The Role of Polysorbate 80 and HPβCD at the Air-Water Interface of IgG Solutions

Understanding Glucagon Aggregation: In Silico Insights and Experimental Validation

Peptide aggregation poses a significant challenge in biopharmaceutical development and neurodegenerative diseases. This study combines computational simulations and experimental validation to uncover the underlying mechanisms and countermeasures for the aggregation of glucagon, a peptide with a high tendency to aggregate. In silico simulations demonstrate that lactose and 2-hydroxypropyl-β-cyclodextrin (2-HPβCD) influence glucagon aggregation differently: lactose stabilizes glucagon by increasing the α-helical content, while 2-HPβCD disrupts protein-protein interactions. According to the simulations, 2-HPβCD is particularly effective at preserving the monomeric form of glucagon. Experimental validation with microfluidic modulation spectroscopy (MMS) confirms these findings, showing that glucagon in the presence of 2-HPβCD remains structurally stable, supporting the antiaggregation effect of this excipient. This research provides essential insights into glucagon aggregation obtained through a new powerful tool for monitoring the critical properties of peptide aggregation, suggesting new strategies for addressing this challenge in therapeutic peptide development.

Evaluating the Potential of Cyclodextrins in Reducing Aggregation of Antibody-Drug Conjugates with Different Payloads

Cyclodextrins (CDs) are versatile agents used to solubilize small drugs and stabilize proteins. This dual functionality may be particularly beneficial for antibody-drug conjugates (ADCs), as CDs may "mask" the hydrophobicity of the drug payloads. In this study, we explored the effect of CDs on the physical stability of ADCs composed of the same antibody but with different payloads (maytansinoid, auristatin, and fluorophore payloads). The aggregation of ADCs was evaluated under shaking stress conditions and elevated temperatures using size-exclusion chromatography, turbidity, and backgrounded membrane imaging. Our results showed that hydroxypropyl-(HP)-CDs effectively stabilized all ADCs during shaking stress, with increasing stabilization in the order of HPαCD < HPγCD < HPβCD at concentrations of 7.5 mM and (near) complete stabilization at 75 mM. Native CDs without surface activity also stabilized certain ADCs, although less effectively than HP-CDs under agitation stress. During quiescent incubation, the HP-CD effects were small for most ADCs. However, for an ADC with a fluorophore payload that rapidly aggregated after conjugation, HPγCD substantially reduced aggregate levels, in line with fluorescence data supporting CD-ADC interactions. In contrast, sulfobutylether-β-CD (SBEβCD) increased the aggregation rates in all ADCs under all stress conditions. In conclusion, this study highlights the potential of appropriate CD formulations to improve the physical stability of ADCs.

Investigation on the Combined Effect of Hydroxypropyl Beta-Cyclodextrin (HPβCD) and Polysorbate in Monoclonal Antibody Formulation

Monoclonal antibodies require careful formulation due to their inherent stability limitations. Polysorbates are commonly used to stabilize mAbs, but they are prone to degradation, which results in unwanted impurities. KLEPTOSE® HPβCD (hydroxypropyl beta-cyclodextrin) has functioned as a stable stabilizer for protein formulations in our previous research. The current study investigates the collaborative impact of combining polysorbates and HPβCD as excipients in protein formulations. The introduction of HPβCD in formulations showed it considerably reduced aggregation in two model proteins, bevacizumab and ipilimumab, following exposure to various stress conditions. The diffusion interaction parameter revealed a reduction in protein-protein interactions by HPβCD. In bevacizumab formulations, the subvisible particle counts per 0.4 mL of samples in commercial formulations vs. formulations containing both HPβCD and polysorbates subjected to distinct stressors were as follows: agitation, 87,308 particles vs. 15,350 particles; light, 25,492 particles vs. 6765 particles; and heat, 1775 particles vs. 460 particles. Isothermal titration calorimetry (ITC) measurement indicated a weak interaction between PS 80 and HPβCD, with a KD value of 74.7 ± 7.5 µM and binding sites of 5 × 10-3. Surface tension measurements illustrated that HPβCD enhanced the surface activity of polysorbates. The study suggests that combining these excipients can improve mAb stability in formulations, offering an alternative for the biopharmaceutical industry.

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.

