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Synthorx’s synthetic DNA base pair expands the DNA alphabet to enable the creation of more diverse proteins for wide variety of applications in medicine and technology

SAN DIEGO, August 19, 2015 — Synthorx Inc. announced today that the company has employed its proprietary protein expression system to successfully produce proteins containing novel amino acids. Using a semi-synthetic DNA template (containing the synthetic base pair X and Y), Synthorx scientists were able to produce RNA containing X and Y, which was used with an otherwise fully natural biological system, to efficiently direct the incorporation of multiple novel amino acids at different sites in proteins.

“Synthorx has built a world class research team that has achieved a scientific milestone in record time,” said Court Turner, president and co-founder of Synthorx. “By advancing our technology to this stage, we are now poised to produce proteins containing multiple novel amino acids, to fill our drug discovery pipeline as well as enable our partners in many aspects of drug development and manufacturing.”

The work builds on research published in Nature last year that described the first in vivo replication of DNA containing a synthetic base pair, named d5SICSTP and dNaMTP (abbreviated X and Y). The incorporation of X and Y into DNA expands the genetic alphabet and promises to allow for site-specific incorporation of multiple, different novel amino acids into a single protein. Since the publication, Synthorx has developed and validated a protein expression system, employing its synthetic DNA technology to incorporate novel amino acids to create new full-length and functional proteins.

“The Synthorx system uses a fully natural cellular system and allows for site-specific insertion of multiple novel amino acids to create more diverse proteins with a range of properties,” added Mr. Turner. “We have now shown that our synthetic base pair, X and Y, can not only be replicated in vivo but are also compatible with the natural biological machinery to enable novel protein expression.”

DNA from every known species has the ability to code for or “spell” proteins that are assembled from 20 natural amino acids, based on arrangements of its four chemical bases or letters – A, T, G and C. But the DNA that Synthorx makes containing its synthetic bases, X and Y, has the potential to spell with an additional 152 novel amino acids, which could be combined to make proteins with unique properties.

“Hundreds of novel amino acids have been produced in the lab, but incorporating them into a protein in a useful and scalable manner requires an expanded genetic code,” explained Mr. Turner. “With our synthetic base pair, we can add multiple different, novel amino acids at any location into a single protein. Now we can create more diverse proteins for improved drugs, diagnostics, and vaccines.”

In the current work, Synthorx scientists site-specifically added novel amino acids into a regular protein. To do this, they customized the DNA that encoded for the protein by adding the synthetic base pair at specific locations. Using the Synthorx expression system, the DNA was then transcribed into messenger RNA, which was then translated into a protein of several hundred regular amino acids and one or more novel amino acids. The accurate incorporation of the novel amino acids at the intended locations was confirmed with mass spectrometry.

“When I began working on synthetic bases more than 15 years ago, the end goal was always to be able to incorporate novel amino acids into proteins in a robust manner,” said Floyd Romesberg, Ph.D., Synthorx’s co-founder and professor at The Scripps Research Institute. “With the ability to generate novel and diverse proteins, we have a significant opportunity to make a revolutionary leap forward in improving health by creating new medical and technological applications.”

About Synthorx

Synthorx is a biotechnology company using synthetic biology to synthesize solutions for the discovery and development of novel therapeutics, diagnostics, and vaccines. With the revolutionary advancement of synthetic nucleotides that can be maintained and replicated by a single-cell organism, Synthorx is exploring the natural and evolution-directed technologies to improve drug discovery. Using synthetic nucleotides to expand the genetic alphabet, Synthorx is developing novel proteins, RNA and DNA for medical applications. Synthorx’s investors include Avalon Ventures and Correlation Ventures. The company was founded based on important discoveries in Dr. Floyd Romesberg’s lab at The Scripps Research Institute in La Jolla, CA.