A platform approach to bioprocessing uses the same set of protocols and systems found during early phase development. Scientists then transfer the protocols, by either scaling-up or scaling-out, through to cGMP production.

Zoltán Kis, PhD, senior lecturer and associate professor in the department of chemical and biological engineering at the University of Sheffield, opened the recent ESACT-UK conference by extolling the virtues of developing a platform process for mRNA manufacturing.

“By developing a platform process for mRNA, you can quickly produce therapeutics and vaccines in a disease agnostic manner. For example, by using a well-defined enzymatic cell-free process, once you have the template DNA, you can produce mRNA in the upstream process with the right critical quality attributes (CQAs) in just two hours,” said Kis.

He detailed an upstream optimization study on the initial in vitro transcription (IVT) reaction used to make mRNA from DNA starting material. In the study, a design of experiments was performed using different reaction conditions including reaction time, nucleoside triphosphate building blocks, magnesium, T7 polymerase, spermidine, and DNA template concentrations. The results seen using capillary gel electrophoresis and anion exchange HPLC showed that an optimum set of conditions produced an mRNA yield of 14mg/mL which, according to Kis, is more than double the industry standard of 5–7mg/mL.

Web-based application

In addition, Kis highlighted a web-based application dashboard being developed in his research project and detailed how this could be used to read data from the IVT reactors to control the IVT reaction.

Image of the data analysis and visualization dashboard showing data from a continuous 90-minute in vitro transcription (IVT) reactor run, continuous chromatography run to purify the mRNA from the reactor, real-time PCA analysis scatter plot with t[2]=f(t[1]) and UV reading control chart for the IVT reactor. The image of the dashboard was generated by Kesler Isoko on the process run by Kate Loveday and Mark Jixin Qu. [Department of Chemical and Biological Engineering/ University of Sheffield].
“Using our dashboard, we can monitor and record critical process parameters such as pH, nucleoside triphosphate, and magnesium concentration and feed these into the digital twin which is embedded into the dashboard to make mRNA yield predictions. If the digital twin predicts the yield is going to fall outside specification (for example within the next 5–10 minutes), then we can control process parameters in the reactor automatically via the dashboard and keep CQAs within specification,” Kis explained.

Kis also presented a second downstream optimization study using a continuous four oligo-dT column chromatography method.

“Our continuous method is scalable, and it has analytics built in to allow feedback control. Using this method, we can purify mRNA much faster to produce around three times more product per unit time and unit scale compared to a traditional batch method. The processed mRNA has high purity and more than 90% integrity,” Kis noted.

“The need for developing platform processes that can be quickly adapted for different therapeutics and vaccines was highlighted by the COVID-19 pandemic. With our work, we have created intensified and continuous processes for mRNA production. We have also shown that our new dashboard can be used to monitor and control the process in real-time aiming to keep all 20 plus CQAs automatically within specification.”

Scaleup of adenovirus-vectored vaccines

Alexander (Sandy) Douglas, PhD, associate professor at the Jenner Institute at Oxford and winner of the Chris Hewitt Rising Star award at ESACT-UK 2024, presented an impressive case study on the benefits of developing a platform process for taking an adenovirus-based COVID-19 vaccine production from laboratory scale to over a billion doses.

“In 2019, my team and I, at the Jenner Institute in Oxford, had plenty of pre-clinical experience with adenovirus-based vaccines as we had used it to develop a rabies vaccine. But we had no experience of large-scale manufacture, because at the Jenner, we produce vaccines in small quantities for clinical trials and then partner with manufacturers such as the Serum Institute of India for scaling,” commented Douglas, who added that the Jenner Institute usually produces no more than 2,000 doses at a less than 20 L scale.

“In February 2020, my group (three scientists at the time) were tasked with developing an adenovirus-based COVID-19 vaccine that could be manufactured at scale for pandemic use. We had recently developed a small-scale platform process that could use single-use bioreactors and purification methods,” Douglas continued.

His group used HEK-293 cells and, by optimizing media and feeds in 30 mL shake flask models, they increased their yields by up to 10-fold. They then transferred this process to 50 L and then 200 L stirred tank bioreactors to make initial batches before partnering with AstraZeneca.

“When we were scaling up, I had an Excel spreadsheet, which showed me how much bioreactor capacity and the amounts of reagents we would need to get to 1 billion doses based on our yields. This was when I realized we would need tens of thousands of liters of bioreactor capacity,” Douglas elaborated.

