Development and approval of the trifunctional antibody catumaxomab (anti-EpCAM×anti-CD3) as a targeted cancer immunotherapy

Emerging role of cancer stem cells in the biology and treatment of ovarian cancer: basic knowledge and therapeutic possibilities for an innovative approach

In 2013 there will be an estimated 22,240 new diagnoses and 14,030 deaths from ovarian cancer in the United States. Despite the improved surgical approach and the novel active drugs that are available today in clinical practice, about 80% of women presenting with late-stage disease have a 5-year survival rate of only 30%. In the last years a growing scientific knowledge about the molecular pathways involved in ovarian carcinogenesis has led to the discovery and evaluation of several novel molecular targeted agents, with the aim to test alternative models of treatment in order to overcome the clinical problem of resistance. Cancer stem cells tend to be more resistant to chemotherapeutic agents and radiation than more differentiated cellular subtypes from the same tissue. In this context the study of ovarian cancer stem cells is taking on an increasingly important strategic role, mostly for the potential therapeutic application in the next future. In our review, we focused our attention on the molecular characteristics of epithelial ovarian cancer stem cells, in particular on possible targets to hit with targeted therapies.

Bispecific antibodies and trispecific immunocytokines for targeting the immune system against cancer: preparing for the future

Monoclonal anti-tumor antibodies (mAbs) that are clinically effective usually recruit, via their constant fragment (Fc) domain, Fc receptor (FcR)-positive accessory cells of the immune system and engage these additionally against the tumor. Since T cells are FcR negative, these important cells are not getting involved. In contrast to mAbs, bispecific antibodies (bsAbs) can be designed in such a way that they involve T cells. bsAbs are artificially designed molecules that bind simultaneously to two different antigens, one on the tumor cell, the other one on an immune effector cell such as CD3 on T cells. Such dual antibody constructs can cross-link tumor cells and T cells. Many such bsAb molecules at the surface of tumor cells can thus build a bridge to T cells and aggregate their CD3 molecules, thereby activating them for cytotoxic activity. BsAbs can also contain a third binding site, for instance a Fc domain or a cytokine that would bind to its respective cytokine receptor. The present review discusses the pros and cons for the use of the Fc fragment during the development of bsAbs using either cell-fusion or recombinant DNA technologies. The recombinant antibody technology allows the generation of very efficient bsAbs containing no Fc domain such as the bi-specific T-cell engager (BiTE). The strong antitumor activity of these molecules makes them very interesting new cancer therapeutics. Over the last decade, we have developed another concept, namely to combine bsAbs and multivalent immunocytokines with a tumor cell vaccine. The latter are patient-derived tumor cells modified by infection with a virus. The virus-Newcastle Disease Virus (NDV)-introduces, at the surface of the tumor cells, viral molecules that can serve as general anchors for the bsAbs. Our strategy aims at redirecting, in an Fc-independent fashion, activities of T cells and accessory cells against autologous tumor antigens. It creates very promising perspectives for a new generation of efficient and safe cancer therapeutics that should confer long-lasting anti-tumor immunity.

Role of the EpCAM (CD326) in prostate cancer metastasis and progression

Despite significant advances in surgery, radiotherapy and chemotherapy to treat prostate cancer (CaP), many patients die of secondary disease (metastases). Current therapeutic approaches are limited, and there is no cure for metastatic castration-resistant prostate cancer (CRPC). Epithelial cell adhesion molecule (EpCAM, also known as CD326) is a transmembrane glycoprotein that is highly expressed in rapidly proliferating carcinomas and plays an important role in the prevention of cell-cell adhesion, cell signalling, migration, proliferation and differentiation. Stably and highly expressed EpCAM has been found in primary CaP tissues, effusions and CaP metastases, making it an ideal candidate of tumour-associated antigen to detect metastasis of CaP cells in the circulation as well as a promising therapeutic target to control metastatic CRPC disease. In this review, we discuss the implications of the newly identified roles of EpCAM in terms of its diagnostic and metastatic relevance to CaP. We also summarize EpCAM expression in human CaP and EpCAM-mediated signalling pathways in cancer metastasis. Finally, emerging and innovative approaches to the management of the disease and expanding potential therapeutic applications of EpCAM for targeted strategies in future CaP therapy will be explored.

Heterodimeric bispecific single-chain variable-fragment antibodies against EpCAM and CD16 induce effective antibody-dependent cellular cytotoxicity against human carcinoma cells

A heterodimeric bispecific biological recombinant drug was synthesized by splicing DNA fragments from two fully humanized single-chain variable-fragment (scFV) antibody fragments forming a novel drug simultaneously recognizing the CD16 natural killer (NK) cell marker and the cancer marker epithelial cell adhesion molecule (EpCAM). The drug precipitously enhanced the killing of human carcinomas of the prostate, breast, colon, head, and neck even at very low effector:target ratios. The drug EpCAM16 rendered even nonactivated NK cell-proficient killers and activated them to kill via degranulation and cytokine production. Studies show that bispecific antibodies can be used to induce proficient killing of the carcinoma targets that ordinarily are resistant to NK-mediated killing. Apparently, the innate immune system can be effectively recruited to kill cancer cells using the bispecific antibody platform and EpCAM targeting.

