Angiogenesis: A promising therapeutic target for ovarian cancer

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1 Critical Reviews in Oncology/Hematology 84 (2012) Angiogenesis: A promising therapeutic target for ovarian cancer A. Bamias a,, S. Pignata b, E. Pujade-Lauraine c a Dept of Clinical Therapeutics, Medical School, University of Athens, Athens, Greece b National Cancer Institute of Naples, Naples, Italy c Département d Oncologie Médicale, Université Paris Descartes, Hôpital Hôtel-Dieu, Paris, France Accepted 10 April 2012 Contents 1. Introduction Rationale for targeting angiogenesis in ovarian cancer Clinical experience with inhibitors of angiogenic factors Selective VEGF/VEGFR inhibition Bevacizumab VEGF Trap IMC-1121B Multiple tyrosine kinase-receptor inhibition Pazopanib Cediranib BIBF Sunitinib Sorafenib Angiopoietin inhibition Conclusions and future directions Conflict of interest statement References Biographies Abstract Ovarian cancer is the leading cause of death from gynecological cancers. Primary treatment of advanced ovarian cancer (FIGO stages III and IV) until recently consisted of cytoreductive surgery and paclitaxel/carboplatin chemotherapy. The results of two randomized studies, showing prolongation of progression-free survival (PFS) by the addition of the anti-vegf monoclonal antibody, bevacizumab, led to the approval of this agent for first-line treatment of this disease and indicate that angiogenesis is a promising therapeutic target. Angiogenesis is essential for oncogenesis but also the viability and expansion of ovarian cancer. Specifically, VEGF is involved in the formation of ascites and has a direct effect on ascites tumor cells as well as an immunosuppressive function. Apart from VEGF, PDGF, FGF and angiopoietins present a therapeutic interest. We are reviewing the results of published clinical studies using anti-angiogenic factors in advanced ovarian cancer Published by Elsevier Ireland Ltd. Keywords: Ovarian cancer; Angiogenesis; VEGF; Bevacizumab; Pazopanib; Cediranib; AMG386 Corresponding author at: Alexandra Hospital, Oncology Unit (5th Floor), 80 Vas. Sofias Ave., Athens, Greece. Tel.: ; fax: address: abamias@med.uoa.gr (A. Bamias). 1. Introduction Cancer is one of the leading causes of death in the developed world outnumbering even heart disease in the United /$ see front matter 2012 Published by Elsevier Ireland Ltd.

2 A. Bamias et al. / Critical Reviews in Oncology/Hematology 84 (2012) States [1]. In turn, ovarian cancer remains the leading cause of death among gynecological malignancies and is the fourth most common cause of cancer related death among women. Epithelial ovarian cancer is the main type of the disease accounting for more than 90% of all malignant ovarian tumors. According to the initial FIGO stage, the prognosis of ovarian cancer varies; a 5-year survival reaches 90% when the disease is confined within the ovary but it drops to below 50% for the cases that cancer has spread outside the pelvis. Ovarian cancer is usually diagnosed in advanced stages (FIGO stages III and IV), and prognosis is generally rather poor. Major established prognostic factors, apart from FIGO stage of the disease, include tumor grade, histologic subtype and the volume of disease remaining after cytoreductive surgery [2,3]. Current treatment of advanced ovarian carcinoma includes debulking and chemotherapy, mainly the combination of the use of paclitaxel and platinum agents. Most patients treated with the above combination initially respond to this treatment but the disease is more likely to relapse in about 70% of the cases [4]. Therefore, although median survival of these patients has been improved due to the advances both in surgery and chemotherapy, cure of advanced ovarian cancer remains exceptional. The addition of effective, nonplatinum cytotoxic agents to the paclitaxel/carboplatin combination in first-line has not produced any benefit. Traditional cytotoxic chemotherapy has been limited by drug resistance and lack of specificity to mechanisms of disease progression. There is, therefore, a need for novel therapies with different modes of action. New ways of treating the disease are currently being explored focusing on the biology of cancer [5] and more specifically within the ovarian tumor microenvironment. Therefore, clinical research has focused on molecular markers, which are related either to the behavior of the disease or the response to chemotherapy in order to define the outcome in these patients and establish furthermore potential targets for therapy. 