Characterisation of the new EpCAM-specific antibody HO-3: implications for trifunctional antibody immunotherapy of cancer

Clinical Progresses and Challenges of Bispecific Antibodies for the Treatment of Solid Tumors

In recent years, bispecific antibodies (BsAbs) have emerged as a promising therapeutic strategy against tumors. BsAbs can recruit and activate immune cells, block multiple signaling pathways, and deliver therapeutic payloads directly to tumor sites. This review provides a comprehensive overview of the recent advances in the development and clinical application of BsAbs for the treatment of solid tumors. We discuss the different formats, the unique mechanisms of action, and the clinical outcomes of the most advanced BsAbs in solid tumor therapy. Several studies have also analyzed the clinical progress of bispecific antibodies. However, this review distinguishes itself by exploring the challenges associated with bispecific antibodies and proposing potential solutions. As the field progresses, BsAbs hold promise to redefine cancer treatment paradigms and offer new hope to patients with solid tumors.

Molecular Mechanisms and Potential Rationale of Immunotherapy in Peritoneal Metastasis of Advanced Gastric Cancer

Peritoneal metastasis (PM) is one of the most frequent metastasis patterns of gastric cancer (GC), and the prognosis of patients with PM is very dismal. According to Paget’s theory, disseminated free cancer cells are seeded and survive in the abdominal cavity, adhere to the peritoneum, invade the subperitoneal tissue, and proliferate through angiogenesis. In these sequential processes, several key molecules are involved. From a therapeutic point of view, immunotherapy with chemotherapy combination has become the standard of care for advanced GC. Several clinical trials of newer immunotherapy agents are ongoing. Understanding of the molecular process of PM and the potential rationale of immunotherapy for PM treatment is necessary. Beyond understanding of the molecular aspect of PM, many studies have been conducted on the modality of treatment of PM. Notably, intraperitoneal approaches, including chemotherapy or immunotherapy, have been conducted, because systemic treatment of PM has limitations. In this study, we reviewed the molecular mechanisms and immunologic aspects of PM, and intraperitoneal approaches under investigation for treating PM.

IgG-like Bispecific Antibody CD3×EpCAM Generated by Split Intein Against Colorectal Cancer

Background: Colorectal cancer is a commonly diagnosed cancer with high mortality worldwide. Postoperative recidivation and metastasis still are the main challenges in clinical treatments. Thus, it is urgent to develop new therapies against colorectal cancer. Epithelial Cell Adhesion Molecule (EpCAM) is overexpressed in colorectal cancer cells and strongly associated with cancer development. Bispecific antibody (BsAb) is a kind of promising immunotherapy, which could recognize T cells and cancer cells simultaneously to achieve the anti-tumor effects. Methods: A bispecific antibody targeting EpCAM and CD3 with IgG format was genereated by split intein based on the Bispecific Antibody by Protein Splicing" platform. In vitro, the affinity of CD3×EpCAM BsAb was determined by Biolayer interferometry, its cytotoxicity was detected by LDH release assay, T cell recruitment and activation was detected by Flow Cytometry. In vivo, its pharmacokinetic parameters were detected, and anti-tumor effects were evaluated on the tumor cell xenograft mouse model. Results: The results showed that the CD3×EpCAM BsAb could activate and recruit T cells via binding colorectal cells and T cells, which could lead to more potent cytotoxicity to various colorectal cell lines than its parent EpCAM monoclonal antibody (mAb) in vitro. The CD3×EpCAM BsAb had similar pharmacokinetic parameters with EpCAM mAb and inhibits tumor growth on the SW480 tumor cell xenograft mouse model. Conclusion: The CD3×EpCAM BsAb could be a promising candidate for colorectal cancer treatment.

Removal of EpCAM-positive tumor cells from blood collected during major oncological surgery using the Catuvab device- a pilot study

BACKGROUND

Intraoperative blood salvage (IBS) is regarded as an alternative to allogeneic blood transfusion excluding the risks associated with allogeneic blood. Currently, IBS is generally avoided in tumor surgeries due to concern for potential metastasis caused by residual tumor cells in the erythrocyte concentrate.

METHODS

The feasibility, efficacy and safety aspects of the new developed Catuvab procedure using the bispecific trifunctional antibody Catumaxomab was investigated in an ex-vivo pilot study in order to remove residual EpCAM positive tumor cells from the autologous erythrocyte concentrates (EC) from various cancer patients, generated by a IBS device.

RESULTS

Tumor cells in intraoperative blood were detected in 10 of 16 patient samples in the range of 69-2.6 × 105 but no residual malignant cells in the final erythrocyte concentrates after Catuvab procedure. IL-6 and IL-8 as pro-inflammatory cytokines released during surgery, were lowered in mean 28-fold and 52-fold during the Catuvab procedure, respectively, whereas Catumaxomab antibody was detected in 8 of 16 of the final EC products at a considerable decreased and uncritical residual amount (37 ng in mean).

CONCLUSION

The preliminary study results indicate efficacy and feasibility of the new medical device Catuvab allowing potentially the reinfusion of autologous erythrocyte concentrates (EC) produced by IBS device during oncological high blood loss surgery. An open-label, multicenter clinical study on the removal of EpCAM-positive tumor cells from blood collected during tumor surgery using the Catuvab device is initiated to validate these encouraging results.

Acoustically Detonated Microbubbles Coupled with Low Frequency Insonation: Multiparameter Evaluation of Low Energy Mechanical Ablation

Noninvasive ultrasound surgery can be achieved using focused ultrasound to locally affect the targeted site without damaging intervening tissues. Mechanical ablation and histotripsy use short and intense acoustic pulses to destroy the tissue via a purely mechanical effect. Here, we show that coupled with low-frequency excitation, targeted microbubbles can serve as mechanical therapeutic warheads that trigger potent mechanical effects in tumors using focused ultrasound. Upon low frequency excitation (250 kHz and below), high amplitude microbubble oscillations occur at substantially lower pressures as compared to higher MHz ultrasonic frequencies. For example, inertial cavitation was initiated at a pressure of 75 kPa for a center frequency of 80 kHz. Low frequency insonation of targeted microbubbles was then used to achieve low energy tumor cell fractionation at pressures below a mechanical index of 1.9, and in accordance with the Food and Drug Administration guidelines. We demonstrate these capabilities in vitro and in vivo. In cell cultures, cell viability was reduced to 16% at a peak negative pressure of 800 kPa at the 250 kHz frequency (mechanical index of 1.6) and to 10% at a peak negative pressure of 250 kPa at a frequency of 80 kHz (mechanical index of 0.9). Following an intratumoral injection of targeted microbubbles into tumor-bearing mice, and coupled with low frequency ultrasound application, significant tumor debulking and cancer cell death was observed. Our findings suggest that reducing the center frequency enhances microbubble-mediated mechanical ablation; thus, this technology provides a unique theranostic platform for safe low energy tumor fractionation, while reducing off-target effects.

