iRGD is a cyclic peptide that binds to integrins that are expressed on tumor endothelial cells. Upon binding, a protease cleavage event is activated. When this happens, the peptide is then able to bind neuropilin-1, activating an endocytotic/exocytotic transport pathway. As a result, it is able to hone in on tumor cells and make them permeable to transport of many types of cancer therapies.
This makes traditional cancer therapies better and less toxic. One study showed that doxorubicin, liposomal doxorubicin, Herceptin trastuzumab or Abraxane nab-paclitaxel had greater drug accumulation in the tumor by up to 40-fold than mice injected with one of the drugs alone. They equaled greater reductions in tumor growth. In all, the drug-peptide combination was as effective as threefold higher doses of drug alone.