Multifunctional αvβ6 Integrin-Specific Peptide–Pt(IV) Conjugates for Cancer Cell Targeting

Increasing the specificity of cancer therapy, and thereby decreasing damage to normal cells, requires targeting to cancer-cell specific features. The αvβ6 integrin is a receptor involved in cell adhesion and is frequently up-regulated in cancer cells compared to normal cells. We have selected a peptide ligand reported to bind specifically to the β6 integrin and have synthesized a suite of multispecific molecules to explore the potential for targeting of cancer cells. A combination of solid-phase peptide synthesis and chemoselective ligations was used to synthesize multifunctional molecules composed of integrin-targeting peptides, cytotoxic platinum(IV) prodrugs, and fluorescent or affinity probes joined with flexible linkers. The modular synthesis approach facilitates the construction of peptide–drug conjugates with various valencies and properties in a convergent manner. The binding and specificity of the multifunctional peptide conjugates were investigated using a cell line transfected with the β6 integrin and fluorescence microscopy. This versatile and highly controlled approach to synthesizing labeled peptide–drug conjugates has the potential to target potent cytotoxic drugs specifically to cancer cells, reducing the doses required for effective treatment.