Monoclonal Antibody Dimers Induced by Low pH, Heat, or Light Exposure Are Not Immunogenic Upon Subcutaneous Administration in a Mouse Model

Impact of Stress on the Immunogenic Potential of Adalimumab

Monoclonal antibodies against tumor necrosis factor-alpha (TNFα) are widely used for treatment of inflammatory diseases. However, despite the inhibitory effect this class of drugs has on the immune system, anti-drug antibodies are often formed with continuous use. Particles formed during stress conditions, which can be used to simulate storage and handling conditions of commercial antibodies, have previously been associated with the formation of anti-drug antibodies. This study investigates the relationship between particles, oligomerization, folding and chemical degradation on the in vitro cytokine response toward the TNFα inhibitor adalimumab. Adalimumab aggregates generated using stir and heat stress were fractionated into distinct sub-populations, and their structure and immunogenic potential were evaluated. A chemically degraded sample of adalimumab was included to compare particle composition with the milder accelerated heat and stir stressed conditions. Particles from stressed adalimumab samples induced elevated cytokine levels and CD4+ T cell proliferation in vitro compared to non-stressed samples. Samples enriched with both submicron and subvisible particles of adalimumab induced the strongest cytokine release and the strongest CD4+ T cell proliferation despite maintaining some TNFα inhibitory functionality. Samples that were stressed and subsequently purified of subvisible and submicron particles did not elicit a significantly higher cytokine response or show increased CD4+ T cell proliferation compared to a non-stressed sample. Oxidation-induced chemical modifications in adalimumab, mainly in Met, His, Trp, and Tyr, were not found to be sufficient in absence of particle formation to induce increased CD4+ T cell proliferation or cytokine release despite less decreased TNFα inhibitory activity of adalimumab. These observations provide further evidence that particles do indeed potentiate the immunogenic potential of adalimumab.

Relationship between aggregation of therapeutic proteins and agitation parameters: Acceleration and frequency

An increase in protein aggregates during transportation should be suppressed in therapeutic protein products because the aggregates have a potential risk of immunogenicity. In this study, three protein solutions in vials were exposed to tri-axial vibration with various combinations of frequency and acceleration using a transportation test system to investigate the relationship between low g-force stresses and protein aggregate generation. The number concentration of micron aggregates detected by flow imaging analysis increased markedly when the acceleration and frequency of agitation were within a specific range, in other words, above a threshold. This threshold was common among the three protein solutions. The suppression of micron aggregate formation by adding a surfactant suggested that agitation above the threshold increased micron aggregates mainly via interface-mediated routes. Notably, agitation, including agitation below the threshold, accelerated spontaneous oligomerization (nanometer aggregate generation) of proteins in bulk solution even in the presence of the surfactant. Studies of stability against mechanical stresses (e.g., a random vibration test to simulate actual shipment, with a time-compressed setting by increasing acceleration) need to be performed and discussed with careful consideration of the threshold for generating micron aggregates.

Machine Learning Analysis Provides Insight into Mechanisms of Protein Particle Formation Inside Containers During Mechanical Agitation

Container choice can influence particle generation within protein formulations. Incompatibility between proteins and containers can manifest as increased particle concentrations, shifts in particle size distributions and changes in particle morphology distributions. In this study, flow imaging microscopy (FIM) combined with machine learning-based goodness-of-fit hypothesis testing algorithms were used in accelerated stability studies to investigate the impact of containers on particle formation. Containers in four major container categories subdivided into eleven container types were filled with monoclonal antibody formulations and agitated with and without headspace, producing subvisible particles. Digital images of the particles were recorded using flow imaging microscopy and analyzed with machine learning algorithms. Particle morphology distributions depended on container category and type, revealing differences that would not have been obvious by analysis of particle concentrations or container surface characteristics alone. Additionally, the algorithm was used to compare morphologies of particles generated in containers against those generated using isolated stresses at air-liquid and container-air-liquid interfaces. These comparisons showed that the morphology distributions of particles formed during agitation most closely resemble distributions that result from exposure of proteins to moving triple interface lines at points where container-air-liquid interfaces intersect. The approach described here can be used to identify dominant causes of particle generation due to protein-container interactions.

