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Synthorx Raises $10M to Expand Use of Synthetic DNA in Biologics

Xconomy San Diego — 

Synthorx, the San Diego synthetic biology startup that expanded the number of DNA base pairs with two synthetic nucleotides, said today it has raised $10 million in a Series B financing round led by RA Capital Management, the Boston life sciences hedge fund.

Existing investors Avalon Ventures and Correlation Ventures joined in the round. The San Diego firms have invested $6 million since 2014, when Synthorx was founded, CEO Court Turner said yesterday. An unnamed pharmaceutical company also is providing additional undisclosed funding under a drug development deal signed in February, Turner said.

The new funding represents a shift from proof-of-concept to demonstrating how a promising research breakthrough in synthetic biology can be used to produce new biologic drugs at commercial scale, Turner said. The company plans to use the proceeds to double its headcount (from eight to 16), and to finance the development of new protein-based drugs that incorporate at least one synthetic amino acid.

In its quest to develop new biologics, Synthorx has focused on potential products for treating pain, metabolic disease, and infectious diseases, Turner said.

The company’s technology is based on research led by Floyd Romesberg, a biological chemist at The Scripps Research Institute. In addition to the four standard nucleotides that comprise DNA (designated as A, C, T, and G), Romesberg’s team showed that a novel synthetic DNA base pair (X and Y) could be inserted into bacterial DNA that reproduced with no change in the altered DNA.

The initial goal at Synthorx, Turner said, was to use the techniques developed in Romesberg’s lab to insert synthetic DNA into E. coli bacteria and to make proteins that incorporate synthetic amino acids.

Recombinant protein therapeutics already have had a dramatic impact in medicine, and examples abound, such as insulin for diabetes and monoclonal antibodies in cancer immunotherapy. But many protein therapeutics have limitations that stall their advance. For example, certain proteins are only effective if they fold in a particular way.

The ability to incorporate synthetic amino acids into proteins also is not new, and many protein  therapeutics with synthetic amino acids have been developed, Turner said. “But a lot of them don’t advance because [production] can’t be scaled up commercially. They can’t be made efficiently and at low cost.”

The groundbreaking potential of Synthorx’s technology is the ability to insert synthetic DNA in bacteria and efficiently produce proteins with multiple synthetic amino acids at low cost and at sufficient scale for drug discovery and development. “We are the only company where you can add synthetic amino acids to any size protein or peptide and produce it at scale,” Turner said.

The funding round led by RA Capital also comes with needed expertise in identifying high-value products for development, Turner said. Andrew Levin, a managing director of RA Capital, is joining Synthorx’s board of directors as part of the financing.

Synthorx also has been meeting with pharmaceutical companies that have developed protein therapeutics that stalled, and could possibly be optimized using Synthorx’s technology.

As part of its hiring plans, Synthorx will add a chief science officer as well as a chief business officer in coming months, Turner said.