Investigational agents in development for the treatment of ovarian cancer

Although significant success has been achieved in the treatment of advanced and recurrent ovarian cancer, there is clearly room for improvement. The use of targeted agents in this patient population has the promise to provide improved survival and quality of life. There are a myriad of relevant pathways under exploration in all settings of ovarian cancer. Clinical trial data are accumulating for antiangiogenic therapy, including vascular endothelial growth factor (VEGF)-specific inhibitors and multiple angiogenic signaling target inhibitors, as well as poly-ADP-ribose polymerase (PARP) inhibitors. Other types of tumorigenic pathway inhibitors, including those that target phosphatidylinositol-3-kinase (PI3K), mammalian target of rapamycin (mTOR), protein kinase B (AKT), Src, folate receptor alpha, and insulin-like growth factor-1 receptor (IGF-1R) pathways are in earlier phases of development for ovarian cancer. Attempts to target the epidermal growth factor receptor (EGFR) of ovarian tumors have been met with limited success; however, newer agents that inhibit this pathway show promise. Finally, with recognition of the role of Wee-1 in p53-deficient tumors, an inhibitor of this tyrosine kinase is being evaluated in recurrent ovarian cancer. The logistical challenge is to determine the optimal timing and proper combinations of novel agents independently as well as concomitantly with conventional chemotherapeutics. Reported results have been modest; however, our growing understanding of these pathways will be potentially reflected in greater impact on response and survival.

Combined targeting of endothelin A receptor and epidermal growth factor receptor in ovarian cancer shows enhanced antitumor activity

Ovarian carcinomas overexpress endothelin A receptors (ET(A)R) and epidermal growth factor (EGF) receptor (EGFR). In these cells, endothelin-1 (ET-1) triggers mitogenic and invasive signaling pathways that are in part mediated by EGFR transactivation. Combined targeting of ET(A)R, by the specific ET(A)R antagonist ZD4054, and of EGFR by the EGFR inhibitor gefitinib (IRESSA), may offer improvements in ovarian carcinoma treatment. In HEY and OVCA 433 ovarian carcinoma cells, ET-1 or EGF induced rapid activation of EGFR, p42/44 mitogen-activated protein kinase (MAPK), and AKT. ZD4054 was able to reduce the ET-1-induced EGFR transactivation. Gefitinib significantly inhibited EGF- and ET-1-induced EGFR phosphorylation, but incompletely reduced the ET-1-induced activation of downstream targets. ZD4054 plus gefitinib resulted in a greater inhibition of EGFR, MAPK, and AKT phosphorylation, indicating the critical role of these interconnected signaling proteins. ZD4054 effectively inhibited cell proliferation, invasiveness, and vascular endothelial growth factor (VEGF) secretion. Concomitantly, ZD4054 enhanced apoptosis and E-cadherin promoter activity and expression. In both cell lines, the drug combination resulted in a significant decrease in cell proliferation (65%), invasion (52%), and VEGF production (50%), accompanied by a 2-fold increase in apoptosis. The coadministration of ZD4054 enhanced the efficacy of gefitinib leading to partial (82%) or complete tumor regression on HEY ovarian carcinoma xenografts. Antitumor effects were paralleled by biochemical and immunohistologic evidence of decreased vascularization, Ki-67, matrix metalloproteinase-2 (MMP-2), VEGF, MAPK and EGFR, and enhanced E-cadherin expression. The cross-signaling between the EGFR/ET(A)R pathways provides a rationale to combine EGFR inhibitors with ET(A)R antagonists, identifying new effective therapeutic opportunities for ovarian cancer.