Challenges for Cell-Based Medicinal Products From a Pharmaceutical Product Perspective.

Advanced therapy medicinal products (ATMPs), such as somatic cell-therapy medicinal products or tissue-engineered products for human use, offer new and potentially curative opportunities to treat yet untreatable diseases or disorders. For cell-therapy medicinal products (CBMPs), multiple stability and quality challenges exist and relate to the cellular composition and unstable nature of these parenteral preparations. It is the aim of this review to discuss open questions and problems associated with the development, manufacturing and testing of CBMPs from a pharmaceutical drug product perspective. This includes safety, storage and handling, particulates, the choice of container closure systems and integrity. Analytical methods commonly used to evaluate the quality of the final CBMP to ensure patient's safety will be discussed. Particulate contamination in final products deserve special attention since CBMPs cannot be sterile filtered. Visible and sub-visible particles may represent environmental contaminations or may form during storage. They may be introduced from processing materials such as single use product contact materials, ancillary materials, or any components such as primary packaging used for the final product. Currently available analytical methods for detecting particulates may not be easily applicable to CBMPs due to their inherent particulate nature and appearance.

Subvisible Particulate Contamination in Cell Therapy Products-Can We Distinguish?

Cell therapy products represent an exciting new class of medicinal products, which must be parenterally administered. Thus, compliance with parenteral preparation guidelines is required. One requirement for parenteral products is the characterization of particle contaminations. As cell-based products are turbid suspensions, containing particles, the cells, characterization and control of foreign particle impurities remain a challenge. Within this study, we evaluated a flow imaging microscopy method for the detection and characterization of subvisible particle contaminations in cell-based products. We found that flow imaging microscopy is a potential method where subvisible particle contaminations can be differentiated from the cells in cell therapy products.

Comparison of ice fog methods and monitoring of controlled nucleation success after freeze-drying.

Improving freeze-drying processes regarding drying time and batch homogeneity is subject of ongoing research work. In this context, controlled nucleation raised great expectations. However, practically we face some challenges, e.g. how to non-destructively monitor successfully performed controlled nucleation. The question if different controlled nucleation methods lead to comparable products, as not every method can easily be implemented in lab and production scale equipment, is also of high interest. Additionally, the optimal nucleation temperature for controlled nucleation is an open question. In our study, we addressed these challenges. We successfully evaluated frequency modulated spectroscopy as a fast and non-destructive method to monitor controlled nucleation success and batch homogeneity. We found that the better homogeneity generated by controlled nucleation during the freezing step did not sustain in the dried product. Lyophilizates produced by three different ice fog methods for controlled nucleation were characterized by comparable specific surface areas but differed in residual moisture content. To investigate the impact of the ice nucleation temperature (TN) on the resulting specific surface area, we performed controlled nucleation at -3 °C and -10 °C. We concluded that TN is not the only specific surface area determining factor and a high TN does not necessarily lead to larger pores but poses a higher risk of not-nucleating vials.

Does controlled nucleation impact the properties and stability of lyophilized monoclonal antibody formulations?

This study provides the first systematic investigation of the impact of the nucleation protocol during freeze-drying on physico-chemical properties and long-term stability of two IgG1 antibodies in sugar formulations. We hypothesized that the lower specific surface area (SSA) generated by controlled nucleation could be beneficial for the stability of interface sensitive proteins. The study compares controlled nucleated (CN) and randomly nucleated (RN) lyophilizates with high and low antibody concentrations stored at different temperatures. Formulations with and without polysorbate (PS) were included. In the "high concentration" study the formulation without PS showed reduced particle formation for CN samples compared to RN samples. PS containing formulations had an overall lower particle level with no further advantage of CN on stability. Besides the intended comparison of CN and RN samples, we observed that PS promoted sucrose crystallization in both low concentration antibody studies during storage. Additionally, our results indicate that the nucleation temperature (TN) was not the only determining factor for the resulting ice crystal size and consequently the product`s SSA. Overall, the application of CN had neither a positive nor a negative impact on the product's physico-chemical stability. The surfactant had a much higher stabilizing effect than the reduction of the SSA by CN.

Evaluation of Heat Flux Measurement as a New Process Analytical Technology Monitoring Tool in Freeze Drying.

This study investigates the suitability of heat flux measurement as a new technique for monitoring product temperature and critical end points during freeze drying. The heat flux sensor is tightly mounted on the shelf and measures non-invasively (no contact with the product) the heat transferred from shelf to vial. Heat flux data were compared to comparative pressure measurement, thermocouple readings, and Karl Fischer titration as current state of the art monitoring techniques. The whole freeze drying process including freezing (both by ramp freezing and controlled nucleation) and primary and secondary drying was considered. We found that direct measurement of the transferred heat enables more insights into thermodynamics of the freezing process. Furthermore, a vial heat transfer coefficient can be calculated from heat flux data, which ultimately provides a non-invasive method to monitor product temperature throughout primary drying. The end point of primary drying determined by heat flux measurements was in accordance with the one defined by thermocouples. During secondary drying, heat flux measurements could not indicate the progress of drying as monitoring the residual moisture content. In conclusion, heat flux measurements are a promising new non-invasive tool for lyophilization process monitoring and development using energy transfer as a control parameter.