Posaconazole and amphotericin B combination therapy against Cryptococcus neoformans infection

In vitro combination with doxycycline plus antifungals against clinical Mucorales pathogens

PURPOSE

Since systematic antifungals for mucormycosis showed variable MICs depending on strains, effective and safe antifungal therapy was still needed. This study is aimed to evaluate the in vitro activity of doxycycline combined with antifungal therapy against dominant Mucorales pathogens.

METHODS

Multidrug susceptibility testing was performed with doxycycline and antifungals, including itraconazole, posaconazole, and amphotericin, in 21 isolates of 8 dominant Mucorales pathogens.

RESULTS

The fractional inhibitory concentration index according to M38 showed one Rhizopus arrhizus isolate synergic (∑FICI = 0.375) and other isolates in addition (0.5 < ∑FICI < 4).

CONCLUSIONS

Doxycycline was found to have in vitro advantages in combined antifungal treatment over antifungals alone.

Integrated therapy for HIV and cryptococcosis

Cryptococcosis has been one of the most common opportunistic infections and causes of mortality among HIV-infected patients, especially in resource-limited countries. Cryptococcal meningitis is the most common form of cryptococcosis. Laboratory diagnosis of cryptococcosis includes direct microscopic examination, isolation of Cryptococcus from a clinical specimen, and detection of cryptococcal antigen. Without appropriate treatment, cryptococcosis is fatal. Early diagnosis and treatment is the key to treatment success. Treatment of cryptococcosis consists of three main aspects: antifungal therapy, intracranial pressure management for cryptococcal meningitis, and restoration of immune function with antiretroviral therapy (ART). Optimal integration of these three aspects is crucial to achieving successful treatment and reducing the mortality. Antifungal therapy consists of three phases: induction, consolidation, and maintenance. A combination of two drugs, i.e. amphotericin B plus flucytosine or fluconazole, is preferred in the induction phase. Fluconazole monotherapy is recommended during consolidation and maintenance phases. In cryptococcal meningitis, intracranial pressure rises along with CSF fungal burden and is associated with morbidity and mortality. Aggressive control of intracranial pressure should be done. Management options include therapeutic lumbar puncture, lumbar drain insertion, ventriculostomy, or ventriculoperitoneal shunt. Medical treatment such as corticosteroids, mannitol, and acetazolamide are ineffective and should not be used. ART has proven to have a great impact on survival rates among HIV-infected patients with cryptococcosis. The time to start ART in HIV-infected patients with cryptococcosis has to be deferred until 5 weeks after the start of antifungal therapy. In general, any effective ART regimen is acceptable. Potential drug interactions between antiretroviral agents and amphotericin B, flucytosine, and fluconazole are minimal. Of most potential clinical relevance is the concomitant use of fluconazole and nevirapine. Concomitant use of these two drugs should be cautious, and patients should be monitored closely for nevirapine-associated adverse events, including hepatotoxicity. Overlapping toxicities of antifungal and antiretroviral drugs and immune reconstitution inflammatory syndrome are not uncommon. Early recognition and appropriate management of these consequences can reinforce the successful integrated therapy in HIV-infected patients with cryptococcosis.

Posaconazole: when and how? The clinician's view

Posaconazole is the newest triazole antifungal agent available as an oral suspension with an extended spectrum of activity against Candida species, Aspergillus species, Cryptococcus neoformans, Zygomycetes and endemic fungi. Among posaconazole advantages are the relatively low potential of cross-resistance with other azoles, few drug interactions compared with other azoles and its activity against Zygomycetes. Randomised, double-blind trials have shown that posaconazole is effective for prophylaxis against invasive fungal infections (IFI), especially aspergillosis, in high-risk patients. Results of Phase III clinical trials and case/series reports indicate that posaconazole is effective in treating oesophageal candidiasis, including azole-refractory disease, and other IFI refractory to standard antifungal therapies. To date, posaconazole has appeared to be well tolerated even in long-term courses; it has an excellent safety profile with gastrointestinal disturbances being the most common adverse events reported. The dose of posaconazole is 200 mg three times daily for prophylaxis, 800 mg daily in two or four divided doses for the treatment of IFI and 100 mg daily (200 mg loading dose) for the treatment of oropharyngeal candidiasis. On the basis of early clinical experience, it appears that posaconazole will be a valuable aid in the management of life-threatening fungal infections.

