Monoclonal antibody therapy of ovarian cancer

CD55, CD59, factor H and factor H-like 1 gene expression analysis in tumors of the ovary and corpus uteri origin

The expression level of complement regulators in ovarian and corpus uteri tumors was not fully established so far. In current manuscript we performed gene expression analysis by the real-time PCR approach to investigate both membrane bound - CD55 and CD59 and fluid phase - factor H and factor H-like 1 complement regulators. We found increased CD55 expression in corpus uteri tumors when compared to control tissues, whereas in ovarian cancer CD55 expression was lower than in control sections. Additionally we found CD59 expression to be more prominent in ovarian cancer than in corpus uteri tumor samples. We observed also the strong positive correlation between the level of expression of the whole group of regulators, which was particularly significant between the expression of factor H and factor H- like 1. In conclusion we present novel results which implicates different role of particular complement inhibitors in the regulation of the complement system in two cancer types examined. Strong positive correlation between examined proteins implicates similar pattern of the regulation which should be taken into consideration with regards to the possible immunotherapy applied as adjuvant therapeutic approach in these two indications. The inhibition of complement regulation may serve as a strategy to potentiate the efficacy of such treatment.

Effect of immune complex formation on the distribution of a novel antibody to the ovarian tumor antigen CA125

3A5 is a novel antibody that binds repeated epitopes within CA125, an ovarian tumor antigen that is shed into the circulation. Binding to shed antigen may limit the effectiveness of therapeutic antibodies because of unproductive immune complex (IC) formation and/or altered antibody distribution. To evaluate this possibility, we characterized the impact of shed CA125 on the in vivo distribution of 3A5. In vitro, 3A5 and CA125 were found to form ICs in a concentration-dependent manner. This phenomenon was then evaluated in vivo using quantitative whole-body autoradiography to assess the tissue distribution of (125)I-3A5 in an orthotopic OVCAR-3 tumor mouse model at different stages of tumor burden. Low doses of 3A5 (75 μg/kg) and pathophysiological levels of shed CA125 led to the formation of ICs in vivo that were rapidly distributed to the liver. Under these conditions, increased clearance of 3A5 from normal tissues was observed in mice bearing CA125-expressing tumors. Of importance, despite IC formation, 3A5 uptake by tumors was sustained over time. At a therapeutically relevant dose of 3A5 (3.5 mg/kg), IC formation was undetectable and distribution to normal tissues followed that of blood. In contrast, increased levels of radioactivity were observed in the tumors. These data demonstrate that CA125 and 3A5 do form ICs in vivo and that the liver is involved in their uptake. However, at therapeutic doses of 3A5 and clinically relevant CA125 levels, IC formation consumes only a minor fraction of 3A5, and tumor targeting seems to be unaffected.

Targeting the epidermal growth factor receptor in epithelial ovarian cancer: current knowledge and future challenges

The epidermal growth factor receptor is overexpressed in up to 60% of ovarian epithelial malignancies. EGFR regulates complex cellular events due to the large number of ligands, dimerization partners, and diverse signaling pathways engaged. In ovarian cancer, EGFR activation is associated with increased malignant tumor phenotype and poorer patient outcome. However, unlike some other EGFR-positive solid tumors, treatment of ovarian tumors with anti-EGFR agents has induced minimal response. While the amount of information regarding EGFR-mediated signaling is considerable, current data provides little insight for the lack of efficacy of anti-EGFR agents in ovarian cancer. More comprehensive, systematic, and well-defined approaches are needed to dissect the roles that EGFR plays in the complex signaling processes in ovarian cancer as well as to identify biomarkers that can accurately predict sensitivity toward EGFR-targeted therapeutic agents. This new knowledge could facilitate the development of rational combinatorial therapies to sensitize tumor cells toward EGFR-targeted therapies.

Recurrent epithelial ovarian cancer: pharmacotherapy and novel therapeutics

Epithelial ovarian cancer will strike between 1 - 2% of women in developed countries and, unfortunately, it largely remains a lethal disease due to late-stage at diagnosis and the eventual development of chemotherapy resistance. Ovarian cancer is initially treated with surgical resection and chemotherapy (primarily platinum/taxane combinations) and remission can be attained for the majority of patients. Despite this, most women will recur and require multiple further therapies. The purpose of this paper is to review the existing treatment options, including surgery, traditional chemotherapy as well as upcoming novel and targeted therapies that may one day improve outcomes in this disease.

