Lakshmi Amaravadi

Recommendations for the validation of immunoassays used for detection of host antibodies against biotechnology products

Most biological drug products elicit some level of anti-drug antibody (ADA) response. This antibody response can, in some cases, lead to potentially serious side effects and/or loss of efficacy. In humans, ADA often causes no detectable clinical effects, but in the instances of some therapeutic proteins these antibodies have been shown to cause a variety of clinical consequences ranging from relatively mild to serious adverse events. In nonclinical (preclinical) studies, ADA can affect drug exposure, complicating the interpretation of the toxicity, pharmacokinetic (PK) and pharmacodynamic (PD) data. Therefore, the immunogenicity of therapeutic proteins is a concern for clinicians, manufacturers and regulatory agencies. In order to assess the immunogenic potential of biological drug molecules, and be able to correlate laboratory results with clinical events, it is important to develop reliable laboratory test methods that provide valid assessments of antibody responses in both nonclinical and clinical studies. For this, method validation is considered important, and is a necessary bioanalytical component of drug marketing authorization applications. Existing regulatory guidance documents dealing with the validation of methods address immunoassays in a limited manner, and in particular lack information on the validation of immunogenicity methods. Hence this article provides scientific recommendations for the validation of ADA immunoassays. Unique validation performance characteristics are addressed in addition to those provided in existing regulatory documents pertaining to bioanalyses. The authors recommend experimental and statistical approaches for the validation of immunoassay performance characteristics; these recommendations should be considered as examples of best practice and are intended to foster a more unified approach to antibody testing across the biopharmaceutical industry.

Immunogenicity of biologically-derived therapeutics: Assessment and interpretation of nonclinical safety studies

An evaluation of potential antibody formation to biologic therapeutics during the course of nonclinical safety studies and its impact on the toxicity profile is expected under current regulatory guidance and is accepted standard practice. However, approaches for incorporating this information in the interpretation of nonclinical safety studies are not clearly established. Described here are the immunological basis of anti-drug antibody formation to biopharmaceuticals (immunogenicity) in laboratory animals, and approaches for generating and interpreting immunogenicity data from nonclinical safety studies of biotechnology-derived therapeutics to support their progression to clinical evaluation. We subscribe that immunogenicity testing strategies should be adapted to the specific needs of each therapeutic development program, and data generated from such analyses should be integrated with available clinical and anatomic pathology, pharmacokinetic, and pharmacodynamic data to properly interpret nonclinical studies.

Mice deficient in fractalkine are less susceptible to cerebral ischemia-reperfusion injury

Fractalkine (FKN), also known as neurotactin, is a CX(3)C chemokine that exists in both secreted and neuronal membrane-bound forms and is upregulated during brain inflammation. There is accumulating evidence that FKN induces chemotaxis by binding to its receptor CX(3)CR1 on leukocytes and microglia. We generated FKN-deficient mice to study the role of FKN in postischemic brain injury. After transient focal cerebral ischemia, FKN-deficient mice had a 28% reduction in infarction size and lower mortality rate, when compared to wild-type littermates. The findings of this study indicate a possible role for FKN in augmenting postischemic injury and mortality after transient focal cerebral ischemia.

Solution ELISA as a platform of choice for development of robust, drug tolerant immunogenicity assays in support of drug development

Humanized monoclonal antibody therapeutics are in many ways indistinguishable from the anti-therapeutic/anti-drug antibodies generated in humans. Therefore, immunogenicity assessments to such therapeutics pose unique challenges in clinical trials especially when significant drug interference is encountered. There are several technology platforms based on the bridging immunogenicity assay format, which have been successfully used for detection and quantification of anti-drug antibodies (ADA) in serum or plasma samples. Enzyme-Linked Immunosorbent Assay (ELISA) and Electrochemiluminescent (ECL) immunoassay formats are among the most popular technology platforms. Pretreatment of samples with acid can also be used to lower drug interference. While ECL technology platform offered many advantages over traditional solid-phase ELISA methods, reliance on a single (or limited) vendor source became a significant concern within the biopharmaceutical industry especially for immunogenicity assays that need to be implemented over a period of many years in support of a single drug development program. We describe herein a systematic evaluation of solid-phase ELISA, GYROS, AlphaLISA, ECL Immunoassay, and solution ELISA platforms for detection of anti-drug antibodies with the goal of selection and development of a robust technology platform that meets the desired performance characteristics for most immunogenicity assays and can be easily implemented in a typical immunoassay laboratory. As part of this effort the Design of Experiments (DOE) approach was utilized in optimization of sample acid treatment conditions in order to improve drug tolerance in the evaluated assay platforms. After the initial evaluation of various technology platforms, a solution ELISA format was chosen for further development to support clinical trials for a humanized therapeutic antibody. As part of the assay development, flexible use of digoxigenin and 6-(2,4-dinitrophenyl) aminohexanoic acid (DNP) for labeling antibodies was evaluated and is presented in this manuscript. In addition, simple methods for evaluation and qualification of streptavidin-coated plates and overcoming soluble target interference in solution ELISA have also been investigated and highlights of these investigations are discussed. The selection of the solution ELISA format was based on availability of generic reagents, achievement of optimal drug tolerance and robust assay performance on a platform that is readily available in many laboratories. This approach removed the heavy reliance on specialized equipment sourced from a single vendor and assay conditions described here are broadly applicable to other immunogenicity assays across many biologics both during clinical development setting and in the post-marketing arena.

