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Contains fulltext : 220654.pdf (Publisher’s version ) (Open Access) In this prospective study, we examined the pharmacokinetics of 1 and 2 mg/kg liposomal amphotericin B in 16 morbidly obese individuals (104-177 kg). Body size had no effect on clearance. We recommend a fixed dose in patients ≥100 kg (ie, 300 or 500 mg rather than the current dose of 3 and 5 mg/kg, respectively). Clinical Trials Registration NCT02320604.

Contains fulltext : 205145.pdf (Publisher’s version ) (Open Access) Since its introduction in the 1990s, liposomal amphotericin B (LAmB) continues to be an important agent for the treatment of invasive fungal diseases caused by a wide variety of yeasts and molds. This liposomal formulation was developed to improve the tolerability of intravenous amphotericin B, while optimizing its clinical efficacy. Since then, numerous clinical studies have been conducted, collecting a comprehensive body of evidence on its efficacy, safety, and tolerability in the preclinical and clinical setting. Nevertheless, insights into the pharmacokinetics and pharmacodynamics of LAmB continue to evolve and can be utilized to develop strategies that optimize efficacy while maintaining the compound's safety. In this article, we review the clinical pharmacokinetics, pharmacodynamics, safety, and efficacy of LAmB in a wide variety of patient populations and in different indications, and provide an assessment of areas with a need for further clinical research.

Contains fulltext : 205184.pdf (Publisher’s version ) (Open Access) The improved safety profile and antifungal efficacy of liposomal amphotericin B (LAmB) compared to conventional amphotericin B deoxycholate (DAmB) is due to several factors including, its chemical composition, rigorous manufacturing standards, and ability to target and transit through the fungal cell wall. Numerous preclinical studies have shown that LAmB administered intravenously distributes to tissues frequently infected by fungi at levels above the minimum inhibitory concentration (MIC) for many fungi. These concentrations can be maintained from one day to a few weeks, depending upon the tissue. Tissue accumulation is dose-dependent with drug clearance occurring most rapidly from the brain and slowest from the liver and spleen. LAmB localizes in lung epithelial lining fluid, within liver and splenic macrophages and in kidney distal tubules. LAmB has been used successfully in therapeutic and prophylactic animal models to treat many different fungal pathogens, significantly increasing survival and reducing tissue fungal burden.

By selecting a unique combination of lipids and amphotericin B, the liposome composition for AmBisome® (L-AmBis) has been optimized resulting in a formulation that is minimally toxic, targets to fungal cell walls, and distributes into and remains for days to weeks in various host tissues at drug levels above the MIC for many fungi. Procedures have been standardized to ensure that large scale production of the drug retains the drug's low toxicity profile, favorable pharmacokinetics and antifungal efficacy. Tissue accumulation and clearance with single or multiple intravenous administration is similar in uninfected and infected animal species, with tissue accumulation being dose-dependent and the liver and spleen retaining the most drug. The efficacy in animals appears to be correlated with drug tissue levels although the amount needed in a given organ varies depending upon the type of infection. The long-term tissue retention of bioactive L-AmBis in different organs suggests that for some indications, prophylactic and intermittent drug dosing would be efficacious reducing the cost and possible toxic side-effects. In addition, preliminary preclinical studies using non-intravenous routes of delivery, such as aerosolized L-AmBis, catheter lock therapy, and intravitreal administration, suggest that alternative routes could possibly provide additional therapeutic applications for this antifungal drug.

Because of the reduced toxicity associated with liposomal amphotericin B preparations, different amphotericin B liposome products have been made. In the present study, we compared the amphotericin B liposomal formulations, AmBisome(®) (AmBi) and Lambin(®) (Lbn), in uninfected and Aspergillus fumigatus infected mice, using several in vitro and in vivo toxicity and efficacy assays. The results showed that the formulations were significantly different, with Lbn 1.6-fold larger than AmBi. Lbn was also more toxic than AmBi based on the RBC potassium release assay and intravenous dosing in uninfected mice given a single 50 mg/kg dose (80% mortality for Lbn vs. 0% for AmBi). Renal tubular changes after intravenous daily dosing for 14 days were seen in uninfected mice given 5 mg/kg Lbn but not with AmBi. Survival following A. fumigatus challenge was 30% for 10 mg/kg Lbn and 60% for 10 mg/kg AmBi. When the BAL and lungs were collected 24 h after the second treatment, AmBi at 10 or 15 mg/kg or 15 mg/kg Lbn lowered the BAL fungal burden significantly vs. the controls (P ≤ 0.05), while there was no difference in lung fungal burden amongst the groups. In contrast, lung histopathology at this same early timepoint showed that AmBi was associated with markedly fewer fungal elements and less lung tissue damage than Lbn. In conclusion, given the differences in size, toxicity, and efficacy, AmBi and Lbn were not physically or functionally comparable, and these differences underscore the need for adequate testing when comparing amphotericin B liposome formulations.

