Understanding the Role of Preferential Exclusion of Sugars and Polyols from Native State IgG1 Monoclonal Antibodies and its Effect on Aggregation and Reversible Self-Association

Stabilizing effect of HP-β-CD on infliximab in liquid formulations and a solid formulation produced by electrospinning

The development of stable biopharmaceutical formulations, such as monoclonal antibodies, poses a great challenge in the pharmaceutical industry. This study investigated the stabilizing effect of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) in liquid and solid formulations of infliximab during processing and storage. The solid formulation was produced by a scaled-up high-speed electrospinning method, resulting in a product suitable for reconstitution with excellent dissolution properties. Liquid formulations contained exclusively HP-β-CD as a stabilizing excipient at different concentrations. Both types of formulations were stored under various conditions for up to 6 months, and infliximab stability was compared based on monomer recovery and the analysis of fragments and aggregates. The solid formulation stored at low (-18 °C, 4 °C) temperatures and lower humidity conditions show the most promising results. Moreover, the monomer loss was less than 10 % even at room temperature storage after 2 months, indicating a potentially good temperature tolerance. Increasing HP-β-CD content in liquid formulations significantly improved the long-term stability of infliximab while enhancing protection against mechanical stress. Furthermore, to better understand the stabilizing mechanism of HP-β-CD on infliximab, the molecular interactions were investigated by bio-layer interferometry and isothermal titration calorimetry methods. The experiments proved that the presence of HP-β-CD decreased infliximab self-interaction, correlating with the aggregation-suppressing effect of HP-β-CD observed during the stress- and long-term stability studies. The results demonstrate the potential of HP-β-CD as a stabilizing excipient in liquid and solid formulations of infliximab.

Strategy to mitigate aggregation during Protein A chromatography and low pH virus inactivation for a nivolumab biosimilar candidate

Protein A chromatography represents the most prevalent methodology for the capture of monoclonal antibodies. The use of a low pH elution buffer from Protein A has been observed to contribute to product aggregation, particularly in the case of IgG4 antibodies, such as nivolumab. This paper presents a well-defined strategy for addressing this issue. Initial experiments were conducted at scale-down Protein A affinity chromatography to evaluate the use of glycine-HCL and sodium citrate as elution buffers at pH values of 3.25, 3.5, and 3.75. Subsequently, a scale-down screening was conducted to assess the efficacy of various additives in Protein A elution. These included 10 % (w/v) mannitol, 50 mM histidine, 50 mM sucrose, 10 % (v/v) sorbitol, 50 mM arginine, 50 mM trehalose, 0.02 % (v/v) polysorbate 80, 1.5 M urea, and 1 M MgCl2. The three most stabilizing additives were evaluated at the laboratory scale, and the one that demonstrated the greatest ability to maintain the minimum high molecular weight aggregate over time was selected. Lastly, the selected additive was subjected to testing at elevated IgG concentrations during purification. Nivolumab exhibits a markedly pH-dependent propensity for aggregation, and the relative efficacy of glycine-HCL and sodium citrate in mitigating anti-PD1 aggregation within the pH range of 3.25 to 3.75 is subject to variation. The use of buffer 100 mM sodium citrate, pH 3.5 was found to be beneficial. All additives evaluated contribute to reducing nivolumab aggregation, albeit in different ways and to varying degrees of effectiveness. Elution buffer with mannitol, polysorbate 80, or MgCl₂ resulted in a monomer control ratio of approximately twice that observed in the absence of additives. However, the stabilizing role of mannitol was confirmed to be particularly significant, as the ratio of aggregation formed at a low pH was reduced to ≤ 2 % from 15 % in all evaluated scales and at different protein concentrations, while maintaining high biological activity.

The role of histidine buffer in the iron-catalyzed formation of oxidizing species in pharmaceutical formulations: Mechanistic studies

Iron-catalyzed oxidation reactions are common degradation pathways in pharmaceutical formulations. Buffers can influence oxidation reactions promoted by iron (Fe) and hydrogen peroxide (H₂O₂). However, mechanistically, the specific role of buffers in such reactions is not well understood. Here, we investigate the formation of radical intermediates using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a probe. Interestingly, over the time course of our experiments histidine (His) is the only buffer that promotes significant radical production during Fe(III)-catalyzed decomposition of H₂O₂, in contrast to other common pharmaceutical buffers such as citrate, succinate, adipate, and 2-(N-morpholino)ethanesulfonic acid (MES). The critical role of His in these degradation reactions is attributed to its unique, higher affinity for Fe(II) as compared to Fe(III), facilitating the reduction of Fe(III) to Fe(II) and subsequent Fenton and/or Fenton-like reactions with H₂O₂.

