Synthorx Initiates Patient Dosing in Australia and Announces Clearance of IND in the U.S. for Lead Immuno-oncology Product Candidate, THOR-707

La Jolla, California, UNITED STATES

SAN DIEGO, July 24, 2019 (GLOBE NEWSWIRE) -- Synthorx, Inc. (NASDAQ: THOR), a clinical-stage biotechnology company developing optimized therapeutics for cancer and autoimmune disorders, announced today it has opened HAMMER, a global, Phase 1/2, first-in-human clinical trial of THOR-707, with Australia being the first region to enroll patients to date. In addition, the company has received clearance from the Food and Drug Administration (FDA) for the Investigational New Drug (IND) Application for THOR-707, paving the way for patient enrollment to proceed in the U.S. The single agent and combination arms of the trial are evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics and anti-tumor activity of THOR-707 in patients with advanced or metastatic solid tumors.

“Our preclinical studies of THOR-707 have shown expansion of NK and CD8+ T cells, and durable anti-tumor effects without vascular leak syndrome (VLS), the toxicity that has limited the use of high-dose IL-2”, said Laura Shawver, Ph.D., president and chief executive officer of Synthorx. “Taken together, the favorable pre-clinical attributes of THOR-707 suggest that this may provide a differentiated product with clinically meaningful anti-tumor activity, minimal regulatory T cell-driven immunosuppression and convenient dosing schedules for patients”. This is the first Synthorin to enter the clinic engineered using Synthorx’ Expanded Genetic Alphabet platform, which enables the site-specific incorporation of novel amino acids to enhance the pharmacological properties of protein therapies like IL-2.

More information about the trial is available at

About THOR-707
THOR-707 is the first product candidate designed using Synthorx’ Expanded Genetic Alphabet platform technology. THOR-707 is a recombinant interleukin-2 (IL-2) cytokine that is pegylated at one specific site, intended to block engagement of the high affinity IL-2 receptor alpha chain while retaining potency on the beta chain, thereby maintaining potent effector T-cell anti-tumor activity while exhibiting an improved safety profile. In preventing engagement of the alpha chain of the receptor, the IL-2 product can be dosed for expansion of CD8+ T cells, without expansion of immune-suppressive regulatory CD4+ T cells, and without activation of non-lymphoid cells that trigger the sometimes-fatal complication of vascular leak syndrome, observed with approved recombinant IL-2 (aldesleukin). This site-specific pegylation also increases the pharmacokinetic properties of THOR-707, including a longer half-life.

About Synthorx
Synthorx, Inc. is a 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 product candidate, THOR-707, a variant of IL-2, is in development for the treatment of solid tumors as a single agent and in combination with an immune checkpoint inhibitor. The company was founded based on important discoveries at The Scripps Research Institute. The company is headquartered in La Jolla, Calif. For more information, visit

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-707 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-707 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

Investor Contacts:
Enoch Kariuki, Pharm.D.
Synthorx, Inc.

Christina Tartaglia
Stern Investor Relations

Media Relations Contact:
Lauren Fish
Canale Communications