Metal-Induced Fatty Acid Particle Formation Resulting from Hydrolytic Polysorbate Degradation.

The occurrence of visible particles over the shelf-life of biopharmaceuticals is considered a potential safety risk for parenteral administration. In many cases, particle formation resulted from the accumulation of fatty acids released by the enzymatic hydrolysis of the polysorbate surfactant by co-purified host cell proteins. However, particle formation can occur before the accumulated fatty acids exceed their expected solubility limit. This early onset of particle formation is driven by nucleation phenomena e.g. the presence of metal cations that promote the formation and growth of fatty acid particles. To further characterize and understand this phenomenon, we assessed the potential of different metal cations to induce fatty acid particle formation using a dynamic light scattering assay. We demonstrated that the presence of trace amounts of multivalent cations, in particular trivalent cations such as aluminum and iron, may act as nucleation seed in the process of particle formation. Finally, we developed a mitigation strategy for metal-induced fatty acid particles that deploys a chelator to reduce the risk of particle formation in biopharmaceutical formulations.

Glass Leachables as a Nucleation Factor for Free Fatty Acid Particle Formation in Biopharmaceutical Formulations.

Surfactants are essential components in protein formulations protecting them against interfacial stress. One of the current industry-wide challenges is enzymatic degradation of parenteral surfactants such as polysorbate 20 (PS20) and polysorbate 80, which leads to the accumulation of free fatty acids (FFAs) potentially forming visible particles over the drug product shelf-life. While the concentration of FFAs can be quantified, the time point of particle formation remains unpredictable. In this work, we studied the influence of glass leachables as nucleation factors for FFA particle formation. We demonstrate the feasibility of nucleation of FFA particles in the presence of inorganic salts like NaAlO2 and CaCl2 simulating relevant glass leachables. We further demonstrate FFA particle formation depending on relevant aluminum concentrations. FFA particle formation was subsequently confirmed with lauric/myristic acid in the presence of different quantities and compositions of glass leachables obtained by several sterilization cycles using different types of glass vials. We further verified the formation of particles in aged protein formulation containing degraded PS20 through the spiking of glass leachables. Particles were characterized as a complex of glass leachables, such as aluminum and FFAs. Based on our findings, we propose a likely pathway for FFA particle formation that considers specific nucleation factors.