Higher concentration of trehalose dihydrate stabilizes recombinant IgG1 under forced stress conditions

Stability of complex biotherapeutics like monoclonal antibodies is paramount for their safe and efficacious use. Excipients are inactive ingredients that are added to the purified product so as to offer it a stable environment. Trehalose dihydrate is a non-reducing sugar that is commonly used as a stabilizing agent in biotherapeutic formulations under liquid and frozen states. The stabilizing effect of trehalose against aggregation in protein formulations is well known. The present study aims to offer insights into the stability effects of higher trehalose concentration (230 mM) on liquid trastuzumab under different forced stress conditions including thermal, light with and without hydrogen peroxide (H2O2), humidity and extraction stresses. Under thermal stress, while high molecular weight (HMW) accounted for 38.80 % in the trastuzumab sample without trehalose, it was 4.89 % at high trehalose concentration. Similarly, under light stress with H2O2, the trastuzumab sample without trehalose had >80 % more HMW than at high trehalose concentration. Two other IgG1 mAbs (rituximab and bevacizumab) were also evaluated for stability at higher trehalose concentrations (230 mM). Similar to trastuzumab, stabilization was observed under thermal stress for rituximab and bevacizumab at higher trehalose concentration compared to samples without trehalose (21.90 % and 29.90 % HMW, respectively). Likewise, accelerated (under humidity stress) and extraction stress induced secondary and tertiary structure disruptions were reduced at higher trehalose concentration. An in-silico study between binding interactions of trehalose and trastuzumab Fab region at different concentrations depicted an increase in hydrogen bonding with trastuzumab Fab when the trehalose concentration is increased, thereby reducing aggregation. Overall, mAb stability under forced stress conditions improved significantly at higher trehalose concentrations. While higher trehalose concentration (>200 mM) is used in mAb formulations and is known to minimise aggregation under thermal stress, however, the current study aims to also explore the stability imparted under light (with H2O2), humidity and extraction stresses for three different mAbs and attempts to explain the underlying mechanisms via in-silico studies.

Rapid Development of High Concentration Protein Formulation Driven by High-Throughput Technologies

BACKGROUND

High concentration protein formulation (HCPF) development needs to balance protein stability attributes such as conformational/colloidal stability, chemical stability, and solution properties such as viscosity and osmolality.

METHODOLOGY

A three-phase design is established in this work. In Phase 1, conformational and colloidal stability are measured by 384-well-based high-throughput (HT) biophysical screening while viscosity reduction screening is performed with HT viscosity screening. Collectively, the biophysical and viscosity screening data are leveraged to design the phase 2 of short-term stability study, executed using 96-well plates under thermal and freeze/thaw stresses. In phase 2, samples are analyzed by stability-indicating assays and processed with pair-wise Student's t-test analyses to choose the final formulations. In phase 3, the final formulations are then confirmed through a one-month accelerated stability in glass vials.

RESULTS

Using a model antibody A (mAb-A), the initial HT screening successfully established the 384-well based platform. A lead formulation was chosen from the second round based on statistical analyses and subsequently tested against the commercial formulation of mAb-A as a control. Compared to the control, the lead formulation reduced the viscosity of mAb-A by 30% and decreased subvisible particles after thermal stress by 80%.

CONCLUSIONS

HT biophysical screening in 384-well plates was demonstrated to effectively guide the rational design of a high-throughput stability screening study using 96-well plates. This platform enables the identification of a high concentration formulation within seven weeks within the first two phases of study that strategically balance stability with solution properties, thus achieving a rapid development of HCPF.

Osmolytes as structure-function regulators of intrinsically disordered casein proteins

Intrinsically disordered proteins (IDPs), despite lacking a stable structure, play crucial role in majority of the cellular processes. Casein, a key milk protein, represents this category of proteins, due to its dynamic and flexible structure which contributes towards the nutritional and functional properties of milk. The present chapter summarizes the role of osmolytes (small molecular weight organic molecules generally accumulated by cells to protect against denaturing stresses) in regulating the structure-function integrity of intrinsically disordered casein proteins. Osmolyte - casein interplay is of particular interest as these osmolytes have been found to affect the conformational flexibility and functional properties of casein proteins and thus can affect their overall behavior in the cellular environment. The present chapter delves into this by discussing the unique structural and functional properties of casein IDPs and the influence of osmolytes on their structure, stability, and chaperone activity. Elucidation of the osmolyte effects on the structural-functional integrity of caseins should advance our understanding of the dynamics of protein structure and function in complex biological environments and also offer practical perceptions for their future applications.

Investigation on environmental factors contributing to bispecific antibody stability and the reversal of self-associated aggregates

Bispecific antibodies (bsAbs) hold promises for enhanced therapeutic potential surpassing that of their parental monoclonal antibodies. However, bsAbs pose great challenges in their manufacturing, and one of the common reasons is their susceptibility to aggregation. Building on previous studies demonstrating the functionality and potential manufacturability of Fab-scFv format bsAb, this investigation delved into the impact of environmental factors-such as pH, buffer types, ionic strength, protein concentrations, and temperatures-on its stability and the reversal of its self-associated aggregates. Mildly acidic, low-salt conditions were found optimal, ensuring bsAb stability for 30 days even at elevated temperature of 40 °C. Furthermore, these conditions facilitated the reversal of its self-associated aggregates to monomers during the initial 7-day incubation period. Our findings underscore the robustness and resilience of Fab-scFv format bsAb, further confirming its potential manufacturability despite its current absence as commercial products.

