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

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

Fasted and fed state human duodenal fluids: Characterization, drug solubility, and comparison to simulated fluids and with human bioavailability

Accurate in vivo predictions of intestinal absorption of low solubility drugs require knowing their solubility in physiologically relevant dissolution media. Aspirated human intestinal fluids (HIF) are the gold standard, followed by simulated intestinal HIF in the fasted and fed state (FaSSIF/FeSSIF). However, current HIF characterization data vary, and there is also some controversy regarding the accuracy of FaSSIF and FeSSIF for predicting drug solubility in HIF. This study aimed at characterizing fasted and fed state duodenal HIF from 16 human volunteers with respect to pH, buffer capacity, osmolarity, surface tension, as well as protein, phospholipid, and bile salt content. The fasted and fed state HIF samples were further used to investigate the equilibrium solubility of 17 representative low-solubility small-molecule drugs, six of which were confidential industry compounds and 11 were known and characterized regarding chemical diversity. These solubility values were then compared to reported solubility values in fasted and fed state HIF, FaSSIF and FeSSIF, as well as with their human bioavailability for both states. The HIF compositions corresponded well to previously reported values and current FaSSIF and FeSSIF compositions. The drug solubility values in HIF (both fasted and fed states) were also well in line with reported solubility data for HIF, as well as simulated FaSSIF and FeSSIF. This indicates that the in vivo conditions in the proximal small intestine are well represented by simulated intestinal fluids in both composition and drug equilibrium solubility. However, increased drug solubility in the fed vs. fasted states in HIF did not correlate with the human bioavailability changes of the same drugs following oral administration in either state.

Biliary Excretion-Mediated Food Effects and Prediction

Many orally administered drugs with negative food effects (i.e., lower exposure under fed conditions) are often primarily or partially eliminated by biliary excretion. The aim of this study is to assess the potential correlation between a negative food effect and biliary excretion. Correlation analysis was conducted using a training dataset containing 27 drugs which met the following criteria: (1) immediate-release formulations, (2) shows a negative food effect, (3) > 10% biliary clearance, and (4) does not undergo extensive metabolism. A correlation between fed-state biliary clearance (CL_b,fed) and fasted-state biliary clearance (CL_b,fast) (y = 1.81*x, R² = 0.68) was observed. The 1.8-fold increase in biliary clearance was then used as a correction factor to improve physiologically based pharmacokinetic (PBPK) prediction of food effects for 12 test drugs. The mean deviations of predicted fed/fasting AUC ratio and C_max ratio from clinically observed values were reduced from 32.4 to 17.2% and from 63.3 to 54.3%, respectively. In contrast to the positive food effects on most biopharmaceutics classification system (BCS) class II drugs for which food-stimulated bile flow increases drug solubility and absorption, our results suggest that the elimination of biliary excreted drugs is increased by food-stimulated bile flow, resulting in negative food effects.

In Vitro Digestion for Control and Monitoring of Food Effects in Relation to Micellarization Index of Carotenoids

The multifactorial system that influences the availability of macronutrients, micronutrients, and phytoconstituents with relevant bioactivities has been assessed by in vitro digestion protocols, which have become an effective technique to support the health-through-food strategy. The measurement of the significance of food structure, food matrix, synergies and competitive effects, processing features, and even some physiological issues has created valuable scientific and technological information, and the development of harmonized protocols. Now it is possible to make further advances by applying this knowledge to obtain data regarding the potential availability of target compound(s) in the food source within a standard meal context. This protocol describes the measurement of the micellarization index of carotenoids from dietary rich sources with test meals accounting the effects of high vs. low fat and normo-, hypo-, and hypercaloric content.

Relationship between the effects of food on the pharmacokinetics of oral antineoplastic drugs and their physicochemical properties

Background

Food is known to affect drug absorption by delaying gastric emptying time, altering gastrointestinal pH, stimulating bile flow, increasing splanchnic blood flow, or physically interacting with drugs. Although food is known to affect the pharmacokinetics of oral antineoplastic drugs, the relationship between the effects of food and the physicochemical properties of drugs remains unclear.

Methods

In this study, we surveyed the literature on three kinds of pharmacokinetic changes, AUC ratio, C_max ratio and T_max ratio, in the fasted and fed state for 72 oral antineoplastic drugs that were listed on the drug price standard in May 2018 in Japan. We further predicted the physicochemical properties from the 2D chemical structure of the antineoplastic drugs using in silico predictions.