Update in the management of ovarian and cervical carcinoma

Ovarian and cervical cancers are significant health problems. This article provides an update in selected management topics. Paclitaxel and platinum derivatives are the first-line treatment for patients with advanced disease. In selected patients, intraperitoneal chemotherapy has been associated with improved survival but the broad applicability of this strategy is limited by issues of toxicity and feasibility. Management of patients with recurrent disease is based on a number of factors and includes surgery in selected cases, platinum-based chemotherapy for patients with platinum-sensitive disease and other agents such as topotecan and pegylated liposomal formulation of doxorubicin for patients with platinum-resistant disease. In cervical cancer, the most significant issue/event is the demonstration of superior survival with topotecan and cisplatin compared to cisplatin alone. Finally, new agents such as epidermal growth factor receptor inhibitors and antiangiogenic agents are being currently tested in these settings.

Development of radioimmunotherapeutic and diagnostic antibodies: an inside-out view

Only a handful of radiolabeled antibodies (Abs) have gained US Food and Drug Administration (FDA) approval for use in clinical oncology, including four immunodiagnostic agents and two targeted radioimmunotherapeutic agents. Despite the advent of nonimmunogenic Abs and the availability of a diverse library of radionuclides, progress beyond early Phase II radioimmunotherapy (RIT) studies in solid tumors has been marginal. Furthermore, [18F]fluorodeoxyglucose continues to dominate the molecular imaging domain, underscored by a decade-long absence of any newly approved Ab-based imaging agent (none since 1996). Why has the development of clinically successful Abs for RIT been limited to lymphoma? What obstacles must be overcome to allow the FDA approval of immuno-positron emission tomography (immuno-PET) imaging agents? How can we address the unique challenges that have thus far prevented the introduction of Ab-based imaging agents and therapeutics for solid tumors? Many poor decisions have been made regarding radiolabeled Abs, but useful insight can be gained from these mistakes. The following review addresses the physical, chemical, biological, clinical, regulatory and financial limitations that impede the progress of this increasingly important class of drugs.

IgE-antibody-dependent immunotherapy of solid tumors: cytotoxic and phagocytic mechanisms of eradication of ovarian cancer cells

Abs have a paramount place in the treatment of certain, mainly lymphoid, malignancies, although tumors of nonhemopoietic origin have proved more refractory ones. We have previously shown that the efficacy of immunotherapy of solid tumors, in particular ovarian carcinoma, may be improved by the use of IgE Abs in place of the conventional IgG. An IgE Ab (MOv18 IgE) against an ovarian-tumor-specific Ag (folate binding protein), in combination with human PBMC, introduced into ovarian cancer xenograft-bearing mice, greatly exceeded the analogous IgG1 in promoting survival. In this study, we analyzed the mechanisms by which MOv18 IgE may exert its antitumor activities. Monocytes were essential IgE receptor-expressing effector cells that mediated the enhanced survival of tumor-bearing mice by MOv18 IgE and human PBMC. Monocytes mediated MOv18 IgE-dependent ovarian tumor cell killing in vitro by two distinct pathways, cytotoxicity and phagocytosis, acting respectively through the IgE receptors FcepsilonRI and CD23. We also show that human eosinophils were potent effector cells in MOv18 IgE Ab-dependent ovarian tumor cell cytotoxicity in vitro. These results demonstrate that IgE Abs can engage cell surface IgE receptors and activate effector cells against ovarian tumor cells. Our findings offer a framework for an improved immunotherapeutic strategy for combating solid tumors.

Armed antibodies targeting the mucin repeats of the ovarian cancer antigen, MUC16, are highly efficacious in animal tumor models

MUC16 is a well-validated cell surface marker for serous adenocarcinomas of the ovary and other gynecologic malignancies that is distinguished by highly repetitive sequences ("mucin repeats") in the extracellular domain (ECD). We produced and compared two monoclonal antibodies: one (11D10) recognizing a unique, nonrepeating epitope in the ECD and another (3A5) that recognizes the repeats and binds multiple sites on each MUC16 protein. 3A5 conjugated to cytotoxic drugs exhibited superior toxicity against tumor cells in vitro and in tumor xenograft models compared with antibody-drug conjugates of 11D10. Importantly, drug conjugates of 3A5 were well tolerated in primates at levels in excess of therapeutic doses. Additionally, the presence of circulating CA125 in a rat model did not exacerbate the toxicity of 3A5 drug conjugates. We conclude that targeting the repeat MUC16 domains, thereby increasing cell-associated levels of drug-conjugated antibody, provides superior efficacy in vitro and in vivo without compromising safety.

