Glass particles as an adjuvant: a model for adverse immunogenicity of therapeutic proteins

Application of Formulation Principles to Stability Issues Encountered During Processing, Manufacturing, and Storage of Drug Substance and Drug Product Protein Therapeutics

The field of formulation and stabilization of protein therapeutics has become rather extensive. However, most of the focus has been on stabilization of the final drug product. Yet, proteins experience stress and degradation through the manufacturing process, starting with fermentaition. This review describes how formulation principles can be applied to stabilize biopharmaceutical proteins during bioprocessing and manufacturing, considering each unit operation involved in prepration of the drug substance. In addition, the impact of the container on stabilty is discussed as well.

Immunostimulant plant proteins: Potential candidates as vaccine adjuvants

The COVID-19 pandemic is shaking up global scientific structures toward addressing antibiotic resistance threats and indicates an urgent need to develop more cost-effective vaccines. Vaccine adjuvants play a crucial role in boosting immunogenicity and improving vaccine efficacy. The toxicity and adversity of most adjuvant formulations are the major human immunization problems, especially in routine pediatric and immunocompromised patients. The present review focused on preclinical studies of immunoadjuvant plant proteins in use with antiparasitic, antifungal, and antiviral vaccines. Moreover, this report outlines the current perspective of immunostimulant plant protein candidates that can be used by researchers in developing new generations of vaccine-adjuvants. Future clinical studies are required to substantiate the plant proteins' safety and applicability as a vaccine adjuvant in pharmaceutical manufacturing.

Particles in Biopharmaceutical Formulations, Part 2: An Update on Analytical Techniques and Applications for Therapeutic Proteins, Viruses, Vaccines and Cells

Particles in biopharmaceutical formulations remain a hot topic in drug product development. With new product classes emerging it is crucial to discriminate particulate active pharmaceutical ingredients from particulate impurities. Technical improvements, new analytical developments and emerging tools (e.g., machine learning tools) increase the amount of information generated for particles. For a proper interpretation and judgment of the generated data a thorough understanding of the measurement principle, suitable application fields and potential limitations and pitfalls is required. Our review provides a comprehensive overview of novel particle analysis techniques emerging in the last decade for particulate impurities in therapeutic protein formulations (protein-related, excipient-related and primary packaging material-related), as well as particulate biopharmaceutical formulations (virus particles, virus-like particles, lipid nanoparticles and cell-based medicinal products). In addition, we review the literature on applications, describe specific analytical approaches and illustrate advantages and drawbacks of currently available techniques for particulate biopharmaceutical formulations.

Subvisible Particles in Solutions of Remicade in Intravenous Saline Activate Immune System Pathways in In Vitro Human Cell Systems

Among patients that receive Remicade® therapy, more than 20% have adverse infusion related reactions and approximately 50% have immunogenic responses.^1-3 Upon characterization of initial Remicade®-IV solution we observed a high concentration of subvisible particles that could inadvertently be delivered to patients. This solution was processed through the IV infusion system, mimicking the typical clinical administration setup - either with or without an in-line filter connected to the IV line. The samples generated thereafter were tested using various in vitro assays for activation of the innate immune system via cytokine release in whole blood and in peripheral blood mononuclear cell (PBMC) cultures, and activation of the Toll like receptors (TLRs). Activation of the adaptive immune system was evaluated by monitoring upregulation of surface receptors on dendritic cells (DCs) and CD4+ T cell proliferation in response to IV solution of Remicade®. Our results indicate that subvisible particles in Remicade®-saline solution have a significant role in activation of the immune system but there are extrinsic factors potentially contributed by the in-line filters or other process parameters that also contribute to immune system activation.

The Impact of Product and Process Related Critical Quality Attributes on Immunogenicity and Adverse Immunological Effects of Biotherapeutics

The pharmaceutical industry has experienced great successes with protein therapeutics in the last two decades and with novel modalities, including cell therapies and gene therapies, more recently. Biotherapeutics are complex in structure and present challenges for discovery, development, regulatory, and life cycle management. Biotherapeutics can interact with the immune system that may lead to undesired immunological responses, including immunogenicity, hypersensitivity reactions (HSR), injection site reactions (ISR), and others. Many product and process related critical quality attributes (CQAs) have the potential to trigger or augment such immunological responses to the product. Tremendous efforts, both clinically and preclinically, have been invested to understand the impact of product and process related CQAs on adverse immunological effects. The information and knowledge are critical for the implementation of Quality by Design (QbD), which requires risk assessment and establishment of specifications and control strategies for CQAs. A quality target product profile (QTPP) that identifies the key CQAs through process development can help assign severity scores based on safety, immunogenicity, pharmacokinetics (PK) and pharmacodynamics (PD) of the molecule. Gaps and future directions related to biotherapeutics and emerging novel modalities are presented.

