Evaluation of Performance of Some Enrichment Designs Dealing with High Placebo Response in Psychiatric Clinical Trials
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*Yeh-Fong Chen, FDA 

Keywords: placebo response, enrichment design

A widely-used design strategy for dealing with the high placebo response commonly observed in trials of psychiatric disorders is to implement a placebo lead-in phase prior to randomization. In recent years, alternative strategies—including a sequentially parallel design (Fava et al., 2003) and a two-way enriched clinical trial design (Ivanova and Tamura, 2011) containing two consecutive double-blind treatment stages—have been proposed. The advantage of these new designs over the traditional placebo lead-in, however, is not always clear. In this presentation, I will discuss the features of these designs, focusing particularly on the evaluation of their performance with respect to continuous measures. In addition to sharing my view on their effectiveness, I will offer suggestions for possible improvement.