Cancerous ovarian stem cells: obscure targets for therapy but relevant to chemoresistance

Chemotherapy with platinum and taxanes is the first line of treatment for all epithelial ovarian cancer (EOC) patients after debulking surgery. Even though the treatment is initially effective in 80% of patients, recurrent cancer is inevitable in the vast majority of cases. Emerging evidence suggests that some tumor cells can survive chemotherapy by activating the self-renewal pathways resulting in tumor progression and clinical recurrence. These defined population of cells commonly termed as "cancer stem cells" (CSC) may generate the bulk of the tumor by using differentiating pathways. These cells have been shown to be resistant to chemotherapy and, to have enhanced tumor initiating abilities, suggesting CSCs as potential targets for treatment. Recent studies have introduced a new paradigm in ovarian carcinogenesis which proposes in situ carcinoma at the fimbrial end of the fallopian tube to generate high-grade serous ovarian carcinomas, in contrast to ovarian cortical inclusion cysts (CIC) which produce borderline and low grade serous, mucinous, endometrioid, and clear cell carcinomas. This review summarizes recent advances in our understanding of the cellular origin of EOC and the molecular mechanisms defining the basis of CSC in EOC progression and chemoresistance. Using a model ovarian cancer cell line, we highlight the role of CSC in response to chemotherapy, and relate how CSCs may impact on chemoresistance and ultimately recurrence. We also propose the molecular targeting of CSCs and suggest ways that may improve the efficacy of current chemotherapeutic regimens needed for the management of this disease.

Redirection of T-cell effector functions for cancer therapy: bispecific antibodies and chimeric antigen receptors

T cells are the most potent cells of the immune system; however, they fail in the immunosurveillance of tumors. In previous decades, scientists began studying methods to take advantage of T-cell potency in cancer therapy by redirecting them against tumors independently from the T-cell receptor-defined specificity. Among different approaches, the most promising are the use of bispecific antibodies and T-cell engineering to create chimeric antigen receptors. Bispecific antibodies, by simultaneously recognizing target antigen and an activating receptor on the surface of an immune effector cell, offer an opportunity to redirect immune effector cells to kill cancer cells. The other approach is the generation of chimeric antigen receptors by fusing extracellular antibodies to intracellular signaling domains. Chimeric antigen receptor-engineered T cells are able to specifically kill tumor cells in a MHC-independent way. The efficacy of these reagents in different formats has been clinically validated and will be presented here.

Rapid optimization and prototyping for therapeutic antibody-like molecules

Multispecific antibody-like molecules have the potential to advance the standard-of-care in many human diseases. The design of therapeutic molecules in this class, however, has proven to be difficult and, despite significant successes in preclinical research, only one trivalent antibody, catumaxomab, has demonstrated clinical utility. The challenge originates from the complexity of the design space where multiple parameters such as affinity, avidity, effector functions, and pharmaceutical properties need to be engineered in concurrent fashion to achieve the desired therapeutic efficacy. Here, we present a rapid prototyping approach that allows us to successfully optimize these parameters within one campaign cycle that includes modular design, yeast display of structure focused antibody libraries and high throughput biophysical profiling. We delineate this approach by presenting a design case study of MM-141, a tetravalent bispecific antibody targeting two compensatory signaling growth factor receptors: insulin-like growth factor 1 receptor (IGF-1R) and v-erb-b2 erythroblastic leukemia viral oncogene homolog 3 (ErbB3). A MM-141 proof-of-concept (POC) parent molecule did not meet initial design criteria due to modest bioactivity and poor stability properties. Using a combination of yeast display, structured-guided antibody design and library-scale thermal challenge assay, we discovered a diverse set of stable and active anti-IGF-1R and anti-ErbB3 single-chain variable fragments (scFvs). These optimized modules were reformatted to create a diverse set of full-length tetravalent bispecific antibodies. These re-engineered molecules achieved complete blockade of growth factor induced pro-survival signaling, were stable in serum, and had adequate activity and pharmaceutical properties for clinical development. We believe this approach can be readily applied to the optimization of other classes of bispecific or even multispecific antibody-like molecules.

Monoclonal antibodies therapies for ovarian cancer

INTRODUCTION

Despite aggressive debulking surgery, intraperitoneal therapies and the use of new drugs for chemotherapy, patients with ovarian cancer (OC) still have poor prognosis and, therefore, new strategies for its management are needed. Molecular-targeted agents can be considered a new option in drug research. Several antigens related to OC have been isolated and they could be potential target of monoclonal antibodies (mAbs); therefore, different mAbs have been developed and are emerging as new potential OC treatments.

AREAS COVERED

This article aims to review the literature on the use of mAbs in the treatment of OC. The purposes of this manuscript are to offer a brief explanation of the mechanisms of action of mAbs and to help readers in understanding the current role of mAbs in the treatment of OC.

