What is a Synthetic Control Arm?
The question at the heart of most clinical trials relates to determining the treatment effect for one agent versus a placebo control. In the case of synthetic control arms, placebo arms are modeled using information that has previously been collected, instead of patients receiving a placebo. This data comes from sources including historical control data, real world data, or the generation of a companion data set from other sources to serve as a comparator.
There are already situations where the placebo can be avoided altogether. In oncology, for example, approvals are sometimes based on single-arm trials, where everyone receives the experimental therapy.
“When we’re looking at tumors, the response rate for untreated patients is known to be essentially zero, reflecting that tumors do not shrink on their own. As a result, if all patients in a trial are given a treatment, tumor reduction of sufficient magnitude and duration is believed to indicate treatment effect and can support approval,” Pulkstenis explains. “In this case the ‘control’ group is based on what we know historically about the course of untreated disease and the lack of placebo effect in this setting.”