This isn’t exactly news, but it’s news to me: Rapamycin has an orally administered derivative, Everolimus, already in use as an anti-cancer and anti-rejection drug. (The two compounds are almost identical; Everolimus has one additional hydroxyethyl group on the protuberant cyclohexane ring, and apparently that’s enough to make the unwieldy rapamycin molecule orally bioavailable.)

This might be good news if it turns out that the longevity-enhancing qualities of rapamycin end up generalizing to humans: If you need to maintain constant levels of a chronically administered drug, t’s way easier to use timed-release oral capsules than injections. Also, as millions of diabetics will tell you, it’s just nice not to have to shoot up.

But the drug itself might be bad news, especially if it is taken over long periods of time: mTOR, the target of rapamycin, appears to be necessary for reconsolidation of long-term memory in mammals; inhibition of mTOR is efficacious enough at blocking fear memories that it’s discussed as a strategy for treating PTSD. The role of mTOR in memory appears to be general, i.e., in memories other than fearful ones, and it is evolutionarily ancient: TOR is important for long-term potentiation in the sea slug Aplysia, beloved model of scholars of learning and memory.

So, as I’ve commented before, I have this fear that rapamycin (or a derivative) will turn out to be a bona fide longevity enhancement drug, but one whose chronic use erodes long-term memory, which does defeat the purpose to some extent.

Then again, blood-brain barrier is an issue here: even though Everolimus can survive the stomach and pass through the gut into the blood, that doesn’t mean it will make it into the brain efficiently. Then again again, if the drug has a long half-life once it’s inside the brain, it might still accumulate there if one had to take it every day for the rest of one’s life.

On the happy side, if you find this possibility traumatic, the rapamycin will take care of that for you.

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