Combined action of micafungin, a new echinocandin, and human phagocytes for antifungal activity against Aspergillus fumigatus

Pulmonary surfactant impacts in vitro activity of selected antifungal drugs against Candida krusei and Candida albicans

PURPOSE

This study investigates how surfactants affect the in-vitro anti-infective efficacy of micafungin, caspofungin, anidulafungin, and amphotericin B in treating pulmonary mycoses.

METHODS

MIC values for antifungal agents were determined against Candida krusei (now Pichia kudriavzevii) ATCC 6258, Candida albicans ATCC 90028, and 18 clinical isolates using the broth microdilution method in RPMI medium, following EUCAST recommendations. MIC assays included testing with and without Curosurf® surfactant at 1 mg/mL for C. krusei ATCC 6258 and all C. krusei isolates. Subsequent Time-kill studies in Sabouraud broth involved testing both C. albicans ATCC 90028 and C. krusei ATCC 6258 strains at concentrations equal their respective MIC values, with and without surfactant, using all four antifungals. CFU/mL were assessed at multiple time points up to 24 h. TKCs with different surfactant concentrations for C. krusei ATCC 6258 and mini-TKCs at various concentrations relative to the MIC of C. krusei isolates and the reference strain were conducted with micafungin, anidulafungin, and caspofungin.

RESULTS

MIC results showed that 1 µg/mL surfactant reduced killing of micafungin and anidulafungin against C. krusei, while caspofungin was unaffected. Amphotericin B's MIC decreased by half. TKCs demonstrated significant effects of surfactant on micafungin and anidulafungin against C. krusei, with complete abolition of anidulafungin's activity against C. albicans.

CONCLUSION

This in-vitro study highlights the concentration-dependent inhibitory effect of surfactant on antifungal activity against C. krusei and, to some extent, C. albicans, necessitating further clinical validation for invasive lung mycoses treatment.

Interaction in vitro of pulmonary surfactant with antifungal agents used for treatment and prevention of invasive aspergillosis

BACKGROUND

Optimizing antifungal therapy is important to improve outcomes in severely immunocompromised patients.

OBJECTIVES

We analysed the in vitro interaction between pulmonary surfactant and antifungal agents used for management of invasive pulmonary aspergillosis.

METHODS

Amphotericin B formulations, mould-active triazoles and echinocandins were tested in vitro against 24 clinical isolates of different Aspergillus spp. with and without the addition of a commercial porcine surfactant (Curosurf®; Poractant alfa, Nycomed, Austria). The data are presented as MIC or minimum effective concentration (MEC) ranges, as MIC or MEC values that inhibited 90% of the isolates (MIC90 or MEC90) and as geometric mean (GM) MIC or MEC values.

RESULTS

For amphotericin B products, addition of surfactant to a final concentration of 10% led to a statistically significant reduction of the GM MIC for all Aspergillus isolates tested after 24 h (0.765 versus 0.552 mg/L; P < 0.05). For the mould-active triazoles, addition of 10% surfactant resulted in a significantly higher GM MIC at 48 h (0.625 versus 0.898 mg/L; P < 0.05). For the echinocandins, the addition of 10% surfactant led to a significantly higher GM MEC after both 24 h (0.409 versus 0.6532 mg/L; P < 0.01) and 48 h (0.527 versus 0.9378 mg/L; P < 0.01). There were no meaningful differences between individual members of the three existing classes of antifungal agents or between the different Aspergillus spp. tested.

CONCLUSIONS

Using EUCAST methodology, addition of porcine surfactant up to a concentration of 10% had a minor, and presumably non-relevant, impact on the in vitro activity of antifungal agents used in prophylaxis and treatment of invasive pulmonary aspergillosis.