A Structural Study on Absorption of Lysozyme in Amorphous Starch Microspheres

The potential of using proteins as drugs is held back by their low stability in the human body and challenge of delivering them to the site of function. Extensive research is focused on drug delivery systems that can protect, carry, and release proteins in a controlled manner. Of high potential are cross-linked degradable starch microspheres (DSMs), as production of these is low-cost and environmentally friendly, and the products are degradable by the human body. Here, we demonstrate that DSMs can absorb the model protein lysozyme from an aqueous solution. At low amounts of lysozyme, its concentration in starch microspheres strongly exceeds the bulk concentration in water. However, at higher protein contents, the difference between concentrations in the two phases becomes small. This indicates that, at lower lysozyme contents, the absorption is driven by protein-starch interactions, which are counteracted by protein-protein electrostatic repulsion at high concentrations. By applying small-angle X-ray scattering (SAXS) to the DSM-lysozyme system, we show that lysozyme molecules are largely unaltered by the absorption in DSM. In the same process, the starch network is slightly perturbed, as demonstrated by a decrease in the characteristic chain to chain distance. The SAXS data modeling suggests an uneven distribution of the protein within the DSM particles, which can be dependent on the internal DSM structure and on the physical interactions between the components. The results presented here show that lysozyme can be incorporated into degradable starch microspheres without any dependence on electrostatic or specific interactions, suggesting that similar absorption would be possible for pharmaceutical proteins.

Stability of Protein Pharmaceuticals: Recent Advances

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

A Review of Recent FDA-Approved Biologic-Device Combination Products

With the remarkably strong growth of the biopharmaceutical market, an increasing demand for self-administration and rising competitions attract substantial interest to the biologic-device combination products. The ease-of-use of biologic-device combination products can minimize dosing error, improve patient compliance and add value to the life-cycle management of biological products. As listed in the purple book issued by the U.S. Food and Drug Administration (FDA), a total of 98 brand biologic-device combination products have been approved with Biologic License Application from January 2000 to August 2023, where this review mainly focused on 63 products containing neither insulin nor vaccine. Prefilled syringes (PFS) and autoinjectors are the most widely adopted devices, whereas innovative modifications like needle safety guard and dual-chamber design and novel devices like on-body injector also emerged as promising presentations. All 16 insulin products employ pen injectors, while all 19 vaccine products are delivered by a PFS. This review provides a systematic summary of FDA-approved biologic-device combination products regarding their device configurations, routes of administration, formulations, instructions for use, etc. In addition, challenges and opportunities associated with biologic-device compatibility, regulatory complexity, and smart connected devices are also discussed. It is believed that evolving technologies will definitely move the boundaries of biologic-device combination product development even further.

The Development of a Novel Aflibercept Formulation for Ocular Delivery

Aflibercept is a recombinant fusion protein that is commercially available for several ocular diseases impacting millions of people worldwide. Here, we use a case study approach to examine alternative liquid formulations for aflibercept for ocular delivery, utilizing different stabilizers, buffering agents, and surfactants with the goal of improving the thermostability to allow for limited storage outside the cold chain. The formulations were developed by studying the effects of pH changes, substituting amino acids for sucrose and salt, and using polysorbate 80 or poloxamer 188 instead of polysorbate 20. A formulation containing acetate, proline, and poloxamer 188 had lower rates of aggregate formation at 4, 30, and 40°C when compared to the marketed commercial formulation containing phosphate, sucrose, sodium chloride, and polysorbate 20. Further studies examining subvisible particles after exposure to a transport stress and long-term stability at 4°C, post-translational modifications by multi-attribute method, purity by reduced and non-reduced capillary electrophoresis, and potency by cell proliferation also demonstrated a comparable or improved stability for the enhanced formulation of acetate, proline, and poloxamer 188. This enhanced stability could enable limited storage outside of the cold chain, allowing for easier distribution in low to middle income countries.

The Effects of Excipients on Freeze-dried Monoclonal Antibody Formulation Degradation and Sub-Visible Particle Formation during Shaking

PURPOSES

We previously reported an unexpected phenomenon that shaking stress could cause more protein degradation in freeze-dried monoclonal antibody (mAb) formulations than liquid ones (J Pharm Sci, 2022, 2134). The main purposes of the present study were to investigate the effects of shaking stress on protein degradation and sub-visible particle (SbVP) formation in freeze-dried mAb formulations, and to analyze the factors influencing protein degradation during production and transportation.

METHODS

The aggregation behavior of mAb-X formulations during production and transportation was simulated by shaking at a rate of 300 rpm at 25°C for 24 h. The contents of particles and monomers were analyzed by micro-flow imaging, dynamic light scattering, size exclusion chromatography, and ultraviolet - visible (UV-Vis) spectroscopy to compare the protective effects of excipients on the aggregation of mAb-X.

