Narendra Chirmule

Immunogenicity to Therapeutic Proteins: Impact on PK/PD and Efficacy

The development of therapeutic proteins requires the understanding of the relationship between the dose, exposure, efficacy, and toxicity of these molecules. Several intrinsic and extrinsic factors contribute to the challenges for measuring therapeutic proteins in a precise and accurate manner. In addition, induction of an immune response to therapeutic protein results in additional complexities in the analysis of the pharmacokinetic profile, toxicity, safety, and efficacy of this class of molecules. Assessment of immunogenicity of therapeutic proteins is a required aspect of regulatory filings for a licensing application and for the safe and efficacious use of these compounds. A systematic strategy and well-defined criteria for measuring anti-drug antibodies (ADA) have been established, to a large extent, through coordinated efforts. These recommendations are based on risk assessment and include the determination of ADA content (concentration/titer), affinity, immunoglobulin isotype/subtype, and neutralization capacity. This manuscript reviews the requirements necessary for understanding the nature of an ADA response in order to discern the impact of immunogenicity on pharmacokinetics/pharmacodynamics and efficacy.

Identification and inhibition of drug target interference in immunogenicity assays

A well-designed anti-drug antibody (ADA) immunoassay is critical for appropriately monitoring the immunogenicity profile of a therapeutic protein during its development. AMG 386 is a peptide-Fc fusion protein that inhibits angiogenesis by preventing the interaction of angiopoietins with the Tie2 receptor. In bridging immunoassays for ADA, interference by the drug target, present in the assay sample, can result in false positive antibody detection. We used a statistical design-of-experiments approach to identify angiopoietin interference in bridging immunoassays of anti-AMG 386 antibodies. We also demonstrated that a high-affinity monoclonal antibody, directed against an epitope on angiopoietin that competes with AMG 386 binding, could inhibit the angiopoietin interference while preserving the detection of ADA. This report describes the development and validation of methodologies for evaluating and addressing drug target interference in bioanalytical assays that involve interactions between drug, ADA, immune complexes, and drug target.

Considerations for optimization and validation of an in vitro PBMC derived T cell assay for immunogenicity prediction of biotherapeutics.

An immune response to a biotherapeutic can be induced when the therapeutic is processed and presented by antigen presenting cell to T helper cells. This study evaluates the performance of an in vitro assay that can elicit antigen specific effector T cell responses. Two biotherapeutics with known clinical immunogenicity [FPX1 and FPX2] were assessed for their ability to induce antigen-specific IFN-γ secreting T cells in peripheral blood mononuclear cells (PBMC). The 24 amino acid peptide component of FPX1 elicited an antigen-specific response in 16/34 (47%) individual naïve healthy donors. This in vitro effect was consistent with high rate of immunogenicity which was observed when this drug was administered in clinical trials. FPX2 did not induce antigen-specific T cells in vitro, which correlates with the low rate of development of anti-drug antibody responses to this molecule in the clinic. The assay has the potential to predict immunogenicity and help in the selection of biotherapeutics at the early development stage of a clinical candidate.

Blockade of interferon-γ normalizes interferon-regulated gene expression and serum CXCL10 levels in patients with systemic lupus erythematosus.

To assess the safety and immunologic impact of inhibiting interferon‐γ (IFNγ) with AMG 811, a human IgG1 monoclonal antibody against IFNγ, in patients with systemic lupus erythematosus (SLE).

Blockade of interferon‐gamma (IFN‐γ) normalizes IFN regulated gene expression and serum CXCL10 (IP‐10) in subjects with systemic lupus erythematosus (SLE)

To assess the safety and immunologic impact of inhibiting interferon‐γ (IFNγ) with AMG 811, a human IgG1 monoclonal antibody against IFNγ, in patients with systemic lupus erythematosus (SLE).

Immunogenicity testing strategy and bioanalytical assays for antibody–drug conjugates

BACKGROUND Immunogenicity testing is an important component of clinical development for large-molecule biotherapeutics. New complex types of large molecules, such as antibody-drug conjugates (ADCs), require careful evaluation of the testing strategy and bioanalytical assays used to monitor the development of antitherapeutic antibodies. RESULTS An electrochemiluminescence-based immunoassay for the detection and epitope characterization of anti-ADC antibodies was validated. Using this assay format, antibodies directed against the monoclonal antibody and linker-drug components of the ADC were successfully detected in a multiple-dose rat toxicity study. CONCLUSION Immunogenicity assays incorporating epitope determination may provide additional information about the characteristics of induced antitherapeutic antibodies, including the magnitude and timing of the various types of antibody responses.

