Small molecule inhibitors of methionine aminopeptidase type 2 (MetAP-2)

The protein processing enzyme, methionine aminopeptidase-2 (MetAP-2), has been identified as a molecular target of fumagillin and its derivative, TNP-470, compounds known to inhibit endothelial cell proliferation and angiogenesis. A high-throughput screening program was undertaken to identify selective, reversible inhibitors of MetAP-2 in an attempt to discover structurally novel anti-angiogenic agents for potential therapeutic use in oncology. Approximately 90 small-molecule, reversible, selective inhibitors of rhMetAP-2 were identified. The most potent of these compounds contained a singly-substituted triazole moiety which exhibited an IC50 of 8 nM (95% confidence limits 5 to 13 nM) and was highly selective for MetAP-2 over MetAP-1 (approximately 60-fold difference in IC50 values). Unlike fumagillin, these MetAP-2 inhibitors failed to significantly inhibit growth factor-stimulated endothelial cell (HUVEC) proliferation or to suppress angiogenesis in the in vitro aortic ring explant model of microvessel outgrowth. The MetAP-2-inhibitory activity of these compounds was dependent on the divalent cation used as the metalloenzyme activating cofactor for MetAP-2. These inhibitors were identified using cobalt(II)-activated recombinant human MetAP-2 for screening compound libraries. When manganese (Mn2+) was substituted for cobalt following EDTA treatment and extensive dialysis of the MetAP-2 protein, these inhibitors were significantly less potent (40-fold increase in IC50) as inhibitors of MetAP-2. These results support the recent hypothesis that cobalt may not be the relevant divalent metal ion cofactor for MetAP-2 in cells and may explain the observed absence of cell-based activity using potent triazole inhibitors of cobalt-activated MetAP-2.

A Vascular Endothelial Growth Factor Receptor-2 Kinase Inhibitor Potentiates the Activity of the Conventional Chemotherapeutic Agents Paclitaxel and Doxorubicin in Tumor Xenograft Models

Inhibition of angiogenesis may have wide use in the treatment of cancer; however, this approach alone will not cause tumor regression but may only slow the growth of solid tumors. The clinical potential of antiangiogenic agents may be increased by combining them with conventional chemotherapeutics. 4-[4-(1-Amino-1-methylethyl)phenyl]-2-[4-(2-morpholin-4-yl-ethyl)phenylamino]pyrimidine-5-carbonitrile (JNJ-17029259) represents a novel structural class of 5-cyanopyrimidines that are orally available, selective, nanomolar inhibitors of the vascular endothelial growth factor receptor-2 (VEGF-R2) and other tyrosine kinases involved in angiogenesis, such as platelet-derived growth factor receptor, fibroblast growth factor receptor, VEGF-R1, and VEGF-R3, but have little activity on other kinase families. At nanomolar levels, JNJ-17029259 blocks VEGF-stimulated mitogen-activated protein kinase signaling, proliferation/migration, and VEGF-R2 phosphorylation in human endothelial cells; inhibits the formation of vascular sprouting in the rat aortic ring model of angiogenesis; and interferes with the development of new veins and arteries in the chorioallantoic membrane assay. At higher concentrations of 1 to 3 microM, this compound shows antiproliferative activity on cells that may contribute to its antitumor effects. JNJ-17029259 delays the growth of a wide range of human tumor xenografts in nude mice when administered orally as single-agent therapy. Histological examination revealed that the tumors have evidence of reduced vascularity after treatment. In addition, JNJ-17029259 enhances the effects of the conventional chemotherapeutic drugs doxorubicin and paclitaxel in xenograft models when administered orally in combination therapy. An orally available angiogenesis inhibitor that can be used in conjunction with standard chemotherapeutic agents to augment their activity may have therapeutic benefit in stopping the progression of cancer and preventing metastasis.

Synthesis and anti-angiogenic activity of 6-(1,2,4-thiadiazol-5-yl)-3-amino pyridazine derivatives

General screening for inhibitors of microvessel growth in vitro in the rat aortic ring assay led to the discovery of a novel series of thiadiazole pyridazine compounds with potential anti-angiogenic activity. Chemical optimization produced orally active compounds with potent in vitro and in vivo anti-angiogenesis and anti-tumor activities.