Title:
Post-antibody Drugs: In vitro evolution for molecular-targeting helix-loop-helix peptides

 

Speaker:
Ikuo Fujii
Department of Biological Science Osaka Prefecture University,
1-1, Gakuen-cho, Naka-ku, Osaka 599-8531 (Japan)
email: fujii(at)b.s.osakafu-u.ac.jp

Keywords: in vitro evolution, helix-loop-helix peptides, phage-displayed libraries

 

Abstract:
Antibodies are indisputably the most successful reagents in molecular-targeting therapy. However, use of antibodies has been limited due to the biophysical properties and the cost to manufacture. To enable new applications where antibodies show some limitations, we have developed an alternative-binding molecule with non-immunoglobulin domain [1]. The molecule is a helix-loop-helix (HLH) peptide, which is stable against enzyme degradations in vivo and is too small to show immunogenicity. Here, we introduce our HLH molecular-targeting peptides, termed “microAntibodes”, that show antibody-like functions, high affinity and high specificity for the targeted proteins.
Since the HLH peptide folds by virtue of hydrophobic and electrostatic interactions between the amino acid residues positioned inside the molecule, the outside solvent-exposed residues are possible to be mutated with a variety of amino acids to give a combinatorial library of the HLH peptides. Based on our technology of phage-displayed libraries for catalytic antibodies [2, 3], we constructed a phage-displayed library of the HLH peptides. The library was screened against G-CSF receptor to give a binding peptide, which was cyclized by a thioether linkage between the N- and C-termini [4]. The cyclic peptide showed a strong binding affinity (Kd of 4 nM) to the receptor and a long half-life (>2 weeks) in mouse sera, proving an enzyme-resistant property. Immunization of the HLH peptide to mice showed no induction of the antibody production (non-immunogenic). We have applied our HLH peptide libraries for VEGF, IgG/Fc, interleukins (IL-5, IL-6), and kinases (Aurora A) to obtain their molecular-targeting peptides “microAntibodies”[4-7]. In addition, we used the HLH peptide as a scaffold for generating cell permeable molecular-targeting peptides through bi-functional grafting: epitope grafting to provide binding activity and arginine grafting to endow cell-permeability [8].

 

[1]I. Fujii, Y. Takaoka, K. Suzuki and T. Tanaka, Tetrahedron Lett., 42, 3323-3325 (2001).
[2]I. Fujii, S. Fukuyama, Y. Iwabuchi, R. Tanimura, Nature Biotechnology, 16, 463-467 (1998).
[3]N. Takahashi, H. Kakinuma, L. Liu, Y. Nishi, and I. Fujii, Nature biotechnology, 19, 563-567 (2001).
[4]D. Fujiwara, Z. Ye, M.Gouda, K. Yokota, T. Tsumuraya, and I. Fujii, Bioorg. Med. Chem. Lett., 20 1776–1778 (2010).
[5]T. Matsubara, M. Iida, T. Tsumuraya, I. Fujii, and T. Sato. Biochemistry, 47, 6745–6751 (2008).
[6]D. Fujiwara and I. Fujii, Current Protocols in Chemical Biology 5, 171-194 (2013).
[7]K. Kawabata , H. Nagai , N. Konishi , D. Fujiwara, R. Sasaki, T. Ichikawa, I. Fujii, Bioorg. Med. Chem. 22 1845–1849 (2014).
[8]D. Fujiwara, et al., H. Kitada, M. Oguri, T. Nishihara, M. Michigami, K. Shiraishi, E.Yuba, I. Nakase, H. Im, S. Cho, J. Y. Joung, S. Kodama, K. Kono, S. Ham, and I. Fujii, Angew. Chem. Int. Ed. 55, 10612-10615 (2016).