EBF recommendation on practical management of critical reagents for antidrug antibody ligand-binding assays

A comprehensive LC-MS based study of factors influencing biotinylation of critical reagents

Aim: Critical reagents (CR) are applied in ligand binding assays (LBA) and biotinylation is a widely conjugation method used for critical reagents. However, insufficient characterization and inconsistent biotinylation can lead to LBA failures and necessitate extensive troubleshooting. This publication developed the detection of biotinylated CR and evaluates efficiency of biotinylation conditions to ensure the reliability of reagents and accuracy when implemented in LBA.Materials & methods: Intact mass analysis was applied to characterize a CR with complex glycosylation and biotinylation patterns. Peptide mapping was developed to identify the biotinylation sites.Results: Biotinylation degrees and sites were clearly illustrated.Conclusion: A CR and its biotinylation were successfully characterized. The relationship between biotinylation efficiency and labeling conditions was clearly illustrated.

Critical reagent considerations for immunogenicity assay development for bispecific biotherapeutic candidates

Aim: To demonstrate the importance of critical reagent characterization for immunogenicity assay development for multi-specific drugs using two case studies.Methods: Bridging anti-drug antibody (ADA) assay with acid-dissociated samples were used for both cases.Results: In the first case study, the unexpected interference in an ADA assay from clinical samples was identified; a model was created to replicate the issue, and an anti-target antibody was identified to mitigate the target interference. In the second case study, an issue due to non-specific binding of a domain-specific confirmatory reagent was identified, and various mitigation techniques were evaluated.Conclusion: A thorough characterization of the critical reagents helped identify the issues with these ADA case studies and provided strategies for resolving them.

A Case Study for Critical Reagent Qualification for Ligand Binding Assays Using Equivalence Test Methodology

Qualifying critical reagents in ligand binding assays by parallel testing of current and candidate reagent lots is recommended by regulatory agencies and industry groups, but specific guidance on the format of reagent qualification experiments is limited. Equivalence testing is a statistically sound approach that is consistent with the objective of critical reagent qualification. We present power analysis for equivalence regions ranging from 1.25- to 1.5-fold multiples of the GM ratio (centered on 1) of current and candidate lots, over a range of assay variability from 5 to 30% coefficient of variation (CV). A 1.25-fold equivalence region can be tested using 6 to 12 plates per lot for assays with up to 15% CV but is not practical for more variable assays. For these assays, wider equivalence regions are justified so long as care is taken to avoid assay drift and the assay remains suitable for the intended use. The equivalence test method is illustrated using historical data from passing and failing reagent qualification experiments. Simulation analysis was performed to support the design of qualification experiments using 6, 12, or 18 plates per lot over a broad range of assay variability. A challenge in implementing the equivalence test approach is selecting an appropriate equivalence region. Equivalence regions providing 90% power using 12 plates/lot were consistent with 1.5σ bounds, which are recommended for equivalence testing of critical quality attributes of biosimilars.

Use of capillary-mediated vitrification to produce thermostable, single-use antibody conjugates as immunoassay reagents

The performance of enzyme-linked immunoassays is directly dependent on the storage, handling, and long-term stability of the critical reagents used in the assay. Currently, antibody reagents are routinely stored as concentrated, multi-use, frozen aliquots. This practice results in material waste, adds complexity to laboratory workflows, and can compromise reagents via cross-contamination and freeze-thaw damage. While refrigeration or freezing can slow down many degradation processes, the freezing process itself can have damaging effects, including introduction of aggregation and microheterogeneity. To address these challenges, we evaluated the application of capillary-mediated vitrification (CMV) as a tool for storing antibody reagents in a thermostable, single-use format. CMV is a novel biopreservation method that enables vitrification of biological materials without freezing. Using an anti-human IgG-alkaline phosphatase conjugate as a model system, we prepared CMV-stabilized aliquots which were stored in a single-use format at temperatures ranging from 25 to 55 °C for up to 3 months. Each stabilized aliquot contained enough antibody to perform a single assay run. We evaluated the assay performance and functional stability of the CMV-stabilized reagents using a plate-based ELISA. Assays run using the CMV stabilized reagents exhibited good linearity and precision that was comparable to results obtained with a frozen control. Throughout the stability study, the maximum signal and EC50s observed for ELISAs run using CMV-stabilized reagents were generally consistent with those obtained using a frozen control. These results indicate that the CMV process has the potential to improve both reagent stability and long-term assay performance, while also reducing reagent waste and simplifying assay workflows.

Determination of label efficiency and label degree of critical reagents by LC-MS and native MS

Degree of labeling and label efficiency are key factors for optimal characterization of critical reagents that are used in ligand binding assays. Here, three case studies are shown demonstrating how liquid chromatography-mass spectrometry (LC-MS) was utilized to characterize critical reagents using three unique methodologies. Critical reagent batches were prepared for LC-MS analysis by use of: 20 mM dithiothreitol (DTT) (Case 1), rapid PNGaseF (Case 2), and a mobile phase diluent (Case 3). LC-MS was run at three different MS method conditions in each troubleshooting case specific for reduced IgG, intact IgG, and native LC-MS, respectively. Specified LC-MS methods based on sample type and configuration elucidated clear MS profiles, allowing for degree of labeling and label efficiencies to be calculated. Ultimately the LC-MS analyses were fine-tuned for critical reagent characterization, and practices for analyzing similar reagents in the future can be established.

