Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2019 Publisher: Gilead Sciences International Ltd, Granta Park, Abington, Cambridge, CB21 6GT
Pharmacotherapeutic group: Antimycotics for systemic use, antibiotics
ATC code: J02AA01
Amphotericin B is a macrocyclic, polyene antifungal antibiotic produced by Streptomyces nodosus. Amphotericin B is fungistatic or fungicidal depending on the concentration attained in body fluids and the susceptibility of the fungus. The molecule is thought to act by binding to sterols in the fungal cell membrane, with a resulting change in membrane permeability, allowing leakage of a variety of small molecules. Mammalian cell membranes also contain sterols, and it has been suggested that the damage to human cells and fungal cells caused by amphotericin B may share common mechanisms. The lipophilic moiety of amphotericin allows the molecule to be integrated into the lipid bilayer of the liposomes. Liposomes are closed, spherical vesicles formed from a variety of amphiphilic substances such as phospholipids. Phospholipids arrange themselves into membrane bilayers when exposed to aqueous solutions.
The efficacy of AmBisome has been established in a number of clinical trials for the treatment of systemic mycotic infections, as empirical therapy for fever of unknown origin in neutropenic patients and for the treatment of visceral leishmaniasis. These studies include comparative randomized studies of AmBisome versus conventional amphotericin B in confirmed Aspergillus and Candida infections where the efficacy of both medicinal products was equivalent. In both adult and paediatric febrile neutropenic patients presumed to have fungal infection, the results of a randomized, double-blind clinical trial demonstrated that AmBisome administered at 3 mg/kg/day is as effective as conventional amphotericin B. The efficacy of AmBisome in the treatment of visceral leishmaniasis has been clearly demonstrated in a large population of immunocompetent and immunocompromised patients.
The efficacy of AmBisome has been demonstrated in a prospective, randomised, multicentre study as first line treatment in immunocompromised, mainly neutropenic adults and children (> 30 days old) with proven or probable IFFIs (AmBiLoad Study).
Patients were monitored for 12 weeks. A standard-dose regimen of 3 mg/kg/day (N=107) was compared to a loading dose regimen of 10 mg/kg/day (N=94) for the first 14 days of treatment. The favourable overall response rates were 50% of subjects in the standard-dose group and 46% of the subjects in the loading-dose group in the modified intent-to-treat analysis set. Differences were not statistically significant. The median time to resolution of fever was similar in the standard-dose and loading-dose groups (6 and 5 days, respectively). Twelve weeks after the first dose of AmBisome, survival was 72% in the standard-dose group and 59% in the loading-dose group, a difference that was not statistically significant.
AmBisome (3 mg/kg/day) was as effective as Micafungin (100 mg/day [Body weight >40 kg] or 2 mg/kg/day [Body weight ≤40 kg]) as first line treatment of candidaemia and invasive candidiasis in a randomised, double-blind, multinational non-inferiority study in adults and children. AmBisome and Micafungin were administered for a median duration of 15 days. The favourable overall response was 89.5% (170/190) in the AmBisome group and 89.6% (181/202) in the Micafungin group (per protocol analysis set). The paediatric sub-study, which enrolled 98 patients of whom 57 were <2 years old, (including 19 premature infants), showed favourable overall response rates of: 88.1% (37/42) for AmBisome and 85.4% (35/41) for Micafungin (per protocol analysis set).
There are no large-scale randomised clinical trials in mucormycosis.
The working group in zygomycosis of the European confederation of medical mycology (ECMM) prospectively collected cases of patients with zygomycosis, 130 patients received liposomal amphotericin B (L-AMB) as first-line therapy, either alone (68) or in combination. In patients who received it as the only antifungal medication, the survival rate was 68%. In patients that were cured, the median duration of treatment was 55 days (range 14-169 days) and the median daily dose was 5 mg/kg (range 3-10 mg/kg), (Skiada et al; Clin Microbiol Infect 2011;17 (12):1859-67).
In a prospective pilot study of high-dose (10 mg/kg/day) liposomal amphotericin B for the initial treatment of mucormycosis, 29 patients receiving 10 mg/kg/day had a median treatment duration of 13.5 days (range 0-28 days). The primary endpoint was treatment success at week 4 or at end of treatment (if earlier) and 12 (36%) out of 33 evaluable patients responded, including 18% with complete response; the response rate increased to 45% at week 12. The survival rate was 62% at week 12 and 47% at week 24 (Lanternier et al; J Antimicrob Chemother 2015; 70(11):3116-23).
