TT-232 is a structural derivative of the natural signal inhibitory peptide somatostatin, with selective antiproliferative and anti-inflammatory properties. TT-232 has no growth hormone release inhibitory effect and does not inhibit the secretion of gastric acid. This analog induces apoptosis in and exerts pronounced antiproliferative effects on various human tumors (colon, pancreas, lymphoma, leukemia, melanoma, hepatoma) cell lines. The growth of human xenografts (prostate, breast carcinoma, lymphoma, melanoma) and animal tumors (colon-26, P-388, S-180, B16, MXT) was inhibited by TT-232 (dose range: 30-750 microg/kg/day) in 54-98% of cases. TT-232 activates SSTR receptors (primarily the SSTR-1), which leads to irreversible cell cycle arrest, followed by secondary induction of apoptosis. TT-232 activates cell cycle inhibitors via SSTR receptors, inhibits tyrosine kinases through interfering with the proliferative signaling cascades, and interacts with an intracellular receptor and an enzyme involved in glycolysis causing translocation of this enzyme to the nucleus, thus inducing apoptosis. TT-232 was a promising candidate in the therapy of human malignancies. TT-232 has passed phase I clinical trials without toxicity and significant side-effects. However TT-232 development has been discontinued.