Drug Permeability Profiling Using the Novel Permeapad® 96-Well Plate.

PURPOSE: Here, first experiences with a prototype tool for high throughput (passive) permeability profiling, a 96-well plate comprising the Permeapad® membrane, are reported. The permeabilities of a set of drugs were determined and compared to published measures of oral absorption, such as human fraction absorbed (Fa) and in vitro permeability values obtained using other tools. METHODS: The tool consists of a 96-well bottom and screen plate with the artificial, phospholipid-based barrier (Permeapad®) mounted between the plates' lower and upper compartments. The permeability of 14 model compounds including high- and low-absorption drugs, cationic, anionic, zwitterionic and neutral molecules, was determined by quantifying the compounds' transport over time, deriving the steady-state flux from the linear part of the cumulative curves and calculating the apparent permeability (Papp). The membrane structure was investigated in a high-resolution digital light microscope. RESULTS: The Permeapad® 96-well plate was found suited to distinguish high and low absorption drugs and yielded a hyperbolic correlation to Fa. The Papp values obtained were congruent with those determined with in-house prepared Permeapad® in the Franz cell set-up. Furthermore, good to excellent correlations were seen with Caco-2 permeability (R2 = 0.70) and PAMPA permeability (R2 = 0.89). Microscopic investigation of the Permeapad® barrier revealed the formation of phospholipid vesicles and myelin figures in aqueous environment. CONCLUSION: The Permeapad® 96-well plate permeation set-up is a promising new tool for rapid and reproducible passive permeability profiling.

Single step bottom-up process to generate solid phospholipid nano-particles.

CONTEXT: The particularity of the Nano Spray Dryer B-90 is the nozzle containing a mesh vibrating at ultrasonic frequency. OBJECTIVE: To study process parameters and processability of crude phospholipid dispersions, in particular the effect of concentration and mesh aperture on both particle size of the dry solid phospholipid nano-particles and on the re-dispersed powder. MATERIALS AND METHODS: Phospholipid dispersions containing trehalose as a stabilizer were spray dried. Particle size distributions of dry powders were evaluated by SEM micrographs and by PCS and cryo-TEM for the re-dispersed particles. RESULTS: Spray drying of crude liposome dispersions revealed solid phospholipid nano-particles. Aperture of nozzle mesh and concentration of the dispersions, respectively, both increased the size of solid phospholipid nano-particles. For crude dispersions, an upper limit with respect to processability was found close to below 10% (m/m) even if the crude dispersion was passed along the mesh several times; however, more effective dispersing methods such as pre-sonication can push the limit of processability to higher values. DISCUSSION AND CONCLUSION: The nano spray dryer is capable of spray drying crude dispersions of phospholipids in concentrations below 10% (m/m) generating solid phospholipid nano-particles relevant for pulmonary delivery. Re-dispersion of spray dried powder reveals liposomes.

Digestion is a critical element for absorption of cinnarizine from supersaturated lipid-based type I formulations.

Enabling formulations, such as lipid-based formulations (LBFs), are means to deliver challenging-to-formulate, poorly soluble drugs. LBFs may be composed of lipids, surfactants and/or cosolvents and can be classified depending on the proportions of the components and the hydrophilicity of the surfactant according to the Lipid Formulations Classification System, ranging from type I (very lipophilic) to type IV (hydrophilic). In cases where drug solubility in LBFs does not suffice, e.g. for preclinical toxicity studies, supersaturated LBFs can be used in order to increase the drug load. However, the effect of digestion on drug absorption from supersaturated type I formulations (consisting exclusively of lipids) still remains relatively unexplored and unclear. In the present study, the impact of lipid digestion on absorption of cinnarizine-loaded supersaturated lipid-based formulations of type I was investigated in rats by pre-dosing of the lipase inhibitor orlistat. The lipid chain length and the drug dose were varied by testing medium-chain triglycerides (MCT) and long-chain triglycerides (LCT), both supersaturated and non-supersaturated. Due to the physical instability of supersaturated formulations of cinnarizine, i.e. a potential of precipitation of cinnarizine, the impact of the addition of the amphiphilic polymer Soluplus®, as a potential precipitation inhibitor, was also investigated. The supersaturated systems resulted in a 2.3 - 3.3-fold higher Area Under the Curve (AUC0-24 h, not dose-normalized) and 1.4 - 2.2-fold higher maximum plasma concentration (Cmax, not dose-normalized) than non-supersaturated formulations (statistically significant with p = 0.05), whereas the addition of Soluplus® did not reveal any benefit. Results indicated that lipase inhibition affected the in vivo performance of LBFs: Co-administration of the lipase inhibitor significantly reduced Cmax and AUC0-24 h (both to 33-39 %, not dose-normalized) for the LCT formulations and, though not significant, a similar trend was observed for the AUC0-24 h of the MCT formulations (to 53-87 %), suggesting a higher dependency on lipolysis for LCT. Also, tmax tended to decrease to 20-60 % when compared to the animals not dosed with orlistat but lacking statistical significance. Without lipase inhibition, the LCT in general lead to better absorption of cinnarizine as compared to MCT, with 1.2-1.7-fold higher AUC0-24 h and 1.4-1.8-fold higher Cmax, but without showing statistical significance. Overall, the study revealed that lipolysis plays a major role in drug absorption from supersaturated lipid-based formulations type I.

