This year, the US Food and Drug Administration (FDA) has been tougher about approving new drugs based on non-inferiority trials &mdash and rightfully so, according to a report out this summer from the Government Accountability Office (GAO).

Non-inferiority trials pit an experimental drug against an established treatment in order to prove that the new drug does not perform any worse than its competitor. Some argue that, for conditions where there is already a drug available, this method is more ethical than placebo-controlled trials.

But the GAO report highlights the concern that non-inferiority trials lead to a phenomenon known as “biocreep”, where new drugs are approved that are slightly less effective than their predecessors, eventually leading to treatments that are no better than a placebo.

The FDA issued new guidelines in March of this year providing more specific suggestions to industry scientists on how to structure non-inferiority trials, including how best to select the drug control and what constitutes an acceptable margin of non-inferiority.