RESULTS

Shaking stress could cause protein degradation in freeze-dried mAb-X formulations, while surfactant, appropriate pH, polyol mannitol, and high protein concentration could impact SbVP generation. Water content had little effect on freeze-dried protein degradation during shaking, as far as the water content was controlled in the acceptable range as recommended by mainstream pharmacopoeias (i.e., less than 3%).

CONCLUSIONS

Shaking stress can reduce the physical stability of freeze-dried mAb formulations, and the addition of surfactants, polyol mannitol, and a high protein concentration have protective effects against the degradation of model mAb formulations induced by shaking stress. The experimental results provide new insight for the development of freeze-dried mAb formulations.

Stabilization effects of saccharides in protein formulations: A review of sucrose, trehalose, cyclodextrins and dextrans

Saccharides are a popular group of stabilizers in liquid, frozen and freeze dried protein formulations. The current work reviewed the stabilization mechanisms of three groups of saccharides: (i) Disaccharides, specifically sucrose and trehalose; (ii) cyclodextrins (CDs), a class of cyclic oligosaccharides; and (iii) dextrans, a class of polysaccharides. Compared to sucrose, trehalose exhibits a more pronounced preferential exclusion effect in liquid protein formulations, due to its stronger interaction with water molecules. However, trehalose obtains higher phase separation and crystallization propensity in frozen solutions, resulting in the loss of its stabilization function. In lyophilized formulations, sucrose has a higher crystallization propensity. Besides, its glass matrix is less homogeneous than that of trehalose, thus undermining its lyoprotectant function. Nevertheless, the hygroscopic nature of trehalose may result in high water absorption upon storage. Among all the CDs, the β form is believed to have stronger interactions with proteins than the α- and γ-CDs. However, the stabilization effect, brought about by CD-protein interactions, is case-by-case - in some examples, such interactions can promote protein destabilization. The stabilization effect of hydroxypropyl-β-cyclodextrin (HPβCD) has been extensively studied. Due to its amphiphilic nature, it can act as a surface-active agent in preventing interfacial stresses. Besides, it is a dual functional excipient in freeze dried formulations, acting as an amorphous bulking agent and lyoprotectant. Finally, dextrans, when combined with sucrose or trehalose, can be used to produce stable freeze dried protein formulations. A strong stabilization effect can be realized by low molecular weight dextrans. However, the terminal glucose in dextrans yields protein glycation, which warrants extra caution during formulation development.

Understanding and controlling the molecular mechanisms of protein aggregation in mAb therapeutics

In antibody development and manufacturing, protein aggregation is a common challenge that can lead to serious efficacy and safety issues. To mitigate this problem, it is important to investigate its molecular origins. This review discusses (1) our current molecular understanding and theoretical models of antibody aggregation, (2) how various stress conditions related to antibody upstream and downstream bioprocesses can trigger aggregation, and (3) current mitigation strategies employed towards inhibiting aggregation. We discuss the relevance of the aggregation phenomenon in the context of novel antibody modalities and highlight how in silico approaches can be exploited to mitigate it.

Photo-induced site-specific oxidative fragmentation of IgG1 mediated by iron(III)-containing histidine buffer: Mechanistic studies and excipient effects

Fragmentation may compromise the clinical efficacy and safety profile of monoclonal antibodies (mAbs). We recently reported that Fe(III)-containing histidine (His) buffer mediates site-specific mAb fragmentation within the Fc domain when exposed to visible light (Y. Zhang and C. Schöneich, Mol. Pharm. 2023, 20, 650-662). Here, we show that this fragmentation proceeds even more efficiently under near-UV light. Several formulation strategies were applied in an attempt to reduce the photo-induced fragmentation. In solution formulations, the fragmentation can be mitigated by reducing the concentration of His buffer, adding Fe(III)-chelating agents, and replacing His with other amino acids. Fragmentation can be almost completely inhibited by formulating the protein in the lyophilized state. Mechanistically, His plays a critical role in the fragmentation process, likely due to its affinity for Fe(II), driving a photo-redox reaction towards product formation.

Stability of Monoclonal Antibodies as Solid Formulation for Auto-Injectors: A Pilot Study

Drug adherence is a significant medical issue, often responsible for sub-optimal outcomes during the treatment of chronic diseases such as rheumatoid or psoriatic arthritis. Monoclonal antibodies (which are exclusively given parenterally) have been proven to be an effective treatment in these cases. The use of auto-injectors is an effective strategy to improve drug adherence in parenteral treatments since these pen-like devices offer less discomfort and increased user-friendliness over conventional syringe-based delivery. This study aims to investigate the feasibility of including a monoclonal antibody as a solid formulation inside an auto-injector pen. Specifically, the objective was to evaluate the drug stability after a concentration (to reduce the amount of solvent and space needed) and freeze-drying procedure. A preliminary screening of excipients to improve stability was also performed. The nano-DSC results showed that mannitol improved the stability of the concentrated, freeze-dried antibody in comparison to its counterpart without it. However, a small instability of the CH2 domain was still found for mannitol samples, which will warrant further investigation. The present results serve as a stepping stone towards advancing future drug delivery systems that will ultimately improve the patient experience and associated drug adherence.