First time intravesically administered trifunctional antibody catumaxomab in patients with recurrent non-muscle invasive bladder cancer indicates high tolerability and local immunological activity

Transurethral resection of the tumor (TUR-B) followed by adjuvant intravesical treatment with cytostatic drugs or Bacillus Calmette–Guérin (BCG) as standard therapy of non-muscle-invasive bladder cancer (NMIBC) is associated with a high recurrence rate of about 60–70%, considerable side effects and requires close monitoring. Alternative treatment options are warranted. Two patients with epithelial cell adhesion molecule (EpCAM)-positive recurrent non-muscle invasive bladder cancer were treated the first time by an intravesical administration of the trifunctional bispecific EpCAM targeting antibody catumaxomab (total dosage of 470 and 1120 µg, respectively). The binding and killing activity of catumaxomab in urine milieu was evaluated in vitro. In contrast to its previous systemic application catumaxomab was well tolerated without any obvious signs of toxicity. Relevant cytokine plasma levels were not detected and no significant systemic drug release was observed. The induction of a human anti-mouse-antibody (HAMA) reaction was either absent or untypically weak contrary to the high immunogenicity of intraperitoneal applied catumaxomab. Tumor cells that were detectable in urine patient samples disappeared after catumaxomab therapy. Endoscopically confirmed recurrence-free intervals were 32 and 25 months. Our data suggest that intravesical administration of catumaxomab in NMIBC is feasible, safe and efficacious, thus arguing for further clinical development of catumaxomab in this indication.

Current Development of Monoclonal Antibodies in Cancer Therapy

Exploiting the unique specificity of monoclonal antibodies has revolutionized the treatment and diagnosis of haematological and solid organ malignancies; bringing benefit to millions of patients over the past decades. Recent achievements include conjugating antibodies with toxic payloads resulting in superior efficacy and/or reduced toxicity, development of molecular imaging techniques targeting specific antigens for use as predictive and prognostic biomarkers, the development of novel bi- and tri-specific antibodies to enhance therapeutic benefit and abrogate resistance and the success of immunotherapy agents. In this chapter, we review an overview of antibody structure and function relevant to cancer therapy and provide an overview of pivotal clinical trials which have led to regulatory approval of monoclonal antibodies in cancer treatment. We further discuss resistance mechanisms and the unique side effects of each class of antibody and provide an overview of emerging therapeutic agents.

Expression of EpCAM in adenoid cystic carcinoma

The mutational landscape of adenoid cystic carcinoma (ACC) is currently being revealed, but further studies are needed to identify biomarkers as therapeutic targets or prognostic factors of ACC. In this study, we investigated the expression of epithelial cell adhesion molecule (EpCAM) in ACCs. We retrospectively collected 83 cases of surgically resected ACCs. Using tissue microarray, we conducted immunohistochemical staining using the anti-EpCAM antibody. EpCAM expression was analysed by intensity score and the total immunostaining score. The positivity was 97.6% (81/83 cases), regardless of the intensity score. A higher histological grade (p = 0.006) and specific tumour location (non-salivary gland origin, p = 0.02) showed a correlation with higher EpCAM intensity. Higher EpCAM expression by total immunostaining score was associated with histological grade (p = 0.004), distant metastasis (p = 0.004) and poorer prognosis (overall survival p = 0.015 and progression-free survival p = 0.033). We suggest EpCAM as a candidate prognostic marker and a putative therapeutic target in ACC. Also, ACCs arising from salivary gland and non-salivary gland sites, respectively, might display different pathophysiologies in which EpCAM could play a role.

Early Investigations and Recent Advances in Intraperitoneal Immunotherapy for Peritoneal Metastasis

Peritoneal metastasis (PM) is an advanced stage malignancy largely refractory to modern therapy. Intraperitoneal (IP) immunotherapy offers a novel approach for the control of regional disease of the peritoneal cavity by breaking immune tolerance. These strategies include heightening T-cell response and vaccine induction of anti-cancer memory against tumor-associated antigens. Early investigations with chimeric antigen receptor T cells (CAR-T cells), vaccine-based therapies, dendritic cells (DCs) in combination with pro-inflammatory cytokines and natural killer cells (NKs), adoptive cell transfer, and immune checkpoint inhibitors represent significant advances in the treatment of PM. IP delivery of CAR-T cells has shown demonstrable suppression of tumors expressing carcinoembryonic antigen. This response was enhanced when IP injected CAR-T cells were combined with anti-PD-L1 or anti-Gr1. Similarly, CAR-T cells against folate receptor α expressing tumors improved T-cell tumor localization and survival when combined with CD137 co-stimulatory signaling. Moreover, IP immunotherapy with catumaxomab, a trifunctional antibody approved in Europe, targets epithelial cell adhesion molecule (EpCAM) and has shown considerable promise with control of malignant ascites. Herein, we discuss immunologic approaches under investigation for treatment of PM.

Recent advances of bispecific antibodies in solid tumors

Cancer immunotherapy is the most exciting advancement in cancer therapy. Similar to immune checkpoint blockade and chimeric antigen receptor T cell (CAR-T), bispecific antibody (BsAb) is attracting more and more attention as a novel strategy of antitumor immunotherapy. BsAb not only offers an effective linkage between therapeutics (e.g., immune effector cells, radionuclides) and targets (e.g., tumor cells) but also simultaneously blocks two different oncogenic mediators. In recent decades, a variety of BsAb formats have been generated. According to the structure of Fc domain, BsAb can be classified into two types: IgG-like format and Fc-free format. Among these formats, bispecific T cell engagers (BiTEs) and triomabs are commonly investigated. BsAb has achieved an exciting breakthrough in hematological malignancies and promising outcome in solid tumor as showed in various clinical trials. In this review, we focus on the preclinical experiments and clinical studies of epithelial cell adhesion molecule (EpCAM), human epidermal growth factor receptor (HER) family, carcinoembryonic antigen (CEA), and prostate-specific membrane antigen (PSMA) related BsAbs in solid tumors, as well as discuss the challenges and corresponding approaches in clinical application.

Pancreas Adenocarcinoma: Ascites, Clinical Manifestations, and Management Implications

BACKGROUND

Ascites develops in a subset of patients with pancreatic adenocarcinoma (PAC) at presentation or as the disease advances. Limited data exist on the prognostic importance of malignant ascites in PAC. Our hypothesis is that this information will provide an understanding of the natural history and facilitate management decisions.

METHODS

We conducted a retrospective analysis of 180 patients treated at Memorial Sloan Kettering Cancer Center diagnosed between January 1, 2009 and December 31, 2014, with PAC and with ascites either at presentation or that developed during the disease course.

