Improving Prediction of Free Fatty Acid Particle Formation in Biopharmaceutical Drug Products: Incorporating Ester Distribution during Polysorbate 20 Degradation

A comparison of Polysorbates and Alternative Surfactants for Interfacial Stress Protection and Mitigation of Fatty Acid Particle Formation in the Presence of an Esterase

The hydrolysis of polysorbate surfactants in large molecule drug product formulations caused by residual host cell proteins presents numerous stability concerns for pharmaceuticals. The fatty acids (FA) released by polysorbate hydrolysis can nucleate into particulates or challenge the conformational stability of the proteinaceous active pharmaceutical ingredient (API). The loss of intact polysorbate may also leave the Drug Product (DP) vulnerable to interfacial stresses. Polysorbate 20 and 80 are available in several different quality grades (Multi-compendial, Super Refined, Pure Lauric Acid (PLA)/Pure Oleic Acid (POA)). All variations of polysorbate as well as three alternative surfactants: Brij L23, Brij O20 and Poloxamer 188 were compared for their ability to protect against air-water interfacial stresses as well as their risk for developing particulates when in the presence of lipoprotein lipase (LPL) (Pseudomonas). Results show a meaningful difference in the timing and morphology of FA particle formation depending on the type of polysorbate used. All grades of polysorbate, while susceptible to hydrolysis, still offered sufficient protection to interfacial stresses, even when hydrolyzed to concentrations as low as 0.005 % (w/v). Alternative surfactants that lack an ester bond were resistant to lipase degradation and showed good protection against shaking stress.

Identification of Acyl-Protein Thioesterase-1 as a Polysorbate-Degrading Host Cell Protein in a Monoclonal Antibody Formulation Using Activity-Based Protein Profiling

Polysorbate (PS) degradation in monoclonal antibody (mAb) formulations poses a significant challenge in the biopharmaceutical industry. PS maintains protein stability during drug product's shelf life but is vulnerable to breakdown by low-abundance residual host cell proteins (HCPs), particularly hydrolytic enzymes such as lipases and esterases. In this study, we used activity-based protein profiling (ABPP) coupled with mass spectrometry to identify acyl-protein thioesterase-1 (APT-1) as a polysorbate-degrading HCP in one case of mAb formulation with stability problems. We validated the role of APT1 by matching the polysorbate degradation fingerprint in the mAb formulation with that of a recombinant APT1 protein. Furthermore, we found an agreement between APT1 levels and PS degradation rates in the mAb formulation, and we successfully halted PS degradation using APT1-specific inhibitors ML348 and ML211. APT1 was found to co-purify with a specific mAb via hitchhiking mechanism. Our work provides a streamlined approach to identifying critical HCPs in PS degradation, supporting quality-by-design principles in pharmaceutical development.

Discrimination of polysorbate 20 by high-performance liquid chromatography-charged aerosol detection and characterization for components by expanding compound database and library

Analyzing polysorbate 20 (PS20) composition and the impact of each component on stability and safety is crucial due to formulation variations and individual tolerance. The similar structures and polarities of PS20 components make accurate separation, identification, and quantification challenging. In this work, a high-resolution quantitative method was developed using single-dimensional high-performance liquid chromatography (HPLC) with charged aerosol detection (CAD) to separate 18 key components with multiple esters. The separated components were characterized by ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) with an identical gradient as the HPLC-CAD analysis. The polysorbate compound database and library were expanded over 7-time compared to the commercial database. The method investigated differences in PS20 samples from various origins and grades for different dosage forms to evaluate the composition-process relationship. UHPLC-Q-TOF-MS identified 1329 to 1511 compounds in 4 batches of PS20 from different sources. The method observed the impact of 4 degradation conditions on peak components, identifying stable components and their tendencies to change. HPLC-CAD and UHPLC-Q-TOF-MS results provided insights into fingerprint differences, distinguishing quasi products.

