Amphotericin B lipid complex therapy of experimental fungal infections in mice

The Anti-Fungal Activity of Nitropropenyl Benzodioxole (NPBD), a Redox-Thiol Oxidant and Tyrosine Phosphatase Inhibitor

Phylogenetically diverse fungal species are an increasing cause of severe disease and mortality. Identification of new targets and development of new fungicidal drugs are required to augment the effectiveness of current chemotherapy and counter increasing resistance in pathogens. Nitroalkenyl benzene derivatives are thiol oxidants and inhibitors of cysteine-based molecules, which show broad biological activity against microorganisms. Nitropropenyl benzodioxole (NPBD), one of the most active antimicrobial derivatives, shows high activity in MIC assays for phylogenetically diverse saprophytic, commensal and parasitic fungi. NPBD was fungicidal to all species except the dermatophytic fungi, with an activity profile comparable to that of Amphotericin B and Miconazole. NPBD showed differing patterns of dynamic kill rates under different growth conditions for Candida albicans and Aspergillus fumigatus and was rapidly fungicidal for non-replicating vegetative forms and microconidia. It did not induce resistant or drug tolerant strains in major pathogens on long term exposure. A literature review highlights the complexity and interactivity of fungal tyrosine phosphate and redox signaling pathways, their differing metabolic effects in fungal species and identifies some targets for inhibition. A comparison of the metabolic activities of Amphotericin B, Miconazole and NPBD highlights the multiple cellular functions of these agents and the complementarity of many mechanisms. The activity profile of NPBD illustrates the functional diversity of fungal tyrosine phosphatases and thiol-based redox active molecules and contributes to the validation of tyrosine phosphatases and redox thiol molecules as related and complementary selective targets for antimicrobial drug development. NPBD is a selective antifungal agent with low oral toxicity which would be suitable for local treatment of skin and mucosal infections.

Biodistribution and histopathology studies of amphotericin B sodium deoxycholate sulfate formulation following intratracheal instillation in rat models

Aerosol inhalation of amphotericin B (AmB) can be a clinically compliant way to administer the drug directly to the pulmonary route for treatment as well as prophylaxis of invasive pulmonary aspergillosis (IPA). We report aerosol formulation of AmB using sodium deoxycholate sulfate (SDCS), a lipid carrier synthesized in-house using natural precursor deoxycholic acid. In vitro toxicity was determined by MTT assay. Biodistribution and histopathology in rats were evaluated in targeted organs including the lungs, kidneys, spleen, and liver. No toxicity was observed when lung and kidney cells treated with AmB-SDCS formulations up to 8 μg/mL and minimal toxicity at higher concentration 16 μg/mL, while the Fungizone®-like formulation induced toxicity to lung and kidney cells with viability decreasing from 86 to 41% and 100 to 49%, respectively, when compared with an equivalent concentration of AmB-SDCS. Renal and hepatic markers were raised for Fungizone®-like formulation-treated rats but not for AmB-SDCS formulations following 7 days of regular dosing by intratracheal instillation. AmB concentrations were highest in the lungs (5.4-8.3 μg/g) which were well above minimum inhibitory concentration (MIC) of all Aspergillus species. Plasma concentration was also above MIC (> 2 μg/mL) for all AmB-SDCS formulations in comparison with Fungizone®-like formulation. No evidence of abnormal histopathology was observed in the lungs, liver, spleen, and kidneys for all AmB-SDCS formulations but was observed for the group treated with Fungizone®-like formulation. It is concluded that AmB-SDCS formulations can be efficiently administered via intratracheal instillation with no evidence of toxicity and may find great value in the treatment as well as prophylaxis of IPA through inhalation route.

Efficacy of a poly-aggregated formulation of amphotericin B in treating systemic sporotrichosis caused by Sporothrix brasiliensis

In severe cases of sporotrichosis, it is recommended to use amphotericin B deoxycholate (D-AMB) or its lipid formulations and/or in association with itraconazole (ITC). Our aim was to evaluate the antifungal efficacy of a poly-aggregated amphotericin B (P-AMB), a nonlipid formulation, compared with D-AMB on systemic sporotrichosis caused by Sporothrix brasiliensis. In vitro assays showed that Sporothrix schenckii sensu stricto and S. brasiliensis yeast clinical isolates were susceptible to low concentrations of P-AMB and D-AMB. Although P-AMB presented a higher minimal inhibitory concentration (MIC) compared to D-AMB, its cytotoxic effect on renal cells and erythrocytes was lower. For the in vivo assays, male BALB/c mice were intravenously infected with S. brasiliensis yeasts, and P-AMB or D-AMB was administered 3 days post-infection. The efficacy of five therapeutic regimens was tested: intravenous monotherapy with P-AMB or D-AMB, intravenous pulsed-therapy with P-AMB or D-AMB, and intravenous therapy with P-AMB, followed by oral ITC. These treatments increased murine survival and controlled the fungal burden in the liver, spleen, lungs, and kidneys. However, only D-AMB monotherapy or the pulsed-therapies with D-AMB or P-AMB led to 100% survival of the mice 45 days post-infection; only pulsed administration of D-AMB was able to control the fungal load in all organs 45 days post-infection. Accordingly, the histopathological findings showed reductions in the fungal burden and inflammatory reactions in these treatment regimens. Together, our results suggest that the P-AMB formulation could be considered as an alternative drug to D-AMB for treating disseminated sporotrichosis.

Target Site Delivery and Residence of Nanomedicines: Application of Quantitative Systems Pharmacology

Quantitative systems pharmacology (QSP), an emerging field that entails using modeling and computation to interpret, interrogate, and integrate drug effects spanning from the molecule to the whole organism to forecast treatment outcomes, is expected to enhance the efficiency of drug development. Since late 2017, the U.S. Food and Drug Administration has advocated the use of an analogous approach of model-informed drug development. This review focuses on issues pertaining to nanosized medicines (NP) and the potential utility of QSP to determine NP delivery and residence at extracellular or intracellular targets in vivo. The kinetic processes governing NP disposition and transport, interactions with biologic matrix components, binding and internalization in cells, and intracellular trafficking are determined, sometimes jointly, by NP properties (e.g., dimension, materials, surface charge and modifications, shape, and geometry) and target tissue properties (e.g., perfusion status, vessel pore size and wall thickness, vessel and cell density, composition of extracellular matrix, and void volume fraction). These various determinants, together with the heterogeneous tissue structures and microenvironment factors in solid tumors, lead to environment-, spatial-, and time-dependent changes in NP concentrations that are difficult to predict. Adding to the complexity is the recent discovery that NP surface-coating protein corona, whose composition depends on NP properties and which undergoes continuous evolution with time and local protein environments, is yet another unpredictable variable. Examples are provided to demonstrate the potential utility of QSP-based multiscale modeling to capture the physicochemical and biologic processes in equations to enable computational studies of the key kinetic processes in cancer treatments.

