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.

Evaluating a Modified High Purity Polysorbate 20 Designed to Reduce the Risk of Free Fatty Acid Particle Formation.

PURPOSE: To evaluate a modified high purity polysorbate 20 (RO HP PS20)-with lower levels of stearate, palmitate and myristate esters than the non-modified HP PS20-as a surfactant in biopharmaceutical drug products (DP). RO HP PS20 was designed to provide functional equivalence as a surfactant while delaying the onset of free fatty acid (FFA) particle formation upon hydrolytic degradation relative to HP PS20. METHODS: Analytical characterization of RO HP PS20 raw material included fatty acid ester (FAE) distribution, higher order ester (HOE) fraction, FFA levels and trace metals. Functional assessments included 1) vial and intravenous bag agitation; 2) oxidation via a placebo and methionine surrogate study; and 3) hydrolytic PS20 degradation studies to evaluate FFA particle formation with and without metal nucleation. RESULTS: Interfacial protection and oxidation propensity were comparable between the two polysorbates. Upon hydrolytic degradation, FFA particle onset was delayed in RO HP PS20. The delay was more pronounced when HOEs of PS20 were preferentially degraded. Furthermore, the hydrolytic degradants of RO HP PS20 formed fewer particles in the presence of spiked aluminum. CONCLUSION: This work highlights the criticality of having tighter control on long chain FAE levels of PS20 to reduce the occurrence of FFA particle formation upon hydrolytic degradation and lower the variability in its onset. By simultaneously meeting compendial PS20 specifications while narrowing the allowable range for each FAE and shifting its composition towards the shorter carbon chain species, RO HP PS20 provides a promising alternative to HP PS20 for biopharmaceutical DPs.