Topical ocular protein delivery based on protein powder suspensions in semifluorinated alkanes

The field of ocular diseases, specifically retinal diseases is a successful target area for protein drugs with various marketed products. Besides the intraocular treatment of the retina, the topical treatment of corneal or conjunctival diseases is a promising approach. Topical ocular protein formulations face the challenges of poor penetration and potentially low stability. In this study we tested suspensions based on the semifluorinated alkane F6H8 to improve the topical ocular protein delivery. Such suspensions are well known for the increased protein stability compared to aqueous solutions. Furthermore, F6H8 is well known as vehicle for ocular delivery due to its easy spreading on the cornea. Penetration of a model mAb and its Fab fragment was tested in an ex vivo corneal penetration test. The amount of penetrated protein was increased when the protein powder suspensions were used compared to the respective aqueous solutions. Sodium caprate as penetration enhancer at 5mg/ml substantially increased the Fab fragment (7-fold) and the mAB (3-fold) concentration in the corneal tissue when applied as an aqueous solution. The effect was surprisingly more pronounced, when Fab fragment (31-fold) or mAb (13-fold) and the penetration enhancer were formulated as F6H8 suspensions. The same penetration enhancement from suspensions could be achieved with 2.5mg/ml, but the penetration was reduced compared to 2.5 mg/ml in the aqueous solution. A test based on stratified human keratinocytes did not indicate eye irritation by the tested formulations. Furthermore, stability studies for bevacizumab suspensions in semifluorinated alkanes were investigated and showed superior long-term stability compared to the marketed aqueous solution. Overall results demonstrate the high potential of topical ocular protein delivery using powder suspensions in non-aqueous vehicles based on semifluorinated alkanes.

Effect of Cosolutes on the Aggregation of a Tau Fragment: A Combined Experimental and Simulation Approach

The intrinsically disordered protein Tau represents the main component of neurofibrillary tangles that are a hallmark of Alzheimer's disease. A small fragment of Tau, known as paired helical filament 6 (PHF6), is considered to be important for the formation of the β-structure core of the fibrils. Here we study the aggregation of this fragment in the presence of different cosolutes, including urea, TMAO, sucrose and 2-hydroxypropyl-β-cyclodextrin (2-HPβCD), using both experiments and molecular dynamics simulations. A novel implicit solvation approach (MIST - Model with Implicit Solvation Thermodynamics) is used, where an energetic contribution based on the concept of transfer free energies describes the effect of the cosolutes. The simulation predictions are compared to thioflavin-T and atomic force microscopy results, and the good agreement observed confirms the predictive ability of the computational approach herein proposed. Both simulations and experiments indicate that PHF6 aggregation is inhibited in the presence of urea and 2-HPβCD, while TMAO and sucrose stabilize associated conformations. The remarkable ability of HPβCD to inhibit aggregation represents an extremely promising result for future applications, especially considering the widespread use of this molecule as a drug carrier to the brain and as a solubilizer/excipient in pharmaceutical formulations.

Exploring the Protein Stabilizing Capability of Surfactants Against Agitation Stress and the Underlying Mechanisms

The application of surfactants in liquid protein formulation is a common practice to protect proteins from liquid-air interface-induced protein aggregation. Typically, Polysorbate 20 or 80 are used, but degradation of these surfactants can result in particle formation and/or protein degradation. The purpose of the current study was to directly compare three alternative protein stabilizing molecules - Poloxamer 188, hydroxypropyl-cyclodextrin and a trehalose-based surfactant - to Polysorbate 80 for their capacities to reduce agitation-induced protein aggregation and particle formation; and furthermore, investigate their underlying protein stabilizing mechanisms. To this end, a small-volume, rapid agitation stress approach was used to quantify the molecules' abilities to stabilize two model proteins. This assay was presented to be a powerful tool to screen the protein stabilizing capability of surfactants using minimum of material and time. SEC, turbidity measurements and particle analysis showed an efficient protein stabilization of all tested surfactants as well as cyclodextrin. STD-NMR and dynamic surface tension measurements indicated the competitive surface adsorption to be the main protein stabilizing mechanism of the three surfactants tested. It might also play a role to some extent in the protein stabilization by HPβCD. However, additional mechanisms might also contribute to protein stabilization leaving room for further investigations.