EXPERT OPINION

A deeper knowledge of the molecular biology of OC has brought new developments in targeted therapies. Among these therapies, bevacizumab demonstrated the higher clinical efficacy. Further larger trials are needed to better define the role of the other mAbs in OC treatment. There is a strong need to identify and validate robust biomarkers for a more focused patient selection and for tailoring therapies, optimizing dose and assessing response.

Ovarian cancer stem cells: a new target for cancer therapy

Ovarian cancer is a highly lethal disease among all gynecologic malignancies and is the fifth leading cause of cancer-related death in women. Although the standard combination of surgery and chemotherapy was initially effective in patients with ovarian cancer, disease relapse commonly occurred due to the generation of chemoresistance. It has been reported that cancer stem cells (CSCs) are involved in drug resistance and cancer recurrence. Over the past decades, increasing studies have been done to identify CSCs from human ovarian cancer cells. The present paper will summarize different investigations on ovarian CSCs, including isolation, mechanisms of chemoresistance, and therapeutic approaches. Although there are still numerous challenges to translate basic research to clinical applications, understanding the molecular details of CSCs is essential for developing effective strategies to prevent ovarian cancer and its recurrence.

Medikamentöse Therapie der Peritonealkarzinose

<b><i>Hintergrund:</i></b> Die Behandlung der Peritonealkarzinose ist eine interdisziplinäre medizinische Herausforderung. Betreffend der medikamentösen Therapie fehlt bislang eine Standardisierung. <b><i>Methode:</i></b> Relevante Artikel zum Thema Peritonealkarzinose aus den Datenbanken der U.S. National Library of Medicine (PubMed) sowie der Kongressregister der American Society of Clinical Oncology und der European Society of Medical Oncology wurden durchsucht. Die Bedeutung der Berichte für die klinische Praxis wurde zwischen den Autoren diskutiert und interdisziplinär abgestimmt. Es wurden praxisnahe Folgerungen und Empfehlungen abgeleitet. <b><i>Ergebnisse:</i></b> PubMed weist eine ansteigende Zahl an Publikationen zum Thema Peritonealkarzinose auf. In 2012 wurden 563 Arbeiten unter dem Stichwort abgelegt. Die medikamentöse Therapie der Peritonealkarzinose ist ein Teil der multimodalen Behandlung, zu der die lokalen chirurgischen und physikalischen Therapiemaßnahmen zählen. Die Auswahl der Chemotherapeutika richtet sich nach der entsprechenden malignen Grunderkrankung. Aktuelle zielgerichtete Ansätze wie die anti-angiogene Therapie und die gegen das epitheliale Zelladhäsionsmolekül (EpCAM) gerichtete Immuntherapie ergänzen neuerdings das Behandlungsspektrum bei Peritonealkarzinose und malignem Aszites. <b><i>Schlussfolgerungen:</i></b> Die medikamentöse Behandlung der Peritonealkarzinose bleibt eine medizinische Herausforderung. Die zunehmende Zahl an Publikationen und Studien auf dem Gebiet lässt aber mittlerweile mehr evidenzbasierte Entscheidungen zu. Die interdisziplinäre Abstimmung eines individuellen Behandlungskonzepts bleibt bis auf Weiteres der Goldstandard auch für die medikamentöse Therapie der Peritonealkarzinose.

Catumaxomab: in malignant ascites

Catumaxomab is a rat/murine hybrid, trifunctional, bispecific (anti-human epithelial cell adhesion molecule [EpCAM] × anti-CD3) monoclonal antibody. Compared with paracentesis alone, paracentesis followed by catumaxomab therapy was associated with significant prolongation of paracentesis-free survival and time to repeat paracentesis in a randomized, open-label, multicentre, pivotal phase II/III trial in patients with recurrent symptomatic malignant ascites due to EpCAM-positive tumours who were resistant to conventional chemotherapy. The benefits of catumaxomab were seen across a broad range of epithelial ovarian and nonovarian cancers, and irrespective of whether or not catumaxomab recipients developed human anti-mouse antibodies. Combining catumaxomab with paracentesis also resulted in more pronounced and prolonged reductions in ascites signs and symptoms and a delayed deterioration in health-related quality of life compared with paracentesis alone. Despite the study not being designed or powered to evaluate overall survival, significant differences favouring the addition of catumaxomab to paracentesis were seen in analyses of the safety population and the subpopulation of patients with gastric cancer. Catumaxomab was generally well tolerated in the pivotal phase II/III trial. The most frequent adverse events attributed to catumaxomab treatment included cytokine-release-related symptoms, which were mostly of mild to moderate severity and manageable with standard symptomatic treatment.

