Indeed it's very promising that humans reacted the same way that mice did to the drug. So often a drug that works in mice does NOT work in humans -- there was an article recently detailing the horrific magnitude of the NON-correlation of drugs that worked in mice and the effects (non-effects) of the same drugs in humans. So this is great news.

However to say that Rett is harder to treat than Alzheimer's -- I do not agree with that at all. We have NO idea of what the true mechanism of action is that causes Alzheimer's (some people with horrible amyloid tangles, discovered upon autopsy, had NO dementia symptoms while they were alive) -- so we don't have any idea whether it's harder to treat Rett.

Personally, I think that Rett is "easier" to treat -- because when people are severely ill, they die. And when people have dementia, it can take decades for them to have the blessing of relief from the horrendous disease.
If this sounds cruel to you, you have never known someone who has been debilitated for years with dementia, and for whom death is truly the best outcome. I have had people with dementia look at me and say "help me" and I knew exactly the kind of help they wanted.