Tetravalent Antibody–scTRAIL Fusion Proteins with Improved Properties

We applied the immunoglobulin E (IgE) heavy-chain domain 2 (EHD2) as the covalently linked homodimerization module to generate antibody–scTRAIL fusion proteins. By fusing a humanized single-chain fragment variable (scFv) directed against EGFR to the N-terminus of the EHD2 and a single-chain derivative of TRAIL (scTRAIL) to the C-terminus of the EHD2, we produced a dimeric, tetravalent fusion protein. The fusion protein retained its binding activity for EGFR and TRAIL receptors. In vitro, the targeted antibody–scTRAIL fusion protein exhibited an approximately 8- to 18-fold increased cytotoxic activity compared with the untargeted EHD2-scTRAIL fusion protein. This resulted in increased antitumor activity in a subcutaneous Colo205 xenograft tumor murine model. In summary, the scFv-EHD2-scTRAIL fusion protein combines target cell selectivity with an increased TRAIL activity leading to improved antitumor activities. Mol Cancer Ther; 13(1); 101–11. ©2013 AACR.