What Drives Innovation: The Canadian Touch on Liposomal Therapeutics

Liposomes are considered one of the most successful drug delivery systems (DDS) given their established utility and success in the clinic. In the past 40–50 years, Canadian scientists have made ground-breaking discoveries, many of which were successfully translated to the clinic, leading to the formation of biotech companies, the creation of research tools, such as the Lipex Extruder and the NanoAssemblr™, as well as contributing significantly to the development of pharmaceutical products, such as Abelcet^®, MyoCet^®, Marqibo^®, Vyxeos^®, and Onpattro™, which are making positive impacts on patients’ health. This review highlights the Canadian contribution to the development of these and other important liposomal technologies that have touched patients. In this review, we try to address the question of what drives innovation: Is it the individual, the teams, the funding, and/or an entrepreneurial spirit that leads to success? From this perspective, it is possible to define how innovation will translate to meaningful commercial ventures and products with impact in the future. We begin with a brief history followed by descriptions of drug delivery technologies influenced by Canadian researchers. We will discuss recent advances in liposomal technologies, including the Metaplex technology from the author’s lab. The latter exemplifies how a nanotechnology platform can be designed based on multidisciplinary groups with expertise in coordination chemistry, nanomedicines, disease, and business to create new therapeutics that can effect better outcomes in patient populations. We conclude that the team is central to the effort; arguing if the team is entrepreneurial and well positioned, the funds needed will be found, but likely not solely in Canada.

Systemic Bioequivalence Is Unlikely to Equal Target Site Bioequivalence for Nanotechnology Oncologic Products

Approval of generic drugs by the US Food and Drug Administration (FDA) requires the product to be pharmaceutically equivalent to the reference listed drug (RLD) and demonstrate bioequivalence (BE) in effectiveness when administered to patients under the conditions in the RLD product labeling. Effectiveness is determined by drug exposure at the target sites. However, since such measurement is usually unavailable, systemic exposure is assumed to equal target site exposure and systemic BE to equal target site BE. This assumption, while it often applies to small molecule drug products that are readily dissolved in biological fluids and systemically absorbed, is unlikely to apply to nanotechnology products (NP) that exist as heterogeneous systems and are subjected to dimension- and material-dependent changes. This commentary provides an overview of the intersecting and spatial-dependent processes and variables governing the delivery and residence of oncologic NP in solid tumors. In order to provide a quantitative perspective of the collective effects of these processes, we used quantitative systems pharmacology (QSP) multi-scale modeling to capture the physicochemical and biological events on several scales (whole-body, organ/suborgan, cell/subcellular, spatial locations, time). QSP is an emerging field that entails using modeling and computation to facilitate drug development; an analogous approach (i.e., model-informed drug development) is advocated by to FDA. The QSP model-based simulations illustrated that small changes in NP attributes (e.g., size variations during manufacturing, interactions with proteins in biological milieu) could lead to disproportionately large differences in target site exposure, rending systemic BE unlikely to equal target site BE.

Antifungal activity of osthol in vitro and enhancement in vivo through Eudragit S100 nanocarriers

In vitro interaction of osthol (Ost) and fluconazole (FLC) was investigated against 11 fluconazole-resistant clinical isolates of Candida albicans. Synergistic activities were determined using the checkerboard microdilution assay. The results of agar diffusion test confirmed the synergistic interaction. We used an enteric material Eudragit S100 for preparation of Ost nanoparticle (Ost-NP) to improve the oral bioavailability, biological activity of Ost. The physicochemical characteristics of Ost-S100-NP revealed Ost-S100-NP with mean particle size of 55.4±0.4 nm, encapsulation efficiency of 98.95±0.06%, drug loading efficiency of 23.89±0.25%, yield of 98.5±0.1% and a polydispersity index (PDI) of 0.165. As the Ost concentration-time curve showed, Ost-S100-NP can increase the plasma concentration and relative bioavailability of Ost compared with Ost-suspension by oral administration. In vivo, Ost-S100-NP enhanced the therapeutic efficacy of Ost against FLC-resistant C. albicans in immunosuppressed candidiasis mice model. The available information strongly suggests that Ost-S100-NP may be used as a promising compound against drug-resistant fungi.

Efficacy, Biodistribution, and Nephrotoxicity of Experimental Amphotericin B-Deoxycholate Formulations for Pulmonary Aspergillosis

An experimental micellar formulation of 1:1.5 amphotericin B-sodium deoxycholate (AMB:DCH 1:1.5) was obtained and characterized to determine its aggregation state and particle size. The biodistribution, nephrotoxicity, and efficacy against pulmonary aspergillosis in a murine model were studied and compared to the liposomal commercial formulation of amphotericin B after intravenous administration. The administration of 5 mg/kg AMB:DCH 1:1.5 presented 2.8-fold-higher lung concentrations (18.125 ± 3.985 μg/g after 6 daily doses) and lower kidney exposure (0.391 ± 0.167 μg/g) than liposomal commercial amphotericin B (6.567 ± 1.536 and 5.374 ± 1.157 μg/g in lungs and kidneys, respectively). The different biodistribution of AMB:DCH micelle systems compared to liposomal commercial amphotericin B was attributed to their different morphologies and particle sizes. The efficacy study has shown that both drugs administered at 5 mg/kg produced similar survival percentages and reductions of fungal burden. A slightly lower nephrotoxicity, associated with amphotericin B, was observed with AMB:DCH 1:1.5 than the one induced by the liposomal commercial formulation. However, AMB:DCH 1:1.5 reached higher AMB concentrations in lungs, which could represent a therapeutic advantage over liposomal commercial amphotericin B-based treatment of pulmonary aspergillosis. These results are encouraging to explore the usefulness of AMB:DCH 1:1.5 against this disease.

Rodent Models of Invasive Aspergillosis due to Aspergillus fumigatus: Still a Long Path toward Standardization

Invasive aspergillosis has been studied in laboratory by the means of plethora of distinct animal models. They were developed to address pathophysiology, therapy, diagnosis, or miscellaneous other concerns associated. However, there are great discrepancies regarding all the experimental variables of animal models, and a thorough focus on them is needed. This systematic review completed a comprehensive bibliographic analysis specifically-based on the technical features of rodent models infected with Aspergillus fumigatus. Out the 800 articles reviewed, it was shown that mice remained the preferred model (85.8% of the referenced reports), above rats (10.8%), and guinea pigs (3.8%). Three quarters of the models involved immunocompromised status, mainly by steroids (44.4%) and/or alkylating drugs (42.9%), but only 27.7% were reported to receive antibiotic prophylaxis to prevent from bacterial infection. Injection of spores (30.0%) and inhalation/deposition into respiratory airways (66.9%) were the most used routes for experimental inoculation. Overall, more than 230 distinct A. fumigatus strains were used in models. Of all the published studies, 18.4% did not mention usage of any diagnostic tool, like histopathology or mycological culture, to control correct implementation of the disease and to measure outcome. In light of these findings, a consensus discussion should be engaged to establish a minimum standardization, although this may not be consistently suitable for addressing all the specific aspects of invasive aspergillosis.

