Recommendations for the Development and Validation of Neutralizing Antibody Assays in Support of Biosimilar Assessment

Unique challenges required reassessment and alterations to critical reagents to rescue a neutralizing antibody assay

Aim: To redevelop a neutralizing antibody (NAb) assay to be much more drug tolerant, have a large dynamic range and have high inhibition when using high levels of positive control (PC).Materials & methods: Early assay data suggested that typical biotin labeling of the capture reagent (Drug 1, produced in a human cell line) was blocking it from binding with the PC or the detection target, and that the detection target was out competing the PC. Methodical biotin labeling experiments were performed at several challenge ratios and an Fc linker was added to the detection target.Results & conclusion: A larger dynamic range, high inhibition and higher drug tolerance were achieved by adding an acid dissociation step to the assay, performing atypical biotin labeling of Drug 1 and switching to a detection target that contained an Fc linker to increase steric hinderance and decrease its binding affinity to Drug 1.

2023 White Paper on Recent Issues in Bioanalysis: ISR for ADA Assays, the Rise of dPCR vs qPCR, International Reference Standards for Vaccine Assays, Anti-AAV TAb Post-Dose Assessment, NanoString Validation, ELISpot as Gold Standard (Part 3 - Recommendations on Gene Therapy, Cell Therapy, Vaccines Immunogenicity & Technologies; Biotherapeutics Immunogenicity & Risk Assessment; ADA/NAb Assay/Reporting Harmonization)

The 17th Workshop on Recent Issues in Bioanalysis (17th WRIB) took place in Orlando, FL, USA on June 19-23, 2023. Over 1000 professionals representing pharma/biotech companies, CROs, and multiple regulatory agencies convened to actively discuss the most current topics of interest in bioanalysis. The 17th WRIB included 3 Main Workshops and 7 Specialized Workshops that together spanned 1 week to allow an exhaustive and thorough coverage of all major issues in bioanalysis of biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on "EU IVDR 2017/746 Implementation and impact for the Global Biomarker Community: How to Comply with these NEW Regulations" and on "US FDA/OSIS Remote Regulatory Assessments (RRAs)" were the special features of the 17th edition. As in previous years, WRIB continued to gather a wide diversity of international, industry opinion leaders and regulatory authority experts working on both small and large molecules as well as gene, cell therapies and vaccines to facilitate sharing and discussions focused on improving quality, increasing regulatory compliance, and achieving scientific excellence on bioanalytical issues. This 2023 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2023 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 3) covers the recommendations on Gene Therapy, Cell therapy, Vaccines and Biotherapeutics Immunogenicity. Part 1A (Mass Spectrometry Assays and Regulated Bioanalysis/BMV), P1B (Regulatory Inputs) and Part 2 (Biomarkers, IVD/CDx, LBA and Cell-Based Assays) are published in volume 16 of Bioanalysis, issues 8 and 9 (2024), respectively.

Pharmacokinetic Profiles of a Proposed Biosimilar Ustekinumab (BFI-751): Results From a Randomized Phase 1 Trial

BioFactura has developed a proposed biosimilar candidate (BFI-751) to ustekinumab reference product. Results are reported for the first-in-human trial designed to compare the pharmacokinetic profiles, safety, and immunogenicity of BFI-751 and ustekinumab reference products from the European Union and United States as well as similarity of the EU and US reference products. This was a multicenter, randomized, double blind, 3-parallel-group study (trial ID: NCT04843631). Healthy subjects were randomized to receive a single subcutaneous dose of 45 mg of BFI-751, EU ustekinumab, or US ustekinumab. The pharmacokinetic parameters were area under the concentration-time curve (AUC) from time zero to infinity, AUC from time zero to the last quantifiable concentration, and maximum concentration. Safety, tolerability, and immunogenicity data were also reported. Pairwise comparisons among the 3 treatments all met the standard bioequivalence criteria that the 90% confidence interval of the geometric mean ratios of AUC from time zero to infinity, AUC from time zero to the last quantifiable concentration, and maximum concentration are completely within the acceptance interval of 80%-125%. There were no marked differences in the safety and tolerability profiles for subjects receiving BFI-751 as compared to EU or US ustekinumab. Treatment-emergent adverse events were mild to moderate for all treatment groups.

A competitive ligand-binding assay to detect neutralizing antibodies to a bispecific drug using a multiplex Meso Scale Discovery platform

Background: Monitoring appearance of neutralizing antibodies (NAbs) to multidomain large molecule drugs is a challenging task. Materials & methods: Here, we report development of a competitive ligand-binding assay for detection of NAbs to a bispecific candidate drug using a multiplex Meso Scale Discovery platform, which allows for detection of NAbs to both drug arms in the same sample. Results: The assay has sensitivity better than 250 ng/ml and is tolerant to the presence of drug at concentration >600 μg/ml and to the level of soluble target(s) >400 ng/ml. Conclusion: Our data suggest that multiplex approach can be successfully used for development of NAb assays in competitive ligand-binding assay format.

