Impact of microcrystalline cellulose material attributes: a case study on continuous twin screw granulation

Systematic investigation of the impact of screw elements in continuous wet granulation

Twin-screw wet granulation (TSG) is a continuous manufacturing technique either for granules as final dosage form or as an intermediate before tableting or capsule filling. A comprehensive process understanding is required to implement TSG, considering various parameters influencing granule and tablet quality. This study investigates the impact of screw configuration on granule properties followed by tableting, using a systematic approach for lactose-microcrystalline cellulose (lactose-MCC) and ibuprofen-mannitol (IBU) formulations. The most affecting factor, as observed by other researchers, was the L/S ratio impacting the granule size, strength and tabletability. Introducing tooth-mixing-elements at the end of the screw, as for the IBU formulation, resulted in a high proportion of oversized granules, with values between 36% and 78%. Increasing the thickness of kneading elements (KEs) produced denser, less friable granules with reduced tablet tensile strength. Granulation with more KEs, larger thickness or stagger angle increased torque values and residence time from 30 to 65 s. Generally, IBU granules exhibited high tabletability, requiring low compression pressure for sufficient tensile strength. At a compression pressure of 50 MPa, IBU tablets where at least one kneading zone was included resulted in approximately 2.5 MPa compared to lactose-MCC with 0.5 MPa. In conclusion, the TSG process demonstrated robustness by varying the screw design with minimal impact on subsequent tableting processes.

Impact of surfactant raw material variability on extrudate clarity appearance (transparency) in HME continuous manufacturing

The appearance of an extrudate formulation was monitored during hot-melt extrusion (HME) continuous manufacturing over 3 days. The formulation matrix consisted of a polymeric component, copovidone, and a low molecular weight surfactant, polysorbate 80. Based on studies prior to the continuous manufacturing, the desired appearance of the target extrudate is translucent. Although process parameters such as feed rate and screw speed were fixed during the continuous manufacturing, the extrudate appearance changed over time from turbid to translucent. For root-cause investigation, the extrudates were analyzed offline by differential scanning calorimetry (DSC) and advanced polymer chromatography (APC™). Although the polysorbate 80 content of both turbid and translucent extrudates was within target, the glass transition temperature of the turbid extrudate was 2 °C above expected value. The observed turbidity was traced to lot-to-lot variability of the polysorbate 80 used in the continuous manufacturing, where APC™ analysis revealed that the relative content of the low molecular weight component varied from 23% to 27% in correlation with the evolution from turbid to translucent extrudates. This work stresses the importance of taking feeding material variability into account during continuous manufacturing.

Cracking the code: Spatial heterogeneity as the missing piece for modeling granular fluidized bed drying

Pharmaceutical twin-screw wet granulation is a multifaceted and intricate process pivotal to drug product development. Accurate modeling of this process is indispensable for optimizing manufacturing parameters and ensuring product quality. The fluid bed dryer, an integral component of this granulation process, significantly influences the granular critical quality attributes. This study builds upon prior research by integrating experimental findings on granule segregation during fluid bed drying into an existing compartmental model, enhancing its predictive capabilities. An additional model layer on granule segregation behavior is composed and integrated into the existing model structure in this study. The added model compartment describes probability distributions on the vertical position of granules within each granule size class considered. To beware of overfitting, predictions of both the moisture content after drying and the granule bed temperature throughout drying are discussed in this study relative to experimental data from earlier published studies. These independent analyses demonstrated a marked improvement in prediction accuracy compared to earlier published model structures. The refined model accurately predicts the residual moisture content after drying for an untrained formulation. Moreover, it simultaneously makes accurate predictions of the granular bed temperature, which emboldens its structural correctness. This advancement makes it a powerful tool for predicting the behavior of the pharmaceutical fluid bed drying, which holds significant promise to facilitate pharmaceutical product development.

Validation of model-based design of experiments for continuous wet granulation and drying

This paper presents an application case of model-based design of experiments for the continuous twin-screw wet granulation and fluid-bed drying sequence. The proposed framework consists of three previously developed models. Here, we are testing the applicability of previously published unit operation models in this specific part of the production line to a new active pharmaceutical ingredient. Firstly, a T-shaped partial least squares regression model predicts d-values of granules after wet granulation with different process settings. Then, a high-resolution full granule size distribution is computed by a hybrid population balance and partial least squares regression model. Lastly, a mechanistic model of fluid-bed drying simulates drying time and energy efficiency, using the outputs of the first two models as a part of the inputs. In the application case, good operating conditions were calculated based on material and formulation properties as well as the developed process models. The framework was validated by comparing the simulation results with three experimental results. Overall, the proposed framework enables a process designer to find appropriate process settings with a less experimental workload. The framework combined with process knowledge reduced 73.2% of material consumption and 72.3% of time, especially in the early process development phase.

