Affinity capture elution bridging assay: A novel immunoassay format for detection of anti-therapeutic protein antibodies

Safety, Tolerability, and Pharmacokinetics of Donanemab in Healthy Chinese Participants: A Phase 1, Randomized, Double-Blind, Placebo-Controlled Study

Alzheimer's disease (AD), characterized by β-amyloid (Aβ) plaques and neurofibrillary tangles, is the leading cause of dementia globally. Donanemab is a humanized immunoglobulin G1 in development as a treatment to slow AD progression. This study aimed to evaluate the safety, tolerability, pharmacokinetics (PKs), and immunogenicity of donanemab in healthy Chinese adults. The study included screening, inpatient, and follow-up periods. Following successful screening, participants were assigned to one of three donanemab cohorts (350, 700, or 1400 mg) and randomized in a 5:1 ratio to receive donanemab or placebo. Participants received a single intravenous (IV) dose of donanemab or placebo, and the safety, PKs, and immunogenicity of donanemab were monitored. A total of 36 male Chinese participants were included. All treatment-emergent adverse events (TEAEs) were mild in severity. Two participants on 350 mg donanemab experienced treatment-related TEAEs. Serum concentrations decreased over time with dose-dependent PK parameters (Cmax, t1/2, AUC0-tlast, and AUC0-inf) as expected. Clearance values were similar across doses. All donanemab recipients developed treatment-emergent antidrug antibodies (ADAs) in the inpatient and follow-up periods, with similar ADA titer ranges across all donanemab doses. Single IV doses of donanemab 350, 700, and 1400 mg showed acceptable safety, tolerability, and dose-proportional PK in healthy Chinese adults.

Population Pharmacokinetics and Pharmacodynamics of Fepixnebart (LY3016859) and Epiregulin in Patients with Chronic Pain

BACKGROUND AND OBJECTIVE

Fepixnebart (LY3016859), a humanized immunoglobulin G4 monoclonal antibody with high binding affinity to epiregulin and tumor growth factor-α, is being developed as a novel analgesic to treat broad-spectrum chronic pain. Early phase clinical studies demonstrated fepixnebart has nonlinear pharmacokinetics in healthy subjects and patients with diabetic nephropathy. This population pharmacokinetic analysis used data from three 26-week, phase 2, proof-of-concept studies in osteoarthritis, diabetic peripheral neuropathic pain (DPNP), and chronic low back pain (CLBP) to characterize the pharmacokinetics of fepixnebart and predict its target engagement by epiregulin. Covariate relationships were also assessed.

METHODS

Population analysis was performed using nonlinear mixed-effects modeling software. Covariate relationships were explored graphically by plotting potential covariates versus parameters of interest. Simulated target engagement was predicted using the phase 2 dose regimen for fepixnebart (750 mg intravenous starting dose, followed by 500 mg every 2 weeks).

RESULTS

The median simulated target engagement at 2 weeks after the last dose of fepixnebart was predicted to be 92.0%, with 90% of predictions between 86.0 and 96.2% and 68.5% of subjects predicted to exhibit target engagement exceeding 90%.

CONCLUSIONS

The phase 2 dose regimen is adequate to test the analgesic effect of fepixnebart in patients with osteoarthritis, DPNP, and CLBP. In the final model, female sex and higher glomerular filtration rate were associated with higher clearance, female sex was associated with larger volume of distribution of the central compartment (Vc) than male sex, and DPNP was associated with lower Vc than CLBP. There were no significant effects on the concentration of fepixnebart at which its effect on epiregulin is half-maximal (EC50).

TRAIL REGISTRY

ClinicalTrials.gov: NCT04529096, NCT04476108, and NCT04456686.

Stability of Anti-Drug Antibodies Against Antibody Therapeutics

Biotherapeutics have the potential to elicit unwanted immune responses that can lead to the production of anti-drug antibodies (ADA). It is critical that ADA responses are detected, characterized, and monitored to understand the safety and efficacy of a drug. ADA samples must remain stable in long- and short-term storage conditions to ensure reliable analysis. Whereas the stability of anti-vaccine antibodies has been well-studied, there are few reports examining the stability of anti-therapeutic antibodies using clinical samples. In this study, ADA samples from four clinical trials of antibody therapeutics were found to be stable after long-term storage (1-10 years) at -80°C and short-term storage (24 h to two weeks) at 4°C, 22°C, and 37°C. In addition, samples were stable after 16 freeze/thaw cycles. The results demonstrate the stability of ADA in clinical samples under various conditions. Consequently, the results observed herein suggest that the routine assessment of ADA sample stability may not be warranted.