Effect of Host Cell Protein on Chinese Hamster Ovary Recombinant Protein Production and its Removal Strategies: A Mini Review

Chinese hamster ovary cells are the main expression system for recombinant therapeutic proteins. During the production of these proteins, certain host cell proteins are secreted, broken down, and released by host cells in the culture along with the proteins of interest. These host cell proteins are often difficult to remove during the downstream purification process, and thus affect the quality, safety, and effectiveness of recombinant protein biopharmaceutical products and increase the production cost of recombinant therapeutic proteins. Therefore, host cell protein production must be reduced as much as possible during the production process and eliminated during purification. This article reviews the harm caused by host cell proteins in the production of recombinant protein drugs using Chinese hamster ovary cell, factors affecting host cell proteins, the monitoring and identification of these proteins, and methods to reduce their type and quantity in the final product.

Enzymatic degradation pattern of polysorbate 20 impacts interfacial properties of monoclonal antibody formulations

Polysorbate 20 (PS20) is widely used to maintain protein stability in biopharmaceutical formulations. However, PS20 is susceptible to hydrolytic degradation catalyzed by trace amounts of residual host cell proteins present in monoclonal antibody (mAb) formulations. The resulting loss of intact surfactant and the presence of PS20 degradation products, such as free fatty acids (FFAs), may impair protein stability. In this study, two hydrolytically-active immobilized lipases, which primarily targeted either monoester or higher-order ester species in PS20, were used to generate partially-degraded PS20. The impact of PS20 degradation pattern on critical micelle concentration (CMC), surface tension, interfacial rheology parameters and agitation protection was assessed. CMC was slightly increased upon monoester degradation, but significantly increased upon higher-order ester degradation. The PS20 degradation pattern also significantly impacted the dynamic surface tension of a mAb formulation, whereas changes in the equilibrium surface tension were mainly caused by the adsorption of FFAs onto the air-water interface. In an agitation protection study, monoester degradation resulted in the formation of soluble mAb aggregates and proteinaceous particles, suggesting that preferential degradation of PS20 monoester species can significantly impair mAb stability. Additional mAbs should be tested in the future to assess the impact of the protein format.

Oxidation of polysorbates - An underestimated degradation pathway?

To ensure the stability of biologicals over their entire shelf-life, non-ionic surface-active compounds (surfactants) are added to protect biologics from denaturation and particle formation. In this context, polysorbate 20 and 80 are the most used detergents. Despite their benefits of low toxicity and high biocompatibility, specific factors are influencing the intrinsic stability of polysorbates, leading to degradation, loss in efficacy, or even particle formation. Polysorbate degradation can be categorized into chemical or enzymatic hydrolysis and oxidation. Under pharmaceutical relevant conditions, hydrolysis is commonly originated from host cell proteins, whereas oxidative degradation may be caused by multiple factors such as light, presence of residual metal traces, peroxides, or temperature, which can be introduced upon manufacturing or could be already present in the raw materials. In this review, we provide an overview of the current knowledge on polysorbates with a focus on oxidative degradation. Subsequently, degradation products and key characteristics of oxidative-mediated polysorbate degradation in respect of different types and grades are summarized, followed by an extensive comparison between polysorbate 20 and 80. A better understanding of the radical-induced oxidative PS degradation pathway could support specific mitigation strategies. Finally, buffer conditions, various stressors, as well as appropriate mitigation strategies, reagents, and alternative stabilizers are discussed. Prior manufacturing, careful consideration and a meticulous risk-benefit analysis are highly recommended in terms of polysorbate qualities, buffers, storage conditions, as well as mitigation strategies.

Image Classification of Degraded Polysorbate, Protein and Silicone Oil Sub-Visible Particles Detected by Flow-Imaging Microscopy in Biopharmaceuticals Using a Convolutional Neural Network Model

Degradation of polysorbates in biopharmaceutical formulations can induce the formation of sub-visible particles (SvPs) in the form of free-fatty acids (FFAs) and potentially protein aggregates. Flow-imaging microscopy (FIM) is one of the most common techniques for enumerating and characterizing the SvPs, allowing for collection of image data of the SvPs in the size ranges of two to several hundred micrometers. The vast amounts of data obtained with FIM do not allow for rapid manual characterization by an experienced analyst and can be ambiguous. In this work, we present the application of a custom convolutional neural network (CNN) for classification of SvP images of FFAs, proteinaceous particles and silicon oil droplets, by FIM. The network was then used to predict the composition of artificially pooled test samples of unknown and labeled data with varying compositions. Minor misclassifications were observed between the FFAs and proteinaceous particles, considered tolerable for application to pharmaceutical development. The network is considered to be suitable for fast and robust classification of the most common SvPs found during FIM analysis.

