Identification and inhibition of drug target interference in immunogenicity assays

Interference from anti-drug antibodies on the quantification of insulin: a comparison of an LC-MS/MS assay and immunoassays

Aim: This study aims to compare the anti-drug antibody (ADA) interference in four pharmacokinetic (PK) assays across different platforms (AlphaLISA, Gyrolab, LC-MS/MS) and to devise a strategy for ADA interference mitigation to improve the accuracy of measured drug in total PK assays.Materials & methods: Spiked test samples, created to achieve different ADA concentrations in human serum also containing an insulin analogue, were analyzed alongside pooled clinical samples using four assays.Results & conclusion: Interference was observed in all platforms. A novel approach using the Gyrolab mixing CD, including acid dissociation in the PK assay, significantly reduced interference and thereby improved relative error from >99% to ≤20% yielding measurements well within the acceptance criteria. Clinical sample results reinforced findings from the test samples.

High ionic strength dissociation assay reduces dimeric target interference in immunogenicity testing

Aim: The presence of di-/multi-meric forms of soluble target in biological samples can interfere in anti-drug antibody (ADA) assays, leading to increased background values and potentially false positivity. The authors investigated the use of the high ionic strength dissociation assay (HISDA) to reduce target interference in two different ADA assays. Results: Interference caused by homodimeric FAP was successfully eliminated to enable cut point determination after applying HISDA. Biochemical experiments confirmed the dissociation of homodimeric FAP after treatment with high ionic strength conditions. Conclusion: HISDA is a promising approach to simultaneously achieve high drug tolerance and reduced interference by noncovalently bound dimeric target molecules in ADA assays without extensive optimization, which is particularly advantageous in routine use.

Approaches for the detection and analysis of anti-drug antibodies to biopharmaceuticals: A review

Antibody-based therapeutic agents and other biopharmaceuticals are now used in the treatment of many diseases. However, when these biopharmaceuticals are administrated to patients, an immune reaction may occur that can reduce the drug's efficacy and lead to adverse side effects. The immunogenicity of biopharmaceuticals can be evaluated by detecting and measuring antibodies that have been produced against these drugs, or anti-drug antibodies (ADAs). Methods for ADA detection and analysis can be important during the selection of a therapeutic approach based on such drugs and is crucial when developing and testing new biopharmaceuticals. This review examines approaches that have been used for ADA detection, measurement, and characterization. Many of these approaches are based on immunoassays and antigen binding tests, including homogeneous mobility shift assays. Other techniques that have been used for the analysis of ADAs are capillary electrophoresis, reporter gene assays, surface plasmon resonance spectroscopy, and liquid chromatography-mass spectrometry. The general principles of each approach will be discussed, along with their recent applications with regards to ADA analysis. This article is protected by copyright. All rights reserved.

Liquid chromatography-mass spectrometry method for the quantification of an anti-sclerostin monoclonal antibody in cynomolgus monkey serum

Liquid chromatography tandem mass spectrometry (LC-MS/MS) has gradually become a promising alternative to ligand binding assay for the bioanalysis of biotherapeutic molecules, due to its rapid method development and high accuracy. In this study, we established a new LC-MS/MS method for the determination of the anti-sclerostin monoclonal antibody (SHR-1222) in cynomolgus monkey serum, and compared it to a previous electrochemiluminescence method. The antibody was quantified by detecting the surrogate peptide obtained by trypsin digestion. The surrogate peptide was carefully selected by investigating its uniqueness, stability and MS response. The quantitative range of the proposed method was 2.00-500 μg/mL, and this verified method was successfully applied to the toxicokinetic assessment of SHR-1222 in cynomolgus monkey serum. It was found that the concentrations of SHR-1222 in cynomolgus monkeys displayed an excellent agreement between the LC-MS/MS and electrochemiluminescence methods (ratios of drug exposure, 0.8-1.0). Notably, two monkeys in the 60 mg/kg dose group had abnormal profiles with a low detection value of SHR-1222 in their individual sample. Combining the high-level anti-drug antibodies (ADAs) in these samples and the consistent quantitative results of the two methods, we found that the decreased concentration of SHR-1222 was due to the accelerated clearance mediated by ADAs rather than the interference of ADAs to the detection platform. Taken together, we successfully developed an accurate, efficient and cost-effective LC-MS/MS method for the quantification of SHR-1222 in serum samples, which could serve as a powerful tool to improve the preclinical development of antibody drugs.

Overcoming multimeric target interference in a bridging immunogenicity assay with soluble target receptor, target immunodepletion and mild acidic assay pH

Background: Soluble multimeric target proteins can generate a target-mediated false-positive signal in bridging anti-drug antibody (ADA) assays. A high background signal due to target interference was observed in our anti-REGN-Y antibody assay, and two different strategies were evaluated to mitigate this false-positive signal. Results: Multiple anti-target antibodies were tested and found to be ineffective at reducing target interference, so soluble target receptor and co-factor proteins were used in combination to inhibit the target-mediated signal. These competitive blockers synergistically inhibited target interference and increased target tolerance levels, especially when the assay was performed under mild acidic conditions. A separate approach, target immunodepletion using magnetic beads conjugated with an anti-target antibody, was also effective at mitigating the target-mediated signal, also in combination with mild acidic assay pH. Both methods allowed detection of a true ADA signal in monkey and human post-dose serum samples. Conclusion: These methods provide alternative strategies for mitigating target interference when standard anti-target antibodies are ineffective, with the competitive blocker method being recommended, if possible, due to its higher throughput and easier execution.