Background Immunocompromised patients are very susceptible to pulmonary aspergillosis causing 50% mortality with present treatments, indicating a need for improved therapy. To address this, we standardized a nebulization method for effectively delivering liposomal amphotericin B (AmBisome®, AmBi) into lungs of Aspergillus fumigatus-infected mice. Methods AmBi particle characterization was done with a Cascade particle impactor and a Schuco S5000 nebulizer containing 1.33 mg/mL AmBi. For in vivo studies, AmBi was nebulized (neb) into a 12 compartment chamber (one mouse/compartment), following immunosuppression with 28 mg/kg triamcinolone IP (d-3, -1, +1). Mice were challenged d0 with 9 x 106A. fumigatus (ATCC#13073) and 4 hours post-challenge, divided into 5 groups (n = 12/gp): 5 days of 20 min/day neb AmBi (Gp1), 5 days of 10 min/day neb AmBi (Gp2), 20 min/day neb AmBi days 0, 1, 3, 5, 7 (Gp 3), 5 days of intravenous(IV) AmBi 7.5 mg/kg/day (Gp4) and IV PBS (Gp5). Seven mice/gp were monitored for survival to d21 and lungs, livers, kidneys, spleens (5 mice/gp) analyzed for mean amphotericin B µg/g and CFU/g. Results 87% of neb AmBi particles were between 0.43 mm to 3.3 mm allowing for drug penetration into 1°, 2° and terminal bronchi, bronchioles, and alveoli. This resulted in very good protection, with 20 min daily neb treatments (Gp1) giving 100% survival and 10 min daily neb treatments producing 71% survival (Gp2). There were no survivors in the PBS gp (P < 0.02 vs. Gp1 and Gp2). Every other day neb AmBi or daily IV AmBi was less effective (43% survival). In addition, neb AmBi for 20 min (Gp1) yielded significantly lower fungal burden in lungs vs. all other AmBi treatments (P < 0.02). While drug was detected in lungs of mice given 20 min of neb AmBi (2.6 µg/g), there was no drug detected in livers, kidneys or spleens of any mice given neb AmBi. In comparison, with IV AmBi, drug was detected in the lungs (7 µg/g), livers (204 µg/g), kidneys (38 µg/g), and spleens (114 µg/g). Conclusion Daily AmBi nebulization was an effective and potentially less nephrotoxic treatment for murine pulmonary aspergillosis since it achieved significantly lower tissue fungal burden and much better survival vs. daily IV AmBi, without delivering drug to the kidneys. Disclosures All authors: No reported disclosures.

Given the recent increase in aspergillosis caused by species other than Aspergillus fumigatus , micafungin, caspofungin, and liposomal amphotericin B (L-AmBi) were investigated as monotherapy or combination therapy for murine systemic or pulmonary Aspergillus flavus infection. Treatment for 3 or 6 days was begun at 24 h (intravenous [i.v.], 2.8 × 10 4 conidia) or 2 h (intranasal, 4.1 × 10 6 to 6.75 × 10 6 conidia) postchallenge as follows: 5 or 10 mg/kg L-AmBi, 10 mg/kg caspofungin, 15 mg/kg micafungin, L-AmBi plus echinocandin, L-AmBi on days 1 to 3 and echinocandin on days 4 to 6, or echinocandin on days 1 to 3 and L-AmBi on days 4 to 6. Mice were monitored for survival, fungal burden, serum or tissue cytokines, and lung histopathology. In the systemic infection, micafungin or caspofungin was more effective than L-AmBi in prolonging survival ( P < 0.05), and L-AmBi was associated with significantly elevated serum levels of interleukin-6 (IL-6), macrophage inflammatory protein 1α (MIP-1α), and IL-12 ( P < 0.05). In contrast, L-AmBi was significantly more effective than the echinocandins in reducing fungal growth in most tissues ( P < 0.05). Concomitant therapies produced significantly enhanced survival, reduction in fungal burden, and low levels of proinflammatory cytokines, while antagonism was seen with some sequential regimens. In comparison, in the pulmonary infection, L-AmBi was significantly better ( P < 0.05) than caspofungin or the combination of L-AmBi and caspofungin in prolonging survival and reducing lung fungal burden. Caspofungin stimulated high lung levels of IL-1α, tumor necrosis factor alpha (TNF-α), and IL-6, with extensive tissue damage. In summary, systemic A flavus infection was treated effectively with L-AmBi plus micafungin or caspofungin provided that the drugs were administered concomitantly and not sequentially, while pulmonary A. flavus infection responded well to L-AmBi but not to caspofungin.