Degradation of polysorbate investigated by a high-performance liquid chromatography multi-detector system with charged aerosol and mass detection

Polysorbate 80 is widely used as a formulation component in biopharmaceutical drug products. Recent studies have shown that polysorbate 80 is readily degraded either through direct or indirect means. The degradation of polysorbate 80 causes a concern for the long-term stability of biopharmaceutical drug product, as the breakdown products of polysorbate 80 have been shown to cause adverse effects, such as formation of sub-visible and visible particles and mAb aggregation. Understanding the path and extent of degradation is of a paramount importance for the formulator during formulation development. A multi-detector HPLC system using charged aerosol and mass detection was developed and optimized for the characterization of polysorbate 80 standards. The system included a post-column make-up flow, i.e. an inverse gradient, that enabled constant eluent composition at the detectors. The inverse gradient eliminated the main source of variability for the charged aerosol detector response, thereby enabling the calculation of the mass balance between polysorbate components with different degrees of esterification. Extracted ion chromatograms of the mass detector combined with their respective retention times were used to qualitatively characterize the polysorbate samples down to the individual components. The system was applied to study the degradation of several polysorbate standards which occurred by enzymatic digestion or long-term storage. The system provided detailed information on the mechanism of degradation without the need for additional orthogonal analytical techniques.

Development of UPLC-UV-ELSD Method for Fatty Acid Profiling in Polysorbate 80 and Confirmation of the Presence of Conjugated Fatty Acids by Mass Spectrometry, UV Absorbance and Proton Nuclear Magnetic Resonance Spectroscopy

Polysorbate 80 (PS80), a chemical substance composed of sorbitol, ethylene glycol, and fatty acids, is commonly used in pharmaceutical drug products to stabilize formulations. However, recent studies have demonstrated that PS80 may hydrolyze over time and the released free fatty acids (FFAs) may lead to particle formation. Naming conventions of fatty acids in current pharmacopeia and in products' certificates of analysis (CoA) of PS80 do not typically distinguish between isomeric species of fatty acids in PS80. Thus, methods to fully characterize the fatty acid species present in PS80 raw materials are needed to enhance quality control strategies of pharmaceuticals using PS80. Here, extended effort is taken to characterize fatty acids in hydrolyzed PS80 raw materials and elucidate the identities of isomeric fatty acid species. In this work, a method was developed and optimized for separation and detection of fatty acids in alkaline hydrolyzed PS80 raw materials using ultra performance liquid chromatography (UPLC) with ultra-violet (UV) detection and evaporative light scattering detection (ELSD). Fatty acids not specified in the current pharmacopeias were detected in PS80 raw material by the developed LC-UV-ELSD method including conjugated forms of linoleic and linolenic fatty acid species. Their identities were orthogonally confirmed by retention time agreement with analytical standards, accurate mass by high resolution mass spectrometry, UV absorbance, and proton nuclear magnetic resonance spectroscopy. The detected conjugated fatty acids are theoretically more hydrophobic and less soluble than their unconjugated counterparts and may increase the propensity of PS80 to form particles upon hydrolysis. This work highlights the need for better quality control of PS80 raw material, as it may eventually play a critical role in product quality of therapeutic proteins.

Small-angle x-ray scattering investigation of the integration of free fatty acids in polysorbate 20 micelles

A critical quality attribute for liquid formulations is the absence of visible particles. Such particles may form upon polysorbate hydrolysis resulting in release of free fatty acids into solution followed by precipitation. Strategies to avoid this effect are of major interest for the pharmaceutical industry. In this context, we investigated the structural organization of polysorbate micelles alone and upon addition of the fatty acid myristic acid (MA) by small-angle x-ray scattering. Two complementary approaches using a model of polydisperse core-shell ellipsoidal micelles and an ensemble of quasiatomistic micelle structures gave consistent results well describing the experimental data. The small-angle x-ray scattering data reveal polydisperse mixtures of ellipsoidal micelles containing about 22-35 molecules per micelle. The addition of MA at concentrations up to 100 μg/mL reveals only marginal effects on the scattering data. At the same time, addition of high amounts of MA (>500 μg/mL) increases the average sizes of the micelles indicating that MA penetrates into the surfactant micelles. These results together with molecular modeling shed light on the polysorbate contribution to fatty acid solubilization preventing or delaying fatty acid particle formation.

