A Quantitative Kinetic Study of Polysorbate Autoxidation: The Role of Unsaturated Fatty Acid Ester Substituents

Visible light triggers the formation of reactive oxygen species in monoclonal antibody formulations

Most monoclonal antibody formulations require the presence of a surfactant, such as polysorbate, to ensure protein stability. The presence of high concentrations of polysorbate have been shown to enhance photooxidation of certain protein drug products when exposed to visible light. The current literature, however, suggest that photooxidation of polysorbate only occurs when exposed to visible light in combination with UVA light. This is probable as peroxides present in polysorbate solutions can be cleaved homolytically in the UVA region. In the visible region, photooxidation is not expected to occur as cleavage of peroxides is not expected at these wavelengths. This report presents findings suggesting that the presence of one or more photosensitiser(s) in polysorbate must be a cause and is required to catalyse the aerobic oxidation of polysorbate solutions upon exposure to visible light. Our investigation aimed to clarify the mechanism(s) of polysorbate photooxidation and explore the kinetics and the identity of the generated radicals and their impact on monoclonal antibody (mAb) degradation. Our study reveals that when polysorbate solutions are exposed to visible light between 400 - 800 nm in the absence of proteins, discolouration, radical formation, and oxygen depletion occur. We discuss the initial formation of reactive species, most likely occurring directly after reaction of molecular oxygen, with the presence of a triplet state photosensitiser, which is generated by intersystem crossing of the excited singlet state. When comparing the photooxidation of PS20 and PS80 in varying quality grades, we propose that singlet oxygen possesses potential for reacting with unsaturated fatty acids in PS80HP, however, PS20HP itself exhibited no measurable oxidation under the tested conditions. The study's final part delves into the photooxidation behaviour of different PS grades, examining its influence on the integrity of a mAb in the formulation. Finally, we examined the effect of photooxidation on the integrity of monoclonal antibodies. Our findings show that the exposure to visible light in polysorbate-containing mAb solutions at high PS concentrations of 4 mg·ml-1 results in increased monoclonal antibody degradation, highlighting the need for cautious evaluation of the correct PS concentration to stabilise protein therapeutics.

Unravelling the effect of droplet size on lipid oxidation in O/W emulsions by using microfluidics

Lipid oxidation in emulsions is hypothesised to increase with decreasing droplet size, as this increases the specific oil-water interfacial area, where lipid oxidation is expected to be initiated. In literature, however, contradictory results have been reported, which can be caused by confounding factors such as the oil droplet polydispersity and the distribution of components between the available phases. In this work, monodisperse surfactant-stabilised emulsions with highly controlled droplet sizes of 4.7, 9.1, and 26 µm were produced by microfluidic emulsification. We show that lipid oxidation increases with decreasing droplet size, which we ascribe to the increased contact area between lipids and continuous phase prooxidants. Besides, a significant amount of oxygen was consumed by oxidation of the surfactant itself (Tween 20), an effect that also increased with decreasing droplet size. These insights substantiate the importance of controlling droplet size for improving the oxidative stability of emulsions.

Lipid oxidation in emulsions: New insights from the past two decades

Lipid oxidation constitutes the main source of degradation of lipid-rich foods, including food emulsions. The complexity of the reactions at play combined with the increased demand from consumers for less processed and more natural foods result in additional challenges in controlling this phenomenon. This review provides an overview of the insights acquired over the past two decades on the understanding of lipid oxidation in oil-in-water (O/W) emulsions. After introducing the general structure of O/W emulsions and the classical mechanisms of lipid oxidation, the contribution of less studied oxidation products and the spatiotemporal resolution of these reactions will be discussed. We then highlight the impact of emulsion formulation on the mechanisms, taking into consideration the new trends in terms of emulsifiers as well as their own sensitivity to oxidation. Finally, novel antioxidant strategies that have emerged to meet the recent consumer's demand will be detailed. In an era defined by the pursuit of healthier, more natural, and sustainable food choices, a comprehensive understanding of lipid oxidation in emulsions is not only an academic quest, but also a crucial step towards meeting the evolving expectations of consumers and ensuring the quality and stability of lipid-rich food products.