Results

As a result of analyzing the relationship between the effects of food and physicochemical properties, we found that compounds that show increased absorption in the fed state had higher logP and lower solubility in fasted-state simulated intestinal fluid (FaSSIF). However, compounds with delayed absorption had higher solubility in FaSSIF. Furthermore, as a result of decision tree analysis, it was classified as AUC increase with logP ≥4.34. We found that an AUC increase in the fed state did not occur with compounds with low lipid solubilities (logP < 1.59). From these results, it is predicted that 7 compounds out of the 24 compounds for which the effects of food are unknown are at risk for increased absorption in the fed state and that no increase in absorption would occur in 13 compounds.

Conclusion

In this study, we found that drugs that will show increased absorption in the fed state and drugs for which absorption is not dependent on food can generally be predicted by logP. These results suggest that logP can be a useful parameter for predicting the effects of food on drug absorption.

The impact of gastric pH, volume, and emptying on the food effect of ziprasidone oral absorption

In a recent food effect clinical study, the authors concluded that a meal consisting of ≥500 kcal, regardless of fat content, produced the maximal bioavailability for ziprasidone. Using GastroPlus™, a commercially available pharmacokinetic simulation software, a semiphysiological model-a kind of physiologically based pharmacokinetic (PBPK) absorption model-was developed that could predict the concentration-time profiles when ziprasidone was administered with any one of the five test meals or fasting. Ziprasidone intravenous pharmacokinetics and oral absorption permeability were determined from clinical studies following the intravenous and duodenal infusion of ziprasidone to volunteers. From the detailed dietary information of each meal provided in the previously published food effect study, the stomach pH, volume, and gastric emptying could be predicted. Incorporating these meal-specific parameters into the model improved the predictions beyond the default fed/fasted parameters commonly used in the software. Compared to the default models, the improved models resulted in an improved prediction of the average ziprasidone concentration-time profile for each meal. Using this type of semiphysiological absorption model, we have shown that the dietary contents of the meals should be taken into account to predict food effects for ziprasidone and perhaps other BCS class I or II compounds.

Mechanistic prediction of food effects for Compound A tablet using PBPK model

Physiologically based pharmacokinetic (PBPK) modeling has been extensively used to study the factors of effect drug absorption, distribution, metabolize and extraction progress in human. In this study, Compound A(CPD A) is a BCS Class II drug, which has been extensive applied in clinical as lipid-lowering drug, administered orally after food, they displayed positive food effects in human, A PBPK model was built to mechanistic investigate the food effect of CPD A tablet in our study. By using gastroplus™ software, the PBPK models accurately predicted the results of food effects and predicted data were within 2-fold error of the observed results. The PBPK model mechanistic illuminated the changes of pharmacokinetic values for the positive food effects of the compound in human. Here in, the PBPK modeling which were combined with ACAT absorption models in it, successfully simulated the food effect in human of the drug. The simulation results were proved that PBPK model can be able to serve as a potential tool to predict the food effect on certain oral drugs.

Trospium chloride is absorbed from two intestinal "absorption windows" with different permeability in healthy subjects

Intestinal P-glycoprotein is regio-selectively expressed and is a high affinity, low capacity efflux carrier for the cationic, poorly permeable trospium. Organic cation transporter 1 (OCT1) provides lower affinity but higher capacity for trospium uptake. To evaluate regional intestinal permeability, absorption profiles after gastric infusion of trospium chloride (30mg/250ml=[I]₂) for 6h and after swallowing 30mg immediate-release tablets in fasted and fed healthy subjects, were evaluated using an inverse Gaussian density function to model input rate and mean absorption time (MAT). Trospium chloride was slowly absorbed (MAT ∼10h) after gastric infusion involving two processes with different input rates, peaking at about 3h and 7h. Input rates and MAT were influenced by dosage form and meal. In conclusion, trospium is absorbed from two "windows" located in the jejunum and cecum/ascending colon, whose uptake capacity might result from local abundance and functional interplay of P-glycoprotein and OCT1.

Can dosage form-dependent food effects be predicted using biorelevant dissolution tests? Case example extended release nifedipine

AIMS

Food intake is known to have various effects on gastrointestinal luminal conditions in terms of transit times, hydrodynamic forces and/or luminal fluid composition and can therefore affect the dissolution behavior of solid oral dosage forms. The aim of this study was to investigate and detect the dosage form-dependent food effect that has been observed for two extended-release formulations of nifedipine using in vitro dissolution tests.

