Superior Efficacy of Liposomal Amphotericin B with Prolonged Circulation in Blood in the Treatment of Severe Candidiasis in Leukopenic Mice

In leukopenic mice with severe systemic candidiasis, single-dose treatment (5 mg of amphotericin B [AMB]/kg of body weight) with long-circulating polyethylene glycol-coated AMB liposomes (PEG-AMB-LIP) resulted in zero mortality and a significant reduction in the number of viable Candida albicans in the kidney, whereas 70% mortality was seen in mice treated with five daily doses of AmBisome (5 mg of AMB/kg · day). When the first of five daily doses of AmBisome was combined with a single low dose of Fungizone (0.1 mg of AMB/kg), the efficacy was equal to that of PEG-AMB-LIP.     

Efficacy of SCH 39304 in treatment of experimental invasive aspergillosis.

The efficacy of SCH 39304 (SCH) against Aspergillus fumigatus was assessed with an immunosuppressed, temporarily leukopenic rabbit model of invasive aspergillosis. Therapy with SCH at 10 or 15 mg/kg of body weight per day was begun 24 h after lethal challenge and compared with therapy with amphotericin B at 1.5 mg/kg/day. Compared with untreated controls, SCH reduced mortality and also reduced the tissue burden of A. fumigatus 100- to 1,000-fold in liver, kidney, and lung tissues. SCH at 15 mg/kg/day and amphotericin B eliminated A. fumigatus in liver, kidney, and lung tissues. In addition, both dosages of SCH significantly eliminated the organism from brain tissues, compared with controls. Both SCH and amphotericin B decreased or eliminated circulating aspergillus antigen. These results show that new azoles can be as effective as amphotericin B in eradicating the organism from tissues and offer promise in improving the treatment of invasive aspergillosis.     

Efficacy of UK-109496, a new azole antifungal agent, in an experimental model of invasive aspergillosis.

The efficacy of UK-109496, a new azole antifungal agent, was evaluated in an immunosuppressed, temporarily leukopenic rabbit model of invasive aspergillosis. Oral therapy with UK-109496 at a dosage of 10 or 15 mg/kg of body weight every 8 h was begun 24 h after a lethal or sublethal challenge, and results were compared with those for amphotericin B therapy and untreated controls. UK-109496 eliminated mortality and also reduced the tissue burden of Aspergillus fumigatus 10- to 100-fold in liver and kidney tissues and to a lesser degree in lung tissue, and at the higher dose, no viable organisms were recovered from brain tissue from these animals. Both dosages of UK-109496 decreased or eliminated circulating antigen. The half-life of UK-109496 in rabbits was 2.5 to 3 h, and no accumulation of drug was seen even after 15 doses in either uninfected or infected animals. Thus, UK-109496 shows activity in this rabbit model of invasive aspergillosis. Additional studies are needed to determine the potential of the drug for use in the treatment of this infection.     

Comparative analysis of amphotericin B lipid complex and liposomal amphotericin B kinetics of lung accumulation and fungal clearance in a murine model of acute invasive pulmonary aspergillosis

The reformulation of amphotericin B (AMB) into a lipid complex (AMB lipid complex [ABLC]) or liposomal carrier (liposomal AMB [L-AMB]) changes the rate and extent of drug distribution to the lung. The importance of pharmacokinetic differences among the various lipid AMB formulations in the treatment of invasive pulmonary aspergillosis (IPA) remains unknown. We compared the kinetics of AMB lung accumulation and fungal clearance of ABLC- and L-AMB-treated mice with acute IPA. BALB/c mice were immunosuppressed with cyclophosphamide and cortisone before intranasal inoculation with 1.5x10(6) Aspergillus fumigatus 293 conidia. ABLC or L-AMB was administered in daily intravenous doses (1, 5, or 10 mg/kg of body weight), starting 12 h after infection and continuing until day 5. At predetermined times (0, 24, 72, and 120 h), mice were euthanized, and lungs were harvested for determinations of lung fungal burdens (quantitative PCR) and total AMB lung tissue concentrations. Both ABLC and L-AMB were effective at reducing lung fungal burdens at doses of >or=5 mg/kg/day. Clearance of A. fumigatus during the first 24 h was associated with AMB tissue concentrations of >4 microg/g. At 5 mg/kg/day, ABLC produced a more rapid fungal clearance than did L-AMB, but at the end of therapy, fungal burden reductions were similar for both formulations and were not improved with higher dosages. These data suggest that ABLC delivers active AMB to the lung more rapidly than does L-AMB, resulting in faster Aspergillus clearance in an experimental model of IPA. However, pharmacodynamic differences between the two formulations were less apparent when mice were dosed at 10 mg/kg/day.     