Determining the Oxidation Mechanism through Radical Intermediates in Polysorbates 80 and 20 by Electron Paramagnetic Resonance Spectroscopy

Polysorbates 20 and 80 (PS20 and PS80) are added to many commercial biologic and vaccine pharmaceuticals. It is commonly known that these polysorbates undergo a radical oxidation mechanism; however, the identity of these radical intermediates has not been clearly determined. Furthermore, PS20 and PS80 differ by the presence of a lauric acid instead of an oleic acid, respectively. The oxidation of PS80 is thought to be centered around the double bond of the oleic acid even though PS20 also undergoes oxidation, making the mechanism of oxidation unclear for PS20. Using commercial stocks of PS20 and PS80 alkyl (R•), alkoxyl (C-O•) and peroxyl (C-OO•) radicals were detected by electron paramagnetic resonance spectroscopy likely originating from radical-initiating species already present in the material. When dissolved in water, the peroxyl radicals (C-OO•) originally in the stocks were not detected but poly(ethylene oxide) radicals were. An oxidative pathway for polysorbates was suggested based on the radical species identified in the polysorbate stock material and solutions.

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.

Comparative Stability Study of Polysorbate 20 and Polysorbate 80 Related to Oxidative Degradation

The surfactants polysorbate 20 (PS20) and polysorbate 80 (PS80) are utilized to stabilize protein drugs. However, concerns have been raised regarding the degradation of PSs in biologics and the potential impact on product quality. Oxidation has been identified as a prevalent degradation mechanism under pharmaceutically relevant conditions. So far, a systematic stability comparison of both PSs under pharmaceutically relevant conditions has not been conducted and little is known about the dependence of oxidation on PS concentration. Here, we conducted a comparative stability study to investigate (i) the different oxidative degradation propensities between PS20 and PS80 and (ii) the impact of PS concentration on oxidative degradation. PS20 and PS80 in concentrations ranging from 0.1 mg⋅mL-1 to raw material were stored at 5, 25, and 40 °C for 48 weeks in acetate buffer pH 5.5 and water, respectively. We observed a temperature-dependent oxidative degradation of the PSs with strong (40 °C), moderate (25 °C), and weak/no degradation (5 °C). Especially at elevated temperatures such as 40 °C, fast oxidative PS degradation processes were detected. In this case study, a stronger degradation and earlier onset of oxidation was observed for PS80 in comparison to PS20, detected via the fluorescence micelle assay. Additionally, degradation was found to be strongly dependent on PS concentration, with significantly less oxidative processes at higher PS concentrations. Iron impurities, oxygen in the vial headspaces, and the pH values of the formulations were identified as the main contributing factors to accelerate PS oxidation.

Extensive Characterization of Polysorbate 80 Oxidative Degradation Under Stainless Steel Conditions

Polysorbate-80 (PS-80) is a common surfactant used in biologics formulations. However, the tendency of oxidation to PS-80 when exposed to stainless steel surfaces brings various challenges during manufacturing processes, such as inconsistent shelf-life of PS-80 solutions, which can further impact the biologics and vaccines production. In this work, the root causes of PS-80 oxidation when in contact with stainless steel conditions were thoroughly investigated through the use of various complementary analytical techniques including U/HPLC-CAD, LC-MS, ICP-MS, peroxide assay, and EPR spectroscopy. The analytical tool kit used in this work successfully revealed a PS-80 degradation mechanism from the perspective of PS-80 content, PS-80 profile, iron content, peroxide production, and radical species. The combined datasets reveal that PS-80 oxidative degradation occurs in the presence of histidine and iron in addition to being combined with the hydroperoxides in PS-80 material. The oxidative pathway and potential degradants were identified by LC-MS. The PS-80 profile based on the U/HPLC-CAD assay provided an effective way to identify early-signs of PS-80 degradation. The results from a peroxide assay observed increased hydroperoxide along with PS-80 degradation. EPR spectra confirmed the presence of histidine-related radicals during PS-80 oxidation identifying how histidine is involved in the oxidation. All assays and findings introduced in this work will provide insight into how PS-80 oxidative degradation can be avoided, controlled, or detected. It will also provide valuable evaluations on techniques that can be used to identify PS-80 degradation related events that occur during the manufacturing process.

