As gene therapy products race towards the clinic and commercial launch, sponsor companies are faced with significant hurdles posed by evolving manufacturing platforms, process improvements across multiple stages of development, and a rapidly growing toolkit for the characterization of viral vectors. Taken together, this creates a complex landscape for demonstrating comparability driven by process changes. Further, a lack of specific regulatory guidance on viral vector comparability studies pushes gene therapy companies to adapt and interpret principles of ICH Q5E for demonstrating comparability of biological products when changes are made in their manufacturing processes. As ICH Q5E guidelines are not fit for purpose in the context of Advanced Therapy Medicinal Products (ATMP), different approaches have been adopted across the industry to define comparability studies. The ISPE ATMP Guide: Recombinant AAV Comparability and Lifecycle Management considers requirements and guidance for recombinant Adeno-Associated Virus (rAAV) manufacturing and comparability from the US FDA, EU EudraLexVolume 4 Part IV, EMA Q&A, and ICH Q5E. Drawing on a team of industry experts with global experience, the Guideprovides current understanding and best practices on rAAV comparability exercises, offering manufacturers a standardized approach for developing process and product comparability strategies. It provides considerations for evaluating rAAV vector products comparability pre and post-change to the manufacturing process and proposes strategies to address the unique challenges posed by this new class of products. The Guide is intended as a reference and practical guide for addressing common challenges that may arise when demonstrating comparability across the rAAV product lifecycle. It discusses host cell type selection, rAAV gene delivery methods, and the advantages, disadvantages, and impact on upstream and downstream operations, including differences in impurity profiles depending on the platform used. Comparison of scale-out versus scale-up of unit operations is included. An extensive list of analytical techniques applicable to rAAV comparability studies is explored that should support virtually any type of rAAV product comparability study. Process changes may occur throughout product development and after approval for various reasons. While a comprehensive list assigning risk to specific process changes is not possible given the product-dependent nature of these risks, the Guide contains general observations about levels of risk associated with common changes. Strategies for considering this knowledge with the analytical tools presented to develop comparability studies at various stages in the product lifecycle are described. In addition, the Guide presents three realistic case studies for changes likely to be encountered during an rAAV product’s lifecycle. They cover various phases, pre-clinical, clinical, and commercial, detailing changes, how to assess them, what kind of development and characterization data should be generated, how the data informs the comparability protocol, and what additional considerations should be included in the comparability protocol.