Authored By: Mo Heidaran, Vice President Technical, PAREXEL Consulting
I have been asked many times while working in CBER/OTAT what is the difference between assay qualification versus assay validation? After all, there is no mention of assay qualification in the relevant FDA laws, or in the rules and regulations [21 CFR 211.165(e) and 211.194(a)(2))]. However, as a matter of policy, FDA/CBER/OTAT guidance documents and outreach educational materials mention and create a discernable boundary between these two concepts. FDA/CBER/OTAT does not generally require validation of assays during early stages of clinical studies for biological products, such as cell and gene therapy products. Although, CBER/OTAT Subject Matter Experts (SMEs) often state in public meetings that assay validation is required for licensure.
However, as a scientific matter and as good laboratory and manufacturing practices, when I was at FDA, I highly recommended using a validated assay whenever possible to measure a critical product quality attribute, especially if it is used to collect information during clinical studies that determine product efficacy (for example pivotal or licensing trial). The reason for this is quite simple, validation involves providing full assurance that a given process or test can performed reproducibly and accurately with a high degree of sensitivity, precision and linearity, even under a worst case scenario. This means the assay yields equivalent results using the same sample when is used by different operators and under different lab environments or using different instruments, so long as the assay parameters are controlled as specified in a protocol.
Qualification sets a lower bar and means the assay can be performed with some reasonable degree of reproducibility by the manufacturers, under very controlled conditions, such as a being performed by a designated operator and using a specific instrument or a reagent lot.
As a result, manufacturers who choose to use a qualified, not a validated, assay to collect critical information during Phase III or pivotal studies could potentially collect data sets which are not fully representative of their product quality. This could potentially impact the usefulness of assays results that are relied upon to define meaningful specification/acceptance criteria to assess and verify product quality.
A typical approach to qualify and then validate your critical assays is as follows:
- For qualification, regulatory authorities generally expect a demonstration of a reasonable degree of assay sensitivity, linearity, precision and accuracy.
- For validation these parameters have to be further complemented by assay ruggedness and robustness.
- For purpose of this discussion, assay ruggedness is the reproducibility of the assay under a variety of variable test conditions that include different instruments, operators, and reagent lots.
- Robustness on the other hand provides an indication of the ability of the assay to perform under normal usage and not being impacted by changes for example the incubation time, temperature, sample preparation, buffer or pH, parameters that can be controlled and specified in the assay protocol.
So, the timing is critical when it comes to using a qualified assay or a validated assay during Cell and Gene Product product’s development and sponsors should make thoughtful decisions so that data used to support development and subsequent BLA submission are reliable and utilize appropriate assays during a given stage of development.
For additional information about assay validation please refer to FDA Guidance and ICH guideline:
• Analytical Procedures and Methods Validation for Drugs and Biologics – issued July 2015 (https://www.fda.gov/downloads/Drugs/Guidances/UCM386366.pdf)
• ICH Q2(R1) Guideline: Validation of Analytical Procedures: Text and Methodology – November 2005 (https://www.ich.org/fileadmin/Public_Web_Site/ICH_Products/Guidelines/Quality/Q2_R1/Step4/Q2_R1__Guideline.pdf)