How to mitigate risks in viral vector production for gene therapies
At the Cell & Gene Therapy Manufacturing & Commercialization Asia Digital Week, Siddharth Gupta, Global Product Manager at Pall Corporation explored the risk mitigation attached to scale-up of viral vectors for gene therapy. Silvia Hnatova sums up the session.
Mr. Sid Gupta, Global Product Manager at Pall Corporation used his talk to cover the risks associated with gene therapies and how to mitigate them.
He first emphasized that the present is a ‘golden age' of gene and cell therapies, due to the number of products in clinical trials and M&As focused on gene and cell therapy companies.
There are 93 products in Phase III trials and 7 approved gene and cell therapy products.
Since 2017, there were more than 40B worth of M&As, acquisitions of smaller companies by larger companies. Mr. Gupta indicated that there should be many more gene therapies approved in the coming years.
The risks associated with manufacturing viral vectors were first presented, with Mr. Gupta explaining that the risks are associated with the process itself.
To assemble the virus, a eukaryotic cell needs to have instruction to assemble the virus, contained on a plasmid. Viral vector manufacturing is therefore significantly more complex than mAbs.
Around 20-30 genes are required to assemble the viruses, and the virus is toxic to the eukaryotic cells, limiting the titer.
Virus assembly by the cell is error-prone and requires significant experience and optimization.
To illustrate the risks of viral vector manufacturing, Mr. Gupta introduced 3 main methods to produce a virus using expression systems, their advantages and disadvantages.
The first option consists of triple transfection, which is a golden-standard method in the industry and can be used for scalable virus production.
This process is in adherent systems, is scalable, produces high-quality viruses, and can be brought to market in a timely manner. Disadvantages include high cost and inflexibility for cell line optimization.
The second method consists of insect cells and baculovirus in a suspension, giving it a huge advantage of scalability. Disadvantages include complexity and requirement for significant optimization.
The third method is using packaging/producer cell lines in a suspension, leading to high productivity. Technically, this process is challenging and has a long development time.
Mr. Gupta predicts that ultimately, suspension systems will become more popular as the market will ultimately move towards scalable systems.
He stressed that the main choice of the viral system depends on whether an adherent or suspension system is preferable.
After a thorough background into the technology, Mr. Gupta drew attention to case studies to illustrate how to best match viral vector manufacturing scale to gene and cell therapy demand.
The first example was an adherent HEK293 cell transfection process for scalable AAV production in the iCELLis(R) 500 fixed-bed bioreactors.
Palls’ customers struggled with scalability, which prompted the adherent virus production in iCELLis, Mr. Gupta explained.
Growth comparability of the Xpansion bioreactor versus flatware was compared, with little differences between cell stacks and XP10 and XP200 multiplate bioreactors on day 3.
Similar growth in both iCELLis Nano bioreactors was observed when using cells amplified by the simplified scalable seed train of Xpansion 200 bioreactor, as they were seeded by the manual seed train of planar vessels.
The most important parameter was the AAV9 yield and productivity, demonstrating that there was no significant difference between cell stacks and XP10 or XP200 expansions.
Because DNA/PEI pro complexes are shear sensitive, rapid transfer of the 60 L complexes into the production bioreactor needed to be performed.
Finally, when measuring specific productivity, it was demonstrated that parameters determined in the iCELLis Nano bioreactor were transferable and scaled linearly to the iCELLis 500 bioreactor.
To illustrate options for scalable manufacturing, Mr. Gupta introduced Allegro STR single-use bioreactor platforms, followed by a case study of the STR Bioreactor 500L for AAV production by HEK293.
HEK293 cells were cultured in a shake flask, followed by expansion in 50L and 500L bioreactors.
Mr. Gupta made an interesting observation about HEK293 cells in suspension that had better doubling time in STR50 bioreactor than in flatware, further speeding up the manufacturing process.
To summarize, Mr. Gupta compared the scalability of the AAV productivity by HEK293 in suspension using different STR bioreactor scales.
There was no significant difference in productivity between the STR 50 and 500 bioreactors, pointing to linear titer scalability – and the same parameters can be applied between STR 50 or 500 L bioreactors.
Mr. Gupta closed his talk by emphasizing the need for risk mitigation in scalable viral vector production for gene and cell therapies.
To mitigate risks, single-use consumables must be used, and raw materials filtered, automating processes as much as possible. This in turn reduces the number of manual steps, and enables use of closed aseptic systems.