Exploring the effect of raw material properties on continuous twin-screw wet granulation manufacturability

Twin-screw wet granulation (TSWG) stands out as a promising continuous alternative to conventional batch fluid bed- and high shear wet granulation techniques. Despite its potential, the impact of raw material properties on TSWG processability remains inadequately explored. Furthermore, the absence of supportive models for TSWG process development with new active pharmaceutical ingredients (APIs) adds to the challenge. This study tackles these gaps by introducing four partial least squares (PLS) models that approximate both the applicable liquid-to-solid (L/S) ratio range and resulting granule attributes (i.e., granule size and friability) based on initial material properties. The first two PLS models link the lowest and highest applicable L/S ratio for TSWG, respectively, with the formulation blend properties. The third and fourth PLS models predict the granule size and friability, respectively, from the starting API properties and applied L/S ratio for twin-screw wet granulation. By analysing the developed PLS models, water-related material properties (e.g., solubility, wettability, dissolution rate), as well as density and flow-related properties (e.g., flow function coefficient), were found to be impacting the TSWG processability. In addition, the applicability of the developed PLS models was evaluated by using them to propose suitable L/S ratio ranges (i.e., resulting in granules with the desired properties) for three new APIs and related formulations followed by an experimental validation thereof. Overall, this study helped to better understand the effect of raw material properties upon TSWG processability. Moreover, the developed PLS models can be used to propose suitable TSWG process settings for new APIs and hence reduce the experimental effort during process development.

Pharmaceutical Application of Process Understanding and Optimization Techniques: A Review on the Continuous Twin-Screw Wet Granulation

Twin-screw wet granulation (TSWG) is a method of continuous pharmaceutical manufacturing and a potential alternative method to batch granulation processes. It has attracted more and more interest nowadays due to its high efficiency, robustness, and applications. To improve both the product quality and process efficiency, the process understanding is critical. This article reviews the recent work in process understanding and optimization for TSWG. Various aspects of the progress in TSWG like process model construction, process monitoring method development, and the strategy of process control for TSWG have been thoroughly analyzed and discussed. The process modeling technique including the empirical model, the mechanistic model, and the hybrid model in the TSWG process are presented to increase the knowledge of the granulation process, and the influence of process parameters involved in granulation process on granule properties by experimental study are highlighted. The study analyzed several process monitoring tools and the associated technologies used to monitor granule attributes. In addition, control strategies based on process analytical technology (PAT) are presented as a reference to enhance product quality and ensure the applicability and capability of continuous manufacturing (CM) processes. Furthermore, this article aims to review the current research progress in an effort to make recommendations for further research in process understanding and development of TSWG.

Evaluation of the influence of material properties and process parameters on granule porosity in twin-screw wet granulation

In recent years, continuous twin-screw wet granulation (TSWG) is gaining increasing interest from the pharmaceutical industry. Despite the many publications on TSWG, only a limited number of studies focused on granule porosity, which was found to be an important granule property affecting the final tablet quality attributes, e.g. dissolution. In current study, the granule porosity along the length of the twin-screw granulator (TSG) barrel was evaluated. An experimental set-up was used allowing the collection of granules at the different TSG compartments. The effect of active pharmaceutical ingredient (API) properties on granule porosity was evaluated by using six formulations with a fixed composition but containing APIs with different physical-chemical properties. Furthermore, the importance of TSWG process parameters liquid-to-solid (L/S) ratio, mass feed rate and screw speed for the granule porosity was evaluated. Several water-related properties as well as particle size, density and flow properties of the API were found to have an important effect on granule porosity. While the L/S ratio was confirmed to be the dictating TSWG process parameter, granulator screw speed was also found to be an important process variable affecting granule porosity. This study obtained crucial information on the effect of material properties and process parameters on granule porosity (and granule formation) which can be used to accelerate TSWG process and formulation development.

