Scale-Up and In-line Monitoring During Continuous Melt Extrusion of an Amorphous Solid Dispersion

Enhancement of dissolution and oral bioavailability by adjusting microenvironment pH in crocetin ternary solid dispersions: Optimization, characterization, in vitro evaluation, and pharmacokinetics

The most promising active ingredient of Crocus sativus L., crocetin (CCT), has been demonstrated to possess many biological activities. However, only a few studies have been conducted on CCT formulation, especially in oral formulation, mainly due to its insolubility in water, which limits its application for oral administration. This article reports an equilibrium saturation solubility and single-pass intestinal perfusion studies conducted to classify the biopharmaceutics classification system (BCS) of CCT. To enhance in vitro dissolution and in vivo oral bioavailability, ternary solid dispersions of CCT (CCT-SDs) with soluplus (SOL) as hydrophilic carrier and meglumine (MEG) as alkalizer were optimized using response surface methodology (RSM) with central composite design (CCD) experiments. Four different preparation methods were evaluated using the optimal formulation, including solvent evaporation, ball milling, spray drying, and freeze-drying. Prepared formulations were characterized by TG-DSC, FTIR, X-RPD, and SEM; the pharmacokinetic studies were performed in rats after oral administration. The cumulative dissolution rate of CCT-SDs containing SOL and MEG prepared by the ball milling method was 97.1% at 15 min and remained at 95.6% at 480 min, which was significantly higher than that of untreated CCT. The lower crystallinity, smaller particle size, and higher microenvironment pH (pHM) were observed in CCT-SDs prepared by the ball milling method. In vivo absorption of CCT-SDs (Cmax = 52.789 ± 12.441 μg/mL and AUC0-12 = 191.748 ± 35.043 μg/mL·h) was greater than untreated CCT (Cmax = 5.918 ± 1.388 μg/mL and AUC0-12 = 44.309 ± 7.264 μg/mL·h). In conclusion, the current study provides ternary solid dispersion formulation of CCT to increase the in vitro dissolution and in vivo bioavailability, which will benefit the commercial production and future clinical applications of CCT.

The applications of machine learning to predict the forming of chemically stable amorphous solid dispersions prepared by hot-melt extrusion

Amorphous solid dispersion (ASD) is one of the most important strategies to improve the solubility and dissolution rate of poorly water-soluble drugs. As a widely used technique to prepare ASDs, hot-melt extrusion (HME) provides various benefits, including a solvent-free process, continuous manufacturing, and efficient mixing compared to solvent-based methods, such as spray drying. Energy input, consisting of thermal and specific mechanical energy, should be carefully controlled during the HME process to prevent chemical degradation and residual crystallinity. However, a conventional ASD development process uses a trial-and-error approach, which is laborious and time-consuming. In this study, we have successfully built multiple machine learning (ML) models to predict the amorphization of crystalline drug formulations and the chemical stability of subsequent ASDs prepared by the HME process. We utilized 760 formulations containing 49 active pharmaceutical ingredients (APIs) and multiple types of excipients. By evaluating the built ML models, we found that ECFP-LightGBM was the best model to predict amorphization with an accuracy of 92.8%. Furthermore, ECFP-XGBoost was the best in estimating chemical stability with an accuracy of 96.0%. In addition, the feature importance analyses based on SHapley Additive exPlanations (SHAP) and information gain (IG) revealed that several processing parameters and material attributes (i.e., drug loading, polymer ratio, drug's Extended-connectivity fingerprints (ECFP) fingerprints, and polymer's properties) are critical for achieving accurate predictions for the selected models. Moreover, important API's substructures related to amorphization and chemical stability were determined, and the results are largely consistent with the literature. In conclusion, we established the ML models to predict formation of chemically stable ASDs and identify the critical attributes during HME processing. Importantly, the developed ML methodology has the potential to facilitate the product development of ASDs manufactured by HME with a much reduced human workload.

In-line monitoring of solid dispersion preparation in small scale extrusion based on UV-vis spectroscopy

The poor solubility of a large number of active pharmaceutical ingredients (APIs) is a major challenge in pharmaceutical research. Therefore, the extrusion of amorphous solid dispersions (ASDs) is one promising approach to enhance the dissolution rate by molecularly dissolving the API in an amorphous carrier polymer. During ASD extrusion, crucial parameters as the dissolution of the API in the carrier polymer need to be monitored. Within this study, a small scale twin screw extruder was coupled with special ColVisTec UV-vis probes that are characterized by their small dimensions. This setup enables a systematic formulation design and optimization based on in-line monitoring of drug dissolution using small material quantities. In fact, sample quantities of about 5 mg were evaluated for each measurement, representing 50% of the material inside the die. The amount of undissolved drug particles was determined based on the lightness of the extrudates. It was shown that the temperature has a significant effect on the drug dissolution in the polymer. Furthermore, complete drug dissolution was shifted to lower temperatures if higher residence times were applied. Based on the courses of lightness, regime maps were modeled that specify the process conditions where ASDs are successfully manufactured.

