Recommendations for the design, optimization, and qualification of cell-based assays used for the detection of neutralizing antibody responses elicited to biological therapeutics

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.

A competitive ligand binding assay for detection of neutralizing antibodies against an insulin analog

Biotherapeutics have the potential to trigger undesired immune responses in the patients. For therapeutic proteins, immunogenicity is manifested as anti-drug antibodies (ADA). Because ADA could compromise pharmacokinetics, efficacy, and safety, regulatory agencies require immunogenicity assessment during clinical development. A tiered bioanalytical approach is recommended to monitor clinical immunogenicity, and neutralizing antibodies (NAb) are studied in Tier 4 if the molecule is immunogenic. Although cell-based assays, which reflect the pharmacological mechanism of action, are in some cases the preferred assay format for detecting NAbs, they are associated with operational complexity and sometimes suboptimal assay performance. Alternatively, non-cell-based assays have also been developed and implemented. In our current study, a competitive ligand binding assay (CLBA) was developed to detect NAbs for insulin efsitora alfa (efsitora, basal insulin Fc, LY3209590), a novel fusion protein being studied for the treatment of Type 1 diabetes and Type 2 diabetes. The CLBA demonstrated acceptable sensitivity, drug tolerance, precision, and robustness, and thus provides a suitable approach for detecting NAbs against efsitora.

An Antibody-Dependent Cellular Cytotoxicity Assay for Detecting Ocrelizumab Neutralizing Antibody

Ocrelizumab (OCREVUS®) is a humanized anti-CD20 monoclonal antibody approved for the treatment of adult patients with relapsing multiple sclerosis (RMS) and primary progressive multiple sclerosis (PPMS). Here, we discuss the strategic and technical considerations needed to develop a robust antibody-dependent cellular cytotoxicity (ADCC)-based neutralizing antibody (NAb) assay to detect anti-ocrelizumab NAb in patients enrolled in the ocrelizumab registered clinical trials. The NAb detection assay consisted of a two-tier assay that included a screening assay and a confirmation assay. In the screening assay, patient samples were analyzed in the presence of ocrelizumab. Samples that tested positive in the screening assay were subsequently analyzed in the confirmatory assay where another anti-CD20 mAb, obinutuzumab, was replaced by ocrelizumab, to verify NAb specificity. Both assays utilized MEC-2 cells, a chronic B cell leukemia cell line, pre-labeled with calcein AM as the target cells, and natural killer (NK) cells engineered to stably express Fc gamma receptor IIIa_ F158 as effector cells. Both cell lines were prepared to be thaw-and-use cells. The NAb assay measures fluorescence from the calcein AM released into the assay media upon the lysis of target cells by ADCC in the presence of ocrelizumab or obinutuzumab. Our validated NAb assay showed a relative sensitivity of 743 ng/mL and can detect 1500 ng/mL of a surrogate positive control antibody in the presence of 1500 ng/mL ocrelizumab. This ADCC assay is the first reported NAb assay that directly measures target cell lysis by using thaw-and-use target and effector cells simultaneously.

Neutralizing Antibody Validation Testing and Reporting Harmonization

Evolving immunogenicity assay performance expectations and a lack of harmonized neutralizing antibody validation testing and reporting tools have resulted in significant time spent by health authorities and sponsors on resolving filing queries. A team of experts within the American Association of Pharmaceutical Scientists' Therapeutic Product Immunogenicity Community across industry and the Food and Drug Administration addressed challenges unique to cell-based and non-cell-based neutralizing antibody assays. Harmonization of validation expectations and data reporting will facilitate filings to health authorities and are described in this manuscript. This team provides validation testing and reporting strategies and tools for the following assessments: (1) format selection; (2) cut point; (3) assay acceptance criteria; (4) control precision; (5) sensitivity including positive control selection and performance tracking; (6) negative control selection; (7) selectivity/specificity including matrix interference, hemolysis, lipemia, bilirubin, concomitant medications, and structurally similar analytes; (8) drug tolerance; (9) target tolerance; (10) sample stability; and (11) assay robustness.

Assay development considerations to improve drug tolerance in direct competitive ligand binding neutralizing antibody assays, pretreatment strategies

Neutralizing anti-drug antibodies (ADAs) may affect safety, efficacy, and pharmacokinetic profile of a biotherapeutic drug and thus their assessment is of particular importance during immunogenicity testing. Neutralizing antibody (NAb) assays typically rely on NAbs ability to block the drug-target interaction. Higher NAb concentration and/or higher binding affinity of NAb to the drug, lowers the drug-target binding interaction. However, in the presence of high concentrations of residual circulating drug, as often seen for drugs with longer half-lives or in repeat-dose studies, NAbs may exist as drug bound complexes. In direct NAb assay formats, the NAb-drug complexes present in the sample could result in the NAb being unable to block the drug-target interaction eventually leading to a false negative response. The residual free circulating drug present in the sample may bind to the target in the NAb assay thereby competing with the drug used in the assay and inhibiting the assay signal, leading to a false positive response. For traditional ADA assays, multiple approaches involving acid treatment have been described to mitigate circulating drug interference issue. Here, we report two acid-treatment approaches that utilize the Dynabeads extraction with acid dissociation and Affinity Capture Elution (ACE) principle to improve drug tolerance in NAb assays.

Implementation of Systematic Bioanalysis of Antibody–Drug Conjugates for Preclinical Pharmacokinetic Study of Ado-Trastuzumab Emtansine (T-DM1) in Rats

Antibody–drug conjugates (ADCs) are composed of monoclonal antibodies covalently bound to cytotoxic drugs by a linker. They are designed to selectively bind target antigens and present a promising cancer treatment without the debilitating side effects of conventional chemotherapies. Ado-trastuzumab emtansine (T-DM1) is an ADC that received US FDA approval for the treatment of HER2-positive breast cancer. The purpose of this study was to optimize methods for the quantification of T-DM1 in rats. We optimized four analytical methods: (1) an enzyme-linked immunosorbent assay (ELISA) to quantify the total trastuzumab levels in all drug-to-antibody ratios (DARs), including DAR 0; (2) an ELISA to quantify the conjugated trastuzumab levels in all DARs except DAR 0; (3) an LC–MS/MS analysis to quantify the levels of released DM1; and (4) a bridging ELISA to quantify the level of anti-drug antibodies (ADAs) of T-DM1. We analyzed serum and plasma samples from rats injected intravenously with T-DM1 (20 mg/kg, single dose) using these optimized methods. Based on these applied analytical methods, we evaluated the quantification, pharmacokinetics, and immunogenicity of T-DM1. This study establishes the systematic bioanalysis of ADCs with validated assays, including drug stability in matrix and ADA assay, for future investigation on the efficacy and safety of ADC development.

