Analysis of regulatory guidance on antidrug antibody testing for therapeutic protein products.

Therapeutic proteins have the potential to induce unwanted immune responses. The potential impact of immunogenicity on pharmacokinetics, pharmacodynamics, safety and efficacy are well established. Here, we analyze key aspects of current US FDA and EMA guidelines on the development and validation of antidrug antibody assays. Although FDA and EMA guidance documents are in harmony on most points, EMA allows greater leeway for scientific judgement, while FDA recommends specific approaches that may not be appropriate in some situations. Many white papers suggest approaches different from the guidance documents, however, these can conflict with each other and are themselves only scientifically valid in certain situations. Here, we indicate when alternatives to guidance may be needed and what those approaches might be.

Current challenges in assessing immunogenicity.

Biography Gopi Shankar is a Vice President at Janssen BioTherapeutics, the biotechnology discovery and development unit of Janssen Research & Development, LLC (one of the Pharmaceutical Companies of Johnson & Johnson). His department of approximately 150 scientists is responsible for characterizing biophysical and pharmacological parameters of biologic molecules for discovery and for developing preclinical projects through first-in-human trials by determining pharmacokinetics, toxicokinetics, target pharmacodynamics, starting dose and projected efficacious dose recommendations. The department also provides analytical and bioanalytical results for Janssen's clinical trials of biologics. Throughout his entire career, Dr Shankar has focused on the development of innovative solutions to scientific hurdles, developed consensus and harmonized scientific practices. A renowned expert in the field of immunogenicity and a Fellow of the American Association of Pharmaceutical Scientists (AAPS), Dr Shankar has led or contributed to several highly impactful scientific advances in immunogenicity; his research, consensus-building efforts and best-practice publications have transformed the thinking and tactical processes related to clinical immunogenicity.

A generic method for the detection of polyethylene glycol specific IgG and IgM antibodies in human serum.

Detection of anti-drug antibodies is a critical step in the development of large molecule biopharmaceuticals. In the case of multicomponent/multifunctional molecules, such as fusion proteins and protein conjugates such as covalent polyethylene glycol (PEG)~protein conjugates, it is useful to further characterize anti-drug antibody (ADA) binding to key domains of the drug. The detection of anti-PEG antibodies poses special challenges that if overlooked can result in underreporting antibody responses. Here we describe the development and characterization of a novel ELISA to detect anti-PEG antibodies that provides a more complete interpretation of anti-PEG than other published methods. Being specific to the PEG moiety alone, this method is intended to detect anti-PEG antibodies independent of the protein to which PEG is conjugated. Based upon early indications that our assay could detect anti-PEG antibodies at a surprisingly high frequency in the general population, our emphasis throughout method development and validation was to ensure that non-specific signals and unintended interactions were not falsely contributing to detection of anti-PEG antibodies. Techniques, including orthogonal methods used to ensure that this ELISA detected antibodies specific to PEG included competition, immunodepletion, immunoprecipitation/western blot and an Octet kinetic binding analysis. The validated ELISA can detect 100 ng/mL of an anti-PEG IgG positive control and 800 ng/mL of an anti-PEG IgM positive control in the presence of 7.5 µg/mL of the PEGylated therapeutic (MW 64 kDa). The intra-assay percent co-efficient of variation (CV) and inter-assay CV of the low positive control samples in the screening method were 4.1 to 7.2% and 16.7 to 17.7%, respectively. Additional assay performance parameters that were validated are also described. When the validated assay was applied to a population of 200 healthy blood donors with no known exposure to biopharmaceutical PEG conjugates it indicated a pre-existing anti-PEG antibody prevalence of 97.5%. We suggest this surprising result is a consequence of exposure to PEG additives in everyday products, such as cosmetics, processed foods and over-the-counter (OTC) pharmaceuticals.

Immunogenicity of Golimumab and its Clinical Relevance in Patients With Ulcerative Colitis.