The role of aggregation and ionization in the chemical instability of Amphotericin B in aqueous methanol

Amphotericin B (AmB) is a potent antimicrobial agent used in clinical practice. Nevertheless, the mechanism of its aqueous instability remains not yet fully understood, especially the role that its aggregation state plays in this process. Therefore, the current study used an aqueous methanol media to evaluate the AmB instability as a function of pH-, organic solvent- and concentration-dependent ionization and aggregation. To reach this goal, the aggregation status and instability were determined using UV-vis spectroscopy, LC-MS and HPLC. Moreover, not only the hydrolytic degradation products were identified by UV-vis spectroscopy and LC-MS, but also, the degradation rate constants were estimated by nonlinear regression. The results indicated that monomeric AmB was the predominant species under pH conditions, wherein the substrate was cationic (pH < 4) or anionic (pH > 9). On the other hand, aggregated AmB form was the predominant species for the zwitterionic substrate (at methanol concentration < 30 %_(v/v)). Anionic substrate degraded by specific base-catalyzed lactone hydrolysis. Oxidation accounted for the loss of zwitterionic substrate. Aggregated zwitterionic AmB exhibited lower stability than monomeric zwitterionic AmB under neutral pH conditions. These studies are a step forward in comprehending the degradation kinetics of AmB in aqueous medium. In fact, along with our previous research on AmB instability in oils, it leads to a better understanding of the AmB stability in complex systems with an oil-water interface, such as disperse lipid systems.

Characterization of radicals in polysorbate 80 using electron paramagnetic resonance (EPR) spectroscopy and spin trapping

Polysorbates are an important class of nonionic surfactants that are widely used to stabilize biopharmaceuticals. The degradation of polysorbate 20 and 80 and the related particle formation in biologics are heavily discussed in the pharmaceutical community. Although a lot of experimental effort was spent in the detailed study of potential degradation pathways, the underlying mechanisms are only sparsely understood. Besides enzymatic hydrolysis, another proposed mechanism is associated with radical-induced (auto)oxidation of polysorbates. To characterize the types and the origin of the involved radicals and their propagation in bulk material as well as in diluted polysorbate 80 solutions, we applied electron paramagnetic resonance (EPR) spectroscopy using a spin trapping approach. The prerequisite for a meaningful experiment using spin traps is an understanding of the trapping rate, which is an interplay of (i) the presence of the spin trap at the scene of action, (ii) the specific reactivity of the selected spin trap with a certain radical as well as (iii) the stability of the formed spin adducts (a slow decay rate). We discuss whether and to which extent these criteria are fulfilled regarding the identification of different radical classes that might be involved in polysorbate oxidative degradation processes. The ratio of different radicals for different scenarios was determined for various polysorbate 80 quality grades in bulk material and in aqueous solution, showing differences in the ratio of present radicals. Possible correlations between the radical content and product parameters such as the quality grade, the manufacturing date, the manufacturer, the initial peroxide content according to the certificate of analysis of polysorbate 80 are discussed.

Alternative Excipients for Protein Stabilization in Protein Therapeutics: Overcoming the Limitations of Polysorbates

Given their safety and efficiency in protecting protein integrity, polysorbates (PSs) have been the most widely used excipients for the stabilization of protein therapeutics for years. In recent decades, however, there have been numerous reports about visible or sub-visible particles in PS-containing biotherapeutic products, which is a major quality concern for parenteral drugs. Alternative excipients that are safe for parenteral administration, efficient in protecting different protein drugs against various stress conditions, effective in protein stabilization in high-concentrated liquid formulations, stable under the storage conditions for the duration of the product's shelf-life, and compatible with other formulation components and the primary packaging are highly sought after. The aim of this paper is to review potential alternative excipients from different families, including surfactants, carbohydrate- and amino acid-based excipients, synthetic amphiphilic polymers, and ionic liquids that enable protein stabilization. For each category, important characteristics such as the ability to stabilize proteins against thermal and mechanical stresses, current knowledge related to the safety profile for parenteral administration, potential interactions with other formulation components, and primary packaging are debated. Based on the provided information and the detailed discussion thereof, this paper may pave the way for the identification or development of efficient excipients for biotherapeutic protein stabilization.

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.

Poloxamer 188 as surfactant in biological formulations - An alternative for polysorbate 20/80?

Surfactants are used to stabilize biologics. Particularly, polysorbates (Tween® 20 and Tween® 80) dominate the group of surfactants in protein and especially antibody drug products. Since decades drug developers rely on the ethoxylated sorbitan fatty acid ester mixtures to stabilize sensitive molecules such as proteins. Reasons are (i) excellent stabilizing properties, and (ii) well recognized safety and tolerability profile of these polysorbates in humans, especially for parenteral applications. However, over the past decade concerns regarding the stability of these two polysorbates were raised. The search of alternatives with preferably less reservations concerning degradation and product quality reducing issues leads, among others, to poloxamer 188 (e.g. Kolliphor® P188), a nonionic triblock-copolymer surfactant. This review sums up our current knowledge related to the characterization and physico-chemical properties of poloxamer 188, its analytics and stability properties for biological formulations. Furthermore, the advantages and disadvantages as a suitable polysorbate-alternative for the stabilization of biologics are discussed.