Investigation of excipients impact on polysorbate 80 degradation in biopharmaceutical formulation buffers

A study on the polysorbate 80 stability in various formulation buffers commonly used in biopharmaceuticals was performed, to investigate the excipients influence on polysorbate 80 degradation. Polysorbate 80 is a common excipient in biopharmaceutical products. However, its degradation will potentially impact the drug product quality, and may trigger protein aggregation and particles formation. Due to the heterogeneity of the polysorbates and the mutual effects with other formulation compositions, the study of polysorbate degradation is challenging. Herein, a real-time stability study was designed and performed. The polysorbate 80 degradation trend was monitored by fluorescence micelle-based assay (FMA), reversed-phase-ultra-performance liquid chromatography-evaporative light scattering detector (RP-UPLC-ELSD) assay, and LC-MS assay. These assays provide orthogonal results to reveal both the micelle-forming capability and the compositional changes of polysorbate 80 in different buffer systems. The degradation occurred after a period of storage under 25 °C in different trend, which indicates the excipients could impact the degradation kinetics. Upon comparison, the degradation is prone to happen in histidine buffer than in acetate, phosphate or citrate buffers. LC-MS confirms oxidation as an independent degradation pathway with detection of the oxidative aldehyde. Thus, it is necessary to pay more attention to the excipients selection and their potential impact on polysorbate 80 stability to achieve longer shelf life for the biopharmaceuticals. Besides, the protective roles of several additives were figured out, which could be applied as potential industrial solutions to the polysorbate 80 degradation issues.

Micelle Formation and Phase Separation of Poloxamer 188 and Preservative Molecules in Aqueous Solutions Studied by Small Angle X-ray Scattering

Multi-injection pharmaceutical products such as insulin must be formulated to prevent aggregation and microbial contamination. Small-molecule preservatives and nonionic surfactants such as poloxamer 188 (P188) are thus often employed in protein drug formulations. However, mixtures of preservatives and surfactants can induce aggregation and even phase separation over time, despite the fact that all components are well dissolvable when used alone in aqueous solution. A systematic study is conducted here to understand the phase behavior and morphological causes of aggregation of P188 in the presence of the preservatives phenol and benzyl alcohol, primarily using small-angle x-ray scattering (SAXS). Based on SAXS results, P188 remains as unimers in solution when below a certain phenol concentration. Upon increasing the phenol concentration, a regime of micelle formation is observed due to the interaction between P188 and phenol. Further increasing the phenol concentration causes mixtures to become turbid and phase-separate over time. The effect of benzyl alcohol on the phase behavior is also investigated.

An Intra-Company Analysis of Inherent Particles in Biologicals Shapes the Protein Particle Mitigation Strategy Across Development Stages

To better understand protein aggregation and inherent particle formation in the biologics pipeline at Novartis, a cross-functional team collected and analyzed historical protein particle issues. Inherent particle occurrences from the past 10 years were systematically captured in a protein particle database. Where the root cause was identified, a number of product attributes (such as development stage, process step, or protein format) were trended. Several key themes were revealed: 1) there was a higher propensity for inherent particle formation with non-mAbs than with mAbs; 2) the majority of particles were detected following manufacturing at scale, and were not predicted by the small-scale studies; 3) most issues were related to visible particles, followed by subvisible particles; 4) 50% of the issues were manufacturing related. These learnings became the foundation of a particle mitigation strategy across development and technical transfer, and resulted in a set of preventive actions. Overall, this study provides further insight into a recognized industry challenge and hopes to inspire the biopharmaceutical industry to transparently share their experiences with inherent particles formation.

