Combination therapy of zibotentan with cisplatinum and paclitaxel is an effective regimen for epithelial ovarian cancer

In human ovarian carcinoma, the endothelin-1 (ET-1) / endothelin A receptor (ET_AR) axis is overexpressed, correlating with tumor grade. Moreover, ET_AR activation by ET-1 affects cell proliferation, survival, angiogenesis, and invasion. ET_AR blockade with zibotentan (ZD4054), a specific ET_AR antagonist, significantly inhibits ovarian cancer growth in vitro and in vivo, underscoring the relevance of this pathway as a target for cancer therapy. Since clinical trial results have defined the combination of platinum and taxane as the standard of care in the management of ovarian cancer, here we explored the therapeutic efficacy of the integration of zibotentan with cytotoxic drugs having different modes of action. We found that the combination of zibotentan with cisplatinum as well as zibotentan with paclitaxel was more effective at inhibiting ovarian cancer HEY cell proliferation induced by endogenous ET-1 than were the single agents alone. However, a significantly enhanced efficacy was observed when we combined zibotentan, cisplatinum, and paclitaxel. Accordingly, in HEY xenografts the coadministration of zibotentan with cisplatinum enhanced the efficacy of the cytotoxic drug alone in controlling tumor growth, associated with reduction in proliferation index and microvessel density. Remarkably, the combination of zibotentan with both cisplatinum and paclitaxel was very effective in inhibiting tumor growth, neovascularization, and cell proliferation, representing a preclinical endpoint to guide combination therapy in clinical trials.