Epitope characterization of pre-existing and developing antibodies to an aglycosylated monoclonal antibody therapeutic of G1m17,1 allotype

Living in LALA land? Forty years of attenuating Fc effector functions

The Fc region of antibodies is vital for most of their physiological functions, many of which are engaged through binding to a range of Fc receptors. However, these same interactions are not always helpful or wanted when therapeutic antibodies are directed against self-antigens, and can sometimes cause catastrophic adverse reactions. Over the past 40 years, there have been intensive efforts to "silence" unwanted binding to Fc-gamma receptors, resulting in at least 45 different variants which have entered clinical trials. One of the best known is "LALA" (L234A/L235A). However, neither this, nor most of the other variants in clinical use are completely silenced, and in addition, the biophysical properties of many of them are compromised. I review the development of different variants to see what we can learn from their biological properties and use in the clinic. With the rise of powerful new uses of antibody therapy such as bispecific T-cell engagers, antibody-drug conjugates, and checkpoint inhibitors, it is increasingly important to optimize the Fc region as well as the antibody binding site in order to achieve the best combination of safety and efficacy.

Beyond Allotypes: The Influence of Allelic Diversity in Antibody Constant Domains

Polymorphic diversity in antibody constant domains has long been defined by allotypic motifs that cross react with the sera of other individuals. Improvements in sequencing technologies have led to the discovery of a large number of new allelic sequences that underlie this diversity. Many of the point mutations lie outside traditional allotypic motifs suggesting they do not elicit immunogenic responses. As antibodies play an important role in immune defense and biotechnology, understanding how this newly resolved diversity influences the function of antibodies is important. This review investigates the current known diversity of antibody alleles at a protein level for each antibody isotype as well as the kappa and lambda light chains. We focus on evidence emerging for how these mutations perturb antibody interactions with antigens and Fc receptors that are critical for function, as well as the influence this might have on the use of antibodies as therapeutics and reagents.

Multiplexed immunoassay approach to characterize antidrug antibody like specific reactivity

Aim: Characterization of antidrug antibody (ADA)-like reactivity has emerged as critical element of bioanalytical design and assessment of compound immunogenicity risk. Materials & methods: Multiplex immunoassay was applied to detect and characterize ADA like reactivity using Photonic Ring Immunoassay platform (Genalyte). Specific binding to human IgE or human recombinant IL21-receptor-Fc fusion using exogenous reagents as surrogates for drug-specific reactivity was investigated. Results: Multiplexed assay format allowed identification of spiked antihuman IgE reactivity as murine IgG1 and endogenous antihuman recombinant IL21-receptor-Fc reactivity in rheumatoid arthritis sera as antihuman Fc-specific binding. Conclusion: The ability of a multiplex immunoassay platform to identify isotype and domain specificity of antidrug immunoglobulins was shown to be effective and should be considered when screening and characterizing pre- and post-dose ADA reactivity.

Bridging immunogenicity assays for IgG4 therapeutics: mitigating interference from Fc-Fc interactions

AIM

A bridging immunogenicity assay for a human IgG4 mAb therapeutic was transferred to an automation system to increase throughput. However, background signal increased five- to six-fold during the 6- to 8-h run.

RESULTS

Noncovalent Fc contacts formed between labeled IgG4 drugs in reagent solutions stored during the automation run. This generated substantial background signal, reducing assay sensitivity by approximately sixfold. Fc interactions also significantly impacted the confirmation assay. Fc contacts formed between labeled and unlabeled drug, significantly increasing signal inhibition (∼7-70%) in the 6-h run.

CONCLUSION

Storing labeled antibody solutions separately and combining them immediately before adding to samples reduced interference from Fc interactions. Preincubation time for reagent solutions should be strictly controlled for anti-drug antibody assays with IgG4 drugs to avoid false-positive results.

CCL20 neutralization by a monoclonal antibody in healthy subjects selectively inhibits recruitment of CCR6+ cells in an experimental suction blister

AIMS

GSK3050002, a humanized IgG1κ antibody with high binding affinity to human CCL20, was administered in a first-in-human study to evaluate safety, pharmacokinetics (PK) and pharmacodynamics (PD). An experimental skin suction blister model was employed to assess target engagement and the ability of the compound to inhibit recruitment of inflammatory CCR6 expressing cells.

METHODS

This study was a randomized, double-blind (sponsor open), placebo-controlled, single-centre, single ascending intravenous dose escalation trial in 48 healthy male volunteers.