In vivo Activity of Copper(II), Manganese(II), and Silver(I) 1,10-Phenanthroline Chelates Against Candida haemulonii Using the Galleria mellonella Model

Candida haemulonii is an emerging opportunistic pathogen resistant to most antifungal drugs currently used in clinical arena. Metal complexes containing 1,10-phenanthroline (phen) chelating ligands have well-established anti-Candida activity against different medically relevant species. This study utilized larvae of Galleria mellonella, a widely used model of in vivo infection, to examine C. haemulonii infection characteristics in response to different copper(II), manganese(II), and silver(I) chelates containing phen, which had demonstrated potent anti-C. haemulonii activity in a previous study. The results showed that C. haemulonii virulence was influenced by inoculum size and incubation temperature, and the host G. mellonella immune response was triggered in an inoculum-dependent manner reflected by the number of circulating immune cells (hemocytes) and observance of larval melanization process. All test chelates were non-toxic to the host in concentrations up to 10 μg/larva. The complexes also affected the G. mellonella immune system, affecting the hemocyte number and the expression of genes encoding antifungal and immune-related peptides (e.g., inducible metalloproteinase inhibitor protein, transferrin, galiomycin, and gallerimycin). Except for [Ag₂(3,6,9-tdda)(phen)₄].EtOH (3,6,9-tddaH₂ = 3,6,9-trioxoundecanedioic acid), all chelates were capable of affecting the fungal burden of infected larvae and the virulence of C. haemulonii in a dose-dependent manner. This work shows that copper(II), manganese(II), and silver(I) chelates containing phen with anti-C. haemulonii activity are capable of (i) inhibiting fungal proliferation during in vivo infection, (ii) priming an immune response in the G. mellonella host and (iii) affecting C. haemulonii virulence.

Echinocandin antifungals: review and update

The echinocandins are a new and unique class of antifungal agents that act on the fungal cell wall by way of noncompetitive inhibition of the synthesis of 1,3-beta-glucans. All agents of this class are of parenteral formulation, with no oral preparations available. Caspofungin (Cancidas) was the first approved echinocandin, followed recently by micafungin (Mycamine) and anidulafungin (Eraxis). The precise role of the echinocandins in the antifungal armamentarium is still unfolding. Caspofungin is approved for the treatment of candidal esophagitis and candidemia, salvage therapy of Aspergillus infections and for empirical therapy of febrile neutropenia. Micafungin is likewise approved for candidal esophagitis, in addition to antifungal prophylaxis for hematopoietic stem cell transplant recipients. Anidulafungin is also approved for treatment of candidal esophagitis, as well as therapy of candidemia. There has been anecdotal use of these agents to treat less common fungal pathogens, as well as limited use as a component of combination antifungal therapy. The echinocandins are an important addition to the antifungal armamentarium in the treatment of fungal infections in both immunocompromised patients and those with normal immunity.

Interaction of platelets and anidulafungin against Aspergillus fumigatus

The combination of platelets and anidulafungin at 0.03 μg/ml significantly (P < 0.05) reduced the germination rate and hyphal elongation in Aspergillus fumigatus compared to those with either anidulafungin only or an untreated control. Platelets decreased the expression of the fks gene, which plays an important role in cell wall synthesis. Our results suggest that human platelets plus anidulafungin might contribute to defense against A. fumigatus.

Immunomodulatory properties of antifungal agents on phagocytic cells

Phagocytic cells, particularly neutrophils and monocytes/macrophages, are the first line and the most effective form of innate host defence against pathogenic fungi. During antifungal therapy these phagocytic cells are also exposed to antifungal agents. In the phagocyte-fungus-antifungal agent interplay, drugs may directly interact with phagocytes through specific pattern recognition receptors, leading to altered antifungal activities. Antifungal agents, through modulation of fungal virulence, may initiate different immune response programs in the phagocytes, leading to antifungal synergism/antagonism or up-regulation of gene expression for a pro-inflammatory response. Additionally, indirect modulation of phagocyte behavior by pretreatment of neutrophils, monocytes, and macrophages with cytokines and exposure to antifungal agents have shown promising findings for combined drug-cytokine therapy that may improve treatment of life-threatening fungal diseases. In this review, we discuss the main in vitro and in vivo immunomodulatory effects of antifungal agents on phagocytes in response to pathogenic fungi, as well as we address underlying immunopharmacologic mechanisms and their potential impact on clinical outcome.