Shifting Paradigms Revisited: Biotechnology and the Pharmaceutical Sciences

In 2003, Crommelin et al. published an article titled: "Shifting paradigms: biopharmaceuticals versus low molecular weight drugs" (https://doi.org/10.1016/S0378-5173(03)00376-4). In the present commentary, 16 years later, we discuss pharmaceutically relevant aspects of the evolution of biologics since then. First, we discuss the increasing repertoire of biologics, in particular, the rapidly growing monoclonal antibody family and the advent of advanced therapy medicinal products. Next, we discuss trends in formulation and characterization as well as summarize our current insights into immunogenicity of biologics. We spend a separate section on new product(ion) paradigms for biologics, such as cell-free production systems, production of advanced therapy medicinal products, and downscaled production approaches. Furthermore, we share our views on issues related to reaching the patient, including routes and techniques of administration, alternative development models for affordable biologics, biosimilars, and handling of biologics. In the concluding section, we outline outstanding issues and make some suggestions for resolving those.

Separation, Characterization and Discriminant Analysis of Subvisible Particles in Biologics Formulations

Background:

The presence of subvisible particles (SVPs) in parenteral formulations of biologics is a major challenge in the development of therapeutic protein formulations. Distinction between proteinaceous and non-proteinaceous SVPs is vital in monitoring formulation stability.

Methods:

The current compendial method based on light obscuration (LO) has limitations in the analysis of translucent/low refractive index particles. A number of attempts have been made to develop an unambiguous method to characterize SVPs, albeit with limited success.

Results:

Herein, we describe a robust method that characterizes and distinguishes both potentially proteinaceous and non-proteinaceous SVPs in protein formulations using Microflow imaging (MFI) in conjunction with the MVAS software (MFI View Analysis Suite), developed by ProteinSimple. The method utilizes two Intensity parameters and a morphological filter that successfully distinguishes proteinaceous SVPs from non-proteinaceous SVPs and mixed aggregates.

Conclusion:

he MFI generated raw data of a protein sample is processed through Lumetics LINK software that applies an in-house developed filter to separate proteinaceous from the rest of the particulates.

Flow Microscopy Imaging Is Sensitive to Characteristics of Subvisible Particles in Peginesatide Formulations Associated With Severe Adverse Reactions

The presence of subvisible particles in formulations of therapeutic proteins is a risk factor for adverse immune responses. Although the immunogenic potential of particulate contaminants likely depends on particle structural characteristics (e.g., composition, size, and shape), exact structure-immunogenicity relationships are unknown. Images recorded by flow imaging microscopy reflect information about particle morphology, but flow microscopy is typically used to determine only particle size distributions, neglecting information on particle morphological features that may be immunologically relevant. We recently developed computational techniques that utilize the Kullback-Leibler divergence and multidimensional scaling to compare the morphological properties of particles in sets of flow microscopy images. In the current work, we combined these techniques with expectation maximization cluster analyses and used them to compare flow imaging microscopy data sets that had been collected by the U.S. Food and Drug Administration after severe adverse drug reactions (including 7 fatalities) were observed in patients who had been administered some lots of peginesatide formulations. Flow microscopy images of particle populations found in the peginesatide lots associated with severe adverse reactions in patients were readily distinguishable from images of particles in lots where severe adverse reactions did not occur.

Why the Immune System Should Be Concerned by Nanomaterials?

Particles possess huge specific surface area and therefore nanomaterials exhibit unique characteristics, such as special physical properties and chemical hyper-reactivity, which make them particularly attractive but also raise numerous questions concerning their safety. Interactions of nanomaterials with the immune system can potentially lead to immunosuppression, hypersensitivity (allergy), immunogenicity and autoimmunity, involving both innate and adaptive immune responses. Inherent physical and chemical NP characteristics may influence their immunotoxicity, i.e., the adverse effects that can result from exposure. This review will focus on the possible interaction of nanomaterials including protein aggregates with the innate immune system with specific emphasis on antigen-presenting cells, i.e., dendritic cells, macrophages and monocytes.

