Pancreatic adenocarcinoma is a leading cause of cancer death in the United States and represents a challenging chemotherapeutic problem. The pharmacological control of angiogenesis might represent a novel approach to the management of pancreas cancer, since the pathological development of vascular supply is a critical step for tumor growth and may affect its prognosis. In order to test this hypothesis, SU5416 ([3-(3,5-dimethyl-1H-pyrrol-2-ylmethylene)-1,3-dihydro-indol-2-one]) a selective inhibitor of the vascular endothelial growth factor receptor-2 tyrosine kinase, and gemcitabine (2', 2'-difluorodeoxycytidine) were tested on endothelial (HUVEC) and pancreatic tumor cells (MIA PaCa-2) in vitro and in vivo alone and in simultaneous association. SU5416 inhibited HUVEC cells stimulated to proliferate by vascular endothelial growth factor but not MIA PaCa-2 cells; the drug concentration that decreased cell growth by 50% (IC50) was 0.14 microM. Furthermore, SU5416 reduced the development of microvessels from placental explants (IC50, 0.23 microM). Gemcitabine inhibited the growth of both HUVEC and MIA PaCa-2 cells with an IC50 of 0.08 and 0.1 microM, respectively. A synergistic effect (combination index <1 and dose reduction index >1) on anti-proliferative and pro-apoptotic activity was calculated with the simultaneous combination of the two drugs on endothelial cells. A marked in vivo antitumor effect on MIA PaCa-2 xenografts was observed with SU5416 at a protracted schedules, as well as with gemcitabine; furthermore, the combination between the two drugs resulted in an almost complete suppression of tumor growth and relapse. In conclusion, the present results provide the evidence of an effective anti-endothelial/antitumor activity of protracted administration of SU5416 on human pancreas cancer xenografts, which is comparable with the one obtained by gemcitabine; moreover, the synergistic combination between these drugs on endothelial cells and the promising association in pancreatic cancer xenografts could be used in future studies and translated into the clinical setting.