Endogenous aspergillus endophthalmitis after kidney transplantation

Endogenous aspergillus endophthalmitis(EAE) after kidney transplant is a rare but important clinical problem due to potentially devastating consequences. Early diagnosis of EAE, timely removal of affected vitreous by vitrectomy, proper anti-fungal treatment, all contributed to the successful control of the disease. Therapeutic success of EAE in post-transplant patients depends largely on prompt diagnosis. Definite diagnosis of EAE is based on positive culture results of vitreous specimen, while fundoscopy and B scan ultrasound may aid early diagnosis. In terms of anti-fungal medicine, amphotericin B has long been the first choice, but its systemic applicaiton has severe adverse reactions, especially for patients with impaired renal function. Herein, we report the treatment modality of EAE after kidney transplant with vitrectomy, systemic administration of micafungin plus voriconazole, topical application of fluconazol and amphotercin B.

Comparison of echinocandin antifungals

The incidence of invasive fungal infections, especially those due to Aspergillus spp. and Candida spp., continues to increase. Despite advances in medical practice, the associated mortality from these infections continues to be substantial. The echinocandin antifungals provide clinicians with another treatment option for serious fungal infections. These agents possess a completely novel mechanism of action, are relatively well-tolerated, and have a low potential for serious drug-drug interactions. At the present time, the echinocandins are an option for the treatment of infections due Candida spp (such as esophageal candidiasis, invasive candidiasis, and candidemia). In addition, caspofungin is a viable option for the treatment of refractory aspergillosis. Although micafungin is not Food and Drug Administration-approved for this indication, recent data suggests that it may also be effective. Finally, caspofungin- or micafungin-containing combination therapy should be a consideration for the treatment of severe infections due to Aspergillus spp. Although the echinocandins share many common properties, data regarding their differences are emerging at a rapid pace. Anidulafungin exhibits a unique pharmacokinetic profile, and limited cases have shown a potential far activity in isolates with increased minimum inhibitory concentrations to caspofungin and micafungin. Caspofungin appears to have a slightly higher incidence of side effects and potential for drug-drug interactions. This, combined with some evidence of decreasing susceptibility among some strains of Candida, may lessen its future utility. However, one must take these findings in the context of substantially more data and use with caspofungin compared with the other agents. Micafungin appears to be very similar to caspofungin, with very few obvious differences between the two agents.

Echinocandin pharmacodynamics: review and clinical implications

Echinocandins have made a significant impact in the treatment of select invasive fungal infections, most notably invasive candidiasis and aspergillosis. However, treatment outcomes for such infections are still less than optimal, prompting an examination of dosing and administration techniques in an attempt to exploit known pharmacodynamic properties and improve outcomes. Echinocandins generally exhibit concentration-dependent, fungicidal activity against Candida spp. and fungistatic activity against Aspergillus spp. However, increasing drug concentrations of echinocandins above the organism's MIC may result in a paradoxical increase in fungal growth as demonstrated in some in vitro and in vivo models (known most commonly as the 'Eagle effect'). Therefore, the potential impact of dose escalations on improving the clinical efficacy of echinocandins based on in vitro and animal models are uncertain and are still being evaluated. In addition, such strategies have to consider the potential for increased treatment-related toxicities and costs. To date, published clinical studies (both superiority and non-inferiority) demonstrating the potential for dose-related improvements in treatment outcomes have been limited to mucocutaneous and oesophageal candidiasis. Further research is needed to determine if a role exists for optimizing echinocandin pharmacodynamics in various clinical settings.

[Future role of micafungin in the treatment of invasive mycoses caused by filamentous fungi]

BACKGROUND

Micafungin is a echinocandin. It inhibits beta-1,3-D-glucan synthesis, thus achieving fungicidal activity against virtually all Candida spp., including those resistant to fluconazole, and fungistatic activity against Aspergillus spp., as well as several but not all pathogenic molds. Results from in vitro studies, animal models, small clinical trials, hint at possible future indications such as invasive aspergillosis and empirical viantifungal therapy, although currently there is little information published.

AIMS

To describe published data of micafungin as treatment against invasive mold infections, specially analysing its role in the inmunodepressed host and critical care setting.

METHODS

A systematic review of literature using the principal medical search engines was performed. Terms such as micafungin, aspergillosis, zygomycosis, invasive fungal infections, emerging fungal infections, antifungal treatment or therapy, antifungal prophylaxis, empiric or pre-emptive therapy were crossed. Febrile neutropenia patients were excluded.

RESULTS

Several studies in these setting were identified and were described in this review. Although there were no blinded randomized clinical trials published, treatment or prophylaxis of invasive aspergillosis and other invasive mould infections with micafungin described in open clinical studies were analyzed.

