Safety Evaluation of ABELCET, an Amphotericin B Lipid Complex (ABLC): Toxicity Studies in Rats

Nonclinical Toxicological Evaluation of Occidiofungin, a Unique Glycolipopeptide Antifungal

Occidiofungin, a glycolipopeptide obtained from the liquid culture of Burkholderia contaminans MS14, has been identified as a novel fungicide. The present study was designed to initially assess the in vitro toxicity in a rat hepatoma (H4IIE) cell line and acute toxicological effects of occidiofungin using a mouse model. In vitro toxicity was observed in all variables at 5 μmol/L. B6C3F1 mice were given single and repeat doses of occidiofungin up to 20 mg/kg. Key effects were a reduction in body and organ weights. However, no significant decrease in body weight was noted at a dose of 1 mg/kg, which is comparable to the dose level of other cyclic glycopeptide antifungal agents currently approved for human use. Microscopic examination of treated mice did not identify any signs of organ-specific toxicity at the dose levels tested.

Highly active human pharmaceuticals in aquatic systems: A concept for their identification based on their mode of action

Widespread occurrence of traces of pharmaceuticals (ng/L to microg/L) has been reported in aquatic systems. However, their effects on the environment and their environmental risks remain elusive. Generally, the acute toxicity towards non-target organisms has been assessed in laboratory experiments, but chronic toxicity studies have been performed only rarely. The guideline issued by the European Medicines Agency in 2006 is aimed at estimating the potential environmental risks of human pharmaceuticals by a tiered approach. The predicted environmental concentration (PEC) of a compound is estimated in phase I, and pharmaceuticals having a PEC above or equal 10ng/L undergo phase II testing. Otherwise they are not expected to pose a risk to the environment. Because some highly active compounds (HC) such as 17-alpha-ethinylestradiol, equine estrogens, trenbolone and the progestin levonorgestrel display adverse effects at concentrations below 10ng/L the question arises, whether additional HC compounds exist, and how they can be identified for undergoing environmental risk assessment. We addressed this question by searching for HC in the literature, and by developing a concept for identification of HC. The suggested mode of action concept is based on (i) the mode of action of the pharmaceutical taking the available toxicological information into account, (ii) the degree of sequence homology between the human drug target and the potential target in aquatic organisms and (iii) the importance of pathways affected by the pharmaceutical. We evaluated the mode of action concept by comparison to existing approaches, the fish plasma model (Huggett et al., 2003) and a QSAR model, called VirtualTox Lab (www.biograf.ch). All concepts result in similar classifications of the selected pharmaceuticals. However, there are some differences not only in the model assumptions, but also in its results. Our study leads to the conclusion that the mode of action concept is most suitable for the identification of HC. A refinement can be achieved by complementing this concept by the QSAR model (VirtualTox Lab), whereas the fish plasma model seemed to be less suitable due to the necessity of environmental concentration above 10ng/L for the identification of a risk.

Amphotericin B in poly(lactic-co-glycolic acid) (PLGA) and dimercaptosuccinic acid (DMSA) nanoparticles against paracoccidioidomycosis

OBJECTIVES

The present study reports on the preparation and testing of a desoxycholate amphotericin B (D-AMB) sustained delivery system based on poly(lactic-co-glycolic acid) (PLGA) and dimercaptosuccinic acid (DMSA) polymeric blends (Nano-D-AMB) aimed at reducing the number of AMB administrations required to treat mycosis.

METHODS

BALB/c mice were infected with the yeast Paracoccidioides brasiliensis intravenously to mimic the chronic form of paracoccidioidomycosis. At 30 days post-infection, the animals were treated with Nano-D-AMB [6 mg/kg of encapsulated D-AMB, intraperitoneally (ip), interval of 72 h] or D-AMB (2 mg/kg, ip, interval of 24 h). Drug efficacy was investigated by the fungal burden recovery from tissues. Toxicity was assessed by renal and hepatic biochemical parameters, physical appearance of the animals and haematological investigation. The control groups used were non-infected and the infected mice mock treated with PBS.

RESULTS

Nano-D-AMB presented results comparable to free D-AMB, with a marked antifungal efficacy. The Nano-D-AMB-treated group presented lower loss of body weight and absence of stress sign (piloerection and hypotrichosis) observed after D-AMB treatment. No renal [blood urea nitrogen (BUN), creatinine] or hepatic (pyruvic and oxalacetic glutamic transaminases) biochemical abnormalities were found. The micronucleus assay showed no significant differences in both the micronucleus frequency and percentage of polychromatic erythrocytes for Nano-D-AMB, indicating the absence of genotoxicity and cytotoxic effects.

CONCLUSIONS

The D-AMB-coated PLGA-DMSA nanoparticle showed antifungal efficacy, fewer undesirable effects and a favourable extended dosing interval. Nano-D-AMB comprises an AMB formulation able to lessen the number of drug administrations. Further studies would elucidate whether Nano-D-AMB would be useful to treat systemic fungal infections such as paracoccidioidomycosis, candidiasis, aspergillosis and cryptococcosis.

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.

Comparative immunotoxicity evaluation of amphotericin B and ABELCET, an amphotericin B lipid complex (ABLC)

ABELCET, an amphotericin B lipid complex formulation (ABLC) and an aqueous, non-lipid-containing formulation with sodium deoxycholate (AmBd), were evaluated for their potential to induce immunotoxicity in B6C3F1 female mice. ABLC was administered intravenously at doses of 1, 3, and 10 mg/kg daily for 28 days, while AmBd at 1 mg/kg was administered by the same route and duration. The effect of ABLC and AmBd on clinical signs, body weight, and spleen weight was determined. Peritoneal macrophage function was measured by phagocytosis of 51Cr-labeled chicken red blood cells and generation of hydrogen peroxide during respiratory burst. The ability of natural killer cells to lyse radiolabeled tumor target cells was evaluated in a short-term chromium-release assay. The ability of splenic T and B cells to undergo blastogenesis and of splenic T cells to recognize alloantigens present on foreign cells was assessed in a splenic lymphocyte assay and the ability of mice to generate antibody-forming cells following immunization with sheep red blood cells was measured. Neither ABLC nor AmBd affected the metabolic or functional activity of murine phagocytic cells. These agents also did not cause any biologically significant or dose-related changes in B- or T-cell responses to mitogens, T-cell responses to allogeneic cells in the mixed lymphocyte culture assay, or natural killer cell function. The ability to generate a primary antibody response to a T cell-dependent antigen was also unimpaired. Based on the results of this study, it was concluded that neither ABLC at dose up to 10 mg/kg nor AmBd at dose up to 1.0 mg/kg produce biologically significant immunologic changes in B6C3F1 mice.