Absorption of cinnarizine from type II lipid-based formulations: Impact of lipid chain length, supersaturation, digestion, and precipitation inhibition.

Lipid-based formulations (LBFs) are an enabling-formulation approach for lipophilic poorly water-soluble compounds. In LBFs, drugs are commonly pre-dissolved in lipids, and/or surfactants/cosolvents, hereby avoiding the rate-limiting dissolution step. According to the Lipid formulation classification system, proposed by Pouton in 2006, in type II LBFs a surfactant with an HLB-value lower than 12 is added to the lipids. If high drug doses are required, e.g. for preclinical toxicity studies, supersaturated LBFs prepared at elevated temperatures may be a possibility to increase drug exposure. In the present study, the impact of digestion on drug absorption in rats was studied by pre-dosing of the lipase inhibitor orlistat. The lipid chain length of the type II LBFs was varied by administration of a medium-chain- (MC) and a long-chain (LC)-based formulation. Different drug doses, both non-supersaturated and supersaturated, were applied. Due to an inherent precipitation tendency of cinnarizine in supersaturated LBFs, the effect of the addition of the precipitation inhibitor Soluplus® was also investigated. The pharmacokinetic results were also evaluated by multiple linear regression. In most cases LC-based LBFs did not perform better in vivo, in terms of a higher area under the curve (AUC0-24 h) and maximal plasma concentration (Cmax), than MC-based LBFs. The administration of supersaturated LBFs resulted in increased AUC0-24 h (1.5 - 3.2-fold) and Cmax (1.1 - 2.6-fold)-values when compared to the non-supersaturated equivalents. Lipase inhibition led to a decreased drug exposure in most cases, especially for LC formulations (AUC0-24 h reduced to 47 - 67%, Cmax to 46 - 62%). The addition of Soluplus® showed a benefit to drug absorption from supersaturated type II LBFs (1.2 - 1.7-fold AUC0-24 h), due to an increased solubility of cinnarizine in the formulation. Upon dose-normalization of the pharmacokinetic parameters, no beneficial effect of Soluplus® could be demonstrated.

Water-mediated phase transformations of posaconazole: An intricate jungle of crystal forms.

Posaconazole is a broad-spectrum antifungal agent exhibiting rich polymorphism. Up to now, a total of fourteen different crystal forms have been reported, sometimes with an ambiguous nomenclature, but less is known about their properties and stability relationships. Investigating the solid-state of a drug compound is essential to identify the most stable form under working conditions and to prevent the risk of undesired solid-phase transformations under processing and storage. In this paper, we study posaconazole polymorphism by providing a description of its polymorphs, hydrates, and solvates. Powder X-ray diffraction (PXRD), dynamic vapor sorption (DVS), spectroscopic and thermal techniques were employed to characterize the different forms. In addition, the solid-phase transformations of posaconazole in aqueous suspensions were studied by means of Raman microscopy. Surprisingly, we found that Form S, the crystal form contained in the marketed oral suspension, is not the most stable form in water. Form S readily converts to a more stable hydrate, i.e. Form A, after storage in water for two weeks. In the commercial oral formulation the conversion between the two forms is prevented by the presence of polysorbate 80. Such insights into the stabilizing excipient effects beyond particle dispersion are critical to formulators.

