A synthetic cyclic octapeptide analogue of somatostatin with direct and indirect antitumor effects. Vapreotide binds to somatostatin receptors (SSTR), specifically SSTR-2 and to SSTR-5 with a lesser affinity, in the similar behaviors as other octapeptide somatostatin analogues. Like octreotide, this agent has direct and indirect antitumor effects via inhibiting the release of growth hormone and other peptides that regulate release of insulin, gastrointestinal hormones. Furthermore, vapreotide may also be useful for inducing hemostasis in cases of acute hemorrhage of the upper gastrointestinal tract.