Activity Of Posaconazole Research Articles

Enhanced antifungal activity of posaconazole against Candida auris by HIV protease inhibitors, atazanavir and saquinavir

The increasing incidence and dissemination of multidrug-resistant Candida auris represents a serious global threat. The emergence of pan-resistant C. auris exhibiting resistance to all three classes of antifungals magnifies the need for novel therapeutic interventions. We identified that two HIV protease inhibitors, atazanavir and saquinavir, in combination with posaconazole exhibited potent activity against C. auris in vitro and in vivo. Both atazanavir and saquinavir exhibited a remarkable synergistic activity with posaconazole against all tested C. auris isolates and other medically important Candida species. In a time-kill assay, both drugs restored the fungistatic activity of posaconazole, resulting in reduction of 5 and 5.6 log10, respectively. Furthermore, in contrast to the individual drugs, the two combinations effectively inhibited the biofilm formation of C. auris by 66.2 and 81.2%, respectively. Finally, the efficacy of the two combinations were tested in a mouse model of C. auris infection. The atazanavir/posaconazole and saquinavir/posaconazole combinations significantly reduced the C. auris burden in mice kidneys by 2.04- (99.1%) and 1.44-log10 (96.4%) colony forming unit, respectively. Altogether, these results suggest that the combination of posaconazole with the HIV protease inhibitors warrants further investigation as a new therapeutic regimen for the treatment of C. auris infections.

Assessment of the activity of posaconazole against azole-resistant Aspergillus species studied in an in vitro pharmacokinetic/pharmacodynamic model.

Invasive pulmonary aspergillosis (IPA) with azole resistance is associated with a high death rate. Posaconazole is used for IPA as preventive and salvage therapy, and exhibits considerable efficacy against the majority of Aspergillus strains. An in vitro pharmacokinetic-pharmacodynamic (PK-PD) model was used to examine the potential use of posaconazole in a primary therapy against azole-resistant IPA. In an in vitro PK-PD model simulating human pharmacokinetics (PKs), 4 clinical isolates of A. fumigatus with Clinical and Laboratory Standards Institute (CLSI) minimum inhibitory concentrations (MICs) ranging from 0.030 mg/L to 16 mg/L were examined. A bioassay was used to determine drug levels, and galactomannan production was used to evaluate fungal growth. The CLSI/European Committee on Antimicrobial Susceptibility Testing (EUCAST) 48-hour values, gradient concentration strip methodologies (MTS) 24-hour values, in vitro PK-PD relationships, and the Monte Carlo method were used to estimate the simulation of the human dosing regimens of oral 400 mg twice-daily and intravenous (i.v.) 300 mg onceand twice-daily using susceptibility breakpoints. With 1 or 2 daily dosage regimes, the area under the curve (AUC)/MIC associated with 50% of the maximum antifungal activity was 160 and 22.3, respectively. For CLSI/EUCAST, the susceptibility/intermediate/resistant breakpoints were 0.125/0.25-0.5/1 mg/L. For therapeutic drug monitoring (TDM), a trough/MIC ratio of 2.6 was calculated. Therapeutic drug monitoring is not necessary for isolates with MICs of 0.06 mg/L with oral 400 mg twice-daily regimens. However, it is important to obtain MICs of 0.125 mg/L and unavoidable when MICs of 0.25-0.5 mg/L are needed. For non-wild type isolates with MICs of 1-2 mg/L, only i.v. 300 mg twice-daily regimen was effective. Oral therapy with posaconazole can be considered in A. fumigatus isolates with low MIC values without TDM, whereas i.v. therapy should be considered with higher MIC values and may be important in the primary treatment of azole-resistant IPA.

In vitro activity of posaconazole and comparators versus opportunistic filamentous fungal pathogens globally collected during 8 years