Antifungal activity and pharmacokinetics of posaconazole (SCH 56592) in treatment and prevention of experimental invasive pulmonary aspergillosis: correlation with galactomannan antigenemia

The antifungal efficacy, safety, and pharmacokinetics of posaconazole (SCH 56592) (POC) were investigated in treatment and prophylaxis of primary pulmonary aspergillosis due to Aspergillus fumigatus in persistently neutropenic rabbits. Antifungal therapy consisted of POC at 2, 6, and 20 mg/kg of body weight per os; itraconazole (ITC) at 2, 6, and 20 mg/kg per os; or amphotericin B (AMB) at 1 mg/kg intravenously. Rabbits treated with POC showed a significant improvement in survival and significant reductions in pulmonary infarct scores, total lung weights, numbers of pulmonary CFU per gram, numbers of computerized-tomography-monitored pulmonary lesions, and levels of galactomannan antigenemia. AMB and POC had comparable therapeutic efficacies by all parameters. By comparison, animals treated with ITC had no significant changes in outcome variables in comparison to those of untreated controls (UC). Rabbits receiving prophylactic POC at all dosages showed a significant reduction in infarct scores, total lung weights, and organism clearance from lung tissue in comparison to results for UC (P < 0.01). There was dosage-dependent microbiological clearance of A. fumigatus from lung tissue in response to POC. Serum creatinine levels were greater (P < 0.01) in AMB-treated animals than in UC and POC- or ITC-treated rabbits. There was no elevation of serum hepatic transaminase levels in POC- or ITC-treated rabbits. The pharmacokinetics of POC and ITC in plasma demonstrated dose dependency after multiple dosing. The 2-, 6-, and 20-mg/kg dosages of POC maintained plasma drug levels above the MICs for the entire 24-h dosing interval. In summary, POC at > or =6 mg/kg/day per os generated sustained concentrations in plasma of > or =1 microg/ml that were as effective in the treatment and prevention of invasive pulmonary aspergillosis as AMB at 1 mg/kg/day and more effective than cyclodextrin ITC at > or =6 mg/kg/day per os in persistently neutropenic rabbits.     

Continuous versus intermittent administration of ceftazidime in experimental Klebsiella pneumoniae pneumonia in normal and leukopenic rats.

Experimental Klebsiella pneumoniae pneumonia was used to study the influence of cyclophosphamide-induced leukopenia on the relative therapeutic efficacy of continuous and intermittent (6-h intervals) administration of ceftazidime. The antimicrobial response was evaluated with respect to the calculated daily dose that protected 50% of the animals from death (PD50) until 16 days after the termination of a 4-day treatment. When ceftazidime was administered intermittently to leukopenic rats, the PD50 was 24.37 mg/kg per day, 70 times (P less than 0.001) the PD50 of 0.35 mg/kg per day for normal rats. Continuous administration of ceftazidime to leukopenic rats resulted in a PD50 of 1.52 mg/kg per day, four times (P less than 0.001) the PD50 of 0.36 mg/kg per day for normal rats. Continuous administration of ceftazidime in daily doses that protected 100% of normal and leukopenic rats from death resulted in serum levels of 0.06 and 0.38 micrograms/ml, respectively, whereas the MIC for the infecting K. pneumoniae strain was 0.2 micrograms of ceftazidime per ml. The effect of the duration of ceftazidime treatment by continuous infusion on the therapeutic efficacy in relation to the persistence of leukopenia was then investigated in leukopenic rats. The administration of 3.75 mg of ceftazidime/kg per day for 4 days protected all leukopenic rats from death, provided the circulating leukocytes returned at the end of antibiotic treatment. When leukopenia persisted for 8 days this ceftazidime treatment schedule resulted in the mortality of rats (P less than 0.05). However, when ceftazidime treatment was continued for 8 days, until the return of the leukocytes, there was no significant mortality (P greater than 0.05).     

