Increasing the biorelevance of simulated intestinal fluids for better predictions of drug equilibrium solubility in the fasted upper small intestine

To date the importance of luminal species other than bile salts and phosphatidylcholine on drug equilibrium solubility in the fasted upper small intestine has been evaluated to a very limited extent. In this communication the importance of fatty acids, cholesterol, and proteins on solubility of four model lipophilic compounds was evaluated by including these components into previously proposed simulated intestinal fluids. Data were compared with ex vivo solubility data in aspirates reflecting the mean and the median luminal composition in the upper small intestine. It is concluded that estimation of solubility in aspirates reflecting the median luminal composition is better estimated when the presence of cholesterol and fatty acids is also simulated. In contrast, estimation of solubility in aspirates reflecting the mean luminal composition requires consideration of additional factors (e.g. buffer species identity, non-micellar colloidal structures, and lyso-phosphatidylcholine content)

Exploring the impact of Crohn’s disease on the intragastric environment of fasted adults

We explored the potential impact of Crohn’s disease on the intragastric environment of fasted adults with a view to potential effects on intragastric performance of orally administered drugs in the fasted state. Data were collected from 15 healthy individuals and 15 patients with Crohn’s disease. All subjects remained fasted for at least 12h prior to gastroscopy. Intragastric resting volume and pH were measured upon aspiration. Osmolality, surface tension, pepsin activity, and content of six bile acids were measured within 4 months upon sample collection. Unlike intragastric volumes, intragastric osmolality was significantly increased by Crohn’s disease. However, mean osmolality value in patients was only slightly higher than in healthy individuals (293 vs. 257 mOsmol/kg, respectively), therefore, unlikely to affect intragastric drug product performance. Primarily due to the high variability of data in healthy individuals, the potential effects on intragastric pH and surface activity could not be evaluated on a statistical basis. However, based on average (mean and median) values, even if they are statistically significant, it seems unlikely to be of clinical significance. Inter-subject variability of pepsin activity, and total bile acids content was high in both the healthy and the patients’ groups. Statistical investigation of the potential impact of Crohn’s disease on these parameters requires prior designation of the minimum differences to be detected; such differences will determine the minimum sample size required of relevant investigations

Evaluation of the impact of excipients and an albendazole salt on albendazole concentrations in upper small intestine using an in vitro biorelevant gastrointestinal transfer (BioGIT) system

An in vitro biorelevant gastrointestinal transfer (BioGIT) system was assessed for its ability to mimic recently reported albendazole concentrations in human upper small intestine after administration of free base suspensions to fasted adults in absence and in presence of supersaturation promoting excipients (hydroxypropylmethylcellulose and lipid self-emulsifying vehicles). The in vitro method was also used to evaluate the likely impact of using the sulfate salt on albendazole concentrations in upper small intestine. In addition, BioGIT data were compared with equilibrium solubility data of the salt and the free base in human aspirates and biorelevant media. The BioGIT system adequately simulated the average albendazole gastrointestinal transfer process and concentrations in upper small intestine after administration of the free base suspensions to fasted adults. However, the degree of supersaturation observed in the duodenal compartment was greater than in vivo. Albendazole sulfate resulted in minimal increase of albendazole concentrations in the duodenal compartment of the BioGIT, despite improved equilibrium solubility observed in human aspirates and biorelevant media, indicating that the use of a salt is unlikely to lead to any significant oral absorption advantage for albendazole

Toward the establishment of a standardized pre-clinical porcine model to predict food effects:Case studies on fenofibrate and paracetamol

A preclinical porcine model that reliably predicts human food effect of fenofibrate was developed. Fenofibrate was administered to pigs as model compound with a positive food effect. Two different types of fed conditions were explored: a FDA style breakfast and a standard pig pellet feed. In order to assess if complete stomach emptying had been achieved under the employed fasting protocol, the amount of gastric and intestinal content was evaluated post-mortem. In addition, the protocol was designed to evaluate gastric emptying in the pre- and postprandial state using paracetamol as a marker. The study confirmed that micronized fenofibrate displayed a positive food effect with a similar fold difference to humans in FDA style fed state. Post-mortem assessment of stomach and intestinal content confirmed significantly lower content in the fasted compared to the pig pellet fed state. In the case of paracetamol, a delayed gastric emptying in the fed state was not observed, which may suggest that the Magenstrasse phenomena reported in humans, may also occur in landrace pigs. The study demonstrated the utility of a food effect protocol in landrace pigs as a pre-clinical approach to predict human food effects and provided new insights into gastric emptying in pigs

Combining species specific in vitro & in silico models to predict in vivo food effect in a preclinical stage – case study of Venetoclax