Physical Instabilities of Therapeutic Monoclonal Antibodies: A Critical Review

The proteinaceous nature of monoclonal antibodies (mAbs) makes them highly sensitive to various physical and chemical conditions, thus leading to instabilities that are classified as physical and chemical instabilities. In this review, we are discussing in detail the physical instability of mAbs because a large number of articles previously published solely focus on the chemical aspect of the instability with little coverage on the physical side. The physical instabilities of mAbs are classified into denaturation and aggregation (precipitation, visible and subvisible particles). The mechanism involved in their formation is discussed in the article, along with the pathways correlating the denaturation of mAb or the formation of aggregates to immunogenicity. Further equations like Gibbs-Helmholtz involved in detecting and quantifying denaturation are discussed, along with various factors causing the denaturation. Moreover, questions related to aggregation like the types of aggregates and the pathway involved in their formation are answered in this article. Factors influencing the physical stability of the mAbs by causing denaturation or formation of aggregates involving the structure of the protein, concentration of mAbs, pH of the protein and the formulations, excipients involved in the formulations, salts added to the formulations, storage temperature, light and UV radiation exposure and processing factors are mentioned in this article. Finally, the analytical approaches used for detecting and quantifying the physical instability of mAbs at all levels of structural conformation like far and near UV, infrared spectroscopy, capillary electrophoresis, LC-MS, microflow imagining, circular dichroism and peptide mapping are discussed.

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.

Polysorbates versus Hydroxypropyl Beta-Cyclodextrin (HPβCD): Comparative Study on Excipient Stability and Stabilization Benefits on Monoclonal Antibodies

Polysorbates (PS 20 and PS 80) are the most widely used surfactants in biopharmaceutical formulations to protect proteins from denaturation, aggregation, and surface adsorption. To date, around 70% of marketed therapeutic antibodies contain either PS 20 or PS 80 in their formulations. However, polysorbates are chemically diverse mixtures, which are prone to degradation by oxidation and hydrolysis to produce peroxides and fatty acids, which, in turn, induce protein oxidation, aggregation, and insoluble particle formation. These will negatively impact protein quality and stability. Thus, polysorbate degradation has emerged as one of the major challenges in the development and commercialization of therapeutic protein products. KLEPTOSE^® HPβCD (hydroxypropyl beta-cyclodextrin), a new multifunctional excipient, has been shown to provide protein stabilization functions in biopharmaceutical downstream processes and in their final formulations. This study aims to evaluate HPβCD, a new molecule of its class, against polysorbates as a stabilizer in biologics formulations. In this study, the chemical stability of KLEPTOSE^® HPβCDs is compared with polysorbates (20 and 80) under various stress conditions. When subjected to heat stress, HPβCDs show little change in product recovery (90.7–100.7% recovery for different HPβCDs), while polysorbates 20 and 80 show significant degradation, with only 11.5% and 7.3% undegraded product remaining, respectively. When subjected to other chemical stressors, namely, autoclave, light, and oxidative stresses, HPβCD remains almost stable, while polysorbates show more severe degradation, with 95.5% to 98.8% remaining for polysorbate 20 and 85.5% to 97.4% remaining for polysorbate 80. Further, profiling characterization and degradation analysis reveal that chemical structures of HPβCDs remain intact, while polysorbates undergo significant hydrolytic degradation and oxidation. Lastly, the physicochemical stability of monoclonal antibodies in formulations is investigated. When subjected to light stress, adalimumab, as a model mAb, formulated in the presence of HPβCD, shows a significant decrease in protein aggregation, and superior monomer and total protein recovery compared to PS 80-containing formulations. HPβCD also reduces both agitation and thermal stress-induced protein aggregation and prevents subvisible particle formation compared to PS 80.

