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Cioffi M.,Stem Cells and Cancer Group | Dorado J.,Stem Cells and Cancer Group | Baeuerle P.A.,Micromet Inc | Heeschen C.,Stem Cells and Cancer Group
Clinical Cancer Research | Year: 2012

Purpose: Tumor-initiating cells with stem-like properties, also termed cancer stem cells (CSC), have been shown to sustain tumor growth as well as metastasis and are highly resistant to chemotherapy. Because pancreatic CSCs have been isolated on the basis of EpCAM expression, we investigated whether a targeted immunotherapy to EpCAM using the bispecific T-cell-engaging antibody MT110 is capable of eradicating CSCs. Experimental Design: Westudied in vitro and in vivo the effects of MT110 on CSCs using both established cell lines as well as primary cells of human pancreatic cancer. Results: Although established cell lines were more responsive to MT110-engaged T cells, also primary cells showed a time- and dose-dependent response to treatment with the bispecific antibody. In addition, the population of highly tumorigenic CSCs was efficiently targeted by the EpCAM/CD3-bispecific antibody MT110 in vitro and in vivo using a mouse model of established primary pancreatic cancer. Pancreatic cancer cells derived from metastases were slightly more resistant to MT110 treatment on the basis of in vivo tumorigenicity studies. This appeared to be related to a higher frequency of an EpCAM-negative subpopulation of CSCs. Conclusions: Cytotoxic T cells can be effectively redirected against primary human pancreatic cancer cells by T-cell-engaging BiTE antibody MT110 including a subpopulation of highly tumorigenic CSCs. ©2011 AACR. Source

Herrmann I.,Micromet AG | Baeuerle P.A.,Micromet AG | Baeuerle P.A.,Micromet Inc | Friedrich M.,Micromet AG | And 9 more authors.
PLoS ONE | Year: 2010

With their resistance to genotoxic and anti-proliferative drugs and potential to grow tumors and metastases from very few cells, cancer stem or tumor-initiating cells (TICs) are a severe limitation for the treatment of cancer by conventional therapies. Here, we explored whether human T cells that are redirected via an EpCAM/CD3-bispecific antibody called MT110 can lyse colorectal TICs and prevent tumor growth from TICs. MT110 recognizes EpCAM, a cell adhesion molecule expressed on TICs from diverse human carcinoma, which was recently shown to promote tumor growth through engagement of elements of the wnt pathway. MT110 was highly potent in mediating complete redirected lysis of KRAS-, PI3 kinase- and BRAF-mutated colorectal TICs, as demonstrated in a soft agar assay. In immunodeficient mice, MT110 prevented growth of tumors from a 5,000-fold excess of a minimally tumorigenic TIC dose. T cells engaged by MT110 may provide a potent therapeutic means to eradicate TICs and bulk tumor cells derived thereof. © 2010 Herrmann et al. Source

Bluemel C.,Micromet AG | Hausmann S.,Micromet AG | Fluhr P.,Micromet AG | Sriskandarajah M.,Micromet AG | And 4 more authors.
Cancer Immunology, Immunotherapy | Year: 2010

Melanoma chondroitin sulfate proteoglycan (MCSP; also called CSPG4, NG2, HMW-MAA, MSK16, MCSPG, MEL-CSPG, or gp240) is a surface antigen frequently expressed on human melanoma cells, which is involved in cell adhesion, invasion and spreading, angiogenesis, complement inhibition, and signaling. MCSP has therefore been frequently selected as target antigen for development of antibody- and vaccine-based therapeutic approaches. We have here used a large panel of monoclonal antibodies against human MCSP for generation of single-chain MCSP/CD3-bispecific antibodies of the BiTE (for bispecific T cell engager) class. Despite similar binding affinity to MCSP, respective BiTE antibodies greatly differed in their potency of redirected lysis of CHO cells stably transfected with full-length human MCSP, or with various MCSP deletion mutants and fusion proteins. BiTE antibodies binding to the membrane proximal domain D3 of MCSP were more potent than those binding to more distal domains. This epitope distance effect was corroborated with EpCAM/CD3-bispecific BiTE antibody MT110 by testing various fusion proteins between MCSP and EpCAM as surface antigens. CHO cells expressing small surface target antigens were generally better lysed than those expressing larger target antigens, indicating that antigen size was also an important determinant for the potency of BiTE antibody. The present study for the first time relates the positioning of binding domains and size of surface antigens to the potency of target cell lysis by BiTE-redirected cytotoxic T cells. In case of the MCSP antigen, this provides the basis for selection of a maximally potent BiTE antibody candidate for development of a novel melanoma therapy. © 2010 Springer-Verlag. Source

