scFv-Based "Grababody" as a General Strategy to Improve Recruitment of Immune Effector Cells to Antibody-Targeted Tumors.

Recruitment of immune cells to tumor cells targeted by a therapeutic antibody can heighten the antitumor efficacy of the antibody. For example, p185her2/neu-targeting antibodies not only downregulate the p185her2/neu kinase (ERBB2) but also trigger complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) through the antibody Fc region. Here, we describe a generalized strategy to improve immune cell recruitment to targeted cancer cells, using a modified scFv antibody we call a "Grababody" that binds the target protein and endogenous immunoglobulins. The model system we used to illustrate the use of this platform recognizes p185her2/neu and includes an IgG binding domain. The recombinant scFv Grababody that was created recruited circulating human IgGs and attracted immune cells carrying Fc receptors to tumor cells that expressed p185her2/neu. The presence of the IgG binding domain significantly enhanced CDC and ADCC activity and improved antitumor activity in vivo. Our results illustrate a novel general approach to improve antibody-like proteins for therapeutic applications. [ABSTRACT FROM AUTHOR]