Background: The trifunctional bi-specific antibody Removab bridges and activates CD3 positive T cells to EpCAM on carcinoma cells and simultaneously binds to an accessory immune cell, thus inducing tumor cell lysis. Following intravenous application, Removab may induce cytokine-related side effects resulting in a sepsis like syndrom. It was questioned, if peripheral mononuclear blood cells (PBMN) already opsonized with Removab could retain antitumor activity and induce less cytokine release than the mere antibody.
Methods: PBMN of patients with head and neck cancer were incubated with Removab and the released cytokines were washed out. Then the Removab-opsonized PBMN were coincubated with genuine tumor cells of the same patient on a chorioallantois membrane for 24 h (T 24) and 48 h (T 48). Tumor cells coincubated with Cisplatin or solely cell culture medium served as control.
Results: Coincubation of tumor cells with opsonized PBMN resulted in a 32 % decrease of viable cells at T 24 and a 37 % decrease at T 48, whereas viable cells increased by 10 % at T 24 or 3 % at T 48 when incubated with medium alone (p < 0.05). This tumor cytotoxicity was similar to that of Cisplatin (35 % at T 24/37 % at T 48).
Conclusion: In an autologous human ex vivo tumor system, Removab-opsonized PBMN induce tumor cell lysis with significantly reduced cytokine release after i. v. application.