Oral Absorption from Surfactant-Based Drug Formulations: The Impact of Molecularly Dissolved Drug on Bioavailability.

Enabling drug formulations are often required to ensure sufficient absorption after oral administration of poorly soluble drugs. While these formulations typically increase the apparent solubility of the drug, it is widely acknowledged that only molecularly dissolved, i.e., free fraction of the drug, is prone for direct absorption, while colloid-associated drug does not permeate to the same extent. In the present study, we aimed at comparing the effect of molecularly and apparently (i.e., the sum of molecularly and colloid-associated drug) dissolved drug concentrations on the oral absorption of a poorly water-soluble drug compound, Alectinib. Mixtures of Alectinib and respectively 50 %, 25 %, 12.5 %, and 3 % sodium lauryl sulfate (SLS) relative to the dose were prepared and small-scale dissolution tests were performed under simulated fed and fasted state conditions. Both the molecularly and apparently dissolved drug concentrations were assessed in parallel using microdialysis and centrifugation/filtration sampling, respectively. The data served as the basis for an in vitro-in vivo correlation (IVIVC) and as input for a GastroPlusTM physiologically-based biopharmaceutics model (PBBM). It was shown that with increasing the content of SLS the apparently dissolved drug in FeSSIF and FaSSIF increased to a linear extent and thus, the predicted in vivo performance of the 50 % SLS formulation, based on apparently dissolved drug, would outperform all other formulations. Against common expectation, however, the free (molecularly dissolved) drug concentrations were found to vary with SLS concentrations as well, yet to a minor extent. A systematic comparison of solubilized and free drug dissolution patterns at different SLS contents of the formulations and prandial states allowed for interesting insights into the complex dissolution-/supersaturation-, micellization-, and precipitation-behavior of the formulations. When comparing the in vitro datasets with human pharmacokinetic data from a bioequivalence study, it was shown that the use of molecularly dissolved drug resulted in an improved IVIVC. By incorporating the in vitro dissolution datasets into the GastroPlusTM PBBM, the apparently dissolved drug concentrations resulted in both, a remarkable overprediction of plasma concentrations as well as a misprediction of the influence of SLS on systemic exposure. In contrast, by using the molecularly dissolved drug (i.e., free fraction) as the model input, the predicted plasma concentration-time profiles were in excellent agreement with observed data for all formulations under both fed and fasted conditions. By combining an advanced in vitro assessment with PBBM, the present study confirmed that only the molecularly dissolved drug, and not the colloid-associated drug, is available for direct absorption.

Using molecularly dissolved drug concentrations in PBBMs improves the prediction of oral absorption from supersaturating formulations.

Predicting the absorption of drugs from enabling formulations is still challenging due to the limited capabilities of standard physiologically based biopharmaceutics models (PBBMs) to capture complex absorption processes. Amongst others, it is often assumed that both, molecularly and apparently dissolved drug in the gastrointestinal lumen are prone to absorption. A recently introduced method for measuring concentrations of molecularly dissolved drug in a dynamic in vitro dissolution setup using microdialysis has opened new opportunities to test this hypothesis and refine mechanistic PBBM approaches. In the present study, we compared results of PBBMs that used either molecularly or apparently dissolved concentrations in the simulated gastrointestinal lumen as input parameters. The in vitro dissolution data from three supersaturating formulations of Posaconazole (PCZ) were used as model input. The modeling outcome was verified using PCZ concentration vs. time profiles measured in human intestinal aspirates and in the blood plasma. When using apparently dissolved drug concentrations (i.e., the sum of colloid-associated and molecularly dissolved drug) the simulated systemic plasma exposures were overpredicted, most pronouncedly with the ASD-based tablet. However, if the concentrations of molecularly dissolved drug were used as input values, the PBBM resulted in accurate prediction of systemic exposures for all three PCZ formulations. The present study impressively demonstrated the value of considering molecularly dissolved drug concentrations as input value for PBBMs of supersaturating drug formulations.

Exploring the Cocrystal Landscape of Posaconazole by Combining High-Throughput Screening Experimentation with Computational Chemistry.

