Engineering superactive granulocyte macrophage colony-stimulating factor transferrin fusion proteins as orally-delivered candidate agents for treating neurodegenerative disease

• Published in: Biotechnology progress Vol. 31; no. 3; pp. 668 - 677
• Main Authors: Heinzelman, Pete, Priebe, Molly C.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.05.2015; Wiley Subscription Services, Inc
• Subjects: Administration, Oral; Alzheimer Disease - drug therapy; Alzheimer's disease; Cell Line; Cell Proliferation - drug effects; Cytokine Receptor Common beta Subunit - metabolism; Dose-Response Relationship, Drug; granulocyte macrophage colony-stimulating factor (GM-CSF); Granulocyte-Macrophage Colony-Stimulating Factor - genetics; Granulocyte-Macrophage Colony-Stimulating Factor - pharmacology; Humans; Neurodegenerative Diseases - drug therapy; Parkinson Disease - drug therapy; Parkinson's disease; Receptors, Granulocyte-Macrophage Colony-Stimulating Factor - genetics; Receptors, Granulocyte-Macrophage Colony-Stimulating Factor - metabolism; Recombinant Fusion Proteins - biosynthesis; Surface Plasmon Resonance; Transferrin - genetics; Transferrin - pharmacology; transferrin receptor; yeast surface display; Yeasts - drug effects; Yeasts - metabolism; granulocyte macrophage colony-stimulating factor (GM-CSF); transferrin receptor; Parkinson's disease; yeast surface display; Alzheimer's disease
• ISSN: 8756-7938; 1520-6033
• DOI: 10.1002/btpr.2071

Intravenously injected granulocyte macrophage colony‐stimulating factor (GM‐CSF) has shown efficacy in Alzheimer's Disease (AD) and Parkinson's Disease (PD) animal studies and is undergoing clinical evaluation. The likely need for dosing of GM‐CSF to patients over months or years motivates pursuit of avenues for delivering GM‐CSF to circulation via oral administration. Flow cytometric screening of 37 yeast‐displayed GM‐CSF saturation mutant libraries revealed residues P12, H15, R23, R24, and K72 as key determinants of GM‐CSF's CD116 and CD131 GM‐CSF receptor (GM‐CSFR) subunit binding affinity. Screening combinatorial GM‐CSF libraries mutated at positions P12, H15, and R23 yielded variants with increased affinities toward both CD116 and CD131. Genetic fusion of GM‐CSF to human transferrin (Trf), a strategy that enables oral delivery of other biopharmaceuticals in animals, yielded bioactive wild type and variant cytokines upon secretion from cultured Human Embryonic Kidney cells. Surface plasmon resonance (SPR) measurements showed that all evaluated variants possess decreases in CD116 and CD131 binding KD values of up to 2.5‐fold relative to wild type. Improved affinity led to increased in vitro bioactivity; the most bioactive variant, P12D/H15L/R23L, had a leukocyte proliferation assay EC50 value 3.5‐fold lower than the wild type GM‐CSF/Trf fusion. These outcomes are important first steps toward our goal of developing GM‐CSF/Trf fusions as orally available AD and PD therapeutics. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:668–677, 2015