In partnership with AstraZeneca and with support from contract manufacturing and development organizations, Cobra, Halix, and Oxford Biomedica, his group then developed a platform process to make it more efficient and easier to scale.

“By transferring a platform process to manufacturers, including the Serum Institute of India and WuXi in China, we produced more than 2.5 billion doses in 2021 and it wasn’t just fill-finish, we had drug substance being made using our process in 12 countries across five continents,” pointed out Douglas.

“In the future we believe it will be possible to produce 1 billion doses in 130 days from the emergence of a new pathogen using higher productivity intensified culture as a key enabler. We are also working at the other end of the range of scales. At around £1 million ($1.26 million), GMP manufacturing costs are the biggest line item for getting vaccines into first-in-human trials. This is why we are now working on other low-cost platform processes to help us produce better, low-cost vaccines for a range of diseases, potentially making them more accessible globally,” emphasized Douglas.

Production of cost-efficient allogeneic cell therapies

At ESACT-UK, an interesting platform approach to produce cell therapies was presented by Márcia Mata, PhD, associate lead scientist of technology and process innovation at the Cell and Gene Therapy Catapult.

“Allogeneic cell therapies offer many benefits compared to autologous cell therapies as they can be produced in batch, resulting in more consistent quality control and lowering costs by applying economies of scale. When considering indications targeting a large number of patients, with doses of ≥109 cells per patient, allogeneic induced pluripotent stem cell (iPSC) derived therapies have been considered as a solution for off-the-shelf affordable therapeutics, as these cells have the potential to differentiate into any cell type,” said Mata.

Traditional manual 2D iPSC culture is not amenable for large scale production of clinically relevant cell numbers, as they are typically labor-intensive, open, and poorly scalable technologies with limited in-process monitoring and increased risk of batch failure. A 3D iPSC expansion platform using scalable, closed, and automated bioreactor technologies can contribute significantly toward the cGMP manufacturing of cell material that can be further utilized in multiple differentiation processes for high dose requirement indications. In addition, these systems allow for the integration of process analytical technologies, which can facilitate greater control through increased process understanding, monitoring, and feedback control.

3D rendering of induced pluripotent stem cell (iPSC). [Marcin Klapczynski/Getty Images]

Mata described how the Cell and Gene Therapy Catapult is developing a closed, automated perfusion process using scalable stirred tank bioreactors (STRs) and a Biosep acoustic filter cell retention system. According to Mata, this platform can be used to expand iPSC cells up to 20-fold every four days and can control aggregate size to <300 µm.

“For the differentiation into the iNK [induced natural killer] case study, we aimed to translate a static, manual, and open natural killer (NK) cell differentiation process from well plates into a scalable STR platform,” Mata commented.

Mata presented data comparing two runs of the bioreactor expansion to iNK differentiation process with a traditional static flask approach. This data showed that the scalable bioreactor process was able to produce a pure population of CD45+/CD56+ NK cells (>80%) with an increased yield per starting iPSC compared to the current manual process, thereby reducing the material cost of manufacturing. In addition, the iNK cells produced in an STR were shown to be functional as they demonstrated in vitro cytotoxicity toward three cancer cell lines.

“As an exemplar manufacturing scenario, to produce a clinically relevant number of doses of NK cells, the traditional method would require 80 CellSTACK-10 cell culture vessels versus a single 85 L STR, which is significant progress toward the commercialization of such therapies by decreasing the footprint, labor and overall cost,” Mata concluded.

Future perspective

Speakers and delegates at ESACT-UK agreed that using standardizing platforms for manufacturing of advanced therapies and vaccines are the way forward, as they offer less complexity, better scalability, as well as scope for tighter process monitoring and control.

In the case study of the adenovirus-based COVID-19 vaccine, for example, developing a platform process allowed smooth process transfer around the world, reducing the risk of process failures. This ensured that the vaccine could be produced safely at scale for rapid distribution.

Using a platform approach with iPSCs has yet to be proven as the best method for production of allogenic stem cells treatments. However, it could result in benefits including reducing costs associated with manual production by highly skilled scientists. It could also reduce the manufacturing risk and costs associated with batch failure due to using open, poorly controlled cell culture methods.

“With our iNK platform method, an issue we have with producing cGMP iPSC cell lines, is gaining access to clinical grade iPSCs for the seed train without paying a fortune in licensing fees,” according to Mata. “We also still need to implement process analytical technology tools and optimize our process, but we’re working on those areas and are optimistic for the future.”

Sue Pearson, PhD, is a free-lance writer based in the U.K.

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