The process analytical technology (PAT) and quality by design (QbD) guidelines promoted by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) support the idea that quality cannot be “tested into” a biologic product but must instead be part of its process design. Seamless integration of analytical data with bioprocess monitoring and control is crucial to understanding a process and overcoming manufacturing challenges that arise in the course of development. Monitoring of product quality attributes (PQAs)…