent bioavailability, through the use of bio-enabling formulations, are an essential tool in addressing this challenge and the latest state of the art in this field are summarised here.

Food Effect Projections via Physiologically Based Pharmacokinetic Modeling: Predictive Case Studies

Food can alter the absorption of orally administered drugs. Biopharmaceutics physiologically based pharmacokinetic (PBPK) modeling offers the possibility to simulate a compound's pharmacokinetics under fasted or fed states. To advance the utility of PBPK modeling, with a view to regulatory impact, we have pooled our experience across 4 pharmaceutical companies to propose a general multistep PBPK workflow leveraging pre-existing clinical data for immediate-release formulations of Biopharmaceutics Classification System I and II compounds. With this strategy, we wish to promote pragmatic PBPK approaches for compounds where absorption is well understood, that is, compounds with moderate-to-high permeability that are not substrates for uptake transporters. Five case studies demonstrate how food effect can be well predicted using appropriately established and validated models. The case studies integrate solubility and dissolution data for initial model development and apply a "middle-out" validation with clinical data in one prandial state. Then, whenever possible, a validation against both fasted and fed state data is recommended before application of the models prospectively for to-be-marketed formulations. Thus, when combined with limited clinical data, PBPK models could be used to simulate outcomes for new doses, formulations, or active pharmaceutical ingredient forms, in lieu of a clinical food-effect study.

The Solubility-Permeability Trade-Off of Progesterone With Cyclodextrins Under Physiological Conditions: Experimental Observations and Computer Simulations

This study intended to evaluate the effect of cyclodextrins on the apparent solubility and permeability of lipophilic drugs under physiological conditions and establish in silico model to choose the optimal amount of cyclodextrins for cyclodextrin-containing oral formulations. In order to study the effect of cyclodextrins under physiological conditions, bile salts and lecithin were added into the rat intestinal perfusion solution to simulate the fasted intestinal fluid. In addition, the in vivo oral absorption performances of cyclodextrin-containing formulations were simulated by gastrointestinal simulation technology based on the advanced compartmental absorption and transit model. The permeability of progesterone was not significantly different between 0.1 mM and 1 mM of 2-hydroxypropyl-β-cyclodextrins (HP-β-CD) under physiological conditions. When the concentration of HP-β-CD was 1 mM, the permeability of progesterone under physiological conditions was significantly higher than that in vitro. The in silico model established in this study was validated by in vivo studies of 4 formulations containing different dosage of cyclodextrin, proving that it was accurate and reliable. In conclusion, this work that demonstrates the permeability of lipophilic drugs could not decrease quickly among a certain range of dosage of HP-β-CD in vivo. Studying the solubility-permeability interplay under physiological conditions would be more meaningful.

Physiologically Based Oral Absorption Modelling to Study Gut-Level Drug Interactions

Physiologically based oral absorption models are in silico tools primarily used to guide formulation development and project the clinical performance of formulation variants. This commentary briefly discusses additional oral absorption model applications, focusing on gut-level drug interactions. Gut-level drug interactions can involve drug degradation, metabolic enzymes, transporters, gastrointestinal motility modulators, acid-reducing agents, and food. The growth in publications reporting physiologically based oral absorption model utilization and successful pharmacokinetic prediction (e.g., after acid-reducing agents or food coadministration) indicate that oral absorption models have achieved a level of maturity within the industry particularly over the past 15 years. Provided appropriate data and model validation, oral absorption modeling/simulation may serve as a surrogate for clinical studies by providing both mechanistic and quantitative understanding of oral delivery considerations on pharmacokinetics.

Pharmacokinetics and Tolerability of Rufinamide Following Single and Multiple Oral Doses and Effect of Food on Pharmacokinetics in Healthy Chinese Subjects

BACKGROUND

Rufinamide is a triazole derivative that is structurally unrelated to currently marketed antiepileptic medications for add-on treatment of seizures in the setting of Lennox-Gastaut syndrome in patients from the age of 4 years.

OBJECTIVE

The purpose of this study was to determine the pharmacokinetic and safety profile of single and multiple doses of rufinamide in healthy Chinese subjects. The effects of food and gender on the pharmacokinetic properties of rufinamide were also evaluated.