METHODS

Two monolithic extended release formulations, the osmotic pump Adalat® XL 60mg and matrix-type Adalat® Eins 30mg formulation, were investigated with biorelevant dissolution methods using the USP apparatus III and IV under both simulated prandial states, and their corresponding quality control dissolution method. In vitro data were compared to published and unpublished in vivo data using deconvolution-based in vitro - in vivo correlation (IVIVC) approaches.

RESULTS

Quality control dissolution methods tended to overestimate the dissolution rate due to the excessive solubilizing capabilities of the sodium dodecyl sulfate (SDS)-containing dissolution media. Using Level II biorelevant media the dosage form dependent food effect for nifedipine was described well when studied with the USP apparatus III, whereas the USP apparatus IV failed to detect the positive food effect for the matrix-type dosage form.

CONCLUSIONS

It was demonstrated that biorelevant methods can serve as a useful tool during formulation development as they were able to qualitatively reflect the in vivo data.

Supersaturation of zafirlukast in fasted and fed state intestinal media with and without precipitation inhibitors

Poor water solubility is a bottle neck in the development of many new drug candidates, and understanding and circumventing this is essential for a more effective drug development. Zafirlukast (ZA) is a leukotriene antagonist marketed for the treatment of asthma (Accolate®). ZA is poorly water soluble, and is formulated in an amorphous form (aZA) to improve its solubility and oral bioavailability. It has been shown that upon dissolution of aZa, the concentration of ZA in solution is supersaturated with respect to its stable crystalline form (ZA monohydrate), and thus, in theory, the bioavailability increases upon amorphization of ZA. The polymers hydroxypropylmethylcellulose (HPMC) and polyvinylpyrrolidone (PVP), often used as stabilizers of the supersaturated state, are in the excipient list of Accolate®. It is not recommended to take Accolate® with food, as this reduces the bioavailability by 40%. The aim of this study was to investigate the effect of simulated fasted and fed state intestinal media as well as the effect of HPMC and PVP on the supersaturation and precipitation of ZA in vitro. Supersaturation of aZA was studied in vitro in a small scale setup using the μDiss Profiler™. Several media were used for this study: One medium simulating the fasted state intestinal fluids and three media simulating different fed state intestinal fluids. Solid state changes of the drug were investigated by small angle x-ray scattering. The duration wherein aZA was maintained at a supersaturated state was prolonged in the presence of HPMC and lasted more than 20h in the presence of PVP in a fasted state intestinal medium. The presence of PVP increased the concentration of drug dissolved in the supersaturated state. The duration of supersaturation was shorter in fed than in a fasted state simulated intestinal media, but the concentration during supersaturation was higher. It was thus not possible to predict any positive or negative food effects from the dissolution/precipitation curves from different media. Lipolysis products in the fed state simulated media seemed to cause both a negative effect on the duration of supersaturation, and an increased drug concentration during supersaturation. In contrast, when testing the effect of a fed state simulated medium compared to the fasted state medium, in the presence of PVP, a clear negative effect was seen on the dissolution/precipitation curved of the fed state medium. The drug concentration during supersaturation was marginally different in the two media, but a precipitation of ZA was seen in the fed state medium, which was not observed in the fasted state medium. Solid state transformation from aZA to ZA monohydrate (mhZA) upon precipitation of the supersaturated solutions was confirmed by small angle x-ray scattering. All of these results can explain the described in vivo behavior of ZA. For ZA simple dissolution experiments in vitro can be used to examine supersaturation, effectiveness of PI and potential food effects on these.

In vitro biorelevant models for evaluating modified release mesalamine products to forecast the effect of formulation and meal intake on drug release

AIMS

Postprandial administration of solid oral dosage forms greatly changes the dissolution environment compared to fasted state administration. The aims of this study were to investigate and forecast the effect of co-administration of a meal on drug release for delayed and/or extended release mesalamine formulations as well as design of in vitro tests to distinguish among formulations in a biorelevant way.

METHODS

Five different mesalamine formulations (Asacol® 400 mg, Mezavant® 1200 mg, Pentasa® 500 mg and Salofalk® in the 250 mg and 500 mg strengths) were investigated with biorelevant dissolution methods using the USP apparatus III and USP apparatus IV (open loop mode) under both fasted and fed state conditions, as well as with the dissolution methods described in pharmacopeia for delayed and extended release mesalamine products.

