Comparative Assessment of Miniaturized Screening Approaches for Selection of Polymers for Amorphous Drug Stabilization

Solvent-Casted Films to Assist Polymer Selection for Amorphous Solid Dispersions During Preclinical Studies: In-vitro and In-vivo Exploration

PURPOSE

The use of two solvent-casted film methods to select optimal polymer compositions for amorphous solid dispersions prepared to support preclinical pharmacokinetic and toxicology studies is described.

METHODS

Evaporation of solvent from cover slips by using nitrogen flow, and solvent removal from vials by using rotary evaporation were employed. The films prepared on cover slips were evaluated under the microscope to determine crystallinity. The methods were validated by scaling up corresponding SDDs, evaluating SDD's dissolution, and comparing those results to the dissolution of drug-polymer films. Subsequently, SDD suspensions were prepared and dosed orally to rats to determine pharmacokinetic parameters. This was done by using three compounds from our pipeline and evaluating multiple polymers.

RESULTS

The dissolution of generated films showed good agreement with the dissolution of spray dried dispersions when the films were fully amorphous (Compound A and B). In contrast, there was disagreement between film and SDD dissolution when the films had crystallized (Compound C). The in vivo exposure results indicated that the polymer choice based on the film screening methods would have been accurate for drug-polymer films that were amorphous (Compound A and B). Two additional case studies (Compound D and E) are presented, showing good agreement between in vivo and in vitro results.

CONCLUSION

This study established the ability of two film casting screening methods to predict the in vitro and in vivo performance of corresponding SDDs, provided that the films are fully amorphous.

Impact of polymer type, ASD loading and polymer-drug ratio on ASD tablet disintegration and drug release

Amorphous solid dispersion (ASD) has become an attractive strategy to enhance solubility and bioavailability of poorly water-soluble drugs. To facilitate oral administration, ASDs are commonly incorporated into tablets. Disintegration and drug release from ASD tablets are thus critical for achieving the inherent solubility advantage of amorphous drugs. In this work, the impact of polymer type, ASD loading in tablet and polymer-drug ratio in ASD on disintegration and drug release of ASD tablets was systematically studied. Two hydrophilic polymers PVPVA and HPMC and one relatively hydrophobic polymer HPMCAS were evaluated. Dissolution testing was performed, and disintegration time was recorded during dissolution testing. As ASD loading increased, tablet disintegration time increased for all three polymer-based ASD tablets, and this effect was more pronounced for hydrophilic polymer-based ASD tablets. As polymer-drug ratio increased, tablet disintegration time increased for hydrophilic polymer-based ASD tablets, however, it remained short and largely unchanged for HPMCAS-based ASD tablets. Consequently, at high ASD loadings or high polymer-drug ratios, HPMCAS-based ASD tablets showed faster drug release than PVPVA- or HPMC-based ASD tablets. These results were attributed to the differences between polymer hydrophilicities and viscosities of polymer aqueous solutions. This work is valuable for understanding the disintegration and drug release of ASD tablets and provides insight to ASD composition selection from downstream tablet formulation perspective.

Modeling and Simulation of Process Technology for Nanoparticulate Drug Formulations-A Particle Technology Perspective

Crystalline organic nanoparticles and their amorphous equivalents (ONP) have the potential to become a next-generation formulation technology for dissolution-rate limited biopharmaceutical classification system (BCS) class IIa molecules if the following requisites are met: (i) a quantitative understanding of the bioavailability enhancement benefit versus established formulation technologies and a reliable track record of successful case studies are available; (ii) efficient experimentation workflows with a minimum amount of active ingredient and a high degree of digitalization via, e.g., automation and computer-based experimentation planning are implemented; (iii) the scalability of the nanoparticle-based oral delivery formulation technology from the lab to manufacturing is ensured. Modeling and simulation approaches informed by the pharmaceutical material science paradigm can help to meet these requisites, especially if the entire value chain from formulation to oral delivery is covered. Any comprehensive digitalization of drug formulation requires combining pharmaceutical materials science with the adequate formulation and process technologies on the one hand and quantitative pharmacokinetics and drug administration dynamics in the human body on the other hand. Models for the technical realization of the drug production and the distribution of the pharmaceutical compound in the human body are coupled via the central objective, namely bioavailability. The underlying challenges can only be addressed by hierarchical approaches for property and process design. The tools for multiscale modeling of the here-considered particle processes (e.g., by coupled computational fluid dynamics, population balance models, Noyes–Whitney dissolution kinetics) and physiologically based absorption modeling are available. Significant advances are being made in enhancing the bioavailability of hydrophobic compounds by applying innovative solutions. As examples, the predictive modeling of anti-solvent precipitation is presented, and options for the model development of comminution processes are discussed.

