10/06/2026
Gene therapy development has expanded rapidly over the past decade, moving beyond a predominantly viral vector centric paradigm to encompass a broad range of therapeutic modalities. These include adeno associated virus (AAV) and lentiviral vectors (LVV), lipid
nanoparticle (LNP)–based nucleic acid delivery systems, mRNA therapeutics, and gene editing platforms such as CRISPR based systems1–3. Each modality presents distinct scientific, manufacturing, and analytical challenges, yet all are subject to increasing
regulatory scrutiny and rising expectations for product understanding and control.
As gene therapies advance towards later stage clinical development and commercialisation, analytical complexity has increased substantially. Products are often structurally heterogeneous, biologically complex, and highly sensitive to subtle changes in manufacturing or formulation2,4. Regulatory authorities now expect a clear demonstration of control over critical quality attributes (CQAs), supported by scientifically justified, phase appropriate analytical methods that evolve coherently across the product lifecycle1,3.
In practice, however, analytical strategies are frequently developed in a reactive and siloed manner. Methods are introduced to address immediate development questions or specific regulatory feedback, often without sufficient consideration of long term suitability, integration across datasets, or future comparability needs4. This fragmented approach can introduce significant technical and regulatory risk as programmes mature.
An integrated, lifecycle based analytical strategy is therefore essential. Such a strategy recognises both the common principles that underpin gene therapy analytics and the modality specific considerations that must be addressed to ensure robust product
characterisation, control, and regulatory alignment from early development through to commercial release.
CQAs provide the foundation for analytical strategy and control across gene therapy products. While the specific attributes differ between modalities, CQAs generally reflect the interdependence between product structure, delivery, and biological function2,4.
Potency and biological activity
Potency is a universal CQA, yet it is one of the most challenging to define and measure for gene therapies. For viral vectors, potency is typically linked to transduction efficiency and transgene expression, whereas for LNP based mRNA or gene editing systems it may reflect protein expression levels, editing efficiency, or functional correction of a disease relevant pathway1,5,8.
Across modalities, regulators increasingly expect potency assays to be biologically relevant, mechanistically justified, and sensitive to meaningful changes in product quality1,3. Importantly, early stage assays must be evaluated for their ability to evolve into
quantitative, reproducible methods suitable for late phase development and commercial control.
Particle or delivery system characterisation
Delivery systems are central to gene therapy performance. Viral vectors require characterisation of capsid integrity, empty and full particle populations, and aggregation state5,6. LNP based systems are defined by particle size distribution, polydispersity,
encapsulation efficiency, and lipid composition8,9. Gene editing platforms may involve multi component delivery systems, further increasing analytical complexity10.
Across modalities, physical attributes are often closely linked to biodistribution, efficacy, and safety, reinforcing the need for robust and orthogonal characterisation strategies.
Genome or payload integrity
Integrity of the genetic payload is critical for potency, safety, and stability across all gene therapy modalities. This includes confirmation of sequence identity, detection of truncation or degradation, and assessment of stability under long term and stressed conditions1,4,5. For gene editing systems, this extends beyond the delivered payload to include characterisation of on target and off target editing outcomes10.
Purity and impurities
Impurity profiles vary by modality and manufacturing process, but commonly include host cell proteins, residual DNA, process related impurities, and product related variants2,4,5. LNP and mRNA based systems introduce additional considerations such as residual solvents, lipid related impurities, and double stranded RNA species8,9. Regulatory guidance increasingly emphasises risk based justification of impurity control
strategies rather than purely prescriptive testing1,3.
Despite increasing industry experience, analytical strategies for gene therapies are often fragmented. Assays may be developed to address specific development questions or regulatory feedback without alignment to long term lifecycle needs4. Common challenges include lack of alignment between R&D, process development, and QC functions, and late
introduction of new analytical technologies without sufficient comparability planning.
The consequences are well recognised across the industry: assay redevelopment late in development, complex comparability exercises during scale up or site transfer, and regulatory delays due to inconsistent or insufficiently justified datasets1,3,4.
