THOR Synthorx Inc

Synthorx, Inc. (NASDAQ: THOR), a clinical-stage biotechnology company developing optimized therapeutics for cancer and autoimmune disorders, today announced that preclinical data highlighting THOR-809 will be presented at the American College of Rheumatology (ACR) Annual Meeting taking place in Atlanta from November 8-13, 2019.

Marcos E. Milla, Ph.D., chief scientific officer of Synthorx, will present research supporting the development of THOR-809, the company’s lead Synthorin™ for the treatment of autoimmune disorders.  THOR-809 is a site-specific, covalently-pegylated interleukin-2 (IL-2) variant that was discovered using Synthorx’ first-of-its-kind Expanded Genetic Alphabet platform.  Preclinical models showed that the compound selectively expands regulatory T cells, without activating and expanding effector T or natural killer cells.

Details of the poster presentation are as follows. For the full abstract, visit the ACR website.

THOR-809: An IL-2 Engineered from an Expanded Genetic Alphabet for the Potential Treatment of Autoimmune DisordersAbstract Number: 86 Presenter: Marcos E. Milla, Ph.D., Chief Scientific Officer, SynthorxSession Title: T Cell Biology & Targets in Autoimmune & Inflammatory DiseaseSession Date & Time: Sunday, November 10, 2019, 9:00 a.m. – 11:00 a.m. ET

Posters and related materials will be archived in the Scientific Publications section of the company’s website.

About SynthorxSynthorx, Inc. is a clinical-stage biotechnology company focused on prolonging and improving the lives of people with cancer and autoimmune disorders. Synthorx’ proprietary, first-of-its-kind Expanded Genetic Alphabet platform technology expands the genetic code by adding a new DNA base pair and is designed to create optimized biologics, referred to as Synthorins. A Synthorin is a protein optimized through incorporation of novel amino acids encoded by the new DNA base pair that enables site-specific modifications, which enhance the pharmacological properties of these therapeutics. The company’s lead immuno-oncology (IO) product candidate, THOR-707, a variant of IL-2, is in development in multiple tumor types as a single agent and in combination with an immune checkpoint inhibitor. The company was founded based on important discoveries by Dr. Floyd Romesberg and The Scripps Research Institute. Synthorx is headquartered in La Jolla, Calif. For more information, visit www.synthorx.com.

Forward-Looking Statements This press release contains forward-looking statements about Synthorx as that term is defined in Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Statements in this press release that are not purely historical are forward-looking statements. Such forward-looking statements include, among other things, preclinical data or plans underlying THOR-809 and the development of Synthorx’ product candidates. Actual results could differ from those projected in any forward-looking statements due to numerous factors. Such factors include, among others, risks associated with the process of discovering, developing and commercializing drugs that are safe and effective for use as human therapeutics and operating as a development stage company; Synthorx’ ability to develop, initiate or complete preclinical studies and clinical trials for, obtain approvals for and commercialize any of its product candidates; changes in Synthorx’ plans to develop and commercialize its product candidates; the potential for any future clinical trials of THOR-809 or other product candidates to differ from preliminary or expected results; Synthorx’ ability to raise any additional funding it will need to continue to pursue its business and product development plans; regulatory developments in the United States and foreign countries; Synthorx’ reliance on key third parties, including contract manufacturers and contract research organizations; Synthorx’ ability to obtain and maintain intellectual property protection for its product candidates; the loss of key scientific or management personnel; competition in the industry in which Synthorx operates; and market conditions. These forward-looking statements are made as of the date of this press release, and Synthorx assumes no obligation to update the forward-looking statements, or to update the reasons why actual results could differ from those projected in the forward-looking statements. Investors should consult all of the information set forth herein and should also refer to the risk factor disclosure set forth in the documents the company files with the SEC available at www.sec.gov.

Investor Relations Contacts: Enoch Kariuki, Pharm.D.Synthorx, Inc.ekariuki@synthorx.com858-750-4750

Christina TartagliaStern IR, Inc.christina.tartaglia@sternir.com212-362-1200

Media Relations Contact:Lauren FishCanale Communicationslauren@canalecomm.com619-849-5386