Pharmacotherapy of yeast infections

The rise of immunocompromised individuals in our society has provoked a significant emergence in the number of patients affected by opportunistic pathogenic yeast. The microorganisms with a major clinical incidence are species from the genera Candida (especially Candida albicans) and Cryptococcus (particularly Cryptococcus neoformans), although there has been a significant increase in other pathogenic yeasts, such as Trichosporon spp. and Rhodotorula spp. In addition, there are an increasing number of patients infected by yeasts that were not previously considered as pathogenic, such as Saccharomyces cerevisiae. The management of these infections is complicated and is highly dependent on the susceptibility profile not only of the species but also of the strain. The available antifungal compounds belong mainly to the polyene, azole and candin families, which show a distinct spectrum of activity. This review summarizes the current knowledge about the use of the main antifungals for treating infections caused by the yeast species with the most significant clinical relevance, including the susceptibility profiles exhibited by these species in vitro.

In Vitro activity of the new azole isavuconazole (BAL4815) compared with six other antifungal agents against 162 Cryptococcus neoformans isolates from Cuba

Cuban Cryptococcus isolates (n = 165) were tested in vitro against amphotericin B, flucytosine, fluconazole, itraconazole, voriconazole, posaconazole, and isavuconazole, giving MIC90 values of 0.25, 8, 4, 0.25, 0.125, 0.016, and 0.016 microg/ml, respectively. Isavuconazole and posaconazole seem to be potentially active drugs for treating cryptococcal infections.

Structural robustness of metabolic networks with respect to multiple knockouts

We present a generalised framework for analysing structural robustness of metabolic networks, based on the concept of elementary flux modes (EFMs). Extending our earlier study on single knockouts [Wilhelm, T., Behre, J., Schuster, S., 2004. Analysis of structural robustness of metabolic networks. IEE Proc. Syst. Biol. 1(1), 114-120], we are now considering the general case of double and multiple knockouts. The robustness measures are based on the ratio of the number of remaining EFMs after knockout vs. the number of EFMs in the unperturbed situation, averaged over all combinations of knockouts. With the help of simple examples we demonstrate that consideration of multiple knockouts yields additional information going beyond single-knockout results. It is proven that the robustness score decreases as the knockout depth increases. We apply our extended framework to metabolic networks representing amino acid anabolism in Escherichia coli and human hepatocytes, and the central metabolism in human erythrocytes. Moreover, in the E. coli model the two subnetworks synthesising amino acids that are essential and those that are non-essential for humans are studied separately. The results are discussed from an evolutionary viewpoint. We find that E. coli has the most robust metabolism of all the cell types studied here. Considering only the subnetwork of the synthesis of non-essential amino acids, E. coli and the human hepatocyte show about the same robustness.

Successful treatment of disseminated mucormycosis with a combination of liposomal amphotericin B and posaconazole in a patient with acute myeloid leukaemia

The combination of resection of infected tissue and antifungal therapy is the treatment of choice in mucormycosis. In disseminated mucormycosis, where surgery is impossible, the mortality is almost 90%. We report the first case of disseminated mucormycosis that was cured with a combination therapy of liposomal amphotericin B and posaconazole without surgical intervention.