2. Rationale for targeting angiogenesis in ovarian cancer Angiogenesis is a critical function for the expansion of a tumor but also for its metastatic potential and it is influenced by the tumor microenvironment [6]. Small incipient tumor masses will not grow beyond the size of approximately 1 2 mm unless they can develop a blood vessel supply to provide the necessary oxygen and nutrients to allow progressive expansion of tumor mass. During the course of tumor development, cells within some of the small microscopic occult tumors start to release soluble proangiogenic mediators, which diffuse out from the tumor cell population, bind to adjacent endothelial cells of mature blood vessels, and trigger a form of angiogenesis called sprouting angiogenesis [7], leading to the development of new blood vessel capillaries. Those capillaries then infiltrate the microscopic tumor mass and set in motion the possibility of progressive expansion of tumor mass and hematogenous metastatic spread. Several reports have demonstrated a role for angiogenesis in the pathophysiology of gynecologic cancers, including ovarian [8]. Vascular endothelial growth factor (VEGF) holds a pivotal role in the angiogenic process, mainly by regulating new blood vessel growth and promoting survival of immature vasculature [9]. Many environmental factors, including hypoxia and low ph, hormones (e.g., progesterone, estrogen), growth factors (e.g., endothelial growth factor [EGF], transforming growth factor-beta [TGF- ], basic fibroblast growth factor [bfgf], platelet-derived growth factor [PDGF], insulinlike growth factor [IGF]-1) and cytokines (e.g., interleukin [IL]1, IL-6) stimulate VEGF expression. In addition to exogenous factors, many tumorigenic mutations lead to VEGF upregulation. These can include mutations in cellular oncogenes, such as src, ras, and bcr-abl. and in tumor suppressor genes such as p53, p73, and vhl [10]. Five members of the VEGF family of ligands have been described so far [11]. VEGF-A seems to be the most important for angiogenesis and it will be referred to as VEGF throughout. VEGF exerts its effects via its receptor, VEGFR, mainly VEGFR2 [9,12]. Various factors, such as Ins-P3, PI3-kinase, MAP kinase and JAK-STAT have been implicated in VEGF signal transduction [13] (Fig. 1). VEGF is produced by cancer cells and is related to the invasive and metastatic potential of human tumors, including ovarian cancer [14 16]. Up to now, these functions have been attributed solely to its angiogenic properties. Recently, it has been suggested that VEGF also exerts an immunosuppressive effect in cancer [17] as it was correlated with low levels of IL12, inhibition of dendritic cell maturation, low numbers of NK-T cells and upregulation of Tregs [18 22]. We have recently shown that a suppressive effect of VEGF on T lymphocytes is exerted through VEGFR2, which is expressed by activated lymphocytes [23]. Finally, VEGF may promote tumor growth by a direct action on its receptor, which is expressed by tumor cells themselves [13,24,25]. This has been shown in experimental models for shed ovarian cancer cells in ascites [26], which have been implicated in the development of peritoneal metastases, the dominant clinical feature of this cancer. In ovarian cancer, tumor lesions are removed or significantly reduced by surgery and tumor regrowth crucially involves neo-angiogenesis, which makes this process more relevant than in other tumors. Its significance in ovarian cancer has been well established and a number of angiogenic factors have been identified. VEGF holds a very important role in the oncogenesis as well as progression and prognosis in ovarian cancer [13,27]. It is selectively accumulated in ascites and occurs in advanced stages of the disease, at much higher levels than those observed in the blood of the same patients as well as in ascites caused by nonmalignant conditions, such as liver cirrhosis [28]. These data indicate that VEGF is associated with the most characteristic feature

3 316 A. Bamias et al. / Critical Reviews in Oncology/Hematology 84 (2012) Fig. 1. VEGF exerts its signaling effect via its receptor VEGFR. VEGF, mainly the VGEFA isoform, exerts its effects via binding its receptor VEGFR (mainly VEGFR2). Bevacizumab blocks the pathway by inhibiting the binding of VEGF to VEGFR ID: intracellular domain, ED: extracellular domain, TD: transmembrane domain. of ovarian cancer, i.e. metastases in the peritoneum, which also represents the most usual site of treatment failure. It may, therefore, be an important target for anti-cancer therapy. This hypothesis is further strengthened by the prognostic significance of serum or ascites levels of VEGF in ovarian cancer [27,29 31]. Microvessel density has also been shown to be associated with prognosis in ovarian cancer [32]. Finally, in recent studies serum Fas protein (sfas) levels and serum VEGF levels have been found to be increased in ovarian cancer patients and correlated with a short duration relapse free period [33]. Several experimental studies have suggested that anti- VEGF/VEGFR therapies may be of value in ovarian carcinoma. Gene therapy with soluble VEGFR 1 3 or the administration of an anti-vegf monoclonal antibody, A resulted in significant reduction of microvessel density and intraperitoneal tumors in mouse models [34,35]. Theoretically, anti-vegf therapy may enhance the efficacy of chemotherapy. The mechanisms of action of these two modalities are independent and, therefore, potentially complementary to each other. This is particularly relevant in advanced ovarian cancer, where chemotherapy represents the main treatment modality. The presence of anti-angiogenic agents during the break period between each successive cycle of chemotherapy might slow down tumor repopulation by inhibiting angiogenesis, thus reversing resistance to chemotherapy. They may also improve tumor-cell kill, possibly by improving endothelial-cell kill as well. It has also been proposed that anti-vegf therapy may disrupt the autocrine VEGF/VEGFR loop, leading to increased susceptibility to apoptosis [36]. Examples of enhanced efficacy of chemotherapy by the addition