Hydroxylpropyl-β-cyclodextrin as Potential Excipient to Prevent Stress-Induced Aggregation in Liquid Protein Formulations

Due to the growing demand for patient-friendly subcutaneous dosage forms, the ability to increasing protein solubility and stability in formulations to deliver on the required high protein concentrations is crucial. A common approach to ensure protein solubility and stability in high concentration protein formulations is the addition of excipients such as sugars, amino acids, surfactants, approved by the Food and Drug Administration. In a best-case scenario, these excipients fulfil multiple demands simultaneously, such as increasing long-term stability of the formulation, reducing protein adsorption on surfaces/interfaces, and stabilizing the protein against thermal or mechanical stress. 2-Hydroxylpropyl-β-cyclodextrin (derivative of β-cyclodextrin) holds this potential, but has not yet been sufficiently investigated for use in protein formulations. Within this work, we have systematically investigated the relevant molecular interactions to identify the potential of Kleptose^®HPB (2-hydroxylpropyl-β-cyclodextrin from Roquette Freres, Lestrem, France) as “multirole” excipient within liquid protein formulations. Based on our results three factors determine the influence of Kleptose^®HPB on protein formulation stability: (1) concentration of Kleptose^®HPB, (2) protein type and protein concentration, and (3) quality of the protein formulation. Our results not only contribute to the understanding of the relevant interactions but also enable the target-oriented use of Kleptose^®HPB within formulation design.

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.

Gelatin Stabilizes Nebulized Proteins in Pulmonary Drug Delivery against COVID-19

Delivering medication to the lungs via nebulization of pharmaceuticals is a noninvasive and efficient therapy route, particularly for respiratory diseases. The recent worldwide severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) pandemic urges the development of such therapies as an effective alternative to vaccines. The main difficulties in using inhalation therapy are the development of effective medicine and methods to stabilize the biological molecules and transfer them to the lungs efficiently following nebulization. We have developed a high-affinity angiotensin-converting enzyme 2 (ACE2) receptor-binding domain (RBD-62) that can be used as a medication to inhibit infection with SARS-CoV-2 and its variants. In this study, we established a nebulization protocol for drug delivery by inhalation using two commercial vibrating mesh (VM) nebulizers (Aerogen Solo and PARI eFlow) that generate similar mist size distribution in a size range that allows efficient deposition in the small respiratory airway. In a series of experiments, we show the high activity of RBD-62, interferon-α2 (IFN-α2), and other proteins following nebulization. The addition of gelatin significantly stabilizes the proteins and enhances the fractions of active proteins after nebulization, minimizing the medication dosage. Furthermore, hamster inhalation experiments verified the feasibility of the protocol in pulmonary drug delivery. In short, the gelatin-modified RBD-62 formulation in coordination with VM nebulizer can be used as a therapy to cure SARS-CoV-2.

No ordinary proteins: Adsorption and molecular orientation of monoclonal antibodies

The interaction of monoclonal antibodies (mAbs) with air/water interfaces plays a crucial role in their overall stability in solution. We aim to understand this behavior using pendant bubble measurements to track the dynamic tension reduction and x-ray reflectivity to obtain the electron density profiles (EDPs) at the surface. Native immunoglobulin G mAb is a rigid molecule with a flat, "Y" shape, and simulated EDPs are obtained by rotating a homology construct at the surface. Comparing simulations with experimental EDPs, we obtain surface orientation probability maps showing mAbs transition from flat-on Y-shape configurations to side-on or end-on configurations with increasing concentration. The modeling also shows the presence of β sheets at the surface. Overall, the experiments and the homology modeling elucidate the orientational phase space during different stages of adsorption of mAbs at the air/water interface. These finding will help define new strategies for the manufacture and storage of antibody-based therapeutics.

Force Field Parameterization for the Description of the Interactions between Hydroxypropyl-β-Cyclodextrin and Proteins

Cyclodextrins are cyclic oligosaccharides, widely used as drug carriers, solubilizers, and excipients. Among cyclodextrins, the functionalized derivative known as hydroxypropyl-β-cyclodextrin (HPβCD) offers several advantages due to its unique structural features. Its optimal use in pharmaceutical and medical applications would benefit from a molecular-level understanding of its behavior, as can be offered by molecular dynamics simulations. Here, we propose a set of parameters for all-atom simulations of HPβCD, based on the ADD force field for sugars developed in our group, and compare it to the original CHARMM36 description. Using Kirkwood-Buff integrals of binary HPβCD-water mixtures as target experimental data, we show that the ADD-based description results in a considerably improved prediction of HPβCD self-association and interaction with water. We then use the new set of parameters to characterize the behavior of HPβCD toward the different amino acids. We observe pronounced interactions of HPβCD with both polar and nonpolar moieties, with a special preference for the aromatic rings of tyrosine, phenylalanine, and tryptophan. Interestingly, our simulations further highlight a preferential orientation of HPβCD's hydrophobic cavity toward the backbone atoms of amino acids, which, coupled with a favorable interaction of HPβCD with the peptide backbone, suggest a propensity for HPβCD to denature proteins.

