Preparation and properties of FabIgG, a chimeric univalent antibody designed to attack tumour cells.

In order to promote the killing of tumour cells by antibody a derivative has been synthesized in which Fab'gamma from xenogeneic antibody is thioether-bonded to half-cystine on normal IgG of the species to be treated. The resulting entity, FabIgG, is obtained with about a 40% yield of the starting Fab'gamma. Being univalent it evades antigenic modulation. It activates complement efficiently, is minimally immunogenic, and appears to be catabolized at the slow rate characteristic of autologous IgG.