Early development (Discovery/Preclinical)
Early development prioritises scientific understanding and flexibility. Analytical methods are often exploratory and support candidate selection, mechanism of action studies, and early risk identification2,5. At this stage, the focus is on identifying potential CQAs rather than establishing tight analytical control.
Early clinical development
As products enter clinical development, expectations shift towards improved reproducibility and standardisation. Key assays are refined, variability is reduced, and preliminary controls may be introduced. Regulatory guidance emphasises that methods
selected at this stage should be assessed for their suitability to support later phase development and potential commercialisation1,3.
Late phase development and commercialisation
Late phase and commercial products require fully validated, stability indicating methods aligned with global regulatory expectations1,3,4. Assays must be robust, transferable, and capable of supporting routine release, stability, and comparability testing. At this stage, analytical changes carry significant regulatory risk.
Across all gene therapy platforms, analytical methods mature as products progress through development. Viral vector programmes often transition from research grade titre or expression assays to validated, quantitative methods suitable for release and stability5,6.
LNP based systems may evolve from basic particle sizing techniques to more discriminating, orthogonal approaches as control requirements increase8,9. Gene editing platforms require progressive refinement of methods to assess editing efficiency, specificity, and long term effects10.
Anticipating these transitions early reduces the burden of late stage bridging studies and supports data continuity across the lifecycle4.
Given the complexity of gene therapy products, no single analytical method can provide a complete picture of product quality. Orthogonal approaches-combining functional, structural, and molecular assays-are therefore essential2,4. Data triangulation of multiple analytical methods improves confidence in product understanding, supports robust comparability assessments, and strengthens regulatory justification across modalities.
Change is inevitable across the gene therapy lifecycle, driven by process optimisation, scale up, manufacturing site changes, and platform evolution. Regulatory guidance consistently emphasises the importance of risk based comparability strategies supported by appropriate analytical data and scientific justification1,3,4. Proactive planning for analytical change is therefore a core element of an integrated strategy.
Early analytical planning delivers tangible benefits, including reduced development risk, more efficient progression to clinic and market, and stronger regulatory alignment1,4. While strategies must be tailored to individual modalities, they should be built within a unified framework that balances early stage flexibility with late stage robustness.
As gene therapy portfolios diversify and development timelines compress, the limitations of fragmented analytical support models become increasingly apparent. Discrete outsourcing of individual assays or development stages can lead to inconsistent datasets, loss of contextual knowledge, and increased risk during comparability and regulatory review4.
An integrated analytical partner provides continuity across the product lifecycle, acting as an analytical steward rather than a collection of isolated testing services. This includes cross modality expertise, end to end analytical capability, alignment with broader CMC strategy, and holistic data interpretation across complex datasets.
EBPT Ireland operates within this integrated framework, supporting gene therapy programmes by combining modality specific technical depth with a unified analytical approach. By maintaining continuity of methods, data, and scientific understanding across development stages, this model supports efficient method evolution and coherent regulatory narratives across viral and non viral modalities.
Potency for AAV products is commonly linked to transduction and transgene expression5,6. However, experience shows that early expression based assays may not detect changes in capsid composition or genome integrity that become clinically relevant during scale up or process change5.
Capsid related attributes such as empty/full ratios, aggregation, and capsid damage have been linked to changes in effective dose, biodistribution, and immunogenicity risk5,6. Similarly, loss of genome integrity can result in reduced potency or stability without
obvious changes in titre, underscoring the importance of stability indicating genome assays5.
For LNP based systems, biological activity depends on efficient delivery, endosomal escape, and payload function8,9. Changes in particle size distribution, encapsulation efficiency, or RNA integrity during scale up or tech transfer have been associated with altered in vivo performance despite comparable nominal metrics8. As with viral vectors, orthogonal methods and early lifecycle planning are essential to manage these risks effectively.
As gene therapy modalities diversify and regulatory expectations increase, integrated, lifecycle focused analytical strategies are no longer optional. Fragmented, reactive approaches introduce unnecessary risk and inefficiency. In contrast, strategies grounded in scientific understanding, orthogonal analytics, and cross modality expertise support robust development, efficient regulatory interactions, and successful commercialisation across the evolving gene therapy landscape.