How do process design, PPQ and continued verification differ?

Why

Stage 1 integrates development experiments, material attributes, scale-up knowledge and risk assessments to define the commercial control strategy. Stage 2 includes qualification of facilities, utilities and equipment plus process performance qualification that tests the defined process against prespecified criteria. Stage 3 trends ongoing manufacturing data to detect drift and continuously assess the state of control.

For instance, cell-culture experiments may establish an acceptable dissolved-oxygen control range, PPQ tests commercial execution, and later production monitoring detects progressive sensor bias. The stages share data and may inform each other, rather than being a one-way checklist. A passing PPQ study does not mean monitoring can stop, and a process change may send the team back to earlier development and qualification activities.