Phase I pilot trial of the bispecific antibody MDXH210 (anti-Fc gamma RI X anti-HER-2/neu) in patients whose prostate cancer overexpresses HER-2/neu

Targeting T cells with bispecific antibodies for cancer therapy

Bispecific antibodies (BiAbs) offer a unique opportunity to redirect immune effector cells to kill cancer cells. BiAbs combine the benefits of different binding specificities of two monoclonal antibodies (mAbs) into a single construct. This unique feature of BiAbs enables approaches that are not possible with single mAbs. Advances in antibody engineering and antigen profiling of malignant cells have led to the development of a number of BiAb formats and their combinations for redirecting effector cells to tumor targets. There have been significant advances in the design and application of BiAbs for intravenous and local injection.The initial barrier of cytokine storm has been partially overcome by more recent constructs that have improved clinical effectiveness without dose-limiting toxicities. Since the recent revival of BiAbs, there has been multiple, ongoing, phase I/II and III trials, and some promising clinical outcomes have been reported in completed clinical studies. This review focuses on arming T cells with BiAbs to create the 'poor man's cytotoxic lymphocyte'.

Novel antibody-based proteins for cancer immunotherapy

The relative success of monoclonal antibodies in cancer immunotherapy and the vast manipulation potential of recombinant antibody technology have encouraged the development of novel antibody-based antitumor proteins. Many insightful reagents have been produced, mainly guided by studies on the mechanisms of action associated with complete and durable remissions, results from experimental animal models, and our current knowledge of the human immune system. Strikingly, only a small percent of these new reagents has demonstrated clinical value. Tumor burden, immune evasion, physiological resemblance, and cell plasticity are among the challenges that cancer therapy faces, and a number of antibody-based proteins are already available to deal with many of them. Some of these novel reagents have been shown to specifically increase apoptosis/cell death of tumor cells, recruit and activate immune effectors, and reveal synergistic effects not previously envisioned. In this review, we look into different approaches that have been followed during the past few years to produce these biologics and analyze their relative success, mainly in terms of their clinical performance. The use of antibody-based antitumor proteins, in combination with standard or novel therapies, is showing significant improvements in objective responses, suggesting that these reagents will become important components of the antineoplastic protocols of the future.

Neutrophils in antibody-based immunotherapy of cancer

Monoclonal antibodies (mAb) are presently considered key therapeutic drugs for the treatment of malignancies. They can be designed to specifically target tumour-associated antigens and initiate several effector mechanisms, which potentially leads to elimination of the tumour. Through their Fc tail mAbs interact with Fc receptors (FcR) that are expressed on immune cells. Neutrophils are the most abundant circulating FcR-expressing white blood cells with potent cytotoxic ability that is enhanced in the presence of antitumour mAbs. They furthermore play a role in regulating adaptive immunity, which may lead to the initiation of antitumour immune responses. Yet, neutrophils receive surprisingly little attention as potential effector cell population. This article reviews the scientific data that supports the possibility of exploiting neutrophils for mAb-based immunotherapy of cancer. An increasing awareness and understanding of this topic may allow for future development of new anticancer therapies.

A phase-I trial of the epidermal growth factor receptor directed bispecific antibody MDX-447 without and with recombinant human granulocyte-colony stimulating factor in patients with advanced solid tumors

INTRODUCTION

MDX-447 is a bispecific antibody directed against the epidermal growth factor receptor (EGFR) and the high affinity Fc receptor (FcgammaRI). Preclinical data suggest that co-administration of granulocyte-colony stimulating factor (G-CSF) may enhance the tumor cytotoxicity of bispecific antibodies.

METHODS

In group 1, patients received MDX-447 intravenously (i.v.) weekly. Dose levels of MDX-447 evaluated in group 1 were 1, 3.5, 7, 10, 15, 20, 30, and 40 mg/m(2). In group 2, patients received MDX-447 IV weekly with G-CSF (3 mcg/kg/day) subcutaneously (days -3 to +2, 5-9, 12-16, etc.). Dose levels of MDX-447 evaluated in group 2 were 1, 3.5, 7, 10, and 15 mg/m(2).

RESULTS

Sixty-four patients with advanced solid tumors were treated. Forty-one patients received MDX-447 alone (group 1); 23 patients received MDX-447 + G-CSF (group 2). Hypotension was the predominant dose-limiting toxicity (DLT) in both treatment groups, with seven patients experiencing >or= grade 3 events. MDX-447 half-life (T(1/2)) ranged from 1.9 to 8.4 h, with no obvious differences between the two treatment groups. MDX-447 binding to neutrophils and peak levels of circulating tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6) were higher in group 2. The MTD for MDX-447 alone was 30 mg/m(2). When G-CSF was given with MDX-447, treatment was not well tolerated and group 2 was closed early because of safety concerns, with the last patient being treated at the 7 mg/m(2) dose level. There were no objective complete or partial responses in either group.