Dose-dependent antifungal activity and nephrotoxicity of amphotericin B colloidal dispersion in experimental pulmonary aspergillosis.

We investigated the safety and efficacy of amphotericin B colloidal dispersion (ABCD) for the treatment of invasive pulmonary aspergillosis in persistently granulocytopenic rabbits. Treatment groups included ABCD in dosages of 1, 5, and 10 mg/kg/day intravenously or conventional desoxycholate amphotericin B (DAmB) at 1 mg/kg/day intravenously. Antifungal activity was directly related to increasing dosage of ABCD as determined by the concentration of Aspergillus fumigatus organisms in lungs and the frequency of hemorrhagic pulmonary lesions. At 5 and 10 mg/kg/day, there was a significant reduction in the tissue burden of A. fumigatus as measured by percent culture-positive lobes and CFU per gram of tissue (P < or = 0.001), whereas at 1 mg/kg/day measured by percent culture-positive lobes and CFU per gram of tissue (P < or = 0.001), whereas at 1 mg/kg/day the tissue burden of A. fumigatus was not significantly different from that in untreated controls. Microbiological clearance was significantly greater at 1 mg of DAmB per kg per day than at 1 mg of ABCD per kg per day (P < or = 0.001). There was no difference in microbiological clearance of bronchoalveolar lavage fluid among the treatment groups as measured by CFU per milliliter. As determined by survival, ABCD at 5.0 mg/kg/day was more effective than DAmB at 1.0 mg/kg/day and ABCD at 10 mg/kg/day. ABCD at 10 mg/kg/day was more nephrotoxic than the lower dosages of ABCD and resulted in higher mortality. Impairment of glomerular filtration developed as a direct function increasing the ABCD dosage (r = 0.77; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Caspofungin prolongs survival of transiently neutropenic rats with advanced-stage invasive pulmonary aspergillosis

A high-dose-step-down strategy for caspofungin treatment was evaluated in an experimental model of advanced-stage invasive pulmonary aspergillosis. The therapeutic efficacy of caspofungin in relation to the severity of invasive pulmonary infection caused by Aspergillus fumigatus in transiently neutropenic rats was investigated by using rat survival and the decrease in the fungal burden as the parameters of efficacy. When treatment was started at either 16 h or 24 h after fungal inoculation, caspofungin administered intraperitoneally at 4 mg/kg of body weight/day for 10 days was highly effective (100% and 93% rat survival, respectively). However, only 27% rat survival was obtained when treatment was started at 72 h, when the rats had advanced-stage infection. Increasing the dose from 4 to 10 mg/kg/day could compensate for the decrease in efficacy and resulted in 67% rat survival. The high dose of 10 mg/kg/day for 10 days did not appear to be necessary since a high-dose-step-down dosing schedule with 10 mg/kg/day for 3 days followed by 4 mg/kg/day for 7 days was equally effective. At 10 days after the end of treatment with 10 mg/kg/day caspofungin, the level of neither A. fumigatus DNA nor A. fumigatus galactomannan in the infected left lung was significantly decreased. In contrast, A. fumigatus galactomannan concentrations in serum were significantly decreased. The levels of creatinine, blood urea nitrogen, alanine aminotransferase, and asparate aminotransferase were not elevated during treatment. Caspofungin is effective for the treatment of invasive pulmonary aspergillosis in transiently neutropenic rats and is even effective in rats with advanced-stage infection. In this model, the administration of high-dose-step-down treatment was as effective as treatment with high doses for the whole treatment period.     

Caspofungin: antifungal activity in vitro, pharmacokinetics, and effects on fungal load and animal survival in neutropenic rats with invasive pulmonary aspergillosis