of bevacizumab, an anti- VEGF monoclonal antibody, have been recently reported in the setting of first-line colorectal cancer, second-line colorectal cancer, first-line non-small-cell lung cancer, first-line metastatic breast cancer, and most recently, first-line ovarian cancer [37 41]. Apart from VEGF other angiogenesis-related factors also represent promising therapeutic targets in cancer therapy. Platelet-derived growth factor (PDGF) is essential to pericyte recruitment, which is a critical component of maturing blood vessels. Preclinical studies have shown that PDGF receptor (PDGFR) activation leads to increased angiogenesis [42]. More importantly, interactions with VEGF have been described, either as common PDGF/VEGF signaling [43] or as PDGF pathway activation in resistance to VEGF inhibition [44]. This evidence supports the rationale for combining PDGF and VEGF inhibition. Preclinical studies have shown reduction of both vascularity and pericytes when such as approach was used in mouse tumor models [45]. The importance of PDGF is also underlined by association of its expression with prognosis in ovarian cancer patients [46]. Similarly to PDGF, fibroblast growth factor (FGF) family has also been implicated in resistance to VEGF pathway inhibitors [47]. FGF is a well-recognized activator of angiogenesis and has been found to be elevated in ovarian cancer compared to normal ovary [13]. Angiopoietin (Ang) 1 and 2 are key endothelial cellselective growth factors. Ang1 binding to Tie2 receptor promotes blood vessel stability by enhancing interactions between perivascular cells and endothelium, enhancing endothelial cell survival and leading to a more stable vasculature with decreased permeability [48]. Ang2 interrupts Ang1-mediated vessel normalization, resulting in impaired pericyte coverage, vessel destabilization, and increased vascular permeability, conditions conducive for sprouting angiogenesis and is upregulated at sites of angiogenesis [49]. Recent experimental studies with Ang1- or Ang2- specific agents suggest that Ang2 may be the more important target for inhibiting angiogenesis. The over-expression of

4 A. Bamias et al. / Critical Reviews in Oncology/Hematology 84 (2012) Table 1 Major types of VEGF-dependent angiogenesis inhibitors, which have been studied in ovarian cancer. Type Drug Target Monoclonal Bevacizumab Circulating VEGF antibodies IMC-1121B VEGFR2 Soluble VEGFR VEGF Trap Circulating VEGF decoy receptors Tyrosine kinase inhibitors (TKIs) Pazopanib VEGFR, PDGFR, c-kit, FGFR Cediranib VEGFR, PDGFR, c-kit BIBF 1120 VEGFR, PDGFR, FGFR Sunitinib VEGFR, PDGFR Sorafenib VEGFR, PDGFR, Raf, c-kit Table 2 Single-agent bevacizumab in EOC/PPC: phase II trials. GOG 170-D AVF 2949 Pts platinum DFI < 6 mos, % Previous regimens (1/2/3/4), % 34/66/0 0/52/48 GOG/ECOG PS (0/1), % 73/27 59/41 RR, n (%) 13 (21) 7 (16) 6-month PFS, % Median OS (months) G3 GI perforation 0 5 (11%) G3 arterial TE 0 3 (8%) G3 HTN 6 (10%) 6 (14%) G3 CNS 0 1 G3 proteinuria 1 0 Ang2 resulted in enhanced tumor angiogenesis and growth [50]. Importantly, selective antagonists of Ang2 (peptibody and antibody) inhibited tumor growth in murine xenograft models, suggesting a possible therapeutic benefit in human cancers [51]. Nevertheless, dual Ang1/2 blockade may offer advantages in some cases [52]. For example, stabilizing tumor vasculature by promoting Tie2 signaling (e.g., through Ang2 blockade) may render established vasculature more resistant to antiangiogenic therapy. Hence, simultaneous Tie2 inhibition may promote vascular regression. The above data suggest that angiogenesis represents a promising target for the treatment of ovarian cancer. 3. Clinical experience with inhibitors of angiogenic factors Several discoveries made since the 1990s have led to the development of drugs targeting the angiogenesis and especially VEGF pathway. There are now many drugs, falling into a number of different classes (Table 1), some of which are approved for clinical use. The major successes have been with small-molecule tyrosine kinase inhibitors (TKIs) of the receptor and with antibodies that target the ligand. Bevacizumab is an example of a drug that targets circulating VEGF. Soluble VEGFR decoy receptors, such as VEGF Trap or aflibercept, also target circulating VEGF. Antibodies have also been developed to target VEGFR-2 and VEGFR-1. The TKIs target multiple tyrosine kinases, VEGFRs, and depending on the drug, a number of other receptors as well. This review is focusing on those which have been studied in ovarian cancer Selective VEGF/VEGFR inhibition Bevacizumab Bevacizumab is a recombinant humanized monoclonal antibody of the IgG1 isotype that binds to all isoforms of VEGF (VEGF-A) with high specificity and affinity resulting in potent VEGF-neutralizing activity. Once bound, bevacizumab prevents VEGF interactions with its cognate receptors, VEGFR-1 (Flt-1) and VEGFR-2 (KDR), on the surface of endothelial cells, inhibiting VEGF-stimulated downstream signaling events [53]. The estimated half-life of bevacizumab is about 20 days (with a range of days) Phase II studies Single agent. Following anecdotal reports of single-agent bevacizumab efficacy in heavily pre-treated patients with recurrent ovarian cancer [54], two phase II studies in platinum-pretreated patients were initiated in USA, a GOG and an industry-sponsored