Chemometrics in Protein Formulation: Stability Governed by Repulsion and Protein Unfolding

Therapeutic proteins can be challenging to develop due to their complexity and the requirement of an acceptable formulation to ensure patient safety and efficacy. To date, there is no universal formulation development strategy that can identify optimal formulation conditions for all types of proteins in a fast and reliable manner. In this work, high-throughput characterization, employing a toolbox of five techniques, was performed on 14 structurally different proteins formulated in 6 different buffer conditions and in the presence of 4 different excipients. Multivariate data analysis and chemometrics were used to analyze the data in an unbiased way. First, observed changes in stability were primarily determined by the individual protein. Second, pH and ionic strength are the two most important factors determining the physical stability of proteins, where there exists a significant statistical interaction between protein and pH/ionic strength. Additionally, we developed prediction methods by partial least-squares regression. Colloidal stability indicators are important for prediction of real-time stability, while conformational stability indicators are important for prediction of stability under accelerated stress conditions at 40 °C. In order to predict real-time storage stability, protein-protein repulsion and the initial monomer fraction are the most important properties to monitor.

Optimizing a therapeutic humanized follicle-stimulating hormone-blocking antibody formulation by protein thermal shift assay

Biopharmaceutical products are formulated using several Food and Drug Administration (FDA) approved excipients within the inactive ingredient limit to maintain their storage stability and shelf life. Here, we have screened and optimized different sets of excipient combinations to yield a thermally stable formulation for the humanized follicle-stimulating hormone (FSH)-blocking antibody, MS-Hu6. We used a protein thermal shift assay in which rising temperatures resulted in the maximal unfolding of the protein at the melting temperature (Tm ). To determine the buffer and pH for a stable solution, four different buffers with a pH range from 3 to 8 were screened. This resulted in maximal Tm s at pH 5.62 for Fab in phosphate buffer and at pH 6.85 for Fc in histidine buffer. Upon testing a range of salt concentrations, MS-Hu6 was found to be more stable at lower concentrations, likely due to reduced hydrophobic effects. Molecular dynamics simulations revealed a higher root-mean-square deviation with 1 mM than with 100 mM salt, indicating enhanced stability, as noted experimentally. Among the stabilizers tested, Tween 20 was found to yield the highest Tm and reversed the salt effect. Among several polyols/sugars, trehalose and sucrose were found to produce higher thermal stabilities. Finally, binding of recombinant human FSH to MS-Hu6 in a final formulation (20 mM phosphate buffer, 1 mM NaCl, 0.001% w/v Tween 20, and 260 mM trehalose) resulted in a thermal shift (increase in Tm ) for the Fab, but expectedly not in the Fc domain. Given that we used a low dose of MS-Hu6 (1 μM), the next challenge would be to determine whether 100-fold higher, industry-standard concentrations are equally stable.

Two peak elution behavior of a monoclonal antibody in cation exchange chromatography as a screening tool for excipients

Aggregation of proteins is a critical quality attribute and a major concern during the purification of therapeutic proteins, like monoclonal antibodies. In-solution experiments applying different stress scenarios, e.g., mechanical, or physical stresses, can determine the overall conformational stability of the protein to enhance drug product shelf-life. Several groups have reported surface-induced unfolding and aggregation of monoclonal antibodies and their derivatives during cation exchange chromatography, which results in a two-peak elution behavior of the protein and its species. We have investigated universal influencing factors, like temperature and hold time, on this phenomenon. The formation of the second peak is a kinetic process, which is strongly influenced by temperature during the hold time. However, our main focus was the application of excipients and their influence on the two-peak elution behavior. We compared the on-column screening results with results obtained through a "traditional" in-solution screening using nanoDSF. Mostly, stabilizing excipients, like Sucrose, show their stabilizing abilities in both systems, but some discrepancies, e.g., using Arginine, between the two orthogonal techniques show the potential of the on-column screening system to lead to unexpected results, which would not necessarily be visible in in-solution experiments.