RESULTS

Using the biorelevant experimental conditions proposed in this study, changes in release in the proximal gut due to meal intake are forecast to be minimal for Asacol®, Mezavant®, Pentasa® and Salofalk® 500 mg, while for Salofalk® 250 mg release was predicted to occur much earlier under fed state conditions. The USP apparatus III generally tended to result in faster dissolution rates and forecast more pronounced food effects for Salofalk® 250 mg than the USP apparatus IV. The biorelevant dissolution gradients were also able to reflect the in vivo behavior of the formulations.

CONCLUSIONS

In vitro biorelevant models can be useful in the comparison of the release behavior from different delayed and extended release mesalamine formulations as well as forecasting effects of concomitant meal intake on drug release.

Interaction between fed gastric media (Ensure Plus®) and different hypromellose based caffeine controlled release tablets: comparison and mechanistic study of caffeine release in fed and fasted media versus water using the USP dissolution apparatus 3

The aim of the study was to investigate caffeine release in fed and fasted state media from three controlled release matrix tablets containing different HPMC viscosity grades. The biorelevant in vitro dissolution methods utilize the USP 3 dissolution apparatus and biorelevant media to simulate fed and fasted gastro-intestinal dissolution conditions. The effect of tablet reciprocation rate (dip speed) in dissolution media (10 and 15 dips per minute) and media (water, fed and fasted) on caffeine release rate from - and erosion rate of - 100, 4000 and 15,000 mPa s HPMC viscosity tablets was investigated using factorial designed experiments. Furthermore, the mechanism of release in Ensure Plus(®), a nutrition drink similar in composition to the FDA standard meal, was investigated by studying tablet swelling using texture analysis. Altering dip speed has negligible effect on release and erosion rates. Using fasted media instead of water slightly decreases caffeine release from 100 and 4000 mPa s HPMC viscosity tablets as well as erosion rates, while 15,000 mPa s tablets remain unaffected. Fed compared to fasted media decreases caffeine release rate, and the food effect is greater for the 100 mPa s viscosity tablets compared to the 4000 and 15,000 mPa s viscosity tablets. The investigation using texture analysis indicates that Ensure Plus(®) becomes rate-limiting for caffeine release from HPMC tablets by forming a hydrophobic barrier around the tablets. The barrier decreases tablet water permeation, which decreases erosion rate in 100 mPa s viscosity tablets, swelling in 15,000 mPa s viscosity tablets and caffeine release from both tablets. This observed interaction between Ensure Plus(®) and the HPMC tablets may translate into decreased drug release rate in the fed stomach, which may decrease the amount of drug available for absorption in the small intestine and thus reduce systemic drug exposure and maximum plasma concentration.

Quantitative prediction of formulation-specific food effects and their population variability from in vitro data with the physiologically-based ADAM model: a case study using the BCS/BDDCS Class II drug nifedipine

Quantitative prediction of food effects (FE) upon drug pharmacokinetics, including population variability, in advance of human trials may help with trial design by optimising the number of subjects and sampling times when a clinical study is warranted or by negating the need for conduct of clinical studies. Classification and rule-based systems such as the BCS and BDDCS and statistical QSARs are widely used to anticipate the nature of FE in early drug development. However, their qualitative rather than quantitative nature makes them less appropriate for assessing the magnitude of FE. Moreover, these approaches are based upon drug properties alone and are not appropriate for estimating potential formulation-specific FE on modified or controlled release products. In contrast, physiologically-based mechanistic models can consider the scope and interplay of a range of physiological changes after food intake and, in combination with appropriate in vitro drug- and formulation-specific data, can make quantitative predictions of formulation-specific FE including the inter-individual variability of such effects. Herein the Advanced Dissolution, Absorption and Metabolism (ADAM) model is applied to the prediction of formulation-specific FE for BCS/BDDCS Class II drug and CYP3A4 substrate nifedipine using as far as possible only in vitro data. Predicted plasma concentration profiles of all three studied formulations under fasted and fed states are within 2-fold of clinically observed profiles. The % prediction error (%PE) in fed-to-fasted ratio of Cmax and AUC were less than 5% for all formulations except for the Cmax of Nifedicron (%PE=-29.6%). This successful case study should help to improve confidence in the use of mechanistic physiologically-based models coupled with in vitro data for the anticipation of FE in advance of in vivo studies. However, it is acknowledged that further studies with drugs/formulations exhibiting a wide range of properties are required to further validate this methodology.