trial, which have been reported in full (Table 2) [55,56]. Bevacizumab was used at 15 mg/kg iv every 3 weeks in both studies and both studies showed that this agent was effective in this population. Specifically for the GOG study, the median PFS was 4.7 months, which was statistically superior (P < ) to the median PFS of 1.8 months for a historical cohort of more than 300 similar patients entered onto previous GOG phase II trials of inactive cytotoxic agents. Although the two trials were similar fundamentally in design and treatment regimen, differences in eligibility resulted in differences both in efficacy and safety. The AVF 2949 trial enrolled only patients considered either primarily or secondarily platinum resistant and who had received two or three previous cytotoxic regimens, while the GOG study also included platinum sensitive patients and only one or two prior regimes were allowed. As shown in Table 2, these differences in eligibility ultimately translated into a higher level of platinum resistance, a greater number of prior regimens and a slightly worse performance status profile in AVF 2949 compared with GOG 170-D. With regard to toxicity, there appeared to be a greater number of serious adverse events in AVF 2949, including GI perforation and ATEs. This trial was terminated prematurely because of five GI perforations (11%) reported in the first 44 patients enrolled. GI perforation is a rare but well established complication in ovarian cancer with a rate of 5.2% in 308 patients treated on reported trials [57]. In the AVF 2949 trial, all GI perforations occurred in patients who received three (vs. two) prior regimens, suggesting that the risk of this complication might be related to degree of prior therapy. Other potential risk factors included intestinal

5 318 A. Bamias et al. / Critical Reviews in Oncology/Hematology 84 (2012) obstruction or bowel wall involvement by tumor based on imaging, although the associations of these variables to the events were not statistically significant Combination with chemotherapy. The rationale for combining anti-angiogenic therapies with chemotherapy has been previously described. In addition to the potential synergy, which has been discussed in Section 1, the non-overlapping toxicities also make their combination attractive. This is particularly relevant in a chemosensitive neoplasm, such as ovarian carcinoma. In first-line therapy, two studies have proved the feasibility of adding bevacizumab at 15 mg/kg to the combination of platinum plus taxane. In one trial bevacizumab was combined with the traditional carboplatin/paclitaxel doublet, followed by bevacizumab consolidation for 1 year [58]. The overall response rate was 76% and median OS had not been reached. In the other study bevacizumab was combined with the less conventional oxaliplatin and docetaxel therapy [59]. The overall response rate was 62% and 1-year PFS was 70%. Bevacizumab at 15 mg/kg/3 weeks iv, has also been used in combination with iv/intraperitoneal chemotherapy [60]. Although the cisplatin dose was lower than that used in the GOG-172 study, median PFS was comparable between the two studies, while treatment was better tolerated with 73% of patients completing 6 cycles of iv/ip therapy, compared to 42% in the GOG-172 study. Nevertheless, one patient died due to rectosigmoid anastomotic dehiscence, raising concerns about the GI complications of this approach. The feasibility of combining bevacizumab with carboplatin and dose-dense paclitaxel is currently being investigated in the OCTAVIA study (NCT ). In this single arm study patients receive weekly cycles of bevacizumab (7.5 mg/kg iv on day 1 of each cycle), paclitaxel (80 mg/m 2 iv on days 1, 8 and 15 of each cycle) and carboplatin (iv to an AUC of 6 on day 1 of each cycle). Following combination chemotherapy, bevacizumab may continue to be given as monotherapy. In a preliminary report of 189 cases the feasibility of this combination was confirmed [61]. These results should be viewed in the context of the recently reported superiority of the dose-dense administration of paclitaxel compared to the traditional 3-weekly in Japanese patients [62]. In relapsed disease, bevacizumab has been combined with oral metronomic cyclophosphamide [63], a nanoparticle albumin-bound formulation of paclitaxel (nab-paclitaxel) [64] and oxaliplatin/gemcitabine [65]. Bevacizumab was used at a dose of 10 mg/kg in all studies, which showed that these combinations are feasible with encouraging RRs and OS Phase III studies First-line. Two phase III randomized trials have been recently reported. In both studies bevacizumab was added to the standard paclitaxel/carboplatin combination and was also continued as maintenance therapy after the completion of chemotherapy. The main details regarding the design, results and toxicity are shown in Table 3. In GOG 218 (NCT ) the 3 treatment arms were placebo plus chemotherapy followed by placebo maintenance, bevacizumab plus chemotherapy followed by placebo maintenance, and bevacizumab plus chemotherapy followed by bevacizumab maintenance. FIGO stages III with macroscopic residual disease and stage IV were included. Although overall survival was originally selected as the primary endpoint, this was changed to PFS to accord with international consensus as a more appropriate endpoint for frontline phase III trials