The Role of Cyclodextrins against Interface-Induced Denaturation in Pharmaceutical Formulations: A Molecular Dynamics Approach

Protein-based pharmaceutical products are subject to a variety of environmental stressors, during both production and shelf-life. In order to preserve their structure, and, therefore, functionality, it is necessary to use excipients as stabilizing agents. Among the eligible stabilizers, cyclodextrins (CDs) have recently gained interest in the scientific community thanks to their properties. Here, a computational approach is proposed to clarify the role of β-cyclodextrin (βCD) and 2-hydroxypropyl-β-cyclodextrin (HPβCD) against granulocyte colony-stimulating (GCSF) factor denaturation at the air–water and ice–water interfaces, and also in bulk water at 300 or 260 K. Both traditional molecular dynamics (MD) simulations and enhanced sampling techniques (metadynamics, MetaD) are used to shed light on the underlying molecular mechanisms. Bulk simulations revealed that CDs were preferentially included within the surface hydration layer of GCSF, and even included some peptide residues in their hydrophobic cavity. HPβCD was able to stabilize the protein against surface-induced denaturation in proximity of the air–water interface, while βCD had a destabilizing effect. No remarkable conformational changes of GCSF, or noticeable effect of the CDs, were instead observed at the ice surface. GCSF seemed less stable at low temperature (260 K), which may be attributed to cold-denaturation effects. In this case, CDs did not significantly improve conformational stability. In general, the conformationally altered regions of GCSF seemed not to depend on the presence of excipients that only modulated the extent of destabilization with either a positive or a negative effect.

HP-β-CD for the formulation of IgG and Ig-based biotherapeutics

The main challenge to develop HCF for IgG and Ig-based therapeutics is to achieve essential solubility, viscosity and stability of these molecules in order to maintain product quality and meet regulatory requirement during manufacturing, production, storage, shipment and administration processes. The commonly used and FDA approved excipients for IgG and Ig -based therapeutics may no longer fulfil the challenge of HCF development for these molecules to certain extent, especially for some complex Ig-based platforms. 2-Hydroxypropyl beta-cyclodextrin (HP-β-CD) is one of the promising excipients applied recently for HCF development of IgG and Ig-based therapeutics although it has been used for formulation of small synthesized chemical drugs for more than thirty years. This review describes essential aspects about application of HP-β-CD as excipient in pharmaceutical formulation, including physico-chemical properties of HP-β-CD, supply chain, regulatory, patent landscape, marketed drugs with HP-β-CD, analytics and analytical challenges, stability and control strategies, and safety concerns. It also provides an overview of different studies, and outcomes thereof, regarding formulation development for IgGs and Ig-based molecules in liquid and solid (lyophilized) dosage forms with HP-β-CD. The review specifically highlights the challenges for formulation manufacturing of IgG and Ig-based therapeutics with HP-β-CD and identifies areas for future work in pharmaceutical and formulation development.

Powder suspensions in non-aqueous vehicles for delivery of therapeutic proteins

Formulating biopharmaceuticals is a challenging task due to their complex and sensitive nature. Protein drugs are typically marketed either as an aqueous solution or as a lyophilizate. Usually aqueous solutions are preferred as neither drying nor reconstitution are required. But it may be unfeasible if the protein features low stability. An interesting alternative to avoid at least reconstitution are protein powder suspensions in non-aqueous vehicles. Such formulations combine the ready-to-use approach with the high protein stability in the solid state. Additionally, protein powder suspensions offer a potentially lower viscosity compared to aqueous solutions at high protein concentrations. Besides injection, other application routes might also benefit from the protein powder approach such as topical or inhalational delivery. Protein powders, which can be dispersed in the non-aqueous suspension vehicle, are usually prepared by spray-drying or freeze-drying with an additional milling step, but other techniques have also been described in literature. An ideal powder preparation technique results in minimum protein damage and yields particle sizes in the lower micrometre range and homogeneous particle size distribution enabling subcutaneous or intramuscular injection through hypodermic needles. As suspension vehicles traditional non-aqueous injectable liquids, such as plant oils, may be selected. But they show an inherent high viscosity, which can lead to unacceptable glide forces during injection. Furthermore, the vehicle should provide high product stability with respect to protein integrity and suspension resuspendability. This review will describe how proteins can be formulated as protein powder suspensions in non-aqueous vehicles for subcutaneous injection including potential vehicles, protein powder preparation techniques, protein and suspension physical stability, as well as the use in the field of high concentration protein formulations.

