New-Concept Chemotherapy by Nanoparticles of Biodegradable Polymers: Where Are We Now?

TLDR

Liposomes have evolved from first‑generation vesicles to long‑circulating, PEG‑coated “stealth” formulations that reduce phagocytic uptake and enable targeted delivery. The review examines stealth liposome technology, summarizing pre‑clinical and clinical data on key formulations and emerging trends. Stealth liposomes achieve prolonged circulation and reduced phagocytic uptake by incorporating PEG and surface‑modified ligands, enabling targeted delivery. This technology has produced numerous liposome formulations with high target efficiency and activity.

Abstract

Among several promising new drug-delivery systems, liposomes represent an advanced technology to deliver active molecules to the site of action, and at present several formulations are in clinical use. Research on liposome technology has progressed from conventional vesicles ("first-generation liposomes") to "second-generation liposomes", in which long-circulating liposomes are obtained by modulating the lipid composition, size, and charge of the vesicle. Liposomes with modified surfaces have also been developed using several molecules, such as glycolipids or sialic acid. A significant step in the development of long-circulating liposomes came with inclusion of the synthetic polymer poly-(ethylene glycol) (PEG) in liposome composition. The presence of PEG on the surface of the liposomal carrier has been shown to extend blood-circulation time while reducing mononuclear phagocyte system uptake (stealth liposomes). This technology has resulted in a large number of liposome formulations encapsulating active molecules, with high target efficiency and activity. Further, by synthetic modification of the terminal PEG molecule, stealth liposomes can be actively targeted with monoclonal antibodies or ligands. This review focuses on stealth technology and summarizes pre-clinical and clinical data relating to the principal liposome formulations; it also discusses emerging trends of this promising technology.