OBJECTIVES: Evaluation of the potential of caspofungin, in relation to pharmacokinetics, in order to optimize its use in the treatment of filamentous fungal infections. METHODS: The in vitro antifungal activity, pharmacokinetics and therapeutic efficacy of caspofungin versus amphotericin B was investigated in vitro as well as in a model of aerogenic Aspergillus fumigatus infection in neutropenic rats, using rat survival and decrease in fungal burden as parameters for therapeutic efficacy. RESULTS: In contrast to amphotericin B, caspofungin shows a concentration-dependent gradual decrease in fungal growth in vitro, which makes it difficult to perform visual readings of antifungal activity (CLSI guidelines). The quantitative XTT [2,3-bis(2-methoxy-4-nitro-5-[(sulphenylamino) carbonyl]-2H-tetrazolium-hydroxide] assay measuring a decrease in fungal metabolic activity seems more appropriate for caspofungin susceptibility testing. Using this assay, in vitro caspofungin was 4-fold less active than amphotericin B. In the infection model, therapy was started 16 h after fungal inoculation, and continued once daily for 10 days. Caspofungin was administered intraperitoneally at 1, 2, 3 or 4 mg/kg/day (CAS 1, 2, 3 or 4), amphotericin B at 1 mg/kg/day (AMB 1). Treatment with CAS 1 or AMB 1 provided modest prolongation of animal survival. The combination of caspofungin and amphotericin B did not show additive effects. Increasing the dosage of caspofungin to 2, 3 or 4 mg/kg/day resulted in a dose-dependent significant increase in efficacy. There was 100% survival among rats in the CAS 4 group, which was correlated with a significant decrease in fungal burden, based on the concentration of A. fumigatus galactomannan in serum and lung tissue and quantification of A. fumigatus DNA in lung tissue. Pharmacokinetic analysis suggested that the CAS 4 dose in rats produced drug exposure comparable to the human situation, visualized by similar 24 h AUC and trough concentrations. CONCLUSIONS: The therapeutic efficacy of caspofungin is superior to amphotericin B, which seemed to be discrepant with their in vitro antifungal activity.     

Saperconazole therapy in a rabbit model of invasive aspergillosis.

The efficacy of orally and intravenously administered saperconazole against Aspergillus fumigatus was assessed in an immunosuppressed temporarily leukopenic rabbit model of invasive aspergillosis and compared with that of amphotericin B. Oral saperconazole at dosages of 5, 10, and 15 mg/kg of body weight per day improved survival compared with that of controls. In addition, saperconazole at 10 and 15 mg/kg/day reduced the tissue burden and reduced levels of circulating antigen, which correlated with increasing dosages of saperconazole. Intravenous saperconazole produced levels in serum more than 10-fold that of oral therapy. Intravenous saperconazole not only improved survival and reduced antigen levels but also significantly eradicated A. fumigatus from tissues compared with those of controls and was as effective as amphotericin B in these studies. Saperconazole was effective in the treatment of experimental invasive aspergillosis and demonstrates the potential of the newer azoles in therapy for invasive aspergillosis.     

Antifungal Efficacy of Caspofungin (MK-0991) in Experimental Pulmonary Aspergillosis in Persistently Neutropenic Rabbits: Pharmacokinetics, Drug Disposition, and Relationship to Galactomannan Antigenemia

The antifungal efficacy, pharmacokinetics, and safety of caspofungin (CAS) were investigated in the treatment and prophylaxis of invasive pulmonary aspergillosis due to Aspergillus fumigatus in persistently neutropenic rabbits. Antifungal therapy consisted of 1, 3, or 6 mg of CAS/kg of body weight/day (CAS1, CAS3, and CAS6, respectively) or 1 mg of deoxycholate amphotericin B (AMB)/kg/day intravenously for 12 days starting 24 h after endotracheal inoculation. Prophylaxis (CAS1) was initiated 4 days before endotracheal inoculation. Rabbits treated with CAS had significant improvement in survival and reduction in organism-mediated pulmonary injury (OMPI) measured by pulmonary infarct score and total lung weight (P < 0.01). However, animals treated with CAS demonstrated a paradoxical trend toward increased residual fungal burden (log CFU per gram) and increased serum galactomannan antigen index (GMI) despite improved survival. Rabbits receiving prophylactic CAS1 also showed significant improvement in survival and reduction in OMPI (P < 0.01), but there was no effect on residual fungal burden. In vitro tetrazolium salt hyphal damage assays and histologic studies demonstrated that CAS had concentration- and dose-dependent effects on hyphal structural integrity. In parallel with a decline in GMI, AMB significantly reduced the pulmonary tissue burden of A. fumigatus (P < or = 0.01). The CAS1, CAS3, and CAS6 dose regimens demonstrated dose-proportional exposure and maintained drug levels in plasma above the MIC for the entire 24-h dosing interval at doses that were > or =3 mg/kg/day. As serial galactomannan antigen levels may be used for therapeutic monitoring, one should be aware that profoundly neutropenic patients receiving echinocandins for aspergillosis might have persistent galactomannan antigenemia despite clinical improvement. CAS improved survival, reduced pulmonary injury, and caused dose-dependent hyphal damage but with no reduction in residual fungal burden or galactomannan antigenemia in persistently neutropenic rabbits with invasive pulmonary aspergillosis.     