in this patient population. Recently presented results [66] indicate that patients who received bevacizumab plus chemotherapy with maintenance bevacizumab had longer PFS than patients who received chemotherapy alone (median PFS, 14.1 vs months; hazard ratio [HR], 0.717; 95% confidence interval [CI], ; P < ) after a median follow up of 17 months. However, no significant difference in PFS was reported between patients who received bevacizumab plus chemotherapy with maintenance placebo and those who received chemotherapy alone (median PFS, 11.2 vs months; HR, 0.908; 95% CI, ; P = 0.08). An updated analysis of data as of August 26, 2011 showed that the hazard of progression remained significantly decreased with bevacizumab-throughout vs. control therapy (HR, 0.770; 95% CI, ). In a pre-specified separate PFS analysis requested by regulatory agencies which censored CA-125-based progression at the date of last radiographic imaging before, the median PFS was 12.0 vs months for the bevacizumab maintenance group (HR: 0.645). There was no statistically significant difference in OS but this analysis was limited due to a 24% death rate at the time of data collection and was confounded by crossover to bevacizumab. At the updated analysis, the hazard of death was (95% CI, ) in the bevacizumab-initiation group and (95% CI, ) in the bevacizumab-throughout group. The addition of bevacizumab to CP appeared well tolerated, with no unexpected adverse events observed and discontinuation rates due to toxicity was similar across all arms. Hypertension a known side effect of bevacizumab was significantly more frequent in the bevacizumab arms compared with the control arm (P < 0.05) but the incidences of all other adverse events were similar (Table 4), including proteinuria, another bevacizumab-related side effect. Gastrointestinal perforation events did not markedly increase with use of bevacizumab ( % in the bevacizumab arms compared with 1.2% in the control arm), while bleeding complications were rare in all arms ( %). ICON-7 (NCT ) included patients with stage IC/IIA AND Grade III or clear-cell and debulked stage III/IV EOC, FTC, or PPC. Patients were randomized to paclitaxel/carboplatin with or without a lower bevacizumab dose (7.5 mg/kg) every 3 weeks for 6 cycles, followed by 12 courses of bevacizumab alone. This trial was initially reported after mature PFS analysis at a median follow up of 19 months, which showed a significant prolongation by the addition of

6 A. Bamias et al. / Critical Reviews in Oncology/Hematology 84 (2012) Table 3 First-line phase III trials of bevacizumab in ovarian cancer. Trial GOG 218 ICON 7 Placebo Yes No Doses Paclitaxel (P) 175 mg/m 2 Paclitaxel (P) 175 mg/m 2 Carboplatin (C) AUC 6 Carboplatin (C) AUC 5 or 6 Bevacizumab (B) 15 mg/kg Bevacizumab (B) 7.5 mg/kg Treatment duration 15 months 12 months Primary end point PFS PFS Arms CP (n = 625) CP + B (n = 625) CP + B B(n = 623) CP (n = 764) CP + B B(n = 764) Stage (%) I/IIA 10 9 II 9 9 III III IV IV Optimal debulking (%) Macro cm Median PFS (months) HR Ref. [66] Ref. [67] 0.87 (95% CI) ( ) ( ) ( ) P 0.16 < Median OS (months) NR NR HR Ref. [66] Ref. [67] 0.85 (95% CI) ( ) ( ) ( ) P Febrile neutropenia Hypertension Gr Gr Proteinuria Gr Gr 3 <1 <1 GI events Gr Gr Thromboembolism Gr Bleeding Gr Gr 3 <1 1 NR: not reported; PFS: progression-free survival; OS: overall survival; HR: hazard ratio; CI: confidence intervals. bevacizumab, thus meeting its primary endpoint [67]. Toxicity profile was similar to that of the GOG study. This trial has also been powered to detect significant differences in OS. The first report included only 34% of the required 715 events for final OS analysis, showing a non-significant numerical difference in favor of the experimental arm. An interim analysis, requested by regulatory authorities, after a median follow up of 28 months, including 53% of the required events confirmed the significant prolongation of PFS but still did not show a significant prolongation of median OS (Table 4). Nevertheless, a significant improvement from to 36.6 months in the high-risk group, defined as stage III suboptimal (residual disease > 1 cm) OR stage IV (HR 0.64 [ ], P = 0.002). The interaction between treatment arm and risk group was significant (P = 0.011). The final OS is due in The results of these studies led to the approval of bevacizumab EMEA for first-line treatment of FIGO stage III B, III C and IV EOC, FPC or PPC Relapsed disease. OCEANS (NCT ) [68] was a 2-arm, double-blind study, which was conducted in 484 women with platinum-sensitive recurrent EOC, PPC, or FTC after first-line chemotherapy and compared bevacizumab plus carboplatin/gemcitabine with carboplatin/gemcitabine alone. The primary endpoint was PFS. Carboplatin was given at AUC 4 day 1 and gemcitabine at 1000 mg/m 2 days 1 and 8 at 3-weekly cycles for 6 cycles. Bevacizumab was used at 15 mg/kg every 3 weeks until disease progression. Only one prior regimen was allowed and patients should have measurable disease. After a median follow up of 24 months, median PFS was significantly prolonged by the addition of bevacizumab by 4 months (8.4 [95% CI: ] vs [95% CI: ], HR: [95% CI: ], P < ). Median OS was 29.9 vs months, respectively (HR: [95% CI: ], P = 0.094) but only 29% of patients had had an event at the time of analysis. The safety profile was consistent with