Liposomes in the treatment of infectious diseases

Phospholipids and other polar lipids can form liposomes and similar colloid al particles that can be used as drug carrier systems. The potential of lip osomal delivery systems to increase the therapeutic index (efficacy to safe ty ratio) of clinically important drugs has been realised with the recent a pproval of liposomal oncologic and antifungal drugs. The application of lip osomes to the treatment of infectious diseases initially focused on intrace llular pathogens, based on the natural targeting of liposomes to phagocytic cells and on the antifungal drug amphotericin B, based on its unique affin ity for lipids. Recent studies with small, low-clearance liposomes have sho wn that more specialised formulations may provide benefits over simpler 'fi rst generation' liposomes for the treatment of infectious diseases, includi ng prolonged residence in plasma, increased tissue exposure and targeting t o sites of infection. These improved biopharmaceutical properties have been associated with both curative and prophylactic activity against a range of non-intracellular pathogens, including Staphylococcus and Klebsiella. Thes e and other highly engineered liposome formulations may provide effective d elivery systems for specific antibacterial, antifungal and antiviral indica tions in the future. Adequate patent protection will be crucial in fully ex ploiting these advanced liposome technologies and in maintaining market sha re for liposomal products. This review discusses some of the patent issues related to liposomes and their use in the treatment of infectious diseases.