AmBisome Induced Avascular Necrosis of the Alae of the Nose of a very young girl suffering from Kala-azar - a Case Report

Although liposomal amphotericin B (AmBisome) is considered as the first-line treatment for New Kala-azar, there is not enough evidence on the dosage formulation in children and its effect on them. Being considered as the safest drug for treatment of Kala-azar, this case of AmBisome-induced avascular necrosis now gives rise to the question; whether it is actually safe enough and if a dosage modification is needed in case of children. This so far, to the best of our knowledge, is the first instance of such severe adverse event due to AmBisome administration.

Fungal Infections of the Spine

STUDY DESIGN

Review of the literature.

OBJECTIVE

To retrospectively examine the frequency of published fungal infections by species and the treatment algorithms used to eradicate the disease.

SUMMARY OF BACKGROUND DATA

Fungal infections of the spine present unique challenges to the modern multispecialty treatment team. Although rare in comparison with bacterial infections, fungal infections have been increasing in incidence over the past several decades. Evidences-based practice is limited to referencing smaller case series.

METHODS

MEDLINE, Scopus, and EMBASE searches were carried out by one of the authors as well as by the research desk at the University of Miami/Calder Memorial Library. We included peer-reviewed articles published between 1948 and September 2010; case reports, series, and reviews were all examined and compiled into a database.

RESULTS

A total of 130 articles, representing 157 cases, were included in the review. Aspergillus (60 cases, 38.2% of the total) and Candida species (36 cases, 22.9% of the total) were the 2 most common organisms. Surgery was associated with a greater survival rate than medical management alone in patients with Aspergillus (26.9% mortality in surgical patients; 60% in medically treated patients) and Candida (0% vs. 28.6%). Overall mortality was 19.3%. The overall recurrence rate was 7.4%. Amphotericin use was associated with a higher mortality rate than azoles.

CONCLUSION

Aspergillus is the most common published pathogen in fungal infections of the spine. Recent publications depicting the use of newer antifungal medications such as azoles report higher survival rates. Surgically treated patients in combination with antifungal therapy showed highest frequencies of patient survival in Aspergillus and Candida infections.

LEVEL OF EVIDENCE

3.

Pharmacokinetics and pharmacodynamics of antifungals in children and their clinical implications

Invasive fungal infections are a significant cause of morbidity and mortality in children. Successful management of these systemic infections requires identification of the causative pathogen, appropriate antifungal selection, and optimisation of its pharmacokinetic and pharmacodynamic properties to maximise its antifungal activity and minimise toxicity and the emergence of resistance. This review highlights salient scientific advancements in paediatric antifungal pharmacotherapies and focuses on pharmacokinetic and pharmacodynamic studies that underpin current clinical decision making. Four classes of drugs are widely used in the treatment of invasive fungal infections in children, including the polyenes, triazoles, pyrimidine analogues and echinocandins. Several lipidic formulations of the polyene amphotericin B have substantially reduced the toxicity associated with the traditional amphotericin B formulation. Monotherapy with the pyrimidine analogue flucytosine rapidly promotes the emergence of resistance and cannot be recommended. However, when used in combination with other antifungal agents, therapeutic drug monitoring of flucytosine has been shown to reduce high peak flucytosine concentrations, which are strongly associated with toxicity. The triazoles feature large inter-individual pharmacokinetic variability, although this pattern is less pronounced with fluconazole. In clinical trials, posaconazole was associated with fewer adverse effects than other members of the triazole family, though both posaconazole and itraconazole display erratic absorption that is influenced by gastric pH and the gastric emptying rate. Limited data suggest that the clinical response to therapy may be improved with higher plasma posaconazole and itraconazole concentrations. For voriconazole, pharmacokinetic studies among children have revealed that children require twice the recommended adult dose to achieve comparable blood concentrations. Voriconazole clearance is also affected by the cytochrome P450 (CYP) 2C19 genotype and hepatic impairment. Therapeutic drug monitoring is recommended as voriconazole pharmacokinetics are highly variable and small dose increases can result in marked changes in plasma concentrations. For the echinocandins, the primary source of pharmacokinetic variability stems from an age-dependent decrease in clearance with increasing age. Consequently, young children require larger doses per kilogram of body weight than older children and adults. Routine therapeutic drug monitoring for the echinocandins is not recommended. The effectiveness of many systemic antifungal agents has been correlated with pharmacodynamic targets in in vitro and in murine models of invasive candidiasis and aspergillosis. Further study is needed to translate these findings into optimal dosing regimens for children and to understand how these agents interact when multiple antifungal agents are used in combination.

Recent advances in development of amphotericin B formulations for the treatment of visceral leishmaniasis

PURPOSE OF REVIEW

Amphotericin B (AmpB) is considered the first-line treatment for visceral leishmaniasis in areas in which resistance to antimony is prevalent. This review describes recent advances in clinically available and novel drug delivery systems of AmpB to treat visceral leishmaniasis.

RECENT FINDINGS

Over the past two decades, lipid-based AmpB formulations developed to tackle the toxicity of AmpB have been used clinically for the treatment of visceral leishmaniasis. Liposomal AmpB (AmBisome) has been the most successful lipid formulation, and recent clinical studies on visceral leishmaniasis have shown the potential of single-dose AmBisome treatment as well as its use in short course combinations with other antileishmanial drugs. Current research is focussed on the development of more stable and affordable nonlipid formulations of AmpB. Although a diverse range of nonlipid-based AmpB formulations have been evaluated, none have yet reached the clinic.

SUMMARY

Liposomal AmpB (AmBisome) has become a standard treatment, by intravenous infusion, for visceral leishmaniasis and the basis for new short course treatments. There have been extensive efforts to develop new AmpB formulations on the basis of polymers, lipids or physical aggregates of AmpB to replace the costly lipid-based formulations. However, no nonlipid-based AmpB delivery systems have yet reached the clinic.

Role of diuretics and lipid formulations in the prevention of amphotericin B-induced nephrotoxicity

PURPOSE

To collect available clinical data to define the role of diuretics and lipid formulations in the prevention of amphotericin B (AmB)-induced nephrotoxicity (AIN) in human populations.

METHOD

A literature search was performed in the following databases: Scopus, Medline, Embase, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews.