Regression of liver metastases after treatment with intraperitoneal catumaxomab for malignant ascites due to breast cancer

Malignant ascites is quite rare in breast cancer and is mainly associated with a lobular histology. To date, no studies have evaluated locoregional therapy for malignant ascites in breast cancer. The anti-epithelial cell adhesion molecule (EpCAM), trifunctional antibody catumaxomab was approved in the European Union for the intraperitoneal (i.p.) treatment of malignant ascites in patients with EpCAM-positive carcinomas where standard therapy is not available or no longer feasible. We report the case of a 69-year-old female with pretreated breast cancer who received i.p. catumaxomab for the treatment of malignant ascites and showed a regression of liver metastases. The patient originally underwent a left mastectomy and ipsilateral axillary lymph node dissection for an invasive ductal carcinoma in 1995. Following several lines of treatment, she was enrolled in February 2010 in a phase IIIb study (CASIMAS) investigating the safety of a 3-h i.p. catumaxomab infusion. In addition to a local benefit, as shown by an improvement in malignant ascites and a prolongation of the paracentesis-free interval with i.p. catumaxomab, a computed tomography scan, performed some weeks after catumaxomab administration, showed a regression of liver metastases. In addition to a locoregional effect on EpCAM-positive disease, i.p. catumaxomab may also show systemic effects. The use of i.p. catumaxomab for the treatment of malignant ascites due to breast cancer should be explored further in appropriate clinical studies and its possible systemic effects should also be further investigated.

Ganglioside GD2-specific trifunctional surrogate antibody Surek demonstrates therapeutic activity in a mouse melanoma model

BACKGROUND

Trifunctional bispecific antibodies (trAb) are a special class of bispecific molecules recruiting and activating T cells and accessory immune cells simultaneously at the targeted tumor. The new trAb Ektomab that targets the melanoma-associated ganglioside antigen GD2 and the signaling molecule human CD3 (hCD3) on T cells demonstrated potent T-cell activation and tumor cell destruction in vitro. However, the relatively low affinity for the GD2 antigen raised the question of its therapeutic capability. To further evaluate its efficacy in vivo it was necessary to establish a mouse model.

METHODS

We generated the surrogate trAb Surek, which possesses the identical anti-GD2 binding arm as Ektomab, but targets mouse CD3 (mCD3) instead of hCD3, and evaluated its chemical and functional quality as a therapeutic antibody homologue. The therapeutic and immunizing potential of Surek was investigated using B78-D14, a B16 melanoma transfected with GD2 and GD3 synthases and showing strong GD2 surface expression. The induction of tumor-associated and autoreactive antibodies was evaluated.

RESULTS

Despite its low affinity of approximately 10(7) M(-1) for GD2, Surek exerted efficient tumor cell destruction in vitro at an EC(50) of 70 ng/ml [0.47 nM]. Furthermore, Surek showed strong therapeutic efficacy in a dose-dependent manner and is superior to the parental GD2 mono-specific antibody, while the use of a control trAb with irrelevant target specificity had no effect. The therapeutic activity of Surek was strictly dependent on CD4(+) and CD8(+) T cells, and cured mice developed a long-term memory response against a second challenge even with GD2-negative B16 melanoma cells. Moreover, tumor protection was associated with humoral immune responses dominated by IgG2a and IgG3 tumor-reactive antibodies indicating a Th1-biased immune response. Autoreactive antibodies against the GD2 target antigen were not induced.

CONCLUSION

Our data suggest that Surek revealed strong tumor elimination and anti-tumor immunization capabilities. The results warrant further clinical development of the human therapeutic equivalent antibody Ektomab.

Biodistribution studies with tumor-targeting bispecific antibodies reveal selective accumulation at the tumor site

Bispecific antibodies are proteins that bind two different antigens and may retarget immune cells with a binding moiety specific for a leukocyte marker. A binding event in blood could in principle prevent antibody extravasation and accumulation at the site of disease. In this study, we produced and characterized two tetravalent bispecific antibodies that bind with high affinity to the alternatively-spliced EDB domain of fibronectin, a tumor-associated antigen. The bispecific antibodies simultaneously engaged the cognate antigens (murine T cell co-receptor CD3 and hen egg lysozyme) and selectively accumulated on murine tumors in vivo. The results, which were in agreement with predictions based on pharmacokinetic modeling and antibody binding characteristics, confirmed that bispecific antibodies can reach abluminal targets without being blocked by peripheral blood leukocytes.

Molecular characterization of novel trispecific ErbB-cMet-IGF1R antibodies and their antigen-binding properties

Therapeutic antibodies are well established drugs in diverse medical indications. Their success invigorates research on multi-specific antibodies in order to enhance drug efficacy by co-targeting of receptors and addressing key questions of emerging resistance mechanisms. Despite challenges in production, multi-specific antibodies are potentially more potent biologics for cancer therapy. However, so far only bispecific antibody formats have entered clinical phase testing. For future design of antibodies allowing even more targeting specificities, an understanding of the antigen-binding properties of such molecules is crucial. To this end, we have generated different IgG-like TriMAbs (trispecific, trivalent and tetravalent antibodies) directed against prominent cell surface antigens often deregulated in tumor biology. A combination of surface plasmon resonance and isothermal titration calorimetry techniques enables quantitative assessment of the antigen-binding properties of TriMAbs. We demonstrate that the kinetic profiles for the individual antigens are similar to the parental antibodies and all antigens can be bound simultaneously even in the presence of FcγRIIIa. Furthermore, cooperative binding of TriMAbs to their antigens was demonstrated. All antibodies are fully functional and inhibit receptor phosphorylation and cellular growth. TriMAbs are therefore ideal candidates for future applications in various therapeutic areas.