the first-line bevacizumab trials VEGF Trap VEGF Trap (aflibercept) is a recombinant protein consisting of domain 2 from VEGFR-1 fused to domain 3 from VEGFR-2, attached to the hinge region of the Fc(a)domain of human immunoglobulin (Ig) G1. VEGF Trap binds VEGF- A and neutralizes all VEGF-A isoforms. In a phase I study, which included patients with various solid tumors, it produced two confirmed and one unconfirmed partial responses in 14 patients with recurrent ovarian or peritoneal cancer [69]. A phase II randomized study in recurrent ovarian cancer has been reported in abstract form so far. In 162 women who had received 2 or 3 prior chemo regimens and their disease was resistant to platinum, topotecan and/or liposomal doxorubicin VEGF Trap was administered at 2 or 4 mg/kg. Both doses were well tolerated with hypertension (9%), proteinuria (4%), encephalopathy (2%) and renal failure (2%) being the Grade 3 4 toxicities. A 11% RR was reported [70]. Finally, in a phase I II study, 46 patients (33 platinum resistant, 13 platinum sensitive) with recurrent or persistent epithelial ovarian,

7 320 A. Bamias et al. / Critical Reviews in Oncology/Hematology 84 (2012) Table 4 Selected trials using VEGFR tyrosine kinase inhibitors (TKIs). TKI [ref] Patients Dose/schedule RR PFS a OS a Relevant Grade 3 4 side effects Pazopanib [73] N =36 CA125 relapse 1 2 prior regimes Cediranib [76,77] N =46 Recurrent 1 2 regimes for relapse N =49 Recurrent 1 regime for relapse BIBF 1120 [78] N =83 Recurrent, TFI 12 mos 2 3 prior regimes Sunitinib [80] N =30 Recurrent 1 2 prior regimes Sorafenib [82,83] N =71 Recurrent, TFI 12 mos 2 3 prior regimes N =19 Platinum-resistant 800 mg/d 31% (CA125) 6-mo: 17% NR Fatigue (11%), liver (11%), diarrhea (8%) 45 mg/d 17% 5.2 mos Mean: 16.2 Hypertension (46%), fatigue (24%), diarrhea (13%) 45 mg/d 18% (pls) 4% (plr) Chemo + BIBF mg bd Chemo + placebo 1st stage: 50 mg 4 2 2nd stage: 37.5 mg cont. NA RECIST: 3% CA125: 10% 4.1 mos 11.9 Hypertension (33%), fatigue (20%) 36-week 16.3% 5% HR: 0.84 (95% CI: ) Liver (51% vs. 7%), diarrhea (9% vs. 2%), hypertension (5% vs. 0%), fatigue (5% vs. 0%) 4.1 mos NR Fatigue (10%), skin (10%), bone marrow (13%) 400 mg bd 3% 2.1 mos 16.3 mos Skin (22%), metabolic (14%) Sorafenib: 200 d 1 7, or 200 mg d 1 5 or 400 mg bd d 1 5 Bevacizumab: 5 or 10 mg/kg/2 wks 42% NR NR Hypertension (30%), fatigue (10%) a When not specified represents median; NR: not reported; mo: month; pls: platinum-sensitive; plr: platinum-resistant; TFI: treatment-free interval; HR: hazard ratio; CI: confidence intervals. primary peritoneal, or fallopian tube carcinoma with a maximum of two prior chemotherapy regimens were treated with aflibercept 6 mg/kg and docetaxel 75 mg/m 2 every 3 weeks; The confirmed ORR was 54% (11 CRs). Most common Grade 3 4 toxicities were: neutropenia (80%), fatigue (50%) and dyspnea (22%). Adverse events specifically associated with aflibercept were Grade 1 2 hypertension in 5 patients (11%), and Grade 2 proteinuria in 1 patient (2%) [71] IMC-1121B Ramucirumab (IMC-1121B) is a fully human IgG1 monoclonal antibody targeting VEGFR-2. In a phase I study one partial response and one disease stabilization in two heavily pre-treated patients with ovarian cancer were recently reported [72]. Currently, this agent is undergoing phase II evaluation in recurrent ovarian or peritoneal cancer (NCT ) [9] Multiple tyrosine kinase-receptor inhibition The targets of the TKIs used in ovarian carcinoma and the most important studies are shown in Tables 1 and 4, respectively Pazopanib In an interesting concept, pazopanib was used in asymptomatic relapse with increasing CA 125, following CR after first-line chemotherapy [73]. Overall a 31% CA-125 response rate was reported with a median time to response of 29 days and median duration of response of 113 days (range, days). No response was observed in patients with measurable disease but 5 patients (29%) had SD. The most common Grade 3 side effects were fatigue (11%) and GT elevation (11%), while one patient had Grade 4 peripheral edema. This agent has been shown to be safely combined with weekly paclitaxel [74] but not with the classic 3-weekly paclitaxel/carboplatin combination [75]. These results have significant implications for the development of pazopanib in first-line treatment of advanced ovarian cancer Cediranib In a phase II study, including 46 patients with recurrent disease, cediranib showed a 17% objective RR as monotherapy [76]. Most patients (65%) had platinum-resistant disease. Eleven patients (23%) were withdrawn from therapy because of toxicities. Grade 2 hypothyroidism occurred in 43% of patients. Grade 4 toxicities included CNS hemorrhage,

