[protomyth]

Ok, but don't we have a body of knowledge on Alzheimer's that having another control group is redundant? Why do we keep needing new control groups for things that are going to kill people and we know are going to kill people? I cannot get by the ethical problem of knowing we're kill 50% of the people in the study to provide data we already have.

[toast0]

The problem is, if something related to how you run your test of the anti-fungal has an effect on the disease, you're going to assume its the anti-fungal; but maybe it's not. If you have a control group, and both groups do better than expected (compared to the body of evidence), then you've learned something you wouldn't have without a control group (and you'll have to work hard to figure out what changed in this study vs other studies). If anti-fungals are a clear winner, it's likely that the study protocol would be changed to give everyone the drug after early results.