Feasibility of a direct binding electrochemiluminescence assay to detect anti-drug antibodies against therapeutic peptides

The emergence of anti-drug antibodies (ADAs) poses significant impacts on the bioactivity and toxicity of biotherapeutics including proteins and peptides. Developing reliable assays to monitor the magnitudes of ADAs in blood samples is therefore considered a crucial task in animal and human studies throughout the development of biotherapeutics. Peptides represent a significant and fast-growing category of biotherapeutics for the management of a variety of indications. While peptides generally exhibit lower immunogenicity risks compared to biologics of larger sizes, drug developers are still required to conduct the risk-based immunogenicity assessment as mandated by the regulatory authorities. To address the need for efficient detection of ADAs against therapeutic peptides, we established a straightforward electrochemiluminescence immunoassay (ECLIA) based on direct binding strategy. Our assay demonstrates its applicability across various peptide therapeutics including marketed drugs and internal investigational compounds. Through stepwise tuning of the assay procedure, we identified several key factors such as buffer, detection reagent, plate type, and conjugation strategy that collectively contribute to the assay performance. Depending on the drug molecule and positive control antibody, the assay can achieve low single-digit to two-digit ng/ml sensitivity and ideal drug tolerance. In conclusion, this ECLIA platform presents a valuable and generic tool to expedite the development and validation of ADA assays for peptide-based therapeutics.

Eliminating drug target interference with specific antibody or its F(ab')2 fragment in the bridging immunogenicity assay

Background: DB-1003 is a humanized anti-IgE monoclonal antibody with higher affinity than omalizumab. In the affinity capture elution (ACE)-based bridging electrochemiluminescent immunoassay (ECLIA) for antibodies to DB-1003, monkey serum IgE caused false-positive results. Materials & methods: The target-specific antibody or its F(ab')2 fragment was used to mitigate drug target interference in an ACE-based bridging ECLIA for the detection of anti-DB-1003 antibodies. Results: The sensitivity of the developed assay was at least 100 ng/ml. When the anti-drug antibody concentration was 250 ng/ml, the assay tolerated at least 20.0 μg/ml of the monkey IgE. Conclusion: Incorporating the target-specific antibody or its F(ab')2 fragment can overcome the interference from monkey serum IgE in ACE-based bridging ECLIA for anti-DB-1003 antibody detection.

Upfront acid treatment with low final pH: the development and testing of a novel method to improve drug tolerance in antidrug antibody assays

Background: The drug tolerance of an antidrug antibody (ADA) assay for a therapeutic monoclonal antibody was insufficient to meet the level of biotherapeutic expected in sera, and a typical acid dissociation method was inadequate. Other strategies were investigated to dissociate ADA-drug complexes and thereby improve drug tolerance. Results: Having a lower final pH of samples after acid dissociation was shown to greatly improve drug tolerance. This method was shown to improve drug tolerance in the ADA assays for four additional monoclonal antibodies and to better detect ADAs in clinical samples. Conclusion: These findings provide a novel alternative method for improving drug tolerance when other methods are not sufficient.

Preclinical risk assessment strategy to mitigate the T-cell dependent immunogenicity of protein biotherapeutics: State of the art, challenges and future perspectives

Protein therapeutics hold a prominent role and have brought significant diversity in efficacious medicinal products. Not just monoclonal antibodies and different antibody formats (pegylated antigen-binding fragments, bispecifics, antibody-drug conjugates, single chain variable fragments, nanobodies, dia-, tria- and tetrabodies), but also purified blood products, growth factors, recombinant cytokines, enzyme replacement factors, fusion proteins are all good instances of therapeutic proteins that have been developed in the past decades and approved for their value in oncology, immune-oncology, and autoimmune diseases discovery programs. Although there was an ingrained belief that fully humanized proteins were expected to have limited immunogenicity, adverse effects associated with immune responses to biological therapies raised some concern in biotech companies. Consequently, drug developers are designing strategies to assess potential immune responses to protein therapeutics during both the preclinical and clinical phases of development. Despite the many factors that can contribute to protein immunogenicity, T cell- (thymus-) dependent (Td) immunogenicity seems to play a crucial role in the development of anti-drug antibodies (ADAs) to biologics. A broad range of methodologies to predict and rationally assess Td immune responses to protein drugs has been developed. This review aims to briefly summarize the preclinical immunogenicity risk assessment strategy to mitigate the risk of potential immunogenic candidates coming towards clinical phases, discussing the advantages and limitations of these technologies, and suggesting a rational approach for assessing and mitigating Td immunogenicity.