Variability in Flow-Imaging Microscopy Measurements and Considerations for Biopharmaceutical Development

Flow-imaging microscopy is widely used in the biopharmaceutical industry to characterize populations of subvisible (1-100 μm) particles due to high sensitivity and the ability to discriminate different particle morphologies. The present work provides a comprehensive assessment of the capabilities of flow-imaging microscopy by exploring the impacts of a variety of factors on the observed variability of these measurements. A novel graphical presentation is proposed to facilitate both determination of expected levels and detection of potential atypical results. Data collected across different products and container-closure systems illustrate that a substantial amount of historical experience is typically required to adequately define the expected levels of subvisible particles for any specific system. It is also shown, however, that an appropriate level of control can be demonstrated without the need to pool large numbers of containers or perform replicate measurements.

Understanding the immunogenicity and antigenicity of nanomaterials: Past, present and future

Nanoparticle immunogenicity and antigenicity have been under investigation for many years. During the past decade, significant progress has been made in understanding what makes a nanoparticle immunogenic, how immune cells respond to nanoparticles, what consequences of nanoparticle-specific antibody formation exist and how they challenge the application of nanoparticles for drug delivery. Moreover, it has been recognized that accidental contamination of therapeutic protein formulations with nanosized particulate materials may contribute to the immunogenicity of this type of biotechnology products. While the immunological properties of engineered nanomaterials and their application as vaccine carriers and adjuvants have been given substantial consideration in the current literature, little attention has been paid to nanoparticle immuno- and antigenicity. To fill in this gap, we herein provide an overview of this subject to highlight the current state of the field, review past and present research, and discuss future research directions.

Silicone Oil Microdroplets Can Induce Antibody Responses Against Recombinant Murine Growth Hormone in Mice

Therapeutic protein products can cause adverse immune responses in patients. The presence of subvisible particles is a potential contributing factor to the immunogenicity of parenterally administered therapeutic protein formulations. Silicone oil microdroplets, which derive from silicone oil used as a lubricating coating on barrels of prefilled glass syringes, are often found in formulations. In this study, we investigated the potential of silicone oil microdroplets to act as adjuvants to induce an immune response in mice against a recombinant murine protein. Antibody responses in mice to subcutaneous injections of formulations of recombinant murine growth hormone (rmGH) that contained silicone oil microdroplets were measured and compared to responses to oil-free rmGH formulations. When rmGH formulations containing silicone oil microdroplets were administered once every other week, anti-rmGH antibodies were not detected. In contrast, mice exhibited a small IgG1 response against rmGH when silicone oil-containing rmGH formulations were administered daily, and an anti-rmGH IgM response was observed at later time points. Our findings showed that silicone oil microdroplets can act as an adjuvant to promote a break in immunological tolerance and induce antibody responses against a recombinant self-protein.

Mouse Models for Assessing Protein Immunogenicity: Lessons and Challenges

The success of clinical and commercial therapeutic proteins is rapidly increasing, but their potential immunogenicity is an ongoing concern. Most of the studies that have been conducted over the past few years to examine the importance of various product-related attributes (in particular several types of aggregates and particles) and treatment regimen (such as dose, dosing schedule, and route of administration) in the development of unwanted immune responses have utilized one of a variety of mouse models. In this review, we discuss the utility and drawbacks of different mouse models that have been used for this purpose. Moreover, we summarize the lessons these models have taught us and some of the challenges they present. Finally, we provide recommendations for future research utilizing mouse models to improve our understanding of critical factors that may contribute to protein immunogenicity.

Evaluation of Microflow Digital Imaging Particle Analysis for Sub-Visible Particles Formulated with an Opaque Vaccine Adjuvant

Microflow digital imaging (MDI) has become a widely accepted method for assessing sub-visible particles in pharmaceutical formulations however, to date; no data have been presented on the utility of this methodology when formulations include opaque vaccine adjuvants. This study evaluates the ability of MDI to assess sub-visible particles under these conditions. A Fluid Imaging Technologies Inc. FlowCAM^® instrument was used to assess a number of sub-visible particle types in solution with increasing concentrations of AddaVax^™, a nanoscale squalene-based adjuvant. With the objective (10X) used and the limitations of the sensor resolution, the instrument was incapable of distinguishing between sub-visible particles and AddaVax^™ droplets at particle sizes less than 5 μm. The instrument was capable of imaging all particle types assessed (polystyrene beads, borosilicate glass, cellulose, polyethylene protein aggregate mimics, and lysozyme protein aggregates) at sizes greater than 5 μm in concentrations of AddaVax^™ up to 50% (vol:vol). Reduced edge gradients and a decrease in measured particle sizes were noted as adjuvant concentrations increased. No significant changes in particle counts were observed for polystyrene particle standards and lysozyme protein aggregates, however significant reductions in particle counts were observed for borosilicate (80% of original) and cellulose (92% of original) particles. This reduction in particle counts may be due to the opaque adjuvant masking translucent particles present in borosilicate and cellulose samples. Although the results suggest that the utility of MDI for assessing sub-visible particles in high concentrations of adjuvant may be highly dependent on particle morphology, we believe that further investigation of this methodology to assess sub-visible particles in challenging formulations is warranted.