Specific mechanical energy - An essential parameter in the processing of amorphous solid dispersions

Specific mechanical energy (SME) is a frequently overlooked but essential parameter of hot-melt extrusion (HME). It can determine whether an amorphous solid dispersion (ASD) can be successfully processed. A minimum combination of thermal input and SME is required to convert a crystalline active pharmaceutical product (API) into its amorphous form. A maximum combination is allowed before it or the carrier polymer chemically degrades. This has important implications on design space. SME input during HME provides information on the totality of the effect of various independent processing parameters such as screw speed, feed rate, and complex viscosity. If only these independent processing parameters are considered separately instead of SME, then important information would be lost regarding the interaction of these parameters and their ability to affect ASD formulation. A complete understanding of the HME process requires an analysis of SME. This paper provides a review of SME use in the pharmaceutical processing of ASDs, the importance of SME in terms of a variety of formulation qualities, and novel future uses of SME. Theoretical background is discussed, along with the relative importance of thermal and mechanical input on various nonsolvent ASD processing methods.

Optimization and Scale-Up for Polymer Extrusion

A review paper is presented on optimization and scale-up for polymer extrusion, both single screw and twin screw extrusion. Optimization consists in obtaining a multidimensional space of process output variables (response surface) on the basis of an appropriate set of input data and searching for extreme values in this space. Scaling consists in changing the scale of the process according to specific criteria, that is, changing the process while maintaining the scaling parameters at a level that is as close to the reference process parameters as possible. It consists in minimizing the differences between the parameters characterizing the reference process and the resulting process. This may be obtained by using optimization techniques leading to the minimization of discrepancies between the parameters of scaled processes. In the paper, it was stated that optimization and scale-up based on process simulation are more effective than those based on experimentation which is time consuming and expensive. The state-of-the-art on extrusion process modeling which is the basis of optimization and scale-up has been presented. Various optimization techniques have been discussed, and the Genetic Algorithms have been identified as powerful and very efficient. Optimization and scale-up based on the process simulation using Genetic Algorithms have been broadly reviewed and discussed. It was concluded that, up to date, there is a lack of optimization studies on the counter-rotating twin screw extrusion, although the global models of this process are known. There is also a lack of process simulation-based scaling-up studies, both on the counter-rotating twin screw extrusion and on the starve fed single screw extrusion. Finally, development perspectives in this field have been discussed.

Quality-by-design in hot melt extrusion based amorphous solid dispersions: An industrial perspective on product development

An industrially feasible approach to overcome the solubility and bioavailability limitations of poorly soluble active pharmaceutical ingredients is the development of amorphous solid dispersions (ASDs) using hot-melt extrusion (HME) technique. The application of Quality by Design (QbD) had a profound impact on the development of HME-based ASDs. The formulation and process optimization of ASDs manufactured via HME techniques require an understanding of critical quality attributes, critical material attributes, critical process parameters, risk assessment tools, and experimental designs. The knowledge gained from each of these QbD elements helps ensure the consistency of product quality. The selection and implementation of appropriate Design of Experiments (DoE) methodology to screen and optimize the formulation and process variables remain a major challenge. This review provides a comprehensive overview on QbD concepts in HME-based ASDs with an emphasis on DoE methodologies. Further, the information provided in this review can assist researchers in selecting a suitable design with optimal experimental conditions. Specifically, this review has focused on the prediction of drug-polymer miscibility, the elements and sequence of QbD, and various screening and optimization designs, to provide insights into the formulation and process variables that are encountered routinely in the production of HME-based ASDs.