Effects of Hydrophobic Tail Length Variation on Surfactant-Mediated Protein Stabilization

Recently, protein therapeutics have gained significant attention as a result of their enhanced selectivity and diminished side effects compared to traditional small-molecule drugs. Despite their advantages, protein formulations typically suffer from stability issues because of aggregation and denaturation during production and storage, often resulting in detrimental immune responses. Surfactants can be used to stabilize and protect proteins in solution by preventing protein adsorption onto interfaces or by forming protective structures in solution. Herein, a detailed structure-activity relationship study is described, demonstrating the role that hydrophobic tail length plays in surfactant-mediated stabilization of the model therapeutic protein IgG. The FM1000 series, originating from a surfactant scaffold that allows for easy structure modulation, was synthesized by a simple 2-step procedure. First, phenylalanine was acylated with a variety of acyl chlorides of differing lengths to yield n-acyl phenylalanine, which was then coupled to Jeffamine M1000, a polyethylene glycol-based amine, to yield the final surfactant. With this FM1000 series, it was observed that the 14 carbon-long tail surfactant (14FM1000) was optimal at preventing IgG aggregation compared to surfactants with tails that were longer or shorter. Using a combination of dynamic surface tensiometry and quartz crystal microbalance with dissipation, it was hypothesized that 14FM1000 was able to prevent IgG adsorption, and therefore aggregation, by adsorbing appreciably onto surfaces quickly. 14FM1000 had the fastest rate of initial adsorption compared to the other surfactants studied. Short-tail surfactants were slow to and did not adsorb appreciably onto surfaces, allowing IgG adsorption. Although long-tail surfactants were also slow to adsorb, allowing IgG to adsorb and aggregate, their equilibrium adsorption was strong. Additionally, 14FM1000 was the most reversibly adsorbed surfactant, likely improving its ability to desorb and adsorb quickly to transient surfaces, therefore protecting the IgG at each new hydrophobic surface and preventing aggregation. By understanding the structure-activity relationship between surfactants and protein stabilization, we move toward more efficient design of future surfactants increasing the stability and utility of important protein therapeutics.

Competitive Surface Activity of Monoclonal Antibodies and Nonionic Surfactants at the Air-Water Interface Determined by Interfacial Rheology and Neutron Reflectometry

Interfacial stresses can destabilize therapeutic formulations containing monoclonal antibodies (mAbs), which is proposed to be a result of adsorption and aggregation at the air-water interface. To increase protein stability, pharmaceutical industries add surfactants, such as Polysorbate 20 (PS20), into protein formulations to minimize mAb adsorption at the interface but rarely quantify this process. We determine that mAb adsorption in surfactant-free solutions creates a monolayer with significant viscoelasticity, which can influence measurements of bulk mAb solution viscosity. In contrast, PS20 absorption leads to an interface with negligible interfacial viscosity that protects the air-water interface from mAb adsorption. These studies were performed through a combined study of surface tensiometry, interfacial rheology, capillary viscometry, and neutron reflectometry to determine the surface activity of a model surfactant, PS20, and mAb system, which can be useful for the successful formulation developments of biotherapeutics.

Armoring the Interface with Surfactants to Prevent the Adsorption of Monoclonal Antibodies