CONCLUSION

MDX-447 alone was generally well tolerated, but did not achieve objective tumor responses. The MTD for MDX-447 alone was 30 mg/m(2) weekly. Co-administration of G-CSF with MDX-447 precluded meaningful dose escalation.

Advances in specific immunotherapy for prostate cancer

OBJECTIVES

The absence of effective therapies for advanced prostate cancer has entailed an intensive search for novel treatments. This review presents an overview of specific immunotherapeutic strategies for prostate cancer.

METHODS

Current literature was reviewed regarding the identification of tumor antigens and the design of T-cell- and antibody-based immunotherapy for prostate cancer. The PubMed database was searched using the key words antibodies, clinical trials, dendritic cells, immunotherapy, prostate cancer, and T cells.

RESULTS

T cells and antibodies are powerful components of the specific antitumor immune response. CD8+ cytotoxic T lymphocytes (CTLs) efficiently destroy tumor cells. CD4+ T cells improve the antigen-presenting capacity of dendritic cells (DCs) and support the stimulation of tumor-reactive CTLs. Monoclonal antibodies exhibit their antitumor effects via antibody-dependent cellular cytotoxicity and complement activation. Consequently, much attention has been given to the identification of tumor antigens that represent attractive targets for specific immunotherapy. Several prostate cancer-related antigens were described and used in clinical trials. Such studies were based on the administration of peptides, proteins, or DNA. Furthermore, men with prostate cancer were vaccinated with peptide-, protein-, or RNA-loaded DCs, which display an extraordinary capacity to induce tumor-reactive T cells. Monoclonal antibodies directed against surface antigens were also used. Clinical trials revealed that immunotherapeutic strategies represent safe and feasible concepts for the induction of immunologic and clinical responses in men with prostate cancer.

CONCLUSIONS

Specific immunotherapy represents a promising treatment modality for prostate cancer. Further improvement of the current approaches is required and may be achieved by combining T-cell- and antibody-based vaccination strategies with radio-, hormone-, chemo-, or antiangiogenic therapy.

Novel antibodies as anticancer agents

In recent years antibodies, whether generated by traditional hybridoma technology or by recombinant DNA strategies, have evolved from Paul Ehrlich's 'magic bullets' to a modern age 'guided missile'. In the recent years of immunologic research, we are witnessing development in the fields of antigen screening and protein engineering in order to create specific anticancer remedies. The developments in the field of recombinant DNA, protein engineering and cancer biology have let us gain insight into many cancer-related mechanisms. Moreover, novel techniques have facilitated tools allowing unique distinction between malignantly transformed cells, and regular ones. This understanding has paved the way for the rational design of a new age of pharmaceuticals: monoclonal antibodies and their fragments. Antibodies can select antigens on both a specific and a high-affinity account, and further implementation of these qualities is used to target cancer cells by specifically identifying exogenous antigens of cancer cell populations. The structure of the antibody provides plasticity resonating from its functional sites. This review will screen some of the many novel antibodies and antibody-based approaches that are being currently developed for clinical applications as the new generation of anticancer agents.

VRP immunotherapy targeting neu: treatment efficacy and evidence for immunoediting in a stringent rat mammary tumor model

The ability to overcome intrinsic tolerance to a strict "self" tumor-associated antigen (TAA) and successfully treat pre-existing tumor is the most stringent test for anti-tumor immunotherapeutic strategies. Although this capacity has been demonstrated in various models using complicated strategies that may not be readily translated into the clinical arena, straightforward antigen-specific immunotherapeutic strategies in the most stringent models of common epithelial cancers have largely failed to meet this standard. We employed an immunotherapeutic strategy using an alphavirus-based, virus-like replicon particle (VRP), which has in vivo tropism for dendritic cells, to elicit immune responses to the non-mutated TAA rat neu in an aggressive rat mammary tumor model. Using this VRP-based immunotherapeutic strategy targeting a single TAA, we generated effective anti-tumor immunity in the setting of pre-existing tumor resulting in the cure of 36% of rats over multiple experiments, P = 0.002. We also observed down-regulation of rat neu expression in tumors that showed initial responses followed by tumor escape with resumption of rapid tumor growth. These responses were accompanied by significant anti-tumor proliferative responses and CD8+ cellular tumor infiltrates, all of which were restricted to animals receiving the anti-neu immunotherapy. Together these data, obtained in a stringent "self" TAA model, indicate that the VRP-based antigen-specific immunotherapy elicits sufficiently potent immune responses to exert immunologic pressure, selection, and editing of the growing tumors, thus supporting the activity of this straightforward immunotherapy and suggesting that it is a promising platform upon which to build even more potent strategies.

