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Touchlight Proprietary Synthetic Vector Tech Offers Enticing Alternative to Plasmid DNA


NEW YORK – UK biotech company Touchlight is using its proprietary in vitro DNA production platform to manufacture doggybone DNA (dbDNA), an enzymatically amplified DNA vector that the company said is a more scalable alternative to traditional plasmid DNA.

While the Hampton-based contract development and manufacturing organization (CDMO) is currently primarily focused on large-scale production of good manufacturing practice (GMP) dbDNA for genetic medicine partners, the company said its technology can also be useful for research applications and beyond.

Established in 2007, Touchlight invented the dbDNA technology to break the capacity and scalability bottlenecks imposed by the traditional plasmid DNA synthesis process using Escherichia coli fermentation.

"There is a significant capacity bottleneck in the industry," said Tommy Duncan, chief business officer at Touchlight. "But there are a lot of companies out there with a lot of demand for [plasmid] DNA."

Named after its schematic structure, dbDNA is a synthetic vector with a linear, double-stranded, and covalently closed construct.

According to Touchlight, the workflow of dbDNA production starts with DNA denaturation, where a circular template DNA containing the sequence of interest and bacterial backbone is chemically denatured. The materials then undergo rolling circle amplification using phi29 DNA polymerase, producing long, linear, and double-stranded concatemers. After that, protelomerase carries out a cleavage-joining reaction on the linear DNA at specified sites to produce dbDNA.

The product subsequently goes through multiple enzyme treatment and purification steps to eliminate the bacterial backbone DNA sequences as well as the impurities.

"What we see is that the dbDNA molecule itself is at least substitutable for plasmid DNA, which is its primary comparator in this space," Duncan said, adding that there are also numerous potential advantages of the dbDNA compared with conventional plasmid DNA.

For one, he said, dbDNA "does tend to have a better expression profile." Additionally, he said dbDNA can eliminate some of the bacterial backbone sequences in plasmid DNA such as antibiotic resistance genes and origins of replication that can be immunogenic, which could be a regulatory issue when used in genetic medicine.

"In DNA vaccines, we tend to see that dbDNA is at least as potent at a substantially lower dose versus plasmid DNA or even has a better immunological profile more generally," Duncan added.

In a study published last year in the journal Gene Therapy by Touchlight scientists and their collaborators, the company showed that dbDNA can be optimized to produce high-titer lentiviral vectors (LVV).

In addition to being able to produce sequences that are difficult to amplify in bacteria, dbDNA "offers benefits from both a regulatory and a manufacturing standpoint due to the elimination of bacterial propagation sequences, the significantly shorter lead times for multi-gram scale GMP material, and a reduced requirement for input material," the authors concluded.

According to Duncan, the manufacturing process for dbDNA is simpler and more flexible compared with that of plasmid DNA, which is typically achieved by E. coli fermentation.

"Plasmid [DNA] requires quite a lot of fixed equipment, quite a large volume of upstream fermentation capacity, and can be quite lengthy," he said. "The dbDNA manufacturing process is extremely simple from the perspective of capital equipment, the time it takes, and the simplicity of the facilities that you need in order to make a very large quantity of DNA material in a short space of time."

Duncan said a typical workflow from the starting DNA template to producing multiple grams of GMP dbDNA is about five days, followed by between one and two weeks of quality control, depending on the QC specification.

Duncan did not disclose a specific list price for the company's product, but he noted that the cost structure of making dbDNA is "very different" compared to plasmid DNA. "We don't have an expensive set of equipment that we need," he said. "The largest cost contributor to dbDNA production is materials."

Because of dbDNA's unique capability to scale, Duncan said, Touchlight, as a CDMO, has been focusing on manufacturing large quantities of GMP clinical materials for clients as its business model. However, he said the company "do[es] absolutely operate within the research space," even though it currently does not offer a product catered for the basic and translational research market.

The company, which has secured more than 100 patents globally pertinent to dbDNA technology, has also been licensing the technology to third parties to allow them to carry out the dbDNA manufacturing in house, Duncan said, noting that this will also be a key part of the company's business model going forward.

Beyond genetic medicine, Duncan also believes that the dbDNA technology can be easily scaled down and "utilized in any space where plasmid DNA is being used," including small-scale genome editing experiments and transient transfections to make antibodies.

"There are always new use cases for the dbDNA that we continue to investigate and continue to scale, as well," he said.