Amphotericin B formulations were compared in preclinical models by using intraperitoneal (ip) and intravenous (iv) delivery of amphotericin B deoxycholate (DAMB) or liposomal amphotericin B. We examined the effects on drug tissue penetration and retention resulting from different routes of drug administration. Mice were treated with equivalent total doses of AmBisome (AmBi) or DAMB (i.e.,15 mg/kg) given ip (3 mg/kg/day for 5 days) or iv (3 mg/kg/day AmBi for 5 days or 1 mg/kg/day DAMB for 15 days), with tissues collected 24 h post-treatment. For drug retention studies, mice were given iv or ip total doses of 30 mg/kg AmBi (10 mg/kg/day 3 x /week) or 60 mg/kg AmBi (20 mg/kg/day 3 x /week) with tissue collection 24 h or 7 days post-treatment. Blood samples were collected at 0.5 h, 2 h, 8 h, 12 h and 24 h after ip or iv drug dosing. A Paecilomyces variottii bioassay was used to determine drug concentrations. AmBi and DAMB were detected in the kidneys following iv, but not ip dosing. Significantly more DAMB than AmBi was detected in the lungs with ip dosing (P = 0.008), and more AmBi than DAMB (P = 0.056) was present with iv dosing. Unlike the lungs, the spleen and liver retained the AmBi for up to one week post-treatment regardless of the route of drug administration. Thus, there are significant differences in AmBi and DAMB tissue distribution depending upon the drug route and these differences could effect how the drugs perform in fungal infection models.

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 (K 50 values) to assess toxicity. The 50% lethal dose (LD 50 ) 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 × 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 μg/ml) than for AmBisome (20 μg/ml), and the LD 50 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.

International audience; Given the clinical success of commercial amphotericin B lipid products, investigators have begun making generic formulations of liposomal amphotericin B. Generic medicines are an attractive approach to help decrease the cost and accessibility to healthcare, provided that appropriate studies are performed to ensure bioequivalence with the parent product. This is of particular concern for liposomal drugs such as amphotericin B where liposomes are used as a carrier system to reduce the toxicity of the active agent. A favorable therapeutic profile for this form of the drug has to include the proper chemical composition along with strictly controlled manufacturing processes. Studies have shown that a comparison of liposomal amphotericin B products with different or the same chemical compositions, using different methods of production, will vary in size, and have significantly dissimilar in vitro and in vivo toxicities along with reduced efficacy. These results underscore the importance of establishing appropriate bioequivalence testing for liposome products to ensure uniformity of their therapeutic index

During the past decade, liposomal amphotericin B has been used with increasing frequency to treat visceral leishmaniasis (VL). The World Health Organization convened a workshop to review current knowledge and to develop guidelines for liposomal amphotericin B use for VL. In Europe, liposomal amphotericin B is widely used to treat VL. In Africa and Asia, the VL disease burden is high and drug access is poor; liposomal amphotericin B is available only through preferential pricing for nonprofit groups in East Africa. Clinical trials and experience demonstrate high efficacy and low toxicity for liposomal amphotericin B (total dose, 20 mg/kg) in immunocompetent patients with VL. Combination trials in areas with antileishmanial drug resistance, and treatment and secondary prophylaxis trials in VL-human immunodeficiency virus-coinfected patients, are important to safeguard the current armamentarium and to optimize regimens. The public health community should work to broaden access to preferential liposomal amphotericin B pricing by public sector VL treatment programs.