Recommendations and discussion points on immunogenicity, biomarkers, automation/technology and protein-MS from the 2021 European Bioanalysis Forum Focus Workshops

During the first half of 2021, and due to the SARS-CoV-2 pandemic preventing in-person meetings, the European Bioanalysis Forum organized four workshops as live interactive online meetings. The themes discussed at the workshops were carefully selected to match the cyberspace dynamics of the meeting format. The first workshop was a training day on challenges related to immunogenicity. The second one focused on biomarkers and continued the important discussion on integrating the principles of Context of Use (CoU) in biomarker research. The third workshop was dedicated to technology, that is, cutting-edge development in cell-based and ligand-binding assays and automation strategies. The fourth was on progress and the continued scientific and regulatory challenges related to peptide and protein analysis with MS. In all four workshops, the European Bioanalysis Forum included a mixture of scientific and regulatory themes, while reminding the audience of important strategic aspects and our responsibility toward the patient.

Secondary failure: immune responses to approved protein therapeutics

Recombinant therapeutic proteins are a broad class of biological products used to replace dysfunctional human proteins in individuals with genetic defects (e.g., factor VIII for hemophilia) or, in the case of monoclonal antibodies, bind to disease targets involved in cancers, autoimmune disorders, or other conditions. Unfortunately, immunogenicity (immune response to the drug) remains a key impediment, potentially affecting the safety and efficacy of these therapeutics. Immunogenicity risk is routinely evaluated during the licensure of therapeutic proteins. However, despite eliciting anti-drug immune responses in at least some patients, most protein drugs are nevertheless licensed as they address unmet medical needs. The pre-licensure immunogenicity assessments of therapeutic proteins are the subject of numerous reviews and white papers. However, observation and clinical management of the immunogenicity of approved therapeutic proteins face additional challenges. We survey the immunogenicity of approved therapeutic proteins, discuss the clinical management of immunogenicity, and identify the challenges to establishing clinically relevant immunogenicity assays for use in routine clinical practice.

The impact of ligand binding based assays critical reagent characterization and storage

Biological critical reagents are the foundation of many bioanalytical methods and often chemically modified or conjugated with various chemical tags. As such, the quality and performance of these methods are inherently tied to the quality and stability of critical reagents. This article will outline recommendations for conjugated critical reagent development and characterization. Examples of the impact of regent quality will be discussed for the two common bioanalytical assays in support of drug development for biotherapeutics. Finally, a brief discussion of conjugated reagent stability and recommendations for storage and testing will be presented.

Critical reagent generation, characterization, handling and storage workflows: impact on ligand binding assays

The foundation of pharmacokinetics and antidrug antibodies assay robustness relies on the use of high-quality reagents. Over the past decade, there has been increasing interest within the pharmaceutical industry, as well as regulators, on defining best practices and scientific approaches for generation, characterization and handling of critical reagents. In this review, we will discuss current knowledge and practices on critical reagent workflows and state-of-the-art approaches for characterization, generation, stability and storage and how each of these steps can impact ligand-binding assay robustness.

Critical reagents issues & solutions for anti-drug antibody assays

Background: Anti-Drug Antibody assays (ADA) are developed and constructed with biological and chemical reagents. Capture and detector reagents as well as ADA standard are considered critical for the performance's characteristics of a bridging assay. Current literature well describes theoretical considerations to manage critical reagents (CR) life cycle management. Nevertheless, those recommendations must be completed by a pragmatic approach which have to be exemplified. Methodology: This article intends to present and describe two study cases of bioanalytical challenge coming from the practical experience of dealing with ADA CR and offers a concrete explanation of how to solve issues. Conclusion: An appropriate management of ADA CR goes through availability anticipation, characterization and by a scientific understanding process of assay and reagents inconsistency.

The importance of quality critical reagents for the entire developmental lifecycle of a biopharmaceutical: a pharmacokinetic case study

Background: High-quality critical reagents are essential to the successful support of biotherapeutic drug development regardless of the analytical platform used for support. The lack of such a reagent, early in the development lifecycle of a biotherapeutic can have detrimental impact on resource and translation of data across development phases. Results: Here, a pharmacokinetic assay case study is shared that illustrates what can occur when there is a lack of a reproducible and sustainable critical reagent early in the development lifecycle of a biotherapeutic. Various assay formats and critical reagents, as well as reagents generation programs, were initiated to find a reagent and assay format which was fit for purpose. Conclusions: Identification of appropriate critical reagents early in the development lifecycle of a biotherapeutic as advantageous.

A strategic approach to nonclinical immunogenicity assessment: a recommendation from the European Bioanalysis Forum

Immunogenicity assays are required to evaluate anti-drug antibody (ADA) responses that can be generated against biotherapeutic modalities. Regulatory guidelines focus on clinical requirements, yet it has become apparent that industry has applied these clinical recommendations for immunogenicity assessment to nonclinical studies in varying degrees. ADAs are an anticipated outcome of dosing a humanized or fully human biotherapeutic into an animal. However, a nonclinical ADA response is rarely predictive of the immunogenic potential in humans. The addendum to ICH S6 recommends that immunogenicity should be explicitly examined where there is: evidence of altered pharmacodynamic activity; unexpected changes in exposure in the absence of a pharmacodynamic marker or evidence of immuno-mediated reactions. The European Bioanalytical Forum has extensively discussed and reached a consensus on a minimal strategic approach of when and what to include for nonclinical immunogenicity assessments. Additionally, this paper recommends a strategy for ADA assay validation and sample analysis for those cases when it is considered necessary to include an immunogenicity assessment in nonclinical toxicology studies.