Discussion

Amunix developed a hydrophilic protein-polymer (XTEN™) with long half-life in circulation that is rapidly degraded upon internalization. XTEN is monodisperse, extremely hydrophilic, and conjugation sites can be introduced in precisely controlled locations. Multiple clinical trials have demonstrated the ability of XTENylation to achieve weekly to monthly dosing of therapeutic peptides and proteins. XTEN allows multivalent as well as orthogonal coupling reactions to increase drug potency or to combine multiple biological activities into a single product. XTEN is stable in circulation but readily degraded upon internalization into cells, which makes it an ideal linker for tumor-targeted drug delivery. Antibodies, antibody fragments, as well as peptides and metabolites can be utilized for tumor targeting. The hydrophilic nature of XTEN allows high drug loads and reduces toxicity resulting from non-specific internalization.