RESULTS

For the 180 patients, the overall survival was 15 months. The time from diagnosis to ascites presentation was 11 months, and the survival time after ascites development was 1.8 months (range, 1.6-2.3 months; 95% confidence interval). Of 62 patients (34%) who had ascitic fluid analyzed, 36 (58%) had positive cytology. Fifty-one (82%) patients had a serum ascites albumin gradient ≥ 1, and 11 (18%) had serum ascites albumin gradient < 1. Sixty-four (36%) patients had their ascites managed solely by serial paracenteses. A total of 116 patients required a catheter; of these, 108 (93%) had a Tenckhoff catheter, 4 (3%) a Pleurx catheter, 4 (3%) a pigtail catheter, and 1 (1%) a Denver catheter. Eight (7%) patients required 2 catheters to be placed, and in 6 (5%), Tenckhoff catheters had to be removed. The main observed complications were spontaneous bacterial peritonitis in 7 (11%) managed with paracenteses versus 26 (23%) who had a catheter placed, catheter malfunction in 8 (7%), and acute renal failure in 6 (3%). After ascites development, 79 (44%) patients received active anti-cancer therapy, and 101 (56%) patients were managed with supportive care alone.

CONCLUSIONS

In patients with PAC who presented with or developed ascites, serial paracenteses and indwelling catheters are common methods used for providing symptomatic relief. The complication rate was higher with indwelling catheters, primarily related to infection (eg, bacterial peritonitis). Overall, ascites has a significantly negative prognostic import with a short median survival.

Intraperitoneal immunotherapy: historical perspectives and modern therapy

Intraperitoneal immunotherapy represents a novel strategy for the management of peritoneal metastases (PM). Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) has remained the gold standard of treatment for patients with PM, yet despite optimal treatment, recurrence rates remain high and long-term survival poor. From Coley's toxins to immune checkpoint inhibitors, the wide variety of anticancer immunotherapeutic strategies are now garnering attention for control of regional disease of the peritoneal cavity. Early studies with vaccine-based therapies, adoptive cell transfer, immune checkpoint inhibitors, and chimeric T cells with tumor-specific antigen receptors (CAR-T cells) are being performed, showing promise for control of peritoneal spread and induction of lasting anticancer immunity. In addition, catumaxomab, a trifunctional antibody, has been approved for intraperitoneal immunotherapy in Europe for the control of malignant ascites in patients with epithelial cell adhesion molecule positive cancers. We review a brief history of immunotherapy and current modalities under investigation for intraperitoneal use in the treatment of PM.

An anti-EpCAM antibody EpAb2-6 for the treatment of colon cancer

Epithelial cell adhesion molecule (EpCAM) is known to be overexpressed in epithelial cancers associated with enhanced malignant potential, particularly colorectal carcinoma (CRC) and head and neck squamous cell carcinoma (HNSCC). However, it is unknown whether progression of malignance can be directly inhibited by targeting EpCAM. Here, we have generated five novel monoclonal antibodies (mAbs) against EpCAM. One of these anti-EpCAM mAbs, EpAb2-6, was found to induce cancer cell apoptosis in vitro, inhibit tumor growth, and prolong the overall survival of both a pancreatic cancer metastatic mouse model and mice with human colon carcinoma xenografts. EpAb2-6 also increases the therapeutic efficacy of irinotecan, fluorouracil, and leucovorin (IFL) therapy in a colon cancer animal model and gemcitabine therapy in a pancreatic cancer animal model. Furthermore, EpAb2-6, which binds to positions Y95 and D96 of the EGF-II/TY domain of EpCAM, inhibits production of EpICD, thereby decreasing its translocation and subsequent signal activation. Collectively, our results indicate that the novel anti-EpCAM mAb can potentially be used for cancer-targeted therapy.

Rendomab B4, a monoclonal antibody that discriminates the human endothelin B receptor of melanoma cells and inhibits their migration

Metastatic melanoma is an aggressive cancer with a poor prognostic, and the design of new targeted drugs to treat melanoma is a therapeutic challenge. A promising approach is to produce monoclonal antibodies (mAbs) against the endothelin B receptor (ETB), which is known to be overexpressed in melanoma and to contribute to proliferation, migration and vasculogenic mimicry associated with invasiveness of this cancer. We previously described rendomab-B1, a mAb produced by DNA immunization. It is endowed with remarkable characteristics in term of affinity, specificity and antagonist properties against human ETB expressed by the endothelial cells, but, surprisingly, had poor affinity for ETB expressed by melanoma cells. This characteristic strongly suggested the existence of a tumor-specific ETB form. In the study reported here, we identified a new mAb, rendomab-B4, which, in contrast to rendomab-B1, binds ETB expressed on UACC-257, WM-266-4 and SLM8 melanoma cells. Moreover, after binding to UACC-257 cells, rendomab-B4 is internalized and colocalizes with the endosomal protein EEA-1. Interestingly, rendomab-B4, despite its inability to compete with endothelin binding, is able to inhibit phospholipase C pathway and migration induced by endothelin. By contrast, rendomab-B4 fails to decrease ERK1/2 phosphorylation induced by endothelin, suggesting a biased effect on ETB. These particular properties make rendomab-B4 an interesting tool to analyze ETB-structure/function and a promising starting point for the development of new immunological tools in the field of melanoma therapeutics.

Capture of Tumor Cells on Anti-EpCAM-Functionalized Poly(acrylic acid)-Coated Surfaces

The presence of tumor cells in blood is predictive of short survival in several cancers and their isolation and characterization can guide toward the use of more effective treatments. These circulating tumor cells (CTC) are, however, extremely rare and require a technology that is sufficiently sensitive and specific to identify CTC against a background of billions of blood cells. Immuno-capture of cells expressing the epithelial cell adhesion molecule (EpCAM) are frequently used to enrich CTC from blood. The choice of bio conjugation strategy and antibody clone is crucial for adequate cell capture but is poorly understood. In this study, we determined the binding affinity constants and epitope binding of the EpCAM antibodies VU1D-9, HO-3, EpAb3-5, and MJ-37 by surface plasmon resonance imaging (SPRi). Glass surfaces were coated using a poly(acrylic acid) based coating and functionalized with anti-EpCAM antibodies. Binding of cells from the breast carcinoma cell line (SKBR-3) to the functionalized surfaces were compared. Although EpAb3-5 displayed the highest binding affinity HO-3 captured the highest amount of cells. Hence we report differences in the performance of the different antibodies and more importantly that the choice of antibody to capture CTC should be based on multiple assays.