Advances in Prostate Cancer Immunotherapies

Prostate cancer is a major cause of mortality in men in the Western world. Although treatment of early stage prostate cancer with radiation therapy or prostatectomy is efficient in most cases, some patients develop a fatal hormone-refractory disease. Treatments in this case are limited to aggressive chemotherapies, which can reduce serum prostate-specific antigen (PSA) levels in some patients. Taxane- and platinum-compound-based chemotherapies produce a survival benefit of only a few months. Therefore, it is crucial to develop novel, well tolerated treatment strategies. Over the past years, immunotherapy of hormone-refractory prostate cancer has been studied in numerous clinical trials. The fact that the prostate is a non-essential organ makes prostate cancer an excellent target for immunotherapy. Administration of antibodies targeting the human epidermal growth factor receptor-2 or the prostate-specific membrane antigen led to stabilisation of PSA levels in several patients. Vaccination of prostate cancer patients with irradiated allogeneic prostate cell lines has demonstrated that whole cell-based vaccines can significantly attenuate increases in PSA. Two different recombinant viral expression vectors have been applied in prostate cancer treatment: poxvirus and adenovirus vectors. Both vaccines have the advantages of using a natural method to induce immune responses and achieving high levels of transgene expression. Vaccinia viruses in combination with recombinant fowlpox or canarypox virus have been used to express recombinant PSA. Several studies demonstrated that this approach is safe and can lead to stabilisation of PSA values. A very promising approach in prostate cancer immunotherapy is vaccination of patients with dendritic cells. Thereby, peptides, recombinant proteins, tumour lysates or messenger RNA have been used to deliver antigens to autologous dendritic cells. Loading of dendritic cells with up to five different peptides derived from multiple proteins expressed in prostate cancer demonstrated that cytotoxic T-cell responses could be elicited in prostate cancer patients. Sipuleucel-T (APC8015), an immunotherapy product consisting of antigen-presenting cells, loaded ex vivo with a recombinant fusion protein consisting of prostatic acid phosphatase linked to granulocyte-macrophage colony-stimulating factor, demonstrated in a phase III, placebo-controlled trial an improvement in median time to disease progression. The improvement in overall survival was 4.5 months for sipuleucel-T-treated patients compared with the placebo group. Although there is a minor increase in overall survival of metastatic prostate cancer patients with some approaches, more effective therapeutic strategies need to be developed.

Immunotherapy for Prostate Cancer: What's the Future?

Prostate cancer is the most common noncutaneous cancer and second leading cause of cancer death among US men. A greater understanding of basic immunologic principles has led to a variety of new techniques,which has led to advancements in prostate cancer vaccines. This article discusses the rationale for the development of antibody-based therapy and vaccines therapy, including whole tumor cells, dendritic cells, and pox viral vectors. A summary of selected clinical studies incorporating these strategies and new approaches incorporating a combination of immunotherapy with traditional treatments for prostate cancer is presented.

Tumor-related immunity in prostate cancer patients treated with human recombinant granulocyte monocyte-colony stimulating factor (GM-CSF)

BACKGROUND

Granulocyte monocyte-colony stimulating factor (GM-CSF) supports the survival, expansion, and differentiation of lymphoid and myeloid derived dendritic cells (DCs). We hypothesized that systemic therapy with GM-CSF in prostate cancer patients could augment prostate cancer-related immunity and induce clinical response.

METHODS

Eligible patients were randomly assigned to receive either 125 or 250 microg/m(2) GM-CSF subcutaneously three times a week until clinical progression. Prostate-specific antigen (PSA) T cell precursor frequencies were determined by a flow cytometric method.

RESULTS

We were able to show, for the first time, a statistically significant correlation between pre-treatment PSA level and PSA-specific CD4(+) T cell precursors and a trend between pre-treatment PSA level and PSA-specific CD8(+) T cell precursors (P<0.0001 and P=0.059, respectively).

CONCLUSIONS

These results suggest that existent immunity to PSA in prostate cancer patients may be a promising target for future immunotherapeutic approaches to prostate cancer.

