Figure 4.

Schematic depiction of possibilities of avidity increase of heterodimeric peptides depending on receptor densities on the target cell. (A) Both target receptors are highly overexpressed, resulting in a high density of both receptor types and low distances between the different receptor types. (B) and (C) Only one of two receptors is strongly expressed, resulting in a high density of only one receptor type while the other is expressed in relatively lower density. In this case, the affinity of that part of the heterodimer is increased, which binds to the receptor expressed in lower density (C) while the affinity for the peptide binding to the strongly expressed receptor remains unaltered (B).