8 A. Bamias et al. / Critical Reviews in Oncology/Hematology 84 (2012) hyperlipidemia and renal (n = 1 for all). In another phase II trial in patients with recurrent disease, who received up to 1 line of prior chemotherapy, there were 2 confirmed and 1 unconfirmed PRs in platinum-sensitive and 1 unconfirmed PR in platinum-resistant patients. Again 9 patients (18%) had to stop treatment due to toxicity [77]. In a phase I study, cediranib was used in combination with the PARP inhibitor, olaparib, in recurrent ovarian (n = 13) or metastatic triple-negative breast cancer (n = 5) [78]. The recommended doses were cediranib 30 mg daily/olaparib 200 mg BID. Among the 9 evaluable ovarian cancer pts there were 1 ccr and 3 cprs. The dose-limiting toxicities were hematological, while class toxicities were within the anticipated ranges BIBF 1120 This triple TKI was studied in a randomized, doubleblind, phase II trial in 83 patients who had just completed chemotherapy for relapsed ovarian cancer, with evidence of response, but at high risk of further early recurrence [79]. A treatment-free interval 12 months between the two last therapies was required. The patients were randomly assigned to receive maintenance therapy using BIBF mg or placebo, twice per day, continuously for 36 weeks. The study suggested that BIBF1120 has efficacy in this setting, since 36-week PFS rate was 16.3% with BIBF 1120 compared with 5% with placebo (HR, 0.65; 95% CI, ; P = 0.06). Grade 3 or 4 adverse events were similar between the groups (34.9% for BIBF 1120 vs. 27.5% for placebo). However, more patients on BIBF 1120 experienced diarrhea, nausea, or vomiting (mainly Grade 1 or 2). There was a higher rate of Grade 3 or 4 liver toxicity in patients on BIBF 1120 compared with patients on placebo (51.2% vs. 7.5%; P < 0.001) Sunitinib One phase II study in 30 patients with recurrent ovarian cancer has been reported [80]. Most patients (72%) were platinum-sensitive. One partial response (3.3%) and three CA125 responses (10%) were observed, all in platinumsensitive patients. The standard 50 mg 4 weeks on-2 weeks off was initially used. Interestingly, fluid accumulation was frequently observed during the holiday period, which was attributed to a rebound phenomenon, associated with increase of VEGF levels. For this reason, the starting dose/schedule was modified for the second stage of accrual to a continuous 37.5 mg p.o. daily schedule Sorafenib Several studies using sorafenib have been reported [81 85]. As monotherapy [81,82] or in combination with gemcitabine [83], it has shown limited efficacy in recurrent disease. In one of these studies, Grade 3 skin toxicity was reported in 20% of patients [82]. In another study, sorafenib was used in combination with carboplatin/paclitaxel as neoadjuvant therapy in advanced ovarian cancer [84]. The study was prematurely terminated after 4 patients had been enrolled due to severe toxicities: 3 patients had life threatening events (cardiac output failure, myocardial infarction, anastomotic leak). In addition, 2 patients had primary progressive disease. Probably the most promising results with sorafenib have been reported in a dose-finding study of sorafenib/bevacizumab combination [85]. The analysis of the 19 platinum-resistant ovarian cancer patients showed a RR of 42%, which is substantially higher than that expected with bevacizumab alone (Section ). Sorafenib was used both continuously and intermittedly (days 1 5/week), with no significant differences in the overall rate of adverse events. Most ovarian cancer patients developed hypertension (84%) and hand-foot syndrome (95%). Grade 3 hypertension was observed in 30% of cases. The intermittent schedule at 200 mg with bevacizumab 5 mg/kg every 2 weeks was considered as the maximal tolerated dose for further development on the basis of lower rate of hypertension Angiopoietin inhibition A recent phase II randomized trial demonstrated activity for the selective angiopoietin 1/2-neutralizing peptibody AMG 386, an investigational peptide-fc fusion protein that neutralizes the interaction between the Tie2 receptor and angiopoietin-1/2 [86]. The addition of AMG 386 to lowdose weekly paclitaxel for recurrent EOC, FTC, or PPC, demonstrated prolongation of PFS from 4.6 to 7.2 months with paclitaxel-amg mg/kg and 5.7 months with paclitaxel-amg mg/kg (HR for both AMG arms vs. placebo 0.76; 80% CI, ; P = 0.165). More than 50% of the 161 patients had platinum-resistant disease. Grade 3 AEs occurring more frequently in arms A or B were hypokalemia, peripheral l edema, hypertension. In a recent pharmacokinetic analysis of this study, an exposuredependent PFS benefit was suggested. Importantly, the maximum effect on prolonging PFS was not achieved at the highest dose tested [87]. 4. Conclusions and future directions The results of the studies reviewed underline the potential of anti-angiogenic strategies in advanced ovarian cancer. After more than a decade, bevacizumab represents the first significant improvement in the management of this disease. Nevertheless, several important issues remain unresolved. As anticipated, the results of the two randomized trials in first-line had rapid implications in the approval status of bevacizumab, which is now approved in some European countries for the treatment of stage III and IV ovarian cancer. The added cost to the existing treatment is substantial and a recent analysis, based on the abstracts rather than the full publications as well as modeling PFS and not OS (since no mature OS data is yet available), questioned the cost effectiveness