BACKGROUND: Antidrug antibody (ADA) detection with standard bridging enzyme immunoassays (EIA) can yield false-negative results or underestimate titers through drug interference. A more sensitive assay was needed to determine clinical impact of antigolimumab antibodies. METHODS: A high-sensitivity, drug-tolerant EIA (DT-EIA) was developed and cross-validated against the original EIA, and samples from induction/maintenance studies in golimumab-treated patients with ulcerative colitis were analyzed for ADAs using both methods. Immunogenicity results were compared, and pharmacokinetic, efficacy, and safety associations were evaluated. RESULTS: An 8-fold increase in ADA-positive patients (21.8% DT-EIA vs 2.8% EIA) reflected DT-EIA improved sensitivity and drug tolerance. Most newly detected ADA-positive patients (using DT-EIA) had low antibody titers, whereas most with high antibody titers were ADA-positive with original EIA. With DT-EIA, week 44 median trough serum golimumab concentrations among ADA-positive patients were approximately half vs ADA-negative (0.51 vs 0.85 µg/mL [50 mg q4w]; 0.85 vs 1.60 µg/mL [100 mg q4w]). Antidrug antibody impact on golimumab concentrations was more notable at titers ≥1:100. During induction, ADAs had no notable impact on efficacy. During maintenance, proportions of patients maintaining clinical response through week 54 were lower using DT-EIA: 38.1% ADA-positive and 52.8% ADA-negative. Antidrug antibody status had no impact on injection-site reaction incidence. CONCLUSIONS: A more sensitive DT-EIA identified higher proportions of ADA-positive patients. A trend of decreasing drug concentrations with increasing ADA titers was observed. Pharmacokinetic impact was better elucidated with DT-EIA. Although development of ADA did not preclude efficacy, a trend toward decreased efficacy in ADA-positive vs ADA-negative patients was observed during maintenance treatment. Antidrug antibody status did not impact safety.

Immunogenicity of golimumab and its clinical relevance in patients with rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis.

OBJECTIVE: Golimumab immunogenicity was extensively studied during clinical development. As anti-drug antibody (ADA) detection with the standard bridging EIA (original-EIA) can yield false-negative results or underestimate ADA incidence and titres due to drug interference, a more sensitive assay was needed to determine clinical impact. METHODS: A highly sensitive drug-tolerant EIA (DT-EIA) was developed and cross-validated against the original-EIA. Samples from phase-3 subcutaneous golimumab rheumatological trials (GO-FORWARD-rheumatoid arthritis, GO-REVEAL-psoriatic arthritis, GO-RAISE-ankylosing spondylitis) were then retested. Associations between ADAs and golimumab pharmacokinetics, efficacy and safety were assessed. RESULTS: The DT-EIA was more sensitive than the original-EIA and capable of detecting ADAs amid golimumab concentrations far exceeding those in immunogenicity test samples. Consequently, an 8-fold increase in the incidence of ADAs was observed with the DT-EIA (31.7%) vs original-EIA (4.1%) in the studies. Most ADA-positive patients identified by the DT-EIA had lower antibody titres, while most with higher titres were previously identified as ADA-positive by the original-EIA. With the DT-EIA, ADA-positive patients generally had lower trough serum golimumab concentrations than ADA-negative patients; however, ADA impact on serum golimumab concentrations was more notable at higher ADA titres (⩾100). No impact of ADAs on clinical efficacy or injection-site reactions was evident. CONCLUSION: ADA incidence was expectedly higher using the DT-EIA vs original-EIA; newly detected ADAs were characterized mostly by low titres, with no impact on clinical efficacy or injection-site reactions, consistent with previously observed original-EIA results. Golimumab immunogenicity with the DT-EIA is consistent with existing knowledge regarding the clinical relevance of ADAs detected with the original-EIA in patients with rheumatological disorders. TRIAL REGISTRATION: NCT00264550, NCT00265096, NCT00265083.

Implementing a tiered approach to bioanalytical method validation for large-molecule ligand-binding assay methods in pharmacokinetic assessments.