Structural Changes and Aggregation Mechanisms for Anti-Streptavidin IgG1 at Elevated Concentration

Non-native protein aggregation may occur during manufacturing and storage of protein therapeutics, and this may decrease drug efficacy or jeopardize patient safety. From a regulatory perspective, changes in higher order structure due to aggregation are of particular interest but can be difficult to monitor directly at elevated protein concentrations. The present report focuses on non-native aggregation of antistreptavidin (AS) IgG1 at 30 mg/mL under solution conditions that prior work at dilute concentrations (e.g., 1 mg/mL) indicated would result in different aggregation mechanisms. Time-dependent aggregation and structural changes were monitored in situ with dynamic light scattering, small-angle neutron scattering, and Raman scattering and ex situ with far-UV circular dichroism and second-derivative UV spectroscopy. The effects of adding 0.15 M (∼5 w/w %) sucrose were also assessed. The addition of sucrose decreased monomer loss rates but did not change protein-protein interactions, aggregation mechanism(s), or aggregate structure and morphology. Consistent with prior results, altering the pD or salt concentration had the primary effect of changing the aggregation mechanism. Overall, the results provide a comparison of aggregate structure and morphology created via different growth mechanisms using orthogonal techniques and show that the techniques agree at least qualitatively. Interestingly, AS-IgG1 aggregates created at pD 5.3 with no added salt formed the smallest aggregates but had the largest structural changes compared to other solution conditions. The observation that the larger aggregates were also those with less structural perturbation compared to folded AS-IgG1 might be expected to extend to other proteins if the same strong electrostatic repulsions that mediate aggregate growth also mediate structural changes of the constituent proteins within aggregates.

The Role of Aggregates of Therapeutic Protein Products in Immunogenicity: An Evaluation by Mathematical Modeling

Therapeutic protein products (TPP) have been widely used to treat a variety of human diseases, including cancer, hemophilia, and autoimmune diseases. However, TPP can induce unwanted immune responses that can impact both drug efficacy and patient safety. The presence of aggregates is of particular concern as they have been implicated in inducing both T cell-independent and T cell-dependent immune responses. We used mathematical modeling to evaluate several mechanisms through which aggregates of TPP could contribute to the development of immunogenicity. Modeling interactions between aggregates and B cell receptors demonstrated that aggregates are unlikely to induce T cell-independent immune responses by cross-linking B cell receptors because the amount of signal transducing complex that can form under physiologically relevant conditions is limited. We systematically evaluate the role of aggregates in inducing T cell-dependent immune responses using a recently developed multiscale mechanistic mathematical model. Our analysis indicates that aggregates could contribute to T cell-dependent immune response by inducing high affinity epitopes which may not be present in the nonaggregated TPP and/or by enhancing danger signals to break tolerance. In summary, our computational analysis is suggestive of novel insights into the mechanisms underlying aggregate-induced immunogenicity, which could be used to develop mitigation strategies.

The Role of Protein Excipient in Driving Antibody Responses to Erythropoietin

Human serum albumin (HSA) is an excipient present in formulations of several recombinant protein products that are approved for clinical use. We investigated the relative contributions of HSA and HSA particles to the generation of antibody responses against recombinant human erythropoietin (rhEPO) and the excipient HSA itself. Protein samples were characterized before injection for quantities of monomeric proteins, soluble protein aggregates, and nano- and micron-sized particles. rhEPO, containing various concentrations of HSA particles, were injected three times a week for 8 weeks into mice. Hematocrits and the production of anti-rhEPO and anti-HSA antibodies were determined at various time points. Levels of antibodies against rhEPO in mice injected with HSA-containing rhEPO were higher than those in mice treated with HSA-free rhEPO. Mice injected with formulations that contained particles of HSA produced strong anti-HSA antibody responses; whereas these responses were greatly reduced when particle-free formulations were administered. In contrast, anti-rhEPO antibody responses were not affected by the presence of particles.