The pharmaceutical industry uses surface-active agents (excipients) in protein drug formulations to prevent the aggregation, denaturation, and unwanted immunological response of therapeutic drugs in solution as well as at the air/water interface. However, the mechanism of adsorption, desorption, and aggregation of proteins at the interface in the presence of excipients remains poorly understood. The objective of this work is to explore the molecular-scale competitive adsorption process between surfactant-based excipients and two monoclonal antibody (mAb) proteins, mAb-1 and mAb-2. We use pendant bubble tensiometry to measure the ensemble average adsorption dynamics of mAbs with and without the excipient. The surface tension measurements allow us to quantify the rate at which the molecules "race" to the interface in single-component and mixed systems. These results define the phase space, where coadsorption of both mAbs and excipients occurs onto the air/water interface. In parallel, we use X-ray reflectivity (XR) measurements to understand the molecular-scale dynamics of competitive adsorption, revealing the surface-adsorbed amounts of the antibody and excipient. XR has revealed that at a sufficiently high surface concentration of the excipient, mAb adsorption to the surface and subsurface domains was inhibited. In addition, despite the fact that both mAbs adsorb via a similar mechanistic pathway and with similar dynamics, a key finding is that the competition for the interface directly correlates with the surface activity of the two mAbs, resulting in a fivefold difference in the concentration of the excipient needed to displace the antibody.

Shocking Data on Parcel Shipments of Protein Solutions

An early-phase development shipping study was designed to interrogate the stability of liquid formulations under normal shipping conditions. Parcel shipments were made between Seattle, WA, and Indianapolis, IN, during 2018-2019. Each parcel contained a data recorder that tracked the shipment by GPS and measured shock and temperature. During the transport process, the parcels received up to 40 shock events with strengths ranging from 8 to 36G. After shipment, the formulations without polysorbate showed considerable increases in submicron and visible particles while little to no change occurred when polysorbate was present. Samples dropped repeatedly from a height of 18 inches to produce a shock of ∼25G caused visible particle formation with little increase in the subvisible particles, suggesting that other factors, such as vibration, in addition to the shock, were necessary to produce particle formation. These results provide a basis for further studies in the relationships between physical stability of mAbs and the challenges introduced by the shipment network, specifically shock and vibration. The findings indicate that the shock events as measured are repeatable and attributable to the layout of the sorting facility.

What Makes Polysorbate Functional? Impact of Polysorbate 80 Grade and Quality on IgG Stability During Mechanical Stress

Polysorbate 80 (PS80) is a commonly used surfactant in therapeutic protein formulations to mitigate adsorption and interface-induced protein aggregation. Several PS80 grades and qualities are available on the market for parenteral application. The role of PS80 grade on protein stability remains debatable, and the impact of (partially) degraded PS on protein aggregation is not yet well understood. In our study, a monoclonal antibody (IgG) was subjected to 3 different mechanical stress conditions in the presence of multicompendial (MC) and Chinese pharmacopeia (ChP) grade PS80. Furthermore, IgG formulations were spiked with (partly) hydrolyzed PS80 to investigate the effect of PS80 degradants on protein stability. PS80 functionality was assessed by measuring the extent of protein aggregation and particle formation induced during mechanical stress by using size-exclusion chromatography, dynamic light scattering, backgrounded membrane imaging, and flow imaging microscopy. No distinguishable differences in PS80 functionality between MC and ChP grade were observed in the 3 stress tests. However, with increasing degree of PS80 hydrolysis, higher counts of subvisible particles were measured after stress. Furthermore, higher levels of PS80 degradants at a constant PS80 concentration may destabilize the IgG. In conclusion, MC and ChP grade PS80 are equally protective, but PS80 degradants compromise IgG stability.

Protein stability in pulmonary drug delivery via nebulization

Protein inhalation is a delivery route which offers high potential for direct local lung application of proteins. Liquid formulations are usually available in early stages of biopharmaceutical development and nebulizers are the device of choice for atomization avoiding additional process steps like drying and enabling fast progression to clinical trials. While some proteins were proven to remain stable throughout aerosolization e.g. DNase, many biopharmaceuticals are more susceptible towards the stresses encountered during nebulization. The main reason for protein instability is unfolding and aggregation at the air-liquid interface, a problem which is of particular challenge in the case of ultrasound and jet nebulizers due to recirculation of much of the generated droplets. Surfactants are an important formulation component to protect the sensitive biomolecules. A second important challenge is warming of ultrasound and vibrating mesh devices, which can be overcome by overfilling, precooled solutions or cooling of the reservoir. Ultimately, formulation development has to go hand in hand with device evaluation.

