Birgit Schultes

Randomized, Placebo-Controlled Study of Oregovomab for Consolidation of Clinical Remission in Patients With Advanced Ovarian Cancer

PURPOSEnTo assess oregovomab as consolidation treatment of advanced ovarian cancer and refine the immunotherapeutic strategy for subsequent study.nnnPATIENTS AND METHODSnPatients with stage III/IV ovarian cancer who had a complete clinical response to primary treatment were randomly assigned to oregovomab or placebo administered at weeks 0, 4, and 8, and every 12 weeks up to 2 years or until recurrence. The primary end-point was time to relapse (TTR).nnnRESULTSnOne hundred forty-five patients were treated with oregovomab (n = 73) or placebo (n = 72). For the population overall, median TTR was not different between treatments at 13.3 months for oregovomab and 10.3 months for placebo (P =.71). Immune responses were induced in most actively treated patients. This was associated with prolonged TTR. Quality of life was not adversely impacted by treatment. Adverse events were reported with similar frequency in oregovomab and placebo groups, indicating a benign safety profile. A long-term survival follow-up is ongoing. Cox analysis of relapse data identified significant factors: performance status, CA-125 before third cycle, and baseline CA-125. Further evaluation identified a subpopulation with favorable prognostic indicators designated as the successful front-line therapy (SFLT) population. For the SFLT population, TTR was 24.0 months in the oregovomab group compared with 10.8 months for placebo (unadjusted hazard ratio of 0.543 [95% CI, 0.287 to 1.025]), a hypothesis-generating observation.nnnCONCLUSIONnConsolidation therapy with oregovomab did not significantly improve TTR overall. A set of confirmatory phase III studies has been initiated to determine whether the SFLT population derives benefit from oregovomab treatment.

Oregovomab Maintenance Monoimmunotherapy Does Not Improve Outcomes in Advanced Ovarian Cancer

PURPOSEnThis phase III study tested the hypothesis that the CA-125-specific murine monoclonal antibody, oregovomab, administered as a monoimmunotherapy after front-line therapy in a selected ovarian cancer population would prolong time to relapse (TTR) and, ultimately, survival.nnnPATIENTS AND METHODSnPatients with stage III to IV ovarian cancer with preoperatively elevated CA-125 and objectively defined characteristics were randomly assigned 4 to 12 weeks after front-line carboplatin and paclitaxel chemotherapy to maintenance monoimmunotherapy in a fully blinded protocol. Two mg of oregovomab or placebo was infused over 20 minutes at weeks 0, 4, and 8 and then 12 weeks until recurrence or up to year 5. Patients were evaluated with serial imaging and clinical evaluation for evidence of recurrence at quarterly visits. TTR was the primary end point.nnnRESULTSnThree hundred seventy-three patients were accrued at more than 60 centers; 251 patients were assigned to oregovomab and 120 patients were assigned to placebo. The treatment arms were well balanced. There were no differences in the clinical outcomes between treatment groups. Median TTR measured from randomization after completion of chemotherapy for the integrated study was 10.3 months (95% CI, 9.7 to 13.0 months) for oregovomab and 12.9 months (95% CI, 10.1 to 17.4 months) for placebo (P = .29, log-rank test). The treatment was well tolerated. Grade 3 to 4 toxicity was reported in 24.6% of patients in the placebo group and 20.1% of patients in the oregovomab group, respectively.nnnCONCLUSIONnAlthough oregovomab has demonstrated bioactivity, the strategy of monoimmunotherapy is not effective as maintenance therapy after front-line treatment of a favorable subset of patients with advanced ovarian cancer. Future studies of this or other tumor-antigen specific immunization strategies should seek ways to further augment induced immunity.

M402, a novel heparan sulfate mimetic, targets multiple pathways implicated in tumor progression and metastasis.