While Candida albicans remains the most common Candida isolate, Candida glabrata accounts for approximately 15 to 20% of all Candida infections in the United States. In this study we used immunosuppressed mice infected with C. glabrata to investigate the efficacy of liposomal amphotericin B alone or in combination with the echinocandin caspofungin or micafungin. For monotherapy, mice were given six daily doses of liposomal amphotericin B (3 to 20 mg/kg of body weight), caspofungin (1 to 5 mg/kg), or micafungin (2.5 to 10 mg/kg). With concomitant therapy, mice received liposomal amphotericin B (7.5 mg/kg) in addition to caspofungin (2.5 mg/kg) or micafungin (2.5 mg/kg) for 6 days. For sequential therapy, liposomal amphotericin B was administered on days 1 to 3 and caspofungin or micafungin was given on days 4 to 6; conversely, caspofungin or micafungin was administered on days 1 to 3 and liposomal amphotericin B was given on days 4 to 6. Efficacy was based on the number of CFU per gram of kidney 21 days postchallenge. Monotherapy with liposomal amphotericin B (7.5 to 20 mg/kg) was significantly more effective than no drug treatment (control group) ( P < 0.05) and demonstrated a dose-dependent response, with 20 mg/kg lowering the CFU/g from 6.3 to 4.2 (significantly different from the value for the control group [ P < 0.001]). Monotherapy with all echinocandin doses lowered the CFU/g from 6.0 to 6.4 to 2.7 to 3.3 (significantly different from the value for the control group [ P < 0.001]) with no dose-dependent response. Complete clearance of infection could be achieved only when liposomal amphotericin B was given either concomitantly with caspofungin or micafungin or if liposomal amphotericin B was given sequentially with caspofungin. In conclusion, the combination of liposomal amphotericin B with an echinocandin markedly improved the therapeutic outcome in murine C. glabrata systemic infection.

This study was done to determine whether high dose AmBisome (4-20 mg/kg), given intermittently, could reduce the frequency of dosing needed to treat murine systemic candidiasis when compared with conventional daily treatment.Mice were immunosuppressed with cyclophosphamide every 3 days, beginning day -3 before challenge with log(10) 5.0 cfu Candida albicans. Treatment was begun 48-72 h post-challenge with daily or intermittent dose regimens of AmBisome, followed by determination of kidney cfu for up to 1 month post-treatment.A single AmBisome dose of 4 mg/kg was as effective as four daily, 1 mg/kg treatments. A total of 8 mg/kg, given as 4 mg/kg on days 2 and 4, or as 5 mg/kg on day 2 followed by 1 mg/kg on days 3, 4, and 5, also produced comparable efficacy. While 20 mg/kg given day 2, 4 and 6 post-challenge as a 1 week loading dose, followed by one 10 mg/kg treatment on day 13, decreased the fungal burden by up to 5 logs compared with controls (log(10) 2.3 cfu/g and log(10) 7.5 cfu/g, respectively), 20 mg/kg given Monday, Wednesday and Friday for 5 weeks, reduced the fungal burden to undetectable levels (i.e. log(10) 1.0 cfu).Significant reduction or clearance of kidney cfu, following intermittent, high dose AmBisome treatment, indicated that non-daily dosing regimens could be successfully used instead of conventional daily dosing to treat established C. albicans infection in immunosuppressed mice.

Amphotericin B is the treatment of choice for life-threatening systemic fungal infections such as candidosis and aspergillosis. To improve this drug's efficacy and reduce its acute and chronic toxicities, several lipid formulations of the drug have been developed, including AmBisome, a liposomal formulation of amphotericin B. The liposome is composed of high transition temperature phospholipids and cholesterol, designed to incorporate amphotericin B securely into the liposomal bilayer. AmBisome can bind to fungal cell walls, where the liposome is disrupted. The amphotericin B, after being released from the liposomes, is thought to transfer through the cell wall and bind to ergosterol in the fungal cell membrane. This mechanism of action of AmBisome results in its potent in vitro fungicidal activity while the integrity of the liposome is maintained in the presence of mammalian cells, for which it has minimal toxicity. In animal models, AmBisome is effective in treating both intracellular (leishmaniasis and histoplasmosis) and extracellular (candidosis and aspergillosis) systemic infections. Because of its low toxicity at the organ level, intravenous AmBisome can be safely delivered at markedly high doses of amphotericin B (1–30 mg/kg) for the treatment of systemic fungal infections. AmBisome has a circulating half-life of 5–24 h in animals, and in animal models appears to localize at sites of infection in the brain (cryptococcosis, aspergillosis, coccidioidomycosis), lungs (blastomycosis, paracoccidioidomycosis, aspergillosis) and kidneys (candidosis), delivering amphotericin B that remains bioavailable in tissues for several weeks following treatment.