In Vivo Analysis of the Potency of Silicone Oil Microdroplets as Immunological Adjuvants in Protein Formulations

Subvisible particles in a therapeutic protein product may act as adjuvants to promote unwanted immune responses against the protein. Silicone oil is used as a lubricant in prefilled syringes, and microdroplets of silicone oil are often detected in protein formulations expelled from prefilled syringes. In order to test the adjuvant potency of silicone oil microdroplets, antibody responses in mice to subcutaneous injections of formulations of ovalbumin (OVA) that contained silicone oil microdroplets were measured. These responses were compared against responses to oil-free OVA formulations and to OVA formulations that contained microparticulate aluminum hydroxide ("alum"), the common vaccine adjuvant. When administered with high concentrations of silicone oil microdroplets, OVA formulations elicited strong anti-OVA IgG1 and IgG2a antibody responses. These responses were equivalent to those observed when alum microparticles were added to OVA formulations, suggesting that silicone oil can act as a potent adjuvant. However, when OVA formulations were prepared with lower levels of silicone oil that had been obtained directly from commercial siliconized syringes, the anti-OVA antibody response was not enhanced significantly compared with responses against OVA alone.

Antinociceptive, muscle relaxant and sedative activities of gold nanoparticles generated by methanolic extract of Euphorbia milii

Background

Nanotechnology has potential future for enhancing therapeutic efficacy and reducing the unwanted effects of herbal drugs. The biological research on Euphorbia species has been supported by the use of some plants in traditional medicines. Many species of Euphorbia have been reported as having strong sedative and analgesic effects. In the present research work gold nanoparticles of Euphorbia milii methanolic extract (Au-EM) were synthesized, characterized and tested for antinociceptive, muscle relaxant and sedative activities.

Methods

Au-EM was prepared by stirring 1 mM warm trihydrated tetrachloroaurate solution with E. milii methanolic extract without using any external reducing agents. The gold nanoparticles were characterized by UV-Visible spectroscopy, infrared spectrophotometery, atomic force microscopy and scanning electron microscopy while their stability was evaluated against varying pH and different volumes of sodium chloride (NaCl). The metal sensing capacity of Au-EM was tested towards cobalt, copper, lead, mercury and nickel. Au-EM was evaluated in BALB/c mice at a dose of 10 and 20 mg/kg for antinociceptive, muscle relaxant and sedative activities in comparison with the crude E. milii methanolic extract.

Results

Au-EM showed remarkable stability in different NaCl and pH solutions. Au-EM produced significant (P < 0.01) antinociceptive effect at doses of 10 and 20 mg/kg as compared to the crude E. milii methanolic extract. In the rotarod test, Au-EM showed significant muscle relaxant effect at 10 mg/kg (P < 0.05) and 20 mg/kg (P < 0.01) after 30, 60 and 90 min. In an open field test significant sedative effect (P < 0.05) of Au-EM was observed at 10 and 20 mg/kg. Moreover significant detection sensitivity was demonstrated towards all the tested heavy metals.

Conclusions

These results concluded that the gold nanoparticles improved the potency of E. milii methanolic extract and exhibited significant analgesic, muscle relaxant and sedative properties. The significant metals sensing ability and enhanced stability in different NaCl and pH solutions may enable us to explore different formulations of E. milii gold nanoparticles for potentially effective and safe nano-herbal therapy.

Physical characterization and in vitro biological impact of highly aggregated antibodies separated into size-enriched populations by fluorescence-activated cell sorting

An IgG2 monoclonal antibody (mAb) solution was subjected to stirring, generating high concentrations of nanometer and subvisible particles, which were then successfully size-enriched into different size bins by low-speed centrifugation or a combination of gravitational sedimentation and fluorescence-activated cell sorting (FACS). The size-fractionated mAb particles were assessed for their ability to elicit the release of cytokines from a population of donor-derived human peripheral blood mononuclear cells (PBMC) at two phases of the immune response. Fractions enriched in nanometer-sized particles showed a lower response than those enriched in micron-sized particles in this assay. Particles of 5-10 μm in size displayed elevated cytokine release profiles compared with other size ranges. Stir-stressed mAb particles had amorphous morphology, contained protein with partially altered secondary structure, elevated surface hydrophobicity (compared with controls), and trace levels of elemental fluorine. FACS size-enriched the mAb particle samples, yet did not notably alter the overall morphology or composition of particles as measured by microflow imaging, transmission electron microscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. The utility and limitations of FACS for size separation of mAb particles and potential of in vitro PBMC studies to rank-order the immunogenic potential of various types of mAb particles are discussed.

