An interview with Lisa Prendergast for Next Generation Gene Therapy Vectors Conference

Q: For adeno-associated virus (AAV) and lentiviral vector (LV) production, there remains an ongoing debate about whether to rely on transient transfection or stable producer cell lines. Could you elaborate on the differences between these methods and when a drug developer might choose one over the other?

Currently, the most common method in viral vector production is transient transfection. In this process, plasmid DNA encoding viral genes is introduced into cells, leading to high-level expression of the desired virus over a short time frame, typically 48 to 72 hours. This method is advantageous due to its rapid implementation, flexibility for process development, and suitability for early-stage production. The cells used for expression are generally in suspension, contrasting with older manual methods that utilized open and adherent systems.

The industry has made significant strides by moving towards closed systems using bioreactors, which have improved production consistency, robustness, and scalability. This evolution has established transient transfection as the standard method in our industry. Furthermore, engineering approaches have been focused on enhancing the plasmids used for transient viral production, which can improve both titer and product quality characteristics.

Despite these advancements, challenges persist. Issues such as limited plasmid availability, scalability concerns, and high production costs remain significant hurdles. Looking to the future, stable producer cell lines present a promising solution for improving quality and reducing the overall costs associated with new gene therapy drugs. This approach involves integrating the genes necessary for production directly into a single stable cell line. Not only does this reduce costs, but it also enhances the reliability of the supply chain and offers a scalable solution that maintains high quality.

Drug developers might opt for transient transfection for its rapid process development capabilities and ease of use during early-stage production. However, stable producer cell lines become preferable for large-scale, consistent manufacturing needed in late-stage clinical trials and commercialization. The size of the target therapeutic population also significantly influences the choice of approach. The industry's shift towards stable producer cell lines underscores the importance of standardizing viral vector manufacturing. It is exciting to witness how this technology is evolving to meet our needs and set the stage for more efficient and cost-effective production in the future, ultimately facilitating access to new gene therapies for a broader patient population.

Q: A hot topic right now is developing platform approaches for clinical and commercial-stage viral vector production. What are the considerations for taking a platform approach versus using customized processes?

The decision to adopt a platform approach or a customized process largely depends on the specific properties of the therapeutic being developed, and these options are not necessarily mutually exclusive. Different serotypes, both native and engineered, exhibit varying expression levels, and the transgene sequence carried by the capsid can also impact expression levels and the ratios of full to empty capsids.

Utilizing an established platform approach typically involves standardized processes, equipment, and methodologies, which may include specific cell lines and plasmids. The primary emphasis of this approach is on process optimization, scalability, and, most importantly, consistency.

Standardization can lead to more predictable outcomes and facilitate technology transfer between different manufacturing sites. On the other hand, customized processes may be necessary to address specific vector characteristics or unique therapeutic needs. This approach allows for the tailoring of production methods to accommodate specific vector types, such as engineered capsids, or to meet individual product requirements, such as achieving a specific ratio of full to empty capsids. While customized processes offer flexibility and the ability to address unique challenges, they may require more resources and time for development and optimization.

Ultimately, the choice between a platform approach and customized processes should be guided by factors such as the specific properties of the therapeutic, the scale of production, regulatory considerations, development timelines, and available resources. A hybrid approach that combines elements of both strategies can also be beneficial, allowing developers to leverage the efficiency of a platform while still addressing the unique requirements of individual products.

Q: As Lonza's subject matter expert for exosomes, your talk at the Next Generation Gene Therapy Vectors Summit in June will touch upon your work exploiting them as natural nanocarriers for delivering a range of cargo. Could you share more about the latest research with exosome-mediated drug delivery?

Extracellular vesicles (EVs), particularly exosomes, show tremendous promise as vehicles for drug delivery due to several key advantages. These include their ability to carry diverse cargo, their innate immune evasion capabilities, and their low risk of toxicity. Additionally, EVs can be re-dosed, which is a significant advantage over other modalities like AAVs, where immune responses can limit re-administration. Research and development efforts, particularly those spearheaded by companies like Codiak Biosciences, have driven advancements in engineering technologies that enable the creation of customized engineered exosomes or EVs. These engineering approaches provide the flexibility to tailor specific properties of the EVs, allowing for the effective loading and targeted delivery of therapeutic payloads.

At Lonza, we are proud to introduce the Xcite^® EV platform, which facilitates the generation of engineered EVs. This platform leverages two proteins that are endogenously associated with exosomes, namely PTGFRN and BASP-1. These proteins are utilized to load cargo onto the surface or into the lumen of the exosomes. The loading process is accomplished through the use of engineered plasmids, which make the linking and loading technologies readily accessible to researchers and developers.

A significant advantage of the Xcite EV^® platform is its clinical validation, demonstrated through successful Phase 1 trials of Codiak's three clinical assets: exoSTING™, exoASO-STAT6™, and Exo-IL-12™. These therapeutic examples showcase the platform's versatility in transporting various types of therapeutic payloads, including small molecules (such as STING agonists), proteins (like IL-12), and nucleic acids (such as antisense oligonucleotides).Looking ahead, our aim is to leverage this technology to support new EV-based drug programs in the field. The potential applications of exosome-mediated drug delivery are vast, and ongoing research is focused on optimizing vector selection and design with scalable and efficient manufacturing in mind.

Q: What advice would you give to early-stage drug developers looking to equip themselves with delivery platforms that will allow for scalable manufacturing downstream?

When embarking on the gene therapy development journey, two critical factors that can have a substantial impact from the outset are scalability and quality. My advice to early-stage drug developers is to consider scalability from the beginning and to evaluate whether their chosen approach aligns with a pathway to commercial manufacturing. For instance, starting with an adherent process for generating initial material may necessitate transitioning to a suspension process later for scaling up during Investigational New Drug (IND) enabling or clinical studies.

Partnering with a Contract Development and Manufacturing Organization (CDMO) can be highly beneficial for developers. This collaboration allows them to leverage established, validated platforms that have successfully generated commercial products. By selecting a versatile platform capable of accommodating various therapies, developers can ultimately save time and costs in the long run.

Early emphasis on quality and consistency is critical. It is essential to establish processes that yield dependable results and meet regulatory standards as developers progress toward larger-scale manufacturing. Investing time in robust process development upfront pays dividends later by facilitating smoother scaling and navigating regulatory requirements more effectively.

Q: Why are you excited to take part in the Next Generation Gene Therapy Vectors Summit this year?

I am particularly excited about participating in the Next Generation Gene Therapy Vectors Summit due to the exceptional program that has been organized. This year, there are several highly innovative approaches from developers aimed at addressing challenges in the therapeutic implementation of gene therapies, particularly concerning targeting and toxicity. The strong focus on payload design is also very promising. The summit provides a fantastic opportunity for engaging discussions over the course of a few days.