RESULTS AND CONCLUSION

Co-administration of mannitol failed to show any clinically significant benefit in preventing AIN. Potassium-sparing diuretics, such as amiloride and spironolactone, have been shown to have beneficial effects as an alternative or adjunct to oral/parenteral potassium supplements in preventing hypokalemia due to AmB. Lipid-based formulations of AmB are clinically effective and safe in preventing AIN. However, due to their high cost and limited accessibility, these formulations are generally used as second-line antifungal therapy in cases of conventional AmB refractoriness and/or intolerance or pre-existing renal dysfunction. The potential effects of other nephroprotective agents, such as N-acetylcysteine, AIN merit further considerations and investigations.

Antifungal therapy and outcomes in infants with invasive Candida infections

BACKGROUND

Invasive candidiasis is a leading cause of mortality and morbidity in neonatal intensive care units. Treatment recommendations are limited by a lack of comparative outcomes data.

METHODS

We identified all infants ≤ 120 days of age with positive blood, urine, or cerebrospinal fluid cultures for Candida species who received amphotericin B deoxycholate, fluconazole, amphotericin B lipid products, or combination therapy admitted to one of 192 neonatal intensive care units in the United States between 1997 and 2003. Primary outcome measures included overall mortality and therapeutic failure (combined outcome of duration of infection >7 days, need for additional antifungal therapy, or death before discharge). We compared outcomes by antifungal therapy using logistic regression, controlling for gestational age, day of life at start of antifungal therapy, delay in therapy, and site of infection.

RESULTS

Overall, 138 of 730 (19%) infants died. On multivariable logistic regression, we observed higher overall mortality for infants receiving amphotericin B lipid products compared with infants receiving amphotericin B deoxycholate (odds ratio 1.96 [95% confidence intervals: 1.16, 3.33]; P = 0.01) or fluconazole (odds ratio 2.39 [1.18, 4.83]; P = 0.02).

CONCLUSIONS

Infants treated with amphotericin B lipid products had higher mortality than infants treated with either amphotericin B deoxycholate or fluconazole. This finding may be related to inadequate penetration of amphotericin B lipid products into the kidneys, inappropriate dosing in premature infants, or unknown differences in acuity of illness in infants treated with amphotericin B lipid products.

A dry powder formulation of liposome-encapsulated recombinant secretory leukocyte protease inhibitor (rSLPI) for inhalation: preparation and characterisation

Inhaled recombinant secretory leukocyte protease inhibitor (rSLPI) has shown potential for the treatment of inflammatory lung conditions. Rapid inactivation of rSLPI by cathepsin L (Cat L) and rapid clearance from the lungs has limited clinical efficacy to date. Previous studies by us have shown that encapsulation of rSLPI within1,2-dioleoyl-sn-glycero-3-[phospho-L-serine]/cholesterol (DOPS/Chol) liposomes protects rSLPI against Cat L inactivation in vitro. Liquid DOPS-rSLPI preparations were found to be unstable upon long-term storage and nebulisation. The aim of this study was therefore to develop a method of manufacture for preparing DOPS-rSLPI liposomes as a dry powder for inhalation. DOPS-rSLPI dry powders were lyophilised and subsequently micronised with a novel micronisation aid. The effects of formulation and processing on rSLPI stability, activity, and uniformity of content within the powders were characterised. Using D-mannitol as the micronisation aid, dry powder particles in the inhalable size range (<5 μm) were prepared. By optimising process parameters, up to 54% of rSLPI was recovered after micronisation, of which there was no significant loss in anti-neutrophil elastase activity and no detectable evidence of protein degradation. Aerosolisation was achieved using a dry powder inhaler, and mass median aerodynamic diameter (MMAD) was evaluated after collection in a cascade impactor. Aerosolisation of the DOPS-rSLPI dry powder yielded 38% emitted dose, with 2.44 μm MMAD. When challenged with Cat L post-aerosolisation, DOPS-rSLPI dry powder was significantly better at retaining a protective function against Cat L-induced rSLPI inactivation compared to the aqueous DOPS-rSLPI liposome dispersion and was also more stable under storage.

Amphotericin B Lipid Complex (Abelcet) in the treatment of invasive mycoses: the North American experience

Abelcet, or Amphotericin B lipid Complex, is unique formulation, comprising an equimolar mixture of amphotericin B complexed with two lipids. In preclinical studies, Abelcet was clearly demonstrated to be less toxic than amphotericin B desoxycholate and to be effective in models where amphotericin B was ineffective at its maximum tolerated dose. Pharmacokinetic studies in animals also showed that the concentration of Abelcet in blood is similar or reduced compared to levels seen with conventional amphotericin B, with accumulation in the liver, lungs and spleen. Phase I clinical trials determined the optimum tolerated dose of Abelcet to be 5 mg/kg d-1. Data are now available for 228 cases (including 51 paediatric cases) of invasive fungal infection treated with Abelcet in an open-label emergency-release protocol. All patients had to have failed on previous amphotericin B or other conventional antifungals, or to have unacceptable toxicity on amphotericin B, or underlying renal disease, or nephrotoxicity due to other drugs. Abelcet was administered at a dose of 5 mg/kg d-1 for 4 wk. Approximately one-third of patients had candidiasis, one-third aspergillosis and one-third other infections, including fusariosis. Of 183 cases evaluable for response, 126 (69%) had a clinical response (cure or improvement) which was mycologically confirmed in 55% (61/110 tested). Results in paediatric cases were similar to or better than those seen in the group as a whole. When comparisons were made between cases with different types of infection, underlying disease/immunosuppressive disorder, and degree of neutropenia, the response rates were very consistent from group to group. Treatment with Abelcet was well tolerated and mean serum creatinine levels actually declined during therapy, particularly in patients with pre-existing renal dysfunction.

Amphotericin B lipid preparations: what are the differences?

To reduce the in-vivo toxicity of the broad-spectrum antifungal drug amphotericin B, various lipid formulations of amphotericin B, ranging from lipid complexes to small unilamellar liposomes, have been developed and subsequently commercialized. These structurally diverse formulations differ in their serum pharmacokinetics as well as their tissue localisation, tissue retention and toxicity. These differences can affect the choice of formulation for a given infection, the time of initiation of treatment, and the dosing regimen. Although preclinical studies have shown similarities in the in-vitro and in-vivo antifungal activity of the formulations with comparable dosing, their acute and chronic toxicity profiles are not the same, and this has a significant impact on their therapeutic indices, especially in high-risk, immunosuppressed patients. With the recent introduction of new antifungal drugs to treat the increasing numbers of infected patients, the amphotericin B lipid formulations are now being studied to evaluate their potential in combination drug regimens. With proven efficacy demonstrated during the past decade, it is expected that amphotericin B lipid formulations will remain an important part of antifungal drug therapy.

