Reducing Cell and Gene Therapy Development Time and Cost with New Purification Strategies

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The past 40 years have ushered in the most advanced medicines the world has ever seen, with tremendous improvements in biomanufacturing technologies to enable their development. Advances in production technology have brought significant improvements in upstream productivity, which then caused bottlenecks in downstream processing. Although many bottlenecks have been resolved for most biologics, new modalities such as gene therapies and mRNA vaccines are driving the need for differentiated purification solutions. Meanwhile, pressures to increase efficiency and reduce costs continue to mount for all biologics.

Innovative fit-for-purpose purification solutions are essential to the successful expansion of advanced therapeutic modalities beyond niche indications. Astrea Bioseparations is leveraging its expertise in development of customized separation solutions with unique nanofiber technology to bring game-changing purification solutions to market for both traditional and next-generation biologics. Additionally, the company can help customers reduce the time and cost of process chromatography by providing economical, ready-to-use columns packed with high-performance resins.

Combining a partnering approach with a focus on tailored solutions will contribute to advances in downstream processing for current and future biologics.

Upstream Advances Drive Downstream Innovation
Improvements in expression systems such as Chinese hamster ovary (CHO) and human embryonic kidney (HEK) cells and in growth media have increased upstream productivity dramatically for manufacturing engineered proteins and antibodies. With proteins reaching several grams per liter in culture today, productivity is far greater than was achievable for the first commercial biopharmaceuticals.

Expanding adoption of single-use (SU) systems eliminates costly and time-consuming cleaning and cleaning-validation procedures. And implementation of perfusion cell culture for continuous processing is boosting upstream productivity further.

Initially, the rapid increase in upstream titers outpaced available downstream purification technologies, especially for capture or affinity-based chromatography. Innovation in downstream bioprocess technologies improved performance substantially through application of membrane separation technologies, introduction of ready-to-use prepacked filters, development of continuous processing methodologies, and improvement of ligand and resin chemistries. For example, protein A binding capacities have increased from 20 mg/mL to ≤100 mg/mL.

New Modalities Create New Challenges
Further bioprocess improvements still need to be made, particularly considering the advent of complex next-generation therapies, such as multispecific and conjugated antibody products, oncolytic virus-based treatments, cell and gene (DNA and mRNA) therapies, and novel vaccines. Much process development work for these new modalities has focused on adapting methods and technologies originally designed for engineered protein and monoclonal antibody (MAb) products.

Chromatography resins optimized for MAbs are not as well suited to cells, viral vectors such as adenoassociated viruses (AAVs) and lentiviruses (LVs), plasmid DNA, mRNA, and exosomes. Conventional resins require oversized columns because the bead pores are difficult to access, so binding capacities are low. Diffusion is slow, resolution is low, and processing takes much longer than desired. Manufacturing footprints are consequentially larger as well.

Meanwhile, membrane adsorbers work well for simple flow-through applications in which capacity is less critical, but membranes have limited applicability for capture chromatography because of their limited surface area. Leveraging new materials designed for next-generation biologics is the only way to overcome the limitations of current downstream processes. Emerging technologies must be purpose-built for viral vector manufacturing and purification, for instance, to make gene therapies and viral vector vaccines more affordable.

A Nanofiber Purification Solution
As a member of the Gamma Biosciences portfolio, Astrea Bioseparations has added Nanopareil technology to the bioseparations toolbox. Nanopareil separation solutions are based on functionalized nanofibers that deliver dramatic improvements in performance over that of legacy chromatography technologies. Based on composite electrospun cellulose nanofibers with uniform and consistent composition and pore sizes, the matrix is physically or chemically functionalized for different separation modalities: e.g., ion-exchange (IEX), hydrophobic interaction (HIC), affinity, and steric exclusion.

Nanofiber membranes have a high surface area (>1,000 m2/g) and are >80% porous. No internal diffusion is required for adsorption, so the binding kinetics are rapid, requiring just one-second residence time to obtain saturation capacities. The average “effective” pore size is ~1.5 µm, and the open nature of the matrix allows for high flow rates at low pressures (<1 bar). In addition, porosity and pore sizes can be tailored for specific applications by controlling the layer stacking of nanofibers within a mat. With large pores, high ligand densities, and rapid flow rates, high-capacity separations are possible in a relatively small footprint, with significantly reduced processing times and costs. This technology is scalable from laboratory to clinical manufacturing.

Our initial work is focused on nanofiber separation solutions for IEX (weak and strong anion and cation) chromatography operations in bind–elute and flow-through modes. Proof-of-concept studies are in progress. For viruses, virus-like particles, AAV vectors, and plasmid DNA, we are reporting binding capacities >2.5× higher, cycle times >50× faster, and footprints ≤10× smaller than those possible with traditional resins.

Nanofiber separations should be applicable for all biologic drug modalities. In the Asia–Pacific region, where the cost of protein A for capture chromatography is a significant barrier, this new technology could offer an attractive alternative for dramatically reducing biomanufacturing costs. In fact, with their improved efficiency and productivity, nanofiber solutions from Astrea Bioseparations and Nanopareil could be game changers for the biopharmaceutical industry.

Partnerships Cut Development Time and Cost
Collaboration always has been a key focus for Astrea Bioseparations. Decades of close work has been carried out with academics, researchers, industry associations, other partners, and colleagues to accelerate the development of next-generation chromatographic tools.

Significant deals include licensing of the Affimer (stefin A) platform from Avacta Life Sciences for applications in bioprocessing. That has expanded Astrea’s range of ligand discovery and development capabilities to include high-performance, engineered, proteinaceous ligands as superior alternatives to antibody-based ligands. Combined with the mimetic Chemical Combinatorial Library (CCL) platform, the Affimer platform significantly expands our capacity to discover, develop, and deliver custom affinity adsorbents for purification of biotherapeutics and advanced therapies.

Prepacked plastic columns help to eliminate not only the packing step (which requires specialized skills and experience), but also cleaning and cleaning validation work. Such columns thus accelerate process development and production operations.

Enabling the Future
Novel modalities such as cell and gene therapies present great potential to mitigate and possibly cure diseases that previously were untreatable. Current bioprocess approaches, however, have led to unsustainable costs that are limiting access to (and thus the value of) these important new medicines. More rapid and cost-effective processes are needed to expand the scope of the cell and gene therapy field beyond niche products to treatments for widespread diseases.

Development of novel, fit-for-purpose biomanufacturing technologies and strategies such as the downstream purification solutions advanced by Astrea Bioseparations and its partners will be essential to overcoming the poor performance of existing processes. New nanofiber materials could reduce the time and cost of purification dramatically for viral vector, plasmid DNA, and other large biologic drug substances.

Daniella Steel, PhD, is senior product manager of cell and gene therapies
at Astrea Bioseparations, Horizon Park, Barton Road, Comberton, Cambridge, CB23 7AJ, UK; Affimer is a registered trademark of Avacta Life Sciences. CCL is a registered trademark of Astrea Bioseparations.

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