Neutralizing Antibody Validation Testing and Reporting Harmonization.

Evolving immunogenicity assay performance expectations and a lack of harmonized neutralizing antibody validation testing and reporting tools have resulted in significant time spent by health authorities and sponsors on resolving filing queries. A team of experts within the American Association of Pharmaceutical Scientists' Therapeutic Product Immunogenicity Community across industry and the Food and Drug Administration addressed challenges unique to cell-based and non-cell-based neutralizing antibody assays. Harmonization of validation expectations and data reporting will facilitate filings to health authorities and are described in this manuscript. This team provides validation testing and reporting strategies and tools for the following assessments: (1) format selection; (2) cut point; (3) assay acceptance criteria; (4) control precision; (5) sensitivity including positive control selection and performance tracking; (6) negative control selection; (7) selectivity/specificity including matrix interference, hemolysis, lipemia, bilirubin, concomitant medications, and structurally similar analytes; (8) drug tolerance; (9) target tolerance; (10) sample stability; and (11) assay robustness.

Immunogenicity assessment of AAV-based gene therapies: An IQ consortium industry white paper.

Immunogenicity has imposed a challenge to efficacy and safety evaluation of adeno-associated virus (AAV) vector-based gene therapies. Mild to severe adverse events observed in clinical development have been implicated with host immune responses against AAV gene therapies, resulting in comprehensive evaluation of immunogenicity during nonclinical and clinical studies mandated by health authorities. Immunogenicity of AAV gene therapies is complex due to the number of risk factors associated with product components and pre-existing immunity in human subjects. Different clinical mitigation strategies have been employed to alleviate treatment-induced or -boosted immunogenicity in order to achieve desired efficacy, reduce toxicity, or treat more patients who are seropositive to AAV vectors. In this review, the immunogenicity risk assessment, manifestation of immunogenicity and its impact in nonclinical and clinical studies, and various clinical mitigation strategies are summarized. Last, we present bioanalytical strategies, methodologies, and assay validation applied to appropriately monitor immunogenicity in AAV gene therapy-treated subjects.

Characterization of the robust humoral immune response to GSK2618960, a humanized anti-IL-7 receptor monoclonal antibody, observed in healthy subjects in a Phase 1 study.

Interleukin-7 (IL-7) signaling modulates T cell activity and is implicated in numerous autoimmune diseases. An anti-IL-7 receptor monoclonal antibody (GSK2618960) biotherapeutic was evaluated in healthy subjects for safety, pharmacokinetics (PK), pharmacodynamics (PD) and immunogenicity in a single-dose escalation phase I study. We found that antibodies against GSK2618960 (i.e., anti-drug antibodies or ADA) developed in 83% and 100% of GSK2618960-treated subjects in the 0.6 and 2.0 mg/kg dose cohorts, respectively. Of the ADA positive subjects, 64% (7 of 11) had detectable neutralizing activity. Further investigation revealed the presence of GSK2618960-specific memory B cells, indicating the development of immunological memory for the ADAs. Ex vivo stimulation of peripheral blood mononuclear cell (PBMC) samples demonstrated a relatively strong CD4+ T cell proliferation response to GSK2618960 as compared to the control anti-RSV antibody (which is known to have only low immunogenic potential), confirming the high immunogenic potential of GSK2618960. Furthermore, GSK2618960 was found to bind in vitro monocyte-derived dendritic cells (DCs). GSK2618960 treatment of PBMCs increased the proportion of DC cells showing an increase in expression of CD83, CD86 and CD209, which indicated enhanced DC differentiation and activation relative to the isotype control anti-ß amyloid antibody. Collectively, the evidence supports that the high incidence of observed clinical immunogenicity was likely related to the receptor-mediated activity by GSK2618960.

Toward Reference Intervals of ARSA Activity in the Cerebrospinal Fluid: Implication for the Clinical Practice of Metachromatic Leukodystrophy.