Immunogenicity assessment of AAV-based gene therapies: An IQ consortium industry white paper

Immunogenicity has imposed a challenge to efficacy and safety evaluation of adeno-associated virus (AAV) vector-based gene therapies. Mild to severe adverse events observed in clinical development have been implicated with host immune responses against AAV gene therapies, resulting in comprehensive evaluation of immunogenicity during nonclinical and clinical studies mandated by health authorities. Immunogenicity of AAV gene therapies is complex due to the number of risk factors associated with product components and pre-existing immunity in human subjects. Different clinical mitigation strategies have been employed to alleviate treatment-induced or -boosted immunogenicity in order to achieve desired efficacy, reduce toxicity, or treat more patients who are seropositive to AAV vectors. In this review, the immunogenicity risk assessment, manifestation of immunogenicity and its impact in nonclinical and clinical studies, and various clinical mitigation strategies are summarized. Last, we present bioanalytical strategies, methodologies, and assay validation applied to appropriately monitor immunogenicity in AAV gene therapy-treated subjects.

Anti-drug antibodies in the current management of cancer

Monoclonal antibodies (mAbs) have become one of the main therapeutic weapons in modern oncology, mainly as targeted therapies, and immune checkpoint inhibitors. The generation of anti-drug antibodies (ADAs) after their administration can alter their pharmacokinetic, pharmacodynamic, efficacy and safety profile causing infusion-related reactions. Several risk factors have been associated with ADAs development, notably host genetics and immune status, comorbidity, concomitant medications, mAbs molecular structure, dose and route of administration. ADAs are not usually tested on daily clinical practice, being their analysis generally placed in early stages of drug development. ELISA-type assay the most common method. ADAs detection can involve important implications for treatment strategies of cancer patients, guiding therapeutic adjustment. In oncology, some studies about ADAs synthesis related to targeted therapies and immune checkpoint inhibitors have been recently published. Several strategies are proposed to reduce mAbs immunogenicity, such as different schedules, routes of administration or even the use of immunosuppressants. Another question that arises in relation to ADAs generation is the need to measure the concentration levels of active drug to guide the administration schedule. In this review, we will discuss all the aspects that are currently under discussion in relation with ADAs in oncology.

Allelic Variation in HLA-DRB1 is Associated with Development ofAnti-Drug Antibodies in Cancer Patients Treated with Atezolizumab that are Neutralizing in Vitro

The treatment of diseases with biologic agents can result in the formation of anti-drug antibodies (ADA). Although drivers for ADA formation are unknown, a role for antigen presentation is likely, and variation in human leukocyte antigen (HLA) genes has been shown to be associated with occurrence of ADA for several biologics. Here, we performed an HLA-wide association study in 1,982 patients treated with the anti-PD-L1 antibody atezolizumab across 8 clinical trials. On average, 29.8% of patients were ADA positive (N=591, range of 13.5% - 38.4% per study), and 14.6% of patients were positive for ADA that were neutralizing in vitro (NAb, N=278, range of 6.4% - 21.9% per study). In a meta-analysis of logistic regression coefficients, we found statistically significant associations between HLA class II alleles and ADA status. The top-associated alleles were HLA-DRB1*01:01 in a comparison of ADA-positive versus ADA-negative patients (p=3.4*10^-5 , odds ratio=1.96, 95% confidence interval=1.64-2.28), and HLA-DQA1*01:01 when comparing NAb-positive with ADA-negative patients (p=2.8 x 10^-7 , OR=2.31, 95% CI=1.98-2.66). Both alleles occur together on a common HLA haplotype, and analyses considering only NAb-negative, ADA-positive patients did no yield significant results, suggesting that the genetic association is mainly driven by NAb status. In conclusion, our study showed that HLA class II genotype is associated with the risk of developing ADA, and specifically NAb, in patients treated with atezolizumab, but the effect estimates suggest that immunogenetic factors are not sufficient as clinically meaningful predictors.

A comparative multi-tiered immunogenicity assessment of biosimilar pegylated filgrastim: validation of methods for clinical assessment of INTP5

BACKGROUND AND OBJECTIVE

Validated and highly sensitive assays are required for comparative assessment of immunogenicity of biosimilars. For INTP5, a biosimilar pegylated filgrastim, the immunogenicity assessment included tiers that allowed for assessment of antibodies against the PEG and the Filgrastim moieties for comparative clinical immunogenicity assessment.

METHODS

Electrochemiluminescence immunoassay (ECLIA) was used for Screening, Specificity, and Titer assays for detecting anti-drug antibodies (ADAs) and cell-based method for neutralizing ADAs. The methods were validated to enable use of same methods irrespective of biosimilar or reference arms.

RESULTS

The ADA and cell-based assay for neutralizing antibody detection were validated with a sensitivity capable of detecting binding Anti-Pegfilgrastim antibody at ~40 ng/mL and Neutralizing antibody at ~380 ng/mL and used for a comparative immunogenicity study. Of 194 subjects, 10 subjects had confirmed positive anti-drug-antibody in the biosimilar arm and 9 in the reference arm. None of the subjects were detected with neutralizing anti-drug antibodies.

CONCLUSION

This work demonstrates the application of a rigorous approach toward validation of assays for immunogenicity studies for biosimilars. Highly sensitive, precise, and robust assays were used to conclude comparable low incidences of anti-drug antibodies in both biosimilar and innovator arms of the clinical study for Pegfilgrastim.

Evaluation of atezolizumab immunogenicity: Efficacy and safety (Part 2)

Antibody therapeutics can be associated with unwanted immune responses resulting in the development of anti‐drug antibodies (ADA). Optimal methods to evaluate the potential effects of ADA on clinical outcomes in oncology are not well established. In this study, we assessed efficacy and safety, based on ADA status, in patients from over 10 clinical trials that evaluated the immune checkpoint inhibitor atezolizumab as a single agent or as combination therapy for several types of advanced cancers. ADA can only be observed post randomization, and imbalances in baseline prognostic factors can confound the interpretation of ADA impact. We applied methodology to account for the confounding effects of baseline clinical characteristics and survivorship bias on efficacy. Adjusted meta‐analyses revealed that despite numerical differences in overall survival and progression‐free survival between ADA‐positive and ADA‐negative patients from some studies, ADA‐positive patients from studies with an overall treatment effect derived benefit from atezolizumab, compared with their adjusted controls. Based on large, pooled populations from atezolizumab monotherapy or combination studies, unadjusted descriptive analyses did not identify a clear relationship between ADA status and frequency or severity of adverse events. Data also suggested that any ADA impact is not driven by neutralizing activity. Collectively, this exploratory analysis suggests that the potential for ADA development should not impact treatment decisions with atezolizumab.

