| Current commercial formulations of Amphotericin B (AmB) cause severe nephrotoxicity or have limited efficacy. As AmB remains a central antifungal agent for systemic fungal diseases, more effective formulations of this drug could be very beneficial. We have successfully solubilized AmB in micelles of stearic acid modified PEG-block-poly(aspartic acid) polymers (PEG-b-PHSA) and co-solubilized AmB with sterols in PEG-phospholipid micelles. Both polymer micelles have lipid-like cores, ideal for the solubilization of AmB and were able to solubilize AmB in a deaggregated state, which is believed to be non-toxic for mammalian cell membranes. In vitro results indicated good stability in serum mimicking conditions for AmB-incorporated PEG- b-PHSA micelles. AmB-incorporated PEG-b-PHSA micelles were also tested in rats to determine pharmacokinetic profile and nephrotoxic effects of this formulation. PEG-b-PHSA micelles did not show marked differences in pharmacokinetics, relative to a commercial AmB formulation, yet nephrotoxicity was significantly reduced. The reduced kidney toxicity may be related to the deaggregation state of AmB in PEG- b-PHSA micelles. AmB incorporated PEG-phospholipid micelles co-loaded with core-stabilizing ergosterol, cholesterol, or 7-dehydrocholesterol or no sterol, showed marked differences in aggregation state of AmB. The thermodynamically preferential interaction of AmB with ergosterol and 7-dehydrocholesterol resulted in aggregate formation in the micelle core, while AmB was predominantly deaggregated when co-solubilized with cholesterol or by itself in PEG-phospholipid micelles. Hemolysis studies indicated a greater hemolytic activity of AmB, when co-solubilized with either ergosterol or 7-dehydrocholesterol, relative to cholesterol. The cholesterol co-loaded PEG-phospholipid micelles were markedly less hemolytic than sterol-free AmB-incorporated PEG-phospholipid micelles, even though AmB was deaggregated in the absence of sterols. This indicates that both the stabilizing effects of cholesterol on the PEG-phospholipid micelle core, as well as deaggregation of AmB may be instrumental in reducing toxicity of AmB. In conclusion, the ability of polymeric micelles to act as kinetically stable carrier system for deaggregated AmB is unique and attractive for the treatment of systemic fungal diseases. |