RESULTS

GSK3050002 (0.1-20 mg kg^-1 ) was well tolerated and no safety concerns were identified. The PK was linear over the dose range, with a half-life of approximately 2 weeks. Complex of GSK3050002/CCL20 increased in serum and blister fluid with increasing doses of GSK3050002. There were dose-dependent decreases in CCR6⁺ cell recruitment to skin blisters with maximal effects at doses of 5 mg kg^-1 and higher, doses at which GSK3050002/CCL20 complex in serum and blister fluid also appeared to reach maximum levels.

CONCLUSIONS

These results indicate a relationship between PK, target engagement and PD, suggesting a selective inhibition of recruitment of CCR6⁺ cells by GSK3050002 and support further development of GSK3050002 in autoimmune and inflammatory diseases.

Evaluation of the immunogenicity of the dabigatran reversal agent idarucizumab during Phase I studies

Aims

Idarucizumab, a humanized monoclonal anti‐dabigatran antibody fragment, is effective in emergency reversal of dabigatran anticoagulation. Pre‐existing and treatment‐emergent anti‐idarucizumab antibodies (antidrug antibodies; ADA) may affect the safety and efficacy of idarucizumab. This analysis characterized the pre‐existing and treatment‐emergent ADA and assessed their impact on the pharmacokinetics and pharmacodynamics (PK/PD) of idarucizumab.

Methods

Data were pooled from three Phase I, randomized, double‐blind idarucizumab studies in healthy Caucasian subjects; elderly, renally impaired subjects; and healthy Japanese subjects. In plasma sampled before and after idarucizumab dosing, ADA were detected and titrated using a validated electrochemiluminescence method. ADA epitope specificities were examined using idarucizumab and two structurally related molecules. Idarucizumab PK/PD data were compared for subjects with and without pre‐existing ADA.

Results

Pre‐existing ADA were found in 33 out of 283 individuals (11.7%), seven of whom had intermittent ADA. Titres of pre‐existing and treatment‐emergent ADA were low, estimated equivalent to <0.3% of circulating idarucizumab after a 5 g dose. Pre‐existing ADA had no impact on dose‐normalized idarucizumab maximum plasma levels and exposure and, although data were limited, no impact on the reversal of dabigatran‐induced anticoagulation by idarucizumab. Treatment‐emergent ADA were detected in 20 individuals (19 out of 224 treated [8.5%]; 1 out of 59 received placebo [1.7%]) and were transient in ten. The majority had specificity primarily toward the C‐terminus of idarucizumab. There were no adverse events indicative of immunogenic reactions.

Conclusion

Pre‐existing and treatment‐emergent ADA were present at extremely low levels relative to the idarucizumab dosage under evaluation. The PK/PD of idarucizumab appeared to be unaffected by the presence of pre‐existing ADA.

Emerging Technologies and Generic Assays for the Detection of Anti-Drug Antibodies

Anti-drug antibodies induced by biologic therapeutics often impact drug pharmacokinetics, pharmacodynamics response, clinical efficacy, and patient safety. It is critical to assess the immunogenicity risk of potential biotherapeutics in producing neutralizing and nonneutralizing anti-drug antibodies, especially in clinical phases of drug development. Different assay methodologies have been used to detect all anti-drug antibodies, including ELISA, radioimmunoassay, surface plasmon resonance, and electrochemiluminescence-based technologies. The most commonly used method is a bridging assay, performed in an ELISA or on the Meso Scale Discovery platform. In this report, we aim to review the emerging new assay technologies that can complement or address challenges associated with the bridging assay format in screening and confirmation of ADAs. We also summarize generic anti-drug antibody assays that do not require drug-specific reagents for nonclinical studies. These generic assays significantly reduce assay development efforts and, therefore, shorten the assay readiness timeline.

Cross-reactive and pre-existing antibodies to therapeutic antibodies--Effects on treatment and immunogenicity

The potential for immunogenicity is an ever-present concern during the development of biopharmaceuticals. Therapeutic antibodies occasionally elicit an antibody response in patients, which can result in loss of response or adverse effects. However, antibodies that bind a drug are sometimes found in pre-treatment serum samples, with the amount depending on drug, assay, and patient population. This review summarizes published data on pre-existing antibodies to therapeutic antibodies, including rheumatoid factors, anti-allotype antibodies, anti-hinge antibodies, and anti-glycan antibodies. Unlike anti-idiotype antibodies elicited by the drug, pre-formed antibodies in general appear to have little consequences during treatment. In the few cases where (potential) clinical consequences were encountered, antibodies were characterized and found to bind a distinct, unusual epitope of the therapeutic. Immunogenicity testing strategies should therefore always include a proper level of antibody characterization, especially when pre-formed antibodies are present. This minimizes false-positives, particularly due to rheumatoid factors, and helps to judge the potential threat in case a genuine pre-dose antibody reactivity is identified.