Daclizumab high-yield process in relapsing-remitting multiple sclerosis (SELECTION): a multicentre, randomised, double-blind extension trial

BACKGROUND In the SELECT trial, disease activity was reduced in patients with multiple sclerosis who received daclizumab high-yield process (HYP) for 52 weeks. The primary aim of the SELECTION extension study was to assess the safety and immunogenicity of extended treatment with daclizumab HYP. METHODS A multicentre, randomised, double-blind, 52-week extension trial was done in 74 centres in the Czech Republic, Germany, Hungary, India, Poland, Russia, Ukraine, and the UK between Feb 13, 2009, and Oct 3, 2012. Eligible patients were aged 18-55 years, had relapsing-remitting multiple sclerosis, and had completed the SELECT study. Patients who received placebo in SELECT were randomly assigned (1:1) to receive 150 mg or 300 mg subcutaneous daclizumab HYP every 4 weeks for 52 weeks (treatment initiation group); those who had received daclizumab HYP were randomly assigned (1:1) to continue their present dose with (washout and re-initiation group) or without (continuous treatment group) a washout period of 20 weeks. All randomisation was done with a centralised, interactive voice-response system. Patients and personnel were masked to treatment assignment, except for the site pharmacist who prepared the study drug but had no interaction with patients. The primary endpoints were the safety and immunogenicity of daclizumab HYP. Analyses were by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00870740. FINDINGS 517 (91%) of 567 patients who completed the SELECT trial entered SELECTION, of whom 170 were in the treatment initiation group, 173 in the continuous treatment group, and 174 in the washout and re-initiation group. 11 patients in the treatment initiation group (6%), 13 in the continuous treatment group (8%), and ten in the washout and re-initiation group (6%) had any serious adverse event other than relapse of multiple sclerosis. One patient in the washout and re-initiation group (300 mg daclizumab HYP) died because of autoimmune hepatitis; a contributory role of daclizumab HYP could not be excluded. Seven patients tested positive for neutralising antidrug antibodies: one (1%) of 128 for whom data were available in the continuous treatment group (this patient also tested positive at SELECTION baseline), four (2%) in the treatment initiation group, and two (2%) of 129 in the washout and re-initiation group. INTERPRETATION Adverse events and immunogenicity were not increased in the second year of continuous treatment with daclizumab HYP or during treatment washout and re-initiation. These results support further assessment of daclizumab HYP for relapsing-remitting multiple sclerosis. FUNDING Biogen Idec and AbbVie Biotherapeutics.

Workshop Report: Crystal City V—Quantitative Bioanalytical Method Validation and Implementation: The 2013 Revised FDA Guidance

In September 2013, the FDA released a draft revision of the Bioanalytical Method Validation (BMV) Guidance, which included a number of changes to the expectations for bioanalysis, most notably the inclusion of biomarker assays and data. To provide a forum for an open, inclusive discussion of the revised draft BMV Guidance, the AAPS and FDA once again collaborated to convene a two-and-a-half day workshop during early December 2013 in Baltimore, MD, USA. The resulting format embodied extensive open discussion and each thematic session included only brief, concise descriptions by Agency and industry representatives prior to opening the floor discussion. The Workshop was built around four thematic sessions (Common Topics, Chromatographic, Ligand-Binding Assays, and Biomarkers) and a final session with international regulators, concluding with a review of the outcomes and recommendations from the thematic sessions. This Workshop report summarizes the outcomes and includes topics of agreement, those where the FDA will consider the Industry’s perspective, and those where the workshop provided a first open dialogue. This article will be available to the bioanalytical community at http://www.aaps.org/BMV13.

A White Paper—Consensus and Recommendations of a Global Harmonization Team on Assessing the Impact of Immunogenicity on Pharmacokinetic Measurements

The Global Bioanalysis Consortium (GBC) set up an international team to explore the impact of immunogenicity on pharmacokinetic (PK) assessments. The intent of this paper is to define the field and propose best practices when developing PK assays for biotherapeutics. We focus on the impact of anti-drug antibodies (ADA) on the performance of PK assay leading to the impact on the reported drug concentration and exposure. The manuscript describes strategies to assess whether the observed change in the drug concentration is due to the ADA impact on drug clearance rates or is a consequence of ADA interference in the bioanalytical method applied to measure drug concentration. This paper provides the bioanalytical scientist guidance for developing ADA-tolerant PK methods. It is essential that the data generated in the PK, ADA, pharmacodynamic and efficacy/toxicity evaluations are viewed together. Therefore, the extent for the investigation of the PK sensitivity to the presence of ADA should be driven by the project needs and risk based.

Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Anti-TWEAK Monoclonal Antibody in Patients With Rheumatoid Arthritis

BACKGROUND Persistent upregulation of signaling by cytokine tumor necrosis factor-like weak inducer of apoptosis (TWEAK) through its receptor fibroblast growth factor-inducible molecule-14 (Fn14) promotes chronic inflammation and tissue destruction. OBJECTIVE The aim of this study was to explore the safety and tolerability of the TWEAK-blocking monoclonal antibody BIIB023 and determine its pharmacokinetics and effects on TWEAK pathway pharmacodynamic markers in rheumatoid arthritis (RA). METHODS Phase I, first-in-human, 2-part, multicenter, double-blind, dose-escalation study. Patients were randomized to a single dose of BIIB023 (0.03-20 mg/kg) (n = 38) or placebo (n = 15) as an add-on to methotrexate. Three open-label cohorts of RA patients taking background disease-modifying antirheumatic drugs and stable tumor necrosis factor (TNF) inhibitor therapy (n = 12) received a single-dose of BIIB023 of 2, 10, or 20 mg/kg and were assessed over 70 days. RESULTS The incidence of treatment-emergent adverse events for the BIIB023 monotherapy cohorts and open-label cohorts of BIIB023 as add-on therapy to TNF inhibitors compared with placebo were 47% and 50% versus 33%, respectively. Serum exposure to BIIB023 increased in a dose-dependent manner from 0.03 to 20 mg/kg, but not in direct proportion to dose level. After administration, the time course of BIIB023 serum concentration was multiphasic and showed expedited elimination when levels decreased to < 10 µg/mL. Serum-soluble TWEAK levels were suppressed at all dose levels by 6 hours post-dose and recovered to baseline between days 7 and 28. A trend toward downward modulation of serum biomarkers of inflammatory response was suggested in monocyte chemoattractant protein 1, inducible protein 10, macrophage inflammatory protein 1β, and tissue inhibitor of metalloproteinase 1 in the BIIB023 group versus placebo. CONCLUSIONS Single-dose BIIB023 showed a favorable safety and tolerability profile in RA. Suppression of serum-soluble TWEAK for ≤ 28 days was observed and downward trends in serum biomarkers suggested.

In Vivo Maintenance of Human Regulatory T Cells during CD25 Blockade

Regulatory T cells (Tregs) mediate immune tolerance to self and depend on IL-2 for homeostasis. Treg deficiency, dysfunction, and instability are implicated in the pathogenesis of numerous autoimmune diseases. There is considerable interest in therapeutic modulation of the IL-2 pathway to treat autoimmunity, facilitate transplantation tolerance, or potentiate tumor immunotherapy. Daclizumab is a humanized mAb that binds the IL-2 receptor α subunit (IL-2Rα or CD25) and prevents IL-2 binding. In this study, we investigated the effect of daclizumab-mediated CD25 blockade on Treg homeostasis in patients with relapsing-remitting multiple sclerosis. We report that daclizumab therapy caused an ∼50% decrease in Tregs over a 52-wk period. Remaining FOXP3+ cells retained a demethylated Treg-specific demethylated region in the FOXP3 promoter, maintained active cell cycling, and had minimal production of IL-2, IFN-γ, and IL-17. In the presence of daclizumab, IL-2 serum concentrations increased and IL-2Rβγ signaling induced STAT5 phosphorylation and sustained FOXP3 expression. Treg declines were not associated with daclizumab-related clinical benefit or cutaneous adverse events. These results demonstrate that Treg phenotype and lineage stability can be maintained in the face of CD25 blockade.

New FDA Draft Guidance on Immunogenicity

A “Late Breaking” session was held on May 20 at the 2013 American Association of Pharmaceutical Scientists-National Biotech Conference (AAPS-NBC) to discuss the US Food and Drug Administration’s (FDA) 2013 draft guidance on Immunogenicity Assessment for Therapeutic Protein Products. The session was initiated by a presentation from the FDA which highlighted several key aspects of the 2013 draft guidance pertaining to immunogenicity risk, the potential impact on patient safety and product efficacy, and risk mitigation. This was followed by an open discussion on the draft guidance which enabled delegates from biopharmaceutical companies to engage the FDA on topics that had emerged from their review of the draft guidance. The multidisciplinary audience fostered an environment that was conducive to scientific discussion on a broad range of topics such as clinical impact, immune mitigation strategies, immune prediction and the role of formulation, excipients, aggregates, and degradation products in immunogenicity. This meeting report highlights several key aspects of the 2013 draft guidance together with related dialog from the session.