Synthorx Announces Completion of Series B Financing

Synthorx Inc. has announced the completion of a $10 million Series B financing, led by RA Capital Management and joined by Series A investors Avalon Ventures and Correlation Ventures. In conjunction with the financing, Andrew Levin, M.D., Ph.D., managing director of RA Capital Management, will join Synthorx’s board of directors. Leveraging a synthetic biology breakthrough, Synthorx has developed scalable platforms for producing proteins that cannot be made through traditional methods.

The proceeds will finance the development and scale-up of novel protein therapeutics that incorporate at least one synthetic amino acid. “The ability to incorporate synthetic or non-natural amino acids into proteins is not new,” said Dr. Levin. “What we believe is new and truly groundbreaking about Synthorx’s technology is the ability to efficiently produce a variety of proteins containing multiple synthetic amino acids at the necessary scale and cost of goods for drug discovery and development.”

Dr. Levin continued, “With a small team and a small initial investment, Synthorx has made notable progress from the Nature paper and helped answer many of the questions about the technology to enable a focus on product development.” Synthorx’s technology is based on research published in Nature that described the first single-cell organism capable of replicating and maintaining a novel synthetic DNA base pair, named d5SICSTP and dNaMTP (abbreviated X and Y). DNA from every known species uses its four bases – A, T, G and C – to assemble the 20 natural amino acids into proteins that carry out the functions of life.

With X and Y, Synthorx’s expanded genetic alphabet technology is designed to produce proteins with multiple, different synthetic amino acids in a scalable and cost-efficient manner. “There are many peptide and protein therapeutic programs in biotech and pharmaceutical companies that stall because they can’t be scaled in a manner amenable to drug development and commercialization,” said Court R. Turner, president and CEO of Synthorx. “The breakthrough of having a living cell replicate and maintain a third base pair is not just about creating something new. It’s about being able to make better protein therapeutics at the right scale and for the right cost, so patients can access these improved medicines.”

Recombinant protein therapeutics have had a dramatic impact on medicine and the treatment of numerous diseases, such as insulin for diabetes and monoclonal antibodies for cancer immunotherapy. While these advances have improved lives and changed how new therapeutics are developed, many protein therapeutics have biophysical and pharmacological limitations. In order to overcome these limitations, therapeutic proteins are frequently chemically modified to enhance their pharmacological properties.

“Synthetic amino acids have a wide diversity of characteristics that can be leveraged to improve delivery, potency, efficacy, selectivity, and efficiency of protein therapeutics. They can also be leveraged to precisely modify the protein and deliver a homogeneous product,” explained Mr. Turner. “By genetically encoding for the site-specific incorporation of select synthetic amino acids, we can create entirely novel proteins with greatly enhanced properties and enable a new generation of tailored protein therapeutics.”