Limb-Leaf designs for adaptive exploration of the dose-response curve.

We propose a two-stage strategy, called the Limb-Leaf method, to explore the dose-response curve using dose promotion and addition in the context of adaptive seamless Phase II/III trials. Strong control of the overall type 1 familywise error rate of the proposed method is enforced by the closed testing principle. The design constants are determined to minimize the risk-adjusted expected total sample size while maintaining a target power. In the case of a nonmonotonic dose response curve where more doses are required to adequately explore the curve, substantial savings in sample size are achieved compared with a traditional strategy which offers only selection and promotion from among initial first stage doses.