The epidemiology of invasive filamentous fungal diseases requires monitoring due to changes in susceptibility patterns of new and established antifungal agents that may affect clinical practices. We evaluated the activity of posaconazole against 2,157 invasive moulds collected worldwide from 2010−2017. The isolates included 1,775 Aspergillus spp. and 382 non-Aspergillus moulds, including 81 Fusarium spp., 62 Mucorales group, and 57 Scedosporium spp. Isolates were tested using the CLSI reference broth microdilution method. Posaconazole showed similar activity to itraconazole and voriconazole against A. fumigatus. Applying published ECV, 98.0% of the A. fumigatus and 97.7% to 100.0% of other common Aspergillus species were wildtype to posaconazole. Categorical agreement between posaconazole and the other azoles tested against A. fumigatus was 98.7%. Notably, most of the Aspergillus spp. isolates recovered from this large collection were wildtype to echinocandins and all azoles. Posaconazole non-wildtype rates of A. fumigatus varied across the different geographic regions, with 2.1% in Europe, 2.2% in North America, 1.8% in Latin America, and 0.7% in the Asia-Pacific region. The frequency of azole non-wildtype A. fumigatus isolates from Europe increased steadily from 2010−2017 for all 3 triazoles (0.0%−5.0%). The azole non-wildtype A. fumigatus rates from the other geographic areas were stable over time. Fusarium and/or Scedosporium spp. isolates were highly resistant to azoles and echinocandins. Posaconazole and amphotericin B were the most active agents against the Mucorales. Posaconazole was very active against most species of Aspergillus and was comparable to itraconazole and voriconazole against the less common moulds. Posaconazole should provide a useful addition to the anti-mould grouping of antifungal agents.

Seifem 2016 Study: Incidence of Probable and Proven Invasive Aspergillosis in Patients with Acute Myeloid Leukemia during Consolidation Therapy

Introduction.During last years, a reduction in invasive aspergillosis (IA) incidence and mortality was observed in acute myeloid leukemia (AML) patients undergoing to induction phase of treatment. Instead, the incidence of IA and the attributable mortality rate (AMR) during the consolidation has not been recently evaluated. It is also uncertain whether posaconazole prophylaxis during induction chemotherapy affects IA on consolidation phase.Design and Methods. The aim of our study was to evaluate incidence and mortality for IA in AML patients during the consolidation phase. All cases of proven/probable IA observed during consolidation chemotherapy in adult and pediatric patients with AML, who received conventional chemotherapy, between 2011 and 2015 were retrospectively collected in a multicenter study involving 38 Italian hematologic centers. All relevant clinical data were collected in CRFs.Results. A total of 2556 of AML patients in consolidation phase were registered. A total of 52 patients (2%) developed an IA [13 proven (0,5%) and 39 probable (1.5%)]. Male/female ratio was 33/19, median age was 57 yrs (range 5-79). As a consolidation, all these patients received high/intermediate doses cytarabine, in combination with an anthracycline in 30. Only 21 of 52 (40%) were on antifungal prophylaxis at the time of IA diagnosis: posaconazole in 5 (24%), fluconazole in 6 (28%), itraconazole in 5 (24%), liposomal amphotericin B (L-AmB) in 4 (19%) and voriconazole in 1 (5%). In 2 of 52 IA was a reactivation of an infection diagnosed during induction (Fig.).Empiric antifungal therapy was initiated in 33 cases (65%) (mainly L-AmB: 24/33, 73%), while the remaining 19 (35%) received a pre-emptive/targeted approach. Fourteen cases switched from L-AmB to voriconazole, so that the most frequently targeted antifungal therapy was voriconazole (29/52, 55%). The median duration of antifungal treatment was 89 days (range 12-700). The overall mortality at day 120 was 19% (10/52), but the AMR was only 3.2% (5/52).During induction, many patients (85%) received posaconazole as antifungal prophylaxis while the remaining 15% received other antifungals. (Fig.) During consolidation, antifungal prophylaxis was performed in about 50% of the patients. The most commonly used drug was fluconazole. In consideration of the hypothesized long-lasting activity of posaconazole, we also performed an analysis of incidence of IA during consolidation taking into whether or not the patients received posaconazole during induction. Considering the overall population of AMLs treated in consolidation no statistical differences were observed between those receiving in induction posaconazole or other prophylaxis, even if a lower percentage of patients in posaconazole arm developed an IA. (Fig.)Conclusion. Our study shows that the incidence of IA during the consolidation in patients with AML is low but not absent. Similarly, also the AMR is low, likely due to advances in diagnosis and antifungal therapy. It is still a matter of discussion whether or not prophylaxis is needed in this subset of patients, since these are in remission and often candidates for transplantation. Finally, the long-lasting benefits of posaconazole is not confirmed but it might be correlated to the few cases of IA observed. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Comparative activity of posaconazole and systemic azole agents against clinical isolates of filamentous fungi from a global surveillance programme.