In Vitro ELISA and Cell-Based Assays Confirm the Low Immunogenicity of VNAR Therapeutic Constructs in a Mouse Model of Human RA: An Encouraging Milestone to Further Clinical Drug Development

Anti-drug antibodies (ADAs), specific for biotherapeutic drugs, are associated with reduced serum drug levels and compromised therapeutic response. The impact of ADA on the bioavailability and clinical efficacy of blockbuster anti-hTNF-α monoclonal antibodies is well recognised, especially for adalimumab and infliximab treatments, with the large and complex molecular architecture of classical immunoglobulin antibody drugs, in part, responsible for the immunogenicity seen in patients. The initial aim of this study was to develop solid-phase enzyme-linked immunosorbent assays (ELISA) and an in vitro cell-based method to accurately detect ADA and estimate its impact on the preclinical in vivo efficacy outcomes of two novel, nonimmunoglobulin VNAR fusion anti-hTNF-α biologics (Quad-X™ and D1-NDure™-C4) and Humira®, a brand of adalimumab. Serum drug levels and the presence of ADA were determined in a transgenic mouse model of polyarthritis (Tg197) when Quad-X™ and Humira® were dosed at 1 mg/kg and D1-NDure™-C4 was dosed at 30 mg/kg. The serum levels of the Quad-X™ and D1-NDure™-C4 modalities were consistently high and comparable across all mice within the same treatment groups. In 1 mg/kg and 3 mg/kg Quad-X™- and 30 mg/kg D1-NDure™-C4-treated mice, an average trough drug serum concentration of 8 μg/mL, 50 μg/mL, and 350 μg/mL, respectively, were estimated. In stark contrast, Humira® trough serum concentrations in the 1 mg/kg treatment group ranged from <0.008 μg/mL to 4 μg/mL with trace levels detected in 7 of the 8 animals treated. Trough serum Humira® and Quad-X™ concentrations in 3 mg/kg treatment samples were comparable; however, the functionality of the detected Humira® serum was significantly compromised due to neutralising ADA. The impact of ADA went beyond the simple and rapid clearance of Humira®, as 7/8 serum samples also showed no detectable capacity to neutralise hTNF-α-mediated cytotoxicity in a murine fibrosarcoma (L929) cell assay. The neutralisation capacity of all the VNAR constructs remained unchanged at the end of the experimental period (10 weeks). The data presented in this manuscript goes some way to explain the exciting outcomes of the previously published preclinical in vivo efficacy data, which showed complete control of disease at Quad-X™ concentrations of 0.5 mg/kg, equivalent to 10x the in vivo potency of Humira®. This independent corroboration also validates the robustness and reliability of the assay techniques reported in this current manuscript, and while it comes with the caveat of a mouse study, it does appear to suggest that these particular VNAR constructs, at least, are of low inherent immunogenicity.

Mitigating target interference in bridging immunogenicity assay with target-blocking reagents and mild basic pH

Background: Soluble drug target in clinical study samples generated false positive results in anti-drug antibody (ADA) bridging assays due to target-mediated bridging. Results: The combination of two target-blocking reagents and mild basic assay pH resulted in high tolerance to recombinant target protein and reduced levels of positivity in clinical study samples with pharmacokinetic profiles that did not indicate significant ADA response. Testing with low-affinity ADA positive serum from immunized rabbits and known ADA positive samples from nonclinical studies in rats confirmed the assay's ability to detect ADA positive samples and the minimal impact of basic pH and target-blocking reagents on ADA detection. Conclusion: These strategies provide alternatives for mitigating target interference when standard target-blocking antibodies alone are ineffective.

Neutralizing Antibody Assay Development with High Drug and Target Tolerance to Support Clinical Development of an Anti-TFPI Therapeutic Monoclonal Antibody

Immunogenicity is a major challenge for protein therapeutics which can potentially reduce drug efficacy and safety and is often being monitored by anti-drug antibody (ADA) and neutralizing antibody (NAb) assays. Circulating targets and residual drugs in matrices can have significant impacts on accuracy of results from ADA and NAb assays, and sufficient drug and target tolerance for these assays are necessary. Here, we report the development of a competitive ligand binding (CLB) NAb assay for an anti-TFPI (tissue factor pathway inhibitor) monoclonal antibody (PF-06741086) with high drug and target tolerance to support ongoing clinical studies. A double acid affinity capture elution approach was used to mitigate drug interference, and a robust target removal strategy was employed to enhance target tolerance. The validated NAb assay has sensitivity of 313 ng/mL, drug tolerance of 50 μg/mL, and target tolerance of 1200 ng/mL. A step-by-step tutorial of assay development is described in this manuscript along with the rationale for using a high drug/target tolerant NAb assay. The NAb assay cut point factor obtained was 0.78. Other assay performance characteristics, e.g., precision and selectivity, are also discussed. This validated method demonstrated a superior drug and target tolerance to warrant specific and precise characterization of the NAb responses in support of ongoing clinical studies.

A bridging immunogenicity assay for monoclonal antibody: case study with SHR-1222

Aim: SHR-1222 is a humanized monoclonal antibody targeted to soluble sclerostin. To support the preclinical study of SHR-1222 in cynomolgus monkeys, a method for the detection of anti-drug antibodies is required. Results: A bridging immunogenicity method for the detection of anti-SHR-1222 antibodies was developed and validated. In the method, minimal required dilution, normalization factor and confirmatory cut point were 1:20, 4.35 and 10.45%, respectively. The method was successfully applied to evaluate a multiple-dose toxicity study in monkeys. Conclusion: The proposed method allows for the detection of anti-SHR-1222 antibodies in preclinical studies and aids in the interpretation of pharmacokinetic changes in certain animals. The soluble targets interference on anti-drug antibody detection can be blocked or decreased by the therapeutic drug.

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.

