[jrumbut]

> in a control group

The control group gets the current standard treatment, not nothing (in case that was a source of confusion). Plus they typically don't have to pay for it which is a benefit for them.

Large trials today will typically conduct interim analyses and will have pre-defined guidelines for when to stop the trial because the new treatment is either clearly providing a benefit or is clearly futile.

Here is an example of such a study: https://www.ahajournals.org/doi/10.1161/CIRCHEARTFAILURE.111...