Bringing Clarity to ATMP Analytics: The Value of Best Practice Guidance
The British Pharmacopoeia (BP) has recently published two new draft Advanced Therapy Medicinal Product (ATMP) Best Practice Guidance documents for consultation, focused on recombinant adeno-associated virus (rAAV) products:
- Characterisation of the capsid particle population in rAAV products: Determination of vector genome identity, integrity and encapsidated DNA impurities;
- Characterisation of the capsid particle population in rAAV product: Capsid protein characterisation.
These additions further strengthen BP’s growing portfolio of ATMP Best Practice Guidance, reflecting the increasing need for clear, practical, and harmonised approaches to analytics in advanced therapy development. Together, they address critical aspects of rAAV characterisation that are essential for understanding product quality, consistency, and safety.
Boyds’ clients are welcome to share their feedback with us by 20th March 2026, which we will incorporate into our response to the MHRA consultation.
The analytical challenge of ATMPs
ATMPs are transforming the treatment landscape, but their development presents a distinct set of challenges. The biological complexity of cell and gene therapies, combined with innovative and evolving manufacturing processes, places significant demands on analytical strategies across development, clinical, and commercial stages.
For ATMP developers, selecting and implementing appropriate analytical methodologies is rarely straightforward. Unlike more established pharmaceutical modalities, many of the analytical tools used for identity, potency, purity, and safety in ATMP development are still rapidly evolving. New technologies, platforms, and methodologies continue to emerge, often in parallel with the therapies themselves. Deciding which analytical methodologies to use, how to apply them appropriately, and how to ensure they deliver reliable, regulatory-compliant data can quickly become a minefield for developers.
While regulatory guidelines provide high-level expectations, they often stop short of offering practical, assay-level detail on how to implement these methods in a robust and harmonised way. This is where the ATMP Best Practice Guidance, developed by the British Pharmacopoeia (BP), plays a uniquely valuable role. At Boyds, we actively use the ATMP Best Practice Guidance to support clients in developing robust CMC strategies for advanced therapies, helping to translate analytical best practice into real-world development programmes.
Best practice guidance
The ATMP Best Practice Guidance, developed by the BP, offers a valuable and practical resource to help address this challenge. Distinct from traditional regulatory guidance, the ATMP Best Practice Guidance provides practical, consensus-based non-mandatory recommendations on the use of analytical tools commonly applied in cell and gene therapy development. Its focus is not on prescribing regulatory requirements, but on helping developers apply analytical methodologies in a more consistent, reliable, and scientifically sound manner, thereby supporting both product quality and patient safety.
To support this effort, the BP Commission established the Advanced Therapy Medicinal Products Working Party (ATMP WP). This group brings together subject matter experts from across industry, academia, and manufacturing, combining real-world experience in ATMP development with deep technical expertise in analytical science.
To date, the BP has published ATMP Best Practice Guidance covering several key analytical areas, including:
- Application of flow cytometry
- Vector copy number
- Characterisation of the capsid particle population in recombinant AAV products
- T cell and NK cell characterisation assays
- Replication-competent virus testing
The recent publication of the two draft rAAV characterisation documents for consultation further bolsters this portfolio, providing developers with deeper guidance on critical quality attributes related to capsid composition and genome content. Collectively, these documents offer practical insights into assay selection, execution, and interpretation, helping to promote greater harmonisation across the ATMP sector.
Looking ahead
The BP and the ATMP Working Party continue to expand their repertoire of analytical assay guidance in response to the evolving needs of the ATMP field. As cell and gene therapies progress toward broader clinical use and commercialisation, the importance of robust, standardised, and well-understood analytical methodologies will only continue to grow.
By providing practical, expert-led guidance, the ATMP Best Practice Guidance documents represent an important resource for developers navigating the complexities of ATMP analytics, helping to reduce uncertainty, improve data quality, and ultimately support the delivery of safe and effective advanced therapies to patients.
If you would like to discuss how robust ATMP analytics and CMC strategy can support your development program, get in touch with the Boyds team. Our experts work closely with developers to translate best practice guidance into regulatory-ready analytical strategies that support product quality, streamline development, and reduce regulatory risk across the ATMP lifecycle.
Moira Francois
Senior Manager, CMC Regulatory Affairs
Meet the author
Moira Francois is a senior CMC regulatory affairs professional with more than ten years of experience across ATMP analytical development, manufacturing, and regulatory strategy. She has worked extensively across cell and gene therapy programs, including leading CMC-focused regulatory projects at the Cell and Gene Therapy Catapult and supporting analytical assay development for pluripotent stem cell–based drug products. Moira also brings valuable insight into regulatory best practice through her contribution as a secondee to the MHRA British Pharmacopoeia’s ATMP Working Party. She joined Boyds as Senior Manager, CMC Regulatory Affairs, where she supports clients in delivering robust, science-led CMC strategies for advanced therapies.