An Adaptive Design for Multi-Arm Clinical Trials

The randomized play-the-winner (RPW) rule is very useful in clinical trials for patient allocation with two treatments. L. J. Wei (1979, Ann. Statist.7, 291–296) introduces the generalized Friedmanʹs urn (GFU) model to clinical trials of K treatments (as an extension of the RPW). In this paper, we propose a new adaptive design for multi-arm clinical trials. The proposed adaptive design proportionally depends on the success rates of each treatment, so that a treatment which is doing well is more likely to be assigned in future trials than a treatment which is doing poorly. The new design is more reasonable although it is no longer a GFU model. In the paper we show that the new design has some desirable asymptotic properties and that it has wider and easier applications in practice. Some simulations also support this new design.