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

Voriconazole enhances UV-induced DNA damage by inhibiting catalase and promoting oxidative stress

Cutaneous squamous cell carcinoma (cSCC) is the second most common form of skin cancer and is associated with cumulative UV exposure. Studies have shown that prolonged voriconazole use promotes cSCC formation; however, the biological mechanisms responsible for the increased incidence remain unclear. Here, we show that voriconazole directly increases oxidative stress in human keratinocytes and promotes UV-induced DNA damage as determined by comet assay, 8-oxoguanine immunofluorescence and mass spectrometry. Voriconazole treatment of human keratinocytes potentiates UV-induced apoptosis and activation of the p38 MAP kinase and 53BP1 UV stress response pathways. The p38 MAP kinase activation promoted by voriconazole exposure can be mitigated by pretreating keratinocytes with N-acetylcysteine. Voriconazole increases oxidative stress in keratinocytes by directly inhibiting catalase leading to lower intracellular NADPH levels and the triazole moieties in voriconazole are critical for inhibiting catalase. Furthermore, voriconazole is shown to promote UV-induced dysplasia in an in vivo model. Together, these data demonstrate that voriconazole potentiates oxidative stress in UV-irradiated keratinocytes through catalase inhibition. Use of antioxidants may mitigate the pro-oncogenic effects of voriconazole.

Anidulafungin: a novel echinocandin for candida infections

A third echinocandin, anidulafungin, has recently been approved for Candida infections in the non-neutropenic patient. In the EU it is indicated for invasive candidiasis; in 2006 it was approved in the USA for candida esophagitis, candidemia, and two types of invasive infections, peritonitis and intra-abdominal abscesses. It is fungicidal against Candida species and fungistatic against Aspergillus species. In addition to its favorable tolerability in studies to date, it does not need adjustment for renal or hepatic insufficiency and has no known drug interactions. A steady state concentration can be achieved on day 2 following a loading dose of twice the maintenance concentration on day 1, and the drug is administered intravenously once daily. Cross resistance with other classes of antifungals is not a concern as it possesses a unique mechanism of action.

Pseudallescheria fusoidea, a new cause of osteomyelitis

Osteomyelitis resulting from a mold infection often presents as a chronic and indolent disease process. Described here for the first time is a case of osteomyelitis of the foot caused by the mold Pseudallescheria fusoidea, which resulted from traumatic implantation after an injury sustained 3 years earlier.

Lysosome and HER3 (ErbB3) selective anticancer agent kahalalide F: semisynthetic modifications and antifungal lead-exploration studies

Kahalalide F (1) shows remarkable antitumor activity against different carcinomas and has recently completed phase I clinical trials and is being evaluated in phase II clinical studies. The antifungal activity of this molecule has not been thoroughly investigated. In this report, we focused on acetylation and oxidation of the secondary alcohol of threonine, as well as reductive alkylation of the primary amine of ornithine, and each product was evaluated for improvements in antifungal activity. 1 and analogues do not exhibit antimalarial, antileishmania, or antibacterial activity; however, the antifungal activity against different strains of fungi was particularly significant. This series of compounds was highly active against Fusarium spp., which represents an opportunistic infection in humans and plants. The in vitro cytotoxicity for the new analogues of 1 was evaluated in the NCI 60 cell panel. Analogue 5 exhibited enhanced potency in several human cancer cell lines relative to 1.

In vitro antifungal susceptibility patterns of dermatophyte strains causing tinea unguium

BACKGROUND

Dermatophytes are the major responsible organisms in onychomycosis. Although recent antifungal agents have high success rates in treating this condition, lack of clinical response may occur in 20%. Antifungal drug resistance may be one of the causes of treatment failure. The need for in vitro antifungal drug resistance in daily practice is still under discussion.

OBJECTIVE

We aimed to determine the in vitro susceptibility patterns of dermatophytes causing onychomycosis, against the traditionally available systemic antifungal agents terbinafine, itraconazole and fluconazole.

METHODS

In total, 100 otherwise healthy patients with suspected onychomycosis were included. Nail clippings were cultured on Sabouraud dexrose agar, mycobiotic agar and dermatophyte test medium. Antifungal susceptibility tests were carried out, mainly following The National Committee for Clinical and Laboratory Standards (M38-P) protocol standard for filamentous fungi. Different concentrations of terbinafine (0.008-8 microg/mL), itraconazole (0.015-16 microg/mL) and fluconazole (0.06-64 microg/mL) were tested. Minimum inhibitory concentration end-point determination was chosen as 100% growth inhibition for terbinafine and 80% for azoles.

RESULTS

Of the 100 nail samples, 43% grew dermatophytes. The main causative organism was Trichophyton rubrum (91%) followed by Trichophyton mentagrophytes (9%). Terbinafine had the lowest minimum inhibitory concentration (0.008 microg/mL) followed by itraconazole. Fluconazole showed the greatest variation in minimum inhibitory concentration (0.03-2 microg/mL) and had different susceptibility patterns for the two species.

CONCLUSIONS

Of the three antifungals tested, terbinafine had the most potent in vitro antifungal activity against dermatophytes. Antifungal susceptibility tests would be useful to screen antifungal-resistant dermatophyte strains.

[Systemic antifungals. Pharmacodynamics and pharmacokinetics]

Invasive fungal infections are important causes of morbidity and mortality in critically ill non neutropenic patients. For many years, amphotericin B and flucytosine have been the only available antifungal agents for invasive fungal infections. Fortunately, the antifungal armamentarium has increased during the past two decades with the addition of several new agents. In addition to itraconazole and fluconazole, lipid formulations of amphotericin B, voriconazole, and caspofungin have been recently licensed. These various antifungal agents differ in their pharmacokinetic and pharmacodynamic profile.

