(497c) X-Ray Reflectivity and Pendant Drop Tensiometry Measurements of the Competitive Adsorption of Mabs and Excipients at the Air-Water Interface

The adsorption of therapeutic monoclonal antibodies (mAbs) at the air-water interface is central to the production and use of antibody-based pharmaceuticals. Air-water interfaces are generated during the production, processing and storage of therapeutic formulations by pressure driven shear stress or shaking.^1–3 When an air-water interface is created, the antibodies will expose their hydrophobic residues to the gas phase leading to partial unfolding, interfacial aggregation, irreversible adsorption and recruitment of additional proteins from the solution phase.⁴ This leads to decreased yields in production as well as a shortened shelf life of these therapeutic drugs. Furthermore, the adsorption phenomenon will result in the conformational degradation of the antibody, where the loss of secondary and tertiary structure can result in diminished activity and promote immunogenicity, inhibiting the efficacy of the biologic drugs.⁵ In order to solve this problem and enhance the physical stability of therapeutic monoclonal antibodies, the pharmaceutical industry uses a multicomponent formulation that includes surface active excipients.⁶ Excipients are thermodynamically favored over proteins for adsorption at the air-water interface.

The first part of the talk focuses on understanding the nature of single component systems about the reversible/irreversible adsorption for Polysorbate 80 (PS-80) and mAbs in histidine. Pendant bubble tensiometer is used to characterize the equilibrium and dynamic surface tension. Additionally, a double-capillary setup of the pendant drop tensiometer is used to exchange mAb solutions with histidine buffer. X-ray reflectivity is used to measure adsorbed amounts and understand the molecular configurations of the adsorbed molecules. A box-refinement method based on the model independent approach⁷ is used to predict the structural information on an Angstrom scale. The surface activity of the mAb’s is correlated to the hydrophobic patches present on the protein surface using a parameter termed Spatial Aggregation Propensity (SAP).⁸ The second part focuses on the competitive adsorption of the mAb and excipient systems using these same tools.

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