Control of protein particle formation during ultrafiltration/diafiltration through interfacial protection

This study investigates the mechanism of protein particle formation during ultrafiltration/diafiltration (UF/DF), finding that agitation drives particle formation by promoting protein-interface adsorption and desorption. Low conductivity and the presence of surfactant reduced the level of particle formation in small-scale stirring studies, and the same trends were observed in pumping and UF/DF. Polysorbate 80 (PS80) and hydroxypropyl-β-cyclodextrin (HPβCD) reduced particle formation in UF/DF by factors of 15 and 4, respectively. Measurements of conformational stability, colloidal stability, and surface tension demonstrated that PS80 protects against particle formation by preventing protein-interface adsorption, low conductivity improves the colloidal stability of the protein, and the mechanism of action of HPβCD remains unclear. This work demonstrates that interfacial adsorption–desorption of the protein during UF/DF is the principal cause of particle formation, that the level of surfactant-free particle formation depends on the colloidal stability of the protein, and that the inclusion of surfactant greatly reduces in-process particle formation during UF/DF.

Renewal of the air-water interface as a critical system parameter of protein stability: aggregation of the human growth hormone and its prevention by surface-active compounds

Soluble proteins are often highly unstable under mixing conditions that involve dynamic contacting between the main liquid phase and a gas phase. The recombinant human growth hormone (rhGH) was recently shown to undergo aggregation into micrometer-sized solid particles composed of non-native (mis- or unfolded) protein, once its solutions were stirred or shaken to generate a continuously renewed air-water interface. To gain deepened understanding and improved quantification of the air-water interface effect on rhGH stability, we analyzed the protein's aggregation rate (r(agg)) at controlled specific air-water surface areas (a(G/L)) established by stirring or bubble aeration. We show that in spite of comparable time-averaged values for a(G/L) (≈ 100 m(2)/m(3)), aeration gave a 40-fold higher r(agg) than stirring. The enhanced r(agg) under aeration was ascribed to faster macroscopic regeneration of free a(G/L) during aeration as compared to stirring. We also show that r(agg) was independent of the rhGH concentration in the range 0.67 - 6.7 mg/mL, and that it increased linearly dependent on the available a(G/L). The nonionic surfactant Pluronic F-68, added in 1.6-fold molar excess over rhGH present, resulted in complete suppression of r(agg). Foam formation was not a factor influencing r(agg). Using analysis by circular dichroism spectroscopy and small-angle X-ray scattering, we show that in the presence of Pluronic F-68 under both stirring and aeration, the soluble protein retained its original fold, featuring native-like relative composition of secondary structural elements. We further provide evidence that the efficacy of Pluronic F-68 resulted from direct, probably hydrophobic protein-surfactant interactions that prevented rhGH from becoming attached to the air-water interface. Surface-induced aggregation of rhGH is suggested to involve desorption of non-native protein from the air-water interface as the key limiting step. Proteins or protein aggregates released back into the bulk liquid appear to be essentially insoluble.

The effects of excipients on protein aggregation during agitation: an interfacial shear rheology study

We investigated the effects of excipients in solutions of keratinocyte growth factor 2 (KGF-2) on protein aggregation during agitation as well as on interfacial shear rheology at the air-water interface. Samples were incubated with or without agitation, and in the presence or absence of the excipients heparin, sucrose, or polysorbate 80 (PS80). The effect of excipients on the extent of protein aggregation was determined by UV-visible spectroscopy and micro-flow imaging. Interfacial shear rheology was used to detect the gelation time and strength of protein gels at the air-water interface. During incubation, protein particles of size ≥1 μm and insoluble aggregates formed faster for KGF-2 solutions subjected to agitation. Addition of either heparin or sucrose promoted protein aggregation during agitation. In contrast, PS80 substantially inhibited agitation-induced KGF-2 aggregation but facilitated protein particulate formation in quiescent solutions. The combination of PS80 and heparin or sucrose completely prevented protein aggregation during both nonagitated and agitated incubations. Interfacial rheological measurements showed that KGF-2 in buffer alone formed an interfacial gel within a few minutes. In the presence of heparin, KGF-2 interfacial gels formed too quickly for gelation time to be determined. KGF-2 formed gels in about 10 min in the presence of sucrose. The presence of PS80 in the formulation inhibited gelation of KGF-2. Furthermore, the interfacial gels formed by the protein in the absence of PS80 were reversible when PS80 was added to the samples after gelation. Therefore, there is a correspondence between formulations that exhibited interfacial gelation and formulations that exhibited agitation-induced aggregation.