The pharmacodynamic profile of AmBisome in paediatric patients is consistent with that described in adult patients.
The pharmacokinetic profile of AmBisome (liposomal amphotericin B (L-AmB), based upon total plasma concentrations of amphotericin B, was determined in cancer patients with febrile neutropenia and bone marrow transplant patients who received 1 hour infusions of 1.0 to 7.5mg/kg/day L-AmB for 3 to 20 days. L-AmB has a significantly different pharmacokinetic profile from that reported in the literature for conventional presentations of amphotericin B, with higher amphotericin B plasma concentrations (Cmax) and increased exposure (AUC0-24) compared to conventional amphotericin B. After the first dose and last dose, the pharmacokinetic parameters of amphotericin B (mean ± standard deviation) ranged from:
| Cmax | 7.3 μg/ml (± 3.8) to 83.7 μg/ml (± 43.0) |
| T½ | 6.3 hr (± 2.0) to 10.7 hr (± 6.4) |
| AUC0-24 | 27 μg.hr/ml (±14) to 555 μg.hr/ml (± 311) |
| Clearance (CI) | 11 ml/hr/kg (± 6) to 51 ml/hr/kg (± 44) |
| Volume of distribution (Vss) | 0.10 L/kg (± 0.07) to 0.44 L/kg (±0.27) |
Minimum and maximum pharmacokinetic values do not necessarily relate to the lowest and highest doses, respectively. Following administration of liposomal amphotericin B (L-AmB) steady state was reached quickly (generally within 4 days of dosing).
Amphotericin B pharmacokinetics following the first dose of L-AmB appear non-linear such that amphotericin B concentrations are greater than proportional with increasing dose. This non-proportional dose response is believed to be due to saturation of reticuloendothelial L-AmB clearance. There was no significant drug accumulation in the plasma following repeated administration of 1 to 7.5mg/kg/day.
Volume of distribution on day 1 and at steady state suggests that there is extensive tissue distribution of amphotericin B.
After repeated administration of L-AmB, the terminal elimination half-life (t½β) of amphotericin B was approximately 7 hours. The excretion of L-AmB has not been studied. The metabolic pathways of amphotericin B and L-AmB are not known. Due to the size of the liposomes, there is no glomerular filtration and renal elimination of L-AmB, thus avoiding interaction of amphotericin B with the cells of the distal tubuli and reducing the potential for nephrotoxicity seen with conventional amphotericin B presentations.
The effect of renal impairment on the pharmacokinetics of L-AmB has not been formally studied. Data suggest that no dose adjustment is required in patients undergoing haemodialysis or filtration procedures, however, L-AmB administration should be avoided during the procedure.
Intrinsic resistance, though rare, may be primarily due to decrease in ergosterol or a change in the target lipid, leading to reduced binding of amphotericin B to the cell membrane.
EUCAST breakpoints for L-AmB have not yet been established, however, susceptibility to L-AmB may differ to that of amphotericin B deoxycholate.
Amphotericin B, the antifungal component of L-AmB, is active in vitro against many species of fungi, most strains of Histoplasma capsulatum, Coccidioides immitis, Candida spp, Blastomyces dermatidis, Rhodotorula, Cryptococcus neoformans, Sporothrix schenkii and Aspergillus fumigatus, Penicillium marneffi, and members of the mucormycetes group of moulds including Mucor mucedo, Rhizomucor and Rhizopus oryzae.
The majority of clinically important fungal species seem to be susceptible to amphotericin B, although intrinsic resistance has rarely been reported, for example, for some strains of S. schenckii, C. glabrata, C.krusei, C. tropicalis, C. lusitaniae, C. parapsilosis and Aspergillus terreus.
L-AmB has been shown to be effective in animal models of visceral leishmaniasis (caused by Leishmania infantum and Leishmania donovani).
In subchronic toxicity studies in dogs (1 month), rabbits (1 month) and rats (3 months) at doses equal to or, in some species, less than the clinical therapeutic doses of 1 to 3 mg/kg/day, the target organs for L-AmB toxicity were the liver and kidneys with thrombocytopenia also observed. All are known targets for amphotericin B toxicity.
L-AmB was found to be non-mutagenic in bacterial and mammalian systems.
Carcinogenicity studies have not been conducted with L-AmB.
No adverse effects on male or female reproductive function were noted in rats.
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