Development of a mono-specific anti-VEGF bivalent nanobody with extended plasma half-life for treatment of pathologic neovascularization.

Vascular endothelial growth factor (VEGF) plays a crucial role in angiogenesis within solid cancers. Thus, targeting VEGF might be part of a feasible therapy for treating pathological neovascularization, and nanobodies - derived from heavy chain-only antibodies occurring within Camelidae - are a novel class of nanometer-sized antibodies possessing unique properties that could be developed into a promising therapeutic. However, nanobodies have a very short half-life in vivo due to their small size. Development of a bivalent nanobody is one way to remediate the half-life problem of nanobodies. Two identical anti-VEGF nanobodies were connected using the hinge region of llama IgG2c. The recombinant plasmid (pHEN6c-bivalent nanobody) was transformed into E.coli WK6 cells and expression of the bivalent nanobody construct was induced with 1mM Isopropyl β-D-1-thiogalactopyranoside (IPTG). Recombinant bivalent nanobody was purified using nickel affinity chromatography and its activity on human endothelial cells was assessed using 3-(4,5-Dimethylthiazol-2-yr)-2,5-diphenyltetrazolium bromide (MTT), tube formation, and cell migration assays. The pharmacokinetic study was performed after intravenous (i.v.) injection of recombinant bivalent nanobody into six-week-old C57BL/6 mice. Recombinant bivalent nanobody performed significantly better than monovalent nanobody in inhibiting proliferation, tube formation, and migration of human endothelial cells. Pharmacokinetic results showed a 1.8-fold longer half-life of bivalent nanobody in comparison with the monovalent nanobody. These results underscore the potential of recombinant anti-VEGF bivalent nanobody as a promising tool for development of a novel therapeutic with an extended plasma half-life for VEGF-related diseases.