ac-7700 and fosbretabulin

Angiogenesis has an essential role in promoting and supporting tumor growth and it is an important therapeutic target. The tumor vascular network is the result of pro-angiogenic and inhibitory factors as well as of the interaction between endothelial cells and extracellular matrix. Different antiangiogenic therapeutics have been developed to improve tumor control through vascular-targeting agents (VTA). VTAs can be divided into two groups: antiangiogenic agents and vascular-disrupting agents (VDAs). VTAs inhibit specific factors required to induce and direct the angiogenic process, with major activity against small tumor masses and at the tumor periphery, encompassing monoclonal antibodies and small molecules inhibitors of the tyrosine kinase domain of the VEGF receptor. VDAs specifically target and destroy well-established tumor vessels with ischemia and destruction of large masses with central hemorrhagic necrosis and survival of a thin peripheral tumor layer. VDAs can be divided into biologics, such as ligand-based, and small-molecule agents; this second group includes small-molecule VDAs like flavonoids, such as 5,6-dimethylxanthenone-4-acetic acid (DMXAA), and microtubule-destabilizing agents. In this review we will discuss the mechanism of action, as well as the preclinical and clinical results, of one of the most promising antitubulin agents: the combretastatin A4-phosphate derivative, AVE8062A.

Topics: Angiogenesis Inhibitors; Animals; Antineoplastic Agents; Clinical Trials as Topic; Drug Evaluation, Preclinical; Humans; Neoplasms; Neovascularization, Pathologic; Serine; Stilbenes; Tubulin

Despite extensive research efforts, effective therapies for refractive cancers have not yet been established, and development of successful treatment strategies remains the most important task in the field of oncology. We recently showed that AVE8062 (formerly AC7700), a derivative of combretastatin A-4, achieved irreversible stasis of tumor blood flow (TBF), thereby causing necrosis of tumor tissue by halting the supply of nutrients. Such effects were unrelated to cancer type. In this review, we summarize our experiments on antivascular and antitumor effects by AVE8062. We maintain that such starvation tactics against solid tumors constitute a new therapeutic strategy for all solid tumors, including refractory cancers.

Topics: Animals; Antineoplastic Agents; Microcirculation; Neoplasms; Rats; Regional Blood Flow; Serine; Stilbenes

Several derivatives of combretastatin have been prepared bearing a cyclopropyl unit instead of the natural occurring cis-double bond. Final products and synthetic intermediates were evaluated for their cytotoxic properties in two human cancer cell lines.

Topics: Antineoplastic Agents; Cell Line, Tumor; Cyclopropanes; Humans; Stilbenes; Tubulin Modulators

AVE8062, a derivative of combretastatin A-4, has a strong stanching effect on tumour blood flow (TBF), which leads to complete blockage of nutrient supply to solid tumours and their necrosis. Previously, we reported that TBF stasis is due to increased arteriolar resistance caused by AVE8062 and a lasting decrease in perfusion pressure in tumour-feeding vessels. Here, we measured changes in TBF in rat solid tumour LY80 during continuous administration of AVE8062-like epinephrine or four catecholamines that are unlike AVE8062 (norepinephrine, dopamine, methoxamine, and metaraminol) to the region of increased vascular resistance. Venous administration of 0.3 mg ml(-1) epinephrine caused TBF to fall immediately to near zero, where it remained throughout the administration period. With a 30-min drug administration, TBF began to recover immediately when drug administration halted. With a 60-min epinephrine administration, TBF recovered somewhat, but not to the previous level. With drug administration of 120 min, TBF did not recover during the subsequent 8 h. Likewise, 0.1 mg ml(-1) epinephrine produced irreversible occlusion after 120 min of administration. In contrast, 120 min of administration of the four other catecholamines resulted in no occlusion. Only the group given 0.3 mg ml(-1) epinephrine (not that given methoxamine) showed significantly greater necrosis than the control. We conclude that, for epinephrine to cause irreversible occlusion of these vessels, a marked decrease in perfusion pressure in tumour-feeding blood vessels is necessary and should be maintained for 2 h. This conclusion is consistent with the previously demonstrated mechanism of irreversible arteriole occlusion caused by AVE8062. AVE8062 and epinephrine appear to have the same mechanism of action regarding induction of tumour blood flow stasis.