Heparan sulfate proteoglycans (HSPGs) play a key role in shaping the tumor microenvironment by presenting growth factors, cytokines, and other soluble factors that are critical for host cell recruitment and activation, as well as promoting tumor progression, metastasis, and survival. M402 is a rationally engineered, non-cytotoxic heparan sulfate (HS) mimetic, designed to inhibit multiple factors implicated in tumor-host cell interactions, including VEGF, FGF2, SDF-1α, P-selectin, and heparanase. A single s.c. dose of M402 effectively inhibited seeding of B16F10 murine melanoma cells to the lung in an experimental metastasis model. Fluorescent-labeled M402 demonstrated selective accumulation in the primary tumor. Immunohistological analyses of the primary tumor revealed a decrease in microvessel density in M402 treated animals, suggesting anti-angiogenesis to be one of the mechanisms involved in-vivo. M402 treatment also normalized circulating levels of myeloid derived suppressor cells in tumor bearing mice. Chronic administration of M402, alone or in combination with cisplatin or docetaxel, inhibited spontaneous metastasis and prolonged survival in an orthotopic 4T1 murine mammary carcinoma model. These data demonstrate that modulating HSPG biology represents a novel approach to target multiple factors involved in tumor progression and metastasis.

Anti-idiotype induction therapy: anti-CA125 antibodies (Ab3) mediated tumor killing in patients treated with Ovarex mAb B43.13 (Ab1)

Abstractu2003Intravenous injection of the murine monoclonal anti-CA125 antibody B43.13 (Ovarex: Ab1) into ovarian cancer patients led to the induction of an idiotypic network. Of the 75 patients who received one to ten injections of a 2-mg dose of the antibody, 48 developed anti-(mAb B43.13) antibodies (Ab2); 18 of these patients also had elevated levels of anti-[anti-(mAb B43.13)] antibodies (Ab3; = anti-CA125 antibodies) compared to pre-injection values. Characterization of these antibodies revealed that the binding to CA125 could be inhibited by mAb B43.13 in most samples. Human anti-CA125 antibodies or Ab3 purified from patient serum samples specifically recognized human ovarian tumor cells and tissues expressing CA125. In addition, these anti-CA125 antibodies were able to conduct Fc-mediated tumor cell killing (antibody-dependent cell-mediated cytotoxicity). This raises the possibility of using an Ab1 for anti-idiotype induction immunotherapy of cancer.

Biologic and immunologic therapies for ovarian cancer.

Biologic therapy of ovarian cancer has been conducted using nonspecific biologic response modifiers, cytokines, monoclonal antibodies (MAbs), vaccines, and gene therapy. Antibodies directed toward her2/neu have also been studied. Phase I and II gene therapy trials using adenoviral vectors containing a wild-type or modified p53 have shown that the treatment is well tolerated. Phase II and III trials are ongoing with MAbs directed against CA-125 (MAb B43.13) and an antibody directed against HMFG1 (anti-HMFG1-yttrium-90-labeled antibody). The trials have shown that these agents are well tolerated and that immunologic responses occur, although the ultimate clinical value of these agents remains to be determined. Prolonged survival after MAb B43.13 treatment has been correlated with changes in several immune parameters, including human antimurine antibody, Ab2, anti-CA-125 antibody development, and induced T-cell immunity. Clinical trials using a MAb directed toward the encoded products of her2/neu have shown minimal activity against ovarian cancer in a phase I and II trial conducted by the Gynecologic Oncology Group. Cytokine therapies have been administered systemically and intraperitoneally. Intracavitary interferon alfa, interferon gamma, and interleukin-2 alone or in combination with cytotoxic therapy in phase I and II trials demonstrated intraperitoneal lymphoid cell stimulation and produced antitumor responses. A randomized trial of chemotherapy with or without interferon gamma in primary treatment produced a response and a progression-free survival advantage in the arm that incorporated the interferon gamma, without a statistically significant benefit in overall survival. A phase III study of interferon gamma in combination with first-line chemotherapy is currently ongoing.