Polyols, increasing global stability of cytochrome c, destabilize the thermal unfolding intermediate

Studies on the intermediate states of proteins provide essential information on folding pathway and energy landscape of proteins. Osmolytes, known to alter the stability of proteins, might also affect the structure and energy states of folding intermediates. This was examined using cytochrome c (Cyt) as a model protein which forms a spectroscopically detectable intermediate during thermal denaturation transition. Most of the secondary structure and the native heme-ligation were intact in the intermediate state of the protein. Denaturants, urea and guanidinium hydrochloride, and ionic salt destabilizes the intermediate and drive the protein to follow two-state transition. The effect of polyol class of osmolytes, glycol, glycerol, erythritol, xylitol and sorbitol (with OH-groups two to six), on the intermediate was studied using Soret absorbance and far-UV circular dichroism. With the increasing concentration of any of the polyols, the transition-midpoint temperature (T_m) and the enthalpy change (ΔH) for native to intermediate transition were decreased. This indicated that the intermediate was destabilized by the polyols. However, the polyols increased the overall stability of the protein by increasing T_m and ΔH for intermediate to unfolded transition, except for glycol which destabilized the protein. These results show that the polyols could alter the energy state of the intermediate, and the effect of lower and higher polyols might be different on the stability and folding pathway of the protein.Communicated by Ramaswamy H. Sarma.

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.

Investigating protein-excipient interactions of a multivalent VHH therapeutic protein using NMR spectroscopy

Multispecific therapeutic proteins come in a variety of formats, including bi- and tri-specific antibodies, dual-variable domain antibodies, and CrossMabs. These multivalent proteins are engineered to interact with multiple therapeutic target proteins with high specificity. Multi-domain proteins can be created by linking together a variety of high-affinity antibody fragments. The choice of protein domains and linkers not only affects the interactions of these molecules with therapeutic targets but also influences the intrinsic behavior in solution that affects their stability. The complexity of solution interactions may translate into developability and manufacturing challenges. Here, we use nuclear magnetic resonance (NMR) spectroscopy to study the solution behavior of a multivalent V_HH molecule composed of three flexibly linked heavy-chain-only domains that show dramatic stabilization against thermal degradation in the presence of sucrose. A collection of NMR fingerprinting and profiling methods were used to simultaneously monitor the protein solution behavior and capture details of protein–excipient interactions. We provide a framework to characterize and begin to understand the role of molecular flexibility in protein stabilization with potential applications in the design of novel therapeutic protein scaffolds that include multivalent proteins, fusion proteins, antibody-drug conjugates, and proteins modified with flexible lipids.

Molecular computations of preferential interactions of proline, arginine.HCl, and NaCl with IgG1 antibodies and their impact on aggregation and viscosity

Preferential interactions of excipients with the antibody surface govern their effect on the stability of antibodies in solution. We probed the preferential interactions of proline, arginine.HCl (Arg.HCl), and NaCl with three therapeutically relevant IgG1 antibodies via experiment and simulation. With simulations, we examined how excipients interacted with different types of surface patches in the variable region (Fv). For example, proline interacted most strongly with aromatic surfaces, Arg.HCl was included near negative residues, and NaCl was excluded from negative residues and certain hydrophobic regions. The differences in interaction of different excipients with the same surface patch on an antibody may be responsible for variations in the antibody's aggregation, viscosity, and self-association behaviors in each excipient. Proline reduced self-association for all three antibodies and reduced aggregation for the antibody with an association-limited aggregation mechanism. The effects of Arg.HCl and NaCl on aggregation and viscosity were highly dependent on the surface charge distribution and the extent of exclusion from highly hydrophobic patches. At pH 5.5, both tended to increase the aggregation of an antibody with a strongly positive charge on the Fv, while only NaCl reduced the aggregation of the antibody with a large negative charge patch on the Fv. Arg.HCl reduced the viscosities of antibodies with either a hydrophobicity-driven mechanism or a charge-driven mechanism. Analysis of this data presents a framework for understanding how amino acid and ionic excipients interact with different protein surfaces, and how these interactions translate to the observed stability behavior.

Pharmaceutical Excipients Enhance Iron-Dependent Photo-Degradation in Pharmaceutical Buffers by near UV and Visible Light: Tyrosine Modification by Reactions of the Antioxidant Methionine in Citrate Buffer

PURPOSE

To evaluate the effect of excipients, including sugars and amino acids, on photo-degradation reactions in pharmaceutical buffers induced by near UV and visible light.

METHODS

Solutions of citrate or acetate buffers, containing 1 or 50 μM Fe³⁺, the model peptides methionine enkephalin (MEn), leucine enkephalin (LEn) or proctolin peptide (ProP), in the presence of commonly used amino acids or sugars, were photo-irradiated with near UV or visible light. The oxidation products were analyzed by reverse-phase HPLC and HPLC-MS/MS.

RESULTS

The sugars mannitol, sucrose and trehalose, and the amino acids Arg, Lys, and His significantly promote the oxidation of peptide Met to peptide Met sulfoxide. These excipients do not increase the yields of hydrogen peroxide, suggesting that other oxidants such as peroxyl radicals are responsible for the oxidation of peptide Met. The addition of free Met reduces the oxidation of peptide Met, but, in citrate buffer, causes the addition of Met oxidation products to Tyr residues of the target peptides.

CONCLUSIONS

Commonly used excipients enhance the light-induced oxidation of amino acids in model peptides.