AmBisome is a lyophilized formulation of amphotericin B incorporated into small unilamellar liposomes composed of hydrogenated soy phosphatidylcholine, distearoyl phosphatidylglycerol, and cholesterol. In aqueous solution AmBisome is quite stable; less than 5% of the drug dissociates from the Iiposomes during a 72 hour incubation period in human plasma. This stability to loss of drug is a key factor, accounting for the ability of AmBisome to markedly reduce the well known acute and chronic toxicities associated with the administration of amphotericin B. Numerous animal and clinical studies have documented the therapeutic efficacy of AmBisome for a wide range of fungal infections. Mechanism of action studies indicate that AmBisome liposomes specifically bind to the fungal cell surface, damage the cell membrane, and kill the fungus. In some cases, AmBisome had a slightly lower potency than amphotericin B itself, but much higher doses of AmBisome could be administered safely resulting in an improved therapeutic profile.

Monotherapy and combination therapy were compared using optimal doses of liposomal amphotericin B, micafungin, or caspofungin in Aspergillus fumigatus pulmonary and disseminated infections. Mice were challenged intravenously (2.8 × 10 4 to 5.7 × 10 4 conidia) or intranasally (5.8 × 10 7 conidia) with A. fumigatus . Drugs (5, 10, or 15 mg/kg of body weight) were given for 3 or 6 days as single, concomitant, or sequential therapy (i.e., days 1 to 3 and then days 4 to 6). Mice were monitored for survival, and tissues were assayed for fungal burden and drug concentrations. Treatments starting 24 h postchallenge significantly prolonged survival in disseminated aspergillosis ( P < 0.002), but only liposomal amphotericin B treatments or treatments beginning with liposomal amphotericin B increased survival to 100% in the pulmonary aspergillosis model. Fungi in kidneys and spleens (disseminated) and lungs (pulmonary) were significantly decreased ( P ≤ 0.04) by liposomal amphotericin B, liposomal amphotericin B plus echinocandin, or liposomal amphotericin B prior to echinocandin. In the disseminated infection, liposomal amphotericin B and micafungin (10 or 15 mg/kg) had similar kidney drug levels, while in the spleen, 5 and 15 mg/kg liposomal amphotericin B gave higher drug levels than micafungin ( P < 0.02). In the pulmonary infection, drug levels in lungs and spleen with 5-mg/kg dosing were significantly higher with liposomal amphotericin B than with caspofungin ( P ≤ 0.002). In summary, treatment of A. fumigatus infections with liposomal amphotericin B plus echinocandin or liposomal amphotericin B prior to echinocandin was as effective as liposomal amphotericin B alone, and a greater decrease in the fungal burden with liposomal amphotericin B supports using liposomal amphotericin B prior to echinocandin.

Objectives We hypothesized that effective prophylactic treatment of fungal infections would require adequate drug penetration and retention at potential infection sites. Using a mouse model, we examined liposomal amphotericin B (L-AmB) biodistribution, cell localization and retention in kidneys, lungs, liver and spleen to evaluate effective dosing regimens for prophylaxis of Candida glabrata and Candida albicans infections. Methods Following treatment of mice with cumulative doses of L-AmB (60-225 mg/kg), a bioassay was done to determine tissue drug concentrations 12 h to 6 weeks post-treatment. Immunohistochemical staining with anti-amphotericin B antibodies was used for cellular drug localization. Mice were treated prophylactically with 15-90 mg/kg L-AmB and challenged intravenously 1-7 days later with C. glabrata or they were given a total of 60 mg/kg as daily or intermittent dosing followed by intravenous challenge with C. albicans 3 or 6 weeks later. Results On the basis of microg/g tissue, the relative amount of drug was in the order spleen > liver > kidneys > lungs. Amphotericin B levels were maintained above the MIC for many fungi for 1 week in lungs and for as long as 6 weeks in kidneys and spleen. Drug localized in kidney tubular epithelial cells and in macrophages of liver and spleen. In prophylactic models, fungal burden was reduced by several 1000-fold or was undetectable within target tissues (kidneys, spleen). Conclusions These observations underscore the importance of including drug tissue levels to obtain a better understanding of L-AmB efficacy. The sustained concentrations of bioactive AmB in many tissues provide a further rationale for investigating L-AmB prophylactic regimens.