The pig has been increasingly used as a reliable preclinical model for assessing and predicting the in vivo bioavailability of different formulation strategies. Nevertheless, differences in the composition between porcine and human intestinal fluids, may impact on the solubility and dissolution behaviour of drugs, in particular BCS II/IV drugs. Recently, a porcine fasted simulated intestinal fluid (FaSSIFp) was developed to mimic the composition in the lumen of landrace pigs under fasted state conditions. In this work, we present the utilization of FaSSIFp to compare solubility against human FaSSIF & FeSSIF and further combine species specific in vitro testing with in silico predictive modelling. Venetoclax was chosen as a model drug, representing a BCS class IV drug, with a reported clinically significant positive food effect, where bioavailability is increased up to approximately five-fold when administered with a high-fat meal. Biorelevant species specific in vitro testing was a promising tool for integrating in vitro data into in silico models, using FaSSIFp resulted in reliable predictions of the plasma concentration profile in fasted pigs, based on a porcine physiologically based absorption model. The porcine physiologically based absorption model was used to prospectively simulate the impact of food on the bioavailability of venetoclax. The use of luminal solubility estimates in combination with dissolution data for venetoclax, measured in species specific simulated fluids, correctly predict the observed pig plasma concentration profile and food effect. Overall, integrating species specific in vitro – in silico models led to accurate prediction of in vivo absorption of venetoclax in a preclinical stage, which can support guidance in early decisions of drug product development. In addition, the study further demonstrated the utility of the pig model to predict the food effects of venetoclax in humans

Disposition of two highly permeable drugs in the stomach and the upper small intestine of healthy adults after a standard high-calorie, high-fat meal

Objectives: To quantify the presence of two model highly permeable drugs, paracetamol and danazol, in the upper gastrointestinal lumen under conditions simulating the situation after disintegration of immediate release dosage forms administered in bioavailability/bioequivalence studies in the fed state. To understand the drug transfer process from the antral contents through the upper small intestine using the luminal drug data. Methods: 8 healthy male adult volunteers participated in a randomized, single dose, two-phase, crossover study. After evaluating the impact of homogenization on meal’s viscosity and particle size, the meal, containing phenol red as non-absorbable marker, was administered to the antrum via the gastric lumen of a naso-gastro-intestinal tube. The drugs were administered in solution form (Phase I) and in suspension form (Phase II) with a glass of tap water to the antrum of the stomach, 30 min after the initiation of meal administration. Samples were aspirated from the antrum and the upper small intestine up to 4 hours post drug administration. Results: Apparent concentrations in the aqueous contents of the antrum were higher than apparent concentrations in micellar contents of the upper small intestine for paracetamol; the opposite was observed for danazol. Based on total drug amount per volume data in contents of the upper gastrointestinal lumen, the transfer of paracetamol (aqueous solution or suspension) and danazol (aqueous suspension) through the upper small intestine could be described as an apparent first-order process. Transfer of a long-chain triglyceride solution of danazol was highly variable. Conclusions: Concentrations in the aqueous/micellar phase of luminal contents and values of parameters controlling the transfer from bulk gastric contents through the upper small intestine after a high-calorie, high-fat meal, were reported for the first time for highly permeable drugs. Data are expected to enhance the development of biorelevant in vitro and physiologically based biopharmaceutics modelling methodologies

Factors affecting successful extrapolation of ibuprofen exposure from adults to paediatric populations after oral administration of a paediatric aqueous suspension

The importance of physiologically based pharmacokinetic (PBPK) model refinement for adults with data acquired in adults using a paediatric formulation under age-relevant dosing conditions in order to extrapolate drug exposure to infants was recently demonstrated for paracetamol. In the present investigation the aim was to expand the use of PBPK modeling informed by bioavailability data collected in healthy adults under different dosing conditions for a low solubility weak acid, ibuprofen, to simulate exposure across paediatric populations, i.e., infants, pre-school children, and schoolchildren. After developing and evaluating an adult disposition and oral absorption model for the aqueous suspension of ibuprofen, ibuprofen performance was extrapolated to paediatrics simulating exposure as a function of different prandial and dosing conditions: fasted conditions, reference-meal-fed conditions (solid-liquid meal), and infant-formula-fed conditions (homogeneous liquid). Successful predictions were achieved when employing the refined model for fasted or by applying appropriate fed conditions for different age groups, i.e., infant formula for infants and reference meal for children. The present study suggested that ibuprofen performance was primarily guided by gastric emptying events and showed sensitivity towards formulation characteristics and pH changes in the small intestine. Better understanding of luminal conditions’ changes in paediatrics and age-dependent ibuprofen post-absorptive processes could improve modeling confidence for ibuprofen, as well as other drugs with similar properties

THE IMPACT OF FOOD INTAKE ON THE LUMINAL ENVIRONMENT AND PERFORMANCE OF ORAL DRUG PRODUCTS WITH A VIEW TO IN VITRO AND IN SILICO SIMULATIONS: A PEARRL REVIEW

Objective: Using the type of meal and dosing conditions suggested by regulatory agencies as a basis, this review has two specific objectives. First, to summarize our understanding on the impact of food intake on luminal environment and drug product performance. Second, to summarize the usefulness and limitations of available in vitro and in silico methodologies for the evaluation of drug products performance after food intake. Key findings: Characterization of the luminal environment and studies evaluating product performance in the lumen, under conditions suggested by regulatory agencies for simulating the fed state, are limited. Various in vitro methodologies have been proposed for evaluating drug product performance in the fed state but systematic validation is lacking. Physiologically based pharmacokinetic (PBPK) modelling approaches require the use of in vitro biorelevant data and, to date, have been used primarily for investigating the mechanisms via which an already observed food effect is mediated. Conclusion: Better understanding of the impact of changes induced by the meal administration conditions suggested by regulatory agencies on the luminal fate of the drug product is needed. Relevant information will be useful for optimizing the in vitro test methods, and increasing the usefulness of PBPK modelling methodologies