Importance of Immunogenicity Investigations in Clinical Development of Antibody Treatments Dr. Anke Domdey, Ando ApS - Bioanalytical Outsourcing 26th September 2018
Topics • Drug-induced Immunogenicity • Biological Effects of Immune Complexes • Clinical Relevance • Regulatory Guidelines • Examples from Day-to-Day Business • Take Home Messages
Immunogenicity is antigenicity resulting in a humoral response
Drug-induced immunogenicity is elicitation of anti-drug antibodies (ADAs)
Drug size and structures not belonging to the patient´s self-repertoir are at risk of being recognized as foreign by the host immune system
Formation of ADAs is subject to high individual variability – influence factors Dose Administration regimen Administration route Other medical treatments Patient´s immune status Genetic factors
ADA bound to drug gives rise to immune complexes (ICs) that may impact drug safety and efficacy Safety
ADA-drug ICs
Composition and size of ICs have different biological implications • Recognition of the functional portion of the drug leads to abrogation of the pharmacological activity (NAb) • Binding to pharmacologically irrelevant portions and/or NAbs may impact the clearance of a drug • Moderate and smaller complexes persist longer in the circulation, while larger complexes are picked up earlier by marcrophages.
Composition and size of ICs have different biological implications • Less severe infusion-site reactions seen during the first infusion (non-allergic) • IgE isotype ADAs are formed during an initial response and upon repeat exposure, IgE bound complexes drive release of histamine, and manifestation of anaphylactic reactions (type I hypersensitivity). • Type II hypersensitivity is mediated by IgM or IgG targeting membrane-associated antigens leading to cellular destruction by phagocytosis, complement-dependent cytotoxicity (CTC) and antibody-dependent cell-mediated cytotoxicity (ADCC). • Type III hypersensitivity reactions are inflammatory responses triggered by circulating immune complexes (CICs) that deposit in various tissues.
Clinical relevance has not consistently been shown across antibody therapeutics ďƒ˜ADA responses to anti-TNF-a biologics, e.g. adalimumab and infliximab, were linked to clinically manifest adverse events, while ADA responses to etanercept, golimumab and certolizumab have not conclusively shown a link to clinical response. ďƒ˜Development of ADA and its role in serious side effects was described for recombinant biologics like IFNs, erythropoietin, thrombopoietin and Factor IX.
Clinical relevance in cancer therapeutics For most registered biological anticancer drugs, only a low percentage of patients form ADAs: Cetuximab (3.4%), Trastuzumab (8%), Rituximab (1-2%) Immune checkpoint inhibitors have low immunogenicity, but a combination of nivolumab with ipilimumab leads to higher percentage of ADA formation (22 vs. 10% in monotherapy) Brentuximab-vedotin (drug-toxin conjugate) and catumaxomab (murine mAb) induce ADAs in 35% to 94% of patients.
The detection of ADAs depends on the quality of the assay and in many cases the effects on PK, efficacy and safety were not investigated.
Regulatory guidelines
Regulatory guidelines – testing scheme for ADAs
Regulatory guidelines – Assay validation
Parameterv
Definition
Sensitivity • Assay Sensitivity
Represents the lowest concentration at which the antibody produces either a positive result or readout equal to the cut-point determined for that particular assay. FDA recommends that screening and confirmatory ADA assays achieve a sensitivity of at least 0.1µg/mL.
•
Drug Tolerance
Specificity and Selectivity
The assessment of assay sensitivity in the presence of the expected levels of interfering therapeutic protein product, also known as the assay’s drug tolerance, is critical to understanding the suitability of the method or detecting ADA in dosed patients. The sponsor may examine drug tolerance by deliberately adding different known amounts of purified ADA into individual ADA-negative control samples in the absence or presence of different quantities of the therapeutic protein product under consideration and determining quantitatively whether the therapeutic protein product interfere with ADA detection. The selectivity of an ADA assay its ability to identify therapeutic protein product-specific ADA in a matrix such as serum or plasma that may contain potential interfering substances.
Matrix Interference
The sponsor may examine matrix interference by spiking different known amounts of purified ADA into the assay buffer in the absence or presence of different matrix components. Comparing the recovery of ADA in buffer alone with that in the matrix can provide input on the degree of interference from matrix components.
MRD
Matrix components can contribute to non-specific signal if undiluted, thereby obscuring positive results. Therefore, there is frequently a need to dilute patient samples to maintain a reasonable ability to detect ADA (sensitivity). Ideally, the MRD is the sample dilution that yields a signal close to that of the assay diluent and allows for the highest signal-to-noise ratio. MRD typically ranges from 1:5 to 1:100.
Precision
Precision is a measure of the variability in a series of measurements for the same material run in a method. Results should be reproducible within and between assay runs to assure adequate precision. To provide reliable estimates, the sponsor should evaluate both intra-assay (repeatability) and inter-assay (intermediate precision) variability of assay responses.
Reproducibility Robustness and Sample Stability
Reproducibility is an important consideration if an assay will be run by two or more independent laboratories during a study, and a sponsor should establish the comparability of the data produced by each laboratory. Assay robustness is an indication of the assay’s reliability during normal usage and is assessed by the capacity of the assay to remain unaffected by small but deliberate variations in method and instrument performance that would be expected under relevant, real-life circumstances in routine laboratory practice. FDA recommends storing patient samples in a manner that preserves antibody reactivity at the time of testing. FDA recommends that the sponsor avoid freeze-thaw cycles because freezing and thawing patient samples may also affect assay results. However, studies evaluating long-term stability of positive control antibodies may be useful.
Experiences from day-to-day business (1) Bioanalytical assay development & validation falls behind within the course of clinical development of biopharmaceutics: • Assay performance may be insufficient • Assay validity may be questionable
incidence rate
of ADA formation uncertain
Proper assessment of a potential impact of ADA formation on the PK/ efficacy of a therapeutic antibody not possible
Experiences from day-to-day business (2) The purpose of an assay may change throughout the clinical development of a biopharmaceutic • From Immunogenicity investigation to treatment decision criterion
The assay is considered a new in vitro companion diagnostic (IVD) device that provides information essential for the effective use of the drug. ďƒ˜ IVD companion diagnostic devices used to make treatment decisions in clinical trials of a therapeutic product generally will be considered investigational devices and the sponsor of the diagnostic device will be required to comply with the investigational device exemption (IDE) regulations that address significant risk devices.
Take Home Messages Immunogenicity investigations are important as IC formation may have an impact on the PK, efficacy and safety of a drug Bioassay performance and validity have a strong impact on the outcome of immunogenicity assessments To understand the relevance of ADA formation on PK, comparing Cmax and AUC in both the presence and the absence of ADAs is essential The regulatory and development pathways change when an assay is used for taking a treatment decision
The bioanalytical strategy should be considered an integrated part of the clinical development strategy to allow valid data generation for clinical and regulatory decision making
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Ando ApS - Bioanalytical Outsourcing Dr. Anke Domdey Nordre Strandvej 119D DK-3150 Hellebaek +45-2568-3668 www.andobio.com anke.domdey@andobio.com CVR DK31612845