Deterioration in quality of life (QoL) in patients with malignant ascites: results from a phase II/III study comparing paracentesis plus catumaxomab with paracentesis alone

BACKGROUND

Malignant ascites (MA) is associated with poor prognosis and limited palliative therapeutic options. Therefore, quality of life (QoL) assessment is of particular importance to demonstrate new treatment value. Following the demonstration of the superiority of catumaxomab and paracentesis over paracentesis on puncture-free survival, this analysis aimed at comparing deterioration in QoL between both the treatment options.

PATIENTS AND METHODS

In a randomised, multicentre, phase II/III study of patients with MA due to epithelial cell adhesion molecule (EpCAM) positive cancer, the QoL was evaluated using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 items (EORTC QLQ-C30) questionnaire at screening, 1, 3 and 7 months after treatment and in the case of re-puncture on the day of paracentesis. Time to first deterioration in QoL was defined as a decrease in the QoL score of at least five points and compared between the catumaxomab (n=160) and control (n=85) groups using the log-rank test and Cox proportional hazards models adjusted for baseline score, country and primary tumour type.

RESULTS

Deterioration in QoL scores appeared more rapidly in the control than in the catumaxomab group (median 19-26 days versus 47-49 days). The difference in time to deterioration in QoL between the groups was statistically significant for all scores (P<0.01). The hazard ratios ranged from 0.08 to 0.24 (P<0.01).

CONCLUSIONS

Treatment with catumaxomab delayed deterioration in QoL in patients with MA. Compared with paracentesis alone, catumaxomab enabled patients to benefit from better QoL for a prolonged survival period.

Transient lymphocyte decrease due to adhesion and migration following catumaxomab (anti-EpCAM x anti-CD3) treatment in vivo

Introduction

In patients, a transient decrease in peripheral blood lymphocyte counts was observed following intraperitoneal administration of the trifunctional monoclonal antibody catumaxomab (anti-human EpCAM x anti-human CD3). The aim of this study was to clarify the observed effect in a preclinical mouse model and to analyse the related mechanism of action in vitro.

Materials and methods

A related antibody, BiLu (antihuman EpCAM x anti-mouse CD3), was administered to mice and blood leukocytes were analysed. In vitro studies measured activation and cytokine secretion from human peripheral blood mononuclear cells (PBMC). For the analysis of T cell adhesion, PBMC were preincubated with catumaxomab and then co-cultured with human endothelial cells (HUVEC); T cell adhesion was assessed in the presence or absence of endothelial cell preactivation by TNFα. Adherent T cells were determined by flow cytometry.

Results

Treatment of mice with BiLu resulted in a dosedependent transient decrease in CD3+ T cells (both CD4+ and CD8+) that returned to the normal range within 48 h. Catumaxomab physiologically activated T cells in vitro (increased CD69 expression) and induced cytokine release (TNFα, IFNγ). TNFα increased expression of adhesion molecules CD54 and CD62E on endothelial cells. Furthermore, catumaxomab dose-dependently enhanced adhesion of T cells to endothelial cells. Adhesion was further increased when endothelial cells were preactivated with TNFα.

Conclusions

Catumaxomab increases adhesion of T cells to endothelial cells due to antibody-mediated activation of T cells and production of T cell cytokines that up-regulate endothelial cell adhesion molecules. These results provide a mechanistic rationale for the transient, reversible decrease in lymphocyte counts observed following catumaxomab administration in patients, which is likely to be due to redistribution of lymphocytes.

Dendritic cell therapy in advanced gastric cancer: a promising new hope?

Advanced gastric cancer carries a very poor prognosis when the tumor becomes unresectable. Even with the best currently available chemotherapy regimens the survival rate remains dismal. A recent breakthrough in the treatment paradigm has been the approval of trastuzumab, a monoclonal antibody, in HER2-positive metastatic gastric cancer. A large number of trials are underway using dendritic cells (DCs) in a number of human malignancies and do show a ray of hope in management of these patients. This review attempts to summarize tumor immunology and the current data regarding use of DCs in gastric cancer therapy.

