If all that was necessary to validate a potency assay was to show that batches of remestemcel-L (whether they are samples set aside from lots that went into patients or whether they are inventory from lots that have not gone anywhere yet except into the inventory) have anti-T cell activity in vitro then sure - but I don't think that that is enough to validate a potency assay.
I think to validate a potency assay you have to show that some associated activity also carries over into the in vivo environment - which means the new potency assay's associated and consequential activity has to itself be carried over to get tested in vivo (in the body - of patients) environment.
I do see a potential difference between a potency assay (TNFR1 expression is the expression of a cell surface receptor - it is not in itself a measure of cytokines being produced or genes being translated or anything like that - its just how much of a receptor presence is there) and an activity test. But most MSB correspondence seems to blur the two together.
What has not been mentioned specifically by Dr Rose is inhibition of interleukin 2 receptor alpha in T cells co-cultured with remestemcel-L which is described as the activity test in the ODAC briefing papers. The ODAC briefing papers do separate the potency assay from the activity test in the table of critical quality attributes.
So perhaps a dud potency assay that was coupled with a nonetheless still solid (ie still reliable) activity test (frankly the activity test does seems closer to me to the T cells (fewer steps away than TNFR1 expression) might still allow a link to the results from the pediatric trial.
Though I think the FDA wasn't convinced about the IL2Ralpha stuff used in the pivotal trial either
Perhaps I've been unconsciously biased because I wasn't impressed with MSB's presentation of IL2Ralpha data in the ODAC briefing.
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