STUDYING SOLUTION SELF-ASSEMBLED MORPHOLOGY AND THERMAL STABILITY OF POLYSORBATE FRACTIONS AND THEIR IMPLICATIONS IN MICELLAR DEGRADATION VIA SMALL ANGLE NEUTRON SCATTERING

摘要

Pharmaceutical industries add excipients in therapeutic protein formulations to stabilize monoclonal antibodies (mAbs) against surface-induced denaturation and aggregation. Excipients such as commercially available polysorbate (PS) 20 and PS 80 can modulate the interfacial behavior of mAbs in solution due to their amphiphilic nature, and thereby enhance long-term stability and storage of therapeutic protein formulations1. Commercially available PSs used in protein formulations are extremely heterogeneous and contain complex molecular entities which mainly comes from different types of fatty acid esters in the hydrophobic chain1. Recent findings in bio-pharmaceutical industries confirm that the structural heterogeneity and manufacturing byproducts make them susceptible to degrade via ester-hydrolysis and auto-oxidation at pharmaceutically relevant conditions12. The possible consequences of such degradation mechanisms are: (1) loss of surfactant functionality due to change in the PS structure in both unimer and micelle (2) accumulation of degradants that can lead to formation of sub-visible and visible particle in therapeutic formulations. These phenomena can severely impact the product quality and produce unwanted immune responses. Furthermore, these degradation mechanisms produce different degradation profiles due to preferential degradation and can respond differently to the assay techniques typically employed by pharmaceutical industries. Therefore, we performed a design of experiments to determine the micellar morphologies of the individual components of PS 20 and PS 80 using small angle neutron scattering (SANS) for comparison to SANS experiments on selectively degraded, commercial PS solutions with the goal of identifying specific components responsible for the properties of the degraded samples. The stability of the components of PS 20 and PS 80 micelles are studied under thermal stress, confirming that PS molecules with two hydrophobic tail groups are more prone to morphology changes leading to solution instability. To understand the mechanistic pathways of PS degradation, we also investigated the solution physiochemical properties and stability of chemically degraded pharmaceutical PS 20 micelles. In conclusion, our study demonstrates morphological changes of the PS components as a function of temperature which can potentially identify the PS components responsible for degradation under thermal stress. The results of this study may facilitate formulating protein therapeutics with better stability profiles.