As a method for extending half-life of protein therapeutics, traditional chemical pegylation is an effective but blunt instrument that adds time and cost to manufacturing, and produces formulations likely to be covered by IP protecting the original protein. Versartis Inc., a JV between Index Ventures and Amunix Inc., says drug candidates made by Amunix's recombinant XTEN technology are patentable molecules that do not require additional manufacturing steps and can be fine-tuned for desired half-life.

The company has rights to three preclinical candidates from Amunix: VRS-317 (hGH-XTEN) to treat growth hormone deficiency, VRS-826 (IL-1ra-XTEN) to treat rheumatoid arthritis (RA) and VRS-859 (exenatide-XTEN) to treat diabetes. Versartis has an option to three more compounds.