Continuous Investment

Cobra Biologics, Pall, and the UK’s Cell and Gene Therapy Catapult have won a shared grant of £1.5 million from the UK’s innovation agency, Innovate UK, to investigate the feasibility of continuous manufacture of adeno-associated viruses (AAV) for gene therapy applications. Tony Hitchcock, Technical Director of Cobra Biologics, tells us more.

Could you tell us about the focus on AAV?

AAV is currently the main vector used to treat monogenetic diseases. The approach has shown spectacular results in the treatment of a broad range of conditions ranging from ophthalmic conditions through to whole body diseases, such as hemophilia and spinal muscular atrophy (SMA). We have seen the licensing of Luxturna for the treatment of retinal disease caused by the RPE 65 gene and it is anticipated that a number of other products, currently in phase III studies, will be successfully licensed in the coming months.

What are the main drawbacks with current methods for manufacturing AAV?

As with a number of other viral vectors, the production processes currently being used are essentially scaled up lab processes, using a number of steps that are poorly scalable and often inadequately defined, such as the use of adherent cell culture systems and ultracentrifugation for the separation of empty and full capsids. Going forward, the industry needs processes that are more suited to the anticipated amounts of material needed to address key disease areas, such as hemophilia, and to reduce the cost of manufacturing.

What are the expectations of the collaboration?

A specific requirement was for projects that could achieve greater than 25 percent improvements in process yields for vector manufacturing. To achieve this, we will be looking at all aspects of the downstream process, including vector recovery and high-resolution chromatographic purification steps.

This collaborative project is split into agreed interconnecting work packages, with each party bringing their own specialist knowledge and experience in vector production and analysis, working towards improving process yields throughout the AAV recovery and purification process. The work will not only be based on the adaption of processes to continuous manufacturing, where Pall are world leaders, but also through improved in-process analytics, which will be developed through expertise from the Cell and Gene Therapy Catapult.

What are the main hurdles?

The development of a continuous process is essentially a two-stage process. Firstly, we must transition from batch to continuous mode for the individual process steps. Secondly, we connect those operations. Our project will focus on the development of the individual downstream operations initially in batch modes, which will then be transferred to a continuous operation. The key hurdles will be to create well-defined separation steps and critical operational parameters relating to these separation steps, and then to establish the required in-process monitoring and process control strategies required to transfer to continuous operations. Here, development of the necessary in-process analytical tools will be crucial.

The real gap is that we are working with technologies that have been developed for the production of protein therapeutics (more specifically monoclonal antibodies), which are produced in suspension culture at multi-gram levels. Viral vectors are produced predominantly in adherent culture systems at levels 5 to 7 logs lower titers and are physically up to 1000 times larger, generating micro/milligrams of product per batch. Therefore, we need to develop manufacturing technologies designed from a processing and monitoring perspective for these properties and product concentrations. Such considerations apply to both the upstream cell culture systems and the downstream recovery and purification platforms. For example, we need membrane technologies designed to recover and retain functionality of these particles rather than removal, and purification approaches that can achieve resolution between intact and partial vectors.

How does the project fit into the bigger picture?

There are a number of significant changes occurring in pharma – much of which relates to the need to reduce costs and improve access to new medicines, while trying to use new technologies and therapeutic approaches to address unmet medical needs and improve patient outcomes. In terms of new therapies, it is very clear that increasingly stratified approaches are being taken and this trend will continue, particularly as we see greater use of gene sequencing combined with AI (to target specific patient populations). Changes to clinical development strategies, in terms of the structure and nature of clinical trials, will also be required to reduce the cost and timelines for these studies.

From a manufacturing perspective, all of these factors point to the need for much more flexible approaches and platforms, to the supply of materials for clinical studies, and the ability to rapidly transition from clinical to commercial production. Significant changes in analytical and quality systems, as well as manufacturing systems, will be required to achieve this goal. Going back to the grant, the industry will need more innovative approaches, including continuous manufacturing, if we are to address these big challenges going forward.