Malignant ascites: pathophysiology and treatment

Malignant ascites (MA) accompanies a variety of abdominal and extra-abdominal tumors. It is a primary cause of morbidity and raises several treatment challenges. MA has several symptoms, producing a significant reduction in the patient's quality of life: loss of proteins and electrolyte disorders cause diffuse oedema, while the accumulation of abdominal fluid facilitates sepsis. Treatment options include a multitude of different procedures with limited efficacy and some degree of risk. A Pubmed, Medline, Embase, and Cochrane Library review of medical, interventional and surgical treatments of MA has been performed. Medical therapy, primarily paracentesis and diuretics, are first-line treatments in managing MA. Paracentesis is widely adopted but it is associated with significant patient discomfort and several risks. Diuretic therapy is effective at the very beginning of the disease but efficacy declines with tumor progression. Intraperitoneal chemotherapy, targeted therapy, immunotherapy and radioisotopes are promising medical options but their clinical application is not yet completely elucidated, and further investigations and trials are necessary. Peritoneal-venous shunts are rarely used due to high rates of early mortality and complications. Laparoscopy and hyperthermic intraperitoneal chemotherapy (HIPEC) have been proposed as palliative therapy. Literature on the use of laparoscopic HIPEC in MA includes only reports with small numbers of patients, all showing successful control of ascites. To date, none of the different options has been subjected to evidence-based clinical trials and there are no accepted guidelines for the management of MA.

Anti-EGFR biparatopic-SEED antibody has enhanced combination-activity in a single molecule

Certain combinations of non-competitive anti-EGFR antibodies have been reported to produce new effects on cells compared to either antibody used separately. New and enhanced combination-activity includes increased inhibition of signaling, increased receptor internalization and degradation, reduced proliferation of tumor cell lines and induction of complement-dependent cytotoxicity (CDC) effector function. To test requirements and mechanisms to elicit enhanced combination-activity with different EGFR binding domains, we created an anti-EGFR biparatopic antibody. A biparatopic antibody interacts through two different antigen-binding sites to a single antigen. A heterodimeric antibody with one binding domain derived from the C225 antibody and one binding domain derived from the humanized 425 (hu425) antibody was built on the strand-exchange engineered domain (SEED) scaffold. This anti-EGFR biparatopic-SEED antibody was compared to parental antibodies used alone and in combination, and to the corresponding monovalent anti-EGFR-SEED antibodies used alone or in combination. We found that the anti-EGFR biparatopic-SEED had enhanced activity, similar to the combination of the two parental antibodies. Combinations of monovalent anti-EGFR-SEED antibodies did not produce enhanced effectiveness in cellular assays. Our results show that the anti-EGFR biparatopic antibody created using the SEED scaffold has enhanced combination-activity in a single molecule. Furthermore, these data suggest that the potential to cross-link the two different epitopes is an important requirement in the mechanism of enhanced combination-activity.

Dual targeting strategies with bispecific antibodies

Monoclonal antibodies are widely used for the treatment of cancer, inflammatory and infectious diseases and other disorders. Most of the marketed antibodies are monospecific and therefore capable of interacting and interfering with a single target. However, complex diseases are often multifactorial in nature, and involve redundant or synergistic action of disease mediators or upregulation of different receptors, including crosstalk between their signaling networks. Consequently, blockade of multiple, different pathological factors and pathways may result in improved therapeutic efficacy. This result can be achieved by combining different drugs, or use of the dual targeting strategies applying bispecific antibodies that have emerged as an alternative to combination therapy. This review discusses the various dual targeting strategies for which bispecific antibodies have been developed and provides an overview of the established bispecific antibody formats.

Therapeutic application of monoclonal antibodies in cancer: advances and challenges

INTRODUCTION

Monoclonal antibody (mAb)-based products are highly specific for a particular antigen. This characteristic feature of the molecules makes them an ideal tool for many applications including cancer diagnosis and therapy.

SOURCES OF DATA

We performed comprehensive searches of PubMed, Medline and the Food and Drug Administration website using keywords such as 'therapeutic antibodies' and 'anti-cancer antibodies'.

AREAS OF AGREEMENT

Treatment of cancer patients with antibodies when used alone or in combination with chemotherapy and radiotherapy, or conjugated to drugs or radioisotopes, prolongs overall survival in cancer patients. Currently, there are 14 mAb-based drugs that have been approved for the treatment of cancer patients.

AREAS OF CONTROVERSY

The response of cancer patients to antibody therapy can be of short duration. Therapeutic antibodies are expensive and may have side effects. There are no reliable predictive biomarkers for sensitivity or resistance to certain therapeutic antibodies. FUTURE FOCUS: There should be additional studies to discover novel therapeutic targets, to develop more effective antibody-based drugs with fewer side effects, to identify more reliable predictive biomarker(s) for response to therapy with antibody-based drugs and to develop alternative strategies (e.g. transgenic plants, transgenic farm animals) for production of large quantities and more affordable batches of therapeutic antibodies.

AREAS TIMELY FOR DEVELOPING RESEARCH

A better understanding of cancer biology, the hallmarks of human cancers and the immune system would lead to identification of additional cell surface biomarkers. These in turn would facilitate the development of novel and biosimilar antibody-based drugs and their routine use as 'magic bullets' for the targeted therapy of human cancers.