A Monovalent Fab Affinity-Capture and Elution Bridging Immunoassay Overcomes Rheumatoid Factor Interference while Accurately Detecting Antidrug Antibodies

BACKGROUND

Rheumatoid factor (RF) consists of autoantibodies that bind the fragment crystallizable (Fc) region of human immunoglobulin G (IgG) and present in sera of rheumatoid arthritis (RA) patients. Immunoassays to detect antidrug antibodies (ADA) in RA patient samples may experience interference due to RF binding and crosslinking Fc regions of the capture and detection antibody reagents. To overcome this interference, a novel Fab affinity-capture and elution (ACE)-bridging immunoassay (Fab ACE-Bridge) was developed with monovalent-recombinant Fab to avoid RF interference.

METHODS

ACE and ACE-Bridge assays were developed to detect ADA against a therapeutic monoclonal antibody using samples from healthy donors, psoriasis patients, and RA patients. The performance of these assays was compared to a novel Fab ACE-Bridge assay, in which monoclonal antibody was replaced with monovalent Fab.

RESULTS

High screening signals in the ACE and ACE-Bridge assays were detected in RA patient samples but not in samples from healthy donors or psoriasis patients. The high screening signals in RA samples did not inhibit to the expected extent in the confirmatory assay, a consistent feature of false-positive screening results. Further investigation revealed RF as the interferent affecting assay performance. Modification of the ACE-Bridge assay by using monovalent Fab eliminated RF interference while allowing for sensitive and drug-tolerant detection of authentic ADA.

CONCLUSIONS

RF interfered significantly in traditional ACE and ACE-Bridge assays. Implementation of a novel monovalent Fab ACE-Bridge assay overcame RF interference. The use of monovalent Fab is recommended for immunogenicity assays when assessing ADA in RA patient samples.

Evolution of Antidrug Antibody Assays During the Development of Anti-Tissue Factor Pathway Inhibitor Monoclonal Antibody Marstacimab

Tissue factor pathway inhibitor (TFPI) is an endogenous inhibitor of the extrinsic coagulation pathway. In patients with hemophilia A or B, inhibition of TFPI is an alternative therapeutic approach that augments the extrinsic coagulation pathway. Marstacimab is an investigational fully human monoclonal antibody that binds and neutralizes TFPI and is being evaluated as a prophylactic treatment to prevent or reduce the frequency of bleeding episodes in patients with severe hemophilia A or B, with or without inhibitors (antibodies against coagulation factors). However, the efficacy, safety, and pharmacokinetics of marstacimab may be affected by the induction of antidrug antibody (ADA) responses. Here, we describe the evolution and validation of three quasi-quantitative electrochemiluminescence-based methods to detect marstacimab ADAs, starting from their use in a first-in-human phase 1 study to their use in phase 2 and 3 clinical studies of patients with severe hemophilia. For all three methods, validation criteria evaluated the performance of the assays in screening and confirmatory cut points, precision, selectivity, drug tolerance, target interference, and stability. Additional criteria for validation were dilution linearity (Methods 1 and 2) and low positive control concentration, prozone effect, plate homogeneity, and robustness (Method 3). The three methods met validation criteria and are a potentially valuable tool in detecting the induction of marstacimab ADAs during treatment in patients with hemophilia.

A Systematic Review on the Interest of Drug-tolerant Assay in the Monitoring of Inflammatory Bowel Disease

Many patients with inflammatory bowel disease [IBD] are treated with anti-tumour necrosis factor [TNF] therapies, of which infliximab [IFX] is most commonly used. Loss of response [LOR] to anti-TNF therapy due to immunogenic failure accounts for 20% of subsequent medical intervention and is defined, using a drug-sensitive assay, as low or undetectable concentration of drug with high titres of anti-drug antibodies [ADAb]. We performed a systematic review to investigate the use of a drug-tolerant assay during both induction and maintenance, to monitor patients treated with anti-TNFs. After the search on PubMed, 90 publications were reviewed. Most ADAb detection methods are drug-sensitive, cannot detect ADAb in the presence of drug, and therefore cannot be used close to drug administration when the drug concentration is too high. To overcome this major limitation, several drug-tolerant techniques have been developed and will be discussed in this review. Using drug-tolerant assays, ADAb against IFX or adalimumab [ADM] can be detected during induction and predict primary non-response or LOR. Drug-sensitive assays do not allow detection of ADAb during the induction phase when IFX or ADM concentration is typically high.