Electrochemiluminescence Assays for Human Islet Autoantibodies

Pinpointing islet autoantibodies associated with type 1 diabetes (T1D) leads the way to project and deter this disease in the general population. A novel ECL assay is a nonradioactive fluid phase assay for islet autoantibodies with higher sensitivity and specificity than the current 'gold' standard radio-binding assay (RBA). ECL assays can more precisely define the onset of presymptomatic T1D by distinguishing the high-risk, high-affinity autoantibodies from the low-risk, low-affinity autoantibodies generated in RBAs, and conventional enzyme-linked immunosorbent assays (ELISA). The antigen protein used in this ECL assay is labeled with Sulfo-tag and Biotin, respectively. Each ECL autoantibody assay that uses a particular antigen protein needs an optimization step before it can be used for laboratory application. This step is especially vital in determining the requirements for serum acid treatments, concentrations, and ratios of the two different antigens labeled with Sulfo-tag and Biotin. To perform the assay, serum samples are mixed with Sulfo-tag-conjugated and biotinylated capture antigen protein in phosphate buffered solution (PBS), containing 5% Bovine Serum Albumin (BSA). Afterwards, the samples are incubated overnight at 4 °C. The same day, a streptavidin-coated plate is prepared with blocker buffer and incubated overnight at 4 °C. On the second day, wash the streptavidin plate and transfer the serum-antigen mixture onto the plate. Place the plate on the plate shaker, set it at low speed, and incubate at room temperature for 1 h. Subsequently, the plate is washed again, and reader buffer is added. The plate is then counted on the plate reader machine. The results are conveyed through an index, which is generated from internal standard positive and negative control serum samples.

Novel drug and soluble target tolerant antidrug antibody assay for therapeutic antibodies bearing the P329G mutation

Aim: Bridging immunoassays for detection of antidrug antibodies (ADAs) are typically susceptible to high concentrations of residual drug. Sensitive drug-tolerant assays are, therefore, needed. Materials & methods: An immune complex assay to detect ADAs against therapeutic antibodies bearing Pro329Gly mutation was established. The assay uses antibodies specific for the Pro329Gly mutation for capture and human soluble Fcγ receptor for detection. Results: When compared with a bridging assay, the new assay showed similar precision, high sensitivity to IgG1 ADA and dramatically improved drug tolerance. However, it was not able to detect early (IgM-based) immune responses. Conclusion: Applied in combination with a bridging assay, the novel assay serves as orthogonal assay for immunogenicity assessment and allows further characterization of ADA responses.

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.

Inhibition of interleukin-5 induced false positive anti-drug antibody responses against mepolizumab through the use of a competitive blocking antibody

Mepolizumab, a humanized IgG1 monoclonal antibody that blocks native homodimeric interleukin-5 (IL-5) from binding to the IL-5 receptor, has recently been approved for treatment of severe eosinophilic asthma. Our initial immunogenicity assay method for phase I and II studies utilized a bridging electrochemiluminescence format with biotin and ruthenium-labelled mepolizumab linked by anti-drug antibodies (ADA). We discovered that IL-5 significantly increased in dosed subjects from a phase II study and that the increased IL-5 was in the form of a drug-bound complex. We demonstrated that the elevated drug-bound IL-5 produced false-positive response in the in vitro ADA assay, in which drug-bound IL-5 dissociated and then bridged mepolizumab conjugates to yield positive signal. To eliminate the IL-5 interference, we compared two strategies: a solid-phase immunodepletion of IL-5 and an in-solution IL-5 immunocompetition. We identified the best competitive antibody for each purpose. We found both methods demonstrated similar effectiveness in reducing the false positive signal in IL-5 spiked samples; however, the in-solution immunocompetition for IL-5 had fewer false positives in study samples. Additionally, the in-solution immunocompetition method was experimentally simpler to execute. We modified the ADA assay by adding a pre-treatment step with a mepolizumab competitive anti- IL-5 antibody. Using this new method, we retested clinical samples from two phase II studies (MEA112997 and MEA114092). The confirmed ADA positive incidence was reduced from 29% and 61% to 1% and 8% with the modified in-solution immune inhibition method. Target interference is a fairly common problem facing immunogenicity testing, and target-induced false positive cannot be distinguished from true ADA response by the commonly used drug competitive confirmation assay. The approach and method used here for resolving target interference in ADA detection will be useful for differentiating between a true ADA response and target induced false positive as well as similar challenges in other programs.

Detection of antidrug antibodies against human therapeutic antibodies lacking Fc-effector functions by usage of soluble Fcγ receptor I

AIM

Bridging immunoassays for the detection of antidrug antibodies (ADAs) are limited to detection of bivalent molecules and are prone to interference by drug and soluble targets. Hence, alternative approaches for ADA detection are desired. Materials & methods: A novel ADA assay with secondary Fc detection using human soluble Fcγ receptor I (hsFcγRI) was established and compared with standard bridging assay.

RESULTS

Both assays showed consistent results in human and cynomolgus monkey samples. In contrast to the bridging assay, the hsFcγRI-based assay was insensitive to the presence of oligomeric targets and appeared to have better drug tolerance.

CONCLUSION

The hsFcγRI-based ADA assay can serve as alternative screening assay or as orthogonal confirmation method for preclinical and clinical immunogenicity testing of IgG therapeutics lacking Fc effector functions.

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.

Evaluation of Multiple Immunoassay Technology Platforms to Select the Anti-Drug Antibody Assay Exhibiting the Most Appropriate Drug and Target Tolerance

The aim of this study was, at the assay development stage and thus with an appropriate degree of rigor, to select the most appropriate technology platform and sample pretreatment procedure for a clinical ADA assay. Thus, ELISA, MSD, Gyrolab, and AlphaLISA immunoassay platforms were evaluated in association with target depletion and acid dissociation sample pretreatment steps. An acid dissociation step successfully improved the drug tolerance for all 4 technology platforms and the required drug tolerance was achieved with the Gyrolab and MSD platforms. The target tolerance was shown to be better for the ELISA format, where an acid dissociation treatment step alone was sufficient to achieve the desired target tolerance. However, inclusion of a target depletion step in conjunction with the acid treatment raised the target tolerance to the desired level for all of the technologies. A higher sensitivity was observed for the MSD and Gyrolab assays and the ELISA, MSD, and Gyrolab all displayed acceptable interdonor variability. This study highlights the usefulness of evaluating the performance of different assay platforms at an early stage in the assay development process to aid in the selection of the best fit-for-purpose technology platform and sample pretreatment steps.

