ABSTRACT
The terms “intrinsic and extrinsic factors” in drug development were first described in the late 1990s as part of ICH E5 guidelines. Identifying these factors early in drug development as a pre-consideration would help in the design of multiregional clinical trials (MRCT). While there are bound to be intrinsic and extrinsic differences, identifying those differences early and managing these differences that affect the treatment effect will determine the success of MRCT. This chapter will provide a historic perspective of how the terminology used in ICH E5 and E17 guidelines are interpreted and applied for the conduct of MRCT.