Evaluation of atezolizumab immunogenicity: Clinical pharmacology (part 1)

Baseline patient characteristics and prognostic factors are important considerations in oncology when evaluating the impact of immunogenicity on pharmacokinetics (PK) and efficacy. Here, we assessed the impact of anti-drug antibodies (ADA) on the PK of the immune checkpoint inhibitor atezolizumab (an anti-PD-L1 monoclonal antibody). We evaluated data from ≈ 4500 patients from 12 clinical trials across different tumor types, treatment settings, and dosing regimens. In our dataset, ~ 30% of patients (range, 13-54%) developed treatment-emergent ADA, and in vitro neutralizing antibodies (NAb) were seen in ~ 50% of ADA-positive (+) patients. Pooled time course data showed a trend toward lower atezolizumab exposure in ADA+ patients, which was more pronounced in ADA+/NAb+ patients. However, the atezolizumab concentration distributions overlapped, and drug concentrations exceeded 6 µg/ml, the target concentration required for receptor saturation, in greater than 95% of patients. Patients had sufficient exposure regardless of ADA status. The dose selected to allow for dosing over effects from ADA resulted in a flat exposure-response relationship. Analysis of study results by ADA titer showed that exposure and overall survival were not affected in a clinically meaningful way. High tumor burden, low albumin, and high CRP at baseline showed the greatest association with ADA development but not with subsequent NAb development. These imbalanced factors at baseline can confound analysis of ADA impact. ADA increases atezolizumab clearance minimally (9%), and its impact on exposure based on the totality of the clinical pharmacology assessment does not appear to be clinically meaningful.

Flow cytometry and receptor occupancy in immune-oncology

Introduction: Immunotherapies are focused on strategies that alter immune responses, using antibodies that binds to receptors on different immune cell subsets and either activate or suppress their functions depending on the immune response being targeted. Hence, the necessity of developing assays that assess the functional and biological effect of a therapeutic on its target. When incorporated into high-parameter flow cytometry panels, receptor occupancy assay can simultaneously evaluate receptor expression and drug occupancy on defined cell subsets, which can provide information related to functional effects, and safety.Areas covered: This review focuses on the importance of developing, optimizing, and validating a robust Receptor Occupancy Assay (ROA) to improve dose selection, pharmacology monitoring and safety mainly in clinical settings.Expert opinion: The designing of an ROA can be challenging and can lead to exaggerated pharmacology if not accurately developed, optimized, and validated. However, improvements in our understanding of epitopes, binding, affinities, and pharmacological effects may lead to improved antibody drug targeting and receptor evaluation.

Statistical methods of screening cut point determination in immunogenicity studies

Background: Currently, screening cut point (CP) calculated from an assay validation with replicates are applied to an immunogenicity study with nonreplicates, for which the antidrug antibodies rate is determined. IID treats the replicate of a sample as coming from another independent sample. AVE uses average results from each sample across runs but inter-assay variability is reduced. Therefore, we propose a random effect model (REM) for calculating CP. Materials & method: We investigate impact of noncompatibility design between validation and immunogenicity studies on CP and compare these methods. Conclusion: IID may not fit for use when replicates' variability dominates all sources of uncertainty. REM considers covariance structure of repeated measurements. CP by REM is smaller than that by IID but larger than that by AVE.

The Molecular Mechanisms That Underlie the Immune Biology of Anti-drug Antibody Formation Following Treatment With Monoclonal Antibodies

Monoclonal antibodies (mAbs) are a crucial asset for human health and modern medicine, however, the repeated administration of mAbs can be highly immunogenic. Drug immunogenicity manifests in the generation of anti-drug antibodies (ADAs), and some mAbs show immunogenicity in up to 70% of patients. ADAs can alter a drug's pharmacokinetic and pharmacodynamic properties, reducing drug efficacy. In more severe cases, ADAs can neutralize the drug's therapeutic effects or cause severe adverse events to the patient. While some contributing factors to ADA formation are known, the molecular mechanisms of how therapeutic mAbs elicit ADAs are not completely clear. Accurate ADA detection is necessary to provide clinicians with sufficient information for patient monitoring and clinical intervention. However, ADA assays present unique challenges because both the analyte and antigen are antibodies, so most assays are cumbersome, costly, time consuming, and lack standardization. This review will discuss aspects related to ADA formation following mAb drug administration. First, we will provide an overview of the prevalence of ADA formation and the available diagnostic tools for their detection. Next, we will review studies that support possible molecular mechanisms causing the formation of ADA. Finally, we will summarize recent approaches used to decrease the propensity of mAbs to induce ADAs.

T-Cell Dependent Immunogenicity of Protein Therapeutics Pre-clinical Assessment and Mitigation-Updated Consensus and Review 2020

Immune responses to protein and peptide drugs can alter or reduce their efficacy and may be associated with adverse effects. While anti-drug antibodies (ADA) are a standard clinical measure of protein therapeutic immunogenicity, T cell epitopes in the primary sequences of these drugs are the key drivers or modulators of ADA response, depending on the type of T cell response that is stimulated (e.g., T helper or Regulatory T cells, respectively). In a previous publication on T cell-dependent immunogenicity of biotherapeutics, we addressed mitigation efforts such as identifying and reducing the presence of T cell epitopes or T cell response to protein therapeutics prior to further development of the protein therapeutic for clinical use. Over the past 5 years, greater insight into the role of regulatory T cell epitopes and the conservation of T cell epitopes with self (beyond germline) has improved the preclinical assessment of immunogenic potential. In addition, impurities contained in therapeutic drug formulations such as host cell proteins have also attracted attention and become the focus of novel risk assessment methods. Target effects have come into focus, given the emergence of protein and peptide drugs that target immune receptors in immuno-oncology applications. Lastly, new modalities are entering the clinic, leading to the need to revise certain aspects of the preclinical immunogenicity assessment pathway. In addition to drugs that have multiple antibody-derived domains or non-antibody scaffolds, therapeutic drugs may now be introduced via viral vectors, cell-based constructs, or nucleic acid based therapeutics that may, in addition to delivering drug, also prime the immune system, driving immune response to the delivery vehicle as well as the encoded therapeutic, adding to the complexity of assessing immunogenicity risk. While it is challenging to keep pace with emerging methods for the preclinical assessment of protein therapeutics and new biologic therapeutic modalities, this collective compendium provides a guide to current best practices and new concepts in the field.