Characterization of Recombinantly-Expressed Hydrolytic Enzymes from Chinese Hamster Ovary Cells: Identification of Host Cell Proteins that Degrade Polysorbate

Enzymatic hydrolysis of polysorbate in drug products is a major challenge for the biopharmaceutical industry. Polysorbate hydrolysis caused by host cell proteins (HCPs) co-purified during bioprocessing can reduce the protective effects of the surfactant for the active pharmaceutical ingredient and cause the accumulation of low-solubility degradation products over the long-term storage. The identities of such HCPs are elusive due to their extremely low concentrations after the efficient purification processes of most biopharmaceuticals. In this work, 20 enzymes-selected for their known or putative hydrolytic activity and potential to degrade polysorbate-were recombinantly expressed, purified, and characterized via orthogonal methods. First, these recombinant HCPs were assessed for hydrolytic activity against a fluorogenic esterase substrate in a recently-developed, high-throughput assay. Second, these HCPs were screened for hydrolytic activity against polysorbate in a representative mAb formulation. Third, HCPs that displayed hydrolytic activities in the first two assays were subjected to more detailed characterization of their enzyme kinetics against polysorbates. Finally, these HCPs were evaluated for substrate specificity towards different sub-species of polysorbates. This work provides critical new insights for targeted LC-MS/MS approaches for identification of relevant polysorbate-degrading enzymes and supports improvements to remove such HCPs, including knockouts or targeted removal during purification.

High Throughput FAMS - A Fatty Acid Mass Spectrometry Method for Monitoring Polysorbate Hydrolysis in QC

Surfactant degradation in biopharmaceuticals has recently gained significant attention in the pharmaceutical industry. Specifically, hydrolytic degradation of polysorbates, leading to the release of free fatty acids potentially forming visible particles, is a key theme in technical development. To address this emerging topic, we present the development of a fully automated liquid-chromatography single quad mass detector method for the quantification of free fatty acids in biopharmaceuticals. For the first time, we have quantified the longer chain fatty acid degradation products of polysorbate, palmitic and stearic acid, allowing reliable detection and early critical insights for process improvements. This high-throughput method was validated underlining its robust performance in an interlaboratory trial as well as high flexibility allowing different robotic platforms and preparation techniques. The combination of automated sample preparation, separation by liquid chromatography and single quad mass detection makes the validated fatty acid mass spectrometry assay ready for routine use in a regulated environment.

End-to-End Approach to Surfactant Selection, Risk Mitigation, and Control Strategies for Protein-Based Therapeutics

A survey performed by the AAPS Drug Product Handling community revealed a general, mostly consensus, approach to the strategy for the selection of surfactant type and level for biopharmaceutical products. Discussing and building on the survey results, this article describes the common approach for surfactant selection and control strategy for protein-based therapeutics and focuses on key studies, common issues, mitigations, and rationale. Where relevant, each section is prefaced by survey responses from the 22 anonymized respondents. The article format consists of an overview of surfactant stabilization, followed by a strategy for the selection of surfactant level, and then discussions regarding risk identification, mitigation, and control strategy. Since surfactants that are commonly used in biologic formulations are known to undergo various forms of degradation, an effective control strategy for the chosen surfactant focuses on understanding and controlling the design space of the surfactant material attributes to ensure that the desired material quality is used consistently in DS/DP manufacturing. The material attributes of a surfactant added in the final DP formulation can influence DP performance (e.g., protein stability). Mitigation strategies are described that encompass risks from host cell proteins (HCP), DS/DP manufacturing processes, long-term storage, as well as during in-use conditions.

Formulation mitigations for particle formation induced by enzymatic hydrolysis of polysorbate 20 in protein-based drug products: insights from a full-factorial longitudinal study

Hydrolytic degradation of the polysorbate 20 (PS20) surfactant in protein-based liquid formulations releases free fatty acids (FFAs), which can accumulate to form particles in drug products during real-time (long-term) storage. To identify formulation conditions that mitigate the risk of particle formation, we conducted a longitudinal study using purified recombinant monoclonal antibody (mAb) formulated in 24 conditions. In this real-time stability study at 5 °C, three key formulation parameters—mAb concentration, initial PS20 concentration, and pH—were varied across representative ranges in a full-factorial design. A longitudinal regression analysis was used to evaluate the effects of these parameters and their interactions on PS20 degradation (via measurements of PS20, FFAs, and PS20 ester distribution) and on particle formation (via visible particle observations and subvisible particle counts). The time-dependent onset of visible particles trended with the rise in subvisible particle counts and FFA levels and fall in PS20 concentration. In the ranges studied here, lower mAb concentration and higher initial PS20 concentration delayed the onset of particles, whereas pH had a negligible effect. These observations were consistent with the general trends predicted by our previously published FFA solubility model. Taken together, these findings highlight the complex relationships between formulation parameters, PS20 degradation, and particle formation.

