Comparability and Characterization in ATMPs Explained: Regulatory Frameworks, Best Practices, and 2025 Strategies Comparability and Characterization in ATMPs: A Regulatory Affairs Guide for Global Compliance Introduction to Comparability and Characterization in ATMPs Advanced Therapy Medicinal Products (ATMPs) — including cell therapies, gene therapies, and tissue-engineered products — are inherently complex due to their reliance on living materials and advanced biotechnologies. Unlike conventional pharmaceuticals, small manufacturing changes in ATMPs can alter safety, efficacy, or potency. Regulators such as the FDA, the EMA, and the CDSCO require sponsors to demonstrate comparability and product characterization whenever manufacturing processes, facilities, or raw materials change….