February 2023

Webinar | Challenges of developing ADA and concentration (PK or PD) assays for lysosomal transgene enzymes

Gene therapy can be used to permanently correct genetic disorders by delivering a functional copy of the gene into the nucleus of affected cells or alternative cells, which then release the functional protein into systemic circulation. 

One of the biggest challenges faced by the bioanalytical sector is the lack of a true reference material. As a result, in most assays, an alternative commercially available therapeutic (for example, an enzyme replacement therapy (ERT) product) can be used as a surrogate for the transgene enzyme. This webinar discusses approaches taken in order to monitor the concentration of the expressed transgene product and any associated immunogenicity.

Transgenes are expected to have very low levels of immunogenicity; therefore, immunogenicity assays against transgenes themselves are not widely developed. Nonetheless, it is very important to monitor any potential case of immunogenicity. Current regulatory guidelines are not applicable to transgene products, which adds to the challenge. This case study describes the considerations and challenges encountered when developing and validating an assay for transgene lysosomal enzyme products. Since lysosomal enzymes are sensitive to physiological pH and salt, which is required for the detection of anti-drug antibodies (ADA), specific buffers were required to maintain their optimal configuration. 

The same level of challenges was also encountered during the development of an assay to determine the transgene product concentration, mainly due to the lack of a true reference standard and the presence of the equivalent endogenous molecule in healthy and disease matrices (with the potential that the defective enzyme could still be detected in the ligand-binding assay). Therefore, measurement of the transgene concentration could not be described as a true PK assay and does not conform to current the PK guideline/guidance, requiring an approach more aligned with a PD assay with a well defined context of use.

Attendees will learn about:

  • Challenges associated with enzyme immunogenicity assessment
  • Measurement of the transgene product - PK or PD?
  • Development considerations for non-stable enzyme analytes
  • Immunogenicity assay development on the Gyrolab® platform

Watch the webinar below