Characterization of the first-in-class T-cell-engaging bispecific single-chain antibody for targeted immunotherapy of solid tumors expressing the oncofetal protein claudin 6

The fetal tight junction molecule claudin 6 (CLDN6) is virtually absent from any normal tissue, whereas it is aberrantly and frequently expressed in various cancers of high medical need. We engineered 6PHU3, a T-cell-engaging bispecific single chain molecule (bi-(scFv)₂) with anti-CD3/anti-CLDN6 specificities, and characterized its pharmacodynamic properties. Our data show that upon engagement by 6PHU3, T cells strongly upregulate cytotoxicity and activation markers, proliferate and acquire an effector phenotype. 6PHU3 exerts potent killing of cancer cells in vitro with EC₅₀ values in the pg/mL range. Subcutaneous xenograft tumors in NSG mice engrafted with human PBMCs are eradicated by 6PHU3 treatment and survival of mice is significantly prolonged. Tumors of 6PHU3-treated mice are strongly infiltrated with activated CD4⁺, CD8⁺ T cells and T_EM type cells but not T_regs and display a general activation of a mostly inflammatory phenotype. These effects are only observed upon bispecific but not monospecific engagement of 6PHU3. Together with the exceptionally cancer cell selective expression of the oncofetal tumor marker CLDN6, this provides a safeguard with regard to toxicity. In summary, our data shows that the concept of T-cell redirection combined with that of highly selective targeting of CLDN6-positive solid tumors is effective. Thus, exploring 6PHU3 for clinical therapy is warranted.

Mechanisms of action of therapeutic antibodies for cancer

The therapeutic utility of antibodies and their derivatives is achieved by various means. The FDA has approved several targeted antibodies that disrupt signaling of various growth factor receptors for the treatment of a number of cancers. Rituximab, and other anti-CD20 monoclonal antibodies are active in B cell malignancies. As more experience has been gained with anti-CD20 monoclonal antibodies, the multifactorial nature of their anti-tumor mechanisms has emerged. Other targeted antibodies function to dampen inhibitory checkpoints. These checkpoint inhibitors have recently achieved dramatic results in several cancers, including melanoma. These and related antibodies continue to be investigated in the clinical and pre-clinical settings. Novel antibody structures that target two or more antigens have also made their way into clinical use. Tumor targeted antibodies can also be conjugated to chemo- or radiotherapeutic agents, or catalytic toxins, as a means to deliver toxic payloads to cancer cells. Here we provide a review of these mechanisms and a discussion of their relevance to current and future clinical applications.

Outpatient Intraperitoneal Catumaxomab Therapy for Malignant Ascites Related to Advanced Gynecologic Neoplasms

BACKGROUND

Catumaxomab (CATU) is a trifunctional antibody approved for intraperitoneal (i.p.) treatment of malignant ascites (MA) related to carcinomas expressing the epithelial cell-adhesion molecule (EpCAM). CATU is mostly given to hospitalized patients, although outpatient treatment seems appropriate in selected individuals. This observational trial sought to obtain more detailed information regarding the feasibility of CATU in outpatients with MA related to various gynecologic tumors, including epithelial ovarian (EOC) and metastatic breast cancer (MBC).

MATERIALS AND METHODS

A total of 30 patients were included, 17 with EOC, 7 with MBC, and 6 with other malignancies. The patients had failed a median of 5 (range 1-12) previous systemic treatments. CATU was administered via an indwelling i.p. catheter at four increasing doses (i.e., 10, 20, 50, and 150 µg) given at 4-day intervals over 2 weeks. Toxicities were scored according to the Common Terminology Criteria for Adverse Events, version 4.03. Puncture-free survival (PuFS) was calculated from the start of CATU until the next puncture for MA, death, or loss to follow-up. Overall survival (OS) was calculated from the start of CATU to death from any reason or loss to follow-up. We also investigated various clinical parameters to predict PuFS and OS. These included age, tumor type, performance status, intensity of pretreatment, presence of extraperitoneal metastases, relative lymphocyte count at baseline, patient adherence to therapy, and the patients' ability to undergo systemic treatment after CATU.

RESULTS

CATU was exclusively given on an outpatient basis, and 19 patients (63.3%) received all four planned i.p. instillations. Toxicity was the reason for discontinuation in only 2 patients. Toxicity was generally manageable, with abdominal pain, nausea/vomiting, fatigue, and fever the predominant adverse effects. Secondary hospitalization was necessary for 7 patients (23.3%), with a general deteriorated condition in 5 and fever/infection or abdominal pain in 1 patient each. Subsequent systemic treatment was possible in 11 patients (36.7%). Only 5 patients (16.7%) required a second puncture after i.p. CATU. The median PuFS was 56 days, and the median OS was 79.5 days. Positive predictors of both PuFS and OS were performance status, absence of extraperitoneal tumor, the capability to receive all four CATU infusions, and the ability to undergo subsequent systemic treatment.

CONCLUSION

Outpatient i.p. CATU therapy for MA related to various gynecologic carcinomas is safe and effective in producing good ascites control in most individuals, allowing for subsequent systemic therapy in a substantial proportion of patients.

IMPLICATIONS FOR PRACTICE

Intraperitoneal treatment with the trifunctional antibody catumaxomab (CATU) was possible in a selected population of 30 outpatients with malignant ascites due to epithelial female genital tract or breast carcinoma. Toxicity was largely manageable. Patients in good condition at baseline, without extraperitoneal tumor and/or liver metastases, and with the ability to complete all four planned CATU instillations and the capability of undergoing subsequent systemic therapy benefited the most in terms of both puncture-free and overall survival. Outpatient i.p. CATU is safe and effective in a selected group of patients with malignant ascites due to various gynecologic malignancies and could be cost-saving compared with an inpatient approach.

Single nucleotide polymorphisms of the EpCAM-coding gene TACSTD1 in patients with ovarian cancer and their potential translational aspects

PURPOSE

EpCAM is overexpressed in many neoplasms including ovarian cancer. We screened the EpCAM-coding gene TACSTD1 for single nucleotide polymorphisms (SNPs), which could alter ovarian cancer risk, impact upon disease progression, or alter binding of the therapeutic EpCAM-binding antibody, catumaxomab.

METHODS

DNA fragments of 10 healthy volunteers were analyzed to identify SNPs. Subsequently, DNA of ovarian cancer patients (n = 117) and age-matched healthy controls (n = 115) was genotyped by restriction fragment length polymorphism and pyrosequencing. TACSTD1 genotypes 4461T>C were cloned into a gene expression vector; Hek293 cells were subsequently used for stable transfection. FACS analysis of the transfected Hek293 cells was conducted with HO-3-the EpCAM binding site of catumaxomab-to determine antibody binding.