A review of Formulations of Commercially Available Antibodies

This review identified 126 commercially available antibodies approved globally between 1986 and February 2021 including 10 antibody drug conjugates, 16 biosimilars, and 3 antibody fragments. Prior to 2014 there were ≤ 5 approved each year, but after 2014 there have been ≥ 7 approved each year with the years 2017, 2019 and 2020 having the most at 17 each. A total of 136 products were identified of which 36 are lyophilized powders and 100 are solutions. The routes of administration are mainly subcutaneous or intravenous infusion with three intravenous bolus, two intravitreal, and one intramuscular. The subcutaneous products are ready-to-use solutions or reconstituted lyophilized powders that do not require dilution while most intravenous products are concentrates that require dilution into saline or another intravenous fluid prior to infusion. Most are packaged in single-dose units and the exception of multi-use is Herceptin® and its biosimilars. The package configurations are vials, prefilled autoinjectors, or prefilled syringes. A typical antibody formulation contains an antibody, an excipient to adjust tonicity or osmolality for solutions or a lyoprotectant for lyophilized powders, a buffer, and a surfactant. The ionic tonicity-adjusting excipient is mainly sodium chloride and the non-ionic osmolality-adjusting excipients include sucrose, trehalose, mannitol, maltose, and sorbitol. The lyoprotectants are trehalose and sucrose. The pH range is 4.8-8.0 and the buffers or pH-modifying agents include histidine, citrate, succinate, acetate, phosphate, glutamate, adipic acid, aspartic acid, lactic acid, tromethamine, and 2-(N-morpholino)-ethanesulfonic acid. The surfactants include mostly polysorbate 20 or polysorbate 80, with four containing poloxamer 188, and one that does not contain a surfactant but contains PEG 3350. One product does not contain a buffer, and 12 do not contain a surfactant. The viscosity-lowering excipients are sodium chloride and the amino acids arginine, glycine, proline, and lysine. Arginine may also function to adjust ionic strength and minimize aggregation. Human serum albumin is used in 2 products for intravenous infusion. Other excipients include methionine as an anti-oxidant, and EDTA or DTPA as chelating agents. The maximum volume of subcutaneous injection is 15 mL administered over 3-5 minutes, but the typically volume is 0.5-2 mL. Five fixed-dose combinations have recently been approved and four contain hyaluronidase to assist the large volume subcutaneous injection of up to 15 mL, while one is a fixed-dose combination for intravenous with three antibodies. Prefilled autoinjectors and syringes are becoming more common and many come affixed with a needle of 27-gauge or 29-gauge, while a few have a 26-gauge or a 30-gauge needle. Recent advancements include hyaluronidase to assist the large subcutaneous injection volume of 5-15 mL, fixed-dose combinations, buffer-free formulation, and smaller subcutaneous injection volume (0.1 mL).

HDX and In Silico Docking Reveal that Excipients Stabilize G-CSF via a Combination of Preferential Exclusion and Specific Hotspot Interactions

Assuring the stability of therapeutic proteins is a major challenge in the biopharmaceutical industry, and a better molecular understanding of the mechanisms through which formulations influence their stability is an ongoing priority. While the preferential exclusion effects of excipients are well known, the additional presence and impact of specific protein-excipient interactions have proven to be more elusive to identify and characterize. We have taken a combined approach of in silico molecular docking and hydrogen deuterium exchange-mass spectrometry (HDX-MS) to characterize the interactions between granulocyte colony-stimulating factor (G-CSF), and some common excipients. These interactions were related to their influence on the thermal-melting temperatures (T_m) for the nonreversible unfolding of G-CSF in liquid formulations. The residue-level interaction sites predicted in silico correlated well with those identified experimentally and highlighted the potential impact of specific excipient interactions on the T_m of G-CSF.

Ectoine and Hydroxyectoine Stabilize Antibodies in Spray-Dried Formulations at Elevated Temperature and during a Freeze/Thaw Process

Maintenance of protein stability during manufacture, storage, and delivery is necessary for the successful development of a drug product. Herein, the utility of two compatible solutes-ectoine and hydroxyectoine-in stabilizing a model protein labeled Fab2 has been investigated. Specifically, the performance of ectoine and hydroxyectoine in stabilizing Fab2 in a spray-dried formulation at elevated temperature and after multiple freeze/thaw cycles has been compared with the performance of a formulation containing trehalose and a formulation containing no excipient as controls. In the solid state at 90 and 37 °C and in freeze concentrate systems, ectoine and hydroxyectoine suppress protein aggregation. Like trehalose, hydroxyectoine also limits N-terminal pyroglutamate formation in Fab2 in the solid state. The extent of protein stabilization is dependent on the excipient concentration in the formulation, but at a 1:1 excipient to protein mass ratio, hydroxyectoine is better than trehalose in stabilizing Fab2. The results presented here suggest that ectoine and hydroxyectoine are effective excipients for stabilizing therapeutic antibodies.

