Development of next-generation macromolecular drugs based on the EPR effect: challenges and pitfalls

Abstract

Introduction: A major problem with conventional antitumor therapeutics is nonselective delivery of cytotoxic drugs to normal vital organs and tissues but little delivery to tumor tissues.

Areas covered: Here, the authors describe the tumor selective delivery of antitumor drugs by taking advantage of nano-sized drugs and the means to augment it further. Based on the enhanced permeability and retention (EPR) effect, the mechanism for more efficient universal tumor delivery using macromolecular drugs to cover wider tumor types than single molecular target is discussed. Unique properties of solid tumor vasculature in the tumor tissue are discussed, especially leakiness of the blood vessels and factors involved and impaired clearance of macromolecular drugs from the tumor interstitium via the lymphatic system. The criteria for such macromolecular drugs or nanomedicines for effective accumulation at tumor sites is commented on as well as the importance of long plasma retention time of such drugs and a need to release active principles from nanoparticles at target sites. Methods to augment the EPR effect and tumor delivery (2 – 3 times) and its application to photodynamic therapy are also discussed.

Expert opinion: Tumor selective delivery of antitumor drugs based on the EPR effect can be accomplished and augmented by modulating the tumor environment. This methodology is favorable not only for tumor therapy but also for tumor imaging.

Keywords:

• application of EPR effect to PDT
• augmentation of EPR effect
• barriers to tumor delivery
• enhanced permeability and retention effect of solid tumor
• macromolecular drug
• nanomedicine
• tumor selective drug delivery

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Erratum

Acknowledgements

The authors would like to thank Ms. Judy Gandy for her excellent/invaluable assistance in English editing.

Declaration of interest

The authors have received research grants from the Government of Japan: Grant-in-Aids from MEXT, No.08011717 for H Maeda, No.26860031 for H Nakamura, No.25430162 for J Fang, and Cancer Specialty Grant from MHWL, H23-3rd Cancer Project-General-001 for H Maeda.

Notes

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