this question was specifically discussed at adcom, and panel favor post-approval study.
fda panel has to weight risk of any side effect, with unmet need. in this case, there is not sufficient evidence of risk, to let patients with unmet need wait for this drug. hence, post-approval study.
Point taken and appreciate your opinion. I understand this is an unmet need, but what if the side effects outweigh the benefits? Wouldn't the FDA request pre-approval study just to make sure the product is safe? On the other side, I can also see this to be post-approval since the FDA had time ( and didn't though) to request pre-approval study and they haven't at this time, so why would they come next month or days before the FDA decision and say, oh we'd need a pre-approval study? not that they've done this before, but given all the time they had and never made it a requisite