Ann: FDA Advisory Committee Sets Review Date for Remestemcel-L, page-472

For those discussing the topic of mechanism of action not being established (mainly @Cato bringing up paragraphs where they discuss it, but others interested in what this could mean moving forward), it's not an issue that the specific mechanism of action isn't established. The FDA make it clear in these circumstances that that was a possibility they (the FDA) anticipated and described two different pathways that companies could get passed this hurdle.

In the FDA briefing document, section 2 on page 5 "Regulatory Perspective on Potency for Cell Therapy Products", the final paragraph of this section on page 6. *Please note* I have added my notes in bold and underlined relevant points to the above, but read the full paragraph for context:
"The second approach [so that developers of cell-based therapies may progress] is to use clinical performance to demonstrate potency. For instance, if a product meets the primary clinical outcomes (tick for Ryoncil), has been extensively characterized during product development (tick for Ryoncil), and is produced by a well-controlled manufacturing process (tick for Ryoncil), these clinical data may be considered to demonstrate potency even if the mechanism of action is not completely understood. In this scenario, assays purporting to measure product attributes thought to be related to product potency must be sufficiently robust in terms of reproducibility and as indicators of product quality and stability. This approach can allow novel therapies with clearly demonstrated efficacy and well-controlled manufacturing processes to progress to licensure even if the mechanism of action and its relationship to the relevant potency assay are not completely understood"

MSB meets this second approach so the fact that the exact mechanism of action may not be entirely established should not be an issue. The FDA makes that incredibly clear in this paragraph.