In light of experience, since the original guidance document was published in 2006, there are a number of changes under consideration in the draft guidance document ‘Guideline on Immunogenicity assessment of biotechnology-derived therapeutic proteins’[i].

Broadly these include:

  • More specific requirements for immunogenicity assays
  • Investigation into the clinical significance of immunogenicity
  • Risk-based approach to immunogenicity with requirements for both studies prior to registration plus studies post-registration
  • Nonclinical studies are recognised as having limited predictive value for determining immunogenicity in patients

This post will focus on the immunogenicity assays as part of the risk management strategy to mitigate clinical risk:

  • Screening assays: preliminary step to determine if an immune response has been elicited based on detecting all antibodies induced against the product. Various immunoassays are acceptable on the understanding that they detect binding interactions (i.e. antigen-antibody). It’s important to use or develop assays which have an appropriate level of specificity to ensure the accuracy of results (i.e. minimise false negatives).
  • Confirmatory assays: necessary to eliminate false positive results. Need to be measured in relation to specificity for the active protein to differentiate from binding to product-related and process- related components (i.e. host cell proteins).
  • Functional assays: Need to determine if the patient has neutralising antibodies (NAbs) against the therapeutic protein. Given the clinical impact of NAbs, sensitive and specific in vitro cell based and non-cell based assays should be used. The mode of action, target and effector pathways of the particular therapeutic protein are important considerations for choosing the suitable assay.

 

Whilst assay validation is an ongoing process throughout the development of a therapeutic protein, it is necessary to have adequate validation of the assays used in the clinical trials to provide an assurance of the results.

[i] EMEA/CHMP/BMWP/14327/2006 Rev. 1