(334j) Impact of Oleic Acid, the Degradation Product of the Excipient Polysorbate 80, on the Interfacial Composition in High Concentration Monoclonal Antibody Formulations

The adsorption of monoclonal antibodies (mAbs) to air/water interfaces is a well-recognized pathway for aggregation and particle formation in therapeutic protein formulations. Surfactants such as polysorbate 80 (PS80) are commonly employed as excipients to mitigate this risk by preferentially occupying the air–water interface. However, in high-concentration protein formulations, PS80 is more susceptible to enzymatic degradation, leading to the release of surface-active fatty acid byproducts such as oleic acid (OA). Despite the wide-spread use of PS80 as an excipient, the interfacial role of OA in the competitive adsorption of PS80 and mAb remains poorly characterized. In this study, we investigate how OA influences interfacial composition and competitive adsorption in monoclonal antibody (mAb) formulations across a range of polysorbate 80 (PS80) concentrations.

First, in separate experiments of mixtures of only PS80 and OA, when PS80 is above its critical micelle concentration (CMC), the PS80 micelles accommodate OA added to the solution to form mixed PS80-OA micelles. These mixed micelles adsorb to the air/water interface, forming a mixed monolayer that significantly lowers the equilibrium surface tension relative to solutions of only PS80. In addition, for fixed PS80 concentration above the CMC, the rate of tension reduction increases with an increase in the OA concentration. X-ray reflectivity measurements confirm the monolayers consist of both PS80 and OA, with the OA composition increasing with its bulk concentration.

In mixtures of mAb and only PS80, a critical concentration exists for which the interface is “protected” from mAb adsorption, i.e. the dynamic and equilibrium tensions of the mixture are identical to the PS80 only solutions. When OA is added to these already protecting formulations, surface tension and x-ray reflectivity measurements confirm the interface remains protected with mixed monolayers of PS80 and OA. Importantly, the addition of OA to the protecting PS80 formulation allows for more rapid reductions in tension.

In pharmaceutical practice, the PS80 enzymatically degrades in-situ. We examine the case in which for a given mAb concentration, the PS80 concentration initially protects the interface from mAb adsorption. To simulate degradation, we examine mixtures with increasingly lower concentrations of PS80 and increasingly higher concentration of OA. We find that the presence of OA, even for reducing concentrations of PS80, continues to protect the surface. However, at a critical mixture concentration, the PS80/OA mixture cannot protect the interface from mAb adsorption. These measurements of loss of protection provide a guide for the initial concentrations of PS80 necessary to protect the interface over extended times of degradation. The findings underscore the need to account for PS80 degradation products in the design of stable, high-concentration therapeutic formulations.