Copper-67 radioimmunotherapy and growth inhibition by anti-L1-cell adhesion molecule monoclonal antibodies in a therapy model of ovarian cancer metastasis

PURPOSE

We examined the tumor-targeting and therapeutic effects of (67)Cu-labeled single amino acid mutant forms of anti-L1 monoclonal antibody chCE7 in nude mice with orthotopically implanted SKOV3ip human ovarian carcinoma cells.

EXPERIMENTAL DESIGN

For radioimmunotherapy, chCE7 antibodies with a mutation of histidine 310 to alanine (chCE7H310A) and a mutation of asparagine 297 to glutamine (chCE7agl) were generated to achieve more rapid blood clearance. Biodistributions of (67)Cu-4-(1,4,8,11-tetraazacyclotetradec-1-yl)-methyl benzoic acid tetrachloride (CPTA)-labeled mutant antibodies were measured in nude mice bearing SKOV3ip human ovarian cancer metastases. The effects of single i.v. injections of (67)Cu-chCE7agl alone on tumor reduction and survival were investigated. In addition, a combination of low-dose (67)Cu-radioimmunotherapy with unlabeled anti-L1 antibody L1-11A on survival was investigated.

RESULTS

(67)Cu-CPTA-chCE7agl showed high (up to 49% ID/g) and persistent (up to 168 h) uptake in SKOV3ip metastases, with low levels in normal tissues. (67)Cu-CPTA-chCE7H310A revealed a shorter half-life in the blood and a lower tumor uptake and retention. A single low dose of 4 MBq of (67)Cu-chCE7agl reduced tumor growth but did not prolong survival significantly, whereas a single 10.5 MBq dose of (67)Cu-chCE7agl reduced tumor growth and prolonged survival significantly. The combination of unlabeled monoclonal antibody L1-11A with a subtherapeutic dose of (67)Cu-radioimmunotherapy also prolonged survival significantly.

CONCLUSION

The results show improved pharmacokinetics and biodistributions as well as the therapeutic effect of the (67)Cu-labeled single amino acid mutant chCE7agl. Therapeutic data indicate, for the first time, the feasibility of combining anti-L1-directed growth inhibition and (67)Cu-radioimmunotherapy, thereby increasing the efficiency of antibody treatment of metastatic ovarian carcinoma.

Detection of human antibodies generated against therapeutic antibodies used in tumor therapy

Application of monoclonal antibodies (MAb) for therapeutic purpose may induce the formation of human antibodies directed against the immunogenic epitopes, which are presented on the therapeutic MAb. Formation of such human antibodies mostly is an undesired side effect, but in the case of newly developed immunotherapeutic tumor treatment strategies it represents the underlying therapeutic effect. Especially the formation of so-called "internal image" antibodies, which are directed against the antigen-combining site (paratope) of the therapeutic antibody, is supposed to evoke specific immune responses against tumor antigens mediated via idiotype-anti-idiotype interactions within the immunoregulatory network. For the monitoring of the immune response after antibody application, the newly formed human antibodies can be measured with immunoassay procedures involving the applied therapeutic antibody as test antibody. Because the original antigen is directed against the therapeutic antibody and inhibits the binding of "internal image" antibodies, a special assay design is needed to avoid interferences with samples containing the antigen. We describe an immunoassay procedure that allows the correct quantification of antiidiotypic antibodies including "internal image" antibodies that are not affected by the original antigen or other serum components that may interact with the therapeutic antibody.

Ovarian cancer vaccine trials and tribulations

Solid tumor vaccine therapy is coming of age. After years of failures, setbacks and negative trials, the first positive trials of antitumor vaccines in humans are being seen. Antitumor vaccine trials have reported an improvement in progression-free survival in breast cancer and an overall survival advantage in prostate cancer. Although, to date no positive Phase III antitumor vaccines trials in ovarian cancer have been reported, recent great strides have been made in improving tumor vaccine target antigens, improving antigen presentation and understanding the mechanisms of immunosuppression associated with tumors. In addition, biological therapies are now being identified that may enhance the efficacy of tumor vaccines. This review summarizes recent trials of ovarian cancer vaccines and addresses future directions to improve vaccine efficacy.