96 POSTER Potential importance of the ceramide pathway in the action of the tumour vascular disrupting agent ASA404 (DMXAA, 5,6-dimethylxanthenone-4-acetic acid)

Temporal aspects of the action of ASA404 (vadimezan; DMXAA)

IMPORTANCE OF THE FIELD

Tumor vascular disrupting agents (tumor VDAs) act by selective induction of tumor vascular failure. While their action is distinct from that of antiangiogenic agents, their clinical potential is likely to reside in improving the efficacy of combination therapy.

AREAS COVERED IN THIS REVIEW

This review describes the preclinical development, clinical trial and mode of action of ASA404, a flavonoid class tumor VDA. This class has a unique dual action, simultaneously disrupting vascular endothelial function and stimulating innate tumor immunity. This review covers the early development of ASA404, through to Phase III trial.

WHAT THE READER WILL GAIN

The reader will gain insight into the sequence of ASA404-induced changes in tumor tissue. Early events include increased vascular permeability, increased endothelial apoptosis and decreased blood flow, while later effects include the induction of serotonin, tumor necrosis factor, other cytokines and chemokines, and nitric oxide. This cascade of events induces sustained reduction of tumor blood flow, induction of tumor hypoxia and increased inflammatory responses. The reader will also gain an appreciation of how the potentiation of radiation and chemotherapeutic effects by ASA404 in murine tumors shaped the development of combination clinical trials.

TAKE HOME MESSAGE

Although there are species differences in ASA404 activity, many features of its action in mice translate to human studies. The future of ASA404 as an effective clinical agent will rely on the development of an appreciation of its ability to optimize the complex interaction between tumor vasculature and tumor immunity during therapy.

ASA404: a tumor vascular-disrupting agent with broad potential for cancer therapy

ASA404 (5,6-dimethylxanthenone-4-acetic acid) was developed as an analogue of flavone acetic acid and found to induce hemorrhagic necrosis of experimental tumors. ASA404 simultaneously targets at least two cell types - vascular endothelial cells and macrophages - within the tumor microenvironment. In murine tumors, ASA404 induces coordinated decreases in tumor blood flow, increases in vascular permeability and increases in vascular endothelial apoptosis, all occurring within 1 h of administration. Over a slightly longer time scale, ASA404 induces an increase in tumor concentrations of TNF and a number of other cytokines. Phase I clinical trials confirmed its vascular effects in humans and Phase II trials demonstrated its activity in combination with the cytotoxic agents carboplatin and paclitaxel. While the molecular target of its action is not yet identified, current results suggest that ASA404 has the potential to augment the antitumor effects of other agents in cancer treatment. Studies of changes in tumor tissue following treatment with ASA404 either alone or combined and other agents will provide new insights into the dynamics of the tumor microenvironment.