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

BACKGROUND

Increased emphasis on the development of biologics has placed a significant focus on anti-drug antibody (ADA) detection. To address this need, several immunoassay formats have been described for use in characterizing potential immune responses. Two commonly utilized methods include the affinity capture elution (ACE) and bridging formats. While these approaches have been effective in supporting many clinical initiatives, both possess potential disadvantages. Here, we compare these standard methods to a novel format that addresses these noted drawbacks.

RESULTS

A novel assay format has been designed to incorporate the benefits of the ACE and bridging methods while overcoming the disadvantages incurred with each approach. The described ACE-Bridge format exhibits excellent sensitivity and precision while providing superior drug tolerance when compared to bridging formats. Further, this assay format is not susceptible to the endogenous target interference that can be an issue in the ACE format.

CONCLUSIONS

The ACE-Bridge format provides an often superior option as a screening method to monitor patient ADA responses. This method is unique in its ability to measure ADA in the presence of high circulating endogenous target concentrations (>100 ng/mL) while demonstrating very high drug tolerance.

Indirect assessment of neutralizing anti-drug antibodies utilizing pharmacokinetic assay data

Neutralizing anti-drug antibodies (NAbs) can adversely impact efficacy and safety of biologic therapeutics. However, current assay formats to detect NAbs are limited in their use during the dosing phase due to interference by circulating drug, resulting in low drug tolerance. To improve the drug tolerance for NAb detection, an alternative approach for indirect NAb (iNAb) assessment was developed and qualified that uses a combination of pharmacokinetic (PK) assays to measure the serum concentrations of free and total drug. It is demonstrated that the ratio of free to total drug concentrations, referred to as F/T ratio, is a novel PK parameter that can indicate neutralizing activity in test samples. The iNAb assessment correctly identified NAb-positive samples with high drug concentrations that led to false negative results in a conventional NAb assay. Moreover, iNAb reliably distinguished between NAbs and non-neutralizing anti-drug antibodies over a wide range of concentrations. A proposal on how to deploy iNAb assessment within a broader immunogenicity testing strategy is presented.

A phase 1b, open-label study of trebananib plus bevacizumab or motesanib in patients with solid tumours

BACKGROUND

To examine the angiopoietin pathway inhibitor trebananib IV plus the anti-VEGF agents bevacizumab or motesanib in advanced solid tumours.

METHODS

In this open-label phase 1b study, patients received IV trebananib 3 mg kg-1 QW plus bevacizumab 15 mg kg-1 Q3W (cohort 1) or motesanib orally 75 mg (cohort 2); or trebananib 10 mg kg-1 plus bevacizumab 15 mg kg-1 (cohort 3) or motesanib 125 mg (cohort 4). If <33% of patients had dose-limiting toxicities (DLTs), dose escalation occurred. Endpoints were treatment-related adverse events (AEs) incidence and pharmacokinetics (primary); anti-trebananib antibodies, biomarkers, and tumour response (secondary).

RESULTS

Thirty-six patients received ≥ 1 dose of trebananib (cohorts 1, 2, 3, 4; n = 6, 8, 19, 3). DLT of G3 intestinal perforation and G3 tumor haemorrhage occurred in cohorts 2 and 3, respectively (both n = 1). Across both trebananib plus bevacizumab cohorts, the most common AEs included fatigue (n = 8), diarrhoea (n =4), constipation (n = 3), nausea (n = 3), and epistaxis (n = 3). Three patients across those cohorts had grade ≥ 3 AEs. Across the trebananib plus motesanib cohorts, the most common AEs included hypertension (n = 4), diarrhoea (n = 4), nausea (n = 3), fatigue (n = 3), vomiting (n = 2), and decreased appetite (n = 2). Two patients had grade ≥ 3 AEs. Trebananib did not markedly affect motesanib pharmacokinetics. Across the trebananib plus bevacizumab cohorts, two patients had a partial response; 11 patients had stable disease lasting >6 months. Across the trebananib plus motesanib cohorts, one patient had a partial response; five patients had stable disease lasting >6 months.

CONCLUSION

Trebananib IV 3 mg kg-1 or 10 mg kg-1 plus bevacizumab or motesanib in advanced solid tumours may be associated with less severe toxicities relative to those emerging when combining two anti-VEGF agents.

Standardizing terms, definitions and concepts for describing and interpreting unwanted immunogenicity of biopharmaceuticals: recommendations of the Innovative Medicines Initiative ABIRISK consortium

Biopharmaceuticals (BPs) represent a rapidly growing class of approved and investigational drug therapies that is contributing significantly to advancing treatment in multiple disease areas, including inflammatory and autoimmune diseases, genetic deficiencies and cancer. Unfortunately, unwanted immunogenic responses to BPs, in particular those affecting clinical safety or efficacy, remain among the most common negative effects associated with this important class of drugs. To manage and reduce risk of unwanted immunogenicity, diverse communities of clinicians, pharmaceutical industry and academic scientists are involved in: interpretation and management of clinical and biological outcomes of BP immunogenicity, improvement of methods for describing, predicting and mitigating immunogenicity risk and elucidation of underlying causes. Collaboration and alignment of efforts across these communities is made difficult due to lack of agreement on concepts, practices and standardized terms and definitions related to immunogenicity. The Innovative Medicines Initiative (IMI; http://www.imi-europe.org), ABIRISK consortium [Anti-Biopharmaceutical (BP) Immunization Prediction and Clinical Relevance to Reduce the Risk; http://www.abirisk.eu] was formed by leading clinicians, academic scientists and EFPIA (European Federation of Pharmaceutical Industries and Associations) members to elucidate underlying causes, improve methods for immunogenicity prediction and mitigation and establish common definitions around terms and concepts related to immunogenicity. These efforts are expected to facilitate broader collaborations and lead to new guidelines for managing immunogenicity. To support alignment, an overview of concepts behind the set of key terms and definitions adopted to date by ABIRISK is provided herein along with a link to access and download the ABIRISK terms and definitions and provide comments (http://www.abirisk.eu/index_t_and_d.asp).

