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10 Barry Cherney IABS


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Tuesday, 19 November, 2013
Latin America Biotherapeutic Conference Day 1

Published in: Health & Medicine, Technology
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10 Barry Cherney IABS

  1. 1. Immunogenicity testing of Biotechnology Products and the Impact to Biosimilars Latin America Conference, IFPMA Biotherapeutic Medicines Sharing Experiences and Best Practices Lima, Peru November 19, 2013 Barry Cherney Executive Director Product Quality Amgen Inc
  2. 2. Protein Products have Immunogenic Potential • Administration of non native or even „humanized‟ proteins to either animals or humans can elicit either an antibody response, cellular response, or both if the immune system recognizes the protein as foreign. • All protein products have some level of immunogenicity, with varying impact to patients. • Although there are multiple theoretical causes of immunogenicity, very few real examples of why a product is immunogenic have been published 2
  3. 3. Generalized Protein Domains Non-receptor binding/functional domain Receptor binding/functional domain 3
  4. 4. Effect of antibodies on the function of proteins No cell response Cell Response Non-neutralizing antibodies Neutralizing antibodies 4
  5. 5. Clinical Concerns in Testing for Antibodies - Effects on PK/PD • The binding of antibodies to product has been shown to potentially affect (by extension or reduction) the half life in blood through the influence on clearance mechanisms. • Biodistribution of product has also been shown to be affected, such as lack of targeting to skin or tumour sites. • If product is cleared differently and its distribution is different, then its ability to have the desired biological effect may also be altered. 5
  6. 6. Clinical Concerns in Testing for Antibodies - Effects on Efficacy • Antibodies that alter the PK/PD of the product may have an effect on its efficacy. If the drug remains longer in the circulation, efficacy can be enhanced. If half life is reduced, so potentially is its efficacy. • The presence of neutralizing antibodies can directly inhibit the biological activity of the product and thus clinical efficacy may be reduced or abrogated. 6
  7. 7. Clinical Concerns in Testing for Antibodies - Effects on Safety • Extending the half life of a product can influence its toxic properties. • Redistributing a product to different sites may potentially also have safety implications. • The presence of complexes of product and antibody can have physiological consequences. 7
  8. 8. Clinical Concerns in Testing for Antibodies - Effects on Safety • Immune responses to product can lead to: • Anaphylaxis • Injection site reactions • Flu like syndromes • Allergic responses • One of the most serious adverse events occurs when neutralizing antibodies to product cross react with endogenous proteins that have a unique physiological role. 8
  9. 9. EMA mAb biosimilar and immunogenicity guidelines on the “risk-based approach” • “Comparative assessment of unwanted immune responses against the biosimilar and the reference mAb are normally undertaken as part of the clinical study”* • “A risk-based approach can provide a starting point from which the further concept of immunogenicity testing can be designed, but due to the diversity of risk factors, as discussed in this guideline, and the variety of mAbs and mAb-related products, the recommendations given here cannot be generalized.”** • “Assessment is based on the identification of risk factors inherent to the particular mAb in question, the final drug product and the treated patient population. The mechanism of action and the basic structure (chimaeric, humanized, fully human) are not sufficient for deciding on the attribution of risk level. For a risk-based approach, applicants need to define what “risk” in this context means.”** * Guideline on similar biological medicinal products containing monoclonal antibodies – non clinical and clinical issues CHMP 2010 ** Guideline line on Guideline on immunogenicity assessment of monoclonal antibodies intended for in vivo clinical use. CHMP Nov. 2010 9
  10. 10. FDA’s draft Biosimilar guideline* also includes “a risk based immunogenicity approach” • “At least one clinical study that includes a comparison of the immunogenicity of the proposed product to that of the reference product will generally be expected “ • “The extent and timing …..of the clinical immunogenicity program will vary depending on a range of factors including the extent of analytical similarity and the incidence and clinical consequences of immune response for the reference product. “ *Scientific Considerations in Demonstrating Biosimilarity to a Reference Product FDA. Feb 2012 10