Considering Inelasticity in the Real-Time Monitoring of Particle Size for Twin-Screw Granulation via Acoustic Emissions

A recently developed process analytical technology (PAT) using artificial intelligence to form the framework of its model, combining frequency-domain acoustic emissions (AE) and elastic impact mechanics to accurately predict complex particle size distributions (PSD) in real-time. This model was modified in this study to give more accurate predictions for the more highly cohesive granules typical of pharmaceutical solid oral dosage formulations. AE spectra were collected from the granulated impacts of various formulations with ranging characteristics from largely elastic to highly inelastic collision responses. A viscoelastic (Hertzian spring-dashpot) and elastoplastic (Walton-Braun) contact force model were compared to understand how these different micro-mechanical approaches would affect the prediction accuracy of particle sizes relevant to granulation. Retraining the artificial intelligence model with the Walton-Braun transformation and a more comprehensive dataset of AE spectra spanning a broad range of granulated formulations showed the prediction error drop to as low as 2% compared to the original elastic version showing errors as large as 18.6% with representative formulations of the industry. The improved PAT shows good applicability to monitoring bimodal PSD that are typical of continuous twin-screw granulation.

Direct Tableting on a Continuous Manufacturing Line-Impact of Mixing Parameters, Material Densities, and Drug Load on Subsequent Process Parameters and Tablet Quality

The continuous manufacturing (CM) of solid oral dosage forms has received increased attention in recent years and has become a leading technology in the pharmaceutical industry. A model has been developed based on process data from two design of experiments (DoEs), where the impact of the mixer process parameters, throughput (THR), hold up mass (HUM), impeller speed (IMP), and the input raw material bulk density (BD_i), on the continuous process and the resulting drug product has been investigated. These statistical models revealed equations, describing process parameter interactions for optimization purposes. For the exit valve opening width (EV) at the bottom of the continuous mixer (CMT), the combination of high throughput (30 kg/h) and low impeller speed (300 rpm) resulted in optimal process conditions. Apparent bulk density of the blend (BD) within the process, fill depth (FD), and tensile strength (TS) were mainly impacted by input bulk density (BD_i) of the tableting mixture, emphasizing the role of material attributes on the continuous manufacturing process. The apparent bulk density itself was, other than from the input bulk density, equally dependent from THR and IMP in opposite deflections. However, process parameters (THR and IMP) revealed a minor impact on the apparent BD compared to the input bulk density. FD was impacted mainly by THR ahead of IMP and the TS by IMP and THR to a similar extend, in opposite deflections. A simplified linear model to estimate the input bulk density revealed satisfactory prediction quality when included in the derived statistical model equations.

Faster to First-time-in-Human: Prediction of the liquid solid ratio for continuous wet granulation

In early development, when active pharmaceutical ingredient (API) is in short supply, it would be beneficial to reduce the number of experiments by predicting a suitable L/S ratio before starting the product development. The aim of the study was to decrease development time and the amount of API needed for the process development of high drug load formulations for continuous twin-screw wet granulation (TSWG). Mixer torque rheometry was used as a pre-formulation tool to predict the suitable L/S ratios for granulation experiments. Three different values that were based on the MTR curves, were determined and assessed for their ability to predict the suitable L/S ratio for TSWG. Three APIs (allopurinol, paracetamol and metformin HCl) were used as model substances in high drug load formulations containing 60% drug substance. The MCC-mannitol ratio was varied to assess the optimal composition for the high-dose formulations. The API solubility affected the mixer torque rheometer (MTR) curves and the optimum L/S ratio for TSWG. The highly soluble metformin needed a much lower L/S ratio compared with allopurinol and paracetamol. A design space was determined for each API based on granule flowability and tablet tensile strength. The flowability of the granules and tensile strength of the tablets improved with an increasing L/S ratio. The MCC-mannitol filler ratio had a significant effect on tabletability for paracetamol and metformin, and these APIs having poor compaction properties needed higher MCC ratios to achieve the 2 MPa limit. The MCC-mannitol ratio had no effect on the granule flow properties. Instead, API properties had the largest influence on both granule flow properties and tensile strength. Based on this study, both the L/S ratio and MCC-mannitol ratio are crucial in controlling the critical quality attributes in high drug load formulations processed by TSWG. The optimum flow and tablet mechanical properties were achieved when using 75:25 MCC-mannitol ratio. Both start of the slope and 2/3 of the L/S ratio at the maximum torque in MTR provided a solid guideline to aim for in a TSWG experiment.

A scaled down method for identifying the optimum range of L/S ratio in twin screw wet granulation using a regime map approach

Twin screw wet granulation (TSWG) has gained momentum in the pharmaceutical industry for effective continuous granulation of solid dosage products. Liquid-to-solid (L/S) ratio is a key process parameter affecting granule properties. Identifying an optimum range of L/S ratio while reducing the number of full scale experiments can minimize material requirements and streamline formulation and process development. In this work, microcrystalline cellulose-based (MCC) formulations of varying drug loads were granulated using a kneading element screw configuration at a wide range of L/S ratios until pasting was visually determined. Quantitative criteria based on process relevant granule size and mass % of fines were established to identify undesirable granulation conditions. Key mechanical properties of wet compacts measured using a small scale approach are discussed. The stress-strain behavior is used to predict pasting, and natural strain at peak yield stress and total work of deformation are used to identify undergranulation and overgranulation respectively. The small scale method is used to establish viable ranges of L/S ratios in advance of at-scale experiments. A quantitative predictive growth regime map is proposed based fully on small scale experiments and input process parameters. Strategies for establishing a generalized growth regime map for various systems of interest are discussed.