Recommendations for the development and validation of confirmatory anti-drug antibody assays

Identification and characterization of anti-drug antibodies is a critical component of biopharmaceutical drug development. The tiered approach for immunogenicity testing consists of screening, confirmatory, and characterization assays. Herein, we provide recommendations for confirmatory assays by expanding upon published guidance and present common practices across the industry. The authors recommend scientific approaches for development and validation of confirmatory assays using competition methods in ligand-binding assays, along with statistical formulae for routine use and validation. The paper will assist in understanding the confirmatory assay, and carefully implementing validation criteria a priori, as well as during sample analysis. These approaches represent the authors’ current knowledge and practices, with the aim that more uniform practices will be applied across the industry.

Development and validation of an LC-MS/MS assay for the quantitation of a PEGylated anti-CD28 domain antibody in human serum: overcoming interference from antidrug antibodies and soluble target

AIM

To support drug development of a PEGylated anti-CD28 domain antibody, a sensitive and robust LC-MS/MS assay was developed for the first in-human multiple ascending dose study.

MATERIALS & METHODS

The procedure consists of a protein precipitation with acidified acetonitrile, followed by trypsin digestion of the supernatant. A surrogate peptide from the complementarity determining region was quantified with an LC-MS/MS assay using a stable isotope-labeled internal standard with flanking amino acids. An acid dissociation step was found to be essential to achieve full analyte recovery in the presence of antidrug antibodies and soluble target CD28.

RESULTS & CONCLUSION

The fully validated LC-MS/MS assay demonstrates good accuracy (% deviation ≤6.3) and precision (%CV ≤5.2) with an lower limit of quantitation of 10 ng/ml.

Systematic comparison of drug-tolerant assays for anti-drug antibodies in a cohort of adalimumab-treated rheumatoid arthritis patients

Drug interference complicates assessment of immunogenicity of biologicals and results in an underestimation of anti-drug antibody (ADA) formation. Drug-tolerant assays have the potential to overcome such limitations. However, to which extent drug-tolerant assays provide an unbiased picture of the antibody response to a biological is unknown. In this study, we compared the measurement of ADA to adalimumab in 94 consecutive adalimumab-treated rheumatoid arthritis patients using the traditional antigen binding test (ABT) and four different drug-tolerant assays, the Ph-shift anti-Idiotype Antigen binding test (PIA) and three newly developed assays for this study: an acid-dissociation radioimmunoassay (ARIA), a temperature-shift radioimmunoassay (TRIA) and an electrochemoluminescence-based assay (ECL). Our results indicate that drug-tolerant assays provide a fairly consistent view on the antibody formation: quantitatively, the results from all four assays correlate well (Spearman r > 0.9). However, the percentage of ADA-positive patients ranges from 51 to 66% between assays, with the ARIA identifying the highest number of patients as positive. These differences are largely due to patients making low amounts of ADA; if ADA levels were above ca. 100 AU/ml, a patient was identified as positive in all four assays. Adalimumab concentrations were significantly lower in ADA-positive samples. Taken together, the results indicate that these different drug-tolerant assays provide a similar and reasonably consistent view on ADA responses, which however, breaks down at the lower end of the detectable range, and highlight that ADA is best reported quantitatively. Furthermore, if an even more sensitive drug-tolerant assay could be developed, one would probably find additional positive samples that will predominantly contain very low levels of ADA.

A phase 1b study of trebananib in combination with pegylated liposomal doxorubicin or topotecan in women with recurrent platinum-resistant or partially platinum-sensitive ovarian cancer

OBJECTIVE

To examine the tolerability and antitumor activity of trebananib plus pegylated liposomal doxorubicin (PLD) or topotecan in recurrent platinum-resistant or partially platinum-sensitive ovarian cancer.

METHODS

In this open-label phase 1b study, patients received trebananib 10 mg/kg or 15 mg/kg IV QW plus PLD 50 mg/m(2) (cohorts A1 and A3, respectively) or topotecan 4 mg/m(2) (cohorts B1 and B3, respectively). Endpoints were dose-limiting toxicity (DLT; primary); treatment-emergent adverse events (AEs), overall response rate, anti-trebananib antibodies, and pharmacokinetics (secondary).

RESULTS

103 patients were enrolled. One patient in A1 and B1 had DLTs. Across all cohorts, the most common AEs were nausea, fatigue, and peripheral edema. Across both trebananib plus PLD cohorts (A1/A3), grade 4 AEs were pulmonary embolism, disease progression, and anemia. Two patients had grade 5 intestinal perforation (n=1) and sudden death (n=1). Across both trebananib plus topotecan cohorts (B1/B3), grade 4 AEs were neutropenia, hypokalemia, decreased granulocyte count, chest pain, dyspnea, decreased neutrophil count, and pulmonary embolism. Two patients had grade 5 disease progression. One patient had grade 5 pleural effusion associated with progressive disease. Confirmed objective response rates were 36.0% (A1), 34.8% (A3), 16.7% (B1), and 0.0% (B3). Median progression-free survival duration (months) was 7.4 (A1), 7.1 (A3), 3.5 (B1), and 3.1 (B3), respectively. No drug-drug interactions were apparent.

CONCLUSIONS

Trebananib 10mg/kg and 15 mg/kg IV QW plus PLD or topotecan appear to have acceptable toxicity profiles in recurrent platinum-resistant or partially platinum-sensitive ovarian cancer. Antitumor activity was evident across all cohorts.

Interference in immunoassays to support therapeutic antibody development in preclinical and clinical studies

During preclinical and clinical studies, immunoassays are used to measure the concentration of the therapeutic antibody, anti-drug antibodies and soluble protein biomarkers. The reliability of these assays is crucial since the results are routinely used for safety assessment and dose selection. Furthermore, soluble protein biomarkers can provide information about target engagement, proof of mechanism, proof of principle and prediction of response. Study samples mostly consist of complex matrices that can exhibit considerable interference, resulting in inaccurate measurements. This perspective discusses the source of interference and strategies to mitigate or eliminate interference in immunoassays used during preclinical and clinical drug development of drugs with a focus on the development of therapeutic antibodies.