METHODS

In the single-dose study, volunteers were randomly assigned to 4 dose groups and received a single dose of 200, 400, 800, 1200 mg rufinamide tablets under fasting condition. Ten subjects in the 200-mg dose group were randomly assigned to either a high-fat or non-high-fat breakfast group in each study period. The drug administration was separated by a washout period of 7 calendar days. In the multiple-dose study, 10 subjects were administered on an empty stomach rufinamide 200 mg twice daily for 6 consecutive days. Liquid chromatography tandem mass spectrometry (LC-MS/MS) method was applied to determine plasma concentration of rufinamide. Pharmacokinetic parameters, including the maximum plasma concentration (C max), the time to peak concentration (t max), the area under the plasma concentration versus time curve from time 0 to the last measurable concentration (AUC0-t ) and from time 0 to infinity (AUC0-∞), terminal elimination half-life (t 1/2), apparent volume of distribution (V d), apparent clearance (CL), average residence time (MRT), area under the plasma concentration versus time curve from time 0 to the last measurable concentration at steady state (AUCss), peak concentration (C max,ss) and trough level concentration (C min,ss) at steady state were calculated using non-compartmental models. Tolerability was assessed based on investigator inquiries, spontaneous reports and clinical evaluations.

RESULTS

Rufinamide displayed a dose-dependent, but sub-proportional increase in exposure following single-dose and repeated dose administration. After administration of single dose of 200, 400, 800 and 1200 mg, without food, the rufinamide mean C max (standard deviation, SD) was 1806.5 (526.4), 2490 (564.8), 3719 (976.1) and 4166 (1187.1) μg/L, respectively. Mean AUC0-t (SD) was 34,571 (9484), 56,246 (18,077), 89,022 (23,379) and 107,316 (34,766) μg·h/L, respectively. While in fed condition at the dosage of 200 mg, mean C max (SD) and mean AUC0-t (SD) were 2363 (582) μg/L and 40,593 (10,516) μg·h/L, respectively. After administration of multiple doses, arithmetic mean (SD) values of C max and AUC0-t were 3566 (873) μg/L and 62,803 (19,873) μg·h/L, respectively. The steady state was achieved by day 3 of multiple dosing after 2 daily doses (twice a day), the corresponding accumulation factor (AUCss/AUC0-t) was 0.9057. Although there were no substantial effects on exposure resulting from gender differences, a notable food effect was observed, with AUC and C max increased by 17.4 and 30.8 %, respectively. Single- and multiple-dose phases were generally safe and well tolerated.

CONCLUSION

Overall, 15 % (6/40) of subjects experienced a mild indisposition with no serious adverse events. On single and multiple dosing, rufinamide exhibited nonlinear pharmacokinetics and was well tolerated in healthy Chinese subjects.

Pharmacokinetics, Distribution, Metabolism, and Excretion of Omadacycline following a Single Intravenous or Oral Dose of 14C-Omadacycline in Rats

The absorption, distribution, metabolism, and excretion (ADME) of omadacycline, a first-in-class aminomethylcycline antibiotic with a broad spectrum of activity against Gram-positive, Gram-negative, anaerobic, and atypical bacteria, were evaluated in rats. Tissue distribution was investigated by quantitative whole-body autoradiography in male Long-Evans Hooded (LEH) rats. Following an intravenous (i.v.) dose of 5 mg/kg of body weight, radioactivity widely and rapidly distributed into most tissues. The highest tissue-to-blood concentration ratios (t/b) were observed in bone mineral, thyroid gland, and Harderian gland at 24 h post-i.v. dose. There was no evidence of stable accumulation in uveal tract tissue, suggesting the absence of a stable binding interaction with melanin. Following a 90 mg/kg oral dose in LEH rats, the highest t/b were observed in bone mineral, Harderian gland, liver, spleen, and salivary gland. The plasma protein binding levels were 26% in the rat and 15% to 21% in other species. Omadacycline plasma clearance was 1.2 liters/h/kg, and its half-life was 4.6 h; the steady-state volume of distribution (Vss) was 6.89 liters/kg. Major circulating components in plasma were intact omadacycline and its epimer. Consistent with observations in human, approximately 80% of the dose was excreted into the feces as unchanged omadacycline after i.v. administration. Fecal excretion was primarily the result of biliary excretion (∼40%) and direct gastrointestinal secretion (∼30%). However, urinary excretion (∼30%) was equally prominent after i.v. dosing.