Implementation of a three-tiered approach to identify and characterize anti-drug antibodies raised against HIV-specific broadly neutralizing antibodies

The ability to detect, quantify, and interrogate the properties of immune responses raised against biological therapeutics is not only important to our understanding of these molecules, but also to their success in the clinic. A tiered assay approach to identify the presence, specificity, and titer of anti-drug antibody (ADA) responses has been adopted as a gold standard by industry leaders, the FDA, and the EMA. In order to support pre-clinical and clinical trials, these assays must be standardized, and their performance sufficiently characterized to ensure the accuracy and reproducibility of results under relevant testing conditions. Here we present implementation of electrochemiluminiscence assays that fit into the tiered paradigm of ADA testing for five HIV broadly neutralizing antibodies (3BNC117, 3BNC117-LS, 10–1074, PGT121, and PGDM1400) in compliance with Good Clinical Laboratory practices. Assay sensitivities and matrix effects were evaluated and used to inform the development of positivity cut points. Once cut points were established, assay precision, specificity, free-drug tolerance, and robustness were defined. In all cases, assay characteristics met or surpassed recommendations set forth by the FDA. To further evaluate the performance of these assays and the tiered approach, samples from non-human primates that had received a subset of the five therapeutics were evaluated. In sum, this study reports qualification of a set of ADA assays available to the scientific community as pre-clinical and clinical trials of broadly HIV-neutralizing antibodies proceed, and a framework that is easily adapted as new drug products are advanced in the clinic.

Optimization and qualification of a functional anti-drug antibody assay for HIV-1 bnAbs

The recent identification of human monoclonal antibodies with broad and potent neutralizing activity against HIV-1 (bnAbs) has resulted in substantial efforts to develop these molecules for clinical use in the prevention and treatment of HIV-1 infection. As with any protein therapeutic drug product, it is imperative to have qualified assays that can accurately detect and quantify anti-drug antibodies (ADA) that may develop in patients receiving passive administration of HIV-1 bnAbs. Here, we have optimized and qualified a functional assay to assess the potential of ADA to inhibit the neutralizing function of HIV-1 bnAbs. Using a modified version of the validated TZM-bl HIV-1 neutralization assay, murine anti-idiotype antibodies were utilized to optimize and evaluate parameters of linearity, range, limit of detection, specificity, and precision for measuring inhibitory ADA activity against multiple HIV-1 bnAbs that are in clinical development. We further demonstrate the utility of this assay for detecting naturally occurring ADA responses in non-human primates receiving passive administration of human bnAbs. This functional assay format complements binding-antibody ADA strategies being developed for HIV-1 bnAbs, and when utilized together, will support a multi-tiered approach for ADA testing that is compliant with Good Clinical Laboratory Practice (GCLP) procedures and FDA guidance.

Approaches to improve drug tolerance and target tolerance in the assessment of neutralizing anti-drug antibodies

Aim: Neutralizing anti-drug antibody (NAb) assays are inherently prone to the interference from drug and its soluble target, potentially resulting in erroneous results. An effective approach to improve drug tolerance of an NAb assay is pretreatment of samples with acid to dissociate immune complexes of NAb and drug, followed by separating NAbs from circulating drug before testing them in the assay. Methods and Results: The acid pretreatment conditions were optimized to improve drug tolerance of cell-based and non-cell-based NAb assays. NAbs were further separated from circulating drug either through direct drug removal or purification of NAb from the sample. In addition, an integrated experimental strategy was implemented to simultaneously improve drug and its soluble target tolerance for reliable NAb assessment. Conclusion: The approaches described herein would enable the development of reliable NAb assays that overcome drug and its target interference for more precise and sensitive NAb assessment.

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).

High-Throughput Process Development for Biopharmaceuticals

The ability to conduct multiple experiments in parallel significantly reduces the time that it takes to develop a manufacturing process for a biopharmaceutical. This is particularly significant before clinical entry, because process development and manufacturing are on the "critical path" for a drug candidate to enter clinical development. High-throughput process development (HTPD) methodologies can be similarly impactful during late-stage development, both for developing the final commercial process as well as for process characterization and scale-down validation activities that form a key component of the licensure filing package. This review examines the current state of the art for HTPD methodologies as they apply to cell culture, downstream purification, and analytical techniques. In addition, we provide a vision of how HTPD activities across all of these spaces can integrate to create a rapid process development engine that can accelerate biopharmaceutical drug development. Graphical Abstract.

Immunogenicity of Innovative and Biosimilar Monoclonal Antibodies

The development of hybridoma technology for producing monoclonal antibodies (mAbs) by Kohler and Milstein (1975) counts as one of the major medical breakthroughs, opening up endless possibilities for research, diagnosis and for treatment of a whole variety of diseases. Therapeutic mAbs were introduced three decades ago. The first generation of therapeutic mAbs of murine origin showed high immunogenicity, which limited efficacy and was associated with severe infusion reactions. Subsequently chimeric, humanized, and fully human antibodies were introduced as therapeutics, these mAbs were considerably less immunogenic. Unexpectedly humanized mAbs generally show similar immunogenicity as chimeric antibodies; based on sequence homology chimeric mAbs are sometimes more “human” than humanized mAbs. With the introduction of the regulatory concept of similar biological medicines (biosimilars) a key concern is the similarity in terms of immunogenicity of these biosimilars with their originators. This review focuses briefly on the mechanisms of induction of immunogenicity by biopharmaceuticals, mAbs in particular, in relation to the target of the immune system.

Detection of Antibodies That Neutralize the Cellular Uptake of Enzyme Replacement Therapies with a Cell-based Assay

The administration of enzyme replacement therapies (ERTs) and other biologic therapies to patients may elicit an anti-drug immune response. The characterization of these anti-drug antibodies (ADA), especially those that may neutralize the biological activity of the drug, termed neutralizing antibodies (NAbs), is crucial in understanding the effects of these antibodies on the drug's pharmacological profile. This protocol describes a cell-based flow cytometry method to detect factors that neutralize the cellular uptake of a representative lysosomal ERT in human matrix. The protocol consists of three procedures: screening, a confirmatory step, and titer assays to detect, identify, and establish the relative level of neutralizing antibody titer in subject samples.