Objectives: Fusarium solani infections are notoriously difficult to treat. We compared the efficacy of polyenes and an echinocandin in treating murine fusariosis to identify the optimal therapeutic regimen. Methods: Neutropenic mice infected intravenously with F. solani were treated with amphotericin B (AmB), liposomal AmB (LAmB), amphotericin B lipid complex (ABLC), caspofungin acetate or a combination of LAmB and caspofungin. Treatment was initiated prior to infection (prophylactic therapy), 24 h post-infection (delayed therapy) or 2 days before infection and continued for 1 day after (continuous therapy). Results: Prophylaxis only with LAmB significantly reduced brain or kidney fungal burden compared with placebo. No prophylactic treatment improved survival. LAmB levels in the kidneys were higher than ABLC or AmB levels, which were often undetectable. In the delayed therapy model, neither polyenes nor caspofungin improved survival. In the continuous therapy model, LAmB or LAmB plus caspofungin did not improve survival even though they did decrease fungal burden. In contrast, continuous caspofungin at 1 but not 5 mg/kg/day improved survival, but did not decrease fungal burden. Kidney inflammation and tissue necrosis were markedly decreased in mice treated with caspofungin compared with other treatments. Conclusions: These studies demonstrate a dissociation between survival and tissue fungal burden during murine fusariosis. Although prophylactic LAmB may be useful at reducing tissue fungal burden, polyenes had limited survival benefit for active fusariosis. Caspofungin at 1 but not 5 mg/kg/day mediated surprising improvements in survival during active fusariosis, despite lack of reduction in fungal burden. Further studies are warranted.

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 μg/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.

During the past decade, liposomal amphotericin B has been used with increasing frequency to treat visceral leishmaniasis (VL). The World Health Organization convened a workshop to review current knowledge and to develop guidelines for liposomal amphotericin B use for VL. In Europe, liposomal amphotericin B is widely used to treat VL. In Africa and Asia, the VL disease burden is high and drug access is poor; liposomal amphotericin B is available only through preferential pricing for nonprofit groups in East Africa. Clinical trials and experience demonstrate high efficacy and low toxicity for liposomal amphotericin B (total dose, 20 mg/kg) in immunocompetent patients with VL. Combination trials in areas with antileishmanial drug resistance, and treatment and secondary prophylaxis trials in VL-human immunodeficiency virus-coinfected patients, are important to safeguard the current armamentarium and to optimize regimens. The public health community should work to broaden access to preferential liposomal amphotericin B pricing by public sector VL treatment programs.

Amphotericin B reformulated into the liposomal formulation known as AmBisome (amphotericin B, hydrogenated soy phosphatidylcholine, cholesterol and dimyristoyl phosphatidylglycerol) can be safely administered at dosages 15 times higher than the conventional drug with the same broad spectrum of activity. Increased doses demonstrate non-linear clearance with saturation of the reticuloendothelial system (RES) and redistribution of the drug into non-RES tissues. The efficacy of this liposomal amphotericin B formulation appears to be related both to improved tissue penetration in the lungs, brain, kidneys, liver and spleen along with sustained bioactivity of therapeutic drug levels in these target tissues.

AmBisome is a liposomal formulation of amphotericin B that has broad-spectrum antifungal activity and greatly reduced toxicity compared to the parent drug. In this study, amphotericin B deoxycholate (Fungizone) (1 mg/kg) and AmBisome (1 to 20 mg/kg) were tested as single-dose prophylactic agents in both immunocompetent and immunosuppressed C57BL/6 mice challenged with either Candida albicans or Histoplasma capsulatum . Prophylactic efficacy was based on survival and fungal burden in the target organ (kidneys or spleen). At 9 to 10 days after histoplasma challenge, 80 to 90% of both immunocompetent and immunosuppressed mice in the control and Fungizone groups had died. All AmBisome-treated mice survived, although in the AmBisome groups given 1 mg/kg, the mice became moribund by day 10 to 12. No spleen CFU were detected in the histoplasma-challenged mice given 10 or 20 mg of AmBisome per kg. By 23 to 24 days after histoplasma challenge, fungal growth and/or death had occurred in all immunosuppressed mice except for four mice receiving 20 mg of AmBisome per kg. There were still no detectable fungi in the spleens of immunocompetent mice given 10 or 20 mg of AmBisome per kg. In the C. albicans experiment at 7 days postchallenge, all animals in both untreated and treated groups were alive with culture-positive kidneys. The kidney fungal burdens in AmBisome groups given 5 to 20 mg/kg were at least 1 log unit lower than those in the Fungizone group and significantly lower than those in the untreated control group ( P < 0.05). There was a trend toward decreasing fungal growth in the kidneys as the dose of AmBisome was increased. In conclusion, these results show that a single high dose of AmBisome (5 to 20 mg/kg) had prophylactic efficacy in immunocompetent and immunosuppressed murine H. capsulatum and C. albicans models.

