Describe the three stages of process validation for biologics manufacturing.

FDA and ICH guidance describe three-stage lifecycle approach to process validation: Stage 1 - Process Design: Define commercial process based on development knowledge; identify critical quality attributes (CQAs), critical process parameters (CPPs), and proven acceptable ranges; establish control strategy; risk assessments (FMEA); small-scale studies and DoE to understand parameter interactions. Stage 2 - Process Qualification: PPQ (Process Performance Qualification) runs at commercial scale; demonstrate process consistently produces quality product; typically 3+ consecutive successful batches; prospective validation before commercial distribution; qualification of equipment and utilities. Stage 3 - Continued Process Verification: Ongoing assurance of validated state; statistical monitoring of process parameters and quality attributes; trend analysis; identify improvement opportunities; revalidation triggers. Supports continuous improvement rather than one-time validation event. Concurrent validation acceptable in limited circumstances.