Also, it's not up to the FDA if the trial continue
Post# of 148176
DMSC stops the trial if it's amazing because it is unethical to let people die on the placebo who could be saved if they get the drug. Or they stop it for futility. It's not really working (underwhelming as you say) and very unlikely to meet its endpoints. Or they stop it because it is harmful and we already know that it isn't.
They let it continue if it's good, but not quite good enough to reach statistical significance with a small number of people.