Drug-tolerant detection of anti-drug antibodies in an antigen-binding assay using europium chelate fluorescence

Accurate anti-drug antibody (ADA) measurements in patient sera requires dissociation of ADA-drug complexes combined with sensitive and specific ADA detection. Bridging type immunoassays are often used despite several disadvantages associated with this approach. A good drug-tolerant alternative is the acid-dissociation radioimmunoassay (ARIA), but this method is not easily implemented in most labs as specialized facilities are required for working with radioactive materials. We describe an innovative method for ADA detection that combines the advantages of antigen binding tests like the ARIA with the convenience of regular immunoassays. This acid-dissociation lanthanide-fluorescence immunoassay (ALFIA) involves dissociation of ADA-drug complexes, followed by binding to an europium-labeled drug derivative and subsequently an IgG pulldown on Sepharose beads. After europium elution, detection is achieved by measuring time-resolved fluorescence originating from europium chelate complexes. We measured anti-adalimumab ADA levels in sera of 94 rheumatoid arthritis patients using the ALFIA and showed this method to be highly drug tolerant, sensitive and specific for anti-adalimumab ADAs.

Donanemab Population Pharmacokinetics, Amyloid Plaque Reduction, and Safety in Participants with Alzheimer's Disease

Donanemab is an amyloid-targeting therapy that resulted in robust amyloid plaque reduction and slowed Alzheimer's disease (AD) progression compared with placebo in the phase II TRAILBLAZER-ALZ study (NCT03367403). The objectives of the current analyses are to characterize (i) the population pharmacokinetics of donanemab, (ii) the relationship between donanemab exposure and amyloid plaque reduction (response), and (iii) the relationship between donanemab exposure and amyloid-related imaging abnormalities with edema or effusions (ARIA-E). Model development included data from participants with mild cognitive impairment or mild to moderate dementia due to AD from the phase Ib study on donanemab (NCT02624778) and participants with early symptomatic AD from the TRAILBLAZER-ALZ study. The analysis showed donanemab has a terminal elimination half-life of 11.8 days. Body weight and antidrug antibody titer impact donanemab exposure but not the pharmacodynamic response. Maintaining a donanemab serum concentration above 4.43 μg/mL (95% confidence interval: 0.956, 10.4) is associated with amyloid plaque reduction. The time to achieve amyloid plaque clearance (amyloid plaque level < 24.1 Centiloids) varied depending on the baseline amyloid level, where higher baseline levels were associated with fewer participants achieving amyloid clearance. The majority of participants achieved amyloid clearance by 52 weeks on treatment. Apolipoprotein ε4 carriers, irrespective of donanemab serum exposure, were 4 times more likely than noncarriers to have an ARIA-E event by 24 weeks.

Development, Validation and Application of a Bridging ELISA for Detection of Antibodies against GQ1001 in Cynomolgus Monkey Serum

Immunogenicity is a major issue associated with the PK, efficacy, and safety evaluation of therapeutic protein products during pre-clinical and clinical studies. A multi-tiered approach consisting of screening, confirmatory, and titration assays has been widely adopted for anti-drug antibody testing. GQ1001, a recombinant humanized anti-human epidermal growth factor receptor 2 monoclonal antibody covalently linked to a cytotoxin of DM1, possesses a novel format of antibody-drug conjugates. In this study, we reported the development, validation, and application of an acid-dissociation bridging enzyme-linked immunosorbent assay for the detection of antibodies against GQ1001 in cynomolgus monkey serum. The sensitivity of the screening assay was 126.141 ng/mL in undiluted serum. The screening assay and confirmatory assay were neither affected by the naïve monkey serum nor by 2% and 5% (v/v) erythrocyte hemolysates. Moreover, the assay was not subject to interference by 2500 ng/mL of human IgG1 in the samples. Drug interference at low positive control (150 ng/mL) and high positive control (8000 ng/mL) of anti-GQ1001 antibodies was not observed when GQ1001 concentrations were below 3.125 μg/mL and 100 μg/mL, respectively. Furthermore, no hook effect was observed for the positive antibodies in the concentration range of 8 to 64 μg/mL. The validated assay was, thereafter, successfully applied to a single-dose toxicity study of GQ1001. Anti-drug antibody positive rates among dosing animals and testing samples were reported, and no significant impact was found on toxicokinetic outcomes.