Efficient clearance of Aspergillus fumigatus in murine lungs by an ultrashort antimicrobial lipopeptide, palmitoyl-lys-ala-DAla-lys

Aspergillus fumigatus is an opportunistic fungal pathogen responsible for invasive aspergillosis in immunocompromised individuals. The inefficiency of antifungal agents and high mortality rate resulting from invasive aspergillosis remain major clinical concerns. Recently, we reported on a new family of ultrashort cationic lipopeptides active in vitro against fungi. Mode of action studies supported a membranolytic or a detergent-like effect. Here, we screened several lipopeptides in vitro for their anti-A. fumigatus activity. To investigate the therapeutic properties of the selected peptides in vivo, we challenged immunosuppressed C57BL/6 wild-type mice intranasally with DsRed-labeled A. fumigatus conidia and subsequently treated the animals locally with the lipopeptides. Confocal microscopic analysis revealed the degradation of DsRed-labeled hyphal forms and residual conidia in the lungs of the mice. The most efficient peptide was tested further using a survival assay and was found to significantly prolong the life of the treated animals, whereas no mice survived with the current standard antifungal treatment with amphotericin B. Moreover, as opposed to the drug-treated lungs, the peptide-treated lungs did not display any toxicity of the peptide. Our results highlight the potential of this family of lipopeptides for the treatment of pulmonary invasive aspergillosis.

Amphotericin B Formulations and Drug Targeting

Amphotericin B is a low-soluble polyene antibiotic which is able to self-aggregate. The aggregation state can modify its activity and pharmacokinetical characteristics. In spite of its high toxicity it is still widely employed for the treatment of systemic fungal infections and parasitic disease and different formulations are marketed. Some of these formulations, such as liposomal formulations, can be considered as classical examples of drug targeting. The pharmacokinetics, toxicity and activity are clearly dependent on the type of amphotericin B formulation. New drug delivery systems such as liposomes, nanospheres and microspheres can result in higher concentrations of AMB in the liver and spleen, but lower concentrations in kidney and lungs, so decreasing its toxicity. Moreover, the administration of these drug delivery systems can enhance the drug accessibility to organs and tissues (e.g., bone marrow) otherwise inaccessible to the free drug. During the last few years, new AMB formulations (AmBisome, Abelcet, and Amphotec) with an improved efficacy/toxicity ratio have been marketed. This review compares the different formulations of amphotericin B in terms of pharmacokinetics, toxicity and activity and discusses the possible drug targeting effect of some of these new formulations.

Efficacy of alternative dosing regimens of poly-aggregated amphotericin B

A new poly-aggregated form of amphotericin B was formulated as a non-microencapsulated form (P-AMB) or incorporated in albumin microspheres (MP-AMB) and compared with the conventional amphotericin B formulation (D-AMB). Mice were infected with Candida albicans and treated with two different intermittent dose regimens of the different amphotericin B formulations. Efficacy and toxicity were studied by the determination of survival rate, kidney colony-forming units counts, biochemical parameters and amphotericin B concentrations in plasma and organs. All the treatments significantly (P<0.05) increased the survival rate in relation to the untreated group, although non-statistically significant differences (P>0.05) were found between formulations and dosing regimens. All the treatments produced kidney toxicity, expressed by high urea levels. Kidney toxicity was especially significant for mice treated with the D-AMB formulation where unilateral kidney atrophy was observed in most of the mice, whereas most of the mice treated with P-AMB conserved both kidneys with a normal size and appearance. At 45 days post infection, variable distribution of amphotericin B in the body was obtained depending on the amphotericin B formulation. In conclusion, non-daily dosing regimens of P-AMB, which is less toxic than D-AMB, could be used as an alternative to the conventional D-AMB formulation to treat experimental candidiasis.

Comparison of the physicochemical, antifungal, and toxic properties of two liposomal amphotericin B products

Small unilamellar amphotericin B liposomes can reduce the toxicity of amphotericin B. In this study, we compared the physical, antifungal, pharmocokinetic, and toxic properties of two liposomal amphotericin B products, AmBisome and Anfogen, that have the same chemical composition but are manufactured differently. In vitro tests included determinations of the MICs and the concentrations causing the release of 50% of the intracellular potassium from red blood cells (K50 values) to assess toxicity. The 50% lethal dose (LD50) was evaluated by using uninfected C57BL/6 mice and single intravenous (i.v.) doses of 1 to 100 mg/kg of body weight. Multiple i.v. dosing over 18 days was performed with 0.5, 1.0, or 5.0 mg of Anfogen/kg or 1.0, 5.0, or 25 mg of AmBisome/kg to evaluate chronic toxicity. DBA/2 mice were infected intranasally with 2.5 x 10(6) Aspergillus fumigatus conidia, treated for 3 or 4 days with 3.0, 5.0, or 7.5 mg of Anfogen/kg or 3, 5, 7.5, or 15 mg of AmBisome/kg, and evaluated to assess the toxicity of the drugs to the kidneys (by measurement of blood urea nitrogen and creatinine levels and histopathology) and the drug efficacy. The median particle size was 77.8 nm for AmBisome and 111.5 nm for Anfogen. In vitro K(50) values were significantly lower for Anfogen (0.9 mug/ml) than for AmBisome (20 microg/ml), and the LD50 of AmBisome was >100 mg/kg, versus 10 mg of Anfogen/kg. There was significant renal tubular necrosis in uninfected and infected mice given Anfogen but no tubular necrosis in AmBisome-treated mice. AmBisome at 7.5 or 15 mg/kg was also more efficacious than 7.5 mg of Anfogen/kg for the treatment of pulmonary aspergillosis, based on survival and weight loss data and numbers of CFU per gram of lung. In conclusion, the efficacy and toxicity of these two liposomal amphotericin B products were significantly different, and thus, the products were not comparable.

Atualização no uso de agentes antifúngicos

Aborda-se sumariamente o espectro de ação, aspectos farmacológicos e toxicológicos e eficácia clínica de anfotericina B lipossomal, anfotericina B em dispersão coloidal, complexo lipídico de anfotericina B, voriconazol e caspofungina. Discute-se o uso desses antifúngicos mais recentes considerando a segurança, a eficiência e o custo da terapia. Sugestões para o uso clínico dessas drogas em infecções pulmonares e sistêmicas são apresentadas, destacando-se a menor toxicidade das formulações lipídicas da anfotericina B em relação à medicação convencional, a possibilidade de terapia primária da aspergilose invasiva, scedosporiose e fusariose com voriconazol e a caspofungina como opção terapêutica na candidíase disseminada e na aspergilose invasiva.

