Immunogenicity
Immunogenicity assessment
Detecting and characterizing wanted and unwanted immune responses to new biopharmaceuticals is an essential task in order to ensure clinical safety and efficacy. An outline by Eurofins Medinet.
For more than 20 years, biopharmaceutical drugs have been increasingly used in the marketplace to complement more traditional small molecule drugs, and they have revolutionized the treatment of many diseases. Biopharmaceuticals consist mainly of drug products containing biotechnology-derived proteins as the active substance. These biotechnology-derived therapeutic proteins have been observed to provoke immune responses in the human body, to varying extents. The possibility that, or the degree to which, a particular substance may provoke an immune response is described as its ‘immunogenicity’.
Wanted and unwanted Immunogenicity
Biosimilars and Immunogenicity
WANTED AND UNWANTED IMMUNOGENICITY
The immunogenicity of a biopharmaceutical is a function of its ‘foreignness’ to the recipient1. Immunogenicity can be either wanted or unwanted. Biopharmaceuticals provoke a wanted immune response when the immune response is directed against substances administered for the induction of a protective immunity. In some cases, biopharmaceuticals should specifically stimulate targeted immune responses through activating antibody dependent cell-mediated cytotoxicity or complement-induced cell death, such as the use of the CD20-specific antibody rituximab for the treatment of CD20+ follicular lymphoma2. Unfortunately, unwanted immune responses have also been observed, and the consequences of an unwanted immune response to a therapeutic protein may range from transient appearance of antidrug antibodies (ADAs) without any clinical significance, to severe life-threatening adverse reactions. The ADA may negatively influence the therapeutic effect of the biopharmaceutical, resulting in a need to enhance the administered dose (PK effect) or, more dramatically, resulting in a negative effect on drug efficacy. Furthermore, clinical safety issues may occur, such as anaphylactic shock, non-acute hypersensitivity or cross reactivity with the endogenous counterpart, causing deficiency syndromes in the patient. Needless to say, immunogenicity may have potential implications for both the safety and efficacy of biotechnology derived therapeutic proteins3,4.
BIOSIMILARS AND IMMUNOGENICITY
The production and manufacture of biopharmaceuticals usually occurs in living cells. A range of product and host-related factors have the potential to provoke an immune response. With the patent expiry of many first-generation biopharmaceuticals, the development of biosimilars (generic products) becomes highly attractive. However, the development of biosimilars may result in differences in product composition, manufacturing and packaging from the original molecule, and therefore may induce unwanted immunogenicity, similar to or different from the original compound. It is of pivotal importance, thus, to monitor adverse events closely when treating patients with biotechnology-derived therapeutic proteins and biosimilars. In fact, the European guidelines require a pharmacovigilance plan with focus on immunogenicity monitoring for biosimilars.
IMMUNOGENICITY ASSESSMENT
Although the potential risks of immunogenicity of a biopharmaceutical can be predicted by performing in vitro tests and in vivo animal studies during drug development, the immunogenic potential, and thus safety, of a biopharmaceutical drug can only be assessed through clinical trials5. The detection and characterization of wanted and unwanted immune responses towards new biopharmaceuticals is essential for ensuring their clinical safety and efficacy. The European Medicines Agency (EMEA) recently released guidelines which include recommendations to incorporate immunogenicity testing as part of clinical trials4.
For vaccine-mediated wanted immune responses or stimulation of wanted immune responses, positive patient samples can be identified through all phases of clinical development. In the majority of cases, the assessment of drug-induced (un)wanted immune response consists of screening for a humoral response. A comprehensive step-by-step workflow is followed to support immunogenicity testing in all phases of clinical trials (See Figure 1).
Figure 1: Strategy for antibody detection and characterization.
The first step is to select and develop tailor-made ELISA-type assays to detect and characterize ADAs that may be present in the patient’s blood sample. It is of pivotal importance to screen person by person, as considerable interindividual variability in antibody response with regard to antibody class, affinity and specificity has been observed. After this initial screening round for the identification of antibody positive specimens, positives are then confirmed using a competition assay with the biopharmaceutical drug of interest, confirming the specificity of the observed response. Confirmed positive ADAs can be quantified by titer value.
When ADAs are produced that bind to the biopharmaceutical compound in vitro, it does not necessarily mean that they will also inhibit the therapeutic effect in vivo. The next step comprises an assessment of the neutralizing capacity of the ADA formed, using either functional bioassays or a competitive ligand binding ELISA. In some cases, the drug-induced unwanted immune response consists of a cellular response. These T lymphocyte-mediated immune responses induce cytokines to activate macrophages, natural killer cells, and antigen-specific cytotoxic T cells, and do not produce ADA. Therefore, the screening for humoral response as described above is not applicable. Instead, T lymphocyte cell surface markers, intracellular cytokine levels and released cytokines are determined through FACS and T-cell ELISPOT analyses.
CONCLUSION
Unwanted immunogenicity may have potential implications for both the safety and efficacy of biotechnology-derived therapeutic proteins. Regulatory bodies recommend monitoring immunogenicity as part of all clinical trials and evaluating all patients, as considerable inter-individual variability in antibody response with regard to antibody classes, affinity and specificity has been observed. In addition, the unpredictability of the onset and incidence of immunogenicity requires long-term monitoring, both during clinical trials and in post-marketing surveillance.
References
1. Benjamini E and Leskowitz S, Immunology, a short course, Second edition, Wiley-Liss
2. Van Meerten T, van Rijn RS, Hol S, Hagenbeek A and Ebeling S, Complement-Induced Cell Death by Rituximab depends on CD20 expression level and acts complimentary to Antibody-Dependent Cellular Cytotoxicity, Clin Cancer Res 12(13) 1 July, 2006
3. van de Weert and Horn Møller E, Immunogenicity of Biopharmaceuticals, AAPS Press
4. Guideline on immunogenicity assessment of biotechnology-derived therapeutic proteins, December 2007, EMEA
5. Chirino AJ, Ary ML and Marshall SA, Minimizing the immunogenicity of protein therapeutics, Drug Discovery Today 9, pp82-90, 2004
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Method validation approach for the determination of antibody response to biopharmaceuticals
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