CONCLUSIONS

Micafungin could play a future important role as a primary or rescue therapy, alone or in combination, in the treatment or prophylaxis of invasive fungal infections caused by moulds. New randomized clinical trials are needed to confirm their efficacy.

Caspofungin-mediated beta-glucan unmasking and enhancement of human polymorphonuclear neutrophil activity against Aspergillus and non-Aspergillus hyphae

BACKGROUND

We investigated whether caspofungin and other echinocandins have immune-enhancing properties that influence human polymorphonuclear neutrophil (PMN)-mediated mold hyphal damage.

MATERIALS AND METHODS

Using aniline blue staining, we compared patterns of beta-glucan exposure in Aspergillus fumigatus, Aspergillus terreus, Rhizopus oryzae, Fusarium solani, Fusarium oxysporum, Scedosporium prolificans, and Scedosporium apiospermum hyphae after caspofungin exposure. We also determined PMN-mediated hyphal damage occurring with or without preexposure to caspofungin or with preexposure to the combination of caspofungin and anti-beta-glucan monoclonal antibody, using 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-sH-tetrazolium hydroxide (XTT) assay.

RESULTS

Preincubation with caspofungin (32 microg/mL for R. oryzae; 0.0625 microg/mL for other isolates) increased exposure to beta-glucan. PMN-induced damage increased after caspofungin exposure and was further augmented by the addition of anti-beta-glucan antibody. Preincubation with micafungin or anidulafungin had similar effects on PMN-induced damage of A. fumigatus hyphae. Finally, preexposure of A. fumigatus, but not S. prolificans, to caspofungin induced expression of Dectin-1 by PMN.

CONCLUSIONS

The results of the present study suggest inducement of beta-glucan unmasking by echinocandins and enhancement of PMN activity against mold hyphae, thereby supporting the immunopharmacologic mode of action of echinocandins.

Comparative in vitro pharmacodynamics of caspofungin, micafungin, and anidulafungin against germinated and nongerminated Aspergillus conidia

The concentration-dependent effects of echinocandins on the metabolic activity of Aspergillus spp. were comparatively studied by using nongerminated and germinated conidia. The susceptibilities of 11 Aspergillus fumigatus, 8 A. terreus and 8 A. flavus isolates to caspofungin, micafungin, and anidulafungin were studied by a CLSI (formerly NCCLS) M38-A broth microdilution-based method. After 48 h of incubation the minimum effective concentration (MEC) was defined microscopically. Metabolic activity was assessed by the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assay and modeled by using the sigmoid (E max) or "bell-shaped" model. The median MEC values of caspofungin (0.5 to 1 microg/ml), micafungin (0.06 to 0.12 microg/ml), and anidulafungin (0.03 microg/ml) against nongerminated conidia increased by 0 to 1, 1 to 2, and 2 to 3 twofold dilutions, respectively (depending on the species), over those against germinated conidia. A similar shift to the right was demonstrated for the corresponding curves of metabolic activity. There was a significant correlation between the degrees of maximal metabolic inhibition caused by different echinocandins at both the species level (greater inhibition for A. flavus) and the strain level (r = 0.84 to 0.93; P < 0.0001). Paradoxical increases in metabolism in the presence of higher concentrations of caspofungin, micafungin, and anidulafungin were detected in 6, 2, and 5 of the A. fumigatus isolates, respectively; 5, 1, and 2 of the A. terreus isolates, respectively; and 1, 0, and 0 of the A. flavus isolates, respectively. Based on the model, 50% of the maximal paradoxical increase was detected with 4.2, 11.1, and 10.8 microg/ml of caspofungin, micafungin, and anidulafungin, respectively. All echinocandins therefore exerted comparable levels of maximal metabolic inhibition against Aspergillus spp. at concentrations that were differentially increased for germinated versus nongerminated conidia. The paradoxical increase in metabolism occurred more frequently and at lower concentrations with caspofungin than with micafungin and anidulafungin.