Detection of anti-ESA antibodies in human samples from PRCA and non-PRCA patients: an immunoassay platform comparison

BACKGROUND The immunological methods for detecting antibodies to erythropoiesis-stimulating agents (ESAs) differ in assay sensitivity. However, this parameter, routinely determined in clinical assays using a high-affinity non-human polyclonal antibody, gives a one-dimensional assessment of antibody detection. We compare three widely used immunological methods and evaluate the ability of each to detect mature human antibodies and human antibodies characteristic of an early immune response. METHODS The detection of anti-ESA antibodies was compared between a radioimmunoprecipitation (RIP) assay, an electrochemiluminescence (ECL) bridging enzyme-linked immunosorbent assay and a surface plasmon resonance (SPR)-based immunoassay. All three methods were validated for sensitivity, specificity and precision. Specimens from clinical studies or post market testing were categorized as pure red cell aplasia (PRCA) or non-PRCA and then analyzed in each method. RESULTS Among the antibody-mediated PRCA samples, which contain high affinity neutralizing antibodies, there was strong correlation between all methods. The results from non-PRCA sample analysis show high correlation between RIP and ECL methods; however, differences between the SPR immunoassay and the ECL and RIP were demonstrated. The samples that scored positive in the SPR immunoassay and negative by RIP and ECL were characterized to be of low antibody concentration, contained a high percentage of rapidly dissociating antibodies, or were antibodies of the IgM isotype. CONCLUSIONS All three immunological methods are appropriate for detection of antibodies associated with antibody-mediated PRCA. However, the SPR immunoassay platform detected an early, low affinity IgG and IgM antibody response as well as detected and characterized a pathogenic antibody response associated with antibody-mediated PRCA.

Immunogenicity of panitumumab in combination chemotherapy clinical trials

BackgroundPanitumumab is a fully human antibody against the epidermal growth factor receptor that is indicated for the treatment of metastatic colorectal cancer (mCRC) after disease progression on standard chemotherapy. The purpose of this analysis was to examine the immunogenicity of panitumumab and to evaluate the effect of anti-panitumumab antibodies on pharmacokinetic and safety profiles in patients with mCRC receiving panitumumab in combination with oxaliplatin- or irinotecan-based chemotherapies.MethodsThree validated assays (two screening immunoassays and a neutralizing antibody bioassay) were used to detect the presence of anti-panitumumab antibodies in serum samples collected from patients enrolled in four panitumumab combination chemotherapy clinical trials. The impact of anti-panitumumab antibodies on pharmacokinetic and safety profiles was analyzed using population pharmacokinetic analysis and descriptive statistics, respectively.ResultsOf 1124 patients treated with panitumumab in combination with oxaliplatin- or irinotecan-based chemotherapy with postbaseline samples available for testing, 20 (1.8%) patients developed binding antibodies and 2 (0.2%) developed neutralizing antibodies. The incidence of anti-panitumumab antibodies was similar in patients with tumors expressing wild-type or mutant KRAS and in patients receiving oxaliplatin- or irinotecan-based chemotherapies. No evidence of an altered pharmacokinetic or safety profile was found in patients who tested positive for anti-panitumumab antibodies.ConclusionsThe immunogenicity of panitumumab in the combination chemotherapy setting was infrequent and similar to the immunogenicity observed in the monotherapy setting. Panitumumab immunogenicity did not appear to alter pharmacokinetic or safety profiles. This low rate of immunogenicity may be attributed to the fully human nature of panitumumab.Trial registrationClinicalTrials.gov: NCT00339183 (study 20050181), NCT00411450 (study 20060277), NCT00332163 (study 20050184), and NCT00364013 (study 20050203).

Assessing specificity for immunogenicity assays

Developing sensitive and specific bioanalytical assays for measuring the immunogenicity of biological therapeutics has become an integral component of the drug-development process. The strategy for measuring these immune responses involves performing sensitive screening assays that are capable of detecting low levels of both low- and high-affinity antibodies. However, having sensitive assays inherently results in a certain rate of false-positivity. Hence, developing steps to determine specificity in these assays is important to confirm the presence of antidrug antibodies. The specificity assays are defined by the ability of an assay to score a positive result if the serum sample contains an antibody that can bind and/or neutralize the therapeutic protein. Here, we discuss the methodologies for determining specificity in the bioanalytical assays used for measuring antidrug antibodies. These methods will provide investigators and regulators with guidelines to develop and review assays to measure antidrug antibodies, which can specifically interfere with the actions of the drug and/or influence the safety profile of the therapeutic proteins.

Impact of matrix-associated soluble factors on the specificity of the immunogenicity assessment

BACKGROUND Specificity and sensitivity are essential in assays for immunogenicity assessment of biotherapeutics. Nonspecific interactions from excess therapeutic or anti-therapeutic antibody, soluble ligands (e.g., target receptor), or serum proteins associated with autoimmune conditions (e.g., rheumatoid factor) in samples can impact the detection of a true anti-therapeutic response. RESULTS Electrochemiluminescence-based bridging assay formats could eliminate the interference due to rheumatoid factor with no pretreatment with Melon Gel™ or aggregated IgG. The interference due to soluble factors was not platform specific for the four therapeutics evaluated in this study. CONCLUSION Melon Gel pretreatment and avidin high-bind (Meso Scale Discovery) plates can effectively reduce interference due to rheumatoid factor in ELISA- and electrochemiluminescence-based assays, respectively. Excess levels of therapeutic and anti-therapeutic antibodies in bridging assays can impact assay specificity.