ObjectivesThe activity of mould-active azoles was evaluated against 397 filamentous fungi causing invasive mould infections (IMI) worldwide. In addition, a tentative posaconazole epidemiological cut-off value (ECV) against Aspergillus fumigatus was investigated.MethodsIsolates were susceptibility tested by the CLSI reference broth microdilution methods. Species identification was confirmed by MALDI-TOF and/or sequencing analysis.ResultsAspergillus spp. (81.9%) remained the most common organism causing IMI worldwide; approximately two-thirds of Aspergillus spp. recovered were A. fumigatus. In general, more than 90% of 220 A. fumigatus isolates were wild type (WT) to all mould-active azoles, except itraconazole (84.5% WT). The voriconazole non-susceptible (NS) A. fumigatus rate was 7.7% overall and was higher in Europe (12.9%) than in the other regions (0%–5.8%). Posaconazole (MIC50/MIC90, 0.25/0.5 mg/L) showed similar or slightly higher activity than voriconazole (MIC50/MIC90, 0.5/0.5 mg/L) and isavuconazole (MIC50/MIC90, 0.5/1 mg/L) against A. fumigatus. The mould-active azoles displayed similar activity against non-fumigatus Aspergillus (WT rates >93%), but differences were observed among the main species/sections. Posaconazole, voriconazole, and isavuconazole inhibited at their respective ECVs 100%, 97.0%, and 100% of A. section Nigri; 100%, 100%, and 93.8% of A. section Terrei; and 97.3%, 100%, and 100% of A. section Flavi isolates. Posaconazole displayed potency greater than or equal to the other azoles against the Mucorales group and Scedosporium spp.ConclusionsPosaconazole and other mould-active azoles showed good activity against Aspergillus spp. causing IMI, but clinicians should be aware of regional rates of voriconazole-NS A. fumigatus.

1169. In Vitro Activity of Posaconazole versus Voriconazole for the Treatment of Invasive Aspergillosis in Adults Enrolled in a Clinical Trial

BackgroundInvasive aspergillosis (IA) is a life-threatening disease with limited treatment options and is associated with delays in effective treatment and significant early mortality. Posaconazole (POS) is a broad-spectrum triazole antifungal, that exhibits potent activity against yeasts and molds. We evaluated the antifungal susceptibility profiles of isolates collected during a randomized, prospective, phase 3, double-blind, double-dummy study comparing posaconazole with voriconazole (1:1 randomization) given for ≤12 weeks in the primary treatment of IA (ClinicalTrials.gov, NCT01782131; EudraCT, 2011-003938-14) using CLSI and EUCAST reference testing methodologies.MethodsMore than 90 study sites located in 23 countries enrolled subjects in the clinical trial. A total of 127 isolates were recovered from documented infections during 2013 through 2019. Fungal isolates were identified using molecular methods and antifungal susceptibility testing was performed by reference broth microdilution methods. The following antifungal agents tested were: posaconazole, itraconazole, voriconazole, caspofungin, and amphotericin BResultsOf the 127 samples tested, 119 were identified as Aspergillus species. Aspergillus fumigatus (N=76) was the most prevalent species, followed by A. flavus species complex (N=19), A. section Nigri (N=10), A. section Terrei (N=7). Overall, posaconazole (MIC50/MIC 90, 0.5/1 mg/L) displayed similar activity to voriconazole (MIC50/MIC90, 0.5/1 mg/L) and itraconazole (MIC50/MIC90, 1/2 mg/L) against 119 Aspergillus species Isolates, by both, CLSI and EUCAST method. Posaconazole (MIC50/MIC90, 0.5/0.5 mg/L) and voriconazole (MIC50/MIC90, 0.25/0.5 mg/L) inhibited all 76 A. fumigatus isolates at MIC of 1 mg/L. Among 19 A. flavus species complex isolates recovered from this study, posaconazole (MIC50/MIC90, 0.5/1 mg/L), voriconazole (MIC50/MIC90, 1/1 mg/L) and itraconazole (MIC50/MIC90, 0.5/1 mg/L) displayed equivalent activity.ConclusionPosaconazole displayed good activity against all Aspergillus species isolates included in this study. In addition, posaconazole in vitro activity against Aspergillus species was similar to that observed by voriconazole and itraconazole.DisclosuresMariana Castanheira, PhD, 1928 Diagnostics (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support)Qpex Biopharma (Research Grant or Support) Leah Woosley, n/a, Merck & Co, Inc. (Research Grant or Support) Mary Motyl, PhD, Merck & Co, Inc (Employee, Shareholder) Seongah Han, PhD, Merck & Co, Inc. (Employee) Havilland Campbell, BS, Merck & Co, Inc. (Employee)

