Relation between Skin Pharmacokinetics and Efficacy in AmBisome Treatment of Murine Cutaneous Leishmaniasis

AmBisome (LAmB), a liposomal formulation of amphotericin B (AmB), is a second-line treatment for the parasitic skin disease cutaneous leishmaniasis (CL). Little is known about its tissue distribution and pharmacodynamics to inform clinical use in CL. Here, we compared the skin pharmacokinetics of LAmB with those of the deoxycholate form of AmB (DAmB; trade name Fungizone) in murine models of Leishmania major CL. Drug levels at the target site (the localized lesion) 48 h after single intravenous (i.v.) dosing of the individual AmB formulations (1 mg/kg of body weight) were similar but were 3-fold higher for LAmB than for DAmB on day 10 after multiple administrations (1 mg/kg on days 0, 2, 4, 6, and 8). After single and multiple dosing, intralesional concentrations were 5- and 20-fold, respectively, higher than those in the healthy control skin of the same infected mice. We then evaluated how drug levels in the lesion after LAmB treatment relate to therapeutic outcomes. After five administrations of the drug at 0, 6.25, or 12.5 mg/kg (i.v.), there was a clear correlation between dose level, intralesional AmB concentration, and relative reduction in parasite load and lesion size (R(2) values of >0.9). This study confirms the improved efficacy of the liposomal over the deoxycholate AmB formulation in experimental CL, which is related to higher intralesional drug accumulation.