Development of a Cell-Based Assay for the Detection of Neutralizing Antibodies to PF-06730512 Using Homogenous Time-Resolved Fluorescence

The administration of biotherapeutics has the potential to induce potent immune responses. Among these responses, the production of anti-drug antibodies (ADA), including a subset of ADA referred to as neutralizing antibodies (NAb), is of heightened concern. Aside from their capacity to alter the pharmacological profile of a given biotherapeutic, NAb can also pose significant safety risks, especially in instances where an endogenous counterpart to the drug exists. As such, the inclusion of an assay to detect NAb in clinical samples is critical to the effectiveness of a tiered approach to immunogenicity assessment. PF-06730512 is a biotherapeutic protein being developed for the treatment of primary Focal Segmental Glomerulosclerosis (FSGS). To support the immunogenicity assessment of PF-06730512, a cell-based assay was developed for the detection of NAb in FSGS serum samples. Herein, we describe the development of the assay with a focus on the challenges faced, including drug and blood collection tube interferences in NAb detection. The outcome of our efforts was a robust assay capable of detecting 1 μg/mL of a NAb positive control in the presence of clinically relevant drug concentrations up to 30 μg/mL.

Recommendations for the Development and Validation of Immunogenicity Assays in Support of Biosimilar Programs

For biosimilar drug development programs, it is essential to demonstrate that there are no clinically significant differences between the proposed biosimilar therapeutic (biosimilar) and its reference product (originator). Based on a stepwise comprehensive comparability exercise, the biosimilar must demonstrate similarity to the originator in physicochemical characteristics, biological activity, pharmacokinetics, efficacy, and safety, including immunogenicity. The goal of the immunogenicity assessment is to evaluate potential differences between the proposed biosimilar product and the originator product in the incidence and severity of human immune responses. Establishing that there are no clinically meaningful differences in the immune response between the products is a key element in the demonstration of biosimilarity. An issue of practical, regulatory, and financial importance is to establish whether a two-assay (based on the biosimilar and originator respectively) or a one-assay approach (based on the biosimilar) is optimal for the comparative immunogenicity assessment. This paper recommends the use of a single, biosimilar-based assay for assessing immunogenic similarity in support of biosimilar drug development. The development and validation of an ADA assay used for a biosimilar program should include all the assessments recommended for an innovator program (10-16, 29). In addition, specific parameters also need to be evaluated, to gain confidence that the assay can detect antibodies against both the biosimilar and the originator. Specifically, the biosimilar and the originator should be compared in antigenic equivalence, to assess the ability of the biosimilar and the originator to bind in a similar manner to the positive control(s), as well as in the confirmatory assay and drug tolerance experiments. Practical guidance for the development and validation of anti-drug antibody (ADA) assays to assess immunogenicity of a biosimilar in comparison to the originator, using the one-assay approach, are described herein.

Addressing soluble target interference in the development of a functional assay for the detection of neutralizing antibodies against a BCMA-CD3 bispecific antibody

Proper evaluation of immunogenicity during clinical development of biotherapeutics is a major challenge to bioanalytical scientists, in part due to matrix interference in anti-drug antibody (ADA) and neutralizing antibody (NAB) assays. If not addressed, matrix interference could confound the immunogenicity assessment of a given biotherapeutic in clinical development. To support clinical development of a B cell maturation antigen (BCMA)-CD3 bispecific antibody, a cell-based NAB assay was developed as part of a tiered approach to evaluating the immunogenicity of the drug. The assay endpoint (T cell activation) was chosen based on its strong association with the mechanism of action of the drug. The BCMA-CD3 bispecific antibody activates T cells through simultaneous binding of CD3 on T cells and BCMA on target cells. In this system, T cell activation was assessed through the measurement of luciferase activity in an engineered Jurkat cell line. In the presence of NAB, the degree of T cell activation measured by the amount of luciferase activity can be reduced. During method development, soluble BCMA (sBCMA) interference in the NAB assay was apparent. The binding of sBCMA to the anti-BCMA domain of the bispecific drug led to reduced T cell activation, which caused false positive results in NAB testing. To mitigate this interference, several strategies to eliminate sBCMA were investigated. Among the procedures tested, a bead-based approach proved most effective in depleting sBCMA, while maintaining robust assay performance and achieving fit-for-purpose sensitivity. Using this sample pretreatment procedure, the NAB assay tolerated sBCMA up to 2 μg/mL, or approximately four times the estimated median sBCMA concentration in serum samples from patients with active multiple myeloma.

Comparative immunogenicity assessment of biosimilars

The first anticancer biosimilars have entered clinical use, with many others under clinical development. Like all biologics, biosimilars may elicit unwanted immune responses that can significantly impact clinical efficacy and safety. Head-to-head immunogenicity assessment of biosimilars and their reference biologics should, therefore, be a critical component of a biosimilar's clinical development program. Various bioanalytical platforms may be used to detect and characterize immune responses, each having relative strengths and weaknesses. To fully recognize the clinical relevance of such data, regulators must be able to interpret immunogenicity results in an assay-specific context as well as in perspective of clinical pharmacology, efficacy and safety. Herein, we discuss current challenges imposed by global regulatory requirements for immunogenicity assessment of biosimilars.