IVIG is approved in quite a number of indications! Baxter seems to be adding a new one every year or so. Is Alzheimer's a longshot? Probably a bit, but I think its got as good a shot as any other Phase-3.
Just to be clear: the viability of MNTA’s enhanced-IVIG program does not depend on the success of BAX’s Gammagard in AD. Even without AD, manufacturers of IVIG are selling everything they can make, and this is unlikely to change even with some new plasma-collection capacity coming online. (You undoubtedly know all this, but some readers of this board might not.)
Contrary to your statement above, I would say that the Gammagard phase-3 program in AD is considerably higher-risk than a typical phase-3 program; however, this doesn’t have any material effect on MNTA.