Retargeting T cells and immune effector cells with bispecific antibodies

The development of BiAbs for therapeutic applications in cancer shows promise. As our understanding of effector cell receptor biology for triggering of cytotoxic functions improves and the behavior of TAA and the targeting antibody engagement is elucidated, customized BiAb reagents can be engineered to optimize in vivo or ex vivo arming of T cells for targeting tumors. Additionally, other variables that require consideration in the equation for successful T cell immunotherapy include: the type of effector cells, their state of activation, the type of effector receptor being activated or tareeted. the presence of Tregs, the affinity of the anti-effector cell antibody and the anti-TAA antibody, the type of BiAb (mouse, humanized, or human), the number of binding sites for the T cells or TAA, the presence or absence of decoy antigen, whether the TAA modulates after being engaged by antibody, the type of tumor, the tumor burden, and last, but not least, the amount of 'immunologic' space available for the adoptively transferred cells to expand and function.

Genes differentially expressed in prostate cancer

Because of the heterogeneity of prostate cancer knowledge about the genes involved in prostate carcinogenesis is still very limited. Previously, the use of novel high-throughput technologies offered the possibility to investigate broad gene expression profiles and thus helped to improve understanding of the molecular basis of prostate disease. Many candidate genes have been identified so far which have a more or less strong effect on prostate cancer. This vast number of gene expression changes show that it is unlikely that only one gene promotes prostate cancer. Conversely, it seems more likely that a broad network of molecular changes is involved in the complex cascade of events which lead to tumour formation and progression, respectively. A few of these novel molecular targets are currently under clinical evaluation. This paper gives an overview of several interesting candidate genes which may be useful as improved biomarkers for diagnosis or as targets for developing novel treatment methods.

The Role of Growth Factors for Disease and Therapy in Diseases of the Head and Neck

Growth factors are a large family of polypeptide molecules that regulate cell division in many tissues by autocrine or paracrine mechanisms. Depending on what receptors are activated, growth factors can initiate mitogenic, antiproliferative, or trophic effects, that is, growth factors act as positive or negative modulators of cell proliferation. Therefore, growth factors do not only play an important role in embryonic development and adult tissue homeostasis, but also in pathological situations like infection, wound healing, and tumorigenesis. Consequently, the application of growth factors, or vice versa the application of substances which are directed against growth factors like antigrowth factor antibodies, may have therapeutic applications. This review provides a brief account of what we know regarding growth factors in otorhinolaryngology, particularly in the field of otology, wound healing, oncology, peripheral nerve regeneration, and rhinology.

Epithelial cell differentiation in the human prostate epithelium: implications for the pathogenesis and therapy of prostate cancer

Within the human prostate epithelium four cell populations are discriminated by their expression of keratins (K). While basal cells co-localize K5 and K14 combined with low levels of K18 (K5(++)/14(++)/18(+)), luminal cells highly express K18 (K18(++)). In addition, two intermediate subpopulations are characterized either by basal K5(++)/18(+)- or luminal K5(+)/18(++)- expression. The entire prostate epithelium is putatively derived from a basal stem cell population. They give rise to intermediate cells that transiently proliferate and mature towards differentiated luminal epithelium. Within prostate carcinoma luminal exocrine, neuro-endocrine and intermediate cells are distinguished. Intermediate cells have been postulated as progenitors for prostate carcinogenesis and targets for androgen-independent tumor progression. Androgen-independency is associated with an enrichment of intermediate cells and over-expression of peptide growth factor receptors. Targeting intermediate cells by inhibition of their peptide growth factor receptors, therefore, offers novel treatment modalities for prostate cancer.

Immunotherapy and prostate cancer

Prostate cancer is the second leading cause of cancer death in the US, largely because of the limitations of our current therapeutic options, especially once the cancer has metastasized. Investigators have long sought new therapeutic modalities such as angiogenesis inhibitors, vaccines, and gene therapy, among others. It appears that a combination approach will be required to cure the majority of malignancies. Immunotherapy for prostate cancer appears feasible and a likely therapeutic modality in the armamentarium. Unfortunately, further research in basic immunology and the interaction of the immune system with other forms of therapy is needed. Many obstacles exist in immunotherapy, including vector design, tumouricidal specificity, and tumor evasion, which will have to be overcome in order to realize the maximum therapeutic benefit from this treatment modality.

