Demonstrating Equivalence
Figure 4. Equivalence Test Results Comparing SDS-PAGE (Reference) to CZE
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A characterized impurity of a licensed biopharmaceutical product is currently quantitated by SDS-PAGE at the final container
stage. Because of anticipated supply problems for critical SDS-PAGE materials, it was decided to develop and validate a capillary
zone electrophoresis (CZE) method that will replace the current (licensed) method. Validation characteristics for a quantitative
limit test, accuracy and intermediate precision are compared before replacing the licensed method with the validated CZE method.
The AMV results of both methods suggest similar performance for intermediate precision but also a drift in the percent impurity
results (only the accuracy or "matching a reference" comparison is shown here). From the analysis of historical release data
with respect to the current release specifications (for SDS-PAGE), a delta of _1.0% was chosen for the equivalence test between
both impurity levels. Both methods were run simultaneously (side-by-side) for each of a total of n=30 final container samples,
and the results were compared by two-sided, paired, t-test statistics with a pre-specified delta of -1.0% (percent is reported
percent, not relative percent). The paired t-test results are summarized in Figure 4.
The 95% confidence interval of the CZE method (4.88 – 5.32) lies entirely over the SDS-PAGE mean (3.8%) plus the positive
delta (3.8% + 1.0% = 4.8%). This means that the CZE results for our impurity are not only significantly higher than our licensed
SDS-PAGE method, but also that the expected drift in results is significantly higher than our pre-specified limit that was
based on the gap of our historical release results relative to the release specifications. Release specifications would need
to be changed for the CZE method to use this new method for release testing. This would not only be expected by the regulatory
authorities when submitting this change in test methods. It would also be a business need, as we would otherwise significantly
increase the expected number of specification-failing lots.
Submitting Validation and Comparability Results to the Regulatory Agencies
Table 3. General Guidance for Regulatory Submission Categories for US and Europe
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After the successful completion of the AMV and comparability studies for a new method, results can be submitted to the agencies
where needed. If the particular biopharmaceutical is licensed abroad, analytical method transfer (AMT) results should also
be submitted for each region that requires lot-release testing within that region. The submission categories and expected
approval timelines are somewhat similar in the US and Europe. Other regulatory agencies for countries like Canada and Japan
may take significantly longer for approval. It is therefore crucial to plan properly and to strategically submit changes,
keeping in mind different timelines in different regions. The submission categories and estimated approval times are illustrated
for the US and Europe in Table 3. If we were to submit our new CZE assay (see example under equivalence studies), we would
also submit a request for a release specification change. This submission would be submitted as a pre-approval submission
(PAS) in the US and a Type II variation in Europe. Because of the costs, time, and effort involved particular with new assays,
submissions of all other assay changes could be bundled together or submitted with other significant changes in production
process or product itself. However, excessive or abusive bundling of independent changes may lead to regulatory requests to
submit independent changes separately.
Stephan O. Krause, Ph.D., is validation manager of QC assay support, Bayer Healthcare LLC, 800 Dwight Way, Berkeley, CA 94701-1986, 510.705.4191,
fax: 510.705.5143, stephan.krause.b@bayer.com
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