Plasmids release specifications are critical to provide effective control of this material when it is used in the manufacture of cell and gene therapy (CGT) products. Yet while some specifications exist, guidance defining expectations for control and release of plasmids as a starting material for the manufacture of viral vectors (e.g., AAV and LVV) for the delivery of CGTs is limited. Industry needs a common language and the ability to reference a shared platform of test attributes and release requirements for plasmids to increase the confidence, speed, and efficacy of data gathering. The platform should also help shape future guidelines and regulations issued by agencies such as the US Pharmacopeia.
This is why BioPhorum has published three documents to date.
The first is Raw materials: Cell and gene therapy critical starting material: a discussion to help establish release specifications for plasmids and the bacterial master cell banks used to produce them, which proposes a platform framework for testing plasmid master cell banks and plasmid DNA to manufacture AAV or LVV viral vectors for the delivery of CGTs. It also includes a survey inviting reader feedback on the approach.
The second is Raw Materials: Perspectives on raw and starting materials risk assessment for cell and gene therapy (CGT) processes, which shares some of the unique challenges of raw materials for CGT manufacturers when working with suppliers.
The latest document is a Discussion on plasmids to establish release specifications using a risk-based approach to manage supply that supplements the previous two papers. It aims to complement broader industry efforts to advance release testing of plasmid DNA and the bacterial master cell banks used to produce them – and de-risk their supply.
We talked to some subject matter experts about how they have used the platform framework and how this focus on raw materials has benefited them.
What problem was the plasmids team trying to address?
“Initially, we were level-setting our expectations for plasmid specifications” said Aaron Mack, Senior Engineer – Material Science Group at Biogen. “At the time, most people were using a commonly available GMP plasmid, but when thinking about democratizing what we needed in terms of dual sourcing, etc., having those agreed expectations was a great efficiency gain for industry. Then we established a risk assessment approach that could be applied to these unique materials for gene therapy, as opposed to what we’d set up for drug substance.”
His colleague Dan Blake, Scientist at Biogen, explained that at the start, there was lots of discussion about how to treat a CGT plasmid, whether as a mammalian cell bank or a raw material like sodium. “With the testing, this BioPhorum work clarified that it’s something unique.”
Lili Belcastro, Principal Scientist – Development Material Sciences & Engineering at Bristol Myers Squibb, had similar thoughts. She said, “The paper helped to address the discrepancy in guidance about whether plasmids used in CGT upstream manufacturing are a raw/ancillary material, starting material, or drug substance.”
How did you apply the BioPhorum recommendations to your situation?
“Through the survey, we were able to confirm an industry consensus on reduced sampling for sterility testing since plasmids are a starting material, which allows us to follow the guidelines in ICH Q5B: Analysis of the expression construct in cell lines used for production of rDNA-derived protein products,” Belcastro added.
As well as standardization and level setting, Mack suggested the BioPhorum work increased efficiency and reduced the amount of ‘back and forth’ between companies. “So, rather than us all having to audit and have individual meetings with 50-60 plasmid companies, we have a document that sets out industry expectations.”
Why was it important to address these problems?
Mack said that by setting appropriate expectations, the team wanted to ensure they were not going above and beyond what was needed — for example, using specifications for plasmids that are inappropriate for the process.
“When we started looking at this, existing guidelines were for direct injection of a plasmid,” Mack added, “as opposed to setting up or making an AAV or other type of recombinant DNA therapy where you take cells out of the body, add plasmid to them, do some transfection and put them back into the body. We added an extra level of nuance and expectation over direct injection.”
How has the BioPhorum work benefitted your company and industry?
Greg Stromberg, Head of Site Manufacturing Science, Gene Therapy Manufacturing at Biogen, said there are benefits but it was also important not to swing the pendulum too far either way. “We wanted to ensure that we provided a safe and characterized molecule or AAV to our patients, but we also needed to ensure that we didn’t set the bar too high and are aligned with our peers. The paper also helps industry explain our views in the same way, to help agencies best understand our materials as they come into our process.”
What lessons did you learn from going through this process?
Belcastro said that in her experience companies handle plasmids differently in terms of qualification and characterization. “Being able to align with other industry leaders on this platform approach may ultimately lead to a reduced cost of goods by not having to repeat all the testing every time a new lot is made.”
Stromberg added that Biogen was trying to provide a plasmid or starting material source that matches his company’s requirements. “The better we define our release criteria and the risk assessment criteria of a supplier, the better we can select a supply chain that meets our needs and that is reasonable for cost, timelines, internal/external sourcing strategies, etc.”
What was the benefit of doing this work as a collaboration?
“Biogen is involved in many different phorums and workstreams, so we see many parallels with what we’re trying to do in the different modalities, specifically gene therapy,” added Stromberg. “We’re pulling in some of that expertise from those other phorums, so I think gene therapy has started faster than some other phorums because of that experience. That’s what BioPhorum allows us to do by working with our peers.”