Immunomonitoring results of a phase II/III study of malignant ascites patients treated with the trifunctional antibody catumaxomab (anti-EpCAM x anti-CD3)

Patients with malignant ascites secondary to primary carcinomas benefit from intraperitoneal therapy with the trifunctional antibody catumaxomab (anti-EpCAM × anti-CD3). Here, we report the analysis of peritoneal fluid samples from 258 patients with malignant ascites randomized to catumaxomab or control groups to investigate the molecular effects of catumaxomab treatment. In the catumaxomab group, tumor cell numbers and peritoneal levels of VEGF decreased, whereas the activation status of CD4(+) and CD8(+) T-cell populations increased more than two-fold after treatment. Notably, CD133(+)/EpCAM(+) cancer stem cells vanished from the catumaxomab samples but not from the control samples. In vitro investigations indicated that catumaxomab eliminated tumor cells in a manner associated with release of proinflammatory Th1 cytokines. Together, our findings show that catumaxomab therapy activates peritoneal T cells and eliminates EpCAM(+) tumor cells, establishing a molecular and cellular basis to understand in vivo efficacy within the immunosuppressed malignant ascites tissue microenvironment.

Therapeutic assessment of SEED: a new engineered antibody platform designed to generate mono- and bispecific antibodies

The strand-exchange engineered domain (SEED) platform was designed to generate asymmetric and bispecific antibody-like molecules, a capability that expands therapeutic applications of natural antibodies. This new protein engineered platform is based on exchanging structurally related sequences of immunoglobulin within the conserved CH3 domains. Alternating sequences from human IgA and IgG in the SEED CH3 domains generate two asymmetric but complementary domains, designated AG and GA. The SEED design allows efficient generation of AG/GA heterodimers, while disfavoring homodimerization of AG and GA SEED CH3 domains. Using a clinically validated antibody (C225), we tested whether Fab derivatives constructed on the SEED platform retain desirable therapeutic antibody features such as in vitro and in vivo stability, favorable pharmacokinetics, ligand binding and effector functions including antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. In addition, we tested SEED with combinations of binder domains (scFv, VHH, Fab). Mono- and bivalent Fab-SEED fusions retain full binding affinity, have excellent biochemical and biophysical stability, and retain desirable antibody-like characteristics conferred by Fc domains. Furthermore, SEED is compatible with different combinations of Fab, scFv and VHH domains. Our assessment shows that the new SEED platform expands therapeutic applications of natural antibodies by generating heterodimeric Fc-analog proteins.

Humoral response to catumaxomab correlates with clinical outcome: results of the pivotal phase II/III study in patients with malignant ascites

The trifunctional antibody catumaxomab is a targeted immunotherapy for the intraperitoneal treatment of malignant ascites. In a Phase II/III trial in cancer patients (n = 258) with malignant ascites, catumaxomab showed a clear clinical benefit vs. paracentesis and had an acceptable safety profile. Human antimouse antibodies (HAMAs), which could be associated with beneficial humoral effects and prolonged survival, may develop against catumaxomab as it is a mouse/rat antibody. This post hoc analysis investigated whether there was a correlation between the detection of HAMAs 8 days after the fourth catumaxomab infusion and clinical outcome. HAMA-positive and HAMA-negative patients in the catumaxomab group and patients in the control group were analyzed separately for all three clinical outcome measures (puncture-free survival, time to next puncture and overall survival) and compared to each other. There was a strong correlation between humoral response and clinical outcome: patients who developed HAMAs after catumaxomab showed significant improvement in all three clinical outcome measures vs. HAMA-negative patients. In the overall population in HAMA-positive vs. HAMA-negative patients, median puncture-free survival was 64 vs. 27 days (p < 0.0001; HR 0.330), median time to next therapeutic puncture was 104 vs. 46 days (p = 0.0002; HR 0.307) and median overall survival was 129 vs. 64 days (p = 0.0003; HR 0.433). Similar differences between HAMA-positive and HAMA-negative patients were seen in the ovarian, nonovarian and gastric cancer subgroups. In conclusion, HAMA development may be a biomarker for catumaxomab response and patients who developed HAMAs sooner derived greater benefit from catumaxomab treatment.

Concentrations of EpCAM ectodomain as found in sera of cancer patients do not significantly impact redirected lysis and T-cell activation by EpCAM/CD3-bispecific BiTE antibody MT110

Ectodomains of target antigens for antibody-based therapies can be shed from the target cell surface and found in sera of patients. Shed ectodomains of therapeutic targets not only pose the risk of sequestering therapeutic antibodies but, in a multimeric form, of triggering T cell activation by bispecific antibodies binding to CD3 on T cells. Recently, epithelial cell adhesion molecule (EpCAM) has been shown to be activated by release of its ectodomain, called EpEX. Here, we show that only very low amounts of EpEX are detectable in sera of cancer patients. Among 100 cancer patient samples tested, only 17 (17%) showed serum levels of EpEX in excess of 0.05 ng/ml with highest EpEX concentrations of 5.29, 1.37 and 0.52 ng/ml. A recombinant form of human EpEX (recEpEX) was produced to assess its possible effect on redirected lysis and T cell activation by EpCAM/CD3-bispecific BiTE antibody MT110, currently being tested in patients with solid tumor malignancies. RecEpEX had a very minor effect on redirected lysis by MT110 with an approximate IC 50 value of 3,000 ng/ml, which is a concentration close to three orders of magnitude higher than the highest EpEX concentration found in cancer patients. Concentrations of 30 ng/ml EpEX in combination with 250 ng/ml MT110 were minimally required to induce a detectable activation of CD4 (+) and CD8 (+) T cells. We conclude that soluble EpEX in sera of cancer patients is unlikely to pose an issue for the efficacy or safety of MT110, and perhaps other antibodies binding to N-terminal epitopes of EpCAM.

