It is good to see in ICH guidelines a set of requirements for APIs that ought to be used in clinical trials. It is noted in Section 19.1 that process and test procedures should be flexible. Would the panel please comment on the interpretation of flexibility?

During development of the process, flexibility is needed because you are monitoring changes, adjusting parameters and making improvements to the process. This process evolution is  essential in deriving the final manufacturing process. Similarly, flexibility in analytical method development is also needed. However, you must fully document your changes along the way. A complete history is required for each batch.