Ann: FDA Notifies Clinical Data Sufficient for Refiling aGVHD BLA, page-542

And if you believe what the CEO of Mesoblast says, in lay terms, the FDA want to make sure that the Ryoncil inventory that MSB currently have in stock and future doses of Ryoncil will produce post approval, are as effective as the product MSB used in the phase 3 trial (which the FDA is already convinced is effective- supported by no CRL issue on effectiveness raised in CRL#2).

In my lay terms, MSB have produced a product that is effective against pediatric SR-aGVHD and the FDA acknowledge that. Mesoblast just need to be able to demonstrate that they have a reliable test to ensure that products released to market meet the same potency / quality and purity of what was used in the phase 3 trial. Quality assurance.

interestingly the adult trial they want to run already has some real world data generated from the EAP, where adults without treatment have approx 20%-30% survival by 100 days… those treated with Ryoncil have approx 67% survival.