Bioanalytical methods must enable the delivery of data that meet sound, scientifically justified, fit-for-purpose criteria. At early phases of biotherapeutic drug development, suitable criteria of a ligand-binding assay could be met for pharmacokinetic (PK) in-study sample testing without a full validation defined by regulatory guidelines. To ensure fit-for-purpose methods support PK testing through all phases of biotherapeutic development, three tiers of method validation - regulatory, scientific and research validations - are proposed. The three-tiered framework for method validation outlines the differences in the parameters that should be assessed, the acceptance criteria that may be applied, and the documentation necessary at each level. The criteria for selecting the appropriate application of each of these PK method validation workflows are discussed.

Comparisons of Serum Infliximab and Antibodies-to-Infliximab Tests Used in Inflammatory Bowel Disease Clinical Trials of Remicade®.

Monitoring infliximab (IFX) concentrations and antibodies-to-IFX (ATI) titers during inflammatory bowel disease treatment may allow more informed decisions in assessing exposure/response and determining appropriate dosing. To aid in interpreting results from different commercial tests in the context of Janssen's published Remicade® results, the reliability of Janssen's IFX and ATI assays was compared with commercial assays from KU Leuven, Sanquin, Dynacare, and LabCorp. Test results were independently reported to Janssen. All assays were tested for specificity, selectivity, and precision. ATI assays were evaluated for sensitivity, drug interference, and potential interference of tumor necrosis factor-alpha (TNF-α). IFX assays were specific, accurate, and reproducible. Intra-class correlation of Janssen IFX assay results with those from KU Leuven, Sanquin, Dynacare, and LabCorp were 0.960, 0.895, 0.931, and 0.971, respectively. ATI titers >10 interfered with IFX assessment in all IFX assays, whereas TNF-α (≤50 ng/mL) did not interfere with IFX detection in any assay. ATI assays specifically and reproducibly detected ATI. Janssen, Sanquin, and LabCorp ATI methods were more resistant to IFX interference than Dynacare and KU Leuven, which were affected by IFX concentrations at ≥2 µg/mL. TNF-α (<5 ng/mL) did not interfere with ATI detection. Strong agreement was observed between Janssen's IFX and ATI assays and the diagnostic service provider assays. Our study results indicate that all four commercially available assays are suitable for therapeutic drug monitoring of IFX. The substantial agreement reported here between the comparator assays and the Janssen drug-tolerant assay provides support to clinicians in their use of these commercial assays, and for understanding their patients' IFX and ATI results relative to published data from clinical studies of Remicade.

Pharmacokinetics and immunogenicity investigation of a human anti-interleukin-17 monoclonal antibody in non-naïve cynomolgus monkeys.

The pharmacokinetics (PK) of biologic therapeutics, especially monoclonal antibodies (mAbs), in monkeys generally presents the most relevant predictive PK information for humans. However, human mAbs, xenogeneic proteins to monkeys, are likely to be immunogenic. Monkeys previously treated with a human mAb (non-naïve) may have developed antidrug antibodies (ADAs) that cross-react with another test mAb in subsequent studies. Unlike PK studies for small-molecule therapeutics, in which animals may be reused, naïve monkeys have been used almost exclusively for preclinical PK studies of biologic therapeutics to avoid potential pre-existing immunologic cross-reactivity issues. The propensity and extent of pre-existing ADAs have not been systematically investigated to date. In this study, the PK and immunogenicity of mAb A, a human anti-human interkeukin-17 mAb, were investigated in a colony of 31 cynomolgus monkeys previously exposed to other human mAbs against different targets. We screened the monkeys for pre-existing antibodies to mAb A prior to the PK study and showed that 44% of the monkeys had pre-existing cross-reactive antibodies to mAb A, which could affect the PK characterization of the antibody. In the subcolony of monkeys without measurable pre-existing ADAs, PK and immunogenicity of mAb A were successfully characterized. The impact of ADAs on mAb A PK was also demonstrated in the monkeys with pre-existing ADAs. Here we report the results and propose a pragmatic approach for the use of non-naïve monkeys when conducting PK studies of biologic therapeutics.

