FDA Releases Guidance on Immunogenicity Testing of Therapeutic Proteins

On April 22, 2016, FDA released Assay Development and Validation for Immunogenicity Testing of Therapeutic Protein Products, Draft Guidance. The guidance addresses the development and validation of immune assays for assessment of the immunogenicity of therapeutic protein products during clinical trials. The guidance provides recommendations for the development and validation of screening assays, confirmatory assays, titering assays, and neutralization assays for detection of anti-drug antibodies (ADA) and, on a case-by-case basis, some combination products. The guidance does not apply to in vitro diagnostic products and does not address product and patient risk factors that may contribute to immunogenicity.

Specifically, the guidance discusses assay design elements including testing strategies such as a multi-tiered testing approach, immunoglobulin isotypes, and epitope specificity. The following are also addressed:

• Assay cut point

• Sensitivity, including assay sensitivity and drug tolerance

• Specificity and selectivity, including matrix interface and minimal required dilution

• Precision

• Reproducibility

• Robustness and sample stability

• Format selection

• Reagent selection, including development of positive control antibodies, development of negative controls, detection reagent consideration, and controlling non-specific binding

• Reporting results for qualitative and semi-quantitative assays

• Other considerations including pre-existing antibodies, rheumatoid factor, monoclonal antibodies, conjugated proteins, and products with multiple functional domains.

Assay development information provided addresses the following:

• Development of a screening assay

• Development of a confirmatory assay, including selection of format for confirmatory assay and cut point of confirmatory assay

• Development of titering assay, including titer determination and cut point of titering assay

• Development of neutralization assay, including selection of format, activity curve, considerations for matrix interface, and cut point.

The assay validation section covers general considerations and recommendations for validation of screening, confirmatory, titering, and neutralization assays. Additional sections address implementation of assay testing and documentation.

Source: FDA