The degradation of poloxamer 188 in buffered formulation conditions

Poloxamer 188 (P188) as a non-ionic surfactant is used in proteinaceous formulations to prevent protein adsorption to hydrophobic surfaces and unfolding at interfaces, preventing the formation of aggregates and particles. Its chemical intactness is crucial to the stability of drug products due to its protecting effects at interfaces. In order to identify and mitigate potential risks that might cause the degradation of P188 during the manufacturing process and storage, in the current work, the stability of P188 was investigated by forced degradation in buffered formulation conditions via oxidation and thermal stress conditions. The process of degradation was monitored through the dedicated liquid adsorption chromatography (LAC) with high sensitivity, and the degradants were characterized by high-resolution mass spectrometry. Results suggest that the vulnerability of P188 is largely related to the buffer conditions. Histidine promotes degradation in the presence of hydroxyl radicals but inhibits the degradation in the presence of H2O2 and alkyl radicals. In thermal stress conditions, histidine protects P188 from degradation at 40 °C, and activates its decay only at higher temperature, like 60 °C.

Monitoring polysorbate hydrolysis in therapeutic proteins using an ultrasensitive extraction-free fatty acid quantitation method

Polysorbates (PSs) are surfactants commonly added to therapeutic protein drug product formulations to protect proteins from denaturation and aggregation during storage, transportation, and delivery. However, enzymatic hydrolysis of PSs has been recognized as the primary route of PS degradation in monoclonal antibody formulations, resulting in the release of free fatty acids that drive undesired particulate formation. Here, we present a rapid lipase activity assay with optimized incubation conditions for accurate quantitation of free fatty acids without a fatty acid extraction step. This assay can detect low levels of PS degradation (0.000024% PS20 degradation) within 1 day with minimal sample preparation. The levels of released free fatty acids were found to strongly correlate with the degree of PS20 degradation. The case study described herein suggests that this approach can detect low levels of PS20 degradation caused by sub-ppm lipase levels within 1 day, compared with the duration of 14 days needed for PS degradation assays based on two-dimensional liquid chromatography-charge aerosol detection.

Clozapine-Encapsulated Binary Mixed Micelles in Thermosensitive Sol-Gels for Intranasal Administration

(1) Background: Clozapine is the most effective antipsychotic. It is, however, associated with many adverse drug reactions. Nose-to-brain (N2B) delivery offers a promising approach. This study aims to develop clozapine-encapsulated thermosensitive sol-gels for N2B delivery. (2) Methods: Poloxamer 407 and hydroxypropyl methylcellulose were mixed and hydrated with water. Glycerin and carbopol solutions were added to the mixture and stirred overnight at 2-8 °C. Clozapine 0.1% w/w was stirred with polysorbate 20 (PS20) or polysorbate 80 (PS80) at RT (25 °C) before being added to the polymer solution. The final formulation was made to 10 g with water, stirred overnight at 2-8 °C and then adjusted to pH 5.5. (3) Results: Formulations F3 (3% PS20) and F4 (3% PS80) were selected for further evaluation, as their gelation temperatures were near 28 °C. The hydrodynamic particle diameter of clozapine was 18.7 ± 0.2 nm in F3 and 20.0 ± 0.4 nm in F4. The results show a crystallinity change in clozapine to amorphous. Drug release studies showed a 59.1 ± 3.0% (F3) and 53.1 ± 2.7% (F4) clozapine release after 72 h. Clozapine permeated after 8 h was 20.8 ± 3.0% (F3) and 17.8 ± 3.1% (F4). The drug deposition was higher with F4 (144.8 ± 1.4 µg/g) than F3 (110.7 ± 2.7 µg/g). Both sol-gels showed no phase separation after 3 months. (4) Conclusions: Binary PS80-P407 mixed micelles were more thermodynamically stable and rigid due to the higher synergism of both surfactants. However, binary mixed PS20-P407 micelles showed better drug permeation across the nasal mucosa tissue and may be a preferable carrier system for the intranasal administration of clozapine.

