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Overview

Amunix was founded in 2006 to create protein pharmaceuticals with improved safety and performance by using non-human sequences that have been designed to be non-immunogenic in multiple species. We refer to such sequences as ‘hypotopic’.

Our primary focus is the design and early development of protein pharmaceuticals with an extended serum half-life, which require less frequent injection. The increased half-life is obtained by the genetic fusion of a long, hydrophilic, unstructured polyamino acid tail, referred to as ‘XTEN’. When fused to existing approved products, we call these ‘Biosuperiors’.

’XTEN’ products offer improved safety potential over PEGylated products, because XTEN is degraded after uptake by cells, whereas PEG is not and can accumulate to form vacuoles in kidney cells.

XTEN products also offer improved safety potential over Fc fusions because XTEN, like PEG, has been shown to reduce the immunogenicity of the payload, whereas Fc fusions do not.

In addition, many XTEN products offer safety potential because their relatively steady serum concentration avoids the peak dose toxicity and high peak-to-trough concentration ratio that is generally blamed for most of the side effects.

One area where we apply XTEN is in the development of products derived from non-human microproteins. We focus on potent modulators of valuable targets like ion channels and GPCRs, which occur as disulfide-rich toxins in the venoms of snakes, spiders, scorpions and snails.

In extensive immunization studies in four species, we have shown that two types of protein structures have especially low immunogenicity: highly flexible, unstructured, hydrophilic sequences that resemble polyethylene glycol (called XTEN), and rigidly structured multi-disulfide domains, called microproteins. Neither of these extremes of structure comprises a hydrophobic core, which typical globular protein require for folding. This hydrophobic core appears to be the focus of the immune system, because of its high content of hydrophobic residues, which are required anchor residues for the binding of proteolytic peptides to the MHC. In addition, both structures are highly resistant to proteolysis, because of high entropy for XTEN and because of the multi-disulfide core in the microproteins, many of which are protease inhibitors.