What are process characterization studies and how are they designed?

Process characterization studies systematically evaluate how process parameter variations affect product quality and process performance. Design includes: identifying process parameters to evaluate (from process knowledge and risk assessment), determining ranges to study (operating vs characterization ranges), selecting appropriate study design (factorial, response surface), executing studies at appropriate scale (scale-down models), and analyzing data to establish parameter criticality and interactions. Outputs include: classification of parameters as critical (CPPs) or non-critical, proven acceptable ranges (PARs), and linkage to CQAs. Studies support regulatory filings, establish control strategies, and define design space. Proper scale-down model qualification is essential for relevance.