Inhibition of human leukemia in an animal model with human antibodies directed against vascular endothelial growth factor receptor 2. Correlation between antibody affinity and biological activity

Abstract

Vascular endothelial growth factor (VEGF) and its receptors (VEGFR) have been implicated in promoting solid tumor growth and metastasis via stimulating tumor-associated angiogenesis. We recently showed that certain 'liquid' tumors such as leukemia not only produce VEGF, but also express functional VEGFR, resulting in an autocrine loop for tumor growth and propagation. A chimeric anti-VEGFR2 (or kinase insert domain-containing receptor, KDR) antibody, IMC-1C11, was shown to be able to inhibit VEGF-induced proliferation of human leukemia cells in vitro, and to prolong survival of nonobese diabetic-severe combined immune deficient (NOD-SCID) mice inoculated with human leukemia cells. Here we produced two fully human anti-KDR antibodies (IgG1), IMC-2C6 and IMC-1121, from Fab fragments originally isolated from a large antibody phage display library. These antibodies bind specifically to KDR with high affinities: 50 and 200 pM for IMC-1121 and IMC-2C6, respectively, as compared to 270 pM for IMC-1C11. Like IMC-1C11, both human antibodies block VEGF/KDR interaction with an IC(50) of approximately 1 nM, but IMC-1121 is a more potent inhibitor to VEGF-stimulated proliferation of human endothelial cells. These anti-KDR antibodies strongly inhibited VEGF-induced migration of human leukemia cells in vitro, and when administered in vivo, significantly prolonged survival of NOD-SCID mice inoculated with human leukemia cells. It is noteworthy that the mice treated with antibody of the highest affinity, IMC-1121, survived the longest period of time, followed by mice treated with IMC-2C6 and IMC-1C11. Taken together, our data suggest that anti-KDR antibodies may have broad applications in the treatment of both solid tumors and leukemia. It further underscores the efforts to identify antibodies of high affinity for enhanced antiangiogenic and antitumor activities.

Activation of FGFR1β signaling pathway promotes survival, migration and resistance to chemotherapy in acute myeloid leukemia cells

“…13 More recently, paracrine (leukemia-stroma) and autocrine (leukemia-leukemia) VEGF/VEGFR signaling loops have been identified in AML. [14][15][16][17][18] However, the role of FGFs and specific FGFRs in the regulation of leukemic cell growth has not been studied, in part because reagents to block FGFR signaling have not been available. Because FGFR1 signaling is critical in hematopoietic stem cells, 3,4,19 we hypothesized that FGF/ FGFR1 signaling may also be active in leukemias.…”

Animal models of acute myelogenous leukaemia – development, application and future perspectives

“…The engraftment of human AML cells in the NOD/ SCID model has subsequently facilitated development of several new treatment modalities. 4,276,[374][375][376][377][378][379][380][381][382][383] Despite the obvious advantages of the NOD/SCID model over all other immunodeficient models, there are still some inherent obstacles. While various strategies, including hu-cytokine supplementation, 364,370,[384][385][386] co-transplantation of growth factor-producing cell lines or 'accessory cells' 384,385 have been evaluated, only 70% of all AML samples exhibit detectible engraftment in NOD/SCIDs.…”

Angiogenesis inhibitors in gastric and gastroesophageal junction cancer

“…Preclinical study results highlighted that blocking this VEGF family receptor was associated with the inhibition of VEGF-mediated signaling, proliferation and migration of human endothelial cells, and antitumor activity in animal models [43][44][45][46][47]. More recently, two phase III clinical trials have shown that ramucirumab is a valuable therapeutic option in GC ( Table 2).…”