The challenge of indication extrapolation for infliximab biosimilars.

A biosimilar is intended to be highly similar to a reference biologic such that any differences in quality attributes (i.e., molecular characteristics) do not affect safety or efficacy. Achieving this benchmark for biologics, especially large glycoproteins such as monoclonal antibodies, is challenging given their complex structure and manufacturing. Regulatory guidance on biosimilars issued by the U.S. Food and Drug Administration, Health Canada and European Medicines Agency indicates that, in addition to a demonstration of a high degree of similarity in quality attributes, a reduced number of nonclinical and clinical comparative studies can be sufficient for approval. Following a tiered approach, clinical studies are required to address concerns about possible clinically significant differences that remain after laboratory and nonclinical evaluations. Consequently, a critical question arises: can clinical studies that satisfy concerns regarding safety and efficacy in one condition support "indication extrapolation" to other conditions? This question will be addressed by reviewing the case of a biosimilar to infliximab that was approved recently in South Korea, Europe, and Canada for multiple indications through extrapolation. The principles discussed should also apply to biosimilars of other monoclonal antibodies that are approved to treat multiple distinct conditions.

Development of a method that eliminates false-positive results due to nerve growth factor interference in the assessment of fulranumab immunogenicity.

Fulranumab, a human IgG2 monoclonal antibody that neutralizes nerve growth factor (NGF), is currently in development for the treatment of pain. Our initial immunogenicity test method was found to be prone to NGF interference, leading to a high apparent incidence of anti-drug antibody (ADA) in phase 1 studies. The ADA immunoassay comprised a homogeneous bridging electrochemiluminescence (ECL) format with biotin and ruthenium-labeled fulranumab bound together ("bridged") by ADA in test samples for detection. In this assay, NGF produced a false-positive signal due to its ability to bridge fulranumab molecules. Thus, we developed a specificity assay to eliminate the NGF false-positive results. We encountered the challenge of eliminating drug interference as well as drug target interference, and discovered that the acid-dissociation-based pretreatment of samples used for mitigating drug interference dramatically increased drug target interference. Several strategies were investigated to eliminate the NGF interference; yet only one strategy specifically removed NGF and produced true fulranumab-specific ADA results by using competitive inhibition with fulranumab and utilizing an alternative NGF binding antibody to eliminate NGF interference. Using this new method, we confirmed that the high apparent anti-fulranumab antibody incidence (>60%) in clinical study samples was in fact due to fulranumab-bound NGF released during the acid-dissociation step of the ADA testing method. We conclude that our revised method accurately identifies anti-fulranumab antibodies by incorporating steps to eliminate fulranumab and NGF interference. We advise that acid-dissociation pretreatment must not be universally applied to improve ADA assays without investigating its bioanalytical risks versus benefits.

Characterization of critical reagents in ligand-binding assays: enabling robust bioanalytical methods and lifecycle management.

The effective management of validated ligand-binding assays used for PK, PD and immunogenicity assessments of biotherapeutics is vital to ensuring robust and consistent assay performance throughout the lifetime of the method. The structural integrity and functional quality of critical reagents is often linked to ligand-binding assay performance; therefore, physicochemical and biophysical characterization coupled with assessment of assay performance can enable the highest degree of reagent quality. The implementation of a systematic characterization process for monitoring critical reagent attributes, utilizing detailed analytical techniques such as LC-MS, can expedite assay troubleshooting and identify deleterious trends. In addition, this minimizes the potential for costly delays in drug development due to reagent instability or batch-to-batch variability. This article provides our perspectives on a proactive critical reagent QC process. Case studies highlight the analytical techniques used to identify chemical and molecular factors and the interdependencies that can contribute to protein heterogeneity and integrity.