The development of multicomponent crystal forms, such as cocrystals, represents a means to enhance the dissolution and absorption properties of poorly water-soluble drug compounds. However, the successful discovery of new pharmaceutical cocrystals remains a time- and resource-consuming process. This study proposes the use of a combined computational-experimental high-throughput approach as a tool to accelerate and improve the efficiency of cocrystal screening exemplified by posaconazole. First, we employed the COSMOquick software to preselect and rank cocrystal candidates (coformers). Second, high-throughput crystallization experiments (HTCS) were conducted on the selected coformers. The HTCS results were successfully reproduced by liquid-assisted grinding and reaction crystallization, ultimately leading to the synthesis of thirteen new posaconazole cocrystals (7 anhydrous, 5 hydrates, and 1 solvate). The posaconazole cocrystals were characterized by PXRD, 1H NMR, Fourier transform-Raman, thermogravimetry-Fourier transform infrared spectroscopy, and differential scanning calorimetry. In addition, the prediction performance of COSMOquick was compared to that of two alternative knowledge-based methods: molecular complementarity (MC) and hydrogen bond propensity (HBP). Although HBP does not perform better than random guessing for this case study, both MC and COSMOquick show good discriminatory ability, suggesting their use as a potential virtual tool to improve cocrystal screening.

Inexpensive and Easy-To-Use Alternative to the Die Holder for Pharmacopoeial Intrinsic Dissolution Tests.

The pharmacopoeial test method "Intrinsic Dissolution" (Ph.Eur. 2.9.29) is used to study the rate of dissolution for powders of active pharmaceutical ingredients normalized by the surface area. Therefore, powders are compacted into a special metal die holder, which is immersed into a dissolution vessel of the dissolution test apparatus (described in Ph.Eur. 2.9.3). However, in some cases, the test cannot be performed because the compacted powder would not stay in the die holder when in contact with the dissolution medium. In this study, we investigated the removable adhesive gum (RAG) as an alternative to the official die holder. Intrinsic dissolution tests were carried out to exemplify the use of the RAG for this purpose. As model substances, acyclovir and its co-crystal with glutaric acid were used. The RAG was validated for compatibility, release of extractables, unspecific adsorption and the ability to block drug release through the covered surfaces. The results showed that the RAG leaked no unwanted substances, showed no adsorption of acyclovir and blocked its release from covered surfaces. The intrinsic dissolution tests revealed, as expected, a constant release of drug with a small standard deviation between replicates. It was possible to distinguish the acyclovir release from the co-crystal and from the pure drug compound. In conclusion, the findings of this study suggest to consider removable adhesive gum as an easy-to-use and inexpensive alternative to the compendial die holder in intrinsic dissolution tests.

When Interactions Between Bile Salts and Cyclodextrin Cause a Negative Food Effect: Dynamic Dissolution/Permeation Studies with Itraconazole (Sporanox®) and Biomimetic Media.

The marketed oral solution of itraconazole (Sporanox®) contains 40% (259.2 mM) of 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD). The obvious role of HP-ß-CD is to solubilize itraconazole and to overcome its poor aqueous solubility that restricts its absorption. In this study, we investigated the biorelevance of in vitro experiments by the influence of biomimetic media (containing bile salts and phospholipids) on the predicted itraconazole absorption from the commercial HP-ß-CD-based Sporanox® solution. We performed phase-solubility studies of itraconazole and dynamic 2-step-dissolution/permeation studies using a biomimetic artificial barrier, Sporanox® solution, and fasted state simulated intestinal fluid (FaSSIF_V1). Both FaSSIF_V1 and HP-ß-CD increased the apparent solubility of itraconazole when used individually. In combination, their solubility-enhancing effects were not additive probably due to the competition of bile salts with itraconazole for the hydrophobic cavity of HP-ß-CD. Our combined dissolution/permeation experiments indicated the occurrence of a transient supersaturation from Sporanox® upon two-step dissolution. Through systematic variation of bile salt concentrations in the biomimetic media, it was observed that the extent and the duration of supersaturation depend on the concentrations of bile salts: supersaturation was rather stable in the absence of bile salts and phospholipids. The higher the bile salt concentration, the faster the collapse of the transient supersaturation occurred, an effect which is nicely mirrored by reduced in vitro permeation across the barrier. This is an indication of a negative food effect, which in fact correlates well with what earlier had been observed in clinical studies for Sporanox® solution. In essence, we could demonstrate that in vitro two-stage dissolution/permeation experiments using an artificial barrier and selected biomimetic media may predict the negative effects of the latter on cyclodextrin-based drug formulations like Sporanox® Oral Solution and, at the same time, provide a deeper mechanistic insight.