Fit-for-purpose validation of a drug-tolerant immunogenicity assay for a human mAb drug in animal safety studies

A modified biotin-drug extraction and acid dissociation (BEAD) immunogenicity assay was developed to detect anti-drug-antibodies (ADA) against the human anti-FXIIa monoclonal antibody (mAb) drug, Garadacimab (previously called CSL312). Multiple strategies were tested to optimize the signal-to-background (S/B) ratio, assay sensitivity and the drug tolerance. The modified BEAD assay was found to be highly drug tolerant (>500 μg/ml) with a sensitivity of 100 ng/ml, in line with current FDA regulatory guidelines. The assay was validated for use in a repeat-dose animal safety study and showed an acceptable intra-assay precision and robustness but a lower inter-assay precision. In-study sample analysis confirmed that the assay was fit-for-purpose (FFP) for the context-of-use (COU) in the nonclinical study and the results obtained were deemed meaningful.

A sensitive and drug tolerant assay for detecting anti-AAV9 antibodies using affinity capture elution

Adeno-associated virus (AAV) based gene therapies are gaining significant momentum as a novel therapeutic modality. However, a yet unsolved concern for using AAV as a vector is the high potential to elicit humoral and cellular responses, which are often exacerbated by pre-existing immunity due to exposure to wild type AAV. Therefore, characterization of pre-existing and treatment emergent anti-AAV antibodies is of great importance to the development of AAV based gene therapies. In this project, a sensitive and drug tolerant total antibody (TAb) assay was developed using recombinant AAV9-GFP (green fluorescent protein) as a surrogate AAV9. The assay format was affinity capture and elution (ACE) with ruthenium labeled AAV9-GFP as detection. Upon evaluation, three commercial anti-AAV9 monoclonal antibodies (clones HI17, HI35, and HL2374) were chosen and mixed at equal concentrations as positive control material. The assay sensitivity was estimated to be 11.2 ng/mL. Drug tolerance was estimated to be 5.4 × 10E10 DRP/mL AAV9-GFP at 100 ng/mL anti-AAV9 antibodies and to be at least 1 × 10E11 DRP/mL at 500 ng/mL and 250 ng/mL anti-AAV9 antibodies. The assay showed desirable specificity and precision. Using this TAb assay, significant pre-existing antibodies were detected from normal human sera.

Current Analytical Strategies for Antibody-Drug Conjugates in Biomatrices

Antibody-drug conjugates (ADCs) are a new class of biotherapeutics, consisting of a cytotoxic payload covalently bound to an antibody by a linker. Ligand-binding assay (LBA) and liquid chromatography-mass spectrometry (LC-MS) are the favored techniques for the analysis of ADCs in biomatrices. The goal of our review is to provide current strategies related to a series of bioanalytical assays for pharmacokinetics (PK) and anti-drug antibody (ADA) assessments. Furthermore, the strengths and limitations of LBA and LC-MS platforms are compared. Finally, potential factors that affect the performance of the developed assays are also provided. It is hoped that the review can provide valuable insights to bioanalytical scientists on the use of an integrated analytical strategy involving LBA and LC-MS for the bioanalysis of ADCs and related immunogenicity evaluation.

Immunogenicity assessment of bispecific antibody-based immunotherapy in oncology

With increasing numbers of bispecific antibodies (BsAbs) and multispecific products entering the clinic, recent data highlight immunogenicity as an emerging challenge in the development of such novel biologics. This review focuses on the immunogenicity risk assessment (IgRA) of BsAb-based immunotherapies for cancer, highlighting several risk factors that need to be considered. These include the novel scaffolds consisting of bioengineered sequences, the potentially synergistic immunomodulating mechanisms of action (MOAs) from different domains of the BsAb, as well as several other product-related and patient-related factors. In addition, the clinical relevance of anti-drug antibodies (ADAs) against selected BsAbs developed as anticancer agents is reviewed and the advances in our knowledge of tools and strategies for immunogenicity prediction, monitoring, and mitigation are discussed. It is critical to implement a drug-specific IgRA during the early development stage to guide ADA monitoring and risk management strategies. This IgRA may include a combination of several assessment tools to identify drug-specific risks as well as a proactive risk mitigation approach for candidate or format selection during the preclinical stage. The IgRA is an on-going process throughout clinical development. IgRA during the clinical stage may bridge the gap between preclinical immunogenicity prediction and clinical immunogenicity, and retrospectively guide optimization efforts for next-generation BsAbs. This iterative process throughout development may improve the reliability of the IgRA and enable the implementation of effective risk mitigation strategies, laying the foundation for improved clinical success.