Nebulized amphotericin B combined with intravenous amphotericin B in rats with severe invasive pulmonary aspergillosis

Nebulized amphotericin B (AMB) combined with intravenous AMB was studied in persistently leukopenic rats with invasive pulmonary aspergillosis. Pulmonary concentrations of AMB after aerosol treatment were substantially higher than after intravenous liposomal AMB. Nebulized liposomal AMB in addition to intravenous AMB resulted in significantly prolonged survival compared to controls.     

Comparative study on the efficacy of AmBisome and Fungizone in a mouse model of pulmonary aspergillosis

OBJECTIVES: The aim of this study was to evaluate the efficacy and tissue concentration of AmBisome and Fungizone in murine pulmonary aspergillosis, and to investigate the localization of AmBisome at the infection site. METHODS: Mice were infected intratracheally with Aspergillus fumigatus. A single dose of each of the antifungals was administered intravenously 4 h after infection. The efficacy of the antifungal treatment was assessed by the pulmonary fungal burden at 20 h post-treatment and the survival time over 1 month. The pulmonary amphotericin B (AMB) concentration was measured until 48 h after administration. The distribution of AmBisome in the lung was evaluated using rhodamine-labelled AmBisome and an anti-AMB antibody. RESULTS: AmBisome at a dose of > or =1 mg/kg significantly prolonged the survival time of infected mice compared with the control group. At the maximum tolerated dose, 10 mg/kg AmBisome exhibited greater efficacy than 1 mg/kg Fungizone in terms of increasing survival and reducing the fungal burden. The pulmonary AMB concentration of 10 mg/kg AmBisome was higher than that of 1 mg/kg Fungizone. Tissue distribution analysis showed that AmBisome was localized at the infection site in the lung, and this might explain the potent in vivo efficacy in this infection model. CONCLUSIONS: AmBisome is localized at the infection site in the lung and consequently may fully exhibit its in vivo activity. The efficacy of AmBisome is superior to that of Fungizone against pulmonary aspergillosis.     

Itraconazole preexposure attenuates the efficacy of subsequent amphotericin B therapy in a murine model of acute invasive pulmonary aspergillosis

Antagonism has been described in vitro and in vivo for azole-polyene combinations against Aspergillus species. Using an established murine model of invasive pulmonary aspergillosis, we evaluated the efficacy of several amphotericin B (AMB) dosages given alone or following preexposure to itraconazole (ITC). Mice were immunosuppressed with cortisone acetate and cyclophosphamide. During immunosuppression, animals were administered either ITC solution (50 mg/kg of body weight) or saline by oral gavage twice daily for 3 days prior to infection. Infection was induced by intranasally inoculating mice with a standardized conidial suspension (1 x 10(8) CFU/ml) of Aspergillus fumigatus strain AF 293. AMB was then administered by daily intraperitoneal injections (0.25, 0.5, 1.0, and 3.0 mg/kg) starting 24 h after inoculation and continuing for a total of 72 h. Drug pharmacokinetics of AMB and ITC in plasma were determined by high-performance liquid chromatography. Four different endpoints were used to examine the efficacy of antifungal therapy: (i) viable counts from harvested lung tissue (in CFU per milliliter), (ii) the whole-lung chitin assay, (iii) mortality at 96 h, and (iv) histopathology of representative lung sections. At AMB doses of >0.5 mg/kg/day, fewer ITC-preexposed mice versus non-ITC-preexposed mice were alive at 96 h (0 to 20 versus 60%, respectively). At all time points, the fungal lung burden was consistently and significantly higher in animals preexposed to ITC, as measured by the CFU counts (P = 0.001) and the chitin assay (P = 0.03). Higher doses of AMB did not overcome this antagonism. ITC preexposure was associated with poorer mycological efficacy and survival in mice treated subsequently with AMB for invasive pulmonary aspergillosis.     