Comparative efficacies, toxicities, and tissue concentrations of amphotericin B lipid formulations in a murine pulmonary aspergillosis model

Invasive aspergillosis, an important cause of morbidity and mortality in immunosuppressed (IS) patients, is often treated with amphotericin B lipid formulations. In the present study, liposomal amphotericin B (L-AMB) and amphotericin B lipid complex (ABLC) were compared in treatment of murine pulmonary aspergillosis. Uninfected, IS mice were treated for 4 days with 1, 4, 8, or 12 mg L-AMB or ABLC/kg of body weight, and their lungs were analyzed by high-performance liquid chromatography for drug concentrations. IS mice intranasally challenged with Aspergillus fumigatus were treated with 12, 15, or 20 mg/kg L-AMB or ABLC and monitored for survival, fungal burden (CFU), and tissue drug concentration. Blood urea nitrogen (BUN) levels and kidney histopathology were determined for uninfected and infected mice given 15 or 20 mg/kg L-AMB or ABLC. The results showed that both drugs had therapeutic levels of drug (>3.0 microg/g) in the lungs of uninfected or infected mice, and 24 h after the last dose, ABLC levels were significantly higher than L-AMB levels (P < 0.02). L-AMB and ABLC at 12 mg/kg both produced 57% survival, but only L-AMB at 15 or 20 mg/kg further increased survival to 80 to 90%, with BUN levels and kidney morphology similar to those of controls. Survival at 15 or 20 mg/kg ABLC was not significantly different than that of controls, and BUN levels were significantly elevated, with tubular alterations in uninfected animals and acute necrosis in kidney tubules of infected animals. In conclusion, although both drugs were effective in prolonging survival at 12 mg/kg, the reduced nephrotoxicity of L-AMB increased its therapeutic index, allowing for its safe and effective use at 15 or 20 mg/kg.

Recommendations for managing Aspergillus osteomyelitis and joint infections based on a review of the literature

OBJECTIVES

To produce recommendations for the management of Aspergillus osteomyelitis and joint infections.

METHODS

Published literature was surveyed to identify both case reports of Aspergillus osteomyelitis and joint infections and anti-fungal pharmacology of anti-fungal agents. Included in the pharmacological review was an assessment of new and investigational anti-fungals to consider their potential role in the management of this infection.

RESULTS

Successful treatments, identified from the cases reviewed, were based on combination anti-fungal therapy with one agent having good bone penetration and one having reliable anti-Aspergillus activity.

CONCLUSIONS

For the management of serious Aspergillus osteomyleitis/joint infections amphotericin B in combination with flucytosine is recommended. A number of second line treatment combinations are identified. Monotherapy is appropriate with an azole in clinically stable patients.

Liposomal amphotericin B: clinical experience and perspectives

While amphotericin B deoxycholate (Fungizone, Apothecon Pharmaceuticals) has been considered by many to be the gold standard for the treatment for numerous invasive fungal infections for over 45 years, toxicities associated with its use often necessitate treatment modification or discontinuation. Lipid-based formulations, including liposomal amphotericin B (AmBisome, Fujisawa Healthcare, Inc.), were developed to decrease many of these toxicities while retaining broad antifungal spectrum and potency of amphotericin B. In clinical trials, liposomal amphotericin B has demonstrated efficacy comparable to that of amphotericin B deoxycholate while reducing the incidence of treatment-related nephrotoxicity, electrolyte-wasting, and infusion-related reactions. In addition, recent clinical trials have also compared liposomal amphotericin B with other antifungal classes. Acquisition costs of liposomal amphotericin B are substantially higher than those of amphotericin B deoxycholate and other antifungals. While pharmacoeconomic analyses consider outcomes and other treatment-related costs, they have yet to clearly demonstrate the cost-effectiveness of liposomal amphotericin B when compared with amphotericin B deoxycholate or other antifungal agents. This review will focus primarily on recent liposomal amphotericin B experience and attempt to put its use into perspective considering other available antifungal agents.

Use of liposomized tetracycline in elimination of Wolbachia endobacterium of human lymphatic filariid Brugia malayi in a rodent model

Wolbachia bacteria, being filarial parasite symbiont have been implicated in a variety of roles, including development, fecundity and the pathogenesis of the filarial infections. Among various strategies used in the treatment of experimental filariasis, the elimination of symbiont Wolbachia seem to offer an efficient means of curing the disease. The antiwolbachial property of tetracycline has been well worked out; however, treatment needs to be continued for a prolonged period of time to achieve complete elimination of Wolbachia from the filarial parasites and their subsequent killing. This results in acute toxicity, thus limiting its practical utility for clinical implementation. In order to increase efficacy of the antibiotic with minimal toxic manifestations, we developed liposomized formulation of the tetracycline. The liposomized tetracycline was found to be significantly more effective when compared to the free form of the drug. In contrast to the 90/120 days oral administration of the drug, the treatment schedule using the liposomized form of the drug was reduced to 12 alternate days with better efficacy of the treatment.

Efficacy of Abelcet and caspofungin, alone or in combination, against CNS aspergillosis in a murine model

OBJECTIVES

Currently, few options exist to treat central nervous system (CNS) aspergillosis, which is usually fatal. We tested the efficacy of Abelcet and caspofungin, alone and in combination for treatment of this disease.

METHODS

Male CD-1 mice were immunosuppressed with 200 mg/kg cyclophosphamide 2 days prior to infection and every 5 days thereafter. In the first study, mice were infected intracerebrally with 2.1 x 10(6) conidia/mouse of Aspergillus fumigatus; 10 days of once daily therapy began one day later. Groups of 10 received 0.8, 4, or 8 mg/kg of Abelcet, intravenously (iv), or caspofungin, intraperitoneally, 0.8 mg/kg of conventional amphotericin B (AmB) iv, or no treatment. In a second study, mice were challenged with 6.4 x 10(6) conidia and given no treatment, 8 mg/kg of Abelcet or caspofungin, alone or in combination. On day 14, cfu were determined in survivors by plating of organ homogenates.

RESULTS

In the first study, mice given any regimen of Abelcet or caspofungin had a survival rate > or =80% whereas untreated had 90% mortality. All drug regimens prolonged survival (P < or = 0.0008) and reduced cfu (P < or = 0.0001-0.003) recovered from the brains and kidneys compared with untreated. Abelcet showed an apparent dose-related reduction of cfu in the brains. Abelcet at 4 or 8 mg/kg were equivalent to AmB in reducing cfu from both organs (P > 0.05); AmB was superior to 0.8 mg/kg of Abelcet in the brain only (P < 0.02). Abelcet at 8 mg/kg or AmB at 0.8 mg/kg were superior to all regimens of caspofungin in reducing cfu (P < or = 0.05-0.001). In the second study, Abelcet alone significantly prolonged survival and reduced cfu in the organs versus the controls. Caspofungin did not significantly prolong survival or reduce cfu in comparison with the controls. In combination, Abelcet and caspofungin were equivalent to Abelcet alone.

