Design Issues for Long-Term Maintenance Trials When the Comparator is Placebo
*Yeh-Fong Chen, FDA 


Randomized withdrawal trials are usually planned to assess the drug’s long-term maintenance efficacy since traditionally designed parallel-trials with placebo may not be suitable for a long-term study due to the ethical concern and possible high dropouts. The randomized withdrawal trial has the open-label stabilization phase and the post-randomization phase. A design with an appropriate length of the open-label stabilization phase is very important since the claim of long-term maintenance efficacy is usually based on the length of the stabilization phase. Is the length of the post-randomization phase important, too? Will it affect the analysis results? Are there any other designs that can be used to assess the drug’s long-term maintenance efficacy?