In this method, samples are first mixed with the fluorophore-conjugated ERT product, then incubated with cells [e.g., human T lymphocytes (Jurkat cells)] that express a cell-surface cation-independent mannose 6-phosphate receptor (CI-M6PR), and finally, analyzed with a flow cytometer. A sample without NAbs will result in the uptake of the fluorophore-conjugated ERT product via CI-M6PR, whereas, the presence of NAbs will bind to the drug and interfere with the CI-M6PR binding and uptake. The amount of the fluorophore-conjugated ERT internalized by the Jurkat cells is measured by flow cytometry and evaluated as the percentage (%) signal inhibition compared to the response obtained in the presence of a representative drug-naïve matrix. In the confirmatory step, the samples are pre-incubated with ERT-conjugated magnetic beads to deplete drug-specific factors that bind to the drug (such as NAbs) prior to an incubation with cells. Samples that screen and confirm positive for drug-specific NAbs in the assay are then serially diluted to generate an antibody titer. Semi-quantitative antibody titers may be correlated with measurements of drug safety and efficacy.

Bead-extraction and heat-dissociation (BEHD): A novel way to overcome drug and matrix interference in immunogenicity testing

Biological therapeutics are foreign antigens and can potentially induce immune response resulting in the formation of anti-drug antibodies (ADA), which in turn may lead to a wide range of side effects. Neutralizing Ab (NAb) is a subset of ADA that can bind to the pharmacological activity regions of therapeutic to inhibit or complete neutralize its clinical efficacy. A cell-based functional NAb assay is preferred to characterize its neutralization activity. However, cell-based NAb assays are often vulnerable to drug interference, as well as interference from numerous serum factors, including but not limited to growth factors and disease-related cytokines. Bead Extraction with Acid Dissociation (BEAD) has been successfully applied to remove circulating drug and/or other interfering factors from human serum samples, thereby enriching for ADA/NAb. However, the harsh acid used in the extraction procedure can cause irreversible denaturing of NAb and lead to underestimated NAb measurement. Herein we describe a new approach when acid-dissociation is not optimal for a PEGylated domain antibody (Ab). We further demonstrate that heating at 62 °C can not only dissociate drug/ADA/NAb immune complex but also selectively and irreversibly denature domain Ab drug due to much lower thermal stability of the domain Ab, when compared to that of full antibodies. The irreversible denaturing of the drug favors the formation of an immune complex between ADA/NAb and the added biotinylated drug thus increasing the recovery of ADA/NAb from samples. We call this new procedure Bead Extraction with Heat Dissociation (BEHD), which can potentially be applied to other NAb assays that have poor compatibility with acid dissociation.

Immunogenicity assessment of tbo-filgrastim in cancer patients receiving chemotherapy

AIM

This integrated analysis examined the immunogenicity of tbo-filgrastim and its potential clinical impact in three Phase III randomized studies in patients with breast cancer, lung cancer and non-Hodgkin lymphoma receiving chemotherapy.

RESULTS

Treatment-emergent antidrug antibodies (ADA) occurred in 3/213 (1.4%) breast cancer patients, 2/160 (1.3%) lung cancer patients and 1/63 (1.6%) patients with non-Hodgkin lymphoma. None of the treatment-emergent ADA showed cross-reactivity toward native granulocyte-colony stimulating factors or exhibited neutralizing activity against tbo-filgrastim. Among patients with treatment-emergent ADA, there was no treatment-related hypersensitivity or anaphylaxis and no evidence of loss of clinical efficacy.

CONCLUSION

Tbo-filgrastim has demonstrated low immunogenicity in cancer patients receiving chemotherapy and ADA response does not impact safety and efficacy in the patients.

Immunogenicity of branched polyethylene glycol modified interferon alpha

AIM

To assess the immunogenicity of Peginterferon alpha-2 b(Pegberon) and its effect on the efficacy and safety in phase III clinical trial, by comparing it with the control drug Pegasys.

METHODS

770 patients were recruited in total. 509 were treated with Pegberon plus ribavirin and 261 were treated with Pegasys plus ribavirin. After treatment of 12 and 24 weeks, plasma samples were collected from individual patients for detecting the anti-therapeutic antibodies (ATA) and hepatitis C RNA(HCV RNA), to evaluate the production of antibodies and their adverse effect on the efficacy and safety of the treatments. With data obtained from the treatments with Pegberon or Pegasys, gross comparison analysis was performed.

RESULTS

The incidence of treatment-induced neutralizing antibodies (NAb) of Pegberon group (0.7%, 3/454) was significantly lower than Pegasys group (5.0%,12/238)(p < .001). Among all patients, the rates of sustained virological response 24 (SVR24) were significantly different between baseline ATA positive (60.7%,34/56) and baseline ATA negative patients (76.2%,544/714)(p = .010), between baseline NAb positive (36.0%,9/25) and baseline NAb negative patients (76.4%,569/745)(p < .001) and between induced ATA positive (72.7%,40/55) and sustained ATA negative patients(84.0%,492/586)(p = .034). The incidence of potential immunogenicity-related adverse reactions (AR) showed no significant difference between Pegberon (55.6%,283/509) and Pegasys groups (53.6%,140/261)(p = .605) and the profiles of these AR were also similar between the two groups.

CONCLUSION

The incidence of treatment-induced Nab in Pegasys group was significantly higher than the Pegberon group. Baseline ATA, induced ATA and baseline NAb all affected the efficacy. The profiles of potential immunogenicity-related AR were similar between two drug groups, indicating the immunogenicity had no significant adverse effect on safety.

Development and validation of a cell based assay for the detection of neutralizing antibodies against recombinant insulins

Recombinant biopharmaceuticals can induce generation of anti-drug antibodies, which could potentially neutralize therapeutic drug activity. In this report, we describe development and validation of a cell-based assay for detection of neutralizing antibodies (Nab) against insulin and insulin analogues. In order to achieve clinically meaningful sensitivity the method used an early signalling event, insulin induced insulin receptor phosphorylation as the endpoint. Percentage insulin receptor phosphorylation in cell lysates was measured using ECL based ELISA. Presence of neutralizing antibodies (Nab) in samples will inhibit insulin induced receptor phosphorylation and consequently lead to a reduction in the percentage of phosphorylated insulin receptor. Additionally, usage of human insulin receptor overexpressing recombinant CHO cell line further improved the assay sensitivity by reducing the fixed drug (EC50) concentration used for induction of receptor phosphorylation. To ensure adequate free drug tolerance a pre-treatment step was introduced, where serum samples underwent acid dissociation and charcoal extraction before drug incubation. In order to distinguish ADA positive samples containing true Nab from samples containing non-antibody phosphorylation inhibitory serum factors, a confirmatory tier was integrated based on immunodepletion using protein AGL mix. Assay parameters including determination of screening and confirmatory cut-points, intra and inter assay precision, selectivity, specificity and stability were assessed during validation in accordance with recent regulatory guidelines and white papers. The advantage of selecting insulin receptor phosphorylation as assay endpoint made the assay capable of detecting Nab against insulin and insulin analogues.