RESULTS

One SNP was detected in exon 3 (4461T>C; rs1126497), resulting in an amino acid exchange at position 115 (Met115Thr). Another polymorphism was found in the 3'UTR (17225A>G; rs1421). Genotyping of patients and controls for these SNPs did not reveal significant differences in genotype distribution. Regarding 17225A>G, the homozygous AA-genotype was associated with diminished progression-free survival (PFS; p = 0.032). Overall survival, FIGO-stage, grading, and age did not differ significantly between genotypes. FACS analysis of transfected Hek293 cells overexpressing EpCAM 115Met/Thr showed binding of HO-3 to both proteins.

CONCLUSIONS

The AA-genotype of 17225A>G seems to be associated with diminished PFS in ovarian cancer patients. The amino acid exchange resulting from 4461T>C does not appear to alter binding of HO-3, suggesting that treatment with catumaxomab can be offered to patients regardless of their TACSTD1-genotype.

Immunological changes in the ascites of cancer patients after intraperitoneal administration of the bispecific antibody catumaxomab (anti-EpCAM×anti-CD3)

OBJECTIVE

To explore the effects of intraperitoneal (i.p.) infusion of catumaxomab, a bispecific monoclonal antibody (anti-EpCAM×anti-CD3), on T cells, NK cells and macrophages in ascites of cancer patients and to understand how ascitic immune cells can be activated despite the pervasive immunosuppressive ability of ascites microenvironment.

METHODS

Six patients with malignant ascites received i.p. catumaxomab infusion. Ascitic immune cells were profiled by flow cytometry and gene expression at baseline and after i.p. catumaxomab infusion. In vitro experiments enabled investigations on the adverse effect of ascites microenvironment on catumaxomab-stimulated immune cells.

RESULTS

I.p. catumaxomab infusion enhanced the expression of the CD69 and CD38 activation molecules in CD4(+) and CD8(+) T cells, NK cells and macrophages, and favoured CD8(+) T cell accumulation into the peritoneal cavity. An analogous immune cell activation as well as IFN-γ and IL-2 production were induced by catumaxomab in vitro. In vitro experiments showed that the immunosuppressive milieu of ascites abrogated all the immunostimulatory activities of catumaxomab. Adding EpCAM(+) tumour cells to the culture permitted both catumaxomab Fab regions to engage cognate antigens and restored immunostimulatory catumaxomab activity.

CONCLUSIONS

This is the first demonstration in a clinical setting that i.p. catumaxomab infusion activates NK cells and macrophages in addition to T cells in ascites and favours CD8(+) T cell accumulation into the peritoneal cavity. Moreover, our findings indicate that the concomitant binding of both catumaxomab Fab regions delivers an activation signal that is strong enough to activate immune cells despite the prevailing immunosuppressive environment of malignant ascites.

Cell surface markers of cancer stem cells: diagnostic macromolecules and targets for drug delivery

The recognition that the persistence of cancer stem cells (CSCs) in patients following chemotherapy can result in disease relapse underscores the necessity to develop therapeutics against those cells. CSCs display a unique repertoire of cell surface macromolecules, which have proven essential for their characterization and isolation. Additionally, CSC-specific cell surface macromolecules or markers provide targets for the development of specific agents to destroy them. In this review, we compiled those cell surface molecules that have been validated as CSC markers for many common blood and solid tumors. We describe the unique chemical and structural features of the most common cell surface markers, as well as recent efforts to deliver chemotherapeutic agents into CSCs by targeting those macromolecules.

Targeted immune therapy of ovarian cancer

Clinical outcomes, such as recurrence-free survival and overall survival, in ovarian cancer are quite variable, independent of common characteristics such as stage, response to therapy, and grade. This disparity in outcomes warrants further exploration and therapeutic targeting into the interaction between the tumor and host. One compelling host characteristic that contributes both to the initiation and progression of ovarian cancer is the immune system. Hundreds of studies have confirmed a prominent role for the immune system in modifying the clinical course of the disease. Recent studies also show that anti-tumor immunity is often negated by immune regulatory cells present in the tumor microenvironment. Regulatory immune cells also directly enhance the pathogenesis through the release of various cytokines and chemokines, which together form an integrated pathological network. Thus, in the future, research into immunotherapy targeting ovarian cancer will probably become increasingly focused on combination approaches that simultaneously augment immunity while preventing local immune suppression. In this article, we summarize important immunological targets that influence ovarian cancer outcome as well as include an update on newer immunotherapeutic strategies.

A survey of treatment approaches of malignant ascites in Germany and Austria

BACKGROUND

Malignant ascites (MA) is a common manifestation of advanced cancer. Currently, there are no evidence-based guidelines for the management of MA. We conducted a survey with physicians throughout Germany and Austria, to get an overview of current approaches and opinions in the treatment of MA.

METHODS

One hundred and twenty-eight medical oncologists (MO), gastroenterologists (GE), and gynecologists (GYN) completed an electronic questionnaire consisting of 33 questions.

RESULTS

Ninety percent of the physicians were from Germany and 10% from Austria; 48% of those were MO, 30% were GYN, and 14% were GE. Most physicians treated an average of 34 patients (pts)/year with MA. Twenty-six percent of these pts suffered from ovarian, 20% from pancreatic, 17% from gastric, and 14% from colorectal cancer. The majority of the physicians associated MA with poor prognosis (92%) and significant reduction in quality of life (87%). One third felt that MA was a contraindication for full dosing of systemic chemotherapy. Paracentesis (PC) was performed in 70% of pts with symptom relieve and quality of life being the main reasons. Almost half of the pts required 3-5 PC, 50% even more than 5 PC during the course of their disease. Only 15% of pts needed multiple PC per week; the majority (79%) needed the procedure either once a week or every 14 days. In 61% of pts, 3-5 L of ascites fluid was drained. Only in 8%, 5 L and more were removed. Volume substitution with IV albumin was performed in 40% of pts. Most pts (55%) had to stay 1-3 h in a healthcare facility for the procedure. However, 21% had to stay ≥1 day. While almost all physicians (89%) performed a PC at some point in the treatment of MA, 75% felt that a systemic chemotherapy and 55% thought a concomitant diuretic therapy were a necessary adjunct. Seven percent of the pts received a targeted treatment with catumaxomab.

CONCLUSIONS

Repeated PC is the main pillar of treatment of MA; its effect is only temporary and requires significant hospital resources. Further treatment strategies of MA have to be evaluated in prospective studies. Targeted therapies like catumaxomab and VEGF inhibitors should be integrated into these.