How the bioanalytical scientist plays a key role in interdisciplinary project teams in the development of biotherapeutics – a reflection of the European Bioanalysis Forum

The bioanalytical scientist plays a key role in the project team for the drug development of biotherapeutics from the discovery to the marketing phase. Information from the project team members is required for assay development and sample analysis during the discovery, preclinical and clinical phases of the project and input is needed from the bioanalytical scientist to help data interpretation. The European Bioanalysis Forum target team 20 discussed many of the gaps in information and communication between the bioanalytical scientist and project team members as a base for providing a perspective on the bioanalytical scientist's role and interactions within the project team.

Resolution of matrix interference: quantitative and quasi-quantitative ligand-binding assays case studies

Background: Matrix effects pose a constant challenge in developing robust ligand-binding assays to be validated for use in nonclinical and clinical study support. When notable matrix effects of any kind are present, it can render an otherwise sound method ineffective. We present two case studies detailing the mitigation of observed matrix effects. Method: A dimeric protein was removed from unknown samples in an anti-therapeutic antibody assay through protein extraction. Nonspecific matrix effects in a quantitative ligand-binding assays were mitigated through development of a specialized buffer. Results: The protein extraction method reproducibly reduced the artificially high responses of naïve samples, enabling the accurate detection of anti-therapeutic antibodies. Design of experiments was used to evaluate and select the optimal components and associated concentrations in order to reduce the observed matrix effect to acceptable limits. Conclusion: Our results suggest there are multiple techniques available for the bioanalytical scientist to mitigate both matrix effects in ligand-binding assays.

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.

A phase I, open-label study of trebananib combined with sorafenib or sunitinib in patients with advanced renal cell carcinoma

BACKGROUND

Trebananib, an investigational peptibody, binds to angiopoietin 1 and 2, thereby blocking their interaction with Tie2.

PATIENTS AND METHODS

This open-label phase I study examined trebananib 3 mg/kg or 10 mg/kg intravenous (I.V.) once weekly plus sorafenib 400 mg twice per day or sunitinib 50 mg once per day in advanced RCC. Primary end points were adverse event incidence and pharmacokinetics.

RESULTS

Thirty-seven patients were enrolled. During trebananib plus sorafenib administration (n = 17), the most common treatment-related adverse events (TRAEs) included rash (n = 12; 71%), diarrhea (n = 12; 71%), hypertension (n = 11; 65%), and fatigue (n = 11; 65%); grade ≥ 3 TRAEs (n = 7; 41%); and 2 patients (12%) had peripheral edema. During trebananib plus sunitinib administration (n = 19), the most common TRAEs included diarrhea (n = 14; 74%), fatigue (n = 13; 68%), hypertension (n = 11; 58%), and decreased appetite (n = 11; 58%); grade ≥ 3 TRAEs (n = 13; 68%); and 8 (42%) patients had peripheral edema. Trebananib did not appear to alter the pharmacokinetics of sorafenib or sunitinib. No patient developed anti-trebananib antibodies. Objective response rates were 29% (trebananib plus sorafenib) and 53% (trebananib plus sunitinib).

CONCLUSION

The toxicities of trebananib 3 mg/kg or 10 mg/kg I.V. plus sorafenib or sunitinib in RCC were similar to those of sorafenib or sunitinib monotherapy, with peripheral edema being likely specific to the combinations. Antitumor activity was observed.

Statistical and bioanalytical considerations for establishing a depletion criterion for specificity testing during immunogenicity assessment of a biotherapeutic

Immunogenicity assessment of fully human monoclonal antibody-based biotherapeutics requires sensitive and specific ligand binding assays. One of the components of specificity is the depletion of signal by a relevant biotherapeutic that is commonly based on an arbitrary depletion criterion of inhibition of the original response or reduction of the signal below the screening assay cut point (ACP). Hence, there is a need to develop a statistically derived physiologically relevant specificity criterion. We illustrate an optimization approach to determine the concentration of biotherapeutic required for the specificity evaluation. Naïve donor sample sets with and without circulating drug and antitherapeutic/drug antibody (ADA) were prepared. Next, a depletion cut point (DCP) using naïve and ADA-containing donor sets with the optimized biotherapeutic concentration was evaluated. A statistically derived design of experiment was used to establish a validated DCP. A reliable DCP requires naïve (no ADA) donors treated only with an optimized concentration of biotherapeutic. The additional DCPs generated using two distinct concentrations of ADA-spiked sample sets led to a physiologically irrelevant criterion that was not necessarily representative of real-time samples. This increased the risk of false positives or negatives. In this study, well-defined bioanalytical and statistical methods were employed to validate a DCP to confirm the presence of biotherapeutic specific ADA in human serum samples. A physiologically relevant and effective strategy to confirm specificity in immune reactive samples, especially those that are close to the ACP, is proposed through this study.

Development of a biosensor-based immunogenicity assay capable of blocking soluble drug target interference

As with other protein therapeutics, trebananib (AMG 386), an investigational peptide Fc-fusion protein ("peptibody") that inhibits angiogenesis by neutralizing the interaction of angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2) with the Tie2 receptor, has the potential to trigger an immune response in cancer patients treated with the therapeutic. An electrochemiluminescence bridging anti-drug antibody (ADA) assay that was utilized to support early-phase clinical trials in the development of trebananib was found to lack adequate sensitivity and drug tolerance in later-phase clinical studies when higher doses of trebananib were administered. Therefore, we developed a surface plasmon resonance (SPR) immunoassay method utilizing a secondary confirmatory detector antibody (goat anti-human IgG F[ab']2) known to cross-react with human IgG and IgM to better assess the potential impact of immunogenicity on the pharmacokinetics, pharmacodynamics, and toxicity of trebananib. The SPR method was more sensitive than the electrochemiluminescence bridging assay because of signal amplification from the confirmatory binding of the detector antibody; drug tolerance was improved since antibody binding avidity does not affect detection on this platform. Despite the inability of the confirmatory detector antibody to bind angiopoietins in protein-free buffer, false-positive ADA results were generated from patient serum samples containing Ang1 and Ang2 through an apparently specific binding between the angiopoietins and the confirmatory detector antibody, likely mediated by the interaction of the angiopoietins with serum immunoglobulins. Addition to the sample diluent of a human antibody that specifically binds to Ang1 and Ang2 with high affinity resulted in a complete block of angiopoietin interference without affecting ADA detection. This biosensor-based assay provides a reliable method for assessing immunogenicity in phase 3 clinical trials.

