EVALUATING NOVEL ANALYTICAL TECHNIQUES TO ASSESS THE INITIAL STEPS OF PROTEIN AGGREGATION USING VARIOUS ANTIBODY SOLUTIONS

Antibody-based therapeutics continue to be a fast growing field in pharmaceutics due to their increased selectivity for a specific target over small molecule drugs. Antibody solutions are often formulated at high protein concentrations in order to achieve low injection volumes, especially for subcutaneous administration, which can cause many challenging problems when it comes to stabilization. The instability of antibodies can often lead to aggregation which can occur during many parts of the manufacturing process including purification, fill-finish, shipping and storage. Aggregation of antibodies can cause many problems such as not injecting the proper dose, due to a decrease in the protein’s concentration, or causing immunogenic responses that may affect the safety or efficacy of the drug potentially causing harm to patients. Therefore, the aggregation pathway(s) of antibody drug candidates need to be characterized in great detail and well understood before they reach the market. Currently, several common analytical techniques are being used to distinguish the amount and size of aggregation impurities produced when an antibody undergoes accelerated stresses during formulation development. However, more novel techniques are needed to get a better, more in-depth understanding of the types of aggregates formed along of the aggregation pathway. The development of novel techniques to screen antibody stability and aggregation propensities can not only elucidate degradation mechanisms that proteins undergo throughout the lifetime of the drug, it can also allow us to better understand effective ways to increase the shelf-life and maintain product safety. In this study, various monoclonal antibodies (mAb) and bispecific antibodies (biAb) were examined under varying stress conditions and their physical stability monitored using conventional and novel techniques. New techniques examined include a high throughput GroEL-based BLI (Biolayer interferometry) assay that helps identify less stable antibodies, formulations (excipients, pH values), and storage conditions (temperatures) by being able to detect pre-aggregate species forming prior to more established techniques show the formation of larger sized aggregates (methods such as size exclusion chromatography and micro-flow digital imaging). Another novel technique examined in these studies is the use of hydrogen-deuterium exchange mass spectrometry, which is used to identify problematic portions of the antibody molecule, by monitoring changes in local flexibility or rigidity, when exposed to different excipients and pH levels. Finally, the use of Langmuir trough to examine interfacial and intermolecular interaction properties of various antibodies and formulation conditions was evaluated. Understanding antibody molecules tendencies to drive to the air-water interface or have intermolecular interactions can predict physical instability problems throughout the purification process and during long term storage conditions. This type of aggregation risk assessment during early formulation development can decrease the resources spent on protein drug candidates that will be problematic. Each of these novel analytical techniques can increase the understanding of antibody instability issues in solution, and therefore, allow for an increased likelihood of successful drug design and development overall