  11. 11. Risk Based Approaches to Immunogenicity Testing Risk = Probabilityharm x Severityharm How many patients are likely to mount an immune response? What happens to the patient if they mount an immune response? • Severity outweighs the probability of a risk occurring. • The overall Risk Score depends on an assessment of the various factors that influence immunogenicity 11
  12. 12. Considerations in Assessing Risk of Immunogenicity - Probability Analysis Risk = Probabilityharm x Severityharm Likely Lower Probability Likely Greater Probability Immunosupressed patients Single dosing More „Human‟ IV administration Highly pure No aggregates Autoimmune disease Chronic dosing ‘Foreign’ Subcutaneous Impure Aggregates 12
  13. 13. Considerations in Assessing Risk of Immunogenicity - Severity Analysis Risk = Probabilityharm x Severityharm Likely More Severe Likely Less Severe Endogenous version Unique activity Sole therapy Life threatening disease Chronic disease Non reversible AE Replacement therapy Anaphylactic response No endogenous version Redundant activity Other therapies Non life threatening disease End stage disease Reversible AE Non replacement therapy Non anaphylactic response 13
  14. 14. Examples of Anti Drug Antibodies: Incidence and Clinical Impact Rate of Antibodies Molecule High r-Human alphagalactosidase High r-chimeric anti-TNFa Moderate r-chimeric anti-GPIIb/IIIa Fab Moderate r-Human Glucocere-brosidase Low r-Human Thrombopoietin truncated, PEG Low Antibody Incidence Clinical Impact 88% none reported 10-57% Hypersensitivity PK affected efficacy unchanged 7-19% 13% 0.5-4% r-Human Tissue Plasminogen Activator <1% 14 Higher incidence after re-administration, TCP higher in ab+ patients Neutralizing antibodies rare neutralizing antibodies TCP none reported
  15. 15. Considerations for Analytical Testing Strategies based on the outcome of the Risk Assessment Score Examples of High score considerations Examples of Low score considerations Test samples in real time Batch test samples at the end of the study More sensitive assays early in development Develop increasingly sensitive assays during development Highly conservative approach to setting cut points Less conservative approach to setting cut points Test positive binding samples for neutralization in real time Batch positive binding samples after initial screening and then test for neutralization Need to develop sensitive neutralization assays Less need for very sensitive neutralization assays 15
  16. 16. Biosimilar Specific Issues with Immunogenicity Testing • The rate of immunogenicity detected in an assay is wholly dependent on the assay chosen, its controls, execution and the clinical study sample plan design • Biosimilar companies are unlikely to know the details of the innovator assays: • • • • • • Assay format (RIA, ELISA - bridging or direct etc.) Assay sensitivity and specificity Assay positive control (standard) Positivity criteria Timing and number of samples Patient population • Multiple indications (if going into licensure with only one) Google.www 16
  17. 17. The Optimal Screening Assay An Optimal screening assay should: • Be sensitive enough to detect any level of specific antibody present in patient sera. • Have no false negatives • Have a few false positives able to be proved false positives • Discriminate between pre-existing antibodies and treatment induced antibodies • Detect antibodies in the presence of drug • Be reproducible 17
  18. 18. The Choice of Assay Format can Heavily Influence the Rate of Immunogenicity Results Reported Coloured reagent Detection System Clear reagent Enzyme Conjugated Drug ELISA Detecting antibody Bridging ELISA Anti-drug antibody Drug Drug Serum Antibody Radio Immunoprecipitation Assay (RIP) Add Serum Sample 18 Precipitate antibody bound drug Measure radioactivity in pellet
  19. 19. Each Assay Format Has Implications for the Results it Reports • ELISAs do have several issues related to design, especially non specific background and the need to stick the antigen to a solid surface • The extensive washes required to reduce background can reduce the ability to detect low affinity antibodies as they can get washed away • Incubation times may not allow for sufficient binding of low affinity antibodies- too long can lead to dissociation too 19
  20. 20. Each Assay Format Has Implications for the Results it Reports • The bridging format appears to have the least background and does not require the use of an antihuman Ig reagent and its associated validation. Care must be taken to avoid loss of low affinity antibodies due to the bispecific nature of the binding. • RIP assays tend to be the more sensitive assay format as compared to ELISAs*. Not all methods to precipitate complexes, such as Protein A/G, necessarily detect all Ig isotypes and subclasses and the format of choice should be justified by the sponsor *Swanson, S.J., et. al., (2004) Nephron Clin Practice Vol 96 p88-95 20