AmBisome® is a newly commercialized formulation of amphotericin B incorporated into small unilamellar liposomes composed of cohesive bilayer forming lipids (see chapter 1). An important feature of this formulation is that the amphotericin B is stably incorporated into the liposome bilayer.1 In recent years, this and other lipid formulations have been devised to improve the utility of Fungizone, a micellar formulation of amphotericin B which rapidly disassociates upon iv administration. While the standard formulation is proven clinically, it is limited by severe renal toxicity, and many life-threatening fungal infections cannot successfully be treated.2,3 For the purposes of this chapter, Fungizone is considered “free” amphotericin B (ampB) administration.

This investigation examined the therapeutic efficacy of AmBisome, a unilamellar (55-75 nm) liposome amphotericin B preparation with a murine LD50 by the intravenous route of greater than 175 mg/kg amphotericin B. Both fungal burden and survival were used to evaluate the drug's efficacy against murine candidosis and cryptococcosis. Single and multiple dose intravenous treatment with AmBisome (2.5, 5.0 and 10.0 mg/kg) reduced the colony forming units/mg kidney in candida-infected mice by 99% and improved survival by at least 40% relative to untreated control mice. Repeated intravenous dosing of candida-infected mice with equivalent amounts (0.75 mg/kg) of conventional amphotericin B (Fungizone) or AmBisome showed comparable reduction of yeasts in the kidneys. When mice were infected systemically with Cryptococcus neoformans, all but one of the 30 mice given AmBisome (5.0, 7.5 or 10.0 mg/kg) survived until the experiment was terminated 35 days after infection. Liver and spleen cultures from AmBisome-treated mice were negative for fungal growth. All the mice given conventional amphotericin B intraperitoneally at 4.5 mg/kg survived and cleared the infection from the livers although some of the mice had infected spleens. The percentage of cultured brains free of cryptococcus was 89% following treatment with 10.0 mg/kg AmBisome, and 80% with 4.5 mg/kg conventional drug. These preclinical studies of systemic candidosis and cryptococcosis demonstrate comparable efficacy of AmBisome and conventional amphotericin B at low doses and improved efficacy with AmBisome at doses higher than can be safely administered of the conventional drug.

AmBisome is a lyophilized preparation of liposomal amphotericin B. The acute intravenous toxicity of AmBisome was evaluated in mice and rats, and the LD50S were found to be greater than 175 and 50 mg/kg, respectively. The corresponding LD50S for conventional amphotericin B were approximately 2.3 and 1.6 mg/kg for mice and rats, respectively. The multiple dose toxicity test confirmed that AmBisome was well tolerated by both species. There were no deaths observed among mice receiving 25 or 50 mg/kg AmBisome for 14 days, and only two deaths among mice receiving 75 mg/kg AmBisome. One rat died in the group receiving 25 mg/kg AmBisome for 30 days. However, five of ten and nine of ten rats died in the groups treated with 50 and 75 mg/kg AmBisome, respectively. Hepatotoxicity was evident by elevation in serum liver enzyme levels for these groups. Initial pharmacokinetic evaluations demonstrated that peak plasma concentrations of 87 and 118 mg/kg, respectively, were attained in mice and rats after injection with 5 mg/kg AmBisome. Terminal plasma half-lives of 3.36 and 7.56 h were calculated for mice and rats, respectively. Tissue accumulations of amphotericin B resulting from multiple dose intravenous administration of either conventional amphotericin B or AmBisome were determined. At equivalent doses of 1 mg/kg, AmBisome treatment resulted in higher liver and spleen uptake of drug, but lower kidney and lung uptake than amphotericin B. At 5 mg/kg, AmBisome treatment resulted in concentrations of drug in the kidney and lungs that were comparable to corresponding tissue levels observed in the group treated with 1 mg/kg conventional amphotericin B.(ABSTRACT TRUNCATED AT 250 WORDS)