Novel methodology comparing two assay formats for the assessment of immunogenicity from clinical trial samples

Aim: We present a novel methodology to compare results between distinct immunogenicity assays, performed by two laboratories, for the same biotherapeutic. Materials & methods: Human serum pools from clinical trials were generated to provide representative immunogenicity titers. Pools were evaluated at two laboratories in a blinded fashion to assess the effect of assay format and laboratory change on clinical interpretation of immunogenicity results. Results: The laboratories validated two different assay formats and demonstrated comparable sensitivity and drug tolerance. Overall, the comparisons in assay format and laboratory ensured a comparable ability to detect treatment-emergent antidrug antibodies for a biotherapeutic. Conclusion: We have established an approach, using pooling of patient samples, that allows for the interlaboratory comparisons without creating duplicative results.

A bridging immunogenicity assay for anti-cabiralizumab antibodies: overcoming the low assay cut point and drug tolerance challenges

Background: To support the clinical studies of cabiralizumab, an immunogenicity assay for detecting anti-cabiralizumab antibodies is required. Results: Strategies were developed to overcome two major bioanalytical challenges: poor drug tolerance of the anti-drug antibodies assay and very low cut point observed in the screening and confirmatory assays. By using acid dissociation (400 mM glycine solution at pH 2.0), drug tolerance of 200 μg/ml drug was achieved for both the screening and confirmatory assays. Effects of biological matrix (disease state vs normal serum) and assay conditions (capture/detector reagent concentration, minimum required dilution, acid pretreatment) on assay cut points were systematically evaluated. Conclusion: A bridging immunogenicity assay for detecting anti-cabiralizumab antibodies in human serum has been successfully developed, validated and applied to clinical studies.

Trastuzumab immunogenicity development in patients' sera and in laboratory animals

Background

Immunogenicity is a major challenge in drug development and patient care. Clinicians and regulators are familiar with immunogenicity concerns of monoclonal antibody (mAb) therapeutics, growth factors and enzyme replacements. Although most small therapeutic molecules are unlikely to trigger undesirable immunogenic responses against themselves upon their administration, the biological therapeutic agents are likely to induce such kind of immunogenicity. This imparts a problem that has to be considered upon judging their risk–benefit ratio. In this article, we tested the immunogenicity developed in patients’ sera due to the use of trastuzumab and that developed in laboratory animals injected with this recombinant humanized IgG1 monoclonal antibody.

Methods

We studied trastuzumab immunogenicity by: I in vitro detection of anti-trastuzumab antibody (Ab) levels in patient’s serum samples withdrawn at different points during trastuzumab treatment course; I.1 using an Affinity Capture Elution (ACE) assay, the assay is both sensitive and highly tolerant to free drug; I.2 using MTT cytotoxicity method against MCF-7 cell line as confirmatory method used in sample showed high level of anti-trastuzumab Ab and to determine neutralizing activity of the anti-trastuzumab Ab. II in vivo immunogenicity testing of trastuzumab in lab animals.

Results

In vitro analysis of patients’ sera for antibodies developed against trastuzumab revealed that this monoclonal antibody has low immunogenicity since most samples showed low levels of anti-trastuzumab antibodies that decreased progressively along the treatment course. Only 1% of samples showed high levels of anti-trastuzumab antibodies which might affect treatment course. In vivo immunogenicity testing in mice showed also low immunogenicity of trastuzumab that could support the in vitro clinical assessment applied in our study.

Conclusions

The study gives an evidence for the low trastuzumab immunogenicity when assessed in Egyptian patients under treatment with this biological therapeutic agent. This supports its prescription and continuous use across the approved indications as biological therapeutic agent.

The method history report: an adaptable tool for communicating immunogenicity assay development and validation

Over the developmental lifetime of a therapeutic protein, the immunogenicity assay validation history can become substantial, frustrating review of clinical immunogenicity within the biologics license application. In our experience, this can lead to questions by regulators, resulting in numerous information requests during the review process. To address this, we propose a new document, the method history report (MHR), which can comprehensively present the history of the immunogenicity assay for regulators, including assay development and validation. The flexibility of the MHR allows for adaptation to the specific needs of each therapeutic program, while maintaining a consistent template. Here, we detail the rationale, general outline and template for the MHR and recommend others consider adopting it for their biologics license application-related activities.

