Comparison of the Protective Effect of Polysorbates, Poloxamer and Brij on Antibody Stability Against Different Interfaces

Protein stability and critical stabilizers in frozen solutions

Freezing is a common unit operation during the processing and storage of therapeutic proteins. Upon freezing, protein molecules and other solutes are excluded from the ice crystals, resulting in the formation of freeze concentrated solution (FCS). Protein destabilization can be prevented due to the low temperature and the formation of a viscous FCS. However, the changes in temperature, pH, salt concentration, and the formation of ice-solution interfaces can induce protein destabilization. The current paper reviews the stresses associated with freezing and thawing and discusses the stabilization strategies. At subambient conditions, protein unfolding is thermodynamically favored when the solution is cooled below the cold denaturation temperature. The formation of a viscous FCS, specifically at a temperature below the glass transition temperature (Tg'), immobilizes and stabilizes the proteins. Protein can adsorb at the ice/solution interface, followed by unfolding and aggregation. Therefore, freezing and thawing rates need to be carefully selected to minimize the ice surface area (due to the formation of small ice crystals) and to avoid ice recrystallization. Besides, stabilizers, including sugars, surfactants, and amino acids, are added as stabilizers (cryoprotectants) to prevent protein destabilization upon freezing and frozen storage. In situ spectroscopic (infrared, Raman, and solid-state NMR) and scattering (X-ray and neutron) techniques provide useful insights into protein stability and phase transitions of excipients in frozen solutions. Finally, we discuss the importance of the freezing process and excipient selection in the successful lyophilization of protein formulations. The review paper comprehensively discusses the challenges during the cryopreservation of therapeutic proteins and provides valuable insights into the critical stabilizers in frozen protein solutions.

Impact of protein adsorption during biopharmaceutical manufacture & storage

Protein therapeutics contact multiple interfaces during formulation, filtration, fill-finish, and storage processes. Interactions at these interfaces can compromise the conformational and colloidal stability of therapeutic proteins through surface adsorption, potentially leading to aggregation and particle formation. Surface-induced conformational changes in protein higher-order structures, influenced by interfacial hydrophobicity and charge, are key drivers of these effects. The resulting loss of active protein and increased aggregation risk pose significant challenges to the efficacy and safety of the final biotherapeutic product. Thus, it is imperative to develop strategies that minimize protein-surface interactions that may compromise the protein's conformational and colloidal stability during manufacture and storage. This review focuses on current research related to the adsorption behaviour of biotherapeutics at interfaces encountered during fill-finish and storage. Furthermore, the review introduces the factors influencing protein adsorption and interfacial stability and current methodologies and advancements in mitigating interfacial adsorption, emphasizing rational formulation design strategies.

Evaluation of monoclonal antibody solution propensity for dripping at the filling nozzle tip end

Nonionic surfactants are commonly used as excipients in monoclonal antibody formulations. The interfacial activity of surfactants may contribute to the elongation of solution droplets at the filling nozzle tip end, leading to dripping that may impact dose accuracy and process consistency. Axisymmetric drop shape analysis was used to evaluate the propensity of monoclonal antibody solution droplets for elongation in the presence of a nonionic surfactant (polysorbate 20, polysorbate 80, poloxamer 188, Brij®35, Brij®58 or FM1000). Droplets were created using a syringe and dosing needle, or a pump and filling nozzle. Droplet elongation rate was calculated from the linear evolution of interfacial surface area over time. An increase in elongation rate led to a quicker occurrence of droplet pinch-off, meaning a higher propensity for dripping. Elongation rate increased with both droplet volume and surfactant concentration. The evolution of elongation rate with droplet volume provided some insights into interface stretching capacity. We propose droplet elongation rate as an indicator of monoclonal antibody solution propensity for dripping.

