The Journal of pharmacology and experimental therapeutics 2018 03 05() pii 10.1124/jpet.117.246249
Angiogenesis mediated by vascular endothelial growth factor (VEGF) is a hallmark of glioblastoma. Based on response rate and improved progression-free survival (PFS), although not overall survival (OS), the 149 kDa anti-VEGF-A IgG antibody bevacizumab (Avastin) has been approved in the US and Japan for recurrent glioblastoma and in Japan for newly diagnosed glioblastoma. However, it is not approved in the EU. Here we characterize the biological activity of DLX1008, a 26 kDa anti-VEGF-A single chain antibody fragment (scFv) which shows 30-fold stronger affinity to human VEGF-A than bevacizumab. The small molecular size of DLX1008 is predicted to result in improved target coverage over bevacizumab. DLX1008 showed superiority to bevacizumab in the inhibition of VEGF-A binding to VEGF receptor (VEGFR) 1 in ELISA by a factor of around 10 and comparable efficacy for the inhibition of VEGF-A-stimulated VEGFR2 dimerization. In a tube formation assay with human cerebral microvascular endothelial cells (hCMEC), DLX1008 was at least as active as bevacizumab. In vivo, DLX1008 delayed growth in a mouse subcutaneous U87 xenograft model (p=0.0021) and improved survival in a mouse orthotopic U87 xenograft model (p=0.00026). Given its exceptionally high affinity and small molecule size, these data warrant further clinical development of DLX1008 as an antiangiogenic agent in glioblastoma.