Octreotide is an octapeptide analog of somatostatin that binds to somatostatin receptors (SSTRs) with a higher affinity for the somatostatin subgroup 2 receptors, SST, SST, and SST (Ks = 875, 0.57, 26.8, >1,000, and 6.8 nM for SST receptors, respectively). Within subgroup 2 SSTRs, it selectively binds to SST over SST and SST receptors with IC values of 0.02, 92.9, and 21.8 nM, respectively, for human receptors. Octreotide inhibits the secretion of growth hormone in vitro in rat pituitary cells three-fold more potently than somatostatin and in vivo in rhesus monkey (ID = 0.38 µg/kg per hour). It inhibits proliferation of VEGF-stimulated human umbilical endothelial cells (HUVECs) with an EC value of approximately 1 µM. It also inhibits growth of LCI-D20 human hepatocellular carcinoma cell tumors in a nude mouse xenograft model when administered at a dose of 50 µg/kg twice daily. Formulations containing octreotide have been used in the treatment of acromegaly to reduce growth hormone and IGF-1 levels.