(387h) Competitive adsorption between monoclonal antibodies and non-ionic surfactants at the air-water interface

Monoclonal antibodies (mAbs) are attractive forms of therapeutic agents due to their high specificity with antigens. The successful commercial development of a new therapeutic mAb product needs to meet many requirements, such as marketability, safety, administration routes and stability. The stability of mAbs is of critical importance to the end product’s marketability and safety, and research into understanding their stability is ongoing in both industrial and academic environments.[1-3] It is well established that the formation of irreversible mAb aggregates can occur due to surface adsorption and desorption,[4] which is a common occurrence during drug manufacture, shipping, and long-term storage. Further factors that impact formulation stability include the interfacial stresses due to selective adsorption of mAbs at the air-water interface, which is attributed with causing instabilities and aggregation. In industrial formulations, surfactants are regularly incorporated into mAb formulations where they play the role of stabilizer, either by forming mAb-surfactant complexes or through preferential adsorption to hydrophobic interfaces.[5] Two surfactants that are commonly used in mAb formulations are polysorbate 20 (PS20) and polysorbate 80
(PS80). These are highly efficient at protecting mAbs from aggregation at solid-liquid and air-liquid interfaces (requiring [surf] < 0.05% w/v), however these have been reported to degrade via both oxidative and hydrolytic pathways.[6,7] Poloxamer 188 (P188) is also used in therapeutic formulations and is regarded as more stable than the polysorbates, with minimal degradation under relevant storage and formulation conditions. It has been speculated that surfactants prevent mAb precipitation under shearing conditions using cone-and-plate rheometry.[8] However, little is known about how surfactants prevent mAb adsorption at the air-water interface under compression and expansion that occurs frequently during drug product manufacturing and transport. One study has shown that under compression, mAb interfaces that age can crumple and shed off into the bulk solution.[9] A recent study has utilized x-ray reflectivity (XRR) alongside dynamic surface tension measurements to quantify the amount of mAb at an air-water interface when mAb and PS80 were added at the same time, and they found that mAb was still present even when the surface tension of the mixture was equal to that of PS80 alone.[10] However, they did not look at the effect of compression and expansion.

In our work, we have selected two different mAbs. These have been chosen based on different stabilities from long-term stability measurements. One is IgG1 and the other is IgG4 which have different flexibilities due to a different amount of disulfide bonds in the hinge region.[11] Further, we have selected two non-ionic surfactants (PS80 and P188). We have utilized multiple interfacial techniques (dynamic surface tension, interfacial shear rheology, interfacial dilatational rheology, Brewster angle microscopy (BAM)) to investigate these systems (single component or mAb+surfactant) with an aim to further our understanding of competitive adsorption at the air-water interface. A DHR-3 rheometer, equipped with a double wall ring accessory for interfacial rheology, was utilized to monitor the moduli of the mAb monolayers, with and without surfactant. Further, it was also used to determine any impact of the order of addition of each component. It was found that after addition of surfactant, the moduli began to decrease, suggesting either mAb displacement or network disruption. Further, the interfacial shear viscosity decreased by three orders of magnitude. We have investigated the effect of different surfactants and surfactant concentration on
different mAb monolayers at the air-water interface. We have also performed measurements using a Langmuir trough. It was noted that when surfactant is injected into the bulk underneath a mAb monolayer, the surface pressure increases, suggesting surfactant is reaching the interface. However, upon compression the isotherm still shows characteristics of a mAb compression isotherm. Here, we have investigated the effect of order of addition, along with surfactant and mAb type, under compression and expansion conditions. Further, BAM has been utilized alongside the Langmuir trough in efforts to visualize mesoscale interfacial behavior. These results provide guidance on mAb formulation stability.

References
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