A two-way enriched clinical trial design merging placebo lead-in and randomized withdrawal
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Anastasia Ivanova, University of North Carolina - Chapel Hill  *Roy Tamura , University of South Florida 

Keywords: enriched trial, score tests, sample size

A new clinical trial design, designated the two-way enriched design (TED), which augments the standard randomized placebo controlled trial with second stage enrichment designs in placebo non-responders and drug responders is described. The trial is run in two stages. In the first stage patients are randomized between drug and placebo. In the second stage placebo non-responders are re-randomized between drug and placebo and drug responders are re-randomized between drug and placebo. All first stage data, and second stage data from first stage placebo non-responders and first stage drug responders, are utilized in the efficacy analysis. We define 1, 2, and 3 df score tests for the TED. The TED is compared to the standard parallel trial, placebo lead-in and randomized withdrawal trials in terms of sample size (entered and randomized) for a Phase 2 trial in generalized anxiety disorder.