Safety and efficacy of multilamellar liposomal nystatin against disseminated candidiasis in persistently neutropenic rabbits

Assessing nystatin cream treatment efficacy against Leishmania (L.) amazonensis infection in BALB/c model

The current scenario for cutaneous leishmaniasis treatment includes the use of first and second-choice drugs, both therapeutic strategies presenting several adverse effects and being related to an increment of treatment-refractory parasite strains. These facts encourage the search for new treatment approaches, including repositioning drugs, such as nystatin. Although some in vitro assays show that this polyene macrolide compound has leishmanicidal activity, no in vivo evidence for a similar activity has been shown so far for the commercial nystatin cream formulation (25,000 IU/g). This work assessed the effects of nystatin cream administered on mice in an amount to completely cover the paw surface of BALB/c mice infected with L. (L.) amazonensis once a day, until a total of up to 20 doses. The data presented herein points to unequivocal evidence that this formulation is related to a statistically significant reduction of swelling/edema in mice paws when compared to animal groups not submitted to this treatment regimen after the fourth week of infection: lesion sizes at the sixth (p = 0.0159), seventh (p = 0.0079) and eighth (p = 0.0079) week. Furthermore, infection reduction relates to a decrease in parasite load in the footpad (∼48%) and in draining lymph nodes (∼68%) at 8th weeks post-infection. This is the first report of the effectiveness of nystatin cream used as a topical treatment in BALB/c model for cutaneous leishmaniasis.

Efficacy and Pharmacokinetics of Fosmanogepix (APX001) in the Treatment of Candida Endophthalmitis and Hematogenous Meningoencephalitis in Nonneutropenic Rabbits

Candida endophthalmitis is a serious sight-threatening complication of candidemia that may occur before or during antifungal therapy. Hematogenous Candida meningoencephalitis (HCME) is also a serious manifestation of disseminated candidiasis in premature infants, immunosuppressed children, and immunocompromised adults. We evaluated the antifungal efficacy and pharmacokinetics of the prodrug fosmanogepix (APX001) in a rabbit model of endophthalmitis/HCME. Manogepix (APX001A), the active moiety of prodrug fosmanogepix, inhibits the fungal enzyme Gwt1 and is highly active in vitro and in vivo against Candida spp., Aspergillus spp., and other fungal pathogens. Plasma pharmacokinetics of manogepix after oral administration of fosmanogepix on day 6 at 25, 50, and 100 mg/kg resulted in maximum concentration of drug in plasma (C _max) of 3.96 ± 0.41, 4.14  ± 1.1, and 11.5 ± 1.1 μg/ml, respectively, and area under the concentration-time curve from 0 to 12 h (AUC_0-12) of 15.8 ± 3.1, 30.8 ± 5.0, 95.9 ± 14 μg·h/ml, respectively. Manogepix penetrated the aqueous humor, vitreous, and choroid with liquid-to-plasma ratios ranging from 0.19 to 0.52, 0.09 to 0.12, and 0.02 to 0.04, respectively. These concentrations correlated with a significant decrease in Candida albicans burden in vitreous (>10¹ to 10³ log CFU/g) and choroid (>10¹ to 10³ log CFU/g) (P ≤ 0.05 and P ≤ 0.001, respectively). The aqueous humor had no detectable C. albicans in treatment and control groups. The tissue/plasma concentration ratios of manogepix in meninges, cerebrum, cerebellum, and spinal cord were approximately 1:1, which correlated with a >10² to 10⁴ decline of C. albicans in tissue versus control (P ≤ 0.05). Serum and cerebrospinal fluid (CSF) (1→3)-β-d-glucan levels demonstrated significant declines in response to fosmanogepix treatment. These findings provide an experimental foundation for fosmanogepix in treatment of Candida endophthalmitis and HCME and derisk the clinical trials of candidemia and invasive candidiasis.

Pharmacokinetics, tissue distribution and immunomodulatory effect of intralipid formulation of nystatin in mice

OBJECTIVES

We developed a novel lipid formulation of nystatin suitable for parenteral administration, nystatin-intralipid (NYT-IL), with antifungal activity and reduced toxicity in mice. We investigated the pharmacokinetics, tissue distribution and immunomodulatory effect of NYT-IL in mice.

