Press Release

Phase 3 enrollment initiated in Japan for Versartis’ long-acting growth hormone based on Amunix’ XTEN® technology

MOUNTAIN VIEW, CA–(Marketwired – September 30, 2016) – Amunix is pleased to announce that Versartis Inc. (NASDAQ:VSAR) has been granted approval in Japan by the PMDA to initiate enrollment for its Phase 3 study of somavaratan (XTENylated recombinant growth hormone) in pediatric patients with growth hormone deficiency (GHD).

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 the Phase 3 stage of the J14VR5 trial is a single-arm, multi-center trial evaluating the safety and efficacy of 3.5 mg/kg twice-monthly somavaratan, the same dose and regimen as the VELOCITY Phase 3 trial. Enrollment in the Phase 3 trial is expected to be completed in the third quarter of 2017, with topline data expected in 2018.

“The initiation of Phase 3 trials for somavaratan in Japan is great news and the continued progression of studies of XTENylated growth hormone in this important ex-US geography underscores the commitment on the part of the health authorities there towards such next generation therapies”, said Volker Schellenberger, Amunix’s Chief Executive Officer. “We are very encouraged by the sustained drive towards commercialization of somavaratan in all key geographies by Versartis”.


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 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, Baxalta, Ambrx, Zealand, Noxxon, 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