Multi-arm clinical trials with treatment selection: what can be gained and at what price?

With current success rates of confirmatory studies being only around 50%, new approaches to drug development are paramount. Many trials fail simply because ineffective treatments are identified too late. In this paper, we discuss the utility of multi-arm studies with treatment selection as a potential strategy that can reduce the high attrition rate. We illustrate the large gains in efficiency that are possible based on an example in Alzheimer's disease while outlining the additional challenges that need to be overcome to implement such studies.