Monitoring of immune responses to CA125 with an IFN-γ ELISPOT assay

The CA125 (carcinoma antigen 125)-specific antibody MAb-B43.13 (OvaRex MAb-B43.13) is in clinical trials for patients with ovarian carcinoma as an immunotherapeutic agent. To develop an assay for monitoring CA125-specific as well as tumor-specific T cells in the peripheral circulation of ovarian cancer patients treated with this antibody, the IFN (interferon)-gamma enzyme-linked immuno SPOT (ELISPOT) assay was optimized. Various assay formats and experimental conditions were evaluated, using peripheral blood mononuclear cells (PBMC) obtained from normal donors and patients with ovarian cancer. T cell proliferation assays were performed in parallel. Conditions tested included different types of antigen presenting cells (APC), the need for and length of in vitro sensitization to enrich in T cell precursors, titration of the antigen and comparison of pulsing dendritic cells (DC) with immune complexes (IC) of CA125 and monoclonal antibody (MAb)-B43.13 or CA125 antigen alone. Proliferation assays were found not to be sufficiently sensitive for detection of CA125-specific T cells in the peripheral circulation of normal donors. A more sensitive 24-h direct ELISPOT assay was also negative. However, ELISPOT assays preceded by a 7-day in vitro sensitization (IVS) step allowed the detection of CA125 antigen-specific T cells in the circulation of normal donors and patients with ovarian cancer. The use of DC as APC was compared to whole PBMC or immortalized B cells. Most donors and ovarian cancer patients responded best to DC pulsed with CA125 in the form of immune complexes. Optimal responses were seen using CA125 concentrations of 500 U/ml and 5 microg/ml of MAb-B43.13. The data indicate that precursor cells specific for CA125 antigen are present at low frequencies in the peripheral circulation of normal donors and patients with ovarian carcinoma and need to be expanded ex vivo for frequency determinations. The optimized assay is able to detect increases in T cell precursor frequencies to CA125 in ovarian cancer patients after immunization with MAb-B43.13.

A novel IgE antibody targeting the prostate-specific antigen as a potential prostate cancer therapy

BackgroundProstate cancer (PCa) is the second leading cause of cancer deaths in men in the United States. The prostate-specific antigen (PSA), often found at high levels in the serum of PCa patients, has been used as a marker for PCa detection and as a target of immunotherapy. The murine IgG1 monoclonal antibody AR47.47, specific for human PSA, has been shown to enhance antigen presentation by human dendritic cells and induce both CD4 and CD8 T-cell activation when complexed with PSA. In this study, we explored the properties of a novel mouse/human chimeric anti-PSA IgE containing the variable regions of AR47.47 as a potential therapy for PCa. Our goal was to take advantage of the unique properties of IgE in order to trigger immune activation against PCa.MethodsBinding characteristics of the antibody were determined by ELISA and flow cytometry. In vitro degranulation was determined by the release of β-hexosaminidase from effector cells. In vivo degranulation was monitored in human FcεRIα transgenic mice using the passive cutaneous anaphylaxis assay. These mice were also used for a vaccination study to determine the in vivo anti-cancer effects of this antibody. Significant differences in survival were determined using the Log Rank test. In vitro T-cell activation was studied using human dendritic cells and autologous T cells.ResultsThe anti-PSA IgE, expressed in murine myeloma cells, is properly assembled and secreted, and binds the antigen and FcεRI. In addition, this antibody is capable of triggering effector cell degranulation in vitro and in vivo when artificially cross-linked, but not in the presence of the natural soluble antigen, suggesting that such an interaction will not trigger systemic anaphylaxis. Importantly, the anti-PSA IgE combined with PSA also triggers immune activation in vitro and in vivo and significantly prolongs the survival of human FcεRIα transgenic mice challenged with PSA-expressing tumors in a prophylactic vaccination setting.ConclusionsThe anti-PSA IgE exhibits the expected biological properties and is capable of triggering immune activation and anti-tumor protection. Further studies on this antibody as a potential PCa therapy are warranted.