Re-challenge with catumaxomab in patients with malignant ascites: results from the SECIMAS study

Malignant ascites is a common phenomenon in cancer patients. It poses a great challenge to the clinician, because of limited treatment options and strong impairment of the quality of life of the often palliative patients. The SECIMAS study investigated the feasibility of a re-challenge with four catumaxomab intraperitoneal infusions in patients who had already received a first cycle of four infusions in the phase III CASIMAS study, which compared catumaxomab with and without prednisolone premedication. The primary endpoint was the proportion of patients who received at least three catumaxomab infusions. Secondary endpoints included a composite safety score (CSS) summarising the worst grades for the main catumaxomab-related adverse events (pyrexia, nausea, vomiting and abdominal pain), safety, efficacy and the occurrence of anti-drug antibodies (ADAs). Eight of nine screened patients received a second catumaxomab cycle. Compliance with a catumaxomab re-challenge was high: all eight patients (100%) received all four infusions. The median CSS was 3.0 versus 3.4 in CASIMAS. The tolerability profile of the second catumaxomab cycle was comparable to that of the first cycle. Median puncture-free survival (48 days) and overall survival (407 days) were longer than in CASIMAS (35 and 103 days, respectively), although median time to next puncture was shorter (60 vs. 97 days). Of six patients sampled, all were ADA positive at screening and remained ADA positive until the end of the study. The presence of ADAs did not affect catumaxomab's safety or efficacy. The CSS and tolerability profile for catumaxomab in SECIMAS were comparable to those in CASIMAS. The majority of patients benefitted from a second cycle of catumaxomab. A re-challenge seems to be feasible and safe for selected patients with recurrent malignant ascites due to carcinoma after a first cycle of catumaxomab.

Intra- and postoperative catumaxomab in patients with epithelial ovarian cancer: safety and two-year efficacy results from a multicentre, single-arm, phase II study

BACKGROUND

This is the first study investigating the safety and efficacy of the trifunctional antibody catumaxomab administered i.p. at the end of cytoreductive surgery and postoperatively prior to standard chemotherapy in patients with primary epithelial ovarian cancer (EOC).

METHODS

Patients received i.p. catumaxomab 10 μg intraoperatively and 10, 20, 50 and 150 μg on days 7, 10, 13 and 16, respectively, postoperatively. After the study, patients received standard chemotherapy and were followed for 23 months. The primary endpoint was the rate of postoperative complications.

RESULTS

Forty-one patients entered the study and were evaluable for safety and 34 were alive at 24 months. Complete tumour resection rate was 68%. Postoperative complications were observed in 51%, the most common anastomotic leakage (7%) and wound infections (5%). The most common catumaxomab-related adverse events were abdominal pain, nausea, vomiting and pyrexia. Thirty-nine percent discontinued catumaxomab therapy, and 98% received chemotherapy post study. Kaplan-Meier estimates of disease-free and overall survival after 24 months were 56% and 85%, respectively.

CONCLUSIONS

Intra- and close postoperative catumaxomab seems feasible, but efficacy and safety were limited by postsurgical complications. In the future prospective trials are needed to investigate the best schedule of integration of catumaxomab into current treatment strategies for EOC.

Catumaxomab with and without prednisolone premedication for the treatment of malignant ascites due to epithelial cancer: results of the randomised phase IIIb CASIMAS study

This two-arm, randomised, multicentre, open-label, phase IIIb study investigated the safety and efficacy of a 3-h catumaxomab infusion with/without prednisolone premedication to reduce catumaxomab-related adverse events. Patients with malignant ascites due to epithelial cancer received four 3-h intraperitoneal catumaxomab infusions with/without intravenous prednisolone (25 mg) premedication before each infusion. The primary safety endpoint was a composite safety score calculated from the incidence and intensity of the most frequent catumaxomab-related adverse events (pyrexia, nausea, vomiting and abdominal pain). Puncture-free survival (PuFS) was a co-primary endpoint. Time to next puncture (TTPu) and overall survival (OS) were secondary endpoints. Prednisolone premedication did not result in a significant reduction in the main catumaxomab-related adverse events. The mean composite safety score was comparable in both arms (catumaxomab plus prednisolone, 4.1; catumaxomab, 3.8; p = 0.383). Median PuFS (30 vs. 37 days) and TTPu (78 vs. 102 days) were shorter in the catumaxomab plus prednisolone arm than in the catumaxomab arm, but the differences were not statistically significant (p = 0.402 and 0.599, respectively). Median OS was longer in the catumaxomab plus prednisolone arm than in the catumaxomab arm (124 vs. 86 days), but the difference was not statistically significant (p = 0.186). The superiority of catumaxomab plus prednisolone versus catumaxomab alone could not be proven for the primary endpoint. Prednisolone did not result in a significant reduction in the main catumaxomab-related adverse events. The study confirms the safety and efficacy of catumaxomab administered as four 3-h intraperitoneal infusions for the treatment of malignant ascites.

The role of relative lymphocyte count as a biomarker for the effect of catumaxomab on survival in malignant ascites patients: results from a phase II/III study

PURPOSE

We report the role of relative lymphocyte count (RLC) as a potential biomarker with prognostic impact for catumaxomab efficacy and overall survival (OS) based on a post hoc analysis of the pivotal phase II/III study of intraperitoneal catumaxomab treatment of malignant ascites.

EXPERIMENTAL DESIGN

The impact of treatment and RLC on OS was evaluated using multivariate Cox models. Kaplan-Meier and log-rank tests were used for group comparisons. Survival analyses were performed on the safety population [patients with paracentesis plus ≥ 1 dose of catumaxomab (n = 157) and paracentesis alone (n = 88)]. Determination of the optimal cutoff value for RLC was based on five optimality criteria.

RESULTS

OS was significantly longer with catumaxomab versus paracentesis alone (P = 0.0219). The 6-month OS rate with catumaxomab was 28.9% versus 6.7% with paracentesis alone. RLC had a positive impact on OS and was an independent prognostic factor (P < 0.0001). In patients with RLC > 13% (n = 159: catumaxomab, 100 and control, 59), catumaxomab was associated with a favorable effect on OS versus paracentesis alone (P = 0.0072), with a median/mean OS benefit of 41/131 days and an increased 6-month survival rate of 37.0% versus 5.2%, respectively. In patients with RLC ≤ 13% at screening (n = 74: catumaxomab, 50 and control, 24), the median (mean) OS difference between the catumaxomab and the control group was 3 (16) days, respectively (P = 0.2561).

CONCLUSIONS

OS was significantly improved after catumaxomab treatment in patients with malignant ascites. An RLC > 13% at baseline was a significant prognostic biomarker.

Intraperitoneal chemotherapy against peritoneal carcinomatosis: current status and future perspective

Peritoneal carcinomatosis (PC), caused by advanced abdominal malignancies, such as those of the ovarian and gastrointestinal tracts, has an extremely poor prognosis. Intraperitoneal (IP) chemotherapy has been clinically applied for several decades, but its clinical efficacy has not been fully determined. An accumulating body of evidence suggests that cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) is the optimal treatment for selected patients with ovarian and colorectal cancers with PC. Recent studies suggest that IP administration of taxane with systemic chemotherapy in a neoadjuvant setting improves patient survival in gastric cancer with PC. The pharmacokinetics of IP-administered drugs should be primarily considered in order to optimize IP chemotherapy. Therefore, the development of specific IP drugs using newly emerging molecular targeted reagents or new drug delivery systems, such as nanomedicine or controlled absorption/release methods, is essential to improve the efficacy of IP chemotherapy.

