Synthorx, Inc. announced that 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. 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.