Development and validation of a functional cell-based neutralizing antibody assay for ipilimumab

Development and Validation of a Cell-Based Binding Neutralizing Antibody Assay for an Antibody-Drug Conjugate

The utilization of antibody-drug conjugates (ADCs) has gained considerable attention in the field of targeted cancer therapy due to their ability to synergistically combine the specificity of monoclonal antibodies (mAbs) and the potency of small molecular drugs. However, the immunogenic nature of the antibody component within ADCs warrants the need for robust immunogenicity testing, including a neutralizing antibody (NAb) assay. Since the mechanism of action (MOA) of the ADC is to first bind to the target cells and then release the payload intracellularly to kill the cells, the most relevant NAb assay format would be a cell-based killing assay. However, in this paper, we present a case where a cell-based killing assay could not be developed after multiple cell lines and NAb-positive controls (PC) had been tested. Surprisingly, contrary to our expectations, all NAb PCs tested exhibited an increased killing effect on the target cells, instead of the expected protective response. This unexpected phenomenon most likely is due to the non-specific internalization of drug/NAb complexes via FcγRs, as an excessive amount of human IgG1 and mouse IgG2a, but not mouse IgG1, greatly inhibited drug or drug/NAb complexes induced cell death. To overcome this obstacle, we implemented a novel cell-based binding assay utilizing the Meso Scale Discovery (MSD) platform. We also propose that an in vitro cell killing NAb assay is limited to at best monitoring the target binding and internalization induced cell death, but not by-stander killing induced by prematurely released or dead-cell released payload, hence cannot really mimic the in vivo MOA of ADC.

Phage-derived anti-idiotype and anti-YTE antibodies in development of MK-1654 pharmacokinetic and immune response assays

Background: MK-1654 is a fully human monoclonal antibody with YTE mutations currently in phase III clinical trials for prophylactic use in protecting infants from human respiratory syncytial virus infection. Materials & methods: We generated anti-idiotype (anti-ID) and anti-YTE antibodies against MK-1654 by panning with MorphoSys HuCal phage libraries, and used the antibodies in the development of MK-1654 pharmacokinetic (PK) and immune response (IR) assays. Results: Detection of MK-1654 in nonhuman primate and human nasal wash samples showed combined use of anti-ID and anti-YTE antibodies can deliver desired sensitivity and accuracy in PK studies. IR studies showed anti-ID can serve as suitable positive control in neutralizing antibody assays. Conclusion: Phage-derived anti-IDs and anti-YTEs are suitable for PK and IR assays.

2022 White Paper on Recent Issues in Bioanalysis: Enzyme Assay Validation, BAV for Primary End Points, Vaccine Functional Assays, Cytometry in Tissue, LBA in Rare Matrices, Complex NAb Assays, Spectral Cytometry, Endogenous Analytes, Extracellular Vesicles Part 2 - Recommendations on Biomarkers/CDx, Flow Cytometry, Ligand-Binding Assays Development & Validation; Emerging Technologies; Critical Reagents Deep Characterization

The 16th Workshop on Recent Issues in Bioanalysis (16th WRIB) took place in Atlanta, GA, USA on September 26-30, 2022. 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 16th WRIB included 3 Main Workshops and 7 Specialized Workshops that together spanned 1 week in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on ICH M10 BMV final guideline (focused on this guideline training, interpretation, adoption and transition); mass spectrometry innovation (focused on novel technologies, novel modalities, and novel challenges); and flow cytometry bioanalysis (rising of the 3rd most common/important technology in bioanalytical labs) were the special features of the 16th 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 2022 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 2022 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 2) covers the recommendations on LBA, Biomarkers/CDx and Cytometry. Part 1 (Mass Spectrometry and ICH M10) and Part 3 (Gene Therapy, Cell therapy, Vaccines and Biotherapeutics Immunogenicity) are published in volume 15 of Bioanalysis, issues 16 and 14 (2023), respectively.

Development of a Cell-based Neutralizing Antibody Assay for Zinpentraxin Alfa: Challenges and Mitigation Strategies

Therapeutic protein drugs can potentially induce immune responses in patients and result in the production of anti-drug antibodies (ADAs), including a subset of ADAs called neutralizing antibodies (NAbs) that might cause loss of efficacy by inhibiting clinical activities of the drug. Herein, we describe the unique challenges encountered during the development of a fit-for-purpose cell-based NAb assay for a new protein modality, zinpentraxin alfa, including our strategies for assay design to overcome various matrix interferences and improve assay drug tolerance. We demonstrated that a typical biotin-drug extraction with acid dissociation (BEAD) approach alone was not sufficient to eliminate matrix interferences in this assay. Instead, the combination of the BEAD and ZebaTM spin size exclusion plate (SEP) was required to achieve the desirable assay performance. We also demonstrated that appropriate acidic buffers were critical in sample pretreatment to improve assay drug tolerance, which not only dissociated the drug/NAb immune complex but also effectively and irreversibly denatured the free drug. The final assay performed well with confirmed assay robustness and suitability for the clinical applications.