Development and validation of a novel immunogenicity assay to detect anti-drug and anti-PEG antibodies simultaneously with high sensitivity

Polyethylene glycol (PEG) represents an effective strategy to improve the pharmacokinetic profile of a molecule as it extends the biotherapeutic's half-life, masks immunogenic epitopes or modifies its distribution. The addition of one or multiple PEG moieties, in either linear or branched form, is known to carry the risk of potentially inducing an immunogenic response against PEG. The importance of accurately quantifying anti-PEG antibodies during a clinical study is well recognized and stems from the fact that anti-PEG antibodies have been shown to negatively impact the efficacy of the biotherapeutic that the PEG is coupled to. As a consequence, sponsors are encouraged to develop immunogenicity assays to assess appropriately the presence of anti-drug antibodies (ADA) against the protein component as well as the PEG. However, detection of anti-PEG antibodies is complicated by a number of technical challenges, including the availability of appropriate positive control material. In addition, the fact that some anti-PEG antibodies are known to circulate as low-affinity IgM, drives the need for an assay able to detect low affinity anti-PEG ADA even in the presence of high concentrations of the biotherapeutic. To address this need, we developed and validated an Affinity Capture Elution (ACE)-AGL assay to detect anti-drug and anti-PEG antibodies. In this assay, which we call ACE-AGL, ADA are captured by biotin-PEG-drug, acid eluted and re-captured on a second plate coated with protein AGL. ADA are then detected using Ruthenium-PEG-drug. The new assay format described is highly sensitive to both anti-drug and anti-PEG antibodies and very drug-tolerant. The ACE-AGL assay is easy to perform and has been successfully validated at two separate CROs. We propose the ACE-AGL format as a valid and effective alternative to the currently available assay methods.

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.

Validation of a de-immunization strategy for monoclonal antibodies using cynomolgus macaque as a surrogate for human

The immunogenicity of biotherapeutics presents a major challenge during the clinical development of new protein drugs including monoclonal antibodies. To address this, multiple humanization and de-immunization techniques that employ in silico algorithms and in vitro test systems have been proposed and implemented. However, the success of these approaches has been variable and to date, the ability of these techniques to predict immunogenicity has not been systematically tested in humans or other primates. This study tested whether antibody humanization and de-immunization strategies reduce the risk of anti-drug antibody (ADA) development using cynomolgus macaque as a surrogate for human. First human-cyno chimeric antibodies were constructed by grafting the variable domains of the adalimumab and golimumab monoclonal antibodies onto cynomolgus macaque IgG1 and Igκ constant domains followed by framework germlining to cyno to reduce the xenogenic content. Next, B and T cell epitopes and aggregation-prone regions were identified using common in silico methods to select domains with an ADA risk for additional modification. The resultant engineered antibodies had a comparable affinity for TNFα, demonstrated similar biophysical properties, and exhibited significantly reduced ADA levels in cynomolgus macaque compared with the parental antibodies, with a corresponding improvement in the pharmacokinetic profile. Notably, plasma concentrations of the engineered antibodies were quantifiable through 504 hours (chimeric) and 840 hours (germlined/de-immunized), compared with only 336 hours (adalimumab) or 336-672 hours (golimumab). The results point to the significant value in the investment in these engineering strategies as an important guide for monoclonal antibody optimization that can contribute to improved clinical outcomes.

Correlation between antidrug antibodies, pre-existing antidrug reactivity, and immunogenetics (MHC class II alleles) in cynomolgus macaque

