Successful Development of Nonclinical Anti-Drug Antibody Assays to Support Zinpentraxin Alfa Reproductive Toxicology Studies.

Immunogenicity assessment is an essential part of biotherapeutic drug development. While the immune response in animals is not always representative of the human immune response, immunogenicity data obtained in animal models is still informative for the evaluation of drug exposure and safety. The most common assay format used for the detection of anti-drug antibodies (ADAs) in preclinical and clinical studies is the bridging format. The advantage of this method is that it can detect all antibody isotypes generated against the therapeutic. However, the method development can be time-consuming and labor-intensive, due to the need for labeling of the drug which is used both as capture and detection. Various generic ADA assays have been successfully implemented to overcome these disadvantages and to enable faster assay development timelines to support nonclinical toxicology studies. Here, we describe the challenges in the development of an assay to detect antibodies to zinpentraxin alfa, a recombinant human pentraxin-2, in rabbit and rat toxicology studies. Our initial efforts to develop a bridging assay failed, prompting us to develop a method adapted from generic assay formats to detect anti-zinpentraxin alfa antibodies in the serum of different species with minimal optimization. However, while the general assay format remained similar, assay reagents were adapted between the different species, resulting in the development of two distinct assays for the detection of ADAs in rat and rabbit. Here, we share the final development/validation data and the immunogenicity study results. Our work highlights the need for the evaluation of alternate assay formats when evaluating novel drug modalities.

Evaluation of multiple immunoassay formats for detection of anti-drug antibodies to zinpentraxin alfa.

Zinpentraxin alfa (rhPTX-2; PRM-151) is currently being developed for the treatment of fibrotic diseases such as idiopathic pulmonary fibrosis and myelofibrosis. Notably, because it is administered chronically and has an endogenously expressed counterpart, clinical studies of zinpentraxin alpha must include immunogenicity assessments. Since the typical homogenous bridging ELISA assay does not adequately measure anti-drug antibodies (ADAs) against zinpentraxin alfa, additional assay formats have been developed to evaluate immunogenicity of this therapeutic. Here, we present the evaluation of four distinct assay formats that were used to measure zinpentraxin alpha ADA: step-wise bridging, direct binding, total ADA, and the semi-homogeneous formats, based on multiple parameters including assay sensitivity, precision, and drug tolerance. This paper presents the full details of method development for each of the aforementioned assay formats including evaluation of sample pre-treatment, determination of cut point, and assessment of assay performance by analyzing a subset of clinical samples. Overall, the semi-homogenous ADA assay format with no sample pre-treatment was selected for the measurement of zinpentraxin alpha immunogenicity as it provided the desired sensitivity, drug tolerance, and reproducibility. Our study emphasizes the importance of assay format evaluation during drug development and the necessity to select the most suitable assay format and sample pre-treatment method by which to evaluate therapeutic drug immunogenicity.

An integrated approach for characterizing immunogenic responses toward a bispecific antibody.

Bispecific antibodies (bsAbs) recognize and bind two different targets or two epitopes of the same antigen, making them an attractive diagnostic and treatment modality. Compared to the production of conventional bivalent monospecific antibodies, bsAbs require greater engineering and manufacturing. Therefore, bsAbs are more likely to differ from endogenous immunoglobulins and contain new epitopes that can increase immunogenic risk. Anti-A/B is a bsAb designed using a 'knobs-into-holes' (KIH) format. Anti-A/B exhibited an unexpectedly high immunogenicity in both preclinical and clinical studies, resulting in early termination of clinical development. Here, we used an integrated approach that combined in silico analysis, in vitro assays, and an in vivo study in non-human primates to characterize anti-A/B immunogenicity. Our findings indicated that the immunogenicity is associated with epitopes in the anti-B arm and not with mutations engineered through the KIH process. Our results showed the value of this integrated approach for performing immunogenicity risk assessment during clinical candidate selection to effectively mitigate risks during bsAb development.

Characterization of robust immune responses to a bispecific antibody, a novel class of antibody therapeutics.