1148. Activity of Posaconazole and Comparator Antifungal agents Tested Against Filamentous Fungi

BackgroundPosaconazole (POS) is a broad-spectrum triazole antifungal that exhibits potent antifungal activity against a variety of yeasts and molds. We evaluated the in vitro activities of posaconazole and comparator antifungal agents against 2,554 isolates of filamentous fungi including 2,100 Aspergillus species and 454 non-Aspergillus moulds (98 Fusarium, 81 Mucorales and 76 Scedosporium species isolates) collected worldwide in 2010-2018 from clinically significant infections.MethodsIsolates were identified using sequencing and/or MALDI-TOF MS methods. Posaconazole, itraconazole, voriconazole, caspofungin, anidulafungin, micafungin, and amphotericin B were tested using the reference broth microdilution method according to CLSI guidelines.ResultsPosaconazole showed comparable activity to itraconazole and voriconazole against A. fumigatus. Categorical agreement between posaconazole and the other azoles tested against A. fumigatus ranged from 98.2-98.7%. Most of the Aspergillus species isolates tested (>90%) were WT to all azoles and echinocandins. Among the isolates of A. fumigatus, the rate of NWT strains varied across the different geographic regions. The frequency of azole NWT strains of A. fumigatus from Europe increased steadily from 2010 to 2018. There was no consistent trend for an increased frequency of NWT strains from other geographic areas. The azoles and echinocandins showed poor activity against Fusarium and Scedosporium species. Posaconazole (MIC50/90, 1/2 mg/L) and amphotericin B (MIC50/90, 1/2 mg/L) were the most active agents against the Mucorales isolates.ConclusionPosaconazole exhibited excellent activity against most species of Aspergillus and was comparable to itraconazole and voriconazole. Most Aspergillus species remain susceptible to triazoles. Although there was no evidence for an increasing frequency of NWT strains among A. fumigatus isolates from North America, Latin America or the Asia-Pacific region, we confirm an increase in the rate of NWT strains to all three triazoles among isolates from Europe.DisclosuresMariana Castanheira, PhD, 1928 Diagnostics (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support)Qpex Biopharma (Research Grant or Support) Cecilia G. Carvalhaes, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Pfizer (Research Grant or Support) Mary Motyl, PhD, Merck & Co, Inc (Employee, Shareholder) Seongah Han, PhD, Merck & Co, Inc. (Employee) Havilland Campbell, BS, Merck & Co, Inc. (Employee)

Pharmacokinetic/Pharmacodynamic Analysis the Probability of Target Attainment of Posaconazole against <i>Mucorales</i> Species in Patients with Mucormycosis

The objective of this study was to investigate the probability of target attainment of various posaconazole dosing regimens against Mucorales species in patients with mucormycosis. According to pharmacokinetic/pharmacodynamic parameters of posaconazole in adults, the dosage regimen of posaconazole for mucormycosis included 50, 100, 200 and 400 mg orally q12h. Monte Carlo Simulation analysed the published parameters of pharmacokinetics and the MIC values of mucormycosis in Mucorales species. The results showed that posaconazole did not affect Rhizopus arrhizus and Mucor sp. The optimal dosage of posaconazole for Rhizopus microsporus and Rhizomucor pusillus was 400 mg orally q12h and the best dosage regimen for Lichtheimia corymbifera was 200 mg orally q12h. The antifungal activity of posaconazole against mucormycosis was different, and the dosage regimen needs to adjust according to fungal species.