Advancements in Understanding Immunogenicity of Biotherapeutics in the Intraocular Space

Therapeutic breakthroughs in a number of retinal degenerative diseases have come about through the development of biotherapeutics administered directly into the eye. As a consequence of their use, we have gained more insight into the immune privileged status of the eye and the various considerations that development, manufacturing, and use of these drugs require. It has been observed that therapeutic proteins injected into the vitreous can elicit an immune response resulting in the production of anti-drug antibodies (ADAs) which can have clinical consequences. This review includes discussion of the anatomy, physiology, and specific area of the eye that are targeted for drug administration. The various immunologic mechanisms involved in the immune responses to intraocularly administered protein are discussed. This review entails discussion on chemistry, manufacturing, and control (CMC) and formulation-related issues that may influence the risk of immunogenicity. Based on the available immunogenicity profile of the marketed intraocular drugs and their reported adverse events, the animal models and the translational gap from animals to human are discussed. Thus, the objective of this review article is to assess the factors that influence immunogenicity in relation to intraocular administration and the steps taken for mitigating immunogenicity risks.

Development and Validation of an Enzyme-Linked Immunosorbent Assay for the Detection of Binding Anti-Drug Antibodies against Interferon Beta

Objective

To develop and validate a method for the detection of binding anti-drug antibodies (ADAs) against interferon beta (IFN-β) in human serum as part of a European initiative (ABIRISK) aimed at the prediction and analysis of clinical relevance of anti-biopharmaceutical immunization to minimize the risk.

Method

A two-tiered bridging enzyme-linked immunosorbent assay (ELISA) format was selected and validated according to current recommendations. Screening assay: ADA in serum samples form complexes with immobilized IFN-β and biotinylated IFN-β, which are then detected using HRP labeled Streptavidin and TMB substrate. Confirmation assay: Screen “putative positive” samples are tested in the presence of excess drug (preincubation of sera with 0.3 µg/mL of soluble IFN-β) and percentage of inhibition is calculated.

Results

The assay is precise, and the sensitivity of the assay was confirmed to be 26 ng/mL using commercially available polyclonal rabbit antihuman IFN-β in human sera as the positive control.

Conclusion

An ultrasensitive ELISA for IFN-β-binding ADA testing has been validated. This will form the basis to assess anti-biopharmaceutical immunization toward IFN-β with regards to its clinical relevance and may allow for the development of predictive tools, key aims within the ABIRISK consortium.

Assessing the Immunogenicity of Biopharmaceuticals

Biopharmaceuticals have the potential to raise an immunogenic response in treated individuals, which may impact the efficacy and safety profile of these drugs. As a result, it is essential to evaluate immunogenicity throughout the different phases of the clinical development of a biopharmaceutical, including post-marketing surveillance. Although rigorous evaluation of biopharmaceutical immunogenicity is required by regulatory authorities, there is a lack of uniform standards for the type, quantity, and quality of evidence, and for guidance on experimental design for immunogenicity assays or criteria to compare immunogenicity of biopharmaceuticals. Moreover, substantial technological advances in methods to assess immune responses have yielded higher immunogenicity rates with modern assays, and limit comparison of immunogenicity of biopharmaceuticals outside of head-to-head clinical trials. Accordingly, research programs, regulatory agencies, and clinicians need to keep pace with continuously evolving analyses of immunogenicity. Here, we review factors associated with immunogenicity of biopharmaceuticals, potential clinical ramifications, and current regulatory guidance for evaluating immunogenicity, and discuss methods to assess immunogenicity in non-clinical and clinical studies. We also describe special considerations for evaluating the immunogenicity of biosimilar candidates.

Antibodies that neutralize cellular uptake of elosulfase alfa are not associated with reduced efficacy or pharmacodynamic effect in individuals with Morquio A syndrome

Many enzyme replacement therapies (ERTs) for lysosomal storage disorders use the cell-surface cation-independent mannose-6 phosphate receptor (CI-M6PR) to deliver ERTs to the lysosome. However, neutralizing antibodies (NAb) may interfere with this process. We previously reported that most individuals with Morquio A who received elosulfase alfa in the phase 3 MOR-004 trial tested positive for NAbs capable of interfering with binding to CI-M6PR ectodomain in an ELISA-based assay. However, no correlation was detected between NAb occurrence and clinical efficacy or pharmacodynamics. To quantify and better characterize the impact of NAbs, we developed a functional cell-based flow cytometry assay with a titer step that detects antibodies capable of interfering with elosulfase alfa uptake. Serum samples collected during the MOR-004 trial were tested and titers were determined. Consistent with earlier findings on NAb positivity, no correlations were observed between NAb titers and the clinical outcomes of elosulfase alfa-treated individuals with Morquio A.

An innovative and highly drug-tolerant approach for detecting neutralizing antibodies directed to therapeutic antibodies

Aim: Immunogenicity testing of biotherapeutic drugs is a regulatory requirement. Herein, we describe a drug-tolerant assay for detecting neutralizing antibodies against a therapeutic antibody. Results: Excess target of the therapeutic antibody was incorporated into the detection step of an affinity capture elution assay. Signal generated from binding of antidrug antibody (ADA) to the therapeutic antibody was compared with signal from binding of ADA to the therapeutic antibody preincubated with its target. The results demonstrated that the target blocked binding of the therapeutic antibody to neutralizing monkey ADA and to two anti-idiotypic antibodies. Conclusion: This highly drug-tolerant novel approach enables the detection of neutralizing antibodies and allows for one basic assay format to achieve complete characterization of ADA responses.

