By Gail Dutton

Applying technologies currently used to produce other biotherapeutics to cell and gene therapy production could dramatically improve product yields and purity in recombinant adeno-associated virus (rAAV) manufacturing, according to researchers at the University of Massachusetts Lowell (UML).

“No matter which platforms are used, rAAV productivity is relatively low compared to the clinical demands,” Seongkyu Yoon, PhD, co-director, Massachusetts Biomanufacturing Center, and faculty member at UML, and colleagues (doctoral candidate Qiang Fu; Ashli Polanco, PhD; and Yong Suk Lee, PhD), wrote in a recent paper. As a case in point, one manufacturing scale batch of 2,000–5,000 L can only support 20–50 patients. That, combined with expensive manufacturing processes, contributes to inordinately high prices for gene therapies.

Combine existing approaches

To counter that, the researchers suggested combining several approaches that are already used in biologics manufacturing and applying them to rAAV manufacturing. These include:

  • Multiomics to enable a systemic approach that better identifies changes in host cells’ physiology and thereby elicit better control over the cell line or bioprocess.
  • In silico modeling, which can improve productivity beyond that of traditional bioprocess treatments (such as temperature shift and sodium butyrate addition).
  • Synthetic biology/inducible producer cell lines to reduce the cytotoxicity inherent in continuous expression of viral components and to extend production, thus enhancing productivity.
  • Scale-free continuous manufacturing, which supports high cell density and consistently removes waste and harmful byproducts as well as any products with unstable structures. This approach, they write, “could reduce the cost and size of necessary equipment and lab space.”
  • Advanced purification methods to improve capsid recovery and quality. For example, the authors note, “Continuous chromatography, which has been extensively used in the monoclonal antibody field, could be an alternative solution.” Multi-column counter-current solvent gradient purification, is another option, “and overcomes the trade-off between yield and purity.”

Combining these tools can improve rAAV productivity in host cell lines, reduce impurities, and enhance scalability. “With a stable producer cell line developed and combined with continuous cell culture, higher cell density and continuous harvest can be achieved. Improved biosynthesis and packaging efficiency of fully packaged capsids, along with a continuous downstream process, would decrease the product impurities and increase the total number of full capsids in the final rAAV product,” Yoon tells GEN. “In total, we estimate the productivity to be increased by 50- to 100-fold.

“Each proposed technology exhibits critical challenges that need to be addressed, then transferred to the manufacturing lines and further optimized…as one complete platform,” he continues. “For example, multi-omics and its application in manufacturing requires deeper understanding and more comprehensive analysis. The development of an in silico model and stable producer cell lines also need to be further investigated and matured.”

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