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A recombinant polypeptide extends the in vivo half-life of peptides and proteins in a tunable manner


Increasing the in vivo residence times of protein therapeutics could decrease their dosing frequencies. We show that genetic fusion of an unstructured recombinant polypeptide of 864 amino acids, called XTEN, to a peptide or protein provides an apparently generic approach to extend plasma half-life. Allometric scaling suggests that a fusion of XTEN to the exenatide peptide should increase exenatide half-life in humans from 2.4 h to a projected time of 139 h. We confirmed the biological activity of the exenatide-XTEN fusion in mice. As extended stability might exacerbate undesirable side effects in some cases, we show that truncating the XTEN sequence can regulate plasma half-life. XTEN lacks hydrophobic amino acid residues that often contribute to immunogenicity and complicate manufacture. Based on data on XTEN fusions to exenatide, glucagon, GFP and human growth hormone, we expect that XTEN will enable dosing of otherwise rapidly cleared protein drugs at up to monthly intervals in humans.

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Figure 1: Production and biophysical characterization of an exenatide-XTEN (E-XTEN) fusion protein.
Figure 2: In vivo characterization of E-XTEN.
Figure 3: Allometric scaling of E-XTEN to humans using data from four species.

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The size exclusion chromatography–multi-angle light scattering analysis was conducted by E. Folta-Stogniew at the W.M. Keck Foundation Biotechnology Resource Laboratory. The mass spectrometry was performed at MDS Analytical Technologies by A. Booy. The Macrocap Q resin was kindly provided by J. Lundberg from GE Healthcare. The project described was supported by award number R44GM079873 from the National Institute of General Medical Sciences. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of General Medical Sciences or the National Institutes of Health.

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Authors and Affiliations



V.S., design of XTEN sequences and constructs, data analysis; C.-W.W., design of XTEN sequences and constructs; N.C.G., design of XTEN sequences and constructs, preparation/characterization of proteins, data analysis; B.J.S., design of XTEN sequences and constructs, preparation/characterization of proteins, data analysis; A.C., managing animal studies, animal sample analysis, data analysis; W.T., preparation/characterization of proteins; M.D.S., design of XTEN sequences and constructs; Y. Yin, design of XTEN sequences and constructs, preparation/characterization of proteins; Y. Yao, preparation/characterization of proteins; O.B., design of XTEN sequences and constructs; J.L.C., design of XTEN sequences and constructs, data analysis; J.S., design of XTEN sequences and constructs, data analysis; W.P.C.S., design of XTEN sequences and constructs, data analysis.

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Correspondence to Willem P C Stemmer.

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Competing interests

V.S., C.-W. W., N.C.G., B.J.S., A.C., W.T., M.D.S., Y.Yin, Y.Yao, O.B. J.S. & W.P.C.S. are employees of Amunix. J.L.C. is an employee of Versatis.

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Schellenberger, V., Wang, Cw., Geething, N. et al. A recombinant polypeptide extends the in vivo half-life of peptides and proteins in a tunable manner. Nat Biotechnol 27, 1186–1190 (2009).

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