Pharmacodynamic activity of amphotericin B deoxycholate is associated with peak plasma concentrations in a neutropenic murine model of invasive pulmonary aspergillosis

We conducted a dose fractionation study of neutropenic, corticosteroid-immunosuppressed mice to characterize the pharmacodynamic/pharmacokinetic (PK/PD) parameter most closely associated with amphotericin B (AMB) efficacy in the treatment of invasive pulmonary aspergillosis. Pharmacokinetic parameter estimates were determined by a nonparametric population pharmacokinetic analysis of plasma drug concentrations following single intraperitoneal doses (0.25, 1.0, and 3.0 mg/kg of body weight) of amphotericin B deoxycholate. Three dosage groups (0.5, 0.75, and 1.0 mg/kg) fractionated into three dosing intervals (every 8 h [q8h], q24h, or q72h) were tested to discriminate between the PK/PD parameters (the ratio of maximum concentration of drug in serum [Cmax]/MIC, the ratio of area under the concentration-time curve/MIC, and percentage of time above MIC) most closely associated with AMB efficacy over a range of clinically achievable exposures in humans. The efficacy of each regimen was determined by quantitative PCR and survival. Reductions in pulmonary fungal burden and improvements in survival were maximized at the highest peak plasma concentrations in each of the dosage groups. Reductions in pulmonary fungal burden and increased survival were most closely associated with Cmax/MIC, with maximal activity occurring as the Cmax/MIC approached 2.4. In our model, Cmax/MIC is the PK/PD parameter most closely associated with efficacy in the treatment of invasive pulmonary aspergillosis. These data predict that less frequently administered, higher dosages of AMB would optimize efficacy.     

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

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.     

Efficacy of aerosolized amphotericin B desoxycholate and liposomal amphotericin B in the treatment of invasive pulmonary aspergillosis in severely immunocompromised rats.

The effects of treatment with aerosolized amphotericin B desoxycholate and aerosolized liposomal amphotericin B were evaluated in severely immunosuppressed rats with invasive pulmonary aspergillosis. Aerosol treatment with amphotericin B desoxycholate consisted of a single dose (60 min) with amphotericin B concentrations in the nebulizer reservoir of 1, 2 and 4 mg/mL, respectively. For liposomal amphotericin B, aerosol treatment consisted of single, double or quadruple doses with a nebulizer reservoir concentration of 4 mg/mL of amphotericin B. Treatment, started at 30 h after inoculation, with aerosolized amphotericin B desoxycholate (nebulizer reservoir concentration 2 mg/mL) significantly prolonged survival of rats as compared with placebo-treated rats, whereas treatment with aerosolized amphotericin B desoxycholate with nebulizer reservoir concentration of 1 or 4 mg/mL did not have a significant effect on survival. Treatment with aerosolized liposomal amphotericin B significantly prolonged survival with all treatment regimens when compared with placebo-treated animals. Aerosol treatment did not prevent dissemination of the infection. The effects of amphotericin B desoxycholate and liposomal amphotericin B on pulmonary surfactant function were also evaluated in vitro. Amphotericin B desoxycholate inhibited surfactant function in a dose-dependent fashion. Liposomal amphotericin B had no detrimental effect on surface activity of surfactant. These results indicate that aerosol administration of amphotericin B, especially the liposomal formulation, could be an additional approach to optimizing treatment of invasive pulmonary aspergillosis.     

Efficacy of caspofungin alone and in combination with voriconazole in a Guinea pig model of invasive aspergillosis