Insight into the mechanism behind oral bioavailability-enhancement by nanosuspensions through combined dissolution/permeation studies.

As numerous new drug candidates are poorly water soluble, enabling formulations are needed to increase their bioavailability for oral administration. Nanoparticles are a conceptually simple, yet resource consuming strategy for increasing drug dissolution rate, as predicting in vivo oral absorption using in vitro dissolution remains difficult. The objective of this study was to obtain insight into nanoparticle characteristics and performance utilizing an in vitro combined dissolution/permeation setup. Two examples of poorly soluble drugs were examined (cinnarizine and fenofibrate). Nanosuspensions were produced by top-down wet bead milling using dual asymmetric centrifugation, obtaining particle diameters of approx. 300 nm. DSC and XRPD studies indicated that nanocrystals of both drugs were present with retained crystallinity, however with some disturbances. Equilibrium solubility studies showed no significant increase in drug solubility over the nanoparticles, as compared to the raw APIs. Combined dissolution/permeation experiments revealed significantly increased dissolution rates for both compounds compared to the raw APIs. However, there were substantial differences between the dissolution curves of the nanoparticles as fenofibrate exhibited supersaturation followed by precipitation, whereas cinnarizine did not exhibit any supersaturation, but instead a shift towards faster dissolution rate. Permeation rates were found significantly increased for both nanosuspensions when compared to the raw APIs, indicating a direct implication that formulation strategies are needed, be it stabilization of supersaturation by precipitation inhibition and/or dissolution rate enhancement. This study indicates that in vitro dissolution/permeation studies can be employed to better understand the oral absorption enhancement of nanocrystal formulations.

In vitro dissolution/permeation tools for amorphous solid dispersions bioavailability forecasting I: Experimental design for PermeaLoop™.

Along with the increasing demand for candidate-enabling formulations comes the need for appropriate in vitro bioavailability forecasting. Dissolution/permeation (D/P) systems employing cell-free permeation barriers are increasingly gaining interest, due to their low cost and easy application as passive diffusion bio-predictive profiling in drug product development, as this accounts for nearly 75% of new chemical entities (NCEs) absorption mechanism. To this end, this study comprises theoretical considerations on the design and experimental work towards the establishment and optimization of a PermeaLoop™ based dissolution/permeation assay to simultaneously evaluate the drug release and permeation using Itraconazole (ITZ)-based amorphous solid dispersions (ASD) formulations, with different drug loads, based on a solvent-shift approach. Alternative method conditions were tested such as: donor medium, acceptor medium and permeation barrier were screened using both PermeaPad® and PermeaPlain® 96-well plates. A range of solubilizers, namely Sodium Dodecyl Sulfate, Vitamin E-TPGS and hydroxypropyl-ß-cyclodextrin, were screened as possible solubilizing additives to the acceptor medium, while donor medium was varied between blank FaSSIF (phosphate buffer) and FaSSIF. The method optimization also included the ITZ dose selection, being the ITZ single dose (100 mg) considered the most adequate to be used in further experiments to allow the comparison with in vivo studies. In the end, a standardized approach that may be applied to predict the bioavailability of weakly basic poorly soluble drug-based formulations is described, contributing to strengthening the analytical portfolio of in vitro pre-clinical drug product development.

Hydrogenated phospholipid, a promising excipient in amorphous solid dispersions of fenofibrate for oral delivery: Preparation and in-vitro biopharmaceutical characterization.

Amorphous solid dispersions (ASD) represent a viable formulation strategy to improve dissolution and bioavailability of poorly soluble drugs. Our study aimed to evaluate the feasibility and potential role of hydrogenated phospholipid (HPL) as a matrix material and solubilizing additive for binary (alone) or ternary (in combination with polymers) solid dispersions, using fenofibrate (FEN) as the model drug. FEN, incorporated within ASDs by melting or freeze-drying (up to 20% m/m), stayed amorphous during short-term stability studies. The solubility enhancing potential of HPL depended on the dissolution medium. In terms of enhancing in vitro permeation, solid dispersions with HPL were found equally or slightly more potent as compared to the polymer-based ASD. For studied ASD, in vitro permeation was found substantially enhanced as compared to a suspension of crystalline FEN and at least equal compared to marketed formulations under comparable conditions (literature data). Additionally, while the permeation of neat FEN and FEN in binary solid dispersions was affected by the dissolution medium (i.e., the "prandial state"), for ternary solid dispersions the permeation was independent of the "prandial state" (FaSSIF = FeSSIF). This suggests that ternary solid dispersions containing both polymer and HPL may represent a viable formulation strategy to mitigate fenofibrate's food effect.

