Interview: How to Achieve Scalable Production of Gene Therapy Vectors

1 Adenovirus Cevec Kateryna Kon

Over the past few years there has been a significant increase in gene therapy research. Past programs have mainly addressed rare or very rare diseases. Consequently, the manufacturing methods for gene therapy vectors are only set out to meet the market demands of a relatively small number of patients. Today, this is a problem.

Progress in gene therapy-based treatments for more common indications, such as Alzheimer’s, Parkinson’s, or Rheumatoid Arthritis means that gene therapy vectors will have to be produced on a much larger scale in future. To date, the amount of material that can be manufactured suits phase I or phase II clinical trials.

However, the problem arises as soon as trials reach phase III or when therapies hit the market. Current gene therapy vector manufacturing methods are just not made for a large scale production, which can cover the demand. This production gap is one of the greatest challenges that industry experts are facing in the field.

Dr. Nicole Faust, CEO and CSO at Cevec

We have caught up with Dr. Nicole Faust, CEO and CSO of the biotech company CEVEC, which focuses on the development of manufacturing platforms for the creation of proteins previously out of reach and the scalable production of viral vectors. Nicole and her team have taken it upon themselves to address the issue of upscaling, by creating cell lines that can be grown in suspension in bioreactors of increasing capacity.

Nicole has told us all about the importance of scalable production systems. She has also introduced CEVEC’s novel helper-virus-free stable production system for Adeno-Associated Virus (AAV) vectors for which the company has provided a scalable manufacturing solution in order to meet the industry’s increasing demand for gene therapy vectors.

Nicole, why is the stable, scalable production of gene therapy vectors so important?

The number of gene therapy-based discovery programs in the biotech and pharma industry is significantly on the rise. It is a trend that is driving a greater need for the scalable production of gene therapy vectors. But most methods for the production of viral vectors are based on adherently growing cells and transient transfection, which is a tedious manual process.

Moreover, adherently growing cells only allow for scale-out and not for scale-up. This means when you want to increase the production volume, you need to increase the number of cell factories and personnel as the substrate-dependent growth of the cells is strictly limited by the available surface to grow on. The whole process is time-consuming, provides limited scalability, causes high costs of goods and is sometimes difficult in respect to reproducibility of the overall process.

To overcome these challenges that arise with scale-up, we have developed a suspension cell system: our proprietary CAP technology. The substrate independent growth makes the cells easier to handle and highly amenable to scale up. Our CAP-GT suspension cells grow to very high densities and are easily adaptable to all current bioreactor formats.

Cevec’s CAP-GT platform allows for the upscale production of gene therapy vectors

More importantly, these cells can produce very high titers of viral vectors, including AAV, lentivirus (LV) and adenovirus (AV). Also, the stable producer system, which is our latest addition to the platform, allows for the production of viral vectors without the need for transient transfection or helper viruses.

All of our CAP-GT cells were extensively safety tested according to the requirements of the European Medicines Agency (EMA) and the American Food and Drug Administration (FDA). Testing results, together with a complete documentation of the history of the development of the cell line, has been deposited as a biologics master file with the FDA, making the CAP-GT platform one of the best characterized cell systems available today.

How does your new Adeno-Associated Virus vectors stable production system facilitate gene therapy vector production?

Our CAP-GT technology for the stable production of AAVs is based on suspension cell lines. It eliminates the transient transfection step. Unlike other stable AAV production systems, it does not depend on the infection with helper viruses, such as adenovirus or herpes virus.

The production of AAVs using our viral packaging cells is straightforward and comparable to the established protein or antibody manufacturing process. And likewise it is fully scalable.

Cevec’s CAP-GT platform allows for the upscale production of gene therapy vectors in bioreactors because the cells grow in suspension and are independent of substrate attachment

In the first step of the process, the gene of interest is stably transfected into the viral packaging cells to generate the producer cell line. Subsequently, the most suitable producer cell clone is selected and characterized. Then, for production, the cells are expanded to the desired production volume and continuous viral vector production is chemically induced. This process allows for probably the most efficient and reproducible viral vector production available today.

What is the science behind the new AAV stable production system?

The genes for the production of all required components of the AAV vector, including the genes for the virus capsid proteins and the therapeutic gene to be included in the AAV vector, are stably integrated into the CAP-GT cells. To circumvent the cytotoxicity of some of these components, their expression must be placed under the control of an inducible system.

Transient lentiviral vector production in CAP-GT cells (Source: Cevec)

For a very long time, the induction of cell lines for AAV in particular was not possible, so we are very proud to be the first to have successfully found a solution. As a result, we are now building permanent packaging and producer cell lines, which can be easily expanded in bioreactors and induced to produce AAV vectors.

Why is a production system for AAV vectors so important? What are its major applications?

Recombinant AAV-based vectors are currently one of the most widely used vehicles for delivery in gene therapy indications. According to market experts, AAVs are used in nearly 50 per cent of the 483 currently ongoing gene therapy trials.

There are various reasons why this number is expected to increase over the next few years. Firstly, there is a lack of diseases associated with the wild-type virus. Also, AAVs have the ability to transduce non-dividing, as well as dividing cells. And a resulting long-term robust transgene expression is observed in several Phase I and II trials. Furthermore, different AAV vector serotypes can be used to specifically target different tissues, organs, and cells, thus expanding the therapeutic application and commercial potential of AAV-based gene therapies.

Stable production of viral vectors in CAP-GT (Source: Cevec)

There is definitely a growing need for fully scalable, clinical-grade good manufacturing practice (GMP) solutions for all new gene therapies based on AAV vectors designed for large patient groups that require high doses of the vectors, such as in hemophilia, muscular dystrophy, Parkinson’s and Rheumatoid Arthritis.

How do you see your CAP-GT manufacturing system developing in the future?

We will definitely be focusing on establishing our CAP-GT suspension platform as the industry standard for scalable viral vector production. While transient production will remain a main production platform for quite a while, I am confident that it will increasingly be replaced by more stable production systems, like ours.

Currently, we are developing a suite of cell lines for stable production of several AAV serotypes. These cell lines can then be used as standard production vehicles or as a base for a more customized approach.

Additionally, we are working on specific packaging cell lines for lentiviral vectors which represent the second major gene therapy vector type. Thanks to the ability of lentiviral vectors to integrate genetic information into the genome of non-dividing cells, they are widely used for the modification of immune cells, such as T cells in the CAR-T approach, which has resulted in the launch of two gene therapy products last year.

What are the different application areas for your CAP technology?

In addition to the activities I mentioned before, there are also attractive opportunities for our CAP-GT technology in other areas. Our cell lines are, for example, very well suited for the production of adenoviral vectors (AV) used as oncolytic viruses, vaccines based on antigen-presenting vectors, or virus-like particles (VLPs).

An especially promising proposition that has been loosely connected to gene therapy is the therapeutic use of exosomes. CEVEC is working with partners who are investigating in this field, and the first results with CAP-derived exosomes are really promising. It is unclear if exosomes will in fact be used in therapeutics, but there is a lot of potential in this field and we are excited to be able to contribute our expertise at the forefront of this research.

With its novel helper-virus-free stable production system for Adeno-Associated Virus vectors CEVEC provides a scalable manufacturing solution for the increasing demand in gene therapy vector supply. Get in touch for more information on the company and its innovative solutions!

Header image via Kateryna Kon/; all other images via CEVEC

Explore other topics: Cell therapyCevecGene therapy

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