Innovative liposomal amphotericin B formulation for oral treatment of visceral leishmaniasis

Current formulations of liposomal amphotericin B (AmB), such as AmBisome, have limited use against leishmaniasis due to high cost, thermal instability, the need for parenteral administration and reduced efficacy in disseminated infections. The present study aimed to optimize PEGylated liposomal AmB formulation in terms of stability and efficacy via the oral route, as well as to simplify the preparation process, comparing the anionic lipids distearoylphosphatidylglycerol (DSPG) and dicetylphosphate (DCP), employing low-cost lipids, and investigating the easily scalable ethanol injection method. Importantly, this work evaluated for the first time the therapeutic potential of the PEGylated liposomal AmB formulation for visceral leishmaniasis (VL). Two different PEGylated liposomal AmB formulations, LAmB-DSPG and LAmB-DCP, essentially unilamellar and monodisperse, with mean diameter below 150 nm and AmB encapsulation efficiency exceeding 95%, were obtained. LAmB-DSPG and LAmB-DCP demonstrated higher stability in simulated gastric fluid, less aggregated AmB and faster drug release, compared to AmBisome. LAmB-DCP exhibited high stability after storage in aqueous suspension for at least 4 months at 4 and 25 °C. When evaluated for oral therapeutic efficacy in hamsters infected with Leishmania (Leishmania) infantum, LAmB-DCP, at a dose of 5 mg/kg/day for 10 days, resulted in significant parasite suppression of 88.4% in the liver and 80% in the spleen. No significant parasite suppression was observed with LAmB-DSPG. Oral treatment with LAmB-DCP also reduced parasite load at least as effectively as parenteral treatment with AmBisome at the same dose. Unlike parenteral treatments, oral treatments showed no signs of hepatic or renal toxicity.