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Synthorx to Present at the 2019 American Society of Clinical Oncology (ASCO) Annual Meeting

May 15, 2019

SAN DIEGO, May 15, 2019 (GLOBE NEWSWIRE) -- Synthorx, Inc. (NASDAQ: THOR), a biotechnology company discovering and developing optimized biologics for cancer and autoimmune disorders, today announced company researchers will present preclinical data demonstrating the potential safety and anti-tumor effects of its lead product candidate, THOR-707, a “not alpha” Synthorin™ of interleukin-2 (IL-2) for the treatment of solid tumors at the 2019 American Society of Clinical Oncology (ASCO) Annual Meeting taking place May 31 – June 4 at McCormick Place, Chicago, IL. Marcos Milla, PhD., chief scientific officer of Synthorx, will present the company’s approach to utilizing its first-of-its-kind Expanded Genetic Alphabet platform technology to engineer IL-2 to improve its pharmacological profile.

The presentation, titled “THOR-707: Using synthetic biology to reprogram the therapeutic activity of interleukin-2 (IL-2),” describes the use of the Synthorx Expanded Genetic Alphabet platform technology to design THOR-707, a recombinant IL-2 that that is pegylated at one specific site, intended to block engagement of the alpha chain of the IL-2 receptor. In preclinical models, the “not alpha” feature of THOR-707 prevents proliferation of immunosuppressive CD4+ regulatory T cells as well as activation of non-lymphoid cells that trigger the serious complication of vascular leak syndrome (VLS) when IL-2 is used to treat cancer patients.

The poster presentation will include data demonstrating expansion of CD8+ T cells without eosinophilia (a measurement of VLS) and durability of the CD8+ T cell expansion, regardless of whether THOR-707 is administered every 2, 3 or 4 weeks. The data also demonstrate that an anti-PD-1 antibody, when combined with THOR-707, increases interferon-gamma (IFN‑γ) release from T cell receptor-activated T cells, indicating the potential of this combination to enhance anti-tumor effects. The durability of these effects was demonstrated in a tumor model where re-challenged animals initially cured with THOR-707 + anti-PD-1 were found to reject additional challenges with tumor cells without subsequent drug administration. These data support the establishment of persistent anti-tumor memory T cell populations.

“Our preclinical data highlights the ways our Expanded Genetic Alphabet platform technology shows the potential of significantly improving both the safety profile and pharmacological properties of IL-2,” said Dr. Milla of Synthorx. “Taken together, the favorable pre-clinical attributes of THOR-707 suggest that this may provide a product with prolonged immuno-stimulatory effects, clinically meaningful anti-tumor activity, minimal regulatory T cell-driven immunosuppression and significantly decreased risk for VLS coupled with convenient dosing for the patient.” The company plans to file its IND application for THOR-707 in the second quarter of 2019.

Details of the ASCO poster presentation are as follows:

Title: THOR-707: Using synthetic biology to reprogram the therapeutic activity of interleukin-2 (IL-2)Presenter: Marcos E. Milla, Ph.D., Chief Scientific Officer, SynthorxAbstract #: 2603Session: Developmental Immunotherapy and Tumor ImmunobiologySession Date/Time: Saturday, June 1, 2019, 8:00 a.m. – 11:00 a.m. CDTAuthors: M. E. Milla, J. Ptacin, C. E. Caffaro, H. R. Aerni, L. Ma, L. Koriazova, I. B. Joseph, L. K. ShawverA copy of the poster will be available at the time of the presentation and archived on the Scientific Publications page of the company’s website, https://synthorx.com/scientific-publications/.

About SynthorxSynthorx, Inc. is a biotechnology company focused on prolonging and improving the lives of people with cancer and autoimmune disorders. Synthorx’s 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 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 in Dr. Floyd Romesberg’s lab at The Scripps Research Institute. Synthorx is headquartered in La Jolla, Calif. For more information, visit www.synthorx.com.

Forward-Looking StatementsThis 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-707 and the development of Synthorx’s 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’s 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’s plans to develop and commercialize its product candidates; the potential for any future clinical trials of THOR-707 or other product candidates to differ from preliminary or expected results; Synthorx’s 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’s reliance on key third parties, including contract manufacturers and contract research organizations; Synthorx’s 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