A Review on the Stability Challenges of Advanced Biologic Therapeutics

Advanced biotherapeutic systems such as gene therapy, mRNA lipid nanoparticles, antibody-drug conjugates, fusion proteins, and cell therapy have proven to be promising platforms for delivering targeted biologic therapeutics. Preserving the intrinsic stability of these advanced therapeutics is essential to maintain their innate structure, functionality, and shelf life. Nevertheless, various challenges and obstacles arise during formulation development and throughout the storage period due to their complex nature and sensitivity to various stress factors. Key stability concerns include physical degradation and chemical instability due to various factors such as fluctuations in pH and temperature, which results in conformational and colloidal instabilities of the biologics, adversely affecting their quality and therapeutic efficacy. This review emphasizes key stability issues associated with these advanced biotherapeutic systems and approaches to identify and overcome them. In gene therapy, the brittleness of viral vectors and gene encapsulation limits their stability, requiring the use of stabilizers, excipients, and lyophilization. Keeping cells viable throughout the whole cell therapy process, from culture to final formulation, is still a major difficulty. In mRNA therapeutics, stabilization strategies such as the optimization of mRNA nucleotides and lipid compositions are used to address the instability of both the mRNA and lipid nanoparticles. Monoclonal antibodies are colloidally and conformationally unstable. Hence, buffers and stabilizers are useful to maintain stability. Although fusion proteins and monoclonal antibodies share structural similarities, they show a similar pattern of instability. Antibody-drug conjugates possess issues with conjugation and linker stability. This review outlines the stability issues associated with advanced biotherapeutics and provides insights into the approaches to address these challenges.

Impact of Weak Vibration Generated by a Refrigerator on Protein Aggregation

Protein aggregates and particles in biopharmaceuticals can induce adverse immune responses in patients. Thus, suppression of the formation of protein aggregates and particles is important for the successful development of therapeutic proteins. Mechanical stresses, including agitation, are widely recognized as stress factors that generate protein aggregates and particles. However, although refrigerators and storage chambers generate weak vibration, there have been no studies of the impact of such weak vibration on aggregate and particle formation during storage. In this study, monomer loss and aggregate formation of a CTLA4-Ig were evaluated during storage in a refrigerator (having a vibration acceleration less than 0.006 G) with or without three vibration isolators. The vibration isolators reduced the vibration acceleration, thereby decreasing the rate of monomer loss and nanometer-sized aggregate formation. The increase in the aggregation rate due to the weak vibration was not mitigated by adding poloxamer 188 or eliminating the air-liquid interface, which are processes known to be effective in preventing protein aggregation due to mechanical stresses. Thus, reducing vibration should be an effective way to mitigate the risk of aggregate formation.

Mitigation Strategies against Antibody Aggregation Induced by Oleic Acid in Liquid Formulations

Polysorbates 20 and 80 (PS20 and PS80) are commonly used in the formulations of biologics to protect against interfacial stresses. However, these surfactants can degrade over time, releasing free fatty acids, which assemble into solid particles or liquid droplets. Here, we apply a droplet microfluidic platform to analyze the interactions between antibodies and oleic acid, the primary free fatty acid resulting from the hydrolysis of PS80. We show that antibodies adsorb within seconds to the polar oleic acid-water interface, forming a viscoelastic protein layer that leads to particle formation upon mechanical rupture. By testing two different monoclonal antibodies of pharmaceutical origin, we show that the propensity to form a rigid viscoelastic layer is protein-specific. We further demonstrate that intact PS80 is effective in preventing antibody adsorption at the oleic acid-water interface only at low antibody concentrations and low pH, where oleic acid is fully protonated. Importantly, introduction of the amino acid l-arginine prevents the formation of the interfacial layer and protein particles even at high antibody concentrations (180 mg mL-1). Overall, our findings indicate that oleic acid droplets in antibody formulations can lead to the formation of protein particles via an interface-mediated mechanism. Depending on the conditions, intact PS80 alone might not be sufficient to protect against antibody aggregation. Additional mitigation strategies include the optimization of protein physicochemical properties, pH, and the addition of arginine.