Therapeutic targeting of the IL-12/23 pathways: generation and characterization of ustekinumab.

Preclinical and clinical studies conducted in the mid-1990s reported strong association and causality between the T-cell helper (T(H)) 1 inductor cytokine interleukin (IL)-12 and numerous immune-mediated disorders, which spurred the development of therapeutic agents targeting IL-12 function. One of the first to enter the clinic, ustekinumab, is a human monoclonal antibody (mAb) that binds to the p40 subunit of IL-12. Subsequent to the generation of ustekinumab, it was discovered that IL-23 also contains the p40 subunit. Thus, although ustekinumab was designed to target IL-12, it also modulates IL-23, a cytokine important to the development and/or maintenance of T(H)17 cells. Clinical observations established that IL-12/23p40 is integral to the pathologies of psoriasis, psoriatic arthritis and Crohn's disease. The molecular and cellular evaluations conducted in ustekinumab clinical programs have provided numerous insights into the pathologic processes of these disorders, illustrating how a novel molecular entity can contribute to our understanding of disease. The individual contributions of these cytokines to specific pathologies require investigation and clinical evaluation of the role of IL-12- and IL-23-specific inhibitors.

Detection of low-affinity anti-drug antibodies and improved drug tolerance in immunogenicity testing by Octet(®) biolayer interferometry.

We assessed the utility of the FortéBio Octet(®) system for detection of anti-drug antibodies (ADAs) against an investigational therapeutic human IgG1 monoclonal antibody (mAb), CNTO X. To understand the relative merits of this technology, key performance requirements were compared with two popularly accepted ADA detection methods, a step-wise bridging ELISA and a Meso Scale Discovery (MSD) homogeneous (single step binding) bridging ECLIA. When used to detect 13 monoclonal ADAs of varying affinities and one polyclonal ADA, all three methods demonstrated their greatest apparent sensitivity to the polyclonal sample (1, 6, and 130 ng/mL, respectively for ECLIA, ELISA, and Octet). Sensitivity to monoclonal ADAs tended to vary in accordance with their affinities, however, the sensitivity of the Octet method varied much less between ADAs. As a result, the above ranking became reversed such that Octet was the most and ELISA least sensitive for detection of low-affinity ADAs. With regard to drug tolerance, the presence of CNTO X could lead to false-negative assay results, although each method was affected to a different degree, with the Octet method tolerating up to 10 times more drug than the ECLIA method, which in turn tolerated up to 10 times more than the ELISA. Finally, the ECLIA and Octet methods were applied to the bioanalysis of cynomolgus monkey sera from a pre-clinical multiple dose study of CNTO X. Octet indicated 3 positive animals developed ADA as early as day 15 of the dosing phase while drug was present at nearly 1mg/mL. ECLIA detected only one of these, and only in a day 57 recovery sample after drug had cleared from circulation. We conclude that the Octet is a promising platform for detection of lower affinity ADAs and is particularly suitable for ADA detection when drug persists at levels that negatively impact bridging immunoassays.

Lack of racial differences in the pharmacokinetics of subcutaneous golimumab in healthy Japanese and Caucasian male subjects.

This phase 1 study evaluated the single-dose pharmacokinetics and safety of subcutaneous golimumab, a human anti-tumor necrosis factor-alpha monoclonal antibody, in healthy Japanese and Caucasian subjects. Eligible subjects were males, aged 20 to 45 years, weighing 50 to 90 kg with a body mass index of 19 to 30 kg/m(2). Japanese and Caucasian subjects were matched by body weight and dose group. Blood samples were collected through day 50 following a single subcutaneous injection of golimumab 50 or 100 mg. The pharmacokinetic parameters were determined using a noncompartmental method. All 51 subjects (24 Japanese, 27 Caucasian) were included in the safety analysis; 47 completed the study and were included in the pharmacokinetic analysis. The pharmacokinetics of golimumab were comparable in both race groups. Peak concentrations were observed approximately 4 to 6 days after administration. No significant differences in exposure or mean half-life (range, 11-13 days) were observed between Japanese and Caucasian subjects at the same dose level. Regardless of race, serum golimumab exposure increased with increasing dose. Mean apparent clearance ranged from 12 to 19 mL/kg/d. Mean apparent volume of distribution (224-262 mL/kg) remained constant with an increase in dose. No antibodies to golimumab were detected. Single subcutaneous injections of golimumab 50 mg or 100 mg were generally well tolerated in these healthy male Japanese and Caucasian subjects.

