I don’t see what’s wrong with the FDA approving a drug only for specific niche proximate-cause X that currently has absolutely no reason to ever be prescribed, presuming it’s disallowed from being marketed as being “for” anything other than specific niche proximate-cause X. Maybe someday a problem will come along that
can be solved by treating for specific niche proximate-cause X — and hey, then you’ve already got an approved drug to treat that problem. (For example, maybe in this case the drug could also happen to treat some novel prion disease, where the
mechanism of that prion disease involves beta-amyloid buildup, such that this drug would actually
stop that disease’s progression. Sort of the same way corticosterioids were already approved for other uses, but then happened to be able to be used in managing COVID, because the same mechanism they target — systemic inflammation — was being triggered by the disease.)
Of course, if the marketability restrictions truly worked the way I’m talking about, then the drug would have zero sales until that real-world problem matching its niche use-case came along. Which means there’d be no point in manufacturing it until then. But it’d be nice that it’d be “on the books” as being allowed to be produced and sold, such that it could be later rushed to market if the problem it solves was ever realized as a necessary problem to solve.