Phase II clinical trials investigate whether a new drug or treatment has sufficient evidence of effectiveness against the disease under study. Two-stage designs are popular for phase II since they can stop in the first stage if the drug is ineffective. Investigators often face difficulties in determining the target response rates, and adaptive designs can help to set the target response rate tested in the second stage based on the number of responses observed in the first stage. Popular adaptive designs consider two alternate response rates, and they generally minimise the expected sample size at the maximum uninterested response rate. Moreover, these designs consider only futility as the reason for early stopping and have high expected sample sizes if the provided drug is effective. Motivated by this problem, we propose an adaptive design that enables us to terminate the single-arm trial at the first stage for efficacy and conclude which alternate response rate to choose. Comparing the proposed design with a popular adaptive design from literature reveals that the expected sample size decreases notably if any of the two target response rates are correct. In contrast, the expected sample size remains almost the same under the null hypothesis.

II期临床试验调查一种新药或治疗是否有足够的证据证明对研究中的疾病有效。两阶段设计在第二阶段很受欢迎，因为如果药物无效，它们可以在第一阶段停止。调查人员在确定目标响应率时经常遇到困难，而自适应设计可以帮助根据第一阶段观察到的响应数量设置在第二阶段测试的目标响应率。流行的自适应设计考虑了两种替代响应率，它们通常以最大无兴趣响应率最小化预期样本量。此外，这些设计仅将无用性视为提前停止的原因，并且如果提供的药物有效，则具有较高的预期样本量。受到这个问题的启发，我们提出了一种适应性设计，使我们能够在第一阶段终止单臂试验以获得疗效，并得出选择哪种替代反应率的结论。将提议的设计与文献中流行的自适应设计进行比较表明，如果两个目标响应率中的任何一个是正确的，则预期样本量会显着减小。相反，在原假设下，预期样本量几乎保持不变。