Real-Time Observation of Protein Aggregation at Liquid-Liquid Interfaces in a Microfluidic Device

A droplet microfluidic device to capture in real-time protein aggregation at liquid-liquid interfaces is described. In contrast to conventional methods, typically characterized by a lag time between the application of interfacial stress and the measurement of protein aggregation, here protein adsorption, the formation of a viscoelastic protein layer, aggregation, and shedding of protein particles into solution is simultaneously monitored. The device is applied to analyze the stability of antibody formulations over a wide range of concentrations (1-180 mg mL-1) at the silicone oil (SO)-water interface under controlled mechanical deformation. The adsorption onto oil droplets induces the formation of a viscoelastic protein layer on a subsecond timescale, which progressively restricts the relaxation of the droplets within the chip. Upon mechanical rupture, the protein layer releases particles in solution. The rate of particle formation increases strongly with concentration, similar to the bulk viscosity. Concentrations above 120 mg mL-1 lead to aggregation in seconds and drastically decrease the mechanical perturbations required to shed protein particles in solution. These results are important for the development of formulations at high-protein concentrations (>100 mg mL-1) and indicate that particular attention should be given to interface-induced particle formation in this concentration range. In this context, low-volume microfluidic platforms allow the assessment of protein physical instabilities early in development and represent attractive tools to optimize antibody stability and formulation design consuming limited amounts of material.

Evaluating surfactant effectiveness in preventing antibody adsorption directly on medical surfaces using a novel device

Biopharmaceuticals, specifically antibody-based therapeutics, have revolutionized disease treatment. Throughout their lifecycle, these therapeutic proteins are exposed to several stress conditions, for example at interfaces, posing a risk to the drug product stability, safety and quality. Therapeutic protein adsorption at interfaces may lead to loss of active product and protein aggregation, with potential immunogenicity risks. Non-ionic surfactants are commonly added in formulations to mitigate protein-surface interactions. However, their effectiveness varies with the monoclonal antibody (mAb), and model surface material. Extrapolating findings from model surfaces to real medical surfaces is challenging due to diverse properties. This study pioneers the evaluation of surfactant effectiveness in preventing mAb adsorption directly on medical surfaces at the medical bag/formulation interface, utilizing the ELIBAG device. The adsorption of different protein modalities, mAbs and antibody-drug conjugate (ADC), using three surfactants (PS80, PS20, and P188), was examined across various medical surfaces, IV bags and manufacturing bags, and model surfaces. Our findings reveal that surfactants prevent mAb adsorption depending on the mAb modality, surfactant type and concentration, and surface material. This research underscores the importance of considering real medical surfaces in direct contact with formulations, offering insights for enhancing drug product development and ensuring material-protein compatibility in real world use.

Small scale model for predicting transportation-induced particle formation in biotherapeutics

Understanding protein adsorption and aggregation at the air-liquid interfaces of protein solutions is an important open challenge in biopharmaceutical, medical, and biotechnological applications, among others. Proteins, being amphiphilic, adsorb at the surface, partially unfold, and form a viscoelastic film through non-covalent interactions. Mechanical agitation of the surface can break this film up, releasing insoluble protein particles into the solution. These aggregates are usually highly undesirable and even toxic in cases, such as for biopharmaceutical application. Therefore, it is imperative to be able to predict the behavior of such solutions undergoing surface agitation during handling, usually transport or mixing. We apply the findings on the viscoelastic protein film, formed at the air-liquid interface, to the prediction of surface mediated aggregation in selected protein solutions of direct biopharmaceutical relevance. Our broad study of Brewster angle microscopy and aggregation monitoring across multiple size ranges by micro-flow imaging, light scattering, and size exclusion chromatography shows that formation of protein particles is driven by the adsorption rate as compared to the rate of surface turnover and that surface film dynamics in the quiescent phase directly affect aggregation. We demonstrate how these learnings can be directly applied to the design of a novel small scale biopharmaceutical stability study, simulating relevant transport conditions. More generally, we show the impact of adsorption dynamics at the air-liquid interface on the stability of a distinct protein solution, as a general contribution to understanding different colloidal and biological interfacial systems.