Anidulafungin: a new echinocandin for candidal infections

Anidulafungin, a new echinocandin, has recently been approved for the treatment of esophageal candidiasis, candidemia and other forms of invasive candidiasis, such as peritonitis and intra-abdominal abscesses in non-neutropenic patients. It is fungicidal against Candida spp. including those that are azole- and polyene-resistant and fungistatic against Aspergillus spp. Owing to its poor oral bioavailability it can only be administered intravenously. Its pharmacokinetics allow for once-daily dosing and a steady state concentration is easily achieved on day 2 following a loading dose of double the maintenance dose on day 1. It does not need adjustment for hepatic or renal insufficiency; there are no known drug interactions and it has a favorable tolerability profile. Its mechanism of action, which differs from other classes of antifungals, should prevent cross-resistance with azoles and polyenes.

Endoscopic Surgery for Sinonasal Invasive Aspergillosis in Bone Marrow Transplantation Patients

OBJECTIVES/HYPOTHESIS

Sinonasal invasive aspergillosis (IA) is an aggressive fungal infection with high mortality rates. It commonly develops in immunocompromised patients, often after bone marrow transplantation (BMT). Aggressive surgical debridement by an external approach has been considered a central element of treatment. We describe our experience in endoscopic management of IA in BMT patients in a retrospective study.

METHODS

Charts of BMT patients with IA in the past 5 years were reviewed. Demographic data, primary disease, comorbidities, signs and symptoms, blood test results, preparation for surgery, surgical technique, and outcome were recorded.

RESULTS

Fourteen BMT patients, age ranging from 3 to 56 years, had sinonasal IA. The primary disease was acute myelogenous leukemia in 6, acute lymphoblastic leukemia in 3, chronic myeloblastic leukemia in one, severe combined immunodeficiency disease in 2, and myelodysplastic syndrome in 2 patients. Diagnosis was made by physical examination, biopsy, culture, and computed tomography scan. Treatment, including aggressive endoscopic debridement, a systemic antifungal medication, and local irrigations of amphotericin-B enabled eradication of IA in all patients. Seven patients required two or more operations. None required orbital exenteration or craniotomy. Six patients died of the primary illness or of comorbidities with no evidence of residual disease. Eight patients are alive.

CONCLUSION

Early detection of IA in BMT patients enables aggressive treatment before the disease spreads into the orbit or brain. Proper preoperative preparation facilitates safe endoscopic surgery in patients with severe bleeding tendencies. Although sinonasal IA is lethal, endoscopic surgery is feasible and efficient, enabling excellent local control.

Synthesis of 13-(substituted benzyl) berberine and berberrubine derivatives as antifungal agents

By introducing various aromatic groups in 13-C of berberine and berberrubine, a series of 13-(substituted benzyl) berberine and berberrubine derivatives were synthesized and examined for antifungal activities against various human pathogenic fungi. The synthesized compounds exhibited more potent antifungal activities than berberine and berberrubine. Among them, 13-(4-isopropyl benzyl) berberine (6e) exerted the most potent antifungal activities against Candida species (MIC=1-8 microg/ml) and a 4-fold stronger activity than 13-(4-isopropyl benzyl) berberrubine (7e) synthesized by pyrolysis of compound 6e.

Conserved fungal genes as potential targets for broad-spectrum antifungal drug discovery

The discovery of novel classes of antifungal drugs depends to a certain extent on the identification of new, unexplored targets that are essential for growth of fungal pathogens. Likewise, the broad-spectrum capacity of future antifungals requires the target gene(s) to be conserved among key fungal pathogens. Using a genome comparison (or concordance) tool, we identified 240 conserved genes as candidates for potential antifungal targets in 10 fungal genomes. To facilitate the identification of essential genes in Candida albicans, we developed a repressible C. albicans MET3 (CaMET3) promoter system capable of evaluating gene essentiality on a genome-wide scale. The CaMET3 promoter was found to be highly amenable to controlled gene expression, a prerequisite for use in target-based whole-cell screening. When the expression of the known antifungal target C. albicans ERG1 was reduced via down-regulation of the CaMET3 promoter, the CaERG1 conditional mutant strain became hypersensitive, specifically to its inhibitor, terbinafine. Furthermore, parallel screening against a small compound library using the CaERG1 conditional mutant under normal and repressed conditions uncovered several hypersensitive compound hits. This work therefore demonstrates a streamlined process for proceeding from selection and validation of candidate antifungal targets to screening for specific inhibitors.

Comparison of two methods and three end points in determination of in vitro activity of micafungin against Aspergillus spp

We investigated the in vitro activity of micafungin against clinical Aspergillus isolates (n = 37) (Aspergillusfumigatus [n = 21], Aspergillusflavus [n = 14], and Aspergillus niger [n = 2]) by using NCCLS M38A microdilution and an investigational disk diffusion assay. Microdilution assay results were evaluated by using the end points of a MIC-2 (measured in micrograms per milliliter) and minimum effective concentration (MEC, measured in micrograms per milliliter; the lowest concentration of micafungin that produces short and aberrant hyphal branchings microscopically). Disk diffusion results were interpreted by measuring the zone(s) of inhibition (ZOI, measured in millimeters). Micafungin proved to be similarly active against all Aspergillus species tested. At 24 h, MIC-2s and MECs were identical. At 48 h, however, MIC-2s increased unpredictably, leading to the loss of a consistent correlation between the two end points. MECs and ZOI remained consistent and correlated at both reading times, suggesting their use as relevant end points in susceptibility testing of micafungin against Aspergillus: All Aspergillus isolates yielded intrazonal growth on disk diffusion agar plates. The intrazonal colonies contained short, aberrant hyphal branchings microscopically. The in vivo significance of these findings remains to be further investigated.