A new approach towards developing a smart and multifunctional peptide-based drug delivery system for selective targeting and treatment of invasive/metastatic breast cancer.

Cancer remains one of the leading causes of morbidity and mortality worldwide. Breast cancer is the most frequently diagnosed cancer and causes cancerrelated deaths in women. In cancer, targeted drugs are often divided into two strategies: “passive targeting” and “active targeting”. Passive targeting suffers from low selectivity and poor retention in tumors. Such limitations lead to the development of an active targeting strategy. Active targeting describes the specific interaction between drugs or drug carriers and target cells, which usually occurs through receptor-ligand interactions. Here, we propose to develop a peptide-based drug conjugate as a novel targeted drug delivery system that enhances selectivity, localization, and activity of antitumor therapeutics on metastatic and invasive breast cancer cells by using endoxefin (END) as a targeting ligand for estrogen receptor, Metalloproteinase peptide-substrate (MMP2) for trigger release of drug, and doxorubicin (DOX) as an antitumor therapeutic.