ABSTRACT
A seamless phase II/III trial design is a program that addresses within a single trial the objectives that are normally achieved through separate trials in phases IIb and III (Gallo et al., 2006; Chang et al., 2006). An adaptive seamless phase II/III design is a combination of phase II and phase III, which aims at achieving the primary objectives normally achieved through the conduct of separate phase II and phases III trials, and would use data from patients enrolled before and after the adaptation in the final analysis (Maca et al., 2006). In a seamless design, there is usually a so-called learning phase that serves the same purpose as a traditional phase II trial, and a confirmatory phase that serves the same objective as a traditional phase III study. Compared to traditional designs, a seamless design can not only reduce sample size but also shorten the time to bring a positive drug candidate to the marketplace. In this chapter, for illustration purposes, we will discuss different seamless designs and their utilities, through real examples. We will also discuss the issues that are commonly encountered followed by some recommendations for assuring the validity and integrity of a clinical trial with seamless design.