Screening the in vitro susceptibility of posaconazole in clinical isolates of Candida spp. and Aspergillus spp. and analyzing the sequence of ERG11 or CYP51A in non-wild-type isolates from China

The present study was to determine the in vitro activity of posaconazole (POS) against 385 Candida and 268 Aspergillus clinical isolates from China. We found that POS was active against 85.5% Candida and 94.4% Aspergillus isolates. Non–wild-type (non-WT) phenotype was found in a subset of Candida albicans (15.4%), Candida tropicalis (11.9%), Aspergillus fumigatus (4.1%), and Aspergillus flavus (17.4%) isolates. Cross-resistance to POS and other triazoles was seen. Gene sequencing showed that 4 C. albicans, 1 C. tropicalis, and 9 A. fumigatus isolates with cross-resistance to POS and other triazoles had mutations in ERG11 or CYP51A. In conclusion, POS has potent in vitro activity against most of Candida and Aspergillus isolates from China. Non-WT phenotype and those with cross-resistance to POS and other triazoles exist, frequently driven by mutations of ERG11 in Candida spp. and CYP51A in Aspergillus spp.

Voriconazole and posaconazole therapy for experimental Candida lusitaniae infection

The in vitro activity of posaconazole (PSC) and voriconazole (VRC) was tested by using time-kill studies against 3 strains of Candida lusitaniae. Both drugs showed fungistatic activity against all strains. The efficacy of those compounds was evaluated by reducing kidney fungal burden and by determining (1→3)-β-d-glucan serum levels in a murine model of invasive infection of C. lusitaniae. The therapies tested were VRC at 10, 25, or 40mg/kg/day and PSC at 5, 12.5, or 20mg/kg/twice a day. All the dosages showed efficacy in a dose-dependant manner being high doses of both antifungals able to sterilize some kidneys after 10days. With the exception of the strain FMR 9474, against which PSC was more effective than VRC, no differences in reducing tissue burden were found between the treatments. All doses of both antifungals were able to significantly reduce (1→3)-β-d-glucan serum levels with no significant differences between treatments and between the same doses of both drugs.

Etest cannot be recommended for in vitro susceptibility testing of mucorales.

Amphotericin B and posaconazole susceptibility patterns were determined for the most prevalent Mucorales, following EUCAST (European Committee on Antimicrobial Susceptibility Testing) broth microdilution guidelines. In parallel, Etest was performed and evaluated against EUCAST. The overall agreement of MICs gained with Etest and EUCAST was 75.1%; therefore, Etest cannot be recommended for antifungal susceptibility testing of Mucorales. Amphotericin B was the most active drug against Mucorales species in vitro, while the activities of posaconazole were more restricted.

Current status of in vitro and in vivo antifungal activities of posaconazole

Abstract Posaconazole (POS) is a new triazole drug with broad-spectrum in vitro activity against most yeasts and molds such as Candida, Cryptococcus neoformans, Aspergillus, Fusarium and Zygomycetes, as well as certain species of dimorphic fungi and endemic fungi. In immunocompetent or immunocompromised animal models with invasive fungal infections, POS has demonstrated highly effective, broad-spectrum antifungal activities. In vitro and in vivo antifungal activities of POS were superior to those of other azoles against Candida glabrata, Candida krusei, Aspergillus terrus, Fusarium and Zygomycetes. In vivo susceptibility studies have shown promising efficacy of POS against life-threatening fungal infections in animal models with different immune status and infection sites.

Mitochondrial respiratory pathways inhibition in Rhizopus oryzae potentiates activity of posaconazole and itraconazole via apoptosis.

The incidence of mucormycosis has increased drastically in immunocompromised patients. Also the array of targets whose inhibition results in Mucorales death is limited. Recently, researchers identified mitochondria as important regulators of detoxification and virulence mechanisms in fungi. In this context, targeting the mitochondrial respiratory chain may provide a new platform for antifungal development. We hypothesized that targeting respiratory pathways potentiates triazoles activity via apoptosis. We found that simultaneous administration of antimycin A (AA) and benzohydroxamate (BHAM), inhibitors of classical and alternative mitochondrial pathways respectively, resulted in potent activity of posaconazole (PCZ) and itraconazole (ICZ) against Rhizopus oryzae. We observed cellular changes characteristic of apoptosis in R. oryzae cells treated with PCZ or ICZ in combination with AA and BHAM. The fungicidal activity of this combination against R. oryzae was correlated with intracellular reactive oxygen species accumulation (ROS), phosphatidylserine externalization, mitochondrial membrane depolarization, and increased caspase like activity. DNA fragmentation and condensation assays also revealed apoptosis of R. oryzae cells. These apoptotic features were prevented by the addition of the ROS scavenger N-acetyl-cysteine. Taken together, these findings suggest that the use of PCZ or ICZ in combination with AA and BHAM makes R. oryzae exquisitely sensitive to treatment with triazoles via apoptosis. This strategy may serve as a new model for the development of improved or novel antifungal agents.