  21. 21. Surface Plasmon Resonance (SPR) 21
  22. 22. SPR Assays - Advantages and Disadvantages • SPR assays involve the exposure of drug in a lawn of dextran that do not affect the structure of the product to the extent of an ELISA • It is a real-time procedure and is therefore fast and also detects rapidly dissociating antibodies which can be missed by other methods • SPR assays do not require extensive wash steps and can not only detect low affinity antibodies but characterize the binding activity • SPR equipment is expensive and needs expert knowledge to design, run and analyze data if the results are not to be spurious 22
  23. 23. Selecting the Assay Cut Point Impacts Reporting Rates Optical Density (OD) 0.500 Cutpoint at 95% negative X Negative Control Mean NSB 29 25 21 17 13 9 5 1 0.000 Sample Number • How the assay cut point is selected dictates when a sample is deemed negative or positive • The assay cut point thus has impact on the rate of seroconversion reported 23
  24. 24. Circulating Therapeutic Can Interfere With Antibody Detection in Antibody Assays Circulating Drug Serum Anti Drug Antibody No Binding to Plate Drug Coat Drug interference can cause significant problems in detection of antibody responses due to the presence of product in samples collected for antibody assessment. This normally results in an artefactually low estimate of antibody content of affected samples and can be so pronounced as to cause false negative results 24
  25. 25. One has to Understand the Impact of Drug in the Sample if the Screening Assay is to be Meaningful 3.50 Titer 3.1 Titer 2.9 Titer 2.7 Titer 2.5 3.00 2.50 2.00 Limit of detection 1.50 1.00 25 640 1280 µg/ml drug added to Serum Sample 320 80 40 20 10 5.0 2.5 1.25 0.63 0.32 0.16 0.08 0 0.00 160 0.50
  26. 26. Identification of Immunoglobulin Class • It may be useful to identify the class and subclass of immunoglobulin detected in a sample but depends on the product and patient responses: • The disease state or route of administration of drug induces an antibody response of classes other than IgG • IgA in certain skin autoimmune disorders • IgE often manifests itself in the patient before being detected in a screening assay. • Should hypersensitivity be detected in clinical trials, the development of an assay is warranted • This may be able to detect and avoid reactions to subsequent doses 26
  27. 27. A Histamine Release Assay to Measure Anti-drug IgE Drug IgE Histamine Release IgE receptor transfected cell IgE loaded cell IgE receptors crosslink 27
  28. 28. Neutralizing Capacity of Antibodies •The neutralizing capacity of antibodies to many products should be tested in a biological assay •Alternative binding-based assays may be appropriate for certain products particularly when used as the potency assay for release– which are often more sensitive than cell based assays •There is discussion about the utility of neutralizing antibody assays in respect to clinical impact (in vitro tests may not reflect what occurs in vivo). •From a risk based approach, identification of a neutralizing response can allow for subset analysis of weak signals in the patient population – patients with a neutralizing response may be assessed for PK and PD but this may not be straightforward (e.g. in the oncology setting) 28
  29. 29. Bioassays for Neutralizing Antibodies Product Cell Response No Cell Response Neutralizing Antibody 29 • Assay responses to product may take the form of cell proliferation or growth inhibition, secretion of protein, gene expression etc.
  30. 30. A Cytokine Neutralizing Antibody Bioassay 2.000 1.800 Serum Pre Exposure Abs 450 1.600 Cytokine 1.400 1.200 Serum Post Exposure 1.000 0.800 0.600 0.400 0.200 0.000 1 10 100 1000 Serum Concentration [Dilution] 30 10000 100000
  31. 31. Conclusions - Immunogenicity 1. The results of immunogenicity testing rely wholly on the design and execution of the assay used to detect and characterize any immune response 2. It is impossible to compare rates of immunogenicity between biotechnology products unless a head to head clinical immunogenicity study is carried out, thus they should be conducted as such 3. Even in such head to head studies, the rates of immunogenicity are dependent on the assay that the biosimilar company uses and may not reflect the rates seen by the innovator, thus only „relative‟ assessments of rates can be provided. 31
  32. 32. Acknowledgements • • • • • Tony Mire-Sluis Gino Grampp Andrew Fox Geoff Eich Richard Markus 32