9 322 A. Bamias et al. / Critical Reviews in Oncology/Hematology 84 (2012) Table 5 Selected ongoing or recently closed studies with anti-angiogenic agents. Name Context Phase Design Status ROSIA 1st line IV Platinum + taxane based + bevacizumab Closed AGO-Ov 12 1st line III Paclitaxel-carboplatin ± BIBF 1120 Closed GOG 252 1st line III Bevacizumab + IV vs. IP platinum + weekly Open paclitaxel TRINOVA-3 1st line III Paclitaxel-carboplatin ± AMG 386 AGO-Ov 16 1st line maintenance Paclitaxel-carboplatin ± pazopanib maintenance AURELIA PLAT-RESISTANT III Standard chemo ± bevacizumab Closed GOG-213 PLAT-SENSITIVE III Paclitaxel-carboplatin ± bevacizumab Open ICON 6 PLAT-SENSITIVE III Carboplatin + paclitaxel + Placebo vs. cediranib Open concurrent vs. cediranib concurrent + maintenance TRINOVA-1&2 RECURRENT 0 12 m III Weekly paclitaxel/doxil ± AMG 386 of this treatment [88]. Not disregarding the limitations of this particular analysis as well as the use of cost effectiveness analyses to make decisions on drug reimbursement, the issue of the societal cost of this new treatment should not be undermined. More importantly, in searching ways to increase cost effectiveness of a therapy, answers to important scientific questions may be sought. In the case of bevacizumab in ovarian cancer the following issues are particularly relevant: (a) Is there a clinically meaningful overall survival advantage by the addition of this agent to chemotherapy? The survival data of the whole populations are still immature but subgroup analyses of the ICON7 study suggested that there may be a survival advantage in the high-risk population. Nevertheless, until mature survival data are obtained in low risk groups, withholding the drug from these patients cannot be supported; (b) the GOG218 dose and schedule of bevacizumab have been included in the label of the new indication. Are the results from the ICON 7 sufficiently robust to permit treatment at half the dose for 9 months instead of 12 months? If so, total costs would be substantially lower; Both GOG and ICON 7 showed that the advantage from bevacizumab was associated only with the arm using maintenance administration, while there was a trend of benefit reduction after the end of maintenance period. It is reasonable to speculate that longer bevacizumab administration might be associated with a more pronounced benefit. Nevertheless, these issues can only be properly addressed in randomized studies; (c) cost effectiveness of a therapy can be improved by selection of patients likely to achieve longer survival benefit [89]. Ideally, molecular characteristics of tumors should be used to predict of outcome in response to anti-vegf therapy and individualize treatment selection. Nevertheless, in contrast to other targeted therapies, such factors have not yet been conclusively identified for these agents but many of the randomized trials are associated with companion translational research, which is hoped to produce valuable information in this area; (d) are there women with advanced ovarian cancer who should not be offered bevacizumab? Such definitive data are lacking. Nevertheless, given the limitations of bevacizumab use in the perioperative period, as well as the increased probability of GI events in patients with bulky disease, this treatment should be avoided when interval debulking is planned or in non debulked patients. It is noteworthy that such patients were not included in the multicenter, phase IV study (ROSIA, Table 5) of bevacizumab in combination with carboplatin/paclitaxel in front-line treatment. Anti-angiogenic agents have been used in combination with chemotherapy, due to the chemosensitivity of ovarian cancer. Given the survival advantage reported for intraperitoneal vs. systemic therapy regimens in three independent, front-line, randomized, phase III trials [90 92], the safety and efficacy of combining systemic bevacizumab with intraperitoneal platinum-taxane therapy will require investigation. Currently, a phase III trial, GOG 252 (NCT ), is recruiting patients to evaluate bevacizumab in combination with paclitaxel and intraperitoneal cisplatin or carboplatin compared with bevacizumab in combination with intravenous paclitaxel and carboplatin (Table 5). Although, the only current indication of bevacizumab is in 1st line, the results of OCEANS have proven the efficacy in platinum-sensitive disease. A randomized, phase III study assessing the benefit from the addition of bevacizumab to chemotherapy in platinum-resistant disease (AURELIA, Table 5) will also be shortly reported. If the results of this study also favor bevacizumab, the optimal setting for its use will present a dilemma. The benefit of bevacizumab to bevacizumab pre-treated patients will be addressed in currently designed studies. Ongoing research on anti-angiogenic therapies in ovarian cancer does not only involve bevacizumab. It is imperative that our insight into the biological mechanisms of the potential targets needs to be expanded and refined, especially taking into consideration preclinical evidence suggesting that certain isoforms (such as PDGF-BB or Ang-1) may inhibit tumor growth and vasculature-stabilizing effect [48,93]. BIBF 1120 is being studied in 1st-line setting in a phase III randomized study (AGO-Ovar 12), which has recently completed accrual, while AMG 386 is also used in a similar study, which has recently been initiated (Table 5). Cediranib is also tested in platinum sensitive recurrence, in a phase III trial (ICON 6). Results of the stage I have shown that cediranib can be safely combined with carboplatin/paclitaxel. The oral administration of these agents in therapies lasting for more than a year represents an obvious advantage over iv administered agents.

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