Minimizing target interference in PK immunoassays: new approaches for low-pH-sample treatment

Background: Quantitating total levels of monoclonal antibody (mAb) biotherapeutics in serum using ELISA may be hindered by soluble targets. Results: We developed two low-pH-sample-pretreatment techniques to minimize target interference. The first procedure involves sample pretreatment at pH <3.0 before neutralization and analysis in a target capture ELISA. Careful monitoring of acidification time is required to minimize potential impact on mAb detection. The second approach involves sample dilution into mild acid (pH ∼4.5) before transferring to an anti-human capture-antibody-coated plate without neutralization. Analysis of target–drug and drug–capture antibody interactions at pH 4.5 indicated that the capture antibody binds to the drug, while the drug and the target were dissociated. Using these procedures, total biotherapeutic levels were accurately measured when soluble target was >30-fold molar excess. Conclusion: These techniques provide alternatives for quantitating mAb biotherapeutics in the presence of a target when standard acid-dissociation procedures are ineffective.

An electrochemiluminescence (ECL)-based assay for the specific detection of anti-drug antibodies of the IgE isotype

To address a possible linkage between the occurrence of the hypersensitivity reactions and the induction of IgE anti-drug-antibodies (ADA), a drug specific IgE ADA assay was developed using electrochemiluminescence (ECL) technology. In the assay a drug-specific IgE isotype chimeric antibody was generated and used as an ADA positive control. The biotinylated drug X (an antibody) and ruthenium-labeled omalizumab (an anti-human IgE antibody) were used as capture and detection reagents, respectively. The binding affinities of the chimeric IgE isotype positive control have been shown to be highly comparable to drug X and drug Y (drug X is the 2nd generation of drug Y), indicating that it could serve as a highly useful control to compare and contrast the relative ability of the two generations of drug to elicit IgE ADA responses. The assay cut point factor (CPF) was estimated to be 1.13. The cut point factor derived from normal human serum samples was statistically equivalent to the cut point factor determined from targeted population samples. The assay could detect less than 250ng/mL of IgE antibodies in the presence of 300μg/mL drug X. The assay sensitivity was <0.2ng/mL. A minimal prozone was observed at 100μg/mL IgE ADA, but the sample remained highly detectable. The inter-assay precision was within 12%. The assay was not susceptible to non-specific matrix effects. The performance specifications ensured that the assay was suitable for validation. The combination of the chimeric IgE positive control and the detection antibody (ruthenium-labeled omalizumab) used for the assay could potentially provide a general bioanalytical approach for other biopharmaceuticals for the detection of IgE ADA responses.

False-positive immunogenicity responses are caused by CD20+ B cell membrane fragments in an anti-ofatumumab antibody bridging assay

An electrochemiluminescent (ECL) bridging assay to detect anti-ofatumumab antibodies (ADA) in human serum samples was developed and validated. Using this assay format, clinical samples were first screened to identify potential ADA positive samples, which were then further tested by adding excess drug, confirming the positive signals as drug specific. However, when the method was implemented into clinical studies for ADA testing, a high positive rate was observed in the pre-dose samples collected from patients with chronic lymphocytic leukemia (CLL). Since the positive signals were not associated with ofatumumab (Ofa) treatment, and diminished after treatment, it was suspected that matrix interference might be responsible, resulting in false-positive responses. We performed a series of experimental investigations to identify, characterize, minimize or eliminate the possible false-positive responses. One possible source was identified to be CD20 (the target of Ofa) present on cell membrane fragments (CMFs). The false-positive responses caused by CD20(+) CMFs could be reduced by solid-phase immunodepletion, ultracentrifugation, or inhibited by adding another anti-CD20 antibody (rituximab). As a consequence, the ADA method was modified to minimize the matrix interference caused by CD20(+) CMFs and, then, validated for sample testing.

Theoretical considerations and practical approaches to address the effect of anti-drug antibody (ADA) on quantification of biotherapeutics in circulation

Continuous improvement in bioanalytical method development is desired in order to ensure the quality of the data and to better support pharmacokinetic (PK) and safety studies of biotherapeutics. One area that has been getting increasing attention recently is in the assessment of "free" and "total" analyte and the impact of the assay format on those assessments. To compliment these considerations, the authors provide a critical review of available literature and prospectively explore methods to mitigate the potential impact of anti-drug antibody on PK assay measurement. This challenge is of particular interest and importance since biotherapeutic drugs often elicit an immune response, and thus may have a direct impact on quantification of the drug for its PK and safety evaluations.

Overcoming soluble target interference in an anti-therapeutic antibody screening assay for an antibody-drug conjugate therapeutic

BACKGROUND

The standard safety evaluation of biotherapeutics includes assessment of immunogenicity. Anti-therapeutic antibodies (ATA) can be detected in serum using immunoassays with a bridging format. However, these assays can be subject to interference.

RESULTS

In the bridging ATA assay for 3A5 TDC, an antibody-drug conjugate that binds to the multimeric extracellular domain of MUC16 (CA125), soluble CA125 in the serum caused false-positive results by binding to the ATA assay reagents. This interaction was blocked by wheat germ agglutinin lectin as it binds to the glycans in CA125; thus, the specificity of the assay improved.

CONCLUSION

The assay development and validation results showed that the addition of wheat germ agglutinin eliminates the interference from circulating CA125 without impacting the ability to detect ATA.

Phase 1 study of trebananib (AMG 386), an angiogenesis targeting angiopoietin-1/2 antagonist, in Japanese patients with advanced solid tumors

PURPOSE

To evaluate the safety, tolerability, pharmacokinetics, and antitumor activity of trebananib (AMG 386)--a first-in-class angiopoietin-1/2 antagonist peptide-Fc fusion protein--in Japanese patients, we conducted a phase 1, dose escalation study.