Targeting HER2/neu with a fully human IgE to harness the allergic reaction against cancer cells

Breast and ovarian cancer are two of the leading causes of cancer deaths among women in the United States. Overexpression of the HER2/neu oncoprotein has been reported in patients affected with breast and ovarian cancers, and is associated with poor prognosis. To develop a novel targeted therapy for HER2/neu expressing tumors, we have constructed a fully human IgE with the variable regions of the scFv C6MH3-B1 specific for HER2/neu. This antibody was expressed in murine myeloma cells and was properly assembled and secreted. The Fc region of this antibody triggers in vitro degranulation of rat basophilic cells expressing human FcεRI (RBL SX-38) in the presence of murine mammary carcinoma cells that express human HER2/neu (D2F2/E2), but not the shed (soluble) antigen (ECDHER2) alone. This IgE is also capable of inducing passive cutaneous anaphylaxis in a human FcεRIα transgenic mouse model, in the presence of a cross-linking antibody, but not in the presence of soluble ECDHER2. Additionally, IgE enhances antigen presentation in human dendritic cells and facilitates cross-priming, suggesting that the antibody is able to stimulate a secondary T-cell anti-tumor response. Furthermore, we show that this IgE significantly prolongs survival of human FcεRIα transgenic mice bearing D2F2/E2 tumors. We also report that the anti-HER2/neu IgE is well tolerated in a preliminary study conducted in Macaca fascicularis (cynomolgus) monkeys. In summary, our results suggest that this IgE should be further explored as a potential therapeutic against HER2/neu overexpressing tumors, such as breast and ovarian cancers.

Elucidating the interplay between IgG-Fc valency and FcγR activation for the design of immune complex inhibitors

An engineered trivalent Fc drug candidate is a potent inhibitor of FcγR-driven immune cell activation and autoimmune diseases in animal models. Third Fc’s the charm The activation of Fcγ receptors by autoantibody immune complexes plays a pathogenic role in multiple autoimmune diseases. In an attempt to systematically evaluate potential therapeutic approaches, Ortiz et al. tested different shapes and sizes of Fc-containing molecules. One particular design, a trimer with a Y-shaped configuration, was particularly effective at binding to Fcγ receptors and blocking them without causing inappropriate activation. To demonstrate therapeutic potential, the authors tested this Fc trimer construct in mouse models of three different autoimmune diseases: immune thrombocytopenic purpura, collagen-induced arthritis, and epidermolysis bullosa acquisita, all with promising results. Autoantibody immune complex (IC) activation of Fcγ receptors (FcγRs) is a common pathogenic hallmark of multiple autoimmune diseases. Given that the IC structural features that elicit FcγR activation are poorly understood and the FcγR system is highly complex, few therapeutics can directly block these processes without inadvertently activating the FcγR system. To address these issues, the structure activity relationships of an engineered panel of multivalent Fc constructs were evaluated using sensitive FcγR binding and signaling cellular assays. These studies identified an Fc valency with avid binding to FcγRs but without activation of immune cell effector functions. These observations directed the design of a potent trivalent immunoglobulin G–Fc molecule that broadly inhibited IC-driven processes in a variety of immune cells expressing FcγRs. The Fc trimer, Fc3Y, was highly efficacious in three different animal models of autoimmune diseases. This recombinant molecule may represent an effective therapeutic candidate for FcγR-mediated autoimmune diseases.

Immunomodulation with antibodies: clinical application in ovarian cancer and other malignancies

This review identifies the role of antibodies in the field of therapeutic cancer vaccines. Ovarian cancer is used as a model to review advances in therapeutic vaccine development with a focus on antibodies as immunomodulators and antigen mimetics, highlighting research on B43.13 and ACA125. The interaction of biological immunomodulation and chemotherapy is discussed. Requirements of antigen processing and recent advances in the field of dendritic cell biology are critical to current understanding of potent immune response induction. Future directions including use of growth factors, adjuvants and cellular therapies to enhance effects may potentiate observed effects and provide clues for application in many cancers and beyond oncology.