Ann: Long-Term Survival for Acute GvHD Treatment with Remestemcel, page-34

The major problem being from the FDA's point of view that the numbers are small with significant variability and comparisons between different trial data are not readily comparable. The phase 2 trial from Osiris showed promising results while two subsequent larger phase 3 trials showed that those were simply outcomes due to statistical chance.

So I think the FDA still have a problem with the quality of the MSB trials in regard to efficacy, which is why they requested a further properly controlled trial. And it's likely to be the reason SI is resisting it because he knows there is a substantial risk of failure and is desperate to get some revenue.