METHODS

Eligible patients were men or women, aged between 20 and 74 years, who had histologically or cytologically confirmed advanced solid tumors refractory to standard treatment. Trebananib (3, 10, and 30 mg/kg) was administered intravenously over 60 min in weekly cycles.

RESULTS

From June 2009 to April 2010, a total of 18 patients (6 for each dose cohort) were enrolled into the study. Trebananib was tolerated at all dose levels. No dose-limiting toxicities were observed. The most common adverse events were peripheral edema, constipation, fatigue, and pyrexia. Exposure to trebananib appeared to increase according to the dose administered. Serum clearance appeared to be similar across the dose range with the mean terminal-phase half-life ranging from 93.9 to 95.9 h. No neutralizing antibodies were detected. Tumor response was assessed in 18 patients. Of these, one patient with colon cancer in the 3-mg/kg cohort and one with bladder cancer in the 30-mg/kg cohort had partial responses as their best responses. These 2 patients were on treatment at the time of data cutoff (January 17, 2012).

CONCLUSION

Trebananib was tolerated and showed acceptable safety profile in Japanese patients with advanced solid tumors. The pharmacokinetic profiles were similar to those in the previous studies in the United States. Trebananib also showed evidence of durable antitumor activity in some patients.

Strategic selection and development of immunogenicity binding methods

The principal components of a meaningful immunogenicity program consist of an initial binding screen followed by confirmation and quantitation of the positive samples. This comprehensive article first describes evolving technologies and assay formats that encourage scientists to start development with appropriate analytical goals that are specific to their clinical program. The selection of the technology and format is based primarily on the product’s structure, treatment indication, intended treatment schedule and pharmacokinetic profile. Feasibility studies are described to satisfy specific criteria before proceeding to optimization. Preparation procedures and storage conditions of critical reagents and controls are provided that will render them suitable throughout the length of the project. A multifactor approach to robustness is recommended that assures consistently sensitive, accurate, precise and specific methods that are verified during prevalidation experiments. Finally, a checklist itemizes all the requirements to develop a compliant validation protocol.

Distinguishing persistent insulin autoantibodies with differential risk: nonradioactive bivalent proinsulin/insulin autoantibody assay

A subset of children develops persistent insulin autoantibodies (IAA; almost always as the only islet autoantibody) without evidence of progression to diabetes. The aim of the current study was the development and characterization of the performance of a nonradioactive fluid phase IAA assay in relation to standard IAA radioassay. We developed a nonradioactive IAA assay where bivalent IAA cross-link two insulin moieties in a fluid phase. The serum samples positive for anti-islet autoantibodies from 150 newly diagnosed patients with diabetes (Barbara Davis Center plus Diabetes Autoantibody Standardization Program [DASP] workshop) and 70 prediabetic subjects who were followed to diabetes were studied. In addition, sequential samples from 64 nondiabetic subjects who were persistently IAA(+) were analyzed. With 99th percentile of specificity, the new assay with the technology from Meso Scale Discovery Company (MSD-IAA) detects as positive 61% (61 of 100) of new-onset patients and 80% (56 of 70) of prediabetic patients compared with our current fluid phase micro-IAA radioassay (mIAA; 44 and 74%, respectively). In addition, MSD-IAA demonstrated better sensitivity than our mIAA from blinded DASP workshop (68 vs. 56% with the same 99% specificity). Of 64 IAA(+) nondiabetic subjects, 25% (8 of 32) who had only IAA and thus the low risk for progression to diabetes were positive with MSD-IAA assay. In contrast, 100% (32 of 32) high-risk children (IAA plus other islet autoantibodies) were positive with MSD-IAA. The IAA detectable by radioassay, but not MSD-IAA, were usually of lower affinity compared with the IAA of the high-risk children. These data suggest that a subset of IAA with current radioassay (not MSD-IAA) represents biologic false positives in terms of autoimmunity leading to diabetes. We hypothesize that factors related to the mechanism of loss of tolerance leading to diabetes determine high affinity and MSD-IAA reactivity.

Investigation of the mechanism of clearance of AMG 386, a selective angiopoietin-1/2 neutralizing peptibody, in splenectomized, nephrectomized, and FcRn knockout rodent models

Purpose

To investigate the mechanisms of clearance of AMG 386, an investigational recombinant peptide-Fc fusion protein (peptibody) that blocks tumor angiogenesis by neutralizing the interaction between angiopoietin-1 and -2 and the Tie2 receptor.

Methods

The role of the neonatal Fc receptor (FcRn) in AMG 386 clearance was assessed in wild-type and FcRn-knockout mice; the roles of the spleen and kidneys were assessed in splenectomized and 5/6th nephrectomized rats, respectively, compared with sham-operated rats. Animals were administered AMG 386 as a single intravenous dose of 3 or 10 mg/kg. Blood samples for pharmacokinetic analysis were collected periodically throughout a 504-hour postdose period.

Results

Compared with wild-type mice, AMG 386 clearance in FcRn-knockout mice was 18-fold faster at the 3-mg/kg dose (FcRn knockout, 13.2 mL/h/kg; wild-type, 0.728 mL/h/kg) and 14-fold faster at the 10-mg/kg dose (FcRn knockout, 10.7 mL/h/kg; wild-type, 0.777 mL/h/kg). Clearance in nephrectomized rats was slower than in sham-operated rats at both the 3-mg/kg dose (nephrectomized, 1.23 mL/h/kg; sham-operated, 1.75 mL/h/kg) and the 10-mg/kg dose (nephrectomized, 1.14 mL/h/kg; sham-operated, 1.65 mL/h/kg). Splenectomy had no apparent effect on the pharmacokinetics of AMG 386.

Conclusions

The FcRn is integral to maintaining circulating levels of AMG 386 in mice. Renal clearance contributed approximately 30% to total AMG 386 clearance in rats.