Scale-up in twin-screw wet granulation: impact of formulation properties.

The focus of this study was to investigate the sensitivity of different drug formulations to differences in process parameters based on previously developed scale-up strategies. Three different formulations were used for scale-up experiments from a QbCon® 1 with a screw diameter of 16 mm and a throughput of 2 kg/h to a QbCon® 25 line with a screw diameter of 25 mm and a throughput of 25 kg/h. Two of those formulations were similar in their composition of excipients but had a different API added to the blend to investigate the effect of solubility of the API during twin-screw wet granulation, while the third formulation was based on a controlled release formulation with different excipients and a high fraction of HPMC. The L/S-ratio had to be set specifically for each formulation as depending on the binder and the overall composition the blends varied significantly in their response to water addition and their overall granulation behavior. Before milling there were large differences in granule size distributions based on scale (Earth Mover's Distance 140-1100 µm, higher values indicating low similarity) for all formulations. However, no major differences in granule properties (e.g. Earth Mover's Distance for GSDs: 23-88 µm) or tablet tensile strength (> 1.8 MPa at a compaction pressure of 200 MPa for all formulations with a coefficient of variation < 0.1, indicating high robustness for all formulations) were observed after milling, which allowed for a successful scale-up independent of the selected formulations.

Comparison of scale-up strategies in twin-screw wet granulation.

The aim of this study was to compare different scale-up strategies in twin-screw wet granulation and investigate the impact of the selected strategy on granule and tablet properties for a defined formulation. For the scale-up, a granulation process was transferred from a QbCon® 1 with a screw diameter of 16 mm to a QbCon® 25 line with a screw diameter of 25 mm. Three different scale-up strategies were introduced based on differences in process parameters and their resulting effects on various aspects. such as the powder feed number as a surrogate for the barrel fill level or the circumferential speed. Both are highly dependent on screw diameter and screw speed (SS), while the barrel fill level also depends on the overall throughput. Granules produced on the larger scale were significantly larger due to the larger gap size in the granulator, however, these differences were eliminated after milling. Despite major differences in powder feed number, circumferential speed, overall throughput and SS, product properties for both tablets and granules were strikingly similar after milling on both scales and with all applied strategies. For the selected formulation the effect of varying liquid to solid ratio at the same scale was much higher than the differences between scale-up strategies. The results of this study are promising for future process scale-up from lab scale to production scale in twin-screw wet granulation, as they are indicating towards a robust granulation process leading to similar tablet properties afterwards.

Model-Guided Development of a Semi-Continuous Drying Process.

INTRODUCTION: With an increased adoption of continuous manufacturing for pharmaceutical production, the ConsiGma® CTL25 wet granulation and tableting line has reached widespread use. In addition to the continuous granulation step, the semi-continuous six-segmented fluid bed dryer is a key unit in the line. The dryer is expected to have an even distribution of the inlet air between the six drying cells. However, process observations during manufacturing runs showed a repeatable pattern in drying time, which suggests a variability in the drying performance between the different cells of the dryer. The aim of this work is to understand the root-cause of this variability. MATERIALS AND METHODS: In a first step, the variability in the air temperature and air flow velocity between the dryer cells was measured on an empty dryer. In a second step, the experimental data were interpreted with the help of results from computational fluid dynamics (CFD) simulations to better understand the reasons for the observed variability. RESULTS: The CFD simulations were used to identify one cause of the measured difference in the air temperature, showing the impact of the air inlet design on the temperature distribution in the dryer. CONCLUSIONS: Although the simulation could not predict the exact temperature, the trend was similar to the experimental observations, demonstrating the added value of this type of simulation to guide process development, engineering decisions and troubleshoot equipment performance variability.

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.

Orthogonal Redundant Monitoring of a New Continuous Fluid-Bed Dryer for Pharmaceutical Processing by Means of Mass and Energy Balance Calculations and Spectroscopic Techniques.

In line with the ongoing shift from batch to continuous pharmaceutical production of solid oral dosage forms, a novel continuous fluid-bed dryer was developed. The forced feed nature of the Glatt GPCG2 CM fluid-bed dryer allows continuous, first-in-first-out drying of wet granulate materials based on its compartmentalized, rotating fluidizing chamber. The presented work aims to introduce the dryer's functionalities in detail, and to demonstrate that the rotating fluid-bed chambers facilitates a stable drying behavior, which ensures robust and repeatable residual moisture contents (loss-on-drying [LOD]) of the discharged granules. Furthermore, a mass and energy balance (MEB) is derived, based on the logged process values of the granulating and drying units. Two independent test experiments demonstrate that precise LOD prediction in real time is achievable by MEB to serve as an orthogonal process analytical technology method to common near-infrared spectroscopy. On average, MEB results differed by 0.36% LOD (absolute) from offline reference analyses, and by 0.61% LOD from predictions made with an in-house available near-infrared spectroscopy method. Furthermore, good correlation between the observed and expected thermal energy loss was found. The derived MEB is solely based on physical principles; hence it is product independent and transferable to other materials that are processed on the described equipment.