Ex vivo Therapie maligner Pleuraergüsse beim metastasierten Mammakarzinom mit dem bispezifischen anti EpCAM/CD3 Antikörper MT110

Abstract

Aim: Despite therapy, approximately half of patients with metastatic breast cancer develop a malignant pleural effusion (MPE) associated with short survival. Hence, new treatment strategies are urgently needed. In the present study, the efficacy of the bispecific single-chain antibody MT110 targeting both the epithelial antigen EpCAM (CD326) and the T cell antigen CD3 was investigated ex vivo with MPE samples of breast cancer patients. Methods: Target antigen expression of MPE cells was analyzed by immunohistochemistry (ABC-method on cytospins, FACS). Percentage of redirected target cell lysis by MT110 was determined by double staining of cells with 7-amino actinomycin (7-AAD) and an anti-EpCAM antibody using FACS analysis. Activation of autologous CD4+ and CD8+ cells in response to MT110 was studied by the expression of CD25, granzyme B and different cytokines i. e. IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ (FACS). Results: EpCAM+ cells were found in 14 out of 18 (78 %) MPE samples from metastatic breast cancer patients. The fraction of EpCAM+ pleural carcinoma cells varied between 30 % and 100 % (mean 78 %). CD3-positive cells were detected in all MPE samples ranging from 60 % to 93 % (mean 80 %). Seven effusion samples were analyzed for MT110 treatment and revealed a dose-dependent and specific redirected lysis of EpCAM+ cells after 48 h and 72 h with 10 ng/ml (48 h, 72 h: p = 0.03) and 1000 ng/ml (48 h, p = 0.03; 72 h, p = 0.016). After 72 h, 57 % ± 29.5 % (mean ± SD) of EpCAM+ cells were killed using 1000 MT110. Antibody treatment (1000 ng/ml) increased the fraction of CD25/CD4 cells after 48 h (p = 0.03) and 72 h (p = 0.016). Similar, CD25 expression on CD8 cells was stimulated after 48 h (p = 0.03) and 72 h (p = 0.016) using 1000 ng/ml MT110. Cytokine analysis revealed a strong TH1 immune response detecting an increased TNF-α (p = 0.016) and INF-γ (p = 0.03) secretion. Conclusion: Single-agent treatment with MT110 is capable of activating unstimulated autologous T cells for efficient and specific redirected lysis of EpCAM+ tumor cells in MPE from breast cancer patients. Future clinical studies are warranted to investigate the efficacy of bispecific antibody MT110 in metastatic breast cancer patients.