TL2: Enriching patient population by response: placebo run-in, randomized withdrawal, sequential parallel comparison design (SPCD) and twice enriched design (TED).
*Anastasia Ivanova, University of North Carolina at Chapel Hill 

Keywords: placebo run-in, randomized withdrawal, sequential parallel comparison design (SPCD)

We discuss various ways to lower the impact of high placebo response on the success of a clinical trial. Existing proposals used in practice include (1) placebo or active lead-in designs and (2) the sequential parallel comparison design (SPCD) where the trial is conducted in two stages with each stage being sufficiently long to observe the outcome.