The parent murine antibody of bevacizumab, A.4.6.1, demonstrated promising antitumor activity in a subcutaneous SKOV-3 human ovarian cancer xenograft model. Interestingly, in the intraperitoneal model of the same cell line, A.4.6.1 produced only partial inhibition of tumor growth, but was associated with almost complete inhibition of ascites production. These data provided the rationale for evaluation of bevacizumab in ovarian cancer. A Gynecologic Oncology Group (GOG) phase II study of bevacizumab monotherapy is ongoing, and a second trial will examine the combination of bevacizumab with daily, low-dose, oral cyclophosphamide, using metronomic dosing in the hope that 'less is more'.