gms | German Medical Science

125. Kongress der Deutschen Gesellschaft für Chirurgie

Deutsche Gesellschaft für Chirurgie

22. - 25.04.2008, Berlin

Ex vivo treatment of malignant pleural effusions with the bispecific antibody MT110 targeting EpCAM and CD3

Meeting Abstract

  • corresponding author J. Witthauer - University of Munich, Department of Surgery, Großhadern, Munich, Germany
  • B. Schlereth - Micromet AG, Munich, Germany
  • K. Brischwein - Micromet AG, Munich, Germany
  • K.-W. Jauch - University of Munich, Department of Surgery, Großhadern, Munich, Germany
  • P. Baeuerle - Micromet AG, Munich, Germany
  • B. Mayer - University of Munich, Department of Surgery, Großhadern, Munich, Germany

Deutsche Gesellschaft für Chirurgie. 125. Kongress der Deutschen Gesellschaft für Chirurgie. Berlin, 22.-25.04.2008. Düsseldorf: German Medical Science GMS Publishing House; 2008. Doc08dgch8819

Die elektronische Version dieses Artikels ist vollständig und ist verfügbar unter:

Veröffentlicht: 16. April 2008

© 2008 Witthauer et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen ( Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.



Introduction: Approximately half of patients with metastatic breast cancer develop a malignant pleural effusion that often becomes persistent and progressive despite therapeutic interventions. Mean survival of these patients is only a few months. Hence, current treatment options for breast cancer patients with malignant pleural effusion are insufficient. Successful anti-cancer strategies using, e.g., monoclonal antibodies and small molecule kinase inhibitors, underline the potential of targeted therapies in metastatic breast cancer. Another class of promising drug candidates are bispecific single chain antibodies that simultaneously target the epithelial antigen EpCAM (CD326) and the T cell antigen CD3. In the present study, the ex vivo efficacy in tumor cell lysis of one representative, MT110, was tested using pleural effusion samples from breast cancer patients.

Materials and methods: Malignant pleural effusions were collected by chest drainage and cells isolated by fractionated centrifugation. Target antigens were detected using the ABC staining procedure on cytospins and FACS. Ex vivo treatment of effusion samples containing EpCAM+ cells was performed with MT110 at concentrations of 0.1, 1, 10 and 1000 ng/ml for 48 h and 72 h. Redirected target cell lysis was determined by FACS analysis using double fluorescence labelling with the nucleic acid dye 7-AAD and EpCAM-APC. Stimulation of endogenous T cells by MT110 was determined by the expression of CD25 and granzyme B on CD4+ and CD8+ cells.

Results: The volume of pleural effusions (n=18) ranged from 40 ml to 800 ml (median 350 ml). The number of isolated effusion cells varied from 3 x 104/ml to 1.5 x 106/ml (median 4 x 105 cell/ml). Immunohistochemical analysis revealed EpCAM+ cells in 78% (14 out of 18) of effusion samples. Ex vivo treatment with MT110 was performed with seven out of 14 pleural exudates. The fraction of EpCAM+ pleural carcinoma cells varied between 30% and 100% (median 78%), and that of CD3+ leukocytes between 60% and 93% (median 80%). Subpopulation analysis showed a median fraction of 71% CD4+ and 27% CD8+ T cells (median ratio of CD4:CD8 = 2.6:1). The ratio between endogenous CD3+ effector and EpCAM+ target cells (E:T) varied between 1:4 and 620:1. Ex vivo treatment of malignant pleural effusion samples with MT110 revealed a significant dose-dependent and specific redirected lysis of EpCAM-expressing target cells. After 72 h, 37% ± 27% (median ± SD) of EpCAM+ cells were killed using 10 ng/ml MT110 (p=0.03), and 57% ± 29.5% with 1000 ng/ml MT110 (p= 0.016). A high degree of lysis (≥50% dead cells) often correlated with a favourable E:T ratio ≥1. MT110 induced a significant increase of CD25 expression on CD4+ and CD8+ cells at 1000 ng/ml MT110 after 48 h (p= 0.03), and after 72 h (p=0.016). Granzyme B-expression was significantly higher in CD8+ than in CD4+ cells (p=0.02). Furthermore, a high granzyme B-expression (≥50%) in CD8+ cells correlated with a higher degree of specific lysis (≥50%) of EpCAM+ cells.

Conclusion: Single-agent treatment with MT110 is capable of activating unstimulated T cells - as detected in pleural exudates - for efficient and specific redirected lysis of EpCAM+ tumor cells. The present ex vivo analysis supports the treatment of metastatic breast cancer patients presenting EpCAM+ pleural carcinoma cells. Future studies need to investigate whether the number and phenotype of pleural T cells serves as a prognostic marker for efficacy of MT110.