The antifungal activity of caspofungin acetate (CAS) alone and in combination with voriconazole (VRC) was evaluated in an immunosuppressed transiently neutropenic guinea pig model of invasive aspergillosis. Guinea pigs were immunosuppressed with triamcinolone at 20 mg/kg of body weight/day subcutaneously beginning 4 days prior to lethal intravenous challenge with Aspergillus fumigatus and were made temporarily neutropenic with cyclophosphamide administered at 150 mg/kg intraperitoneally (i.p.) 1 day prior to challenge. Therapy with i.p. CAS at 1 and 2.5 mg/kg/day (with and without oral VRC at 5 mg/kg/day), oral VRC at 5 mg/kg/day, or i.p. amphotericin B (AMB) at 1.25 mg/kg/day was begun 24 h after challenge and was continued for 5 days. Mortality occurred in 12 of 12 untreated controls, whereas mortality occurred in 4 of 12 and 6 of 12 guinea pigs treated with CAS at 1 and 2.5 mg/kg/day, respectively, and in 3 of 12 guinea pigs treated with AMB. No mortality occurred among animals treated with CAS at 1 mg/kg/day plus VRC at 5 mg/kg/day, CAS at 2.5 mg/kg/day plus VRC at 5 mg/kg/day, or VRC at 5 mg/kg/day alone. Both CAS regimens increased the survival times and reduced the colony counts in tissue compared with those for the controls. Treatment with VRC and AMB significantly reduced the colony counts in the tissues of selected animals compared with those in the tissues of the controls. Treatment with VRC and AMB also resulted in reductions in colony counts in tissues compared with those in the tissues of animals treated with CAS (the difference was not statistically significant) and improved the survival times but did not sterilize tissues. Combination therapies with CAS plus VRC at either dose reduced colony counts in tissues 1,000-fold over those for the controls and were the only regimens that significantly reduced the numbers of positive cultures. The combinations of CAS plus VRC were highly effective in this model and should be further evaluated for use against invasive aspergillosis.     

Limited protection by small unilamellar liposomes against the renal tubular toxicity induced by repeated amphotericin B infusions in rats.

Amphotericin B (AMB), either alone or incorporated into small unilamellar vesicles of pure dipalmitoylphosphatidyl choline (DPPC SUV-AMB), was administered intravenously to male Sprague-Dawley rats once daily for 5 days. Either 1.5 or 3.5 mg of AMB or DPPC SUV-AMB per kg was given, since these concentrations corresponded, respectively, to the lowest nephrotoxic dose and the sublethal dose of AMB in our model. Tubular functions were evaluated daily, and AMB concentrations in plasma, urine, and tissues were measured by high-performance liquid chromatography. AMB at both doses induced tubular toxicity, hyposthenuria being the earliest symptom. DPPC SUV-AMB at 1.5 mg/kg/day was atoxic, but the tubular alterations induced by 3.5 mg of DPPC SUV-AMB per kg were similar to those observed with 3.5 mg of AMB per kg, except that the ability to concentrate urine was partly restored 72 h after the last infusion. Incorporating AMB into DPPC SUV did not influence the pharmacokinetics of the drug. Using this lipidic AMB formulation, we thus observed a beneficial effect toward limiting the renal tubular toxicity of repeated low doses of AMB but, unexpectedly, not that of high doses. These results indicate that tubular renal functions and electrolyte serum values should be closely monitored in patients treated with AMB liposomal formulations, especially high-dose regimens.     

Efficacy of amphotericin B or itraconazole in a murine model of central nervous system Aspergillus infection

Given the greater than 90% lethality of clinical central nervous system (CNS) aspergillosis despite current therapies, there is a need for an animal model to study therapeutic strategies. We previously established a model of CNS aspergillosis by intracerebral infection and report here the results of treatment with the two therapies with the greatest clinical experience, i.e., treatments with amphotericin B (AMB) and itraconazole (ITZ). Mice were given cyclophosphamide to produce pancytopenia. AMB was given intraperitoneally (i.p.; 3 mg/kg of body weight) or intravenously (i.v.; 0.8 mg/kg) once daily. ITZ in cyclodextrin was given by gavage once daily at a dose of 100 mg/kg or twice daily at 50 mg/kg. Treatments were started at day 1 postinfection and given for 10 days. At day 15, survivors were euthanatized. Ninety percent of the mice given no treatment died by day 6, and 100% died by day 10. Mice treated with AMB either i.p. or i.v. had 40% survival. Mice treated with ITZ either once or twice per day had a median survival time of 10 days, compared with 4 days for control animals, but a survival rate of only 10%. AMB and ITZ prolonged survival (P, <0.0001 to <0.05) compared with controls. Brains from surviving mice had CFU of Aspergillus fumigatus. This model can be used to compare newer antifungals and to study combination therapy or immunotherapy to find better therapeutic alternatives.