Photo-Oxidation of Therapeutic Protein Formulations: From Radical Formation to Analytical Techniques

UV and ambient light-induced modifications and related degradation of therapeutic proteins are observed during manufacturing and storage. Therefore, to ensure product quality, protein formulations need to be analyzed with respect to photo-degradation processes and eventually protected from light exposure. This task usually demands the application and combination of various analytical methods. This review addresses analytical aspects of investigating photo-oxidation products and related mediators such as reactive oxygen species generated via UV and ambient light with well-established and novel techniques.

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.

Advancing Structure Characterization of PS-80 by Charge-Reduced Mass Spectrometry and Software-Assisted Composition Analysis

The commercially available Polysorbate 80 (PS-80) is a highly heterogeneous product. It is a complex and structurally diverse mixture consisting of polymeric species containing polyoxyethylenes (POEs), fatty acid esters, with/or without a carbohydrate core. The core is primarily sorbitan, with some isosorbide and sorbitol. Depending on the sources of fatty acids and the degrees of esterification, multiple combinations of fatty acid esters are commonly observed. A number of POE intermediates, such as polyoxyethylene glycols, POE-sorbitans, POE-isosorbides, and an array of fatty acid esters from these intermediates remain in the raw material as well. The complex composition of PS-80 is difficult to control and poses a significant characterization challenge for its use in the pharmaceutical industry. Here, we present a novel solution for PS-80 characterization using ultra high-performance liquid chromatography coupled with charge-reduction high resolution mass spectrometry. Post column co-infusion of triethylamine focused the signal into mainly singly charged molecular ions and reduced the extent of in-source fragmentation, resulting in a simpler ion map and enhanced measurement of PS-80 species. The data processing workflow is designed to programmatically identify PS-80 component classes and reduce the burden of manually analyzing complex MS data. The 2-dimensional graphical representation of the data helps visualize these features. Together, these innovative methodologies enabled us to analyze components in PS-80 with unprecedented detail and shall be a useful tool to study formulation and stability of pharmaceutical preparations. The power of this approach was demonstrated by comparing the composition of PS-80 obtained from different vendors.

Characterization of Polysorbate 80 by Liquid Chromatography-Mass Spectrometry to Understand Its Susceptibility to Degradation and Its Oxidative Degradation Pathway

A liquid chromatography-mass spectrometry (LC-MS) method was developed to provide a fingerprint of polysorbate 80 (PS80) subspecies that enables identification of PS80 degradation pathway. The developed method demonstrates unique monoester peak profile of PS80 from different vendors, attributed by differences in relative abundance of the fatty acid monoesters. The LC-MS method was also applied to examine the susceptibility of PS80, at different grades, to auto-oxidation and hydrolysis. PS80 oxidative degradation induced by iron or occurred in open bottle without nitrogen overlay was found to follow the same pathway, but at a much faster rate in the former scenario. The oxidation preferentially occurs at the double bond of fatty acid chains, thus providing explanation on the faster degradation observed in PS80 at Chinese Pharmacopia (ChP) grade than at multi-compendial (MC) grade. In contrast, the difference in susceptibility of MC and ChP grade PS80 against esterase-induced hydrolysis in placebo was not pronounced. The method was also able to provide a fingerprint to identify both PS80 hydrolysis and oxidation in mAb drug product stability samples, but it required a solid phase extraction step to remove protein prior to the analysis.

Enhancement and analysis of Anthracene degradation by Tween 80 in LMS-HOBt

This study examines the specific effect of Tween 80 on the conversion of anthracene (ANT) in laccase medium system regarding surfactant chemical changes and mechanism. The conversion rate and degradation products of ANT were investigated in different concentrations of Tween 80 solution. Between Tween 80 concentration 0-40 critical micelle concentrations (CMC), the kinetic parameter-k (h-1) and corresponding half-life T1/2 decreased with increasing concentration. When Tween 80 was above 20 CMC the laccase-medium system converted > 95% of ANT to anthraquinone within 12 h. During the entire enzymatic reaction, the laccase activity in the system increased with increasing Tween 80 concentration. Combined with GC/MS analysis of the product, it was speculated that hydrogens belonging to the ether-oxygen bond and carbon-carbon double bond α-CH of Tween 80, were removed by the laccase-media system, promoting its degradation. Additionally, enhanced activity caused by oxygen free radicals (ROS) such as RO• and ROO•, continuously oxidized Tween 80, which in turn produced free radicals while converting ANT. This study provides new theoretical support toward the application of surfactants in the elimination of polycyclic aromatic hydrocarbons.

