They don't. Drug treatments for alzheimer's don't affect genes like apo e4. Their intent is to treat the aftermath (the cognitive symptoms of alzheimer's disease itself). Young people with this gene should read dr. David perlmitters new book, "grain brain, " which makes a strong research-based case for gluten and other sugars being linked to alzheimer's and many other problems. http://tinyurl.com/mof6qj8.
Reality of Alz meds. We have no truly effective meds on the market, only modest interventions which slightly slow the deterioration & improve behavior. The meds preserve acetylcholine function, and block glutamate damage, but do not affect genetics or the pathological lesions. Some approaches such as intranasal Insulin seem to briefly improve function, and axona and cerefolin-nac may help early on. Research proceeds.