ABSTRACT
This chapter describes in addition to the Food and Drug Administration's (FDA) recommended switching design, several useful switching studies such as Balaam's design, 2 × 3 dual design, replicated 2 × 2 design, and complete N-of-1 trial designs with two, three, and four periods. It provides review and comments on FDA's draft guidance on analytical similarity assessment. The chapter describes several recent developments in the past few years that include a unified approach considering effect size adjusted for standard deviation for analytical similarity assessment proposed by Shein-Chung Chow et al. It also includes several useful switching designs including complete N-of-1 trial design following the general principles as described in the FDA draft guidance on interchangeability and the concern of off-label non-medical switch post-approval. Three types of hybrid parallel-crossover designs are commonly used to address drug interchangeability, which are parallel plus 2 × 2 crossover design, parallel plus 2 × 3 crossover design, and parallel plus 2 × 4 crossover design.