Effect of surfactants on lactate dehydrogenase aqueous solutions: A comparative study of poloxamer 188, polysorbate 20 and 80

The effect of three commonly used surfactants, poloxamer 188 (P188), polysorbate 20 and 80 (PS20 and PS80), on the stability of a model protein, lactate dehydrogenase (LDH), was compared in aqueous solutions. In the absence of a surfactant, protein solution revealed a gradual decrease in surface tension as a function of time. The addition of surfactant resulted in a rapid decrease in the surface tension. This suggested that the surface behavior was dictated by the surfactant. PS20 and PS80 were more effective than P188 in preventing LDH adsorption on the solution surface. The advantage of polysorbates over P188 was also evident from the higher LDH tetramer recovery after shaking (room temperature, 30 h), especially when the surfactants were used at concentrations ≤ 0.01% w/v. However, PS20 and PS80 accelerated protein unfolding during quiescent storage at 40 °C. Based on circular dichroism results, polysorbates perturbed the tertiary structure of LDH but not the secondary structure, while P188 did not impact the protein structure and stability. Polysorbates were more effective in stabilizing LDH against mechanical stress (shaking), but their adverse effects on protein conformational stability need to be carefully evaluated.

Microfluidic Stress Device to Decouple the Synergistic Effect of Shear and Interfaces on Antibody Aggregation

Protein denaturation and aggregation resulting from the effects of interfacial stress, often enhanced by flow and shear stress, pose significant challenges in the production of therapeutic proteins and monoclonal antibodies. The influence of flow on protein stability is closely intertwined with interfacial effects. In this study, we have developed a microfluidic device capable of exposing low volume (< 320 µL) protein solutions to highly uniform shear. To disentangle the synergistic impact of flow and interfaces on protein aggregation, we fabricated two devices composed of different materials, namely poly(methyl methacrylate) (PMMA) and stainless steel. Upon application of shear, we observed formation of protein particles in the micron-size range. Notably, The number of particles generated in the steel devices was ∼ 3.5 fold lower than in the PMMA device, hinting at an interface-mediated effect. With increasing the protein concentration from 1 to 50 mg/mL we observed a saturation in the amount of aggregates, further confirming the key role of solid-liquid interfaces in inducing particle formation. Introduction of non-ionic surfactants prevented protein aggregation, even at the highest tested protein concentration and low surfactant concentrations of 0.05 mg/mL. Overall, our findings corroborate the synergistic impact of shear and interface effects on protein aggregation. The device developed in this study offers a small-scale platform for assessing the stability of antibody formulations throughout various stages of the development and manufacturing process.

Combined Effect of Shaking Orbit and Vial Orientation on the Agitation-Induced Aggregation of Proteins

Orbital shaking in a glass vial is a commonly used forced degradation test to evaluate protein propensity for agitation-induced aggregation. Vial shaking in horizontal orientation has been widely recommended to maximize the air-liquid interface area while ensuring solution contact with the stopper. We evaluated the impact of shaking orbit diameter and frequency, and glass vial orientation (horizontal versus vertical) on the aggregation of three proteins prepared in surfactant-free formulation buffers. As soon as an orbit-specific frequency threshold was reached, an increase in turbidity was observed for the three proteins in vertical orientation only when using a 3 mm agitation orbit, and in horizontal orientation only when using a 30 mm agitation orbit. Orthogonal analyses confirmed turbidity was linked to protein aggregation. The most turbid samples had a visually more homogeneous appearance in vertical than in horizontal orientation, in line with the predicted dispersion of air and liquid phases obtained from computational fluid dynamics agitation simulations. Both shaking orbits were used to assess the performance of nonionic surfactants. We show that the propensity of a protein to aggregate in a vial agitated in horizontal or vertical orientation depends on the shaking orbit, and confirm that Brij® 58 and FM1000 prevent proteins from agitation-induced aggregation at lower concentrations than polysorbate 80.