However, in doing so, the principle of equipoise—recognized by many as the primary ethical justification for an RCT, any RCT—loses some of its force. You might still find it, but the emphasis is elsewhere: on "social value," on "scientific validity," on "independent review," on "respect," on "informed consent." Important values all, but by deconflating research from treatment, investigators are relieved from the constraints of the personal-care principle and the absolute prohibition against doing harm. The deconflation has defeated equipoise.
Source: wiktionary