Industry Perspective on the Use and Characterization of Polysorbates for Biopharmaceutical Products Part 2: Survey Report on Control Strategy Preparing for the Future

Polysorbate (PS) 20 and 80 are the main surfactants used to stabilize biopharmaceutical products. Industry practices on various aspects of PS based on a confidential survey and following discussions by 16 globally acting major biotechnology companies is presented in two publications. Part 1 summarizes the current practice and use of PS during manufacture in addition to aspects like current understanding of the (in)stability of PS, the routine QC testing and control of PS, and selected regulatory aspects of PS.¹ The current part 2 of the survey focusses on understanding, monitoring, prediction, and mitigation of PS degradation pathways in order to propose an effective control strategy. The results of the survey and extensive cross-company discussions are put into relation with currently available scientific literature.

Differential Surface Adsorption Phenomena for Conventional and Novel Surfactants Correlates with Changes in Interfacial mAb Stabilization

Protein adsorption on surfaces can result in loss of drug product stability and efficacy during the production, storage, and administration of protein-based therapeutics. Surface-active agents (excipients) are typically added in protein formulations to prevent undesired interactions of proteins on surfaces and protein particle formation/aggregation in solution. The objective of this work is to understand the molecular-level competitive adsorption mechanism between the monoclonal antibody (mAb) and a commercially used excipient, polysorbate 80 (PS80), and a novel excipient, N-myristoyl phenylalanine-N-polyetheramine diamide (FM1000). The relative rate of adsorption of PS80 and FM1000 was studied by pendant bubble tensiometry. We find that FM1000 saturates the interface faster than PS80. Additionally, the surface-adsorbed amounts from X-ray reflectivity (XRR) measurements show that FM1000 blocks a larger percentage of interfacial area than PS80, indicating that a lower bulk FM1000 surface concentration is sufficient to prevent protein adsorption onto the air/water interface. XRR models reveal that with an increase in mAb concentration (0.5-2.5 mg/mL: IV based formulations), an increased amount of PS80 concentration (below critical micelle concentration, CMC) is required, whereas a fixed value of FM1000 concentration (above its relatively lower CMC) is sufficient to inhibit mAb adsorption, preventing mAb from co-existing with surfactants on the surface layer. With this observation, we show that the CMC of the surfactant is not the critical factor to indicate its ability to inhibit protein adsorption, especially for chemically different surfactants, PS80 and FM1000. Additionally, interface-induced aggregation studies indicate that at minimum surfactant concentration levels in protein formulations, fewer protein particles form in the presence of FM1000. Our results provide a mechanistic link between the adsorption of mAbs at the air/water interface and the aggregation induced by agitation in the presence of surfactants.

The Characterization of Polysorbate

Polysorbates (PSs), including PS20 and PS80, are non-ionic surfactants widely used in the pharmaceutical industry to enhance drug solubility and stability. Despite their wide application, PSs are prone to degradation by either hydrolysis or oxidation in drug formulations during storage; therefore, a PS characterization method assessing protein products is needed for stability testing and for understanding the degradation pathway. In this article, we detail our protocol for sample preparation for forced degradation study and our instrumentation setup for PS profiling and quantitation in protein samples. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Sample preparation for forced degradation of polysorbate in protein samples Basic Protocol 2: Two-dimensional liquid chromatography coupled with charged aerosol detector or mass spectrometry to analyze polysorbate degradation.

A Mechanistic Understanding of Monoclonal Antibody Interfacial Protection by Hydrolytically Degraded Polysorbate 20 and 80 under IV Bag Conditions

PURPOSE

Polysorbates (PS) contain polyoxyethylene (POE) sorbitan/isosorbide fatty acid esters that can partially hydrolyze over time in liquid drug products to generate degradants and a remaining intact PS fraction with a modified ester distribution. The degradants are composed of free fatty acids (FFAs) --primarily lauric acid for PS20 and oleic acid for PS80-- and POE head groups. We previously demonstrated that under IV bag agitation conditions, mAb1 (a surface-active IgG4) aggregation increased with increasing amounts of degradants for PS20 but not for PS80. The purpose of this work is to understand the mechanism behind this observation.