Transiently redirected T cells for adoptive transfer

BACKGROUND AIMS

T cells can be redirected to reject cancer by retroviral transduction with a chimeric antigen receptor (CAR) or by administration of a bispecific T cell engager (BiTE). We demonstrate that transfection of T cells with messenger (m) RNA coding for CAR is an alternative strategy.

METHODS

We describe the pre-clinical evaluation of a method based on transient modification of expanded T cells with a CD19 CAR directed against B-cell malignancies. CAR mRNA was generated under cell-free conditions in a scalable process using recombinant RNA polymerase. Efficient and non-toxic square-wave electroporation was used to load the mRNA into the cytoplasm of T cells with no risk of insertional mutagenesis.

RESULTS

After transfection >80% of T cells were viable, with 94% CAR expression. Transfected T cells were cytolytic to CD19(+) targets and produced interferon (IFN)-γ in response. Killing of CD19(+) target cells was demonstrated even at day 8 with undetectable CAR expression. Increasing the concentration of mRNA resulted in higher surface CAR expression, better killing and more IFN-γ release but at the expense of increased activation-induced cell death. Finally, we demonstrated that a second transgene could be introduced by co-electroporation of CXCR4 or CCR7 with CAR to also modify chemotactic responses.

CONCLUSIONS

We advocate the transient redirection approach as well suited to meet safety aspects for early phase studies, prior to trials using stably transduced cells once CAR has been proven safe. The simplicity of this methodology also facilitates rapid screening of candidate targets and novel receptors in pre-clinical studies.

Have we overestimated the benefit of human(ized) antibodies?

The infusion of animal-derived antibodies has been known for some time to trigger the generation of antibodies directed at the foreign protein as well as adverse events including cytokine release syndrome. These immunological phenomena drove the development of humanized and fully human monoclonal antibodies. The ability to generate human(ized) antibodies has been both a blessing and a curse. While incremental gains in the clinical efficacy and safety for some agents have been realized, a positive effect has not been observed for all human(ized) antibodies. Many human(ized) antibodies trigger the development of anti-drug antibody responses and infusion reactions. The current belief that antibodies need to be human(ized) to have enhanced therapeutic utility may slow the development of novel animal-derived monoclonal antibody therapeutics for use in clinical indications. In the case of murine antibodies, greater than 20% induce tolerable/negligible immunogenicity, suggesting that in these cases humanization may not offer significant gains in therapeutic utility. Furthermore, humanization of some murine antibodies may reduce their clinical effectiveness. The available data suggest that the utility of human(ized) antibodies needs to be evaluated on a case-by-case basis, taking a cost-benefit approach, taking both biochemical characteristics and the targeted therapeutic indication into account.

ZEB1-responsive genes in non-small cell lung cancer

The epithelial to mesenchymal transition (EMT) is a developmental process enabling epithelial cells to gain a migratory mesenchymal phenotype. In cancer, this process contributes to metastases; however the regulatory signals and mechanistic details are not fully elucidated. Here, we sought to identify the subset of genes regulated in lung cancer by ZEB1, an E-box transcriptional repressor known to induce EMT. Using an Affymetrix-based expression database of 38 non-small cell lung cancer (NSCLC) cell lines, we identified 324 genes that correlated negatively with ZEB1 and 142 that were positively correlated. A mesenchymal gene pattern (low E-cadherin, high Vimentin or N-cadherin) was significantly associated with ZEB1 and ZEB2, but not with Snail, Slug, Twist1 or Twist2. Among eight genes selected for validation, seven were confirmed to correlate with ZEB1 by quantitative real-time RT-PCR in a series of 22 NSCLC cell lines, either negatively (CDS1, EpCAM, ESRP1, ESRP2, ST14) or positively (FGFR1, Vimentin). In addition, over-expression or knockdown of ZEB1 led to corresponding changes in gene expression, demonstrating that these genes are also regulated by ZEB1, either directly or indirectly. Of note, the combined knockdown of ZEB1 and ZEB2 led to apparent synergistic responses in gene expression. Furthermore, these responses were not restricted to artificial settings, since most genes were similarly regulated during a physiologic induction of EMT by TGF-β plus EGF. Finally, the absence of ST14 (matriptase) was linked to ZEB1 positivity in lung cancer tissue microarrays, implying that the regulation observed in vitro applies to the human disease. In summary, this study identifies a new set of ZEB-regulated genes in human lung cancer cells and supports the hypothesis that ZEB1 and ZEB2 are key regulators of the EMT process in this disease.