What is the meaning of "phase-appropriate" in the test method development and validation?

"Phase" is the stage of clinical study. Usually, it is separated by registration batches. All activities before the registration batches are considered early phase, and any after it are considered late phase. The CMC requirements on the early phase and late phase are somewhat different. In the method development and validation, the following tables summarize the differences in the author's past experiences.

Table 1. Phase-appropriated Development Requirements for analytical methods (use small molecule assay and impurities HPLC method as the example)

	​Early Phase	Late Phase
Method combination	Assay and related substances methods are usually combined.	Assay and related substances methods are usually separated.
​HPLC gradient	Large gradient range to ensure all impurities are covered.	Smaller gradient range to have a better peak separation.
Impurity calculation	Usually use area%	Use w/w%
​Peak separation	Impurities are recommended to be baseline-separated from main peak, but individual impurity peak is not required to separate from each other.	​Impurities are required to be baseline-separated from main peak, and from each other.
​Method Validation readiness	Qualification is sufficient	​Complete validation before PPQ batches
Method validation design	Specificity (forced degradation) Accuracy Precision Linearity LOQ and LOD Solution Stability	Specificity (forced degradation) Accuracy Precision Linearity LOQ and LOD Solution Stability Intermediate Precision Robustness