Cell-based potency testing provides quantitative data concerning a drug’s biological activity. Thus, it plays an essential role in biopharmaceutical quality control (QC), good manufacturing practice (GMP) product release, comparability determination, and stability testing for both drug products and drug substances. Potency is a critical quality attribute (CQA) often scrutinized by regulators and reviewers. Test methods are specific to a drug’s mechanism of action (MoA) and should be validated to internationally harmonized regulatory standards (1). The options preclude applying a simple…