Chapter 2 - EPR effect and its implications in passive targeting of nanocarriers to tumors

Abstract

Among the various reasons for mortality worldwide, cancer is one of the most common. Therefore development of effective cancer treatment methods is urgently needed. The world is looking to researchers to develop a “magic bullet” that selectively targets only cancerous tissues and thus leads to a decreased cancer mortality rate. The enhanced permeability and retention (EPR) effect plays a vital role in the accumulation of drugs or nanoparticulate systems at tumor sites. Over the last 10 years scientists have observed that there is increasing difference in inter- and intrapatient reactivity to EPR-based targeting. This knowledge has helped in the development of various nanoformulations currently undergoing clinical trials. The only way to avoid this heterogeneity between patients is to develop individualized nanomedicine rather than a one-size-fits-all targeting approach. This requires better understanding of the characteristic properties of tumor sites, receptors involved, and EPR effect. This chapter provides detailed information about the EPR effect, its principles, and factors affecting it. It also examines therapies for enhancing EPR-mediated tumor targeting and bypassing it.