BACKGROUND: Cerebrospinal fluid (CSF) has emerged as a sensitive matrix for the screening of biomarkers for diagnosis and clinical follow-up of diseases with neurological manifestations, including some lysosomal storage disorders. In this study, we assessed the range of values of arylsulfatase A (ARSA) activity in the CSF of pediatric and adult donors, and in pediatric patients who underwent gene therapy for metachromatic leukodystrophy (MLD). METHODS: A cohort of 56 CSF samples was included in the study: pediatric donors (n = 36), adult donors (n = 9), and MLD patients (n = 11) at different timepoints [pre-gene therapy (GT), post-GT + 1 Year, post-GT + 2 Years, post-GT + 3 Years]. We have used our fluorometric assay for the determination of ARSA activity. The total protein content in the samples was also evaluated. RESULTS: We discovered that ARSA activity was higher in pediatric donors (geometric mean: 1.039 nmol/mg/h; 95% range: 0.859-1.258 nmol/mg/h) compared to adults (geometric mean: 0.305 nmol/mg/h; 95% range: 0.214-0.435 nmol/mg/h). No ARSA activity was detected in the CSF of MLD patients pre-GT, whereas ARSA activity was stably expressed and almost restored to range of values of pediatric donors in MLD patients post-GT + 3 Years with a geometric mean of 0.822 nmol/mg/h (95% range: 0.580-1.165 nmol/mg/h). CONCLUSIONS: This study establishes range of values of ARSA activity in the CSF for MLD clinical practice. The observed ranges of ARSA activities in CSF exhibited an unpredicted age dependence and, in turn, revealed the need of using pediatric ARSA activity for evaluating the restoration of the enzyme activity during the therapy of MLD.

Immunogenicity Risk Assessment for PEGylated Therapeutics.

The objective of this manuscript is to provide the reader with two examples on how to present an immunogenicity risk assessment for a PEGylated therapeutic as part of Investigational New Drug (IND) application or during other stages of the drug development process. In order to provide context to the bioanalytical strategies used to support the PEGylated therapeutics presented here, a brief summary of information available for marketed PEGylated biologics is provided. Two case studies are presented, a PEGylated enzyme and a PEGylated growth factor. For the former, the risk assessment covers how to deal with a narrow therapeutic window and suggestions to utilize a PD marker as surrogate for neutralizing antibody assessments in Phase I. The latter has recommendations on additional analytes that should be monitored to mitigate risk of immunogenicity to endogenous counterparts.

A Study to Investigate the Efficacy and Safety of an Anti-Interleukin-18 Monoclonal Antibody in the Treatment of Type 2 Diabetes Mellitus.

OBJECTIVE: Evidence suggests that chronic subclinical inflammation plays an important role in the pathogenesis of type 2 diabetes (T2DM). Circulating levels of interleukin (IL)-18 appear to be associated with a number of micro- and macrovascular comorbidities of obesity and T2DM. This study was designed to investigate whether inhibition of IL-18 had any therapeutic benefit in the treatment of T2DM. Preliminary efficacy, safety and tolerability, pharmacokinetics, and pharmacodynamics of the anti-IL-18 monoclonal antibody, GSK1070806, were assessed. RESEARCH DESIGN AND METHODS: This was a multicentre, randomized, single-blind (sponsor-unblinded), placebo-controlled, parallel-group, phase IIa trial. Obese patients of either sex, aged 18-70 years, with poorly controlled T2DM on metformin monotherapy were recruited. Patients received two doses, of placebo (n = 12), GSK1070806 0.25 mg/kg (n = 13) or GSK1070806 5 mg/kg (n = 12). The primary end-point was the change from baseline in fasting plasma glucose and weighted mean glucose area under the curve (AUC)(0-4 hours) postmixed meal test on Days 29, 57, and 85. RESULTS: Thirty-seven patients were randomized to one of the three treatment arms. There were no statistically significant effects of GSK1070806 doses on fasting plasma glucose levels, or weighted mean glucose AUC(0-4 hours) compared with placebo. CONCLUSIONS: GSK1070806 was well tolerated, and inhibition of IL-18 did not lead to any improvements in glucose control. However, because of study limitations, smaller, potentially clinically meaningful effects of IL-18 inhibition cannot be excluded. TRIAL REGISTRATION: ClinicalTrials.gov NCT01648153.

