I thought that this only happened if the drug was saving lives? I think that OM is considered more of a quality of life issue much like psoriasis.
"If the treatment shows overwhelmingly positive results, the IRB, or the DSMB can also prematurely stop the trial and allow all participants to cross over into the more effective treatment arm of the trial. It is considered inhumane to keep people on placebo if the trial is safe and overwhelmingly efficacious." - baytdr