The angiogenesis inhibitor O-(chloroacetyl-carbamoyl)fumagillol (TNP-470) showed antitumor activity in three human cancer xenograft systems. TNP-470 potently inhibited the tumor growth of hormone-independent prostate cancer PC-3 cells and breast cancer MDA-MB-231 cells dose dependently at weekly s.c. doses of 50–200 mg/kg with maximum inhibition of 96 and 88% (tumor growth, 4 and 12% of that in the respective control). In experiments of combination therapy with chemotherapeutic agents, the combination of TNP-470 (100 mg/kg) and cisplatin (5 mg/kg) showed an additive antitumor effect (from treated versus control, 38 and 22% to 5%) against PC-3 carcinoma. 5-Fluorouracil and Adriamycin alone did not significantly inhibit MDA-MB-231 tumor growth (treated versus control, 131 and 64%, respectively). TNP-470 also inhibited tumor growth of WiDr colon cancer, although the inhibition was less marked (treated versus control, 39%) than that observed with the hormone-independent cancers used in this study.
In an in vitro study, all the cell lines tested were considerably insensitive to TNP-470 in monolayer cultures (50% inhibitory concentration, approximately 5 µg/ml), whereas TNP-470 inhibited the anchorage-independent growth of PC-3 and MDA-MB-231 cells (50% inhibitory concentration, 0.05 and 470 ng/ml, respectively). The inhibitory activity of TNP-470 against anchorage-independent growth correlated well with the in vivo antitumor activity among the cell lines tested. Thus, this inhibitory action may partly contribute to the potent antitumor activity of the angiogenesis inhibitor TNP-470, at least in the case of PC-3 and MDA-MB-231.
These results suggest that hormone-independent prostate and breast cancers may be appropriate target diseases for TNP-470 clinical trials.