Immunogenicity Testing is a method to check the ability of a drug to provoke an immune response from the body. This testing is vital to developing safe and successful drugs. A lot of work has been put into this over the last decade.
FDA finalized a guidance document on immunogenicity testing of therapeutic protein products in January 2019, following previous drafts. Guidelines are also available from the WHO and other leading bodies. The guidelines facilitate the development and validation of immunogenicity testing assay, helping with assessment during clinical trials.
On The Workings of Immunogenicity Testing
The molecules of a medicine/drug may be large enough to make the human body consider it a foreign invader. The triggered immune system can end up reducing the pharmacokinetic profile and pharmacodynamic properties of a drug. This can result in reduced efficacy of the drug. In some cases, it may even pose a problem to patient safety.
FDA guidelines recommend a panel of immunogenicity testing assays with a multi-tiered approach. The detection of anti-drug antibodies (ADAs) is highlighted. Though testing on a case-by-case basis can also include peptides, oligonucleotides, and combination products.
Biologics can require a panel of assays for a thorough screening of immunogenicity. This applies to biosimilars as well, because the method or combination can be different from the origin drug. A well-devised analytical testing strategy is necessary to work through the panel of assays. For many drugs, this strategy can include a screening assay complemented by a confirmatory assay. This is often followed by a neutralization assay for assessing the capability of the antibodies.
Data so gathered can further be used for pharmacodynamic and pharmacokinetic properties and their effects on patients. A better approach to understanding the kinetics of antibody development can be very helpful. This data can find a use for more precise analytics and in silico testing.
Unintended immunogenicity should be monitored not only during clinical development but also as part of post-marketing surveillance. Testing is directly influenced by good assay design, assay reagents, execution of assays, and how the data so gathered is used.
Validation and Considerations
Assay validation requires a demonstration that the characteristics employed for testing are suitable for its intended use. The extent of validation is dependent on the stage of drug development. It should display the results and consequences of immunogenicity testing of subjects in the trial.
A partial-validation may be acceptable, depending on the stage of drug development. Important points remain the assessment of specificity, precision, drug tolerance, and sensitivity. For earlier stages of development, robustness, reproducibility, and stability can have a lower emphasis. Many high-risk products will require full validation before moving to clinical studies. License application, in any case, requires fully validated assays. While the above-mentioned points remain in play, a balanced study should not lose focus of the cut-point.
Do keep in mind that testing remains a multi-tiered approach and steps, in general, remain broad examples. The goal of these tests and immunogenicity testing assays remains to predict patient immune response to therapy.