Micafungin sodium, the second of the echinocandin class of antifungals: theory and practice

Micafungin is a new drug in the echinocandin class and is currently being investigated in Phase III clinical trials. Like other echinocandins, it inhibits 1,3-beta-D-glucan synthesis, thus achieving fungicidal activity against virtually all Candida spp., including those resistant to fluconazole, and fungistatic activity against Aspergillus spp. Micafungin sodium is available for intravenous administration only. It has a favorable safety and drug-drug interaction profile. Micafungin has been approved by the US FDA for treatment of esophageal candidiasis and for antifungal prophylaxis during the pre-engraftment phase in patients undergoing hematopoietic stem cell transplantation. Considering the competitive pricing as well as the good tolerability and efficacy, at present micafungin seems to be another choice for both of these indications. Current research has proven micafungin sodium to add a rational and effective option to the antifungal armamentarium, especially in esophageal candidiasis refractory to fluconazole treatment, in those intolerant to triazoles or in patients needing concomitant therapy interacting with triazoles. In addition to the current indications, recent uncontrolled clinical trials have demonstrated a marked success in the treatment of candidemia and invasive candidiasis. Results from in vitro studies, animal models, small clinical trials, as well as the obvious comparison with the more established caspofungin, hint at possible future indications such as invasive aspergillosis and empirical antifungal therapy. However, preclinical data on micafungin is inconsistent and published well-designed clinical studies are scarce. More controlled and sufficiently scaled trials are imperative in order to establish micafungin as a reliable and safe option in clinical practice.

Efficacy and safety of micafungin in febrile neutropenic patients treated for hematological malignancies

OBJECTIVE

The purpose of this study was to prospectively evaluate the efficacy and safety of micafungin (MCFG) in empirical therapy for febrile neutropenic patients for whom antibiotic therapy was not effective for hematological malignancies.

PATIENTS AND METHODS

Twenty-three hematological patients aged 27-82 years with febrile neutropenia for whom antibiotic therapy was not effective were enrolled in this study and responses to treatment were evaluated.

RESULTS

Treatment success rate was 73.9%. Treatment success rates by primary diagnosis were 77.8% in patients with AML, 50.0% in patients with NHL and 87.5% in patients with other diseases. Moreover, MCFG at a dose of 100 mg or more have a tendency to be effective. One or more adverse events occurred in five (27.7%) of the patients during the study. All of these adverse events were below grade 2 toxicity.

CONCLUSIONS

Although the number of patients studied was limited, MCFG as a monotherapy seems to be effective and safe as an empirical therapy in patients with febrile neutropenia. However, further investigation using large-scale studies is needed. This study demonstrated the clinical efficacy and safety of MCFG in patients with febrile neutropenia and with hematological malignancies.

Micafungin (FK463), alone or in combination with other systemic antifungal agents, for the treatment of acute invasive aspergillosis

BACKGROUND

Micafungin (FK463) is a new lipopeptide compound (echinocandin) with activity against Aspergillus and Candida species. This study evaluated the safety and efficacy of micafungin in patients with proven or probable invasive aspergillosis (IA).

METHODS

A multinational, non-comparative study was conducted to examine proven or probable (pulmonary only) Aspergillus species infection in a wide variety of patient populations. The study employed an open-label design utilizing micafungin alone or in combination with another systemic antifungal agent. Criteria for IA and therapeutic responses were judged by an independent panel.

RESULTS

Of the 331 patients enrolled, only 225 met diagnostic criteria for IA as determined by the independent panel and received at least one dose of micafungin. Patients included 98/225 who had undergone hematopoietic stem cell transplantation (HSCT) (88/98 allogeneic), 48 with graft versus host disease (GVHD), and 83/225 who had received chemotherapy for hematologic malignancy. A favorable response rate at the end of therapy was seen in 35.6% (80/225) of patients. Of those only treated with micafungin, favorable responses were seen in 6/12 (50%) of the primary and 9/22 (40.9%) of the salvage therapy group, with corresponding numbers in the combination treatment groups of 5/17 (29.4%) and 60/174 (34.5%) of the primary and salvage treatment groups, respectively. Of the 326 micafungin-treated patients, 183 (56.1%) died during therapy or in the 6-week follow-up phase; 107 (58.5%) deaths were attributable to IA.

CONCLUSIONS

Micafungin as primary or salvage therapy proved efficacious and safe in high-risk patients with IA, although patient numbers are small in the micafungin-only groups.