It looks like this: the FDA is saying the potency assay is best...

It looks like this: the FDA is saying the potency assay is best validated by results of a randomised, controlled clinical trial. They would consider a single arm trial IF Mesoblast could show convincing evidence that validates their potency assay. But from the FDA's perspective, that can only be achieved through a randomised, controlled clinical trial, in adults and/or children...

But SI doesn't want to do a randomised controlled clinical trial and has literally spent years and hundreds of millions of investors funds fighting against it. When he said the FDA told him they "couldn't do another trial until they had validated the potency assay", IMO that was a partial truth at best, which is why it wasn't previously mentioned in any of the reports to shareholders. This announcement makes it pretty clear that it applies only to single arm open label trials, not prospective randomised controlled clinical trials. And it makes complete sense in that context and therefore his proposed single arm trial has very little chance of being accepted by the FDA