4-Hydroxynonenal is An Oxidative Degradation Product of Polysorbate 80

INTRODUCTION

Polysorbates (PS) are used in biopharmaceuticals to stabilize therapeutic proteins. Oxidative degradation of (poly)unsaturated fatty acids (PUFAs) contained in PS was shown to lead to α,β-unsaturated carbonyls.

AIM

The n-6-PUFA linoleic acid accounts for up to 18% of all FAs contained in multi-compendial grade PS80. 4-Hydroxynonenal (HNE) is highly reactive towards nucleophilic amino acids, potentially leading to covalent protein modifications. This study tests whether HNE may be a pharmaceutically relevant PS80 peroxidation product.

METHODS

Since HNE was not directly detectable in the PS80 matrix by UV and MS, a new quantification method was established. After derivatization with 2,4-dinitrophenyl hydrazine (DNPH) and extraction of the formed hydrazone with a salting-out assisted liquid-liquid extraction, the HNE-DNPH adduct was analyzed by multiple reaction monitoring. Kinetic oxidation studies were conducted incubating PS80 in presence and absence of the antioxidant butylhydroxytoluene (BHT).

RESULTS

HNE was confirmed as PS80 degradant in oxidatively stressed samples. BHT was shown to prevent its formation.

CONCLUSION

HNE is a detectable PS80 degradation product raising questions about the potential impact on critical quality attributes of biopharmaceuticals formulated with PS80. Addition of BHT prevented HNE formation under oxidative stress. Consequently, BHT might be a valuable additive in PS used in biopharmaceuticals.

Degradation of polysorbates 20 and 80 catalysed by histidine chloride buffer

Polysorbates are amphiphilic, non-ionic surfactants, and they represent one of the key components of biopharmaceuticals. They serve as stabilisers, and their degradation can cause particle formation, which has been an industry-wide issue over the past decade. To determine the influence of the buffers most frequently used in biopharmaceuticals on polysorbate degradation, an accelerated stability study was carried out using placebo formulations containing 0.02% polysorbates and 20 mM buffers (pH 5.5, 6.5). These included histidine chloride, sodium citrate, sodium succinate and sodium phosphate buffers. The rate of polysorbate degradation was highest in histidine chloride buffer, and therefore we further focused on the mechanism here. The predominant degradation pathway of polysorbates in this buffer was ester hydrolysis, catalysed by the imidazole moiety of the histidine. Interestingly, the presence of therapeutic proteins in the formulations slowed histidine-catalysed degradation of polysorbates in 50% of cases, with negligible degradation seen otherwise. This emphasises the complex nature of the interactions between the components of biopharmaceutical drug products. Nonetheless, there are disadvantages of using histidine chloride buffers in biopharmaceuticals that contain polysorbates. Careful consideration should be given to selection of excipients used in parenteral formulations, whereby compatibility between buffer and surfactant is of key importance.

Protein Formulations Containing Polysorbates: Are Metal Chelators Needed at All?

Proteins are prone to post-translational modifications at specific sites, which can affect their physicochemical properties, and consequently also their safety and efficacy. Sources of post-translational modifications include oxygen and reactive oxygen species. Additionally, catalytic amounts of Fe(II) or Cu(I) can promote increased activities of reactive oxygen species, and thus catalyse the production of particularly reactive hydroxyl radicals. When oxidative post-translational modifications are detected in the biopharmaceutical industry, it is common practice to add chelators to the formulation. However, the resultant complexes with metals can be even more damaging. Indeed, this is supported here using an ascorbate redox system assay and peptide mapping. Ethylenediaminetetraacetic acid (EDTA) addition strongly accelerated the formation of hydroxyl radicals in an iron-ascorbate system, while diethylenetriaminepentaacetic acid (DTPA) addition did not. When Fe(III) was substituted with Cu(II), EDTA addition almost stopped hydroxyl radical production, whereas DTPA addition showed continued production, but at a reduced rate. Further, EDTA accelerated metal-catalysed oxidation of proteins, and thus did not protect them from Fe-mediated oxidative damage. As every formulation is unique, justification for EDTA or DTPA addition should be based on experimental data and not common practice.

