Press Release

Long acting growth hormone based on Amunix’ XTEN® technology completes enrollment of Phase 3 trial

MOUNTAIN VIEW, CA–(Marketwired – September 1, 2016) – Amunix is pleased to announce that Versartis, Inc (NASDAQ:VSAR) has completed enrollment of a Phase 3 study of somavaratan (XTENylated recombinant growth hormone) in pediatric patients with growth hormone deficiency.

Somavaratan is a long-acting version of growth hormone created using Amunix’s XTEN technology under license to Versartis. Somavaratan’s twice-monthly dosing schedule in pediatric patients is the least frequent dosing interval in development for long-acting growth hormones.

Versartis disclosed that 137 patients have now been enrolled in the VELOCITY trial that is powered at > 90% to demonstrate non-inferiority of somavaratan compared to daily rhGH. Patients will be followed for the primary trial endpoint of height velocity at 12 months, as well as safety and pharmacodynamic secondary endpoints. Top-line results are expected in Q3 2017.

“The news serves as continuing validation of XTEN as a robust half-life extension platform,” said Volker Schellenberger, Amunix’s Chief Executive Officer.“ We are encouraged by the continued clinical progress of XTENylated growth hormone and look forward to completion of the ongoing study and the top-line results as a major step in the overall development program.”


Amunix, based in Mountain View, CA, is a privately held biotechnology company focused on the discovery and development of novel therapeutics with improved in vivo half-lives. Amunix’s half-life extension technology is based on XTEN — hydrophilic, unstructured, biodegradable proteins that impart a number of favorable properties upon the molecules to which they are attached. XTEN can be recombinantly fused or chemically conjugated to peptides, proteins, and other pharmaceuticals. In addition to the advantages of reduced dosing frequency, XTENylation also stabilizes plasma drug concentrations, which often results in increased efficacy as well as reduced side effects. Two genetically fused XTENylated products have been tested clinically. VRS-859 (exenatide-XTEN) has been tested through Phase 1 in the treatment of Type II diabetes and VRS-317 (human growth hormone-XTEN), for which enrollment has been completed for the Phase 3 trial. Amunix is also working with other partners, including Eli Lilly, Biogen, Roche, Janssen, Naia and other undisclosed partners in a wide range of therapeutic areas. Amunix is developing an internal pipeline of ProTIA (Protease Triggered Immune Activator) immuno-oncology therapeutics. ProTIAs are bispecific molecules that bind tumor antigens and T cells. ProTIAs are administered as long-acting prodrugs that can be activated in the tumor environment by tumor-associated proteases. Amunix is actively seeking partnerships for application of its XTEN technology and its ProTIA platform. For additional information about the company, please visit

Volker Schellenberger, Ph.D.
President and CEO
Tel: 650-889-5095