Today, biopharmaceutical drug products based on proteins, antibodies, and biological agents are common in clinical research. Antibody-based biological products constitute a significant portion of the therapeutic market. The specificity of monoclonal antibodies has increased their applications in complex therapeutic areas such as cancer and autoimmune diseases. Besides, scientists can employ recombinant techniques to modify the properties of monoclonal antibodies, such as their size, structure, and affinity. However, monoclonal antibodies are other biopharmaceuticals that can potentially induce unwanted immune responses in patients. Although not all immune responses lead to adverse events, they can affect the efficacy of biopharmaceuticals.
Unwanted immune responses to a biologic can be detected through anti-drug antibodies (ADA) analysis. Antibodies can bind to the pharmaceutical drug and neutralize its activity. Understanding the importance of drug ADA complexes, the pharmaceutical industry is focused on developing precise, reliable, and sensitive immunogenicity testing methods. The current article deep dives into anti-drug antibody analysis for immunogenicity testing in clinical trials and preclinical assessments.
ADA analysis in clinical trials and preclinical testing
Antibodies are glycoproteins produced by the immune system. These antibodies belong to the immunoglobulin superfamily and consist of five common isotopes. Monoclonal antibodies are produced by a single clonal cell line. They are beneficial as reagents in antibody-based assays and biotherapeutics due to their specificity against target antigens.
The extent of monoclonal antibody immunogenicity depends on the level of antibody modification. Murine monoclonal antibodies are crucial in biochemical research. However, they have limited utility in human immunogenicity testing. Hence, humanized monoclonal antibodies with less structural differences from human antibodies induce reduced immune responses compared to murine monoclonal antibodies.
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For a biotherapeutic drug, immunogenicity response is reflected by the production of anti-drug antibodies. The detection of anti-drug antibodies is now considered the standard for immunogenicity of biotherapeutic agents. Antibodies are divided into neutralizing and non-neutralizing ADA. Non-neutralizing anti-drug antibodies bind to a biotherapeutic but do not affect its efficacy or functional activity. On the other hand, neutralizing anti-drug antibodies can directly bind with biotherapeutics and interfere with their functional activity. Hence, neutralizing anti-drug antibodies is considered critical in clinical settings.
Today, highly sensitive, specific, and precise ADA assays are vital for quality control of biotherapeutic and treating patients with these agents. The US FDA recommends a multilayered approach involving screening assay, confirmatory assay, and characterization assays, including ADA titer assay and neutralizing antibody assays. Scientists have multiple modalities to detect and quantify anti-drug antibodies in study samples.
Some examples of binding assays and immunoassays for anti-drug antibodies include:
- Antigen binding tests
- Electrochemiluminescence assays
- Radioimmunoassays
- ELISA assays, including direct, indirect, and bridging format
- Homogeneous mobility shift assays
Additionally, several other methods are available for analyzing anti-drug antibodies, such as:
- Reporter gene assays
- Capillary electrophoresis
- LC-MS bioanalysis
- Surface plasmon resonance spectroscopy
Each of these methods has unique advantages and limitations. Hence, researchers should identify individual research needs and choose techniques based on their intended application.
In conclusion
Biopharmaceuticals have witnessed steady growth in drug development. However, adequate development and validation initiatives are critical for generating reproducible and accurate results.