Rational design to biologics development: The polysorbates point of view

Formulation development is an essential part of any biopharmaceuticals development programme, and this will affect quality, safety and efficacy of the final drug product. The vast majority of biopharmaceuticals on the market are therapeutic proteins; however, these are less stable compared to conventional pharmaceuticals. To counter aggregation, denaturation and surface adsorption of proteins in solution, surfactants are added to the formulations; however, the choice of the best formulation is a challenge that is faced during formulation development. Polysorbates are the most widely used surfactants in the pharmaceutical industry and are presented in >80% of commercial monoclonal antibody formulations. In this review, we provide a general overview of polysorbates and their issues, and the characteristics that have to be taken into account during formulation development. Degradation of polysorbates, namely by hydrolysis and/or oxidation, is one of the main concerns associated with their use. Furthermore, degradation of polysorbates is determined by formulation composition, pH and storage conditions, therefore underlining the importance and complexity of protein formulation development using polysorbates. A need-based approach should be used for correct selection of excipients in protein formulations that contain polysorbates.

Cis/Trans Isomerization of Unsaturated Fatty Acids in Polysorbate 80 During Light Exposure of a Monoclonal Antibody-Containing Formulation

Light exposure of a monoclonal antibody formulation containing polysorbate 80 (PS80) leads to cis/trans isomerization of monounsaturated and polyunsaturated fatty acids. This cis/trans isomerization was monitored by positive electrospray ionization mass spectrometry of intact PS80 components as well as by negative ion electrospray ionization mass spectrometry analysis of free fatty acids generated via esterase-catalyzed hydrolysis. The light-induced cis/trans isomerization of unsaturated fatty acids in PS80 required the presence of the monoclonal antibody, or, at a minimum (for mechanistic studies), a combination of N-acetyltryptophan amide and glutathione disulfide, suggesting the involvement of thiyl radicals generated by photoinduced electron transfer from Trp to the disulfide. Product analysis confirmed the conversion of PS80-bound oleic acid to elaidic acid; furthermore, together with linoleic acid, we detected conjugated linoleic acids in PS80, which underwent light-induced cis/trans isomerization.

Characterization of therapeutic antibodies and related products by two-dimensional liquid chromatography coupled with UV absorbance and mass spectrometric detection

The development of analytical tools for the characterization of large biomolecules is an emerging and rapidly evolving area. This development activity is motivated largely by the current trend involving the increase in development and use of large biomolecules for therapeutic uses. Given the inherent complexity of these biomolecules, which arises from their sheer size and possibilities for chemical modification as well as changes over time (e.g., through modification in solution, aggregation), two-dimensional liquid chromatography (2D-LC) has attracted considerable interest as an analytical tool to address the challenges faced in characterizing these materials. The immediate potential benefits of 2D-LC over conventional one-dimensional liquid chromatography in this context include: (1) higher overall resolving power; (2) complementary information gained from two dimensions of separation in a single analysis; and (3) enabling indirect coupling of separation modes that are inherently incompatible with mass spectrometric (MS) detection (e.g., ion-exchange, because of high-salt eluents) to MS through a more compatible second dimension separation such as reversed-phase LC. In this review we summarize the work in this area, most of which has occurred in the past five years. Although the future is bright for further development in this area, some challenges have already been addressed through new 2D-LC methods. These include: (1) deep characterization of monoclonal antibodies to understand charge heterogeneity, glycosylation patterns, and other modifications; (2) characterization of antibody-drug conjugates to understand the extent and localization of small molecule conjugation; (3) detailed study of excipients in protein drug formulations; and (4) detection of host-cell proteins on biotherapeutic molecule preparations. We fully expect that in the near future we will see this list expanded, and that continued development will lead to methods with further improved performance metrics.

A plasmonic nanosensor for lipase activity based on enzyme-controlled gold nanoparticles growth in situ

A plasmonic nanosensor for lipase activity was developed based on one-pot nanoparticle growth. Tween 80 was selected not only as the substrate for lipase recognition but also as the reducing and stabilizing agent for the sensor fabrication. The different molecular groups in Tween 80 could have different roles in the fabrication procedure; the H2O2 produced by the autoxidation of the ethylene oxide subunits in Tween 80 could reduce the AuCl4(-) ions to Au atoms, meanwhile, the lipase could hydrolyze its carboxyl ester bond, which could, in turn, control the rate of nucleation of the gold nanoparticles (AuNPs) and tailor the localized surface plasmon resonance (LSPR) of the AuNP transducers. The color changes, which depend on the absence or presence of the lipase, could be used to sense the lipase activity. A linear response ranging from 0.025 to 4 mg mL(-1) and a detection limit of the lipase as low as 3.47 μg mL(-1) were achieved. This strategy circumvents the problems encountered by general enzyme assays that require sophisticated instruments and complicated assembling steps. The methodology can benefit the assays of heterogeneous-catalyzed enzymes.