In-Depth Understanding of Granule Compression Behavior under Variable Raw Material and Processing Conditions

Tablet manufacturing involves the processing of raw materials through several unit operations. Thus, the mitigation of input-induced variability should also consider the downstream processability of intermediary products. The objective of the present work was to study the effect of variable raw materials and processing conditions on the compression properties of granules containing two active pharmaceutical ingredients (APIs) and microcrystalline cellulose. Differences in compressibility and tabletability of granules were highlighted in function of the initial particle size of the first API, granule polydispersity and fragmentation. Moreover, interactions were underlined with the atomizing pressure. Changing the supplier of the second API was efficiently controlled by adapting the binder addition rate and atomizing pressure during granulation, considering the starting crystal size. By fitting mathematical models on the available compression data, the influence of diluent source on granule compactibility and tabletability was identified. These differences resumed to the ease of compaction, tableting capacity and pressure sensitivity index due to variable water binding capacity of microcrystalline cellulose. Building the design space enabled the identification of suitable API types and the appropriate processing conditions (spray rate, atomizing pressure, compression force) required to ensure the desired tableting performance.

Continuous Twin Screw Granulation: A Review of Recent Progress and Opportunities in Formulation and Equipment Design

Continuous twin screw wet granulation is one of the key continuous manufacturing technologies that have gained significant interest in the pharmaceutical industry as well as in academia over the last ten years. Given its considerable advantages compared to wet granulation techniques operated in batch mode such as high shear granulation and fluid bed granulation, several equipment manufacturers have designed their own manufacturing setup. This has led to a steep increase in the research output in this field. However, most studies still focused on a single (often placebo) formulation, hence making it difficult to assess the general validity of the obtained results. Therefore, current review provides an overview of recent progress in the field of continuous twin screw wet granulation, with special focus on the importance of the formulation aspect and raw material properties. It gives practical guidance for novel and more experienced users of this technique and highlights some of the unmet needs that require further research.

Continuous twin screw granulation: Impact of microcrystalline cellulose batch-to-batch variability during granulation and drying - A QbD approach

Despite significant advances in the research domain of continuous twin screw granulation, limited information is currently available on the impact of raw material properties, especially considering batch-to-batch variability. The importance of raw material variability and subsequent mitigation of the impact of this variability on the manufacturing process and drug product was recently stressed in the Draft Guidance for Industry on Quality Considerations for Continuous Manufacturing by the U.S. Food and Drug Administration (FDA). Therefore, this study assessed the impact of microcrystalline cellulose (MCC) batch-to-batch variability and process settings in a continuous twin screw wet granulation and semi-continuous drying line. Based on extensive raw material characterization and subsequent principal component analysis, raw material variability was quantitatively introduced in the design of experiments approach by means of t1 and t2 scores. L/S ratio had a larger effect on critical granule attributes and processability than screw speed and drying time. A large impact of the t1 and t2 scores was found, indicating the importance of raw material attributes. For the studied formulation, it was concluded that MCC batches with a low water binding capacity, low moisture content and high bulk density generated granules with the most desirable quality attributes. Additionally, an innovative and quantitative approach towards mitigating batch-to-batch variability of raw materials was proposed, which is also applicable for additional excipients and APIs.

The Influence of Equipment Design and Process Parameters on Granule Breakage in a Semi-Continuous Fluid Bed Dryer after Continuous Twin-Screw Wet Granulation

The drying unit of a continuous from-powder-to-tablet manufacturing line based on twin-screw granulation (TSG) is a crucial intermediate process step to achieve the desired tablet quality. Understanding the size reduction of pharmaceutical granules before, during, and after the fluid bed drying process is, however, still lacking. A first major goal was to investigate the breakage and attrition phenomena during transport of wet and dry granules, the filling phase, and drying phase on a ConsiGma-25 system (C25). Pneumatic transport of the wet granules after TSG towards the dryer induced extensive breakage, whereas the turbulent filling and drying phase of the drying cells caused rather moderate breakage and attrition. Subsequently, the dry transfer line was responsible for additional extensive breakage and attrition. The second major goal was to compare the influence of drying air temperature and drying time on granule size and moisture content for granules processed with a commercial-scale ConsiGma-25 system and with the R&D-scale ConsiGma-1 (C1) system. Generally, the granule quality obtained after drying with C1 was not predictive for the C25, making it challenging during process development with the C1 to obtain representative granules for the C25.