Dose levels in particulate-containing formulations impact anti-drug antibody responses to murine monoclonal antibody in mice

Dosage levels and particulate contents of therapeutic protein formulations are potential factors that impact immunogenicity of protein therapeutics. Here, we evaluated the effect of dose levels on the immunogenicity of protein particulates formed by adsorbing a murine monoclonal IgG2c/κ antibody (mAb1) onto silicone oil microdroplets, glass, or aluminum hydroxide (Alhydrogel) microparticles. Immune responses to these particulate-containing preparations were compared against responses to solutions of mAb1 that had been ultracentrifuged to minimize particle levels. Formulations containing 5 or 500 μg of adsorbed mAb1 were administered subcutaneously to C57BL/6J or BALB/c mice. Antidrug antibodies (ADAs) were detected using an isotype-specific enzyme-linked immunosorbent assay (ELISA) method or a chemiluminescence method. Sera from BALB/c mice showed greater ADA responses to administration of particles at the 5-μg dose level than at the 500-μg dose level. In sera from C57BL/6J mice, ADA levels detected by ELISA were independent of the particle dose levels tested. ADAs were not detected in sera from C57BL/6J mice performing the chemiluminescence technique. In conclusion, mice administered formulations of a murine antibody adsorbed onto silicone oil microdroplets, glass microparticles, or Alhydrogel(®) showed greater ADA responses that those that received particle-free mAb1 preparations, and responses were greater for formulations containing lower doses of antibody. .

Effects of syringe material and silicone oil lubrication on the stability of pharmaceutical proteins

Currently, polymer-based prefillable syringes are being promoted to the pharmaceutical market because they provide an increased break resistance relative to traditionally used glass syringes. Despite this significant advantage, the possibility that barrel material can affect the oligomeric state of the protein drug exists. The present study was designed to compare the effect of different syringe materials and silicone oil lubrication on the protein aggregation. The stability of a recombinant fusion protein, abatacept (Orencia), and a fully human recombinant immunoglobulin G1, adalimumab (Humira), was assessed in silicone oil-free (SOF) and silicone oil-lubricated 1-mL glass syringes and polymer-based syringes in accelerated stress study. Samples were subjected to agitation stress, and soluble aggregate levels were evaluated by size-exclusion chromatography and verified with analytical ultracentrifugation. In accordance with current regulatory expectations, the amounts of subvisible particles resulting from agitation stress were estimated using resonant mass measurement and dynamic flow-imaging analyses. The amount of aggregated protein and particle counts were similar between unlubricated polymer-based and glass syringes. The most significant protein loss was observed for lubricated glass syringes. These results suggest that newly developed SOF polymer-based syringes are capable of providing biopharmaceuticals with enhanced physical stability upon shipping and handling. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:527–535, 2015

Investigation of the immunogenicity of different types of aggregates of a murine monoclonal antibody in mice

PURPOSE

The potential contribution of protein aggregates to the unwanted immunogenicity of protein pharmaceuticals is a major concern. In the present study a murine monoclonal antibody was utilized to study the immunogenicity of different types of aggregates in mice. Samples containing defined types of aggregates were prepared by processes such as stirring, agitation, exposure to ultraviolet (UV) light and exposure to elevated temperatures.

METHODS

Aggregates were analyzed by size-exclusion chromatography, light obscuration, turbidimetry, infrared (IR) spectroscopy and UV spectroscopy. Samples were separated into fractions based on aggregate size by asymmetrical flow field-flow fractionation or by centrifugation. Samples containing different types and sizes of aggregates were subsequently administered to C57BL/6 J and BALB/c mice, and serum was analyzed for the presence of anti-IgG1, anti-IgG2a, anti-IgG2b and anti-IgG3 antibodies. In addition, the pharmacokinetic profile of the murine antibody was investigated.

RESULTS

In this study, samples containing high numbers of different types of aggregates were administered in order to challenge the in vivo system. The magnitude of immune response depends on the nature of the aggregates. The most immunogenic aggregates were of relatively large and insoluble nature, with perturbed, non-native structures.

CONCLUSION

This study shows that not all protein drug aggregates are equally immunogenic.