Mst1 promotes mitochondrial dysfunction and apoptosis in oxidative stress-induced rheumatoid arthritis synoviocytes

In this study, we investigated the role of macrophage stimulating 1 (Mst1) and the AMPK-Sirt1 signaling pathway in the oxidative stress-induced mitochondrial dysfunction and apoptosis seen in rheumatoid arthritis-related fibroblast-like synoviocytes (RA-FLSs). Mst1 mRNA and protein expression was significantly higher in hydrogen peroxide (H₂O₂)-treated RA-FLSs than untreated controls. H₂O₂ treatment induced the mitochondrial apoptotic pathway by activating caspase3/9 and Bax in the RA-FLSs. Moreover, H₂O₂ treatment significantly reduced mitochondrial membrane potential and mitochondrial state-3 and state-4 respiration, but increased reactive oxygen species (ROS). Mst1 silencing significantly reduced oxidative stress-induced mitochondrial dysfunction and apoptosis in RA-FLSs. Sirt1 expression was significantly reduced in the H₂O₂-treated RA-FLSs, but was higher in the H₂O₂-treated Mst1-silenced RA-FLSs. Pretreatment with selisistat (Sirt1-specific inhibitor) or compound C (AMPK antagonist) significantly reduced the viability and mitochondrial function in H₂O₂-treated Mst1-silenced RA-FLSs by inhibiting Sirt1 function or Sirt1 expression, respectively. These findings demonstrate that oxidative stress-related upregulation and activation of Mst1 promotes mitochondrial dysfunction and apoptosis in RA-FLSs by inhibiting the AMPK-Sirt1 signaling pathway. This suggests the Mst1-AMPK-Sirt1 axis is a potential target for RA therapy.

Spliced X-box binding protein 1 induces liver cancer cell death via activating the Mst1-JNK-mROS signalling pathway

Previous studies have found that the primary pathogenesis of liver cancer progression is linked to excessive cancer cell proliferation and rapid metastasis. Although therapeutic advances have been made for the treatment of liver cancer, the mechanism underlying the liver cancer progression has not been fully addressed. In the present study, we explored the role of spliced X-box binding protein 1 (XBP1) in regulating the viability and death of liver cancer cells in vitro. Our study demonstrated that XBP1 was upregulated in liver cancer cells when compared to the primary hepatocytes. Interestingly, the deletion of XBP1 could reduce the viability of liver cancer cells in vitro via inducing apoptotic response. Further, we found that XBP1 downregulation was also linked to proliferation arrest and migration inhibition. At the molecular levels, XBP1 inhibition is followed by activation of the Mst1 pathway which promoted the phosphorylation of c-Jun N-terminal kinase (JNK). Then, the active Mst1-JNK pathway mediated mitochondrial reactive oxygen species (mROS) overproduction and then excessive ROS induced cancer cell death. Therefore, our study demonstrated a novel role played by XBP1 in modulating the viability of liver cancer cells via the Mst1-JNK-mROS pathways.

Dynamin-related protein-1 promotes lung cancer A549 cells apoptosis through the F-actin/bax signaling pathway

Dynamin-related protein-1 (Drp1) has been found to be associated with cell death. The role of Drp1 in A549 cells death has not been explored. In this study, adenovirus-mediated Drp1 overexpression was used to investigate the influence of Drp1 on A549 cell viability with a focus on F-actin and Bax. Cell viability, protein expression, oxygen consumption, energy metabolism, and growth rate were measured through ELISA, qPCR, western blots and pathway analysis. Our results indicated that Drp1 overexpression promoted A549 cell death through apoptosis. Mechanistically, cytoskeletal F-actin was impaired and Bax expression was elevated in response to Drp1 overexpression. Besides, energy metabolism was reduced and oxygen consumption was interrupted. Therefore, our results demonstrated that A549 cell viability, apoptosis and growth were regulated by the Drp1/F-actin/Bax signaling pathways. These data explain a new role played by Drp1 in regulating cell viability and also provide a potential target to affect the progression of lung cancer through induction of cell death.

Molecular Computations of Preferential Interaction Coefficients of IgG1 Monoclonal Antibodies with Sorbitol, Sucrose, and Trehalose and the Impact of These Excipients on Aggregation and Viscosity

Preferential interactions of formulation excipients govern their overall interactions with protein molecules, and molecular dynamics simulations allow for the examination of the interactions at the molecular level. We used molecular dynamics simulations to examine the interactions of sorbitol, sucrose, and trehalose with three different IgG1 antibodies to gain insight into how these excipients impact aggregation and viscosity. We found that sucrose and trehalose reduce aggregation more than sorbitol because of their larger size and their stronger interactions with high-spatial aggregation propensity residues compared to sorbitol. Two of the antibodies had high viscosity in sodium acetate buffer, and for these, we found that sucrose and trehalose tended to have opposite effects on viscosity. The data presented here provide further insight into the mechanisms of interactions of these three carbohydrate excipients with the antibody surface and thus their impact on excipient stabilization of antibody formulations.