Protein Engineering on Human Recombinant Follistatin: Enhancing Pharmacokinetic Characteristics for Therapeutic Application.

Abstract

Follistatin (FS) is an important regulatory protein, a natural antagonist for transforming growth factor-β family members activin and myostatin. The diverse biologic roles of the activin and myostatin signaling pathways make FS a promising therapeutic target for treating human diseases exhibiting inflammation, fibrosis, and muscle disorders, such as Duchenne muscular dystrophy. However, rapid heparin-mediated hepatic clearance of FS limits its therapeutic potential. We targeted the heparin-binding loop of FS for site-directed mutagenesis to improve clearance parameters. By generating a series of FS variants with one, two, or three negative amino acid substitutions, we demonstrated a direct and proportional relationship between the degree of heparin-binding affinity in vitro and the exposure in vivo. The triple mutation K(76,81,82)E abolished heparin-binding affinity, resulting in ∼20-fold improved in vivo exposure. This triple mutant retains full functional activity and an antibody-like pharmacokinetic profile, and shows a superior developability profile in physical stability and cell productivity compared with FS variants, which substitute the entire heparin-binding loop with alternative sequences. Our surgical approach to mutagenesis should also reduce the immunogenicity risk. To further lower this risk, we introduced a novel glycosylation site into the heparin-binding loop. This hyperglycosylated variant showed a 10-fold improved exposure and decreased clearance in mice compared with an IgG1 Fc fusion protein containing the native FS sequence. Collectively, our data highlight the importance of improving pharmacokinetic properties by manipulating heparin-binding affinity and glycosylation content and provide a valuable guideline to design desirable therapeutic FS molecules.

• Authors: Chuan Shen, Andrea Iskenderian, Dianna Lundberg, Tao He, Kathleen Palmieri, Robert Crooker, Qingwei Deng, Matthew Traylor, Sheng Gu, Haojing Rong, David Ehmann, Brian Pescatore, Bettina Strack-Logue, Alla Romashko, George Baviello, John Gill, Bohong Zhang, Muthuraman Meiyappan, Clark Pan, Angela W Norton
• Journal: The Journal of pharmacology and experimental therapeutics (J Pharmacol Exp Ther) Vol. 366 Issue 2 Pg. 291-302 (08 2018) ISSN: 1521-0103 [Electronic] United States
• PMID: 29752426 (Publication Type: Journal Article)
• Copyright: Copyright © 2018 The Author(s).

Chemical References

• Follistatin
• Recombinant Proteins
• Heparin

Topics

• Amino Acid Motifs
• Amino Acid Sequence
• Animals
• Female
• Follistatin (genetics, metabolism, pharmacokinetics, therapeutic use)
• Glycosylation
• Heparin (metabolism)
• Humans
• Mice
• Mutation
• Protein Engineering
• Recombinant Proteins (genetics, metabolism, pharmacokinetics, therapeutic use)
• Tissue Distribution