UV photodegradation of murine growth hormone: chemical analysis and immunogenicity consequences

During manufacturing, therapeutic proteins may be exposed to ultraviolet (UV) radiation. Such exposure is of concern because UV radiation may cause photooxidative damage to proteins, which in turn could lead to physical changes such as aggregation and enhanced immunogenicity. We exposed murine growth hormone (mGH) to controlled doses of UV radiation, and examined the resulting chemical, physical and immunogenic changes in the protein. mGH chemical structure was analyzed by mass spectrometry after UV irradiation. Photooxidation products detected by mass spectrometry included methionine sulfoxide formed at Met[127] and Met[149] residues, and, tentatively assigned by MS/MS analysis, ether cross-links between original Ser[78] and Cys[188], and Cys[206] and Ser[213], and a thioether cross-link between Cys[17] and Cys[78] residues, transformation of Cys[189] into Ala, and various hydrolytic fragments. Physical damage to UV-irradiated mGH was monitored by infrared spectrometry, chromatographic analyses, and particle counting by micro-flow imaging. UV radiation caused mGH to aggregate, forming insoluble microparticles containing mGH with non-native secondary structure. When administered subcutaneously to Balb/c or Nude Balb/c mice, UV-irradiated mGH provoked antibodies that cross-reacted with unmodified mGH in a fashion consistent with a T-cell dependent immune response. In wildtype Balb/c mice, titers for anti-mGH IgG1 antibodies increased with increasing UV radiation doses.

Recombinant murine growth hormone particles are more immunogenic with intravenous than subcutaneous administration

Evaluation and mitigation of the risk of immunogenicity to protein aggregates and particles in therapeutic protein products remains a primary concern for drug developers and regulatory agencies. To investigate how the presence of protein particles and the route of administration influence the immunogenicity of a model therapeutic protein, we measured the immune response in mice to injections of formulations of recombinant murine growth hormone (rmGH) that contained controlled levels of protein particles. Mice were injected twice over 6 weeks with rmGH formulations via the subcutaneous, intraperitoneal, or intravenous (i.v.) routes. In addition to soluble, monomeric rmGH, the samples prepared contained either nanoparticles of rmGH or both nano- and microparticles of rmGH.The appearance of anti-rmGH IgG1, IgG2a, IgG2b, IgG2c, and IgG3 titers following the second injection of both preparations implies that multiple mechanisms contributed to the immune response. No dependence of the immune response on particle size and distribution was observed. The immune response measured after the second injection was most pronounced when i.v. administration was used. Despite producing high anti-rmGH titers mice appeared to retain the ability to properly regulate and use endogenous growth hormone.

High-dose monoclonal antibodies via the subcutaneous route: challenges and technical solutions, an industry perspective

This review summarizes the various challenges in product development involved in subcutaneous administration of high-dose monoclonal antibodies and attempts to provide an industry perspective of some of the available technologies and potential avenues to overcome these challenges.

Models for evaluation of relative immunogenic potential of protein particles in biopharmaceutical protein formulations

An immune response to a therapeutic protein that compromises the biopharmaceutical activity or cross-reacts with an endogenous protein is a serious clinical event. The role of protein aggregates and particles in biopharmaceutical formulations in mediating this immune response has gained considerable attention over the recent past. Model systems that could consistently and reliably predict the relative immunogenicity of biopharmaceutical protein formulations would be extremely valuable. Several approaches have been developed in an attempt to provide this insight, including in silico algorithms, in vitro tests utilizing human leukocytes and in vivo animal models. This commentary provides an update of these various approaches as well as the author's perspectives on the pros and cons of these different methods.

The potential clinical relevance of visible particles in parenteral drugs

Visible particulates (VP) are one subclass of defects seen during the final visual inspection of parenteral products and are currently one of the top ten reasons for recalls 1,2. The risk posed by particles is still unclear with limited experience reported in humans but remains an important consideration during the manufacture and use of parenteral products. From the experimental and clinical knowledge of the distribution of particulate matter in the body, clinical complications would include events occurring around parenteral administration e.g., as a result of mechanical pulmonary artery obstruction and injection site reaction, or sub-acute or chronic events e.g., granuloma. The challenge is to better understand the implication for patients of single vials with VP and align the risk with the probabilistic detection process used by manufacturers for accept/reject decisions of individual units of product.

Highly aggregated antibody therapeutics can enhance the in vitro innate and late-stage T-cell immune responses

