New building blocks, with the aim of improved therapeutics

Our novel DNA base pair creates an expanded genetic alphabet

The ‘genetic alphabet’ of DNA constitutes two base pairs (A–T and G–C). In an important discovery in synthetic biology, Synthorx’ scientific founder Dr. Romesberg and his team have crafted new base pairs, including d5SICSTP and dNaMTP (abbreviated X–Y), that can be replicated, maintained, transcribed, and subsequently translated in vivo. The expansion of the genetic alphabet with X and Y allows for the increased storage of information and the incorporation of novel amino acids into new, unique proteins.

Why it matters

Protein therapeutics have delivered tremendous value to patients, but some have limitations which cannot be corrected utilizing the twenty natural amino acids. Many proteins in the cell have dual and often opposing functions owing to interaction with different receptors. Synthorx deploys its novel building block technology to create proteins that are capable of re-programming receptor interactions to potentially treat disease. Furthermore, the half-life of the protein can also be modulated through site-specific bioconjugation such as incorporation of PEGs. We believe these improved pharmacological properties can make drugs that are more efficacious, safer, and more convenient for patients.

How we accomplish this

A semi-synthetic organism was created that incorporates all the necessary building blocks for scalable synthesis of Synthorin™ proteins

Our proprietary bacterial strain, based on a well-established E. coli protein manufacturing strain, expresses a nucleotide transporter (A) that allows controllable maintenance of X–Y genetic information. Supplementing cultures of this strain with X and Y nucleotides leads to their intracellular accumulation to support replication of the DNA encoding genes containing X–Y (B). Induction of transcription stimulates the cell to express the Synthorin messenger RNA harboring non-canonical codons, and the orthogonal tRNAs that decode them (C). Engineered tRNA synthetase enzymes recognize and specifically charge the Synthorx tRNAs with corresponding novel amino acids (nAA) added to the medium (D). Finally, the cell’s natural translation machinery uses these components to decode X–Y codons, site-specifically introducing nAAs into the desired Synthorin product (E).

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