Anti-angiogenic agents in ovarian cancer: past, present, and future

Angiogenesis plays a pivotal role in normal ovarian physiology as well as in the progression of ovarian cancer through ascites formation and metastatic spread. Bevacizumab (Avastin (R), Genentech; South San Francisco, CA, USA), a humanized antivascular endothelial growth factor (VEGF) monoclonal antibody, is the most widely studied anti-angiogenesis agent both across tumor types and specifically in epithelial ovarian cancer. In 2005, single-agent bevacizumab at 15 mg/kg (IV) every 3 weeks was first reported to be active in a case of recurrent high-grade serous ovarian cancer after failing 11th line cytotoxic treatment. Since then, many case series, phase II and phase III trials have confirmed these results leading to regulatory approval in most countries including the US Food and Drug Administration in 2014. Guidelines now give clear recommendations as to when and how bevacizumab should be integrated into the ovarian cancer treatment paradigm. Other anti-VEGF agents such as the VEGF receptor (VEGFR) tyrosine kinase inhibitors have not shown increased activity or reduced toxicity relative to bevacizumab. However, anti-angiogenics other than anti-VEGF/VEGFR agents such as those targeting Angiopoietin-1 and -2 are in development as well as novel combinations with vascular disrupting agents (VDAs), PARP inhibitors and immune checkpoint inhibitors. Clearly, the benefits of anti-angiogenic agents such as bevacizumab must be carefully weighed against the cost and associated toxicities. Although almost all patients with ovarian cancer will receive an anti-angiogenic compound, cures are not increased. Predictive biomarkers are an urgent unmet need.