Pharmaceutical application of multivariate modelling techniques: a review on the manufacturing of tablets

The tablet manufacturing process is a complex system, especially in continuous manufacturing (CM). It includes multiple unit operations, such as mixing, granulation, and tableting. In tablet manufacturing, critical quality attributes are influenced by multiple factorial relationships between material properties, process variables, and interactions. Moreover, the variation in raw material attributes and manufacturing processes is an inherent characteristic and seriously affects the quality of pharmaceutical products. To deepen our understanding of the tablet manufacturing process, multivariable modeling techniques can replace univariate analysis to investigate tablet manufacturing. In this review, the roles of the most prominent multivariate modeling techniques in the tablet manufacturing process are discussed. The review mainly focuses on applying multivariate modeling techniques to process understanding, optimization, process monitoring, and process control within multiple unit operations. To minimize the errors in the process of modeling, good modeling practice (GMoP) was introduced into the pharmaceutical process. Furthermore, current progress in the continuous manufacturing of tablets and the role of multivariate modeling techniques in continuous manufacturing are introduced. In this review, information is provided to both researchers and manufacturers to improve tablet quality.

Continuous twin screw granulation and fluid bed drying: A mechanistic scaling approach focusing optimal tablet properties

This study provides the results of investigation on scaling approaches for three differently-sized continuous granulation lines, each consisting of a twin screw wet granulation process and a continuous fluid bed drying process. To check the initial scaling approach with regard to granule and tablet properties, a process parameter Design of experiment (DoE) was performed on each of the three equipment scales. The processed formulation did not contain cellulose to allow a high overall flowrate through the directly connected granulation and drying sections. Enhanced scaling aspects showed the influence of Froude number [-] at different twin screw granulator scales and screw speeds on the overgranulated particle fraction [% (V/V] as well as on the scale-dependent drying performance of the continuous fluid bed dryers. Scale-independent, specification limits of the two granule material attributes particle fine fraction [%] and residual water content [%] could be defined, resulting in high tableting performance in terms of tabletability and compressibility. Based on these specification limits and the statistical evaluation of the process parameter DoE, a process design space for the continuous granulation and drying process for each scale was calculated. It came up, that this process design space was decreasing in range with increasing equipment scale. The applicability of the presented scaling approach in terms of granule and tablet properties could successfully be demonstrated by three control experiments performed on the different equipment scales. In sum, this work delivers a basis for a smooth transition of scales within process development on the investigated continuous twin screw granulation and drying lines.

Continuous twin screw granulation: Robustness of lactose/MCC-based formulations

In recent years, significant progress has been made in the field of continuous twin screw granulation. However, only limited knowledge is currently available on the impact of active pharmaceutical ingredient (API) properties on granule quality and processability. In this study, the response behavior of four formulations containing APIs (5-10% drug load) with diverse characteristics was compared to the behavior of the corresponding placebo formulation consisting of lactose, microcrystalline cellulose (MCC) and hydroxypropylmethylcellulose (HPMC). API selection was based on extensive material characterization, combining conventional testing with in silico descriptors. For each formulation, a design of experiments was set up, evaluating the impact of liquid to solid (L/S) ratio and screw speed. Response ranges, response behavior and processability of each of the four formulations proved very similar to the placebo formulation when an appropriate center point L/S ratio was chosen. Hence, this robust placebo formulation could prove useful by decreasing drug product development time and consequently providing patients with a faster access to innovative medicine. Additionally, APIs with similar properties exhibited highly comparable response behavior at similar L/S ratios, indicating the potential use of surrogate APIs in novel drug product development.

Delta-mannitol to enable continuous twin-screw granulation of a highly dosed, poorly compactable formulation

In current study, it was investigated if the moisture-mediated polymorphic transition from δ- to β-mannitol during twin screw granulation (TSG) also took place in high drug loaded formulations and if the specific granule morphology associated with the polymorphic transition could enable tableting of granules comprising 75% paracetamol, a poorly compactable drug. Experiments were performed on an integrated continuous manufacturing line, including a twin screw granulator, fluid bed dryer, mill and tablet press. The polymorphic transition of δ- to β-mannitol was observed during twin screw granulation and granules exhibited the needle-shaped morphology, typical of this transition. TSG at low liquid-to-solid (L/S) ratios and use of polyvinylpyrrolidone or hydroxypropylmethylcellulose as binders inhibited the polymorphic transition, whereas screw speed, drying time, drying temperature and airflow did not affect the solid state of mannitol in the granules. Without binder and despite the high paracetamol drug load in the formulation, limited breakage and attrition was observed during drying and milling. In contrast to granules manufactured from a formulation containing paracetamol/β-mannitol which could not be tableted due to extensive capping, granules prepared from a paracetamol/δ-mannitol formulation showed good tabletability. In conclusion, δ-mannitol is a promising TSG excipient, especially for high drug-loaded formulations with poor tabletability.