Posaconazole Oral Suspension

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Immunomodulation with CD40 stimulation and interleukin-2 protects mice from disseminated cryptococcosis

Cryptococcus neoformans is a ubiquitous fungus that can cause life-threatening infections during immunosuppressive states such as AIDS and after bone marrow transplantation. In this study we investigated the antifungal efficacy of an agonist antibody to CD40, an important costimulator of immune function, in combination with interleukin 2 (IL-2) in a murine model of disseminated cryptococcosis. Only the combination of anti-CD40 and IL-2 significantly prolonged the survival time of infected mice. This protection was correlated with decreased yeast burdens in the brain and kidney. Increased immune cell populations in the spleens, as well as increased serum gamma interferon (IFN-gamma) and tumor necrosis factor alpha levels were observed in infected mice treated with anti-CD40 and IL-2. Further experiments with IFN-gamma knockout mice demonstrated that the protection induced by anti-CD40 and IL-2 treatment was dependent on IFN-gamma. Depletion of CD4+ T cells did not affect the increased serum IFN-gamma levels induced by anti-CD40 and IL-2 treatment and, importantly, did not affect the antifungal effect of combination therapy. These studies indicate that immunotherapy using anti-CD40 and IL-2 has therapeutic potential in augmenting host resistance to disseminated cryptococcosis and that IFN-gamma is essential for efficacy.

Treatment of Candida glabrata infection in immunosuppressed mice by using a combination of liposomal amphotericin B with caspofungin or micafungin

While Candida albicans remains the most common Candida isolate, Candida glabrata accounts for approximately 15 to 20% of all Candida infections in the United States. In this study we used immunosuppressed mice infected with C. glabrata to investigate the efficacy of liposomal amphotericin B alone or in combination with the echinocandin caspofungin or micafungin. For monotherapy, mice were given six daily doses of liposomal amphotericin B (3 to 20 mg/kg of body weight), caspofungin (1 to 5 mg/kg), or micafungin (2.5 to 10 mg/kg). With concomitant therapy, mice received liposomal amphotericin B (7.5 mg/kg) in addition to caspofungin (2.5 mg/kg) or micafungin (2.5 mg/kg) for 6 days. For sequential therapy, liposomal amphotericin B was administered on days 1 to 3 and caspofungin or micafungin was given on days 4 to 6; conversely, caspofungin or micafungin was administered on days 1 to 3 and liposomal amphotericin B was given on days 4 to 6. Efficacy was based on the number of CFU per gram of kidney 21 days postchallenge. Monotherapy with liposomal amphotericin B (7.5 to 20 mg/kg) was significantly more effective than no drug treatment (control group) (P < 0.05) and demonstrated a dose-dependent response, with 20 mg/kg lowering the CFU/g from 6.3 to 4.2 (significantly different from the value for the control group [P < 0.001]). Monotherapy with all echinocandin doses lowered the CFU/g from 6.0 to 6.4 to 2.7 to 3.3 (significantly different from the value for the control group [P < 0.001]) with no dose-dependent response. Complete clearance of infection could be achieved only when liposomal amphotericin B was given either concomitantly with caspofungin or micafungin or if liposomal amphotericin B was given sequentially with caspofungin. In conclusion, the combination of liposomal amphotericin B with an echinocandin markedly improved the therapeutic outcome in murine C. glabrata systemic infection.

Posaconazole: a broad-spectrum triazole antifungal

Posaconazale is a new triazole drug being investigated in phase III clinical trials for the treatment and prevention of invasive fungal infections. In-vitro and in-vivo studies showed that posaconazole has broad-spectrum activity against most Candida species, Cryptococcus neoformans, Aspergillus species, Fusarium species, zygomycetes, and endemic fungi. Posaconazole is given orally two to four times daily. This triazole is widely distributed in the body, metabolised mainly by the liver, and is well tolerated, even in long-term courses. Adverse events are generally mild and include headache and gastrointestinal complaints. Posaconazole has shown promising clinical efficacy against life-threatening fungal infections that are often refractory to the currently available antifungal therapies-eg, invasive aspergillosis, fusariosis, and the emerging zygomycosis.