CONCLUSIONS

Abelcet proved to be efficacious, but not curative, in the treatment of CNS aspergillosis and was equivalent overall to conventional AmB. Caspofungin was not as effective against the larger inoculum, but did not enhance or interfere with the efficacy of Abelcet. Since Abelcet displayed dose-responsive efficacy, it is possible higher doses could produce superior results, yet not show toxicity.

Chronic disseminated candidiasis in patients with acute leukemia: emphasis on diagnostic definition and treatment

BACKGROUND

Chronic disseminated candidiasis (CDC) is a form of invasive fungal infection that occurs most commonly in patients with acute leukemia treated with chemotherapy. Recent studies have provided evidence for diagnostic alternatives to invasive procedures and more therapeutic options for the management of this complication. In order to put diagnostic criteria and methodological approach to the disease into the perspective of developing strategies for therapy, all relevant studies published in the English literature over the last 30 years were examined.

MATERIALS AND METHODS

The English-language articles located through MEDLINE (1966 to present) and from selected bibliographies.

RESULTS

There is increased recognition of CDC as complication of treatment with chemotherapy in patients with acute leukemia. Liver biopsy may not always be revealing or feasible to perform in some patients. Among the imaging modalities, magnetic resonance imaging has obtained preeminence as a non-invasive tool for the diagnosis of hepatosplenic fungal infections. Administration of amphotericin B (Amp B) in relatively large cumulative doses is needed to ensure appropriate control of the infection and prevention of future relapse. Patients intolerant of, or refractory to conventional Amp B have been successfully salvaged using fluconazole or lipid formulations of Amp B. A constellation of clinical, laboratory and radiologic parameters should be used to determine response and efficacy of therapy. There is sufficient evidence to support the safety and feasibility of continuing chemotherapy for acute leukemia in conjunction with antifungal treatment in patients diagnosed with CDC.

CONCLUSION

The development of CDC in patients with acute leukemia does not preclude further chemotherapy or constitute contraindication for bone marrow transplantation. Knowledge of the course and pattern of evolution of the disease and adopting aggressive therapeutic approach will likely reduce the morbidity and mortality from this complication.

Comparative efficacies of four amphotericin B formulations--Fungizone, amphotec (Amphocil), AmBisome, and Abelcet--against systemic murine aspergillosis

We compared various amphotericin B formulations (no treatment or 0.8 mg of Fungizone [conventional deoxycholate amphotericin B] per kg of body weight, or 0.8, 4, or 8 mg of Amphocil, AmBisome, or Abelcet per kg of body weight) for treatment of systemic murine aspergillosis. In two studies, all formulations prolonged survival, with the results for AmBisome nearly equivalent to those for Fungizone; Amphocil and Abelcet were less effective or equivalent depending on the severity of infection. No survivors were cured in both kidneys and brain, but each formulation showed efficacy, especially in the kidneys. Although higher doses could be given, no lipid-based formulation showed consistent superiority over Fungizone or over each other.

Amphotericin B lipid complex for the treatment of invasive fungal infections

Amphotericin B lipid complex (ABLC; Abelcet, Enzon Pharmaceuticals) has become the dominant marketed lipid amphotericin B compound to emerge since the approval of these agents from the mid-1990s onwards. This agent is a 1:1 combination of amphotericin B and a lipid moiety consisting of dimyristoyl phosphatidylcholine and dimyrisoyl phosphatidylcholine, which exists in a ribbon-like molecular structure. ABLC undergoes rapid reticuloendothelial uptake from the circulation and achieves significantly higher tissue concentrations in the liver, spleen and lung compared to comparably dosed conventional amphotericin B. ABLC is approved by the FDA for all mycoses in amphotericin B-intolerant or -refractory infection. Randomised, controlled trials of amphotericin B have shown comparable efficacy in candidiasis and an improved outcome in invasive aspergillosis versus historical controls. ABLC has demonstrated a reduced incidence of nephrotoxicity and infusion reactions versus amphotericin B. Comparative studies against other lipid formulations are quite limited and have shown variable differences in infusion toxicity, nephrotoxicity, hepatotoxicity and clinical efficacy. Postapproval experience has shown substantial efficacy for less common mycotic pathogens including zygomycosis. The precise position of ABLC versus both other lipid formulations and expanding formulary of new antifungal agents is in flux. Future studies which examine its clinical efficacy, role in combination therapy, toxicity and cost-effectiveness in these complex patients are needed.

The lipid formulations of amphotericin B

Amphotericin B spectrum covers most of the fungal pathogens involved in human diseases. Its use is limited by infusion-related effects and nephrotoxicity. As a result of strong lipophilic properties, encapsulation in liposomes or binding to lipid complexes led to the development of lipid formulations in an attempt to increase both efficacy and safety. Three lipid formulations of amphotericin B are commercially available: a liposomal preparation, a lipid complex and a colloidal dispersion. They differ in their lipid composition, shape, pharmacokinetic behaviour and clinical effects. The nephrotoxicity of these formulations is significantly decreased compared to their parent compound. Infusion-related events are lowest with liposomal amphotericin B. Increased efficacy of the lipid formulations over conventional amphotericin B, however, still has to be demonstrated. These formulations are mainly indicated for the treatment of documented fungal infections in patients failing conventional amphotericin B or with renal impairment. Liposomal amphotericin B is also indicated for empirical therapy of suspected fungal infections in febrile neutropenic patients giving this compound an advantage over the two other formulations. Lipid formulations of amphotericin B are extremely expensive. Whether the increase in cost translates into a long-term benefit for the patient is still unknown.

Amphotericin B: time for a new "gold standard"

When introduced in 1959, amphotericin B deoxycholate (AmBD) was clearly a life-saving drug. Randomized studies demonstrating its efficacy were not thought to be necessary, and it was granted indications for many invasive fungal infections. Despite its formidable toxicities, AmBD is thus often used as the primary comparator in studies of invasive fungal infections. Safer lipid-based versions of amphotericin B (AmB) have been introduced, but difficulties with studying these agents generally led to licensure for salvage therapy, not primary therapy. However, the cumulative clinical experience to date with the lipid-based preparations is now adequate to demonstrate that these agents are no less active than AmBD, and, for some infections, it can now be stated that specific lipid-based preparations of AmB are superior to AmBD. Given their superior safety profiles, these preparations can now be considered suitable replacements for AmBD for primary therapy for many invasive fungal infections in clinical practice and research.

Update on antifungal therapy

Fungal pathogens are becoming increasingly important for human and small animal medicine. This article highlights many standards-of-care and new agents for treatment of these pathogens for small animals and people.