Are traditional small-scale screening methods reliable to predict pharmaceutical spray drying?

Driven by the new trend to build quality into products and reducing empiricism, small-scale screening techniques have been frequently used to evaluate, thermodynamic of drug solubility in the polymer, and drug-polymer kinetic amorphous miscibility. In this paper, these methods have been overviewed to shed light on their liabilities in predicting spray-dried amorphous solid dispersions' (ASDs) properties. By scrutinizing relevant open literature, several inconsistencies have been recognized, deemed to be due to the inability of conventional miniaturized means to simulate the spray drying process operations/constraints in formulating active pharmaceutical ingredients (APIs). Given the complex interplay of thermodynamics of mixing, heat and mass transfer, and fluid dynamics in this process, scaling rules have been introduced to remedy arisen issues in conventional miniaturized tools. Accordingly, spray drying process is analyzed considering the fundamental physical transformations involved, i.e. atomization and drying. Each transformation is explored from a scaling perspective with an emphasis on key response factors, and ways to retain them for each transformation across scales. Prospective bifurcated developments may improve the odds of successful formulations/process conditions later on during development stages.

High-Throughput Dissolution/Permeation Screening -A 96-Well Two-Compartment Microplate Approach

Early formulation screening can alleviate development of advanced oral drug formulations, such as amorphous solid dispersions (ASDs). Traditionally, dissolution is used to predict ASD performance. Here, a high-throughput approach is described that simultaneously screens drug dissolution and permeation employing a two-compartment 96-well plate. Freeze-drying from hydro-alcoholic solutions was used to prepare amorphous formulations. The screening approach was tested on amorphous and crystalline tadalafil formulations with and without Soluplus^®. The workflow consisted of: 1) dispersion of the formulations; 2) incubation within the two-compartment plate, where a dialysis membrane separated donor (dispersed formulation) and acceptor; 3) sampling (donor and acceptor), where donor samples were centrifuged to remove non-dissolved material; and 4) quantification by UHPLC-UV. To identify optimal screening conditions, the following parameters were varied: dispersion medium (buffer / biomimetic media), acceptor medium (buffer / surfactant solutions), and incubation time (1, 3, and 6 h). Surfactants (acceptor) increased tadalafil permeation. Biomimetic medium (donor) enhanced dissolution, but not permeation, except for freeze-dried tadalafil, for which the permeated amount increased. The predictiveness was evaluated by comparing dissolution-/permeation-results with in vivo bioavailability. In general, both dissolution and permeation reflected bioavailability, whereof the latter was a better predictor. High-throughput dissolution/permeation is regarded promising for formulation screening.

Automated assays for thermodynamic (equilibrium) solubility determination

Solubility is a crucial physicochemical property for drug candidates and is important in both drug discovery and development. Poor solubility is detrimental to absorption after oral administration and can mask compound activity in bioassays in various ways. Hence, solubility liabilities should ideally be identified as early as possible in the drug development process. With the increasing number of compounds as potential drug candidates, automated thermodynamic solubility assays for high throughput screening enabling rapid evaluation of a large number of compounds are becoming increasingly important. This review discusses the current status of the most widely used automated assays for thermodynamic solubility, followed by recent high throughput measurements of properties related to solubility (e.g. dissolution rate and supersaturation) and a brief overview of predictive computational methods for thermodynamic solubility reported in the literature.