METHODS

The surface tension of the remaining intact PS fraction without degradants was modeled and compared with that of enzymatically degraded PS solutions. Next, mAb1 aggregation in saline was measured in the presence of laurate and oleate salts during static storage. Lastly, colloidal and conformational stability of mAb1 in the presence of these salts was investigated through differential scanning fluorimetry and dynamic light scattering under IV bag solution conditions.

RESULTS

The surface tension was primarily influenced by FFAs rather than the modified ester distribution of the remaining intact PS. MAb1 bulk aggregation increased in the presence of laurate but not oleate salts. Both salt types increased the melting temperature of mAb1 indicating FFA-mAb1 interactions. However, only laurate salt increased mAb1 self-association potentially explaining the higher aggregation propensity in its presence.

CONCLUSION

Our results help explain the observed differences between hydrolytically degraded PS20 and PS80 in affecting mAb1 aggregation under IV bag agitation conditions.

The measurement and control of high-risk host cell proteins for polysorbate degradation in biologics formulation

Nonionic surfactant polysorbates, including PS-80 and PS-20, are commonly used in the formulation of biotherapeutic products for both preventing surface adsorption and acting as stabilizer against protein aggregation. Trace levels of residual host cell proteins (HCPs) with lipase or esterase enzymatic activity have been shown to degrade polysorbates in biologics formulation. The measurement and control of these low abundance, high-risk HCPs for polysorbate degradation are an industry-wide challenge to achieve desired shelf life of biopharmaceuticals in liquid formulation, especially for high-concentration formulation product development. Here, we reviewed the challenges, recent advances, and future opportunities of analytical method development, risk assessment, and control strategies for polysorbate degradation during formulation development with a focus on enzymatic degradation. Continued efforts to advance our understanding of polysorbate degradation in biologics formulation will help develop high-quality medicines for patients.

Fatty Acids Can Induce the Formation of Proteinaceous Particles in Monoclonal Antibody Formulations

The presence of subvisible or visible particles in mAb formulations can pose significant challenges to pharmaceutical development as it can lead to reduced shelf life, batch rejection, and recalls. Among all type of particles, proteinaceous particles are the most concerning due to their potential role in immunogenicity. Nevertheless, the underlying mechanism for protein particle formation remains poorly understood. Past research highlighted the importance of interfaces and mechanical agitation in causing protein particle formation. Current research suggests that fatty acids, as impurities present in excipients or as a result of polysorbate degradation, can also induce protein assembly and promote particle formation. In this work, we assessed oleic and lauric acid for their impact on particle formation as each represents the main hydrolysis product of PS80 or PS20, respectively. It was found that co-existence of either fatty acids with 10 mg/mL mAb A can cause protein particles, with a similar morphology to those observed previously in mAb formulations. FTIR spectra showed that the particles are proteinaceous, heterogeneous in its composition, but contain corresponding fatty acids. Interestingly, it was found that oleic acid is significantly more effective in causing protein particles than lauric acid in these experiments. This suggests that PS20 containing formulations might have a lower likelihood to have protein particles compared to PS80 containing mAb formulations if hydrolysis of polysorbate were to occur. Lastly, the presence of 0.01% polysorbate in the mAb A formulation was able to fully mitigate the effect of fatty acids and reduce the protein particles significantly, suggesting a potential mechanism where interfacial action is involved. The present study can help to understand the root cause for protein particles in a mAb formulation where fatty acids are introduced because of polysorbate hydrolysis. With further work, it will help to shed light into product control strategy as well as design approaches for robust mAb products.

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.