Munz M.,Micromet AG | Munz M.,Micromet Inc | Murr A.,Micromet AG | Murr A.,Micromet Inc | And 23 more authors.
Cancer Cell International | Year: 2010

Background: Epithelial cell adhesion molecule (EpCAM) is frequently and highly expressed on human carcinomas. The emerging role of EpCAM as a signalling receptor and activator of the wnt pathway, and its expression on tumor-initiating cells, further add to its attractiveness as target for immunotherapy of cancer. Thus far, five conventional monoclonal IgG antibodies have been tested in cancer patients. These are murine IgG2a edrecolomab and its murine/human chimeric IgG1 antibody version, and humanized, human-engineered and fully human IgG1 antibodies 3622W94, ING-1, and adecatumumab (MT201), respectively. Here we compared all anti-EpCAM antibodies in an attempt to explain differences in clinical activity and safety.Methods: We recombinantly produced all antibodies but murine edrecolomab and investigated them for binding affinity, EpCAM epitope recognition, ADCC and CDC, and inhibition of breast cancer cell proliferation.Results: ING-1 and 3622W94 bound to EpCAM with much higher affinity than adecatumumab and edrecolomab. Edrecolomab, ING-1, and 3622W94 all recognized epitopes in the exon 2-encoded N-terminal domain of EpCAM, while adecatumumab recognized a more membrane proximal epitope encoded by exon 5. All antibodies induced lysis of EpCAM-expressing cancer cell lines by both ADCC and CDC with potencies that correlated with their binding affinities. The chimeric version of edrecolomab with a human Fcγ1 domain was much more potent in ADCC than the murine IgG2a version. Only adecatumumab showed a significant inhibition of MCF-7 breast cancer cell proliferation in the absence of complement and immune cells.Conclusion: A moderate binding affinity and recognition of a distinct domain of EpCAM may best explain why adecatumumab showed a larger therapeutic window in cancer patients than the two high-affinity IgG1 antibodies ING-1 and 3622W94, both of which caused acute pancreatitis. © 2010 Münz et al; licensee BioMed Central Ltd. Source

Schmidt M.,Johannes Gutenberg University Mainz | Ruttinger D.,Micromet Inc | Ruttinger D.,Micromet AG | Sebastian M.,Johannes Gutenberg University Mainz | And 15 more authors.
Annals of Oncology | Year: 2012

Background: Targeted therapy options in HER2-negative breast cancer are limited. This open-label, multicenter phase IB dose-escalation trial was conducted to determine safety, tolerability, and antitumor activity of a combination of docetaxel (Taxotere) and increasing doses of adecatumumab, a human IgG1 antibody targeting epithelial cell adhesion molecule (EpCAM), in EpCAM-positive relapsed or primary refractory advanced-stage breast cancer. Patients and methods: Patients pretreated with up to four prior chemotherapy regimens received increasing adecatumumab doses either every 3 weeks (q3w) or weekly (qw) combined with docetaxel (100 mg/m2 q3w). Primary end points were safety and tolerability. Antitumor activity was evaluated according to RECIST. Clinical benefit was defined as complete or partial response or stable disease for ≥24 weeks. Results: Thirty-one evaluable patients were treated. Most adverse events were mild to moderate in severity. Neutropenia, leukocytopenia, lymphopenia, and diarrhea (dose-limiting) were the most frequent toxic effects. Maximum tolerated doses of adecatumumab given in combination with docetaxel were 550 mg/m2 q3w and 360 mg/m2 qw. Clinical benefit was observed in 44% of patients treated with q3w adecatumumab and docetaxel, increasing to 63% in patients with high EpCAM-expressing tumors. Conclusion: Combination therapy of adecatumumab and docetaxel is safe, feasible, and potentially active in heavily pretreated advanced-stage breast cancer. © The Author 2012. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. Source

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