Topics: Animals; Antineoplastic Agents, Phytogenic; Catecholamines; Epinephrine; Necrosis; Neoplasms, Experimental; Rats; Regional Blood Flow; Sarcoma; Serine; Soft Tissue Neoplasms; Stilbenes

AC-7700, a novel combretastatin A-4 derivative, suppresses the growth of solid tumors by inhibiting tumor perfusion. We evaluated the antitumor activity of AC-7700 on solid tumors in two experimental models, an advanced tumor model (murine colon 26 (c26) adenocarcinoma, colon 38 (c38) adenocarcinoma, MethA fibrosarcoma, Sarcoma 180 (S180), Lewis lung carcinoma (3LL), human LS180 adenocarcinoma) and an orthotopically transplanted tumor model (c26), compared with that of cisplatin (CDDP). The maximum tolerable dose (MTD) of CDDP suppressed early-stage c26 and c38 tumor growth when treatment was started after the tumor volume (TV) reached 0.2-0.5 cm3, but it showed reduced activity against the same tumors at an advanced growth stage when TV exceeded 2 cm3. At its MTD, AC-7700 was active against all tumors tested except 3LL in both early and advanced growth stages, reducing the tumor mass and having a curative effect in advanced c38 tumors. AC-7700 was also effective on orthotopically transplanted c26 tumors, showing a comparable activity to that on subcutaneous tumors. Unlike flavon acetic acid, which damages tumor vasculature by inducing endogenous tumor necrosis factor-alpha production, AC-7700 potently suppressed the growth of advanced c26 tumors in athymic as well as euthymic mice. These results suggest that AC-7700 is a novel antivascular agent that may have potent activity against advanced-stage cancer in the clinical setting.

Topics: Animals; Antineoplastic Agents; Disease Models, Animal; Drug Screening Assays, Antitumor; Female; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Mice, Inbred ICR; Neoplasm Transplantation; Neoplasms, Experimental; Serine; Stilbenes; Survival Analysis; Transplantation, Heterologous; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

The relation between tumor tissue blood flow (tBF) reduction and antitumor effects was investigated. Changes in tBF of normal tissues (liver, kidney cortex, bone marrow and brain cortex) and tumors (Yoshida sarcoma subline, LY80 and Sato lung carcinoma, SLC) due to i.v. administration of AC7700 (1, 3, 10 mg/kg), one of the combretastatin A-4 derivatives, were measured with the hydrogen clearance method. The change in blood flow in tumor microfoci was also observed directly using a rat transparent chamber. Chemotherapy against the solid tumors (LY80, SLC) was performed by administering AC7700 7 times at intervals of 3 days and the effect on the tumor growth, the histological effect, the effect on lymph node metastasis and the survival rate were investigated. Tumor tBF showed a dose-dependent response to AC7700. Although tumor tBF decreased markedly at a dose of 1 mg/kg, it tended to recover partly within several hours. At 10 mg/kg, however, tumor tBF completely stopped within approximately 30 min and never recovered in many regions. The irreversible stoppage of tumor tBF was observed in large s.c. tumors and in microfoci as well. On the other hand, in normal tissues, tBF changes due to AC7700 were not uniform. In the liver, although tBF decreased by approximately 50% at 10 mg/kg AC7700, it recovered within 8 h. In the brain, although the mean maximum reduction was 35%, the blood flow recovered to the original level within 24 h. The blood flow in the kidney cortex did not change at all. In the bone marrow, tBF decreased by approximately 80%. Generally, the blood flow reduction in normal tissues tended to be reversible. The effect on tumor growth and the histological effect were also dependent on the dose of AC7700. The tumor growth was markedly inhibited by 10 mg/ kg AC7700 and extensive necrosis was induced. Lymph node metastases were significantly inhibited and survival was prolonged significantly. In the control group, all 8 SLC tumor-bearing rats died of cancer, the presence of which was verified by gross and microscopic evaluation, within 45 days after tumor implantation. On the other hand, in the treated group, 2 of 8 rats recovered completely and survived. No obvious side effects such as body weight loss, anemia or diarrhea were observed at the dose used in this experiment. From these results, we conclude that strong antitumor effects are obtained by stopping tumor tBF irreversibly and by shutting off the nutritional supply into tumor tissue. AC7700

Topics: Animals; Antineoplastic Agents; Blood Pressure; Body Weight; Disease Models, Animal; Drug Screening Assays, Antitumor; Lymphatic Metastasis; Male; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Regional Blood Flow; Serine; Stilbenes; Survival Rate