Comparative efficacies of conventional amphotericin b, liposomal amphotericin B (AmBisome), caspofungin, micafungin, and voriconazole alone and in combination against experimental murine central nervous system aspergillosis

Abstract

Central nervous system (CNS) aspergillosis is a severe disease that responds poorly to current therapies. The current studies examined the efficacies of several antifungal agents alone or in combination with a murine model of CNS aspergillosis. Immunosuppressed mice were infected intracerebrally with Aspergillus fumigatus and treated with an amphotericin B preparation, an echinocandin, or voriconazole (VCZ) given alone or in combination. Monotherapy studies showed that micafungin (MICA), caspofungin (CAS), VCZ, conventional amphotericin B (AMB), Abelcet (ABLC) (a lipid-carried AMB formulation; Enzon Pharmaceuticals, Inc.), and AmBisome (AmBi) (liposomal AMB; Gilead Sciences, Inc.) were efficacious. However, doses of AmBi above 15 mg/kg of body weight showed reduced efficacy. Neither MICA nor CAS showed dose responsiveness at the doses tested (1, 5, or 10 mg/kg). Only the 40-mg/kg dose of VCZ was effective. AmBi and ABLC showed dose responsiveness, with 10-mg/kg doses causing a significant reduction in fungal burden; they had equivalent activities at the 10-mg/kg dose. Suboptimal dosages of AmBi in combination with MICA, CAS, or VCZ were effective in prolonging survival. However, significantly enhanced activity was demonstrated only with AmBi and VCZ in combination. AmBi in combination with MICA or CAS showed a trend toward enhanced activity, but the combination was not significantly superior to monotherapy. The use of AmBi with CAS or VCZ at optimal doses did not improve efficacy. Cure was not attained with any dosage combinations. These results indicate that AmBi in combination with VCZ may be superior for treatment of CNS aspergillosis; combinations of AmBi and MICA or CAS were not antagonistic and may have a slight benefit.

FIG. 1.

Serum pharmacokinetics of VCZ in mice after one or multiple doses. Average from two mice at each time point after the last dose. AUC_0-24, area under the concentration-time curve from 0 to 24 h.

FIG. 2.

Efficacy of sole treatment with AmBi at 1, 5, or 10 mg/kg, ABLC at 1 or 10 mg/kg, MICA at 1, 5, or 10 mg/kg, CAS at 1, 5, or 10 mg/kg, VCZ at 5, 10, or 40 mg/kg, or AmB at 1 mg/kg in the prolongation of survival of mice infected intracerebrally with A. fumigatus. The same D5W and AMB data are repeated in each panel to serve as reference points for the purposes of comparison. GFJ, grapefruit juice. For all groups, n = 10.

FIG. 3.

Recovery of A. fumigatus from the organs of surviving mice (see Fig. 2 and legend) given one of the indicated monotherapies. A log₁₀ value of 5 indicates death of the animal, and a value of 0 indicates that the number of CFU present, if any, was below the detectable number of approximately 10 CFU per entire organ. For all groups, n = 10. The bar represents the median.

FIG. 4.

Efficacies of the various combination therapies and monotherapies in the prolongation of survival of mice infected intracerebrally with A. fumigatus. The D5W group is repeated in each panel to serve as reference. Abbreviations: D5W, 5% dextrose water; AMB, 1 mg/kg; GFJ, grapefruit juice; AmBi, 1 mg/kg; VCZ, 40 mg/kg; MICA, 1 mg/kg; CAS, 1 mg/kg. For all groups, n = 10.

FIG. 5.

Recovery of A. fumigatus from the organs of surviving mice given one of the indicated monotherapies or combination therapies (see Fig. 4 and legend). A log₁₀ value of 5 indicates death of the animal, and a value of 0 indicates that the number of CFU present, if any, was below the detectable number of approximately 10 CFU per entire organ. For all groups, n = 10. The bar represents the median.

FIG. 6.

Cumulative mortalities of mice infected intracerebrally with A. fumigatus and given one of the respective treatments. Treatment began 1 day postinfection (day 0). AmBi, 10, 15, 20, or 25 mg/kg; CAS (CAS or CASPO), 10 mg/kg; VCZ, 40 mg/kg. One mouse in each of the CAS 10 and AmBi (3 days)-plus-VCZ (7 days) groups died prior to the beginning of treatment; for each of these groups, n = 9. For all other groups, n = 10.