METHODS

Nystatin levels in serum and organs were determined using HPLC after NYT-IL or nystatin administration in mice. The levels of the pro-inflammatory cytokines tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) and the anti-inflammatory cytokine interleukin 10 (IL-10) produced by splenocytes from mice injected with NYT-IL or nystatin were evaluated by an ELISA assay.

RESULTS

Injection of NYT-IL resulted in similar levels and similar kinetics of nystatin in serum, higher concentrations in the liver and lower concentrations in the kidneys, in comparison with nystatin injection. Injection of mice with NYT-IL yielded higher levels of IL-10 than that of nystatin, whereas the levels of TNF-α and IFN-γ induced by NYT-IL were lower than those elicited by nystatin.

CONCLUSIONS

Since polyene treatment is associated with nephrotoxicity, lower levels of nystatin in the kidneys following NYT-IL injection suggest the possibility of reduced toxicity. As the acute infusion-related adverse effects associated with polyene treatment are considered to be induced by pro-inflammatory cytokines, a higher level of anti-inflammatory and lower levels of pro-inflammatory cytokines elicited by NYT-IL administration suggest the possibility of amelioration of such effects. In summary, the altered pharmacokinetics, tissue distribution and immune response due to the use of this intralipid formulation of nystatin merit further research towards the development of a therapeutic agent against invasive mycoses.

Nystatin induces secretion of interleukin (IL)-1beta, IL-8, and tumor necrosis factor alpha by a toll-like receptor-dependent mechanism

Nystatin is an antifungal compound with potent proinflammatory properties. Herein, we demonstrate that nystatin induces interleukin (IL)-1beta, IL-8, and tumor necrosis factor alpha secretion through its activation of toll-like receptor 1 (TLR1) and TLR2. Hence, a TLR-dependent mechanism could serve as the molecular basis for the proinflammatory properties of nystatin.

New agents for the treatment of systemic fungal infections – current status

Systemic antifungal chemotherapy is enjoying its most dynamic era. More antifungal agents are under development than ever before, including agents in entirely new classes. Major goals of current investigations are to identify compounds with a wide spectrum of activity, minimal toxicity and a high degree of target specificity. The antifungal drugs in development include new azoles {voriconazole, posaconazole (formerly SCH-56592), ravuconazole (formerly BMS-207147)}, lipid formulations of amphotericin B, a lipid formulation of nystatin, echinocandins {anidulafungin (formerly, LY-303366, VER-002), caspofungin (formerly MK-991), micafungin (formerly FK-463)}, antifungal peptides other than echinocandins, and sordarin derivatives. This discussion reviews the currently available antifungal agents and summarises the developmental issues that surround these new systemic antifungal drugs.

Liposomal nystatin in patients with invasive aspergillosis refractory to or intolerant of amphotericin B

We assessed the activity and safety of liposomal nystatin, a broad-spectrum antifungal agent, for invasive aspergillosis in patients refractory to or intolerant of amphotericin B. Thirty-three patients were enrolled, received at least one dose of the study drug, and were evaluable for safety. Twenty-six patients had confirmed probable or definite aspergillosis and were fully eligible. Most patients had a hematological malignancy (53.8%) or hematopoietic stem cell transplantation (23.0%), were neutropenic (61.5%), and were refractory to previous amphotericin B (92.3%). The median duration of previous amphotericin B treatment was 16.5 days (range, 5 to 64 days). Aspergillosis was definite in 3 cases and probable in 23 cases. Liposomal nystatin was initiated at a dose of 4 mg/kg of body weight/day. Twenty-five patients were evaluable for response: a complete response was achieved for one patient, and a partial response was achieved for six. Thus, the overall response rate is 7 of 25 (28%; 95% confidence interval, 12 to 49%). Seventeen (68.0%) of the 25 evaluable patients died during therapy or within 1 month after the end of therapy. The primary cause of death was invasive aspergillosis for nine patients and underlying malignancy for eight patients. The most frequent side effects included chills, shivering, and fever, leading to discontinuation of therapy for two patients. Grade 1 decline in renal function was seen for 10 (30.3%) patients, and hypokalemia was seen for 13 (39.4%). We conclude that liposomal nystatin can be effective for salvage therapy of invasive aspergillosis. Infusion-related adverse events have been observed frequently.