Best practice recommendations for the transfer of cell-based assays for the measurement of neutralizing anti-drug antibodies

We recommend the application of a strategically designed step-wise approach to transfer cell-based assays that includes assessing analytical performance (through a fit for purpose validation and/or design of experiment robustness characterization), clinical performance (i.e., concordance) and performance or proficiency testing for long-term method monitoring. Here we focus on the application of this strategy to cell-based assays for the measurement of neutralizing anti-drug antibodies. This application is unique in that it requires a custom cell-based assay to be used over a long period of time (potentially phase 1a through the life of a marketed product) with the confidence of consistent method performance and result reporting. But, the process is adaptable to a variety of assay types and applications. We present lessons learned from two cell-based assay transfers that met relevant challenges while implementing alternative permutations of the recommended method transfer process.

Treatment with recombinant human bone morphogenetic protein 7 leads to a transient induction of neutralizing autoantibodies in a subset of patients

Background

Recombinant human bone morphogenetic protein 7 (rhBMP7) is applied for treatment of bone fractures, especially tibial non-unions. Its application may induce autoantibodies (aAB) affecting the targeted and endogenous signaling pathways and in turn negatively impact treatment efficacy.

Methods

Novel and sensitive assays for the quantification of BMP7-aAB and BMP2-aAB were established and used to analyze serum samples from healthy controls (n = 100 men, n = 100 women) and patients with long bone fracture (n = 265) treated or not with rhBMP7. Sera from three to nine time points per patient were available and enabled the evaluation of aAB over a time course of up to one year. Functional activity of the BMP-aAB was tested with a BMP-responsive cell-based reporter assay. Consolidation of the fracture was evaluated as clinical outcome potentially affected by BMP7-aAB.

Results

Prevalence of BMP7-aAB and BMP2-aAB was 1–2.5% in non-treated patients or healthy controls. The rhBMP7 treatment induced a transient increase in BMP7-aAB in a subset of patients, returning to non-detectable levels within six months. IgG from BMP7-aAB positive sera inhibited dose dependently the BMP7-reporter gene activity, whereas control sera were without effect. Successful consolidation of the fracture was observed in the majority of both aAB-positive and aAB-negative patients.

General significance

We conclude that BMP7-aAB can be detected as natural aAB in healthy subjects, and are transiently induced by rhBMP7 therapy in a subset of patients. The aAB are capable of antagonizing BMP7 signaling in vitro, but do not preclude treatment success in patients.

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There are patients with natural autoantibodies recognizing BMP7.

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In some patients, rhBMP7-therapy induces BMP7 autoantibodies.

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BMP7 autoantibodies elicit neutralizing effects on BMP signaling.

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Therapy-induced BMP7 autoantibodies disappear over time.

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BMP7 autoantibodies seem not to affect therapy success.

Optimizing Treatment with TNF Inhibitors in Inflammatory Bowel Disease by Monitoring Drug Levels and Antidrug Antibodies

BACKGROUND

Biological tumor necrosis factor (TNF) inhibitors have revolutionized the treatment of inflammatory bowel disease and redefined treatment goals to include mucosal healing. Clinicians are faced with challenges such as inadequate responses, treatment failures, side effects, and high drug costs. The objective is to review optimization of anti-TNF therapy by use of personalized treatment strategies based on circulating drug levels and antidrug antibodies (Abs), i.e. therapeutic drug monitoring (TDM). Furthermore, to outline TDM-related pitfalls and their prevention.

METHODS

Literature review.

RESULTS

Circulating anti-TNF drug trough level is a marker for the pharmacokinetics (PK) of TNF inhibitors. Because of a number of factors, including antidrug antibodies, PK varies between and within patients across time leading to variable clinical outcomes. Differences in intestinal inflammatory phenotype influencing the pharmacodynamic (PD) responses to TNF inhibitors also affect treatment outcomes. As an alternative to handling anti-TNF-treated patients by empiric strategies, TDM identifies underlying PK and PD-related reasons for treatment failure and aids decision making to secure optimal clinical and economic outcomes. Although promising, evidence does not the support use of TDM to counteract treatment failure in quiescent disease. Use of TDM is challenged by methodological biases, difficulties related to differentiation between PK and PD problems, and temporal biases due to lack of chronology between changes in PK versus symptomatic and objective disease activity manifestations. Biases can be accommodated by knowledgeable interpretation of results obtained by validated assays with clinically established thresholds, and by repeated assessments over time using complimentary techniques.

CONCLUSIONS

TDM-guided anti-TNF therapy at treatment failure has been brought from bench to bedside.

Determination of Anti-Adeno-Associated Viral Vector Neutralizing Antibodies in Patients With Heart Failure in the Cardiovascular Foundation of Colombia (ANVIAS): Study Protocol

Background

Recent progress in the pathophysiology of heart failure (HF) has led to the development of new therapeutic options such as gene therapy and the use of adeno-associated viral (AAV) vectors. Despite the promising results in early clinical trials of gene therapy for HF, various obstacles have been faced, such as the presence of neutralizing antibodies (NAbs) against the capsid vectors. NAb activity limits vector transduction levels and therefore diminishes the final therapeutic response. Recent studies evaluating the prevalence of NAbs in various populations found considerable geographic variability for each AAV serotype. However, the levels of NAbs in Latin American populations are unknown, becoming a limiting factor to conducting AAV vector therapeutic trials in this population.

Objective

The goal of this study is to determine for the first time, the prevalence of anti-AAV NAbs for the serotypes 1, 2, and 9 in HF patients from the city of Bucaramanga, Colombia, using the in vitro transduction inhibition assay.

Methods

We will conduct a cross-sectional study with patients who periodically attend the HF clinic of the Cardiovascular Foundation of Colombia and healthy volunteers matched for age and sex. For all participants, we will evaluate the NAb levels against serotypes AAV1, AAV2, and AAV9. We will determine NAb levels using the in vitro transduction inhibition assay. In addition, participants will answer a survey to evaluate their epidemiological and socioeconomic variables. Participation in the study will be voluntary and all participants will sign an informed consent document before any intervention.

Results

The project is in the first phase: elaboration of case report forms and the informed consent form, and design of the recruitment strategy. Patient recruitment is expected to begin in the spring of 2016. We expect to have preliminary results, including the titer of the viral vectors, multiplicity of infections that we will use for each serotype, and the general validation of the assay, at the end of 2016. The final results are expected mid-2017.

Conclusions

This project is the first effort to evaluate NAb levels against AAV1, AAV2, and AAV9 serotypes in patients with HF in Latin America. Our results will allow us to check the cross-reactivity response between the serotypes assessed, to describe the epidemiological characteristics of the participant population, and to set up a link with earlier reports of NAb prevalence in the literature.