A Novel Neutralization Antibody Assay Method to Overcome Drug Interference with Better Compatibility with Acid-Sensitive Neutralizing Antibodies

Immunogenicity testing to detect and characterize anti-drug antibody (ADA) is required for almost all biotherapeutics. Monoclonal antibody biotherapeutics usually have long half-lives and for high-dose indications such as oncology, high level of drug will be present in the testing samples and interfere with ADA and/or neutralization antibody (NAb) measurement. To overcome this drug interference, acid-dissociation-based sample pre-treatment such as Bead-Extraction and Acid Dissociation (BEAD) has been successfully applied. The main concern for these acid-dissociation-based methods, however, is that harsh acid treatment could denature positive control Abs as well as NAb species in testing samples. In addition, high amount of biotinylated drug is needed in order to have effective competition with high level of drug in the samples, which in turn requires expensive magnetic beads. And the whole process of magnetic beads handling is tedious if doing manually and often causes trouble during assay transfer. Here, we describe a novel method which we named as Precipitation, Acid Dissociation and Biotin-drug as Assay Drug (PABAD). This novel method will need only one step of acid dissociation, with much milder and shorter acid treatment to maximally preserve NAb activity. In addition, only a fraction of biotinylated-drug is needed and there is no need to use additional streptavidin (SA)-plate or SA-magnetic beads for extraction. Compared to a BEAD-based assay, PABAD demonstrates significantly improved recovery of acid-sensitive NAb positive controls (PCs) and similar recovery of acid-resistant NAb PCs.

Neutralization Activity of Anti-drug Antibodies Against a Biotherapeutic Can Be Predicted from a Comprehensive Pharmacokinetics, Pharmacodynamics, and Anti-drug Antibody Data Analysis

Historically, a neutralization antibody (NAb) assay is considered critical in immunogenicity assessment of biologic therapeutics, even with low anti-drug antibody (ADA) positive rates. In 2019, FDA new guidelines issued on immunogenicity testing acknowledged the possibility of using "a highly sensitive PD marker or an appropriately designed PK assay or both that generate data that inform clinical activity" to replace a NAb assay. In the current manuscript, we present data for PK, PD, and ADA assays which collectively succeed to replace the standalone NAb assay. The data include a total LC/MS-based PK assay, a serum neutralization antibody (SNA) assay that essentially measures pharmacodynamically functional PK and can detect NAb activity in the presence of 1:1 ratio of drug, and a highly drug-tolerant ADA assay. In addition, a model-based meta-analysis (MBMA) demonstrated that the ability of SNA assay to detect NAb at 1:1 ratio of drug is sensitive enough to monitor clinically meaningful efficacy change, which is 50% reduction of SNA titer. Our strategy of preparing a holistic data package discussed here may provide a roadmap to the community for alternatives in assaying neutralizing activity of ADA.

Strategies to develop highly drug-tolerant cell-based neutralizing antibody assay: neutralizing antidrug antibodies extraction and drug depletion

Aim: Drug interference poses great analytical challenges for cell-based neutralizing antidrug antibodies (NAb) assay. The work aimed to improve assay drug tolerance through biotin-drug extraction with acid dissociation method optimization and developing new approach. Results: The NAb extraction with biotin-drug extraction with acid dissociation approach has been optimized by reducing biotinylated drug leaching and improving NAb elution efficiency, resulting in drug tolerance of up to 160 μg/ml. To circumvent the low acid elution efficiency of NAb from drug, a novel drug depletion approach was developed, which combined acid dissociation and drug targeted crosslinked capture, achieved drug tolerance up to 400 μg/ml. At last, a strategy workflow for sample pretreatment approach selection and optimization was established for improving drug tolerance of NAb assay. Conclusion: We demonstrated that reduced biotinylated drug leaching and the high NAb elution efficiency was critical for improving assay drug tolerance. Drug depletion offers an alternative approach to overcome low NAb elution efficiency.

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.

Quantification of neutralizing anti-drug antibodies and their neutralizing capacity using competitive displacement and tandem mass spectrometry: Infliximab as proof of principle

Background

The development of anti-drug antibodies (ADA) in patients treated with therapeutic proteins can result in treatment failure. The clinically most relevant fraction of these antibodies are the neutralizing anti-drug antibodies (NAb) that block the pharmacological function of the drug. Consequently, the detection of NAb in plasma is a better predictor of loss of therapeutic response than increased levels of total anti-drug antibodies (ADA) test. Traditional assays to detect ADA and NAb have limited specificity, sensitivity and linear dynamic range.

Method

Here, we demonstrate for the first time the potential of a LC-MS/MS method to measure the concentration of NAb against therapeutic proteins in plasma as exemplified with infliximab (IFX). We designed a competitive screening assay in which the presence of NAb in patients plasma prevents the binding of stable isotopically labeled (SIL) mAb infliximab to TNF-α ligand fixed on a 96-well plate.

Results

After washing, eluting and digesting, the signal intensity of SIL IFX-derived signature peptides was inversely and strongly correlated with NAb concentration in the sample: R² ​= ​0.999. Evaluation data showed that the assay has a high specificity (100%) and a high sensitivity (94%) to predict NAb presence. Cross-validation against total ADA measured by a reference laboratory using radio immunoassay assay (RIA) for ADA provided a good correlation (r² ​= ​0.79).

Conclusion

We developed for the first time a robust and fast screening method on the basis of LC-MS/MS to determine the presence of NAb and its neutralizing capacity in plasma. The analyses of NAb can be combined with therapeutic mAb quantification. Furthermore, the quantification of the neutralizing capacity expressed as mAb mass equivalents opens the door to new personalized dosing strategies in patients with NAb.

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A novel method to quantify neutralizing antibodies and their neutralizing capacity is presented.

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Neutralizing antibodies to infliximab have been determined with liquid chromatography tandem-mass spectrometry.

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Signal of SIL infliximab showed a strong correlation (r² ​= ​0.999) to the concentration neutralizing antibodies in plasma.

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Method was highly specific (100%) and selective (94%) and was well correlated with radioimmunoassay (r² ​= ​0.79).