Overcoming challenges in co-formulation of proteins with contradicting stability profiles - EPO plus G-CSF

Protein concentration and analyzing charge variants in a co-formulation comprising three monoclonal antibodies: A cation-exchange chromatography approach

In the realm of therapeutic antibodies, co-formulations comprising two or more monoclonal antibodies (mAbs) have emerged as a promising strategy, offering enhanced treatment efficacy, improved efficiency, and prolonged intellectual property protection. These advantages have sparked significant interest among both patients and pharmaceutical companies. However, the quantification and analysis of individual mAbs within such co-formulations pose a substantial challenge due to their similar physicochemical properties. To address this challenge, we introduce a pH gradient cation exchange chromatography (CEX) method designed to effectively separate three mAbs that share significant similarities in molecular weight, structure, and isoelectric points (pIs) etc. This versatile approach not only facilitates the accurate quantification of each mAb's concentration and their respective ratios within the co-formulation, but also allows for the comprehensive characterization of all charge variants present. In the case of a co-formulation containing three antibodies, the developed CEX method demonstrated superior performance compared to other techniques. The method's robustness was further underscored by its qualification parameters, including acceptable precision (RSD ≤ 3 %), accuracy (95 %-115 % recovery), and linearity (R2 > 0.99) across a range of 10 to 30 μg load for each mAb. Moreover, the method has been successfully applied in stability studies to quantitatively analyze individual mAb concentrations within co-formulations, marking a significant advancement in the field. Through this work, we contribute a crucial analytical insight into mAb co-formulations, especially those comprising three or more molecules, underscoring its considerable potential to propel the field of biotherapeutic co-formulations forward.

In Silico and Experimental Evidence for the Stabilization of rhEPO by Glycine, Glutamic Acid and Lysine

The available literature indicates that amino acids can stabilize proteins. Our experimental data demonstrated that lysine and glutamic acid can stabilize recombinant human erythropoietin (rhEPO) at 40°C for at least 1 month, as measured by RP-UPLC. Studies with different excipient concentrations demonstrated optimal concentrations of these amino acids within 10-12 mM. The results suggest that a lower concentration of amino acids may not be sufficient to stabilize formulations, while a higher concentration of amino acids can lead lower stability. In silico studies highlighted the importance of the FA4G4S4 model in experimental glycosylation determination, particularly in glycoprotein analysis. We obtained insights into the interactions between the glycosylated ligands of rhEPO and amino acids, as well as their impact on protein behavior and stability. We observed different interactions between the amino acids glycine, glutamic acid, and lysine and the rhEPO protein using this model in docking experiments. They also made it easier to find specific interaction areas by analyzing ligand‒protein interaction fingerprints (PLIFs). This demonstrated how the ligands bind to the proteins or remain outside their vicinity. Furthermore, this study revealed specific places where ligands and rhEPO residues can interact, which helps us learn more about how they stabilize rhEPO.

Stability Convergence in Antibody Coformulations

Combined administration of antibody therapeutics has proven to be beneficial for patients with cancer or infectious diseases. As a result, there is a growing trend toward multiple antibodies premixed into a single product form and delivered to patients as a fixed-dose coformulation. However, combining antibodies into a single coformulation could be challenging as proteins have the potential to interact and alter their stability and degradation profiles in the mixture, compared to that in isolation. We show that in two specific antibody-antibody coformulations, the more stable antibody component increased the stability of the less stable component, which in return destabilized the more stable component, hence exhibiting an overall convergence of stability in the coformulation.

Stability enhancement in a mAb and Fab coformulation

Multiple therapeutic proteins can be combined into a single dose for synergistic targeting to multiple sites of action. Such proteins would be mixed in dose-specific ratios to provide the correct potency for each component, and yet the formulations must also preserve their activity and keep degradation to a minimum. Mixing different therapeutic proteins could adversely affect their stability, and reduce the shelf life of each individual component, making the control of such products very challenging. In this study, a therapeutic monoclonal antibody and a related Fab fragment, were combined to investigate the impact of coformulation on their degradation kinetics. Under mildly destabilizing conditions, these proteins were found to protect each other from degradation. The protective effect appeared to originate from the interaction of Fab and IgG1 in small soluble oligomers, or through the rapid coalescence of pre-existing monomeric IgG1 nuclei into a dead-end aggregate, rather than through macromolecular crowding or diffusion-limitations.

Room Temperature Intrinsic Emission Ratio of BSA Correlates With Percent Aggregates During Long-Term Storage

Successful formulation development hinges on the ability to screen and identify excipients that stabilize drug products during long-term storage. Biophysical and accelerated stability studies are used to screen for excipients that stabilize protein drug products. However, these studies are not always predictive of aggregation during long-term storage. In this study, we used multivariate experimentation to compare the effectiveness of intrinsic fluorescence and size exclusion chromatography accelerated stability parameters to predict excipients that stabilized bovine serum albumin (BSA) against aggregation on long-term storage at 4 °C. Emission intensity ratio (IR_330/350) data was more sensitive than emission maxima (λ_max) or intensity measurements in identifying significant factors and interactions. We observed the expected inverse correlation between the mid-points of fluorescence thermal transitions (T_ms) and insoluble aggregates at 4 and 40 °C. However, there were positive correlations between T_ms and % aggregates at 4 °C, indicating that if T_m was used as a predictive tool, it would select formulations that promoted soluble aggregates on long-term storage. Ambient temperature IR_330/350 measurements identified excipients that reduced BSA soluble aggregates on long-term storage. The results show ambient temperature emission ratio measurements can be useful for protein formulation development.