Recent progress in continuous manufacturing of oral solid dosage forms

Continuous drug product manufacturing is slowly being implemented in the pharmaceutical industry. Although the benefits related to the quality and cost of continuous manufacturing are widely recognized, several challenges hampered the widespread introduction of continuous manufacturing of drug products. Current review presents an overview of state-of-the art research, equipment, process analytical technology implementations and advanced control strategies. Additionally, guidelines and regulatory viewpoints on implementation of continuous manufacturing in the pharmaceutical industry are discussed.

Continuous twin screw granulation: Influence of process and formulation variables on granule quality attributes of model formulations

In recent years, continuous manufacturing techniques, such as twin screw wet granulation, have gained significant momentum. Due to the large diversity of the (model) formulations and equipment, it is often difficult to generalize conclusions about the importance of process settings. As only limited knowledge is available on the importance of formulation variables, this study focused on the systematic quantification of both process as formulation effects on critical quality attributes of granules from several model formulations. Apart from conventional process and formulation variables, also non-conventional process factors such as nozzle diameter, nozzle orientation and inclusion of a new type of size control elements were evaluated using a Plackett-Burman screening design. Although effects were often formulation-dependent, liquid-to-solid ratio proved the most influential variable for all formulations. Furthermore, binder concentration had a clear effect on granule characteristics, whereas barrel fill level and barrel temperature were less influential. The novel type of size control elements improved granule size distribution and density. The impact of nozzle diameter and wet binder addition proved negligible towards granule properties. Overall it was apparent that lactose/MCC-based formulations correlated better than lactose-based formulations, indicating the possible process robustness of the first filler combination to accommodate API and excipient variability and to handle APIs with different characteristics.

Heat Transfer Evaluation During Twin-Screw Wet Granulation in View of Detailed Process Understanding

During the last decade, the pharmaceutical industry has shown a growing interest in continuous twin-screw granulation (TSG). Despite flourishing literature on TSG, limited studies focused on fundamental process understanding on its mechanisms. In current study, granule quality attributes along the length of the TSG barrel were evaluated together with heat transfer in order to achieve a more fundamental understanding of the granulation process. An experimental setup was developed allowing the collection of granules at the different TSG compartments. In addition to the determination of typical granule attributes, mechanical energy, barrel and granule temperature (measured using an in-line implemented infra-red camera) were measured to evaluate heat transfer occurring at the different compartments and to relate them to granulation mechanisms. Collected data identified wetting enthalpy and friction forces as the main sources of heat along the granulator length. Wetting occurred in the wetting zone and generated temperature increase depending on liquid-to-solid ratio and powder wettability. In the kneading zones, granule temperature increase was proportional to mechanical energy. While it is usually admitted that granule consolidation and reshaping are the consequence of the high shear experienced by the granules, it was highlighted that most of the mechanical energy is converted into thermal energy with no correlation between mechanical energy and granule size distribution. Combined mass and energy balance of the granulation process are therefore necessary to capture the interaction between granule properties and physico-chemical and mechanical phenomena occurring in each compartment.

Managing active pharmaceutical ingredient raw material variability during twin-screw blend feeding

Continuous powder feeding is a critical step in continuous manufacturing of solid dosage forms, as this unit operation should ensure the mass flow consistency at the desired powder feed rate to guarantee the process throughput and final product consistency. In this study, twin-screw feeding of a pharmaceutical formulation (i.e., blend) existing of a highly dosed very poorly flowing active pharmaceutical ingredient (API) leading to insufficient feeding capacity was investigated. Furthermore, the API showed very high batch-to-batch variability in raw material properties dominating the formulation blend properties. Formulation changes were evaluated to improve the flowability of the blends and to mitigate the impact of API batch-to-batch variability on the twin-screw feeding. Herewith, feeding evaluation tests and an extensive material characterization of the reformulated blends were performed to assess the impact of the formulation changes upon continuous twin-screw feeding. The transfer of the glidant from extra-granular to intra-granular phase allowed to improve the flowability of the blends. A sufficient feeding capacity for the downstream process and a mitigation of the impact of batch-to-batch variability of the API upon twin-screw feeding of the blends could be achieved. No effect of the formulation or of the API properties on the feeding stability was observed. The material characterization of the blends allowed identifying the material attributes which were critical for continuous twin-screw feeding (i.e., bulk density, mass charge and powder cohesiveness).

