I'm pretty sure the BBB is there for a reason, unavoidably there will be some side effects.

No, this removes plaques, and having plaques means you already have Alzheimers. This just slows or stops progression. Thankfully we seem to be developing ways to test for Alzheimers, so we should be able to catch it before any symptoms, and treatments to hold it in stasis. Reversing the damage is a whole different problem.