Food Effect in Humans: Predicting the Risk Through In Vitro Dissolution and In Vivo Pharmacokinetic Models

In vitro and in vivo experimental models are frequently used to assess a new chemical entity's (NCE) biopharmaceutical performance risk for food effect (FE) in humans. Their ability to predict human FE hinges on replicating key features of clinical FE studies and building an in vitro-in vivo relationship (IVIVR). In this study, 22 compounds that span a wide range of physicochemical properties, Biopharmaceutics Classification System (BCS) classes, and food sensitivity were evaluated for biorelevant dissolution in fasted- and fed-state intestinal media and the dog fed/fasted-state pharmacokinetic model. Using the area under the curve (AUC) as a performance measure, the ratio of the fed-to-fasted AUC (FE ratio) was used to correlate each experimental model to FE ratio in humans. A linear correlation was observed for the in vitro dissolution-human IVIVR (R (2) = 0.66, % mean square error 20.7%). Similarly, the dog FE ratio correlated linearly with the FE ratio in humans (R (2) = 0.74, % mean square error 16.25%) for 15 compounds. Data points near the correlation line indicate dissolution-driven mechanism for food effect, while deviations from the correlation line shed light on unique mechanisms that can come into play such as GI physiology or unusual physicochemical properties. In summary, fed/fasted dissolution studies and dog PK studies show a reasonable correlation to human FE, hence are useful tools to flag high-risk NCEs entering clinical development. Combining kinetic dissolution, dog FE model and in silico modeling one can study FE mechanism and formulation strategies to mitigate the FE risk.

Physicochemical and crystal structure analysis of pranlukast pseudo-polymorphs II: Solvate and cocrystal

Pranlukast (PRS) is a leukotriene receptor antagonist for the treatment of bronchial asthma. In this study, six new solvates and one new cocrystal of PRS were characterized by PXRD, TG-DTA, DSC, vapor sorption analysis and the dissolution test. In addition, the crystal structures were determined by single crystal X-ray structure analysis. PRS was found to be a rare example of a promiscuous multicomponent crystal former. The crystal packing patterns of these crystals can be categorized into the sheet-like and channel-like patterns. The ethanol solvate (PRS/ethanol) and urea cocrystal (PRS/urea) were more stable than the others under humid conditions. PRS/ethanol showed an improved dissolution profile compared to PRS HH and PRS/urea.

Physicochemical and crystal structure analysis of pranlukast pseudo-polymorphs I: anhydrates and hydrate

Pranlukast (PRS) is a leukotriene receptor antagonist for the treatment of bronchial asthma. Pranlukast is formulated as a hemihydrate (HH) form in the drug product. Here, we report three new anhydrate forms of PRS (AH, form I-III). These polymorphs and PRS HH were characterized by PXRD, TG-DTA, simultaneous PXRD-DSC and vapor sorption analysis. In addition, the crystal structures of HH and AH-I were determined by single crystal X-ray structure analysis for the first time. HH transformed to AH-I, AH-II and AH-III as the temperature was increased from 25°C to 210°C. At 25°C, AH-I transformed to HH at above 5%RH. HH and AH-I possessed similar crystal packing patterns and molecular structures.

First-in-humans study of the safety, tolerability, and pharmacokinetics of ACT-451840, a new chemical entity with antimalarial activity

Emerging resistance to antimalarial agents raises the need for new drugs. ACT-451840 is a new compound with potent activity against sensitive and resistant Plasmodium falciparum strains. This was a first-in-humans single-ascending-dose study to investigate the safety, tolerability, and pharmacokinetics of ACT-451840 across doses of 10, 50, 200, and 500 mg in healthy male subjects. In the 200- and 500-mg dose groups, the effect of food was investigated, and antimalarial activity was assessed using an ex vivo bioassay with P. falciparum. No (serious) adverse events leading to discontinuation were reported. At the highest dose level, the peak drug concentration (Cmax) and the area under the plasma concentration-time curve from zero to infinity of ACT-451840 under fasted conditions reached 11.9 ng/ml and 100.6 ng·h/ml, respectively, and these were approximately 13-fold higher under fed conditions. Food did not affect the half-life (approximately 34 h) of the drug, while the Cmax was attained 2.0 and 3.5 h postdose under fasted and fed conditions, respectively. The plasma concentrations estimated by the bioassay were approximately 4-fold higher than those measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Several potentially active metabolites were also identified. ACT-451840 was well tolerated across all doses. Exposure to ACT-451840 significantly increased with food. The bioassay indicated the presence of circulating active metabolites. (This study has been registered at ClinicalTrials.gov under registration no. NCT02186002.).