Combining in vitro dissolution/permeation with microdialysis sampling: Capabilities and limitations for biopharmaceutical assessments of supersaturating drug formulations.

Many novel small drug molecules are poorly water-soluble and thus, enabling drug formulations may be required to ensure sufficient absorption upon oral administration. Biopharmaceutical assessment and absorption prediction of enabling formulations, however, remains challenging. Combined in vitro dissolution/permeation (D/P) assays have gained increasing interest since they may provide a more realistic formulation ranking based on the drug permeation profiles from different formulations as compared to conventional dissolution, which captures both readily permeable and not readily permeable fractions of "dissolved" drug. Moreover, the combined in vitro D/P assays allow to better predict intestinal supersaturation and precipitation processes as compared to simple dissolution setups due to the effect of an absorptive sink. Microdialysis on the other hand has proven useful to determine molecularly dissolved drug in colloidal dispersions, thus allowing for a deeper mechanistic insight into the mechanism of drug release from supersaturating formulations. Here, microdialysis sampling from the donor compartment was used in combination with the dissolution/permeation (D/P) tool PermeaLoop™ to study commercial supersaturating drug formulations of the poorly soluble and weakly basic drug Posaconazole (PCZ). An amorphous solid dispersion (ASD)-based tablet, as well as a crystalline suspension in acidified and neutral dilution medium, respectively, were tested. Microdialysis sampling allowed for differentiation between molecularly dissolved and micellar drug concentration, as expected, but, surprisingly, it was found that the presence of the microdialysis probe affected the precipitation behavior of a crystalline suspension within the two-stage D/P setup, simulating the oral administration of the acidified PCZ (Noxafil®) suspension: the extent and duration of supersaturation in the donor decreased significantly, which also affected permeation. Similarly, for the ASD-based tablet, a less pronounced supersaturation was observed during the first 120 min of the experiment. Hence, in this case, the formulation ranking and the prediction of intestinal supersaturation in the in vitro D/P assay became less predictive as compared to a conventional PermeaLoop™ study without microdialysis sampling. It was concluded that valuable mechanistic insights into the molecularly dissolved drug profiles over time can be obtained by microdialysis. However, since the presence of the probe may affect the degree of supersaturation and precipitation, a conventional D/P assay (without microdialysis sampling) is preferred for formulation ranking of supersaturating drug formulations.

In-vitro dynamic dissolution/bioconversion/permeation of fosamprenavir using a novel tool with an artificial biomimetic permeation barrier and microdialysis-sampling.

Fosamprenavir is a phosphate ester prodrug that, upon dissolution, is cleaved to the poorly soluble yet readily absorbable parent drug amprenavir. In this study, a novel cell-free in vitro setup with quasi-continuous monitoring of the dynamic dissolution/bio-conversion/permeation of fosamprenavir was designed and tested. It consists of side-by-side diffusion cells, where the donor and acceptor compartments are separated by the biomimetic barrier PermeaPad®, and sampling from the donor compartment is accomplished via a microdialysis probe. Externally added bovine alkaline phosphatase induced bioconversion in the donor compartment. Microdialysis sampling allowed to follow the enzymatic conversion of fosamprenavir to amprenavir by the bovine alkaline phosphatase in an (almost) real-time manner eliminating the need to remove or inactivate the enzyme. Biomimetic conversion rates in the setup were established by adding appropriate amounts of the alkaline phosphatase. A substantial (6.5-fold) and persistent supersaturation of amprenavir was observed due to bioconversion at lower (500 µM) concentrations, resulting in a substantially increased flux across the biomimetic barrier, nicely reflecting the situation in vivo. At conditions with an almost 10-fold higher dose than the usual human dose, some replicates showed premature precipitation and collapse of supersaturation, while others did not. In conclusion, the proposed novel tool appears very promising in gaining an in-depth mechanistic understanding of the bioconversion/permeation interplay, including transient supersaturation of phosphate-ester prodrugs like fosamprenavir.

