Origin of Aggregate Formation in Antibody Crystal Suspensions Containing PEG

Particles in Biopharmaceutical Formulations, Part 2: An Update on Analytical Techniques and Applications for Therapeutic Proteins, Viruses, Vaccines and Cells

Particles in biopharmaceutical formulations remain a hot topic in drug product development. With new product classes emerging it is crucial to discriminate particulate active pharmaceutical ingredients from particulate impurities. Technical improvements, new analytical developments and emerging tools (e.g., machine learning tools) increase the amount of information generated for particles. For a proper interpretation and judgment of the generated data a thorough understanding of the measurement principle, suitable application fields and potential limitations and pitfalls is required. Our review provides a comprehensive overview of novel particle analysis techniques emerging in the last decade for particulate impurities in therapeutic protein formulations (protein-related, excipient-related and primary packaging material-related), as well as particulate biopharmaceutical formulations (virus particles, virus-like particles, lipid nanoparticles and cell-based medicinal products). In addition, we review the literature on applications, describe specific analytical approaches and illustrate advantages and drawbacks of currently available techniques for particulate biopharmaceutical formulations.

On the Aggregation and Nucleation Mechanism of the Monoclonal Antibody Anti-CD20 Near Liquid-Liquid Phase Separation (LLPS)

The crystallization of Anti-CD20, a full-length monoclonal antibody, has been studied in the PEG400/Na2SO4/Water system near Liquid-Liquid Phase Separation (LLPS) conditions by both sitting-drop vapour diffusion and batch methods. In order to understand the Anti-CD20 crystallization propensity in the solvent system of different compositions, we investigated some measurable parameters, normally used to assess protein conformational and colloidal stability in solution, with the aim to understand the aggregation mechanism of this complex biomacromolecule. We propose that under crystallization conditions a minor population of specifically aggregated protein molecules are present. While this minor species hardly contributes to the measured average solution behaviour, it induces and promotes crystal formation. The existence of this minor species is the result of the LLPS occurring concomitantly under crystallization conditions.

Optimization of Vapor Diffusion Conditions for Anti-CD20 Crystallization and Scale-Up to Meso Batch

The crystal form is one of the preferred formulations for biotherapeutics, especially thanks to its ability to ensure high stability of the active ingredient. In addition, crystallization allows the recovery of a very pure drug, thus facilitating the manufacturing process. However, in many cases, crystallization is not trivial, and other formulations, such as the concentrate solution, represent the only choice. This is the case of anti-cluster of differentiation 20 (anti-CD20), which is one of the most sold antibodies for therapeutic uses. Here, we propose a set of optimized crystallization conditions for producing anti-CD20 needle-shaped crystals within 24 h in a very reproducible manner with high yield. High crystallization yield was obtained with high reproducibility using both hanging drop vapor diffusion and meso batch, which is a major step forward toward further scaling up the crystallization of anti-CD20. The influence of anti-CD20 storage conditions and the effect of different ions on the crystallization processes were also assessed. The crystal quality and the high yield allowed the first crystallographic investigation on anti-CD20, which positively confirmed the presence of the antibody in the crystals.