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# Streamlining regulatory adoption of AAV gene therapies via producer cell lines
- URL: https://www.pharmamanufacturingiq.com/streamlining-regulatory-adoption-of-aav-gene-therapies-via-producer-cell-lines/
- Published: 2026-11-06T16:00:00.000Z
- Updated: 2026-11-06T16:00:00.000Z
- Author: Olivia Friett
- Tags: Policy & Regulation, Insights

**Vijetha Bhat, cell and gene technical expert, Lonza Specialized Modalities, Ramesh Koukuntla, head of MSAT, Lonza Specialized Modalities and Laura Sands, regional head, Regulatory Affairs, US Region 2 looks at the streamlining regulatory adoption of AAV gene therapies.**

As more adeno-associated virus (AAV) gene therapies enter clinical pipelines to treat diseases with larger patient populations, the technologies used to manufacture these therapies evolve with them. Today, AAV therapies are typically seen as a vehicle to treat rare diseases with small patient populations. To advance these therapies, developers use traditional transient transfection methods to enable rapid initial screening and follow an established regulatory path.

In recent years, with increased understanding of underlying molecular mechanisms and the progress of several clinical programs, AAV therapies are becoming more widely accepted as treatments for more common diseases, such as macular degeneration and Parkinson’s disease. This has led to an increasing number of potential treatment options entering clinical pipelines, addressing high unmet medical need with a proven record of safety and efficacy.

Among the current challenges of bringing AAV therapies that treat broader indications to market is a need to scale up the manufacturing process. For AAV therapy developers increasingly prioritising scalability, manufacturing feasibility and commercial viability, traditional transient transfection is unable to support the product volume necessary for a successful clinical program. These developers seek a more industrialised production method that allows for greater control and consistency at a larger volume and lower cost.

Whereas transient transfection introduces plasmid DNA temporarily into host cells resulting in AAV production with limited and costly scalability, producer cell lines (PCLs) allow for the permanent integration of viral genes into the host cell’s genome. This approach simplifies the production of AAV, enabling robust and controlled commercial-scale manufacturing. Additionally, the need for GMP-grade plasmids is eliminated, making the manufacturing process much more cost-effective.

**Assessing the approach to PCL**

Making the leap to PCLs from the dominant transient transfection technique is not a matter of simple process change. High on the list of considerations that developers in clinical stages must take into account when deciding to adopt PCLs is demonstrating to regulators that quality, safety and efficacy remain comparable to the original product, despite a fundamental change in process.

Regulatory agencies have not yet published final AAV-specific guidelines for comparability. Therefore, developers are left to explore the ways in which the transition between platforms will affect the product. Critical to determining whether a transition to a PCL is appropriate for a particular developer will depend largely on the stage of product development.

For regulators in the U.S. and Europe, a process change could trigger the need for additional data and bridging studies that demonstrate no meaningful impact on safety and efficacy to support future approval. Therefore, the shift should happen as early as possible in the development process, with regulatory requirements becoming increasingly burdensome to meet at later stages.

Those considering a PCL approach to make manufacturing more cost-friendly in the long term should ideally adopt the method prior to or early on in Phase 1 studies. If PCL development begins in preclinical stages before an investigational new drug application is filed, the likelihood for comparability to be required is minimised as material from polyclonal pools can be used to determine the most successful clones, providing the basis for early toxicology and safety studies.

After clinical trials have begun, comparability becomes a greater burden, and the developer may be required to conduct bridging studies to demonstrate that the risk assessment has not changed. The magnitude of the comparability exercise is generally commensurate with the product's stage of development and the potential impact on product quality, safety, and efficacy.

**Employing robust analytics**

When a comparability study is considered, it is important that robust analytics be used, including extended characterisation methods beyond the traditional release panel. These include methods that assess productivity, viral protein ratio, capsid protein post-translational modifications, genomic integrity, packaging efficiency and potency. Additionally, developers must continuously monitor the genetic and phenotypic stability of the cell line and potentially conduct stability studies that demonstrate consistent performance of the product over time.

The transition to a PCL process, in particular, could also have an impact on potency, which might require a dose reassessment and additional nonclinical or clinical studies. For all of these reasons, incorporating PCLs as early in development as possible is beneficial to minimising the need for comparability and bridging studies later in the product lifecycle.

CDMOs can support gene therapy developers by advising on regulatory considerations based on when they make the switch from transient transfection to a PCL method, ensuring that risk assessment and future manufacturing efficiency are prioritised. Determining the optimal transition time, maintaining a robust comparability strategy and generating data that aligns with regulatory expectations — all serve to help a developer meet the necessary requirements while setting them up for a more efficient manufacturing process.

While the current status quo for AAV gene therapy development remains transient transfection, the technology was never developed as a scalable manufacturing platform. As more of these therapies move through the clinical pipeline, developers will require processes that support higher volumes, better productivity and a more efficient supply chain.

With PCLs filling this gap and transient transfection still acting as a useful tool for early screening, there will likely continue to be a balance of both platforms in the AAV development space. As such, ensuring a smooth regulatory pathway through that transition will be critical to bringing more of these therapies to the market with greater speed and efficiency.