Pre-existing Antibody: Biotherapeutic Modality-Based Review

Pre-existing antibodies to biotherapeutic drugs have been detected in drug-naïve subjects for a variety of biotherapeutic modalities. Pre-existing antibodies are immunoglobulins that are either specific or cross-reacting with a protein or glycan epitopes on a biotherapeutic compound. Although the exact cause for pre-existing antibodies is often unknown, environmental exposures to non-human proteins, glycans, and structurally similar products are frequently proposed as factors. Clinical consequences of the pre-existing antibodies vary from an adverse effect on patient safety to no impact at all and remain highly dependent on the biotherapeutic drug modality and therapeutic indication. As such, pre-existing antibodies are viewed as an immunogenicity risk factor requiring a careful evaluation. Herein, the relationships between biotherapeutic modalities to the nature, prevalence, and clinical consequences of pre-existing antibodies are reviewed. Initial evidence for pre-existing antibody is often identified during anti-drug antibody (ADA) assay development. Other interfering factors known to cause false ADA positive signal, including circulating multimeric drug target, rheumatoid factors, and heterophilic antibodies, are discussed.

Specificity of human anti-variable heavy (VH ) chain autoantibodies and impact on the design and clinical testing of a VH domain antibody antagonist of tumour necrosis factor-α receptor 1

During clinical trials of a tumour necrosis factor (TNF)-R1 domain antibody (dAb™) antagonist (GSK1995057), infusion reactions consistent with cytokine release were observed in healthy subjects with high levels of a novel, pre-existing human anti-VH (HAVH) autoantibody. In the presence of HAVH autoantibodies, GSK1995057 induced cytokine release in vitro due to binding of HAVH autoantibodies to a framework region of the dAb. The epitope on GSK1995057 was characterized and dAbs with reduced binding to HAVH autoantibodies were generated; pharmacological comparability was determined in human in-vitro systems and in-vivo animal experiments. A Phase I clinical trial was conducted to investigate the safety and tolerability of the modified dAb (GSK2862277). A significant reduction in HAVH binding was achieved by adding a single alanine residue at the C-terminus to create GSK2862277. Screening a pool of healthy donors demonstrated a reduced frequency of pre-existing autoantibodies from 51% to 7%; in all other respects, GSK2862277 and the parent dAb were comparable. In the Phase I trial, GSK2862277 was well tolerated by both the inhaled and intravenous routes. One subject experienced a mild infusion reaction with cytokine release following intravenous dosing. Subsequently, this subject was found to have high levels of a novel pre-existing antibody specific to the extended C-terminus of GSK2862277. Despite the reduced binding of GSK2862277 to pre-existing HAVH autoantibodies, adverse effects associated with the presence of a novel pre-existing antibody response specific to the modified dAb framework were identified and highlight the challenge of developing biological antagonists to this class of receptor.

Rheumatoid arthritis response to treatment across IgG1 allotype - anti-TNF incompatibility: a case-only study

Introduction

We have hypothesized that incompatibility between the G1m genotype of the patient and the G1m1 and G1m17 allotypes carried by infliximab (INX) and adalimumab (ADM) could decrease the efficacy of these anti-tumor necrosis factor (anti-TNF) antibodies in the treatment of rheumatoid arthritis (RA).

Methods

The G1m genotypes were analyzed in three collections of patients with RA totaling 1037 subjects. The first, used for discovery, comprised 215 Spanish patients. The second and third were successively used for replication. They included 429 British and Greek patients and 393 Spanish and British patients, respectively. Two outcomes were considered: change in the Disease Activity Score in 28 joint (ΔDAS28) and the European League Against Rheumatism (EULAR) response criteria.

Results

An association between less response to INX and incompatibility of the G1m1,17 allotype was found in the discovery collection at 6 months of treatment (P = 0.03). This association was confirmed in the replications (P = 0.02 and 0.08, respectively) leading to a global association (P = 0.001) that involved a mean difference in ΔDAS28 of 0.4 units between compatible and incompatible patients (2.3 ± 1.5 in compatible patients vs. 1.9 ± 1.5 in incompatible patients) and an increase in responders and decrease in non-responders according to the EULAR criteria (P = 0.03). A similar association was suggested for patients treated with ADM in the discovery collection, but it was not supported by replication.