Management of intracranial fungal infections in patients with haematological malignancies

The incidence of, and mortality associated with, invasive fungal infections remains far higher than hoped. As a consequence of the overall increase in the incidence of such infections over time, the incidence of central nervous system (CNS) fungal infections is also increasing and, despite improvements in diagnostic techniques and the introduction of novel antifungal agents, therapy for CNS infections is still associated with discouragingly poor results. In patients with haematological malignancies, opportunistic infections with Candida or Aspergillus remain the most common infections affecting the CNS; however, opportunistic infections with less well-known fungi are becoming more common and must be considered in the differential diagnosis. New techniques for the early diagnosis of invasive fungal infections are emerging. Pharmacologic options for treating invasive fungal infections have also improved during the past few years, with new drugs becoming available that have broader antifungal spectra and better safety profiles. Other novel treatment approaches, such as combination therapy, are also being explored. Early investigations have produced encouraging results; however, large, prospective studies involving many patients are necessary to validate the widespread use of these approaches. This review analyses the existing guidelines for treatment of CNS fungal infections and the literature available on the use of new drugs to generate sets of recommendations for treatment of these life-threatening infections in patients with haematological malignancies.

Posaconazole

Posaconazole is a triazole antifungal agent, administered as an oral suspension, with an extended spectrum of in vitro activity. Posaconazole 800 mg/day demonstrated clinically relevant activity against a range of fungi in patients with invasive fungal infections who were refractory to, or intolerant of, other antifungal therapy in an open-label, multicentre, phase III study (330 patients received posaconazole and 279 patients served as external controls). In aspergillosis, the global response success rate at the end-of-therapy visit (primary endpoint) was significantly higher in posaconazole recipients than in external controls (42% vs 26%). Posaconazole was also associated with overall success rates of 54% in zygomycosis, 46% in fusariosis, 43% in Pseudallescheria infection, 80% in phaeohyphomycosis and 100% in histoplasmosis. Success rates were 48% in refractory candidiasis, 69% in refractory coccidioidomycosis, 48% in refractory cryptococcal infection and 82% in refractory chromoblastomycosis or mycetoma. Posaconazole also demonstrated potential in febrile neutropenia in an open-label phase II study (success rate of 81% 7 days after the end of treatment). In a noncomparative, multicentre, phase III study in patients with advanced HIV infection who had azole-refractory oropharyngeal and/or oesophageal candidiasis, posaconazole 400 or 800 mg/day resulted in a clinical response in 132 of 176 patients (75%). Oral posaconazole suspension was generally well tolerated in patients with invasive fungal infections, including patients who received treatment for >or=1 year.

Activity of posaconazole in the treatment of central nervous system fungal infections

OBJECTIVES

A multinational, multicentre, open-label clinical trial was conducted to evaluate the safety and efficacy of posaconazole, an extended-spectrum triazole antifungal agent, in subjects with invasive fungal infections who had refractory disease or who were intolerant of standard antifungal therapy. In this subanalysis, we report on those subjects in this trial who had a fungal infection that involved the CNS.

METHODS

Subjects received posaconazole oral suspension 800 mg/day in divided doses for up to 1 year; however, subjects could receive additional therapy as part of a treatment-use extension protocol. A blinded, third-party data review committee determined subject eligibility and outcome.

RESULTS

Of the 330 subjects who enrolled in the study, 53 had infections of the CNS, of which 39 were considered evaluable for efficacy. Most had refractory disease (37 of 39) and underlying HIV infection (29 of 39). Twenty-nine subjects had cryptococcal infections, and 10 had infections caused by other fungal pathogens [Aspergillus spp. (four), Pseudallescheria boydii (two), Coccidioides immitis (one), Histoplasma capsulatum (one), Ramichloridium mackenziei (one), and Apophysomyces elegans plus a Basidiomycetes sp. (one)]. Successful outcomes were observed in 14 of 29 (48%) subjects with cryptococcal meningitis and five of 10 (50%) subjects with CNS infections due to other fungal pathogens. Posaconazole was well tolerated.

CONCLUSIONS

These data suggest that posaconazole, as an oral medication, has clinical activity against fungal infections of the CNS and may provide a valuable alternative to parenteral therapy in patients failing existing antifungal agents.