Bispecific antibody conjugates in therapeutics

Bispecific monoclonal antibodies have drawn considerable attention from the research community due to their unique structure against two different antigens. The two-arm structure of bsMAb allows researchers to place a therapeutic agent on one arm while allowing the other to specifically target the disease site. The therapeutic agent can be a drug, toxin, enzyme, DNA, radionuclide, etc. Furthermore, bsMAb may redirect the cytotoxicity of immune effector cells towards the diseased cells or induce a systemic immune response against the target. BsMAb holds great promise for numerous therapeutic needs in the light of: (1) recent breakthroughs in recombinant DNA technology, (2) the increased number of identified disease targets as the result of the completion of human genomic map project, and (3) a better understanding of the mechanism of human immune system. This review focuses on therapeutic applications and production of bsMAb while providing the up-to-date clinical trial information.

Expression of colony-stimulating factor 1 receptor during prostate development and prostate cancer progression

Colony-stimulating factor-1 receptor (CSF-1R) is the major regulator of macrophage development and is associated with epithelial cancers of the breast and ovary. Immunohistochemistry analysis of murine prostate development demonstrated epithelial expression of CSF-1R during the protrusion of prostatic buds from the urogenital sinus, during the prepubertal and androgen-driven proliferative expansion and branching of the gland, with a decline in older animals. Models of murine prostate cancer showed CSF-1R expression in areas of carcinoma- and tumor-associated macrophages. Several human prostate cancer cell lines and primary cultures of human prostate epithelial cells had low but detectable levels of CSF-1R. Human prostatectomy samples showed low or undetectable levels of receptor in normal glands or benign prostatic hypertrophy specimens. Staining was strongest in areas of prostatic intraepithelial neoplasia or carcinoma of Gleason histological grade 3 or 4. The activated form of the receptor reactive with antibodies specific for phosphotyrosine modified peptide sequences was observed in samples of metastatic prostate cancer. Immunohistochemistry showed strong expression of CSF-1R by macrophage lineage cells, including villous macrophages and the syncytiotrophoblast layer of placenta, Kupper cells in the liver, and histiocytes infiltrating near prostate cancers. These observations correlate CSF-1R expression with changes in the growth and development of the normal and neoplastic prostate.

Advances in prostate cancer immunotherapy

Metastatic prostate cancer remains incurable. Harnessing the body's own immune system to control or eradicate tumours has long been an attractive concept. Only recently has the field of tumour immunology provided the basic science behind the mechanisms of tumour genesis, molecular basis of the recognition of tumour associated antigens and the interactions of the antigen-presenting cells with effector cells. This research has been translated into numerous clinical immunotherapy strategies, which have reached the oncology clinic and which should provide options for our patients.

Bispecific antibody-targeted phagocytosis of HER-2/neu expressing tumor cells by myeloid cells activated in vivo

Studies from our laboratory and others have established that both mononuclear phagocytes and neutrophils mediate very efficient cytotoxicity when targeted through Fc receptors using a suitable monoclonal or bispecific antibody (BsAb). Cross-linking an Fc receptor for IgG (FcgammaR) triggers multiple anti-tumor activities including superoxide generation, cytokine and enzyme release, phagocytosis and antibody-dependent cellular cytotoxicity (ADCC). In this report, using unfractionated leukocytes and two color flow cytometric analysis, we describe the phagocytic capacity of peripheral blood polymorphonuclear cells (PMN) and monocytes isolated from patients enrolled in a phase I clinical trial of MDX-H210 given in combination with IFNgamma. MDX-H210 is a BsAb targeting the myeloid trigger molecule FcgammaRI and the HER-2/neu proto-oncogene product overexpressed on a variety of adenocarcinomas. In this trial, cohorts of patients received escalating doses of MDX-H210 3 times per week for 3 weeks. Interferon-gamma (IFNgamma) was given 24 h prior to each BsAb infusion. Our results demonstrate that monocytes from these patients were inherently capable of phagocytosing the HER-2/neu positive SK-BR-3 cell line and that addition of MDX-H210 into the assay significantly enhanced the number of targets phagocytosed. Two days after administration of an immunologically active dose of MDX-H210 (10 mg/m2), monocytes from these patients were able to phagocytose greater amounts of target cell material, indicating that these cells remained armed with functionally sufficient BsAb for at least 48 h. PMN from these patients very efficiently mediated phagocytosis through FcgammaRI after being treated with IFNgamma, but not before. We conclude that phagocytosis is not only an efficient mechanism of myeloid cell-mediated cytotoxicity, but may also be a mechanism by which antigens from phagocytosed cells can enter a professional antigen presenting cell for processing and presentation.