Immunogenicity screening assay development for a novel human-mouse chimeric anti-CD147 monoclonal antibody (Metuzumab)

The clinical effect of patient immune responses to therapeutic antibodies affect product safety and efficacy, which makes the development of valid, sensitive immune assays a key aspect of antibody drug development. In this paper, we reported the generations of mouse monoclonal and Cynomolgus monkey polyclonal antibodies against the anti-CD147 antibody (Metuzumab) as the internal standards and the positive controls. Seven mouse monoclonal antibodies were shown to recognize both (Fab)2 and full length of Metuzumab, but not the control normal human IgGs, and monoclonal anti-Metuzumab, Clone 2D9 was chosen to be used as the internal standard for anti-Metuzumab study. A Bridging ELISA assay was developed by coating the wells with the antibody drug, and the anti-drug antibody (ADA) in the animal sera were detected by enzyme-labeled antibody. Its limit of detection (LOD) was determined to be 0.39ng/ml of anti-Metuzumab antibody (ADA) with linear range between 0.39-50ng/ml and R(2)=0.994. For normal monkey sera, a minimal dilution was determined to be 1:80. However, very different from peptide or other protein drugs, strong interferences from the residual antibody drugs were observed from most of the testing monkey sera in the preclinical study. It was experimentally determined that the concentration of the residual antibody drug in the assay have to be lower than 1μg/ml, so the assays were carried out at 1:100 dilution of the monkey sera. In the pre-clinical study, 32 monkeys were treated with escalating doses of Metuzumab between 0, 10, 50, 200mg/kg for 13 times over 13weeks of time period. 16 of them were terminated right after the last injection, while the other 16 were rested for additional 4weeks before termination. Afraid to miss any positive response to antibody drug, sera samples were collected at six time points, including 2-, 6- and 10-weeks post 1st dose, prior to last dose, and 2-, 4-weeks into recovery. The highest positive rates were seen with the Medium- and High-dose group 2-weeks post the first injection, 6 out 8 monkeys in the High-dose were positive for free ADA. However, no significant pathologic and clinic adversary effect was observed in those monkeys.

Development of Immunocapture-LC/MS Assay for Simultaneous ADA Isotyping and Semiquantitation

Therapeutic proteins and peptides have potential to elicit immune responses resulting in anti-drug antibodies that can pose problems for both patient safety and product efficacy. During drug development immunogenicity is usually examined by risk-based approach along with specific strategies for developing “fit-for-purpose” bioanalytical approaches. Enzyme-linked immunosorbent assays and electrochemiluminescence immunoassays are the most widely used platform for ADA detection due to their high sensitivity and throughput. During the past decade, LC/MS has emerged as a promising technology for quantitation of biotherapeutics and protein biomarkers in biological matrices, mainly owing to its high specificity, selectivity, multiplexing, and wide dynamic range. In fully taking these advantages, we describe here an immunocapture-LC/MS methodology for simultaneous isotyping and semiquantitation of ADA in human plasma. Briefly, ADA and/or drug-ADA complex is captured by biotinylated drug or anti-drug Ab, immobilized on streptavidin magnetic beads, and separated from human plasma by a magnet. ADA is then released from the beads and subjected to trypsin digestion followed by LC/MS detection of specific universal peptides for each ADA isotype. The LC/MS data are analyzed using cut-point and calibration curve. The proof-of-concept of this methodology is demonstrated by detecting preexisting ADA in human plasma.

Determination of anti-adeno-associated virus vector neutralizing antibody titer with an in vitro reporter system

Adeno-associated virus (AAV) vectors are a platform of choice for in vivo gene transfer applications. However, neutralizing antibodies (NAb) to AAV can be found in humans and some animal species as a result of exposure to the wild-type virus, and high-titer NAb develop following AAV vector administration. In some conditions, anti-AAV NAb can block transduction with AAV vectors even when present at low titers, thus requiring prescreening before vector administration. Here we describe an improved in vitro, cell-based assay for the determination of NAb titer in serum or plasma samples. The assay is easy to setup and sensitive and, depending on the purpose, can be validated to support clinical development of gene therapy products based on AAV vectors.

Development and validation of cell-based luciferase reporter gene assays for measuring neutralizing anti-drug antibodies against interferon beta

Neutralizing anti-drug antibodies (NAbs) against therapeutic interferon beta (IFNβ) in people with multiple sclerosis (MS) are measured with cell-based bioassays. The aim of this study was to redevelop and validate two luciferase reporter-gene bioassays, LUC and iLite, using a cut-point approach to identify NAb positive samples. Such an approach is favored by the pharmaceutical industry and governmental regulatory agencies as it has a clear statistical basis and overcomes the limitations of the current assays based on the Kawade principle. The work was conducted following the latest assay guidelines. The assays were re-developed and validated as part of the "Anti-Biopharmaceutical Immunization: Prediction and analysis of clinical relevance to minimize the risk" (ABIRISK) consortium and involved a joint collaboration between four academic laboratories and two pharmaceutical companies. The LUC assay was validated at Innsbruck Medical University (LUCIMU) and at Rigshospitalet (LUCRH) Copenhagen, and the iLite assay at Karolinska Institutet, Stockholm. For both assays, the optimal serum sample concentration in relation to sensitivity and recovery was 2.5% (v/v) in assay media. A Shapiro-Wilk test indicated a normal distribution for the majority of runs, allowing a parametric approach for cut-point calculation to be used, where NAb positive samples could be identified with 95% confidence. An analysis of means and variances indicated that a floating cut-point should be used for all assays. The assays demonstrated acceptable sensitivity for being cell-based assays, with a confirmed limit of detection in neat serum of 1519 ng/mL for LUCIMU, 814 ng/mL for LUCRH, and 320 ng/mL for iLite. Use of the validated cut-point assay, in comparison with the previously used Kawade method, identified 14% more NAb positive samples. In conclusion, implementation of the cut-point design resulted in increased sensitivity to detect NAbs. However, the clinical significance of these low positive titers needs to be further evaluated.

Design and Implementation of High-Throughput Screening Assays

HTS remains at the core of the drug discovery process, and so it is critical to design and implement HTS assays in a comprehensive fashion involving scientists from the disciplines of biology, chemistry, engineering, and informatics. This requires careful consideration of many options and variables, starting with the choice of screening strategy and ending with the discovery of lead compounds. At every step in this process, there are decisions to be made that can greatly impact the outcome of the HTS effort, to the point of making it a success or a failure. Although specific guidelines should be established to ensure that the screening assay reaches an acceptable level of quality, many choices require pragmatism and the ability to compromise opposing forces.