Physicochemical properties of amphotericin B liposomes prepared by reverse-phase evaporation method

The physicochemical properties of phosphatidylcholine-cholesterol liposomes containing amphotericin B and prepared by reverse-phase evaporation method were studied. Uniformly dispersed liposomal suspensions were obtained by employing 3:1 ratio (by volume) of diethyl ether to normal saline, 5 min sonication time at 7 degrees C, and evaporation of diethyl ether at 25 degrees C. Microscopic examination showed that the prepared liposomes were spheroids with unilamellar, oligolamellar, or multilamellar structure. The liposomes containing amphotericin B 2.0 mol% of total lipid led to the highest percentage of drug entrapment. Liposomes with maximum entrapment efficiency were obtained from using 250 micromol of total lipid. The liposomal amphotericin B possessing the highest drug entrapment efficiency (approximately 95%) with particle size range of 1307-1451 nm was the one composed of 1:1 molar ratio of phosphatidylcholine to cholesterol.

Amphotericin B/emulsion admixture interactions: an approach concerning the reduction of amphotericin B toxicity

Mixing Fungizone with a fat emulsion used for nutritional purpose (Intralipid or Lipofundin ) was reported to decrease Amphotericin B (AmB) toxicity in clinical use. In an effort to understand the reason for this phenomenon, spectral and morphological analyses were done for the Fungizone and Fungizone /Lipofundin admixture (FLmix). The absorption spectra analyses showed that not only Fungizone but also FLmix presented spectra that were concentration dependent. Moreover, the spectra of FLmix remained stable until the concentration of 5 x 10(-7) M, and only at 5 x 10(-8) M did they become similar in shape to the Fungizone spectra. Morphological studies revealed that even though emulsion droplets with or without Fungizone presented the same particle size, the former was less electron dense compared with Lipofundin alone. These results suggest a kind of association between Fungizoneand Lipofundin that remains over the whole range of concentrations. This hypothesis was confirmed by in vitro studies in which FLmix presented an important selectivity against human and fungal cells compared with Fungizone. These findings suggest that parenteral emulsions should be able to reduce the AmB toxicity probably by changing the AmB self-association state by binding it with emulsion droplets.

Elongated supramolecular assemblies in drug delivery

This review presents different lipid-based elongated microstructures: tubules, cochleate cylinders and ribbons. Their composition, process of preparation and the mechanism behind their formation is discussed as well as their use as a drug delivery system.

Successful treatment of invasive mould infection affecting lung and brain in an adult suffering from acute leukaemia

We describe in detail a 67-yr-old woman who was treated with a cytostatic combination chemotherapy for newly diagnosed common-acute lymphoblastic leukaemia. At the end of induction therapy, the patient acquired invasive mould infection affecting lung and brain. The patient entered complete remission of her leukaemia. Treatment with liposomal amphotericin B was initiated along with surgical excision of the fungal brain abscess. Intrathecal instillation of amphotericin B deoxycholate was started using an Ommaya reservoir because of an anatomical connection between the postoperative cavity and the ventricle. Full dose cytostatic chemotherapy was continued with little delay. A computerised tomography scan of the chest performed 2 months later revealed no fungal abscesses. Magnetic resonance imaging of the brain did not reveal any fungal manifestation. During maintenance therapy/week 69, the patient relapsed from leukaemia. High doses of intravenous liposomal amphotericin B were administered prophylactically. The patient's leukaemia proved refractory to reinduction chemotherapy and the patient died from pneumonia 8 wk later. Post mortem microbiological investigation and histopathological examination of lung and brain tissue did not reveal any macroscopical or microscopical fungal manifestations. This case underlines the feasibility and successful application of combined antileukaemic, antifungal and surgical therapy in a patient with acute leukaemia.

The role of murine models in the development of antifungal therapy for systemic mycoses

Animal testing is crucial to the development of new antifungal compounds. This review describes the role that murine and other animal models have played in the development of three classes of antifungal agents: the polyenes, the triazoles and the echinocandins and the ways in which these models have been either the positive link in the path from in vitro studies to the patient, or have foreclosed later clinical evaluation. Efficacy studies in particular mycoses are discussed, as well as studies designed to determine whether combinations of antifungal drugs may have value over single agents. Copyright 2000 Harcourt Publishers Ltd.

Activities of an intravenous formulation of itraconazole in experimental disseminated Aspergillus, Candida, and Cryptococcus infections

An intravenous (i.v.) formulation of itraconazole was evaluated in disseminated fungal infection models in guinea pigs. In acute disseminated Candida albicans and Aspergillus fumigatus infections, treatment at 5 mg/kg of body weight twice a day (b.i.d.) significantly prolonged survival. In these models and in animals with chronic disseminated cryptococcosis, itraconazole given i.v. at 2.5 and 5 mg/kg b.i.d. greatly reduced the proportions of organs with culture-detectable fungal burdens. The efficacy of i.v. itraconazole in these animal models justifies its further investigation for the treatment of life-threatening mycoses in humans.

In vivo activity of amphotericin B lipid complex in immunocompromised mice against fluconazole-resistant or fluconazole-susceptible Candida tropicalis

We compared four doses of amphotericin B lipid complex (ABLC) with three doses of fluconazole in temporarily neutropenic mice in a murine model of disseminated candidiasis due to four different isolates of Candida tropicalis. The mice were infected with a 90% lethal dose of four strains of C. tropicalis for which the fluconazole MICs ranged from 1 to >125 mg/liter 3 days after receiving 200 mg of cyclophosphamide/kg of body weight. Treatment was started 18 h after infection and lasted for 7 days. ABLC (1, 2, 5, and 10 mg/kg) was administered once a day intravenously, fluconazole was administered by oral gavage once daily (25 and 50 mg/kg/day) or twice daily (125 mg/kg). MICs determined in five different ways with 24- and 48-h endpoints were also compared. The overall survival rates were controls, 14%; fluconazole, 64%; and ABLC, 82%. Treatment with ABLC at 2 to 10 mg/kg increased survival compared to controls (P = <0.0001) and was also superior to fluconazole at 25 and 50 mg/kg (P = 0.006). In the fluconazole-resistant C. tropicalis model (MIC, 128 microg/ml), ABLC at 2 to 10 mg/kg was superior to fluconazole at 250 mg/kg and ABLC at 10 mg/kg was superior to all fluconazole doses (P = <0.05). Fluconazole at 250 mg/kg daily was superior to both 25 and 50 mg/kg at reducing mortality with most isolates. ABLC was superior to fluconazole (P = <0.01), and fluconazole at 250 mg/kg was superior to fluconazole at both 25 and 50 mg/kg (P = 0.02) in all models at reducing C. tropicalis counts in the kidneys. Neither drug consistently sterilized the brain or kidneys. A 48-h endpoint reading with the NCCLS susceptibility testing microtiter variation overestimates resistance to fluconazole. ABLC is an effective treatment for fluconazole-resistant C. tropicalis at all doses tested.