FDA's slow drift from two trials to one

The FDA recently announced it would shift from requiring two clinical trials to one. Why the change? In his Substack, Adam Kroetsh points out things have been moving in this direction a long time (the FDA has had the authority to approve based on a single trial since 1997 and most drugs approved these days are approved based on a single trial) at least partially in response to rising quality (and cost) of individual trials and an increasing focus on rare diseases.