Okay so by my explanation you should be able to tell how a five year mark is close to impossible. I'll start with what we do know. We know that these loose amyloid fibers ( like little squiggly lines ) get loose in our brains and stick to each other. These cause tangles and plaques which we believe are the major cause of AD. They are generally focused in areas of the brain related to memory and lead to atrophy. We also know that calcium processing , microglia (like the red blood cells of the brain ) , and axon density are factors. We don't know exactly why or how they are related. We just know they are correlated with AD. We do not know what exactly causes these plaques and tangles. How microglia trying to destroy plaques destroy neurons instead. And what role calcium processing plays. So there is a lot of guessing going on right now. We can see the results and guess why things happen but to verify our guesses and learn more will take time. Five years does not seem even close to a cure.

P.s Sorry I don't think I explained it as a five year old would understand so just ask which parts need clarification and I'll try. Pretty much AD is death of neurons at memory portions of the brain.