Conclusions

Our results suggest that G1m1,17 allotypes are associated with response to INX and could aid improved therapeutic targeting in RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0571-z) contains supplementary material, which is available to authorized users.

Aglycosylated full-length IgG antibodies: steps toward next-generation immunotherapeutics

Albeit the removal of Asn297 glycans of IgG perturbs the overall conformation and flexibility of the IgG CH2 domain, resulting in the loss of Fc-ligand interactions and therapeutically critical immune effector functions, aglycosylated full-length IgG antibodies are nearly identical to the glycosylated counterparts in terms of antigen binding, stability at physiological or low temperature conditions, pharmacokinetics, and biodistribution. To bypass the drawbacks of glycosylated antibodies that include glycan heterogeneity and requirement of high capital investment for biomanufacturing, aglycosylated antibodies have been developed and several are under clinical trials. Comprehensive cellular and bioprocess engineering has enabled to produce highly complex aglycosylated IgGs in a simple bacterial cultivation with comparable production level as that of mammalian cells. Moreover, extensive engineering of aglycosylated Fc has converted the aglycosylated IgG antibodies into a new class of effector functional human immunotherapeutics.

Strategic characterization of anti-drug antibody responses for the assessment of clinical relevance and impact

All therapeutic proteins have the potential to induce anti-drug antibodies (ADA). Clinically relevant ADA can impact efficacy and/or safety of a biological therapeutic. Immunogenicity assessment strategy evaluates binding and neutralizing ADA, and the need for additional characterization (e.g., epitope, titer and so on) is determined using a risk-based approach. The choice of characterization assays depends on the type, application and immunogenicity of the therapeutic. ADA characterization can impact the interpretation of the risk profile of a given therapeutic, and offers insight into opportunities for risk mitigation and management. This article describes common ADA characterization methods. Strategic assessment and characterization of clinically relevant ADA are discussed, in order to support clinical options for safe and effective patient care and disease management.

Evaluation of pre-existing antibody presence as a risk factor for posttreatment anti-drug antibody induction: analysis of human clinical study data for multiple biotherapeutics

Biotherapeutic-reactive antibodies in treatment-naïve subjects (i.e., pre-existing antibodies) have been commonly detected during clinical immunogenicity assessments; however information on pre-existing antibody prevalence, physiological effects, and impact on posttreatment anti-drug antibody (ADA) induction remains limited. In this analysis, pre-existing antibody prevalence and impact on posttreatment ADA induction were determined using ADA data from 12 biotherapeutics analyzed in 32 clinical studies. Approximately half (58%) of the biotherapeutics were associated with some level of pre-existing antibodies and 67% of those were associated with posttreatment ADA induction. Across all studies, 5.6% of study subjects demonstrated presence of pre-existing antibodies, among which, 17% of the individual subjects had posttreatment increases in their ADA titers while 16% had decreased titers and 67% had no change in titers. However, in studies conducted in the rheumatoid arthritis (RA) population, 14.8% of RA patients were associated with pre-existing antibodies and 30% of those had posttreatment titer increases. The results suggest that in most study subjects, pre-existing antibodies pose a low risk for posttreatment ADA induction. That said, the high risk of induction implicated for RA patients, primarily observed in treatments evaluating novel antibody-based constructs, indicates that further understanding of the contribution of product and disease-specific factors is needed. Cross-industry efforts to collect and analyze a larger data set would enhance understanding of the prevalence, nature, and physiological consequences of pre-existing antibodies, better inform the immunogenicity risk profiles of products associated with these antibodies and lead to better fit-for-purpose immunogenicity management and mitigation strategies.

Assessing immunogenicity of biosimilar therapeutic monoclonal antibodies: regulatory and bioanalytical considerations

This article reflects on methodological limitations for interpretation of relative immunogenicity of biosimilar and reference therapeutic monoclonal antibodies, in emphasizing the relevance of correlation of bioanalytical signals with appropriate clinical end points, and the possible need for post-marketing observational studies to indicate the impact of detected differences in anti-drug antibody incidence and magnitude on sustainability of treatment benefit. Given the current uncertainty regarding the longer term clinical impact of undesirable immunogenicity for reference products, there can be no predefined margin for an acceptable difference based on incidence and magnitude of detected anti-drug antibodies. Any detected differences should be assessed in relation to clinical parameters; and the designation of biosimilarity made with reference to the similarity demonstrated in the directly comparative quality, nonclinical and clinical evaluations. Application of this ‘totality of evidence’ approach is illustrated for infliximab and adalimumab.