Comparative drug disposition, urinary pharmacokinetics, and renal effects of multilamellar liposomal nystatin and amphotericin B deoxycholate in rabbits

The comparative drug dispositions, urinary pharmacokinetics, and effects on renal function of multilamellar liposomal nystatin (LNYS; Nyotran) and amphotericin B deoxycholate (DAMB; Fungizone) were studied in rabbits. Drug concentrations were determined by high-performance liquid chromatography as total concentrations of LNYS and DAMB. In comparison to a standard dose of 1 mg of DAMB/kg of body weight, therapeutic dosages of LNYS, i.e., 2, 4, and 6 mg/kg, resulted in escalating maximum concentrations (Cmax) (17 to 56 microg/ml for LNYS versus 3.36 microg/ml for DAMB; P<0.001) and values for the area under the concentration-time curve from 0 to 24 h (AUC(0-24)) (17 to 77 microg.h/ml for LNYS versus 12 microg.h/ml for DAMB; P<0.001) in plasma but a significantly faster total clearance from plasma (0.117 to 0.080 liter/h/kg for LNYS versus 0.055 liter/h/kg for DAMB; P=0.013) and a < or =8-fold-smaller volume of distribution at steady state (P=0.002). Urinary drug concentration data revealed a > or =10-fold-higher Cmax (16 to 10 microg/ml for LNYS versus 0.96 microg/ml for DAMB; P=0.015) and a 4- to 7-fold-greater AUC(0-24) (63 to 35 microg.h/ml for LNYS versus 8.9 microg.h/ml for DAMB; P=0.015) following the administration of LNYS, with a dose-dependent decrease in the dose-normalized AUC(0-24) in urine (P=0.001) and a trend toward a dose-dependent decrease in renal clearance. Except for the kidneys, the mean concentrations of LNYS in liver, spleen, and lung 24 h after dosing were severalfold lower than those after administration of DAMB (P, <0.002 to <0.001). Less than 1% each of the total dose of LNYS was recovered from the kidneys, liver, spleen, and lungs; in contrast, a quarter of the total dose was recovered from the livers of DAMB-treated animals. LNYS had dose-dependent effects on glomerular filtration and distal, but not proximal, renal tubular function which did not exceed those of DAMB at the highest investigated dosage of 6 mg/kg. The results of this experimental study demonstrate fundamental differences in the dispositions of LNYS and DAMB. Based on its enhanced urinary exposure, LNYS may offer a therapeutic advantage in systemic fungal infections involving the upper and lower urinary tracts that require therapy with antifungal polyenes.

Antifungal agents of use in animal health--chemical, biochemical and pharmacological aspects

A limited number of antifungal agents is licensed for use in animals, however, many of those available for the treatment of mycoses in humans are used by veterinary practitioners. This review includes chemical aspects, spectra of activity, mechanisms of action and resistance, adverse reactions and drug interactions of the antifungals in current use.

New nystatin polymeric complexes and their in vitro antifungal evaluation in a model study with Fusarium oxysporum

Six water-soluble nystatin-polyvilnylpyrrolidone complexes with respective MW of 10 kDa (NC1), 25 kDa (NC2), 30 kDa (NC3), 40 kda (NC4), 90 kDa (NC5), 360 kDa (NC6) were synthesized. The activity of the complexes was compared with that of nystatin against growth and spore germination of Fusarium oxysporum f.sp. radiciscucumerinum. The ED50 value (effective dose) of free nystatin in aqueous solution on growth inhibition on solid medium was determined at 35.7 ppm. The ED50 of the complexes NC3, NC4, NC5, and NC6 ranged from 2.2 to 4 times lower than that of nystatin. The NC6 complex exhibited the highest activity, followed by NC5, NC4, and NC3. The activities of NC1 and NC2 were about 3 and 1.7 times higher than nystatin respectively in the same in vitro model. The complexes NC6. NC1 and NC4 were 25.4, 13.6 and 6.9 times more active respectively than nystatin against spore germination of E oxysporum. The activity of the nystatin complexes was dependent on the molecular weight of the polymeric carrier.