Twin Screw Granulation: Effects of Properties of Primary Powders

Lactose and mannitol are some of the most commonly used powders in the pharmaceutical industry. The limited research published so far highlights the effects of process and formulation parameters on the properties of the granules and the tablets produced using these two types of powders separately. However, the comparison of the performance of these two types of powders during twin screw wet granulation has received no attention. The present research is focused on understanding the granulation mechanism of different grades of two pharmaceutical powders with varying properties (i.e., primary particle size, structure, and compressibility). Three grades each of lactose and mannitol were granulated at varying liquid to solid ratios (L/S) and screw speed. It was noticed that primary powder morphology plays an important role in determining the granule size and structure, and tablet tensile strength. It was indicated that the processed powders such as spray-dried and granulated lactose and mannitol can be used in formulation for wet granulation where flowability of active pharmaceutical ingredient (API) is poor.

A novel approach to support formulation design on twin screw wet granulation technology: Understanding the impact of overarching excipient properties on drug product quality attributes

The overall objective of this work is to understand how excipient characteristics influence the drug product quality attributes and process performance of a continuous twin screw wet granulation process. The knowledge gained in this study is intended to be used for Quality by Design (QbD)-based formulation design and formulation optimization. Three principal components which represent the overarching properties of 8 selected pharmaceutical fillers were used as factors, whereas factors 4 and 5 represented binder type and binder concentration in a design of experiments (DoE). The majority of process parameters were kept constant to minimize their influence on the granule and drug product quality. 27 DoE batches consisting of binary filler/binder mixtures were processed via continuous twin screw wet granulation followed by tablet compression. Multiple linear regression models were built providing understanding of the impact of filler and binder properties on granule and tablet quality attributes (i.e. 16 DoE responses). The impact of fillers on the granule and tablet responses was more dominant compared to the impact of binder type and concentration. The filler properties had a relevant effect on granule characteristics, such as particle size, friability and specific surface area. Binder type and concentration revealed a relevant influence on granule flowability and friability as well as on the compactability (required compression force during tableting to obtain target hardness). In order to evaluate the DoE models' validity, a verification of the DoE models was performed with new formulations (i.e. a new combination of filler, binder type and binder concentration) which were initially not included in the dataset used to build the DoE models. The combined PCA (principle component analysis)/DoE approach allowed to link the excipient properties with the drug product quality attributes.

Raw material variability of an active pharmaceutical ingredient and its relevance for processability in secondary continuous pharmaceutical manufacturing

Active Pharmaceutical Ingredients (API) raw material variability is not always thoroughly considered during pharmaceutical process development, mainly due to low quantities of drug substance available. However, synthesis, crystallization routes and production sites evolve during product development and product life cycle leading to changes in physical material attributes which can potentially affect their processability. Recent literature highlights the need for a global approach to understand the link between material synthesis, material variability, process and product quality. The study described in this article aims at explaining the raw material variability of an API using extensive material characterization on a restricted number of representative batches using multivariate data analysis. It is part of a larger investigation trying to link the API drug substance manufacturing process, the resulting physical API raw material attributes and the drug product continuous manufacturing process. Eight API batches produced using different synthetic routes, crystallization, drying, delumping processes and processing equipment were characterized, extensively. Seventeen properties from seven characterization techniques were retained for further analysis using Principal Component Analysis (PCA). Three principal components (PCs) were sufficient to explain 92.9% of the API raw material variability. The first PC was related to crystal length, agglomerate size and fraction, flowability and electrostatic charging. The second PC was driven by the span of the particle size distribution and the agglomerates strength. The third PC was related to surface energy. Additionally, the PCA allowed to summarize the API batch-to-batch variability in only three PCs which can be used in future drug product development studies to quantitatively evaluate the impact of the API raw material variability upon the drug product process. The approach described in this article could be applied to any other compound which is prone to batch-to-batch variability.