The influence of polysorbate 80 on the radiochemical synthesis of a PET tracer in the FASTlab

PURPOSE

The aim of current study was to investigate the influence of a common non-ionic surfactant, polysorbate 80 (PS80), on radioactive labelling process of a novel PET tracer, [(18)F]Flutemetamol.

METHODS

Ferrous oxidation-xylenol orange (FOX) assay, in addition to UV/VIS and (1)H NMR spectroscopies were applied to characterise the composition of the PS80 solution after storage. Multivariate Curve Resolution (MCR) and PLS analysis was used to establish correlation between quality of the PS80 solution and the RCP obtained after labelling.

RESULTS

The levels of unsaturated fatty acid moieties of PS80 were negatively correlated to RCP of [(18)F]Flutemetamol after synthesis. This explains the slight increase in RCP when stored PS80 solutions were applied in the synthesis. The mechanism behind this observation is suggested to be related to radiation induced radical formation in the unsaturated fatty acids, which subsequently causes instability of the PET tracer. UV/VIS spectroscopy was demonstrated to have the ability as a possible control tool for quality assurance of the studied radioactive labelling process.

CONCLUSIONS

The presence of unsaturated fatty acid moieties in PS80 was found to be one of the most important factors responsible for the reduction in RCP of [(18)F]Flutemetamol after synthesis.

Discovery of a chemical modification by citric acid in a recombinant monoclonal antibody

Recombinant therapeutic monoclonal antibodies exhibit a high degree of heterogeneity that can arise from various post-translational modifications. The formulation for a protein product is to maintain a specific pH and to minimize further modifications. Generally Recognized as Safe (GRAS), citric acid is commonly used for formulation to maintain a pH at a range between 3 and 6 and is generally considered chemically inert. However, as we reported herein, citric acid covalently modified a recombinant monoclonal antibody (IgG1) in a phosphate/citrate-buffered formulation at pH 5.2 and led to the formation of so-called "acidic species" that showed mass increases of 174 and 156 Da, respectively. Peptide mapping revealed that the modification occurred at the N-terminus of the light chain. Three additional antibodies also showed the same modification but displayed different susceptibilities of the N-termini of the light chain, heavy chain, or both. Thus, ostensibly unreactive excipients under certain conditions may increase heterogeneity and acidic species in formulated recombinant monoclonal antibodies. By analogy, other molecules (e.g., succinic acid) with two or more carboxylic acid groups and capable of forming an anhydride may exhibit similar reactivities. Altogether, our findings again reminded us that it is prudent to consider formulations as a potential source for chemical modifications and product heterogeneity.

Searching for life on Mars: degradation of surfactant solutions used in organic extraction experiments

Life-detection instruments on future Mars missions may use surfactant solutions to extract organic matter from samples of martian rocks. The thermal and radiation environments of space and Mars are capable of degrading these solutions, thereby reducing their ability to dissolve organic species. Successful extraction and detection of biosignatures on Mars requires an understanding of how degradation in extraterrestrial environments can affect surfactant performance. We exposed solutions of the surfactants polysorbate 80 (PS80), Zonyl FS-300, and poly[dimethylsiloxane-co-[3-(2-(2-hydroxyethoxy)ethoxy)propyl]methylsiloxane] (PDMSHEPMS) to elevated radiation and heat levels, combined with prolonged storage. Degradation was investigated by measuring changes in pH and electrical conductivity and by using the degraded solutions to extract a suite of organic compounds spiked onto grains of the martian soil simulant JSC Mars-1. Results indicate that the proton fluences expected during a mission to Mars do not cause significant degradation of surfactant compounds. Solutions of PS80 or PDMSHEPMS stored at -20 °C are able to extract the spiked standards with acceptable recovery efficiencies. Extraction efficiencies for spiked standards decrease progressively with increasing temperature, and prolonged storage at 60°C renders the surfactant solutions ineffective. Neither the presence of ascorbic acid nor the choice of solvent unequivocally alters the efficiency of extraction of the spiked standards. Since degradation of polysorbates has the potential to produce organic compounds that could be mistaken for indigenous martian organic matter, the polysiloxane PDMSHEPMS may be a superior choice of surfactant for the exploration of Mars.