Novel anti-VEGF scFv antibodies with superior in vitro and in vivo activities.

Vascular Endothelial Growth Factor (VEGF) plays important roles in the pathogenesis of age-related macular degeneration (AMD), the most common cause of vision loss in the elderly. Intravitreal anti-VEGF injection is the gold standard for AMD treatment. Here three novel anti-VEGF single chain variable fragments (scFvs) produced in Pichia pastoris system are reported. First, an scFv was designed based on the variable chain sequence of ranibizumab, then rational mutations were introduced to find the best variant(s). Mutagenesis of two residues that normally reside at the Fab V(L)- C(L) resulted in three mutant scFv variants (scFv1, 2, 3) with high affinity to VEGF and good thermal stability. scFv1 and scFv2 outperformed ranibizumab at the HUVEC proliferation inhibition test. The activities of the variants were compared to bevacizumab, ranibizumab and brolucizumab with VEGF bioassay. scFv1 and scFv2 together with brolucizumab performed best, which was seconded by scFv3 and ranibizumab, while all variants performed better than bevacizumab. scFv1 was selected as the lead molecule based on its improved in vivo activity in zebrafish angiogenesis and leaky retinal vasculature models. scFv1 inhibits in vitro angiogenesis and binds selectively to all VEGFA isoforms. The engineered anti-VEGF scFv1, is a promising therapeutic candidate for AMD treatment.