Immunogenicity of biologically-derived therapeutics: assessment and interpretation of nonclinical safety studies.

An evaluation of potential antibody formation to biologic therapeutics during the course of nonclinical safety studies and its impact on the toxicity profile is expected under current regulatory guidance and is accepted standard practice. However, approaches for incorporating this information in the interpretation of nonclinical safety studies are not clearly established. Described here are the immunological basis of anti-drug antibody formation to biopharmaceuticals (immunogenicity) in laboratory animals, and approaches for generating and interpreting immunogenicity data from nonclinical safety studies of biotechnology-derived therapeutics to support their progression to clinical evaluation. We subscribe that immunogenicity testing strategies should be adapted to the specific needs of each therapeutic development program, and data generated from such analyses should be integrated with available clinical and anatomic pathology, pharmacokinetic, and pharmacodynamic data to properly interpret nonclinical studies.

Recommendations for the validation of immunoassays used for detection of host antibodies against biotechnology products.

Most biological drug products elicit some level of anti-drug antibody (ADA) response. This antibody response can, in some cases, lead to potentially serious side effects and/or loss of efficacy. In humans, ADA often causes no detectable clinical effects, but in the instances of some therapeutic proteins these antibodies have been shown to cause a variety of clinical consequences ranging from relatively mild to serious adverse events. In nonclinical (preclinical) studies, ADA can affect drug exposure, complicating the interpretation of the toxicity, pharmacokinetic (PK) and pharmacodynamic (PD) data. Therefore, the immunogenicity of therapeutic proteins is a concern for clinicians, manufacturers and regulatory agencies. In order to assess the immunogenic potential of biological drug molecules, and be able to correlate laboratory results with clinical events, it is important to develop reliable laboratory test methods that provide valid assessments of antibody responses in both nonclinical and clinical studies. For this, method validation is considered important, and is a necessary bioanalytical component of drug marketing authorization applications. Existing regulatory guidance documents dealing with the validation of methods address immunoassays in a limited manner, and in particular lack information on the validation of immunogenicity methods. Hence this article provides scientific recommendations for the validation of ADA immunoassays. Unique validation performance characteristics are addressed in addition to those provided in existing regulatory documents pertaining to bioanalyses. The authors recommend experimental and statistical approaches for the validation of immunoassay performance characteristics; these recommendations should be considered as examples of best practice and are intended to foster a more unified approach to antibody testing across the biopharmaceutical industry.

Recommendations on risk-based strategies for detection and characterization of antibodies against biotechnology products.

The appropriate evaluation of the immunogenicity of biopharmaceuticals is of major importance for their successful development and licensure. Antibodies elicited by these products in many cases cause no detectable clinical effects in humans. However, antibodies to some therapeutic proteins have been shown to cause a variety of clinical consequences ranging from relatively mild to serious adverse events. In addition, antibodies can affect drug efficacy. In non-clinical studies, anti-drug antibodies (ADA) can complicate interpretation of the toxicity, pharmacokinetic (PK) and pharmacodynamic (PD) data. Therefore, it is important to develop testing strategies that provide valid assessments of antibody responses in both non-clinical and clinical studies. This document provides recommendations for antibody testing strategies stemming from the experience of contributing authors. The recommendations are intended to foster a more unified approach to antibody testing across the biopharmaceutical industry. The strategies proposed are also expected to contribute to better understanding of antibody responses and to further advance immunogenicity evaluation.