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Cancer Lett. 2011 Apr 28;303(2):128-39. doi: 10.1016/j.canlet.2011.01.020. Epub 2011 Feb 19.

Heterodimeric bispecific antibody-derivatives against CD19 and CD16 induce effective antibody-dependent cellular cytotoxicity against B-lymphoid tumor cells.

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Chair of Genetics, University of Erlangen-Nuremberg, Erwin-Rommel-Straße 3, 91058 Erlangen, Germany.


Bispecific scFv antibody-derivatives (bsscFvs) recruiting natural killer (NK) cells for the lysis of malignant cells have therapeutic potential. However, a bsscFv specific for the B-lymphoid tumor antigen CD19 and the trigger molecule CD16 on NK cells had similar affinities for both antigens (42 and 58nM, respectively) and was not optimal for cytotoxicity. Therefore, a bispecific tribody (bsTb) was constructed with two binding sites for CD19 and one for CD16. This bsTb contained a CD19-specific Fab fragment carrying a CD16-specific scFv fused to its light chain and a CD19-specific scFv fused to its heavy chain. The bsTb was compared with a bispecific bibody (bsBb) lacking the CD19-specific scFv. The bsTb had 3-fold greater avidity for CD19 than the bsBb (8 and 24nM, respectively), while both had equal affinity for CD16 (56nM). Both molecules mediated antibody-dependent cellular cytotoxicity (ADCC) of leukemia-derived SEM cells and primary cells from leukemia patients. The bsTb showed half-maximum effective concentrations (EC(50)) of 55pM and promoted equal lysis as the bsBb and the bsscFv at 6- and 12-fold lower concentrations, respectively. Among these three molecules the bsTb showed the most promising in vitro properties which are anticipated to be displayed also in vivo.

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