In vitro activity of nystatin compared with those of liposomal nystatin, amphotericin B, and fluconazole against clinical Candida isolates

We investigated the in vitro activity of nystatin and liposomal nystatin against 103 Candida isolates to determine the effect of both time and medium on MICs. We also compared the nystatin MICs with those of amphotericin B and fluconazole. Testing was performed in accordance with the National Committee for Clinical Laboratory Standards M27-A microdilution methodology with RPMI 1640, RPMI 1640 supplemented with glucose to 2% (RPMI-2), and antibiotic medium 3 supplemented with glucose to 2% (AM3). While nystatin MICs were similar to or slightly lower than liposomal nystatin MICs in RPMI 1640 and RPMI-2, they were markedly higher than liposomal nystatin MICs in AM3. Use of AM3 and determination of the MIC after 24 h of incubation provided a slightly wider range of liposomal nystatin MICs (0.06 to >16 microg/ml). Under these conditions, the MICs at which 90% of isolates were inhibited of nystatin and liposomal nystatin were 2 and 1 microg/ml, respectively. Nystatin and liposomal nystatin in general showed good activity against all Candida spp. tested. Although the MICs of nystatin and liposomal nystatin tended to rise in parallel with the amphotericin B MICs, nystatin and liposomal nystatin MICs of 1 to 2 and 0.5 to 1 microg/ml, respectively, were obtained for seven and six, respectively, of nine isolates for which amphotericin B MICs were >or=0.25 microg/ml. No correlation between fluconazole and nystatin or liposomal nystatin MICs was observed. As amphotericin B MICs of >or=0.25 microg/ml correlate with in vitro resistance, these results suggest that liposomal nystatin might have activity against some amphotericin B-resistant isolates. In vivo testing in animal models is required for clarification of this issue.

Candida: a causative agent of an emerging infection

Incidences of infections due to Candida have increased over the last 15-20 y. This increase in the incidence and the high associated mortality rate despite therapy has focused the attention on this disease and prompted investigators to undertake research aimed at understanding the pathogenesis of this disease as well as methods to treat it. This paper discusses recent developments in the Candida field and the impact they have on patient management.

Differential antifungal activity of isomeric forms of nystatin

When nystatin is placed in RPMI and other biological fluids, there is loss of pure nystatin, with the development of two distinguishable chromatographic peaks, 1 and 2. Peak 1 appears identical to commercially prepared nystatin. By nuclear magnetic resonance (NMR) and mass spectral analysis, peak 2 appears to be an isomer of peak 1. The isomers are quantitatively and fully interconvertible. Formation of peak 2 is accelerated at a pH of >7.0 and ultimately reaches a near 55:45 (peak 1/peak 2 ratio) mixture. We sought to determine the relative activities of peaks 1 and 2 against Candida spp. Peak 2 consistently showed higher MICs when it was the predominant form during the experiment. Time-kill analyses showed that peak 2 required > or =8 x the concentration of peak 1 to produce a modest and delayed killing effect, which was never of the same magnitude as that produced by peak 1. In both types of assays, the activity of peak 2 corresponded with intra-assay formation of peak 1. Both MIC measurements and time-kill analysis suggest that peak 2 has considerably less activity, if any at all, against Candida spp. Peak 2 may serve as a reservoir for peak 1.

Invasive candidiasis stimulates hepatocyte and monocyte production of active transforming growth factor beta

Candida albicans is an opportunistic fungal pathogen and a major cause of morbidity and mortality in patients with compromised immune function. The cytokine response to tissue invasion by C. albicans can influence the differentiation and function of lymphocytes and other mononuclear cells that are critical components of the host response. While the production of transforming growth factor beta (TGF-beta) has been documented in mice infected with C. albicans and is known to suppress phagocyte function, the cellular source and role of this cytokine in the pathogenesis of systemic candidiasis are not well understood. We have investigated the source of production of TGF-beta by immunohistochemical studies in tissue samples from patients with an uncommon complication of lymphoreticular malignancy, chronic disseminated candidiasis (CDC), and from a neutropenic-rabbit model of CDC. Liver biopsy specimens from patients with documented CDC demonstrated intense staining for extracellular matrix-associated TGF-beta1 within inflammatory granulomas, as well as staining for TGF-beta1 and TGF-beta3 within adjacent hepatocytes. These results correlate with the immunolocalization of TGF-beta observed in livers of infected neutropenic rabbits, using a neutralizing antibody that recognizes the mature TGF-beta protein. Human peripheral blood monocytes incubated with C. albicans in vitro release large amounts of biologically active TGF-beta1. The data demonstrate that local production of active TGF-betas by hepatocytes and by infected mononuclear cells is a component of the response to C. albicans infection that most probably contributes to disease progression in the immunocompromised host.

