THOR Synthorx Inc

Synthorx, Inc. (NASDAQ: THOR), a clinical-stage biotechnology company developing optimized therapeutics for cancer and autoimmune disorders, today announced the presentation of three  posters at the upcoming Society for Immunotherapy of Cancer (SITC) 34th Annual Meeting in National Harbor, MD, from November 6-10, 2019. These posters will highlight the company’s lead product candidate THOR-707 and two of its other Synthorin™ cytokines for immuno-oncology.

We will present an update on the HAMMER study with a trial in progress poster. “HAMMER is a three-part global Phase 1/2 dose escalation and expansion study evaluating the safety and anti-tumor activity of THOR-707, our not-alpha IL-2 Synthorin, in patients with advanced or metastatic solid tumors. Part 1 of the study will determine the recommended phase 2 dose (RP2D) of THOR-707 as a single agent and part 2 will determine the RP2D of THOR-707 in combination with a PD-1 inhibitor. Part 3 of the study will continue to evaluate safety along with the anti-tumor activity of THOR-707 alone or in combination with a PD-1 or PD-L1 inhibitor as well as in combination or sequenced with other established and emerging immuno-oncology therapies via dose expansion.” said Joseph A. Leveque, M.D., Chief Medical Officer.

In addition, posters on IL-15 and IL-10 Synthorins will be presented.  “IL-15 and IL-10 each have unique biological properties that are promising for the treatment of cancer, but in their unmodified forms have therapeutic limitations.  Our work presented in the posters showcase the versatility of our Expanded Genetic Alphabet Platform, demonstrating how site-specific pegylation can improve the pharmacological and pharmacokinetic properties of IL-15, and enable the discovery of improved IL-10 variants” said Marcos E. Milla, Ph.D., chief scientific officer, Synthorx.

Details of the poster presentation are as follows. The full abstracts will be made available on the SITC website on November 5, 2019 at 8:00 a.m. ET.

An Open-Label, Multicenter Phase 1/2 Dose Escalation and Expansion Study of THOR-707 as a Single Agent and in Combination with a PD-1 Inhibitor in Adult Subjects with Advanced or Metastatic Solid TumorsAbstract Number: P430Presenter: Joseph Leveque, MDSession Date & Time: Saturday, November 9, 2019, 7:00 a.m. – 8:00 p.m. ET (hosted from 12:35 p.m. – 2:05 p.m.)Category: Clinical Trial in Progress

Discovery of Pharmacologically Differentiated Interleukin 15 (IL-15) Agonists Employing a Synthetic Biology PlatformAbstract Number: 613Presenter: Carolina E. Caffaro, PhDSession Date & Time: Friday, November 8, 2019, 7:00 a.m. – 8:00 p.m. ET (hosted from 12:30 p.m. – 2:00 p.m.)Category: Immune-stimulants and immune modulators

Using a Novel Synthetic Biology Platform to Generate a Homogeneous Dipegylated IL-10 with Native PotencyAbstract Number: P612Presenter: Carolina E. Caffaro, PhDSession Date & Time: Saturday, November 9, 2019, 7:00 a.m. – 8:00 p.m. ET (hosted from 12:35 p.m. – 2:05 p.m.)Category: Immune-stimulants and immune modulators

The Synthorx posters and related materials will be available at the time of each of the presentations and 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 plans underlying THOR-707 clinical trials and development, preclinical data or plans underlying Synthorx’s IL-10 and IL-15 Synthorins 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 clinical trials of THOR-707 or any future clinical trials of Synthorx’s IL-10 and IL-15 Synthorins 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.com 858-750-4750

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

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