Brivanib, a Dual FGF/VEGF Inhibitor, Is Active Both First and Second Line against Mouse Pancreatic Neuroendocrine Tumors Developing Adaptive/Evasive Resistance to VEGF Inhibition

Abstract Purpose: Preclinical trials of a mouse model of pancreatic neuroendocrine tumors (PNET) were conducted to determine whether dual FGF/VEGF pathway inhibition with brivanib can improve first-line efficacy in comparison with VEGF inhibitors lacking fibroblast growth factor (FGF)-inhibitory activity and to characterize second-line brivanib activity before and after the onset of evasive resistance to VEGF-selective therapy. Experimental Design: An anti-VEGFR2 monoclonal antibody (DC101), an inhibitor of FGF signaling (FGF ligand trap), sorafenib, and brivanib were comparatively evaluated in first-line monotherapy in short and longer term fixed endpoint intervention trials in the RIP-Tag2 mouse model of PNET. Brivanib was also tested second line aiming to block adaptive resistance to selective VEGF therapies, assessing tumor growth, vascularity, hypoxia, invasion, and metastasis. The effects of initiating second-line brivanib therapy prior to or following overt relapse on sorafenib therapy were compared in overall survival trials to first-line therapies. Results: Brivanib produced enduring tumor stasis and angiogenic blockade, both first and second line following the failure of DC101 or sorafenib. Overall survival was significantly extended by brivanib versus sorafenib, both first-line and when second-line therapy was initiated prior to sorafenib failure; second-line brivanib was less beneficial when initiated later, after the initiation of revascularization and incipient tumor progression. Conclusions: Brivanib holds promise and deserves consideration for clinical evaluation as an antiangiogenic therapy, both in the context of impending failures of VEGF-selective therapy and in a first-line setting aiming to limit the adaptive response to VEGF inhibitors that results in evasive resistance. Clin Cancer Res; 17(16); 5299–310. ©2011 AACR.