EpCAM, a potential therapeutic target for esophageal squamous cell carcinoma

BACKGROUND

Molecular-targeted drugs are not available for esophageal squamous cell carcinoma (ESCC), which has a poor prognosis. We investigated the clinicopathological significance of epithelial cell adhesion molecule (EpCAM) expression and the utility of EpCAM as a potential therapeutic target.

METHODS

The relationship between EpCAM expression and clinicopathological factors was examined by immunohistochemistry in 74 patients with resectable ESCC. A total of ten ESCC cell lines were analyzed for EpCAM expression. The effects of EpCAM knockdown in TE4, TE10, and TE14 cells were examined with regard to cell proliferation and gene expression in vitro and tumor growth in vivo. The antitumor effect of catumaxomab in ESCC cell lines was examined.

RESULTS

EpCAM overexpression was associated with poor survival in ESCC patients (P = 0.026). Multivariate Cox regression analysis showed that EpCAM overexpression was a significant and independent prognostic factor for surgically treated ESCC (P = 0.004). TE4 and TE10 cells showed high EpCAM expression, in contrast to TE14. EpCAM siRNA knockdown in TE4 and TE10 cells downregulated CCND1 and CCNE2 and suppressed cell proliferation. Low EpCAM expression reduced tumorigenesis; TE4 cells initiated tumorigenesis in seven of the ten mice injected, whereas shRNA knockdown resulted in smaller tumors in two of ten mice at 6 weeks after transplantation. Concentration- and time-dependent antitumor effects of catumaxomab were observed in TE4 and TE10 cells.

CONCLUSIONS

EpCAM overexpression is an independent prognostic factor for surgically treated ESCC. EpCAM contributes to cell proliferation and tumorigenesis and may be a useful therapeutic target for ESCC.

Drug development for intraperitoneal chemotherapy against peritoneal carcinomatosis from gastrointestinal cancer

Intraperitoneal (IP) chemotherapy for peritoneal carcinomatosis (PC) from gastrointestinal cancer has been investigated and applied clinically for several decades. Cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy have been considered to be the optimal treatment options for selected patients with colorectal and gastric cancers with PC. Accumulating evidence suggests that the administration of IP paclitaxel for patients with PC from gastric cancer may improve the patient survival. The pharmacokinetics of such treatment should be considered to optimize IP chemotherapy. In addition, newly emerging molecular-targeted therapies and research into new drug delivery systems, such as nanomedicine or controlled absorption/release methods, are essential to improve the effects of IP chemotherapy. This review summarizes the current status and future prospects of IP chemotherapy for the treatment of gastrointestinal cancer.

Relative lymphocyte count is a prognostic parameter in cancer patients with catumaxomab immunotherapy

BACKGROUND

Catumaxomab (anti-EpCAM × anti-CD3) treatment in peritoneal carcinomatosis (PC) of EpCAM-positive cancers was effective in phase I and II studies. Recently, it was approved in the EU for treatment of peritoneal carcinomatosis and malignant ascites. Aim of this hypothesis-generating study was to identify predictive or prognostic biomarkers with relevance for overall survival.

METHODS

34 patients with PC in phase I/II studies with catumaxomab treatment were assessed for age, Karnofsky Index (KI), relative (RLC) and absolute lymphocyte count, relative and absolute granulocyte count, T-cell subsets, NK cells, and monocytes before catumaxomab therapy. Disease control (responder) was defined by stable disease, partial response or complete response (RECIST v1.0) >3 months or survival >6 months. Correlation analysis, Kaplan-Meier curves, ROC calculation, and multivariate regression were used for statistical analysis.

RESULTS

Mean RC values significantly differed between the non-responder (14.0%) and the responder group (23.9%; p=0.001). RLC was correlated with overall survival (p=0.03). RLC of >12% defined by ROC calculation was associated with prolonged survival (p=0.035; hazard ratio of 2.775 for patients with RLC <12%). Patients with RLC >12% showed a mean survival of 15.6 versus 5.6 months in patients with RLC ≥ 12% (p=0.001). Multivariate analysis found the individual RLC before therapy (p=0.039) and the KI performance status (p=0.002) to be independent prognostic parameters. Increasing KI by 1% resulted in a risk decrease of 10.1%. Increasing RLC by 1% resulted in a risk decrease of 4.6%. Age and the extent of PC did not significantly influence survival.

CONCLUSIONS

RLC and KI were identified as potential prognostic parameters for superior disease control and overall survival after catumaxomab treatment. RLC may be used as a biomarker to indicate a suitable immune status for catumaxomab therapy. The predictive impact has to be confirmed in further studies.

Epithelial cell-adhesion molecule-directed trifunctional antibody immunotherapy for symptom management of advanced ovarian cancer

Despite advances in cytotoxic chemotherapy and surgical cytoreduction, disease recurrence continues to be a troubling problem in patients with advanced-stage epithelial ovarian cancer (EOC). Malignant ascites affects approximately 10% of patients with recurrent EOC and is associated with troublesome symptoms, including abdominal pressure, distension, dyspnea, pelvic pain, and bowel/bladder dysfunction. To date, no effective therapy has been identified for the treatment of malignant ascites in patients with recurrent, advanced-stage ovarian cancer. Recently, immune modulation has gained attention as a novel approach to anti-cancer therapy. This review explores the role of epithelial cell-adhesion molecule (EpCAM)-directed immunotherapy, with a specific focus on the mechanism of action of the trifunctional antibody catumaxomab (anti-EpCAM × anti-CD3). In addition, clinical trials exploring the use of catumaxomab in the treatment of malignant ascites in patients with ovarian cancer are reviewed.

Monoclonal antibodies in gastrointestinal cancers

INTRODUCTION

Among gastrointestinal cancers, colorectal and gastric neoplasms are the most frequent. The development of new targeted drugs improved the efficacy of systemic therapy in advanced stages of those malignancies.

AREAS COVERED

This review highlights the main biological processes implicated in gastrointestinal cancer development and progression, such as angiogenesis and epidermal growth factor receptor (EGFR) signaling pathway. On these bases, anti-EGFR and anti-vascular endothelial growth factor (VEGF) monoclonal antibodies in colorectal and gastric cancer are discussed. Data about further monoclonal antibodies in development are also reported.