Structure-Activity Relationship of the Dimeric and Oligomeric Forms of a Cytotoxic Biotherapeutic Based on Diphtheria Toxin

Protein aggregation is a well-recognized problem in industrial preparation, including biotherapeutics. These low-energy states constantly compete with a native-like conformation, which is more pronounced in the case of macromolecules of low stability in the solution. A better understanding of the structure and function of such aggregates is generally required for the more rational development of therapeutic proteins, including single-chain fusion cytotoxins to target specific receptors on cancer cells. Here, we identified and purified such particles as side products of the renaturation process of the single-chain fusion cytotoxin, composed of two diphtheria toxin (DT) domains and interleukin 13 (IL-13), and applied various experimental techniques to comprehensively understand their molecular architecture and function. Importantly, we distinguished soluble purified dimeric and fractionated oligomeric particles from aggregates. The oligomers are polydisperse and multimodal, with a distribution favoring lower and even stoichiometries, suggesting they are composed of dimeric building units. Importantly, all these oligomeric particles and the monomer are cystine-dependent as their innate disulfide bonds have structural and functional roles. Their reduction triggers aggregation. Presumably the dimer and lower oligomers represent the metastable state, retaining the native disulfide bond. Although significantly reduced in contrast to the monomer, they preserve some fraction of bioactivity, manifested by their IL-13RA2 receptor affinity and selective cytotoxic potency towards the U-251 glioblastoma cell line. These molecular assemblies probably preserve structural integrity and native-like fold, at least to some extent. As our study demonstrated, the dimeric and oligomeric cytotoxin may be an exciting model protein, introducing a new understanding of its monomeric counterpart’s molecular characteristics.

Oxidation and Deamidation of Monoclonal Antibody Products: Potential Impact on Stability, Biological Activity, and Efficacy

The role in human health of therapeutic proteins in general, and monoclonal antibodies (mAbs) in particular, has been significant and is continuously evolving. A considerable amount of time and resources are invested first in mAb product development and then in clinical examination of the product. Physical and chemical degradation can occur during manufacturing, processing, storage, handling, and administration. Therapeutic proteins may undergo various chemical degradation processes, including oxidation, deamidation, isomerization, hydrolysis, deglycosylation, racemization, disulfide bond breakage and formation, Maillard reaction, and β-elimination. Oxidation and deamidation are the most common chemical degradation processes of mAbs, which may result in changes in physical properties, such as hydrophobicity, charge, secondary or/and tertiary structure, and may lower the thermodynamic or kinetic barrier to unfold. This may predispose the product to aggregation and other chemical modifications, which can alter the binding affinity, half-life, and efficacy of the product. This review summarizes major findings from the past decade on the impact of oxidation and deamidation on the stability, biological activity, and efficacy of mAb products. Mechanisms of action, influencing factors, characterization tools, clinical impact, and risk mitigation strategies have been addressed.

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.

Immunogenicity of Bioproducts: Cellular Models to Evaluate the Impact of Therapeutic Antibody Aggregates

Patients treated with bioproducts (BPs) frequently develop anti-drug antibodies (ADAs) with potential neutralizing capacities leading to loss of clinical response or potential hypersensitivity reactions. Many factors can influence BP immunogenicity and could be related to the patient, the treatment, as well as to the product itself. Among these latter factors, it is now well accepted that BP aggregation is associated with an increased potential for immunogenicity, as aggregates seem to be correlated with ADA development. Moreover, the presence of high-affinity ADAs suggests a CD4 T-cell dependent adaptive immune response and therefore a pivotal role for antigen-presenting cells (APCs), such as dendritic cells (DCs). In this review, we address the in vitro methods developed to evaluate how monoclonal antibodies could trigger the immunization process by focusing on the role of aggregated antibodies in the establishment of this response. In particular, we will present the different cell-based assays that have been used to assess the potential of antibodies and their aggregates to modulate cellular mechanisms leading to activation and the biological parameters (cellular activation markers, proliferation and secreted molecules) that can be measured to evaluate the different cell activation stages and their consequences in the propagation of the immune response. Indeed, the use of such strategies could help evaluate the risk of BP immunogenicity and their role in mitigating this risk.

Accelerated Aggregation Studies of Monoclonal Antibodies: Considerations for Storage Stability

Aggregation of mAbs is a crucial concern with respect to their safety and efficacy. Among the various properties of protein aggregates, it is emerging that their size can potentially impact their immunogenicity. Therefore, stability studies of antibody formulations should not only evaluate the rate of monomer loss but also determine the size distribution of the protein aggregates, which in turn depends on the aggregation mechanism. Here, we study the aggregation behavior of different formulations of 2 monoclonal immunoglobulins (IgGs) in the temperature range from 5°C to 50°C over 52 weeks of storage. We show that the aggregation kinetics of both antibodies follow non-Arrhenius behavior and that the aggregation mechanisms change between 40°C and 5°C, leading to different types of aggregates. Specifically, for a given monomer conversion, dimer formation dominates at low temperatures, while larger aggregates are formed at higher temperatures. We further show that the stability ranking of different molecules as well as of different formulations is drastically different at 40°C and 5°C while it correlates better between 30°C and 5°C. Our findings have implications for the level of information provided by accelerated aggregation studies with respect to protein stability under storage conditions.