Innovations in Thermal Processing: Hot-Melt Extrusion and KinetiSol® Dispersing

Thermal processing has gained much interest in the pharmaceutical industry, particularly for the enhancement of solubility, bioavailability, and dissolution of active pharmaceutical ingredients (APIs) with poor aqueous solubility. Formulation scientists have developed various techniques which may include physical and chemical modifications to achieve solubility enhancement. One of the most commonly used methods for solubility enhancement is through the use of amorphous solid dispersions (ASDs). Examples of commercialized ASDs include Kaletra®, Kalydeco®, and Onmel®. Various technologies produce ASDs; some of the approaches, such as spray-drying, solvent evaporation, and lyophilization, involve the use of solvents, whereas thermal approaches often do not require solvents. Processes that do not require solvents are usually preferred, as some solvents may induce toxicity due to residual solvents and are often considered to be damaging to the environment. The purpose of this review is to provide an update on recent innovations reported for using hot-melt extrusion and KinetiSol® Dispersing technologies to formulate poorly water-soluble APIs in amorphous solid dispersions. We will address development challenges for poorly water-soluble APIs and how these two processes meet these challenges.

Amorphous solid dispersion dry powder for pulmonary drug delivery: Advantages and challenges

Amorphous solid dispersion (ASD) is commonly used in pharmaceutical industry. It has been mainly employed to enhance the oral bioavailability of poorly water-soluble drugs that belong to class II and IV of the biopharmaceutical classification system but has showed promise in other areas of pharmaceutical research. In this review, the potential and limitations of ASD dry powder for inhalation are discussed. ASD powder for inhalation (ASD-IP) is commonly prepared by spray drying technique. The physicochemical characteristics of ASD-IP could be tailored to achieve effective lung deposition. ASD-IP could also attain rapid dissolution behavior to achieve therapeutically effective concentration either locally or systemically before particle clearance in the lung. The key challenges of using ASD powder for inhalation include the possible chemical and/or physical instability of the amorphous phase during manufacturing and in vivo, and the moisture and temperature sensitivity of ASD-IP that affects its storage stability.

Formulation and Evaluation of a Novel Oral Oil-Based Suspension Using Micro-environmental pH-Modifying Solid Dispersion

Drugs with pH-dependent solubility that have poor water solubility can be identified in the drug discovery pipeline. Some of them have poor oral absorption, which can result in insufficient efficacy. Micro-environmental pH-modifying solid dispersion (micro pHm SD) is a promising approach to overcome the poor oral absorption of these drugs. In the present study, toltrazuril (TOL), a weakly acidic drug with poor aqueous and pH-dependent solubility, was used as a model drug. Using micro pHm SD, a novel oral oil-based suspension of TOL SD (TSDS) was developed, and the stability of this formulation was evaluated based on particle size, settling volume ratio, redispersibility, thermal stability, and drug content. The optimized soybean oil-based TSDS (S-TSDS) had high physicochemical stability and good histocompatibility with common inflammatory reactions. The results of the in vitro dissolution analysis showed that S-TSDS rapidly and markedly released the drug and provided higher efficacy and longer persistence against coccidiosis (above 90.9%) in rabbits. This technique could increase the oral absorption and bioavailability of new drug candidates.

In-Line UV-Vis Spectroscopy as a Fast-Working Process Analytical Technology (PAT) during Early Phase Product Development Using Hot Melt Extrusion (HME)

This paper displays the potential of an in-line PAT system for early phase product development during pharmaceutical continuous manufacturing following a Quality by Design (QbD) framework. Hot melt extrusion (HME) is used as continuous manufacturing process and UV⁻Vis spectroscopy as an in-line monitoring system. A sequential design of experiments (DoE) (screening, optimisation and verification) was used to gain process understanding for the manufacture of piroxicam (PRX)/Kollidon® VA64 amorphous solid dispersions. The influence of die temperature, screw speed, solid feed rate and PRX concentration on the critical quality attributes (CQAs) absorbance and lightness of color (L*) of the extrudates was investigated using multivariate tools. Statistical analysis results show interaction effects between concentration and temperature on absorbance and L* values. Solid feed rate has a significant effect on absorbance only and screw speed showed least impact on both responses for the screening design. The optimum HME process conditions were confirmed by 4 independent studies to be 20% w/w of PRX, temperature 140 °C, screw speed 200 rpm and feed rate 6 g/min. The in-line UV-Vis system was used to assess the solubility of PRX in Kollidon® VA64 by measuring absorbance and L* values from 230 to 700 nm. Oversaturation was observed for PRX concentrations higher than 20% w/w. Oversaturation can be readily identified as it causes scattering in the visible range. This is observed by a shift of the baseline in the visible part of the spectrum. Extrudate samples were analyzed for degradation using off-line High-Performance Liquid Chromatography (HPLC) standard methods. Results from off-line experiments using differential scanning calorimetry (DSC), and X-ray diffraction (XRD) are also presented.