EXPERT OPINION

The use of monoclonal antibodies in colorectal and gastric cancers showed the best outcomes when combined with chemotherapy, even though single agent anti-EGFR antibodies seem active in particular setting of metastatic colorectal cancer (CRC) patients. It is not well defined whether the addition of anti-VEGF and anti-EGFR to chemotherapy could improve outcome in those patients susceptible to CRC-related metastases resection. Little and conflicting data are available about the role of these drugs in adjuvant setting. Tests are available to select patients with higher probability to get benefit from these treatments. Further biomarkers need to be evaluated to improve this selection and achieve "tailorization" of systemic therapy.

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.

A phase 1b study of humanized KS-interleukin-2 (huKS-IL2) immunocytokine with cyclophosphamide in patients with EpCAM-positive advanced solid tumors

Background

Humanized KS-interleukin-2 (huKS-IL2), an immunocytokine with specificity for epithelial cell adhesion molecule (EpCAM), has demonstrated favorable tolerability and immunologic activity as a single agent.

Methods

Phase 1b study in patients with EpCAM-positive advanced solid tumors to determine the maximum tolerated dose (MTD) and safety profile of huKS-IL2 in combination with low-dose cyclophosphamide. Treatment consisted of cyclophosphamide (300 mg/m² on day 1), and escalating doses of huKS-IL2 (0.5–4.0 mg/m² IV continuous infusion over 4 hours) on days 2, 3, and 4 of each 21-day cycle. Safety, pharmacokinetic profile, immunogenicity, anti-tumor and biologic activity were evaluated.

Results

Twenty-seven patients were treated for up to 6 cycles; 26 were evaluable for response. The MTD of huKS-IL2 in combination with 300 mg/m² cyclophosphamide was 3.0 mg/m². At higher doses, myelosuppression was dose-limiting. Transient lymphopenia was the most common grade 3/4 adverse event (AE). Other significant AEs included hypotension, hypophosphatemia, and increase in serum creatinine. All patients recovered from these AEs. The huKS-IL2 exposure was dose-dependent, but not dose-proportional, accumulation was negligible, and elimination half-life and systemic clearance were independent of dose and time. Most patients had a transient immune response to huKS-IL2. Immunologic activity was observed at all doses. Ten patients (38%) had stable disease as best response, lasting for ≥ 4 cycles in 3 patients.

Conclusion

The combination of huKS-IL2 with low-dose cyclophosphamide was well tolerated. Although no objective responses were observed, the combination showed evidence of immunologic activity and 3 patients showed stable disease for ≥ 4 cycles.

Trial registration

http://NCT00132522

Generation and characterization of rendomab-B1, a monoclonal antibody displaying potent and specific antagonism of the human endothelin B receptor

Endothelin B receptor (ETBR) is a G protein-coupled receptor able to bind equally to the three identified human endothelin peptides. It is expressed primarily on vascular endothelial cells and involved in various physiological processes including vascular tone homeostasis, enteric nervous system development, melanogenesis and angiogenesis. Furthermore, overactivation or overexpression of ETBR have been associated with the development of various diseases such as cardiovascular disorders and cancers. Therefore, ETBR appears to be relevant target for the therapy or diagnosis of highly prevalent human diseases. In this study, we report the in vitro characterization of rendomab-B1, a monoclonal antibody (mAb) obtained by genetic immunization, which selectively recognizes the native form of human ETBR (hETBR). Rendomab-B1 is the first-reported mAb that behaves as a potent antagonist of hETBR. It recognizes an original extracellular conformational epitope on the receptor, distinct from the endothelin-1 (ET-1) binding site. Rendomab-B1 not only blocks ET-1-induced calcium signaling pathway and triggers rapid receptor internalization on recombinant hETBR-expressing cells, but also exerts pharmacological activities on human vascular endothelial cells, reducing both cell viability and ET-1-induced hETBR synthesis. In addition, binding experiments using rendomab-B1 on different melanoma cell lines reveal the structural and functional heterogeneity of hETBR expressed at the surface of these cancer cells, strongly suggesting the existence of tumor-specific receptors. Collectively, our results underscore the value of rendomab-B1 for research, therapeutic and diagnostic applications dealing with hETBR.

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.

CD133 induces tumour-initiating properties in HEK293 cells

The pentaspan protein CD133 (Prominin-1) is part of the signature of tumour-initiating cells for various cancer entities. The aim of the present study was to investigate the impact of ectopic CD133 expression on tumourigenic properties of otherwise CD133-negative, non-tumourigenic cells in vitro and in vivo. CD133 was stably transfected into human embryonic kidney 293 (HEK293) which was then sorted for the expression of CD133. The effects of CD133 on cell proliferation were assessed upon standard cell counting of sorted cells at various time points. Severe combined immunodeficient (SCID) mice (n = 30) were injected with HEK293 CD133(high) and CD133(low) transfectants (5 × 10(3), 1 × 10(5), or 5 × 10(6) cells per injection). The expression of CD133, Ki67, CD44s, CD44v6, and EpCAM was analysed upon immunohistochemical staining of cryosections with specific antibodies. In vitro, ectopic expression of CD133 did influence neither cell proliferation nor cell cycle distribution of otherwise CD133-negative HEK293 cells. However, CD133(high) cells generated tumours in vivo in SCID mice with at least 1,000-fold increased frequency compared to CD133(low) cells. Tumour load was also significantly increased in CD133(high) cells as compared to those tumours formed by high numbers of CD133(low) cells. Immunohistochemistry stainings disclosed no changes in Ki67, CD44s, CD44v6, or EpCAM once tumours were formed by either cell type. CD133 induces tumour-initiating properties in HEK293 cells in vivo and is potentially involved in the regulation of tumourigenicity. Future research will aim at the elucidation of molecular mechanisms of CD133-induced tumourigenicity.

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.

Demasking of epithelial cell adhesion molecule (EpCAM) on circulating epithelial tumor cells by Tween®20 treatment in breast cancer patients

The epithelial cell adhesion molecule (EpCAM) embedded in the plasma membrane of circulating epithelial tumor cells (CETC) is used for detection and enrichment of circulating tumor cells in peripheral blood and as a target for anti-epithelial antibodies elicited during immune response in anti-tumor immunization. Although an efficient immune response against EpCAM can be generated, the clinical application of such approaches has not been successful so far and the detection of circulating epithelial cells is highly variable. One reason for these discrepancies may be that not all circulating tumor cells are equally accessible for the specific antibody. A possible reason might be masking of EpCAM by glycoproteins or membrane lipoproteins preventing antibody binding.

We have tested the application of detergents as demasking agents known to be successful in demasking red blood cell epitopes and determined how and in which way they affect integral membrane proteins and membrane lipids.

The results showed that the polysorbate Tween

The data presented in this study suggest that EpCAM is present on part of circulating tumor cells in a masked form and that it is possible to demask EpCAM on CETC of breast cancer patients using Tween