Safety, tolerability, pharmacokinetics, and pharmacodynamics of single-dose antiinterleukin- 18 mAb GSK1070806 in healthy and obese subjects.

OBJECTIVE: To investigate the safety, tolerability, pharmacokinetics, and pharmacodynamics of GSK1070806, a novel IgG1 mAb that neutralizes human interleukin (IL)-18. METHODS: In this first-timein-human (FTIH) study, cohorts of healthy and obese subjects were randomly allocated to receive single doses of GSK1070806 (0.008 - 10 mg/kg) or placebo. Blood was sampled ≤ 274 days post-dosing, and safety monitored. RESULTS: GSK1070806 was generally well tolerated. The most common AEs were nasopharyngitis and headache, arising as frequently in the placebo as in the active drug groups; most AEs were mild to moderate and unrelated to dose level. There were no allergic, delayed-type hypersensitivity, or infusion-related reactions and the incidence of immunogenicity was low. GSK1070806 plasma pharmacokinetic profiles were comparable in healthy and obese subjects; there was no major deviation from dose proportionality for AUC(∞) and C(max) although a trend for dose-dependent increase in t(1/2) was observed. Serum drug-bound IL-18 levels increased post-dosing and were sustained for a long time-period following GSK1070806 administration. Ex-vivo whole blood assay demonstrated prolonged pharmacological activity of GSK1070806 as determined by its primary immunological mechanism of action, inhibition of IL-18-induced IFN-γ production. CONCLUSION: GSK1070806 warrants clinical investigation in patients.

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.

Development and validation of a cell-based SEAP reporter assay for the detection of neutralizing antibodies against an anti-IL-13 therapeutic antibody.

A cell-based bioassay capable of detecting neutralizing antibodies (NAb) specific to a therapeutic anti-IL-13 monoclonal antibody was developed, validated and used to analyze normal human and asthma serum samples. At the time of this study, a neutralizing assay was unavailable for anti-IL-13 antibody therapeutics with sufficient rigor for validation. Thus, we describe here a method and considerations for validation. The assay used IL-13 responsive HEK293 cells transfected with a secreted embryonic alkaline phosphatase (SEAP) reporter gene. Cells were plated at 5.4×10(4) per assay well due to 90% confluence on the subsequent day. Optimal IL-13 and anti-IL-13 concentrations were determined to be 600 pg/mL and 900 ng/mL respectively. We demonstrated the assay's cut point, sensitivity, specificity/cross reactivity, selectivity/matrix interference, and precision. Also, we demonstrated how the drug inhibitory concentration (IC(50), IC(75), and IC(90)) can affect sensitivity and dynamic range/assay window. We characterized the differences in assay response between serum samples of normal population and asthma population. Asthma samples demonstrated an elevated OD ratio in average compared to normal samples. Thus, separate cut points were needed and calculated to be 1.78 and 2.43 for normal and asthma serum, respectively. The assay sensitivity was 670 ng/mL with the positive control (affinity purified rabbit anti-drug polyclonal antibodies). Potential false positives resulting from endogenous serum cytokines including IL-13, IL-4, and Interferon alpha (INF-α) were evaluated and the results indicated that the interfering concentrations for these cytokines are much higher than the respective physiological concentrations. Based on these data, the risk of false positive by endogenous cytokines was considered to be low. In addition, irrelevant anti-drug positive control antibodies were evaluated for assay specificity and did not demonstrate neutralizing capability. Further, no matrix interference in the intended patient population was found when using a final assay serum concentration of 16.7%. The validated assay had acceptable intra- and inter- assay precision in that all %CVs were ≤25%. Overall, this assay successfully proceeded through validation and was used to determine NAb responses within serum samples.