Background: Anti-A/B is a bispecific monoclonal antibody that blocks activities of soluble targets A and B. Robust immune responses were observed in a multiple-dose cynomolgus monkey toxicology study, negatively impacting the toxicokinetics/pharmacodynamics profile of anti-A/B in some animals. This was unexpected as similar findings were not observed in the two previously studied parental molecules. Methodology & Results: This paper discusses our characterization strategy for evaluating the immunogenic domain(s) of anti-A/B and our mitigation plan to monitor immunogenicity in the first-in-human clinical study. The characterization results from the cynomolgus monkey and Phase I studies are discussed. Conclusion: The characterization strategy discussed informed understanding of immunogenicity results and clinical impact, which can be broadly applied to other molecules with multiple-binding domains.

Measurement of IL-17AA and IL-17FF as Pharmacodynamic Biomarkers to Demonstrate Target Engagement in the Phase I Study of MCAF5352A.

The interleukin (IL)-17 pathway has been implicated in the pathophysiology of many autoimmune diseases. MCAF5352A is a humanized monoclonal antibody which targets both IL-17A and IL-17F, thereby inhibiting the activity of IL-17 dimers (IL-17AA, IL-17AF, and IL-17FF). The pharmacokinetic profile of MCAF5352A has been characterized in both a Phase Ia single ascending dose study and a Phase Ib multiple ascending dose study. Two qualified enzyme-linked immunosorbent assays were used to measure total IL-17AA and IL-17FF levels in serum as pharmacodynamic biomarkers in the Phase I studies. The two assays demonstrated specificity for IL-17AA or IL-17FF with sensitivity at low picogram/milliliter levels. The assay precision and accuracy also met acceptance criteria. Although total serum IL-17AA and IL-17FF levels were below the assay detection limits prior to administration of MCAF5352A, post-treatment levels in both the single and multiple dose cohorts became detectable and increased in a dose-dependent manner. These data are consistent with target engagement by MCAF5352A. Our work highlights bioanalytical challenges encountered while developing biomarker assays requiring high sensitivity and specificity. Data generated using these assays enabled the confirmation of target engagement during early clinical drug development.

Relation of increased prebeta-1 high-density lipoprotein levels to risk of coronary heart disease.

Preß-1 high-density lipoprotein (HDL) plays a key role in reverse cholesterol transport by promoting cholesterol efflux. Our aims were (1) to test previous associations between preß-1 HDL and coronary heart disease (CHD) and (2) to investigate whether preß-1 HDL levels also are associated with risk of myocardial infarction (MI). Plasma preß-1 HDL was measured by an ultrafiltration-isotope dilution technique in 1,255 subjects recruited from the University of California-San Francisco Lipid and Cardiovascular Clinics and collaborating cardiologists. Preß-1 HDL was significantly and positively associated with CHD and MI even after adjustment for established risk factors. Inclusion of preß-1 HDL in a multivariable model for CHD led to a modest improvement in reclassification of subjects (net reclassification index 0.15, p = 0.01; integrated discrimination improvement 0.003, p = 0.2). In contrast, incorporation of preß-1 HDL into a risk model of MI alone significantly improved reclassification of subjects (net reclassification index 0.21, p = 0.008; integrated discrimination improvement 0.01, p = 0.02), suggesting that preß-1 HDL has more discriminatory power for MI than for CHD in our study population. In conclusion, these results confirm previous associations between preß-1 HDL and CHD in a large well-characterized clinical cohort. Also, this is the first study in which preß-1 HDL was identified as a novel and independent predictor of MI above and beyond traditional CHD risk factors.

Clinical immunogenicity specificity assessments: a platform evaluation.

Immunogenicity assessment is an integral part of the evaluation of the safety and efficacy for protein therapeutics during drug development, and is required by the regulatory authorities. A tiered strategy is typically utilized to assess immunogenicity and is often comprised of a screening method, a confirmation/specificity step and a characterization step. To ensure methods with appropriate sensitivity are utilized, the threshold for screening assays is set to minimize false negatives resulting in a certain rate of false positivity. The confirmatory step is critical for determining assay specificity and eliminating false positives identified in the screening assay. Using a widely implemented technology and bridging assay format commonly used for immunogenicity assessments, unacceptably poor specificity was observed for the confirmatory/specificity step for a subset of monoclonal antibodies in our group. Therefore, we believe that this challenge will be relevant to others in the field. In this paper, we will describe our challenges with one of these antibodies, monoclonal antibody therapeutic X (rhuMAb X). This paper presents extensive evaluation of two technology platforms and various conditions to evaluate and provide solutions to improving the assay specificity in the immunogenicity assessment of antibody therapeutics.