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

Powder dosing within continuous manufacturing: A lean approach for gravimetric dosing configuration and equipment selection

This work presents a novel approach to select gravimetric dosing configurations for continuous unit operations in pharmaceutical processing. It optimizes material, time, and personnel use, and allows selections for configurations of materials not included in the model by robust material attribute-based interpolation. The approach does not apply Principal Component Analysis (PCA) and Partial Least Squares (PLS). Instead, a reduced set of material attributes that require measurement was determined from existing material attribute libraries found in literature. Only those identified 17 attributes were measured for 13 materials and employed in this study. The established model proved to be predictive for an even further reduced attribute set of 12 attributes. The model introduces a simplified method for selecting feeding equipment combining precision metrics (relative mean intra-bin variability) and model parameters (fmax, fmin, β). The reduction of Material Attributes (MAs) in this short-cut method enables fast evaluation and enhances resource efficiency by incorporating only a few selected MAs into the model and therefore introduces a different line of thinking. It was also possible to compare feeding of different hopper geometries, showing that flat bottom-hoppers have higher dosing precision than round bottom-hoppers. In conclusion, this work introduces a smart and innovative model that simplifies the equipment selection process and brings objectivity through a comprehensive numerical description of the discharge characteristics, and provides new options for continuous dosing in pharma through combining precision and curve fitting parameters.

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 16mm to a QbCon® 25 line with a screw diameter of 25mm. 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.