Abstract
Cyclic peptides have chemical and biological stabilities and potent binding affinity for their target molecules due to their conformational restriction. Therefore, these are major molecules in mid-size drugs researche. To date, we have developed a cyclic peptide-based chemokine receptor CXCR4 antagonist, which has high anti-HIV activity and is now in Phase III clinical trial as a drug candidate for cancer and leukemia. In addition, we have developed binding ligands for epidermal growth factor receptor(EGFR), which is a receptor overexpressing on the surface of several cancer cells. Bivalent ligands, which contain two CXCR4 ligands or two EGFR ligands, have also been synthesized to have selective recognition for dimeric CXCR4 or EGFR, respectively. These cyclic peptides might be useful as drug delivery molecules targeting cancer cells, thus conjugate molecules, containing these cyclic peptides and therapeutic agents, were synthesized. As a result, targeted delivery of the agents were successful due to specific affinity of these cyclic peptides.