Immunogenicity of biomolecules is one of the largest concerns in biological therapeutic drug development. Adverse immune responses as a result of immunogenicity to biotherapeutics range from mild hypersensitivity reactions to potentially life-threatening anaphylactic reactions and can negatively impact human health and drug efficacy. Numerous confounding patient-, product- or treatment-related factors can influence the development of an immune reaction against therapeutic proteins. The goal of this study was to investigate the relationship between pre-existing drug reactivity (PE-ADA), individual immunogenetics (MHC class II haplotypes), and development of treatment-induced antidrug antibodies (TE-ADA) in cynomolgus macaque. PE-ADA refers to the presence of antibodies immunoreactive against the biotherapeutic in treatment-naïve individuals. We observed that PE-ADA frequency against four different bispecific antibodies in naïve cynomolgus macaque is similar to that reported in humans. Additionally, we report a trend towards an increased incidence of TE-ADA development in macaques with high PE-ADA levels. In order to explore the relationship between MHC class II alleles and risk of ADA development, we obtained full-length MHC class II sequences from 60 cynomolgus macaques in our colony. We identified a total of 248 DR, DP, and DQ alleles and 236 unique haplotypes in our cohort indicating a genetically complex set of animals potentially reflective of the human population. Based on our observations, we propose the evaluation of the magnitude/frequency of pre-existing reactivity and consideration of MHC class II genetics as additional useful tools to understand the immunogenic potential of biotherapeutics.

Investigation of pre-existing reactivity to biotherapeutics can uncover potential immunogenic epitopes and predict immunogenicity risk

Despite recent advances in the development of tools to predict immunogenicity risk of biotherapeutic molecules, the ability of a protein to elicit the formation of anti-drug antibodies (ADA) remains one of the most common causes for termination of clinical development programs. In this study, we use ADA assays to detect and measure pre-existing reactivity or the ability of a molecule to produce an ADA-like response in serum from treatment-naïve, healthy donors. We report herein that the magnitude of pre-existing reactivity evaluated pre-clinically and expressed as the 90th percentile of Tier 2 inhibition correlates with the subsequent rate of ADA emergence in the clinic. Furthermore, a multi-domain biotherapeutic (IgG-scFv bispecific antibody) showed the highest pre-existing reactivity and incidence of treatment-emergent ADA (TE-ADA) (57% and 93%, respectively). Using the components of the multidomain molecule in the Tier 2 step of the ADA assay, we were able to identify the scFv as the target of the serum pre-existing reactivity. Most importantly, the domain specificity of pre-existing ADA was the same as that of the TE-ADA from patients treated with the molecule. Based on these data, we propose the evaluation of the magnitude and of the domain specificity of pre-existing reactivity as a powerful tool to understand the immunogenic potential of novel biotherapeutics.

Immunogenicity of Therapeutic Antibodies: Monitoring Antidrug Antibodies in a Clinical Context

One of the factors that may impact drug levels of therapeutic antibodies in patients is immunogenicity, with potential loss of efficacy. Nowadays, many immunogenicity assays are available for testing antidrug antibodies (ADA). In this article, we discuss different types of immunogenicity assays and their clinical relevance in terms of drug tolerance, relation with pharmacokinetics (PK), neutralizing antibodies, potential adverse events associated with ADA, and prediction of ADA production. Drug-tolerant assays can provide insight into the process of immunogenicity, but for clinical management, these assays do not necessarily outperform drug-sensitive assays. The usefulness of any ADA assay for clinical decision making will be larger when drug concentrations are also measured, and this is true, in particular, for drug-tolerant assays.

Quartz crystal microbalance as an assay to detect anti-drug antibodies for the immunogenicity assessment of therapeutic biologics

Because of their biological origins, therapeutic biologics can trigger an unwanted deleterious immune response with some patients. The immunogenicity of therapeutic biologics can affect drug efficacy and patient safety by the production of circulating anti-drug antibodies (ADA). In this study, quartz crystal microbalance (QCM) was developed as an assay to detect ADA. Etanercept (Enbrel®) was covalently grafted to dextran-modified QCM surfaces. Rabbits were immunized with etanercept to generate ADA. Results showed the QCM assay could detect purified ADA from rabbits at concentrations as low as 50 ng/mL, within the sensitivity range of ELISA. The QCM assay could also assess the ADA isotype. It was shown that the ADA were composed of the IgG isotype, but not IgM, as expected. Furthermore, it was shown that QCM surfaces that had been used to detect ADA could be regenerated in glycine-HCl solution and reused. The QCM assay was also demonstrated to detect ADA in crude serum samples. Serum was collected from the rabbits and analyzed before and after etanercept immunization. ADA were clearly detected in serum from rabbits after immunization, but not in serum before immunization. Serum from patients administered with etanercept for rheumatoid arthritis (RA) treatment was also analyzed and compared to serum from healthy donors. Sera from 10 RA patients were analyzed. Results showed one of the RA patient serum samples may have ADA present. In conclusion, QCM appears to be a viable assay to detect ADA for the immunogenicity assessment of therapeutic biologics.

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.