Implementation of quality by design approach in manufacturing process optimization of dry granulated, immediate release, coated tablets - a case study

The aim of this study was to optimize the process of tablets compression and identification of film-coating critical process parameters (CPPs) affecting critical quality attributes (CQAs) using quality by design (QbD) approach. Design of experiment (DOE) and regression methods were employed to investigate hardness, disintegration time, and thickness of uncoated tablets depending on slugging and tableting compression force (CPPs). Plackett-Burman experimental design was applied to identify critical coating process parameters among selected ones that is: drying and preheating time, atomization air pressure, spray rate, air volume, inlet air temperature, and drum pressure that may influence the hardness and disintegration time of coated tablets. As a result of the research, design space was established to facilitate an in-depth understanding of existing relationship between CPPs and CQAs of intermediate product (uncoated tablets). Screening revealed that spray rate and inlet air temperature are two most important factors that affect the hardness of coated tablets. Simultaneously, none of the tested coating factors have influence on disintegration time. The observation was confirmed by conducting film coating of pilot size batches.

Optimization of critical quality attributes in continuous twin-screw wet granulation via design space validated with pilot scale experimental data

In this study, the influence of key process variables (screw speed, throughput and liquid to solid (L/S) ratio) of a continuous twin screw wet granulation (TSWG) was investigated using a central composite face-centered (CCF) experimental design method. Regression models were developed to predict the process responses (motor torque, granule residence time), granule properties (size distribution, volume average diameter, yield, relative width, flowability) and tablet properties (tensile strength). The effects of the three key process variables were analyzed via contour and interaction plots. The experimental results have demonstrated that all the process responses, granule properties and tablet properties are influenced by changing the screw speed, throughput and L/S ratio. The TSWG process was optimized to produce granules with specific volume average diameter of 150μm and the yield of 95% based on the developed regression models. A design space (DS) was built based on volume average granule diameter between 90 and 200μm and the granule yield larger than 75% with a failure probability analysis using Monte Carlo simulations. Validation experiments successfully validated the robustness and accuracy of the DS generated using the CCF experimental design in optimizing a continuous TSWG process.

Identifying overarching excipient properties towards an in-depth understanding of process and product performance for continuous twin-screw wet granulation

The overall objective of this work is to understand how excipient characteristics influence the process and product performance for a continuous twin-screw wet granulation process. The knowledge gained through this study is intended to be used for a Quality by Design (QbD)-based formulation design approach and formulation optimization. A total of 9 preferred fillers and 9 preferred binders were selected for this study. The selected fillers and binders were extensively characterized regarding their physico-chemical and solid state properties using 21 material characterization techniques. Subsequently, principal component analysis (PCA) was performed on the data sets of filler and binder characteristics in order to reduce the variety of single characteristics to a limited number of overarching properties. Four principal components (PC) explained 98.4% of the overall variability in the fillers data set, while three principal components explained 93.4% of the overall variability in the data set of binders. Both PCA models allowed in-depth evaluation of similarities and differences in the excipient properties.

Continuous manufacturing via hot-melt extrusion and scale up: regulatory matters

Currently, because globalization, the pharmaceutical industry is facing enormous challenges to comply with regulatory matters. Reduced patent life and overall decreased profitability of newly discovered drugs are also forcing the pharmaceutical industry to shorten the drug development time with maximum throughput. Therefore, continuous manufacturing (CM) processes via hot melt extrusion (HME) can be a promising alternative for achieving these goals. HME offers solvent-free green technology with a process that is easy to scale up. Moreover, CM provides better product quality assurance compared with batch processes, with fewer labor costs and shorter time to development. In this review, we primarily focus on various aspects of CM and the emerging application of HME to bridge the current manufacturing gap in pharmaceutical sphere.

How Deformation Behavior Controls Product Performance After Twin Screw Granulation With High Drug Loads and Crospovidone as Disintegrant

This study addresses the quantitative influence of 12 different materials (active pharmaceutical ingredients and excipients as surrogate active pharmaceutical ingredients) on the critical quality attributes of twin screw granulated products and subsequently produced tablets. Prestudies demonstrated the significant influence of the chosen model materials (in combination with crospovidone) on the disintegration behavior of the resulting tablets, despite comparable tablet porosities. This study elucidates possible reasons for the varying disintegration behavior by investigating raw material, granule, and tablet properties. An answer could be found in the mechanical properties of the raw materials and the produced granules. Through compressibility studies, the materials could be classified into materials with high compressibility, which deform rather plastically under compression stress, and low compressibility, which display breakages under compression stress. In general, and apart from (pseudo)-polymorphic transformations, brittle materials featured excellent disintegration performance, even at low resulting tablet porosities <8%, whereas plastically deformable materials mostly did not reveal any disintegration. These findings must be considered in the development of simplified formulations with high drug loads, in which the active pharmaceutical ingredient predominantly defines the deformation behavior of the granule.