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.

Leveraging the use of in vitro and computational methods to support the development of enabling oral drug products: An InPharma commentary.

Due to the strong tendency towards poorly soluble drugs in modern development pipelines, enabling drug formulations such as amorphous solid dispersions, cyclodextrins, co-crystals and lipid-based formulations are frequently applied to solubilize or generate supersaturation in gastrointestinal fluids, thus enhancing oral drug absorption. Although many innovative in vitro and in silico tools have been introduced in recent years to aid development of enabling formulations, significant knowledge gaps still exist with respect to how best to implement them. As a result, the development strategy for enabling formulations varies considerably within the industry and many elements of empiricism remain. The InPharma network aims to advance a mechanistic, animal-free approach to the assessment of drug developability. This commentary focuses current status and next steps that will be taken in InPharma to identify and fully utilize 'best practice' in vitro and in silico tools for use in physiologically based biopharmaceutic models.

Drug Dissolution in Oral Drug Absorption: Workshop Report.

The in-person workshop "Drug Dissolution in Oral Drug Absorption" was held on May 23-24, 2023, in Baltimore, MD, USA. The workshop was organized into lectures and breakout sessions. Three common topics that were re-visited by various lecturers were amorphous solid dispersions (ASDs), dissolution/permeation interplay, and in vitro methods to predict in vivo biopharmaceutics performance and risk. Topics that repeatedly surfaced across breakout sessions were the following: (1) meaning and assessment of "dissolved drug," particularly of poorly water soluble drug in colloidal environments (e.g., fed conditions, ASDs); (2) potential limitations of a test that employs sink conditions for a poorly water soluble drug; (3) non-compendial methods (e.g., two-stage or multi-stage method, dissolution/permeation methods); (4) non-compendial conditions (e.g., apex vessels, non-sink conditions); and (5) potential benefit of having both a quality control method for batch release and a biopredictive/biorelevant method for biowaiver or bridging scenarios. An identified obstacle to non-compendial methods is the uncertainty of global regulatory acceptance of such methods.

Effect of degree of methoxylation and particle size on compression properties and compactibility of pectin powders.

This study examines the effect of the degree of methoxylation (DM) and particle size on compression properties and compactibility of pectin powders. A powder classification system based on sequential handling of compression parameters was applied. A single size fraction (90-125 µm) of pectin powders with DM values ranging from 5-72% was studied. For DM 25%, the effect of different particle size fractions (180-250, 125-180, 90-125, 63-90, 45-63, <45 µm) were investigated. Compression parameters were derived based on time-resolved force-displacement data using Heckel, Kawakita and Shapiro equations. Volume-specific surface area was estimated for powders and tablets. Tablet tensile strength was determined. It was found that all pectin powders displayed low degrees of particle rearrangement and relatively low degrees of fragmentation (class IIA materials). Pectin particles were found to be relatively soft, with a tendency towards softer particles for pectins of higher DM. The overall variation in fragmentation and deformation behavior was limited. Both DM and initial particle size affected the tensile strength of pectin tablets. The difference in surface hydrophobicity caused by the DM was suggested as being responsible for the variation in the mechanical strengths. The study shows that pectin grades with DM ≤ 40% are potential direct compression excipients.

Felodipine-diazabicyclo[2.2.2]octane-water (1/1/1).

The title compound, C(18)H(19)Cl(2)NO(4)·C(6)H(12)N(2)·H(2)O, is a cocrystal hydrate containing the active pharmaceutical ingredient felodipine and diazabicyclo[2.2.2]octane (DABCO). The DABCO and water molecules are linked through O-H···N hydrogen bonds into chains around 2(1) screw axes, while the felodipine molecules form N-H···O hydrogen bonds to the water molecules. The felodipine molecules adopt centrosymmetric back-to-back arrangements that are similar to those present in all of its four reported polymorphs. The dichlorophenyl rings also form π-stacking interactions. The inclusion of water molecules in the cocrystal, rather than formation of N-H···N hydrogen bonds between felodipine and DABCO, may be associated with steric hindrance that would arise between DABCO and the methyl groups of felodipine if they were directly involved in hydrogen bonding.