“Bad” GMR [Power / Sample Size]

posted by konkous – Greece, 2020-12-11 15:44 (1090 d 16:05 ago) – Posting: # 22144
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Dear Helmut,

Thank you very much for your prompt feedback.

Please let me provide some more information regarding the study and its design.
The study is an in vitro permeation study for a topical product. So the design is not the typical 2x2 crossover design since we are dealing with tissues from different donors. Each of the reference and test products is applied on replicate skin sections of each donor. The only effect here (maybe simplifying things a little) is the formulation effect since each of the test and reference formulations is applied on each donor at the same time on separate skin sections.
To this end the statistical comparison is closer to a paired TOST.

The comparison is made according to the provisions of FDA draft guidance on acyclovir cream.

The aim of the pilot was to see if the duration of the study is sufficient to capture the entire release profile (increase and subsequent decrease of flux) and to have an idea about the GMR.

You are absolutely right regarding the conclusion that the chances for establishing equivalence are slim to none. I was wondering whether someone could "translate" the criterion of the pivotal study into a scaled criterion for the pilot taking into account the small sample size of the latter and its associated uncertainty. For example i have seen the following approach for reaching a go / no-go decision

Thanks a million!
Best regards,

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