Antifungal pharmacodynamics: concentration-effect relationships in vitro and in vivo

The pharmacodynamics of antifungal compounds involve relationships among drug concentrations, time, and antimicrobial effects in vitro and in vivo. Beyond better understanding of a drug's mode of action, characterization of these relationships has important implications for setting susceptibility breakpoints, establishing rational dosing regimens, and facilitating drug development. Important advances have been made in the experimental investigation of pharmacokinetics and pharmacodynamics of antifungal drugs; however, much remains to be learned about specific pathogens and specific sites of infection. Increased incorporation of pharmacokinetic and pharmacodynamic principles in experimental and clinical studies with antifungal agents is an important objective that will benefit the treatment and prophylaxis of life-threatening invasive fungal infections in immunocompromised patients.

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.

New investigational antifungal agents for treating invasive fungal infections

Systemic fungal infections have been recognised as a major cause of morbidity and mortality during the last two decades. There are only a few therapeutic options for these infections. Severe toxicity, such as impairment of renal function, limits the use of amphotericin B. Flucytosine is associated with side effects and drug resistance. Fluconazole and itraconazole are safer, though emergence of resistance and innate resistance in some fungal pathogens is a concern in their use. Therefore, there is a need for developing novel drugs and/or treatment strategies to combat these infections. In recent years, increased efforts by the pharmaceutical industry and academia have led to the discovery of new re-engineered or reconsidered antifungal agents that are more efficacious, safer and have a broad spectrum of activity. Lipid formulations of polyene antifungal agents, amphotericin B and nystatin, have the advantage of improved therapeutic index. Activity against resistant fungi, high bioavailability, safety and longer half-life are the properties that encourage development of the newer triazoles (e.g., voriconazole, ravuconazole and posaconazole). Echinocandin-like lipopeptide antibiotics are among the antifungal agents with a novel mode of action. In addition to these lead investigational compounds, development of newer antifungal agents is underway.

Compartmental pharmacokinetics and tissue distribution of multilamellar liposomal nystatin in rabbits

The plasma pharmacokinetics of multilamellar liposomal nystatin were studied in normal, catheterized rabbits after single and multiple daily intravenous administration of dosages of 2, 4, and 6 mg/kg of body weight, and drug levels in tissues were assessed after multiple dosing. Concentrations of liposomal nystatin were measured as those of nystatin by a validated high-performance liquid chromatography method, and plasma concentration data were fitted into a two-compartment open model. Across the investigated dosage range, liposomal nystatin demonstrated nonlinear kinetics with more than proportional increases in the AUC(0-24) and decreasing clearance, consistent with dose-dependent tissue distribution and/or a dose-dependent elimination process. After single-dose administration, the mean C(max) increased from 13.07 microg/ml at 2 mg/kg to 41.91 microg/ml at 6 mg/kg (P < 0.001); the AUC(0-24) changed from 11.65 to 67.44 microg. h/ml (P < 0.001), the V(d) changed from 0.205 to 0. 184 liters/kg (not significant), the CL(t) from 0.173 to 0.101 liters/kg. h (P < 0.05), and terminal half-life from 0.96 to 1.51 h (P < 0.05). There were no significant changes in pharmacokinetic parameters after multiple dosing over 14 days. Assessment of tissue concentrations of nystatin near peak plasma levels after multiple dosing over 15 days revealed preferential distribution to the lungs, liver, and spleen at that time point. Substantial levels were also found in the urine, raising the possibility that renal excretion may play a significant role in drug elimination. Liposomal nystatin administered to rabbits was well tolerated and displayed nonlinear pharmacokinetics, potentially therapeutic peak plasma concentrations, and substantial penetration into tissues. Pharmacokinetic parameters were very similar to those observed in patients, thus validating results derived from infection models in the rabbit and allowing inferences to be made about the treatment of invasive fungal infections in humans.