Degradation of Polysorbate 20 by Sialate O-Acetylesterase in Monoclonal Antibody Formulations

Polysorbates (PS) are surfactants commonly added in biologics formulations that can protect proteins from denaturation and aggregation. However, decreases in polysorbate 20 (PS20) content have been observed in some monoclonal antibody formulations, causing the formation of visible and/or subvisible particles that ultimately compromise the quality and stability of the therapeutic protein products. It was determined that the particles are mainly composed of free fatty acid, suggesting enzymatic hydrolysis of PS is responsible for the degradation of PS. Enrichment of host cell proteins (HCPs) by immunoprecipitation followed by shotgun proteomics have been utilized to identify the HCPs that can hydrolyze PS20. One HCP, sialate O-acetylesterase (SIAE), demonstrated strong enzymatic activity for PS20 degradation even at low concentration (<5 ppm level). Incubation of recombinant SIAE with PS20 resulted in a unique degradation pattern where the hydrolysis of monoester with short fatty acid chain (C12, C14) was observed but not the monoester with long fatty acid chain (C16, C18) or higher-order esters. SIAE was detected and quantitated in several formulated mAbs, and the amount of SIAE was positively correlated to PS20 degradation in these mAbs during incubation. Additional experiments also showed that when SIAE was depleted, PS20 degradation was diminished, suggesting a causality between SIAE and PS20 degradation. The lipase activity of SIAE is specific to PS20, but not to PS 80 (PS80), which contains monoesters with long chain fatty acid (C18) and higher-order esters. The specific esterase activity of SIAE on PS20 suggests a possible solution of using PS80 over PS20 to eliminate surfactant degradation in mAb products.

A Comprehensive Assessment of All-Oleate Polysorbate 80: Free Fatty Acid Particle Formation, Interfacial Protection and Oxidative Degradation

PURPOSE

Enzymatic polysorbate (PS) degradation and resulting free fatty acid (FFA) particles are detrimental to biopharmaceutical drug product (DP) stability. Different types and grades of polysorbate have varying propensity to form FFA particles. This work evaluates the homogenous all-oleate (AO) PS80 alongside heterogeneous PS20 and PS80 grades in terms its propensity to form FFA particles and other important attributes like interfacial protection and oxidation susceptibility.

METHODS

FFA particle formation rates were compared by degrading PS using non-immobilized hydrolases and fast degrading DP formulations. Interfacial protection of monoclonal antibodies (mAbs) was assessed by agitation studies in saline using non-degraded and degraded PS. Several antioxidants were assessed for their ability to mitigate AO PS80 oxidation and subsequent mAb oxidation by a 40°C placebo stability study and a 2, 2'-Azobis (2-amidinopropane) dihydrochloride stress model, respectively.

RESULTS

Visible and subvisible particles were significantly delayed in AO PS80 formulations compared with heterogeneous PS20 and PS80 formulations. Non-degraded AO PS80 was less protective of mAbs against the air-water interface compared with heterogeneous PS20. Interfacial protection by AO PS80 improved upon degradation owing to high surface activity of FFAs. Diethylenetriaminepentaacetic acid (DTPA) completely mitigated AO PS80 oxidation unlike L-methionine and N-Acetyl-DL-Tryptophan. However, DTPA did not mitigate radical mediated mAb oxidation.

CONCLUSION

AO PS80 is a promising alternative to reduce FFA particle formation compared with other PS types and grades. However, limitations observed here---such as lower protection against interfacial stresses and higher propensity for oxidation---need to be considered in assessing the risk/benefit ratio in using AO PS80.

Dissolution of Polysorbate 20 Degradation Related Free Fatty Acid Particles in Intravenous Bag Solutions

Degradation of Polysorbate 20 (PS20), a commonly used surfactant in drug product (DP) formulations, is a phenomenon of increasing concern to the biopharmaceutical industry. One of the most prevalent modes of PS20 degradation is enzymatic hydrolysis resulting from co-purified hydrolases that make their way into biologic DP formulations at trace levels. Enzymatic PS20 degradation results in generation of free fatty acids (FFAs) that have limited solubility in aqueous formulations and can form visible and/or sub-visible particles which is undesirable for parenteral DP stability and administration. Many therapeutic monoclonal antibodies are administered intravenously after first diluting the DP into an infusion solution (e.g., 0.9% normal saline, 0.45% half normal saline or 5% dextrose). The purpose of this work is to understand if FFA particles in the DP dissolve in intravenous solutions prior to administration. Our assessment indicates that visible and/or sub-visible particles that contain high levels of lauric, myristic and palmitic acids dissolve immediately upon dilution (at or exceeding two fold) regardless of the intravenous bag or solution type. Therefore, the risk is low of visible and/or sub-visible particles, comprised of FFAs in biopharmaceutical DPs, being intravenously administered to a patient.