Preparation of a bispecific F(ab')2 targeted to the human IL-2 receptor

The heterodimer-forming leucine zippers Fos and Jun can efficiently mediate the formation of bispecific F(ab')2 when they are fused separately to two different Fab' fragments. This recombinant method can be used in conjunction with the humanization process to yield humanized bispecific F(ab')2. The potential immunogenicity of the leucine zippers can be eliminated by their removal using pepsin digestion. This method has been scaled up to produce hundreds of milligrams of a bispecific F(ab')2 that targets two subunits of the human IL-2 receptor.