Aggregation of biotherapeutics has the potential to induce an immunogenic response. Here, we show that aggregated therapeutic antibodies, previously generated and determined to contain a variety of attributes (Joubert, M. K., Luo, Q., Nashed-Samuel, Y., Wypych, J., and Narhi, L. O. (2011) J. Biol. Chem. 286, 25118–25133), can enhance the in vitro innate immune response of a population of naive human peripheral blood mononuclear cells. This response depended on the aggregate type, inherent immunogenicity of the monomer, and donor responsiveness, and required a high number of particles, well above that detected in marketed drug products, at least in this in vitro system. We propose a cytokine signature as a potential biomarker of the in vitro peripheral blood mononuclear cell response to aggregates. The cytokines include IL-1β, IL-6, IL-10, MCP-1, MIP-1α, MIP-1β, MMP-2, and TNF-α. IL-6 and IL-10 might have an immunosuppressive effect on the long term immune response. Aggregates made by stirring induced the highest response compared with aggregates made by other methods. Particle size in the 2–10 μm range and the retention of some folded structure were associated with an increased response. The mechanism of aggregate activation at the innate phase was found to occur through specific cell surface receptors (the toll-like receptors TLR-2 and TLR-4, FcγRs, and the complement system). The innate signal was shown to progress to an adaptive T-cell response characterized by T-cell proliferation and secretion of T-cell cytokines. Investigating the ability of aggregates to induce cytokine signatures as biomarkers of immune responses is essential for determining their risk of immunogenicity.

Immunogenicity of protein aggregates--concerns and realities

Protein aggregation is one of the key challenges in the development of protein biotherapeutics. It is a critical product quality issue as well as a potential safety concern due to the increased immunogenicity potential of these aggregates. The overwhelming safety concern has led to an increased development effort and regulatory scrutiny in recent years. The main purposes of this review are to examine the literature data on the relationship between protein aggregates and immunogenicity, to highlight the linkage and existing inconsistencies/uncertainties, and to propose directions for future investigations/development.

Accelerated stability studies of abatacept formulations: comparison of freeze-thawing- and agitation-induced stresses

Accelerated degradation studies are frequently used to screen for formulation conditions that confer adequate shelf life for therapeutic proteins. To speed development cycles, degradation is often accelerated by application of conditions that expose proteins to elevated temperatures, dynamic air-water interfaces created by agitation, or stresses induced by freeze-thaw cycling. The purpose of this case study was to compare freeze-thaw- and agitation-induced aggregations with aggregation previously studied at elevated temperatures (Fast J, Cordes AA, Carpenter JF, Randolph TW. 2009. Biochemistry 48:11724-11736) using the therapeutic fusion protein abatacept as a model. The stability of abatacept against aggregation induced by the freeze-thaw and agitation degradation methods was assessed by size-exclusion chromatography (SEC) and microflow imaging (MFI) analysis. pH conditions that were previously found to increase conformational stability of abatacept and reduce aggregation during incubation at elevated temperature (Fast J, Cordes AA, Carpenter JF, Randolph TW. 2009. Biochemistry 48:11724-11736) also reduced aggregation induced by freeze-thaw cycling and by agitation in this study. Especially in the case of the freeze-thaw cycling, wherein the formation of aggregates was not readily detectable by SEC, MFI proved to be a useful method to characterize the stability of the formulations against aggregation.

Native-like aggregates of factor VIII are immunogenic in von Willebrand factor deficient and hemophilia a mice

The administration of recombinant factor VIII (FVIII) is the first-line therapy for hemophilia A (HA), but 25%-35% of patients develop an inhibitory antibody response. In general, the presence of aggregates contributes to unwanted immunogenic responses against therapeutic proteins. FVIII has been shown to form both native-like and nonnative aggregates. Previously, we showed that nonnative aggregates of FVIII are less immunogenic than the native protein. Here, we investigated the effect of native-like aggregates of FVIII on immunogenicity in HA and von Willebrand factor knockout (vWF(-/-)) mice. Mice immunized with native-like aggregates showed significantly higher inhibitory antibody titers than animals that received native FVIII. Following restimulation in vitro with native FVIII, the activation of CD4+ T-cells isolated from mice immunized with native-like aggregates is approximately fourfold higher than mice immunized with the native protein. Furthermore, this is associated with increases in the secretion of proinflammatory cytokines IL-6 and IL-17 in the native-like aggregate treatment group. The results indicate that the native-like aggregates of FVIII are more immunogenic than native FVIII for both the B-cell and the T-cell responses.

Particles in therapeutic protein formulations, Part 1: overview of analytical methods

The presence of particles is a major issue during therapeutic protein formulation development. Both proteinaceous and nonproteinaceous particles need to be analyzed not only due to the requirements of the Pharmacopeias but also to monitor the stability of the protein formulation. Increasing concerns about the immunogenic potential together with new developments in particle analysis make a comparative description of established and novel analytical methods useful. Our review aims to provide a comprehensive overview on analytical methods for the detection and characterization of visible and subvisible particles in therapeutic protein formulations. We describe the underlying theory, benefits, shortcomings, and illustrative examples for quantification techniques, as well as characterization techniques for particle shape, morphology, structure, and identity.