Effects of Obesity on Posaconazole Kinetics in a Patient with Graft versus Host Disease

Posaconazole, a triazole antifungal agent, displays a highly variable pharmacokinetic profile due in part to the oral solution, the only currently available dosage form. Posaconazole activity appears to be dose-dependent and clinical outcomes correlate with steady-state serum trough concentrations and area under the concentration curve (AUC) over minimum inhibitory concentration (MIC) ratios. Therapeutic drug monitoring (TDM) has been recommended to help overcome the unpredictable nature of the drug. The impact of obesity of posaconazole pharmacokinetics and the use of TDM in this population has not been well described; however, limited data demonstrate increased weight correlates with lower serum concentrations and reduced drug exposure. We describe the use of TDM in an obese man, 12 months status post hematopoietic stem-cell transplant (HSCT), receiving posaconazole therapy for a presumed invasive fungal infection (IFI).

Current status of in vitro and in vivo antifungal activities of posaconazole

Current status of in vitro and in vivo antifungal activities of posaconazole

Tacrolimus Enhances the Potency of Posaconazole Against Rhizopus oryzae In Vitro and in an Experimental Model of Mucormycosis

We hypothesized that tacrolimus, an inhibitor of the calcineurin pathway, would enhance the in vivo activity of posaconazole against Rhizopus oryzae, the Mucorales species most commonly associated with mucormycosis. We examined patterns of growth inhibition and fungicidal activity of posaconazole and tacrolimus, alone and in combination, against R. oryzae in vitro, using multiple methods (ie, hyphal metabolic and fluorescent vital dye reduction assays and measurement of chitin concentrations), and in vivo, using 2 mucormycosis models: an invertebrate model (Drosophila) and a nonlethal murine model of cutaneous mucormycosis. Combinations of posaconazole and tacrolimus were synergistic in checkerboard assays for 4 clinical isolates of R. oryzae (48-hour fractional inhibitory concentration index, 0.187-0.281). Pharmacodynamic analysis of the combination revealed that the 90% effective concentration threshold of posaconazole activity against R. oryzae could be achieved with 2-fold lower drug concentrations (0.5-1 mg/L) when administered with tacrolimus (0.007-2 mg/L). In vivo, combination therapy was associated with improved survival in the fly model of mucormycosis (65% vs 57% posaconazole alone) and with significant reductions in cutaneous lesions and R. oryzae fungal burden, compared with animals that received posaconazole monotherapy, in the cutaneous model of mucormycosis. Combination posaconazole-tacrolimus therapy displays synergism in vitro and improved antifungal efficacy in vivo in 2 phylogenetically distinct models of mucormycosis.

Efficacy of posaconazole in a murine model of disseminated infection caused by Apophysomyces variabilis

We evaluated the in vitro activity of posaconazole and amphotericin B against several clinical strains of the mucoralean fungus Apophysomyces variabilis, and their efficacy in a murine model of disseminated infection caused by that fungus. The in vitro susceptibility of seven strains of A. variabilis to posaconazole and amphotericin B was determined by using a broth microdilution method. The in vivo efficacy of both drugs, posaconazole at 20 mg/kg twice daily orally by gavage and amphotericin B at 0.8 mg/kg once daily intravenously, was evaluated against six of the strains previously tested in vitro using immunocompetent mice. In general, MICs of both drugs were within the range of susceptibility or intermediate susceptibility. Posaconazole and amphotericin B were able to significantly reduce the percentages of positive cultures in the affected tissues. However, in general, posaconazole significantly improved survival (median, 23 days; range, 7-30 days) compared with untreated controls (median, 6 days; range, 4-7 days) and, in some cases, with respect to the animals treated with amphotericin B (median, 15 days; range, 5-30 days). Our results demonstrate the efficacy of posaconazole in the treatment of a disseminated murine infection caused by A. variabilis. However, further clinical studies are required to ascertain the potential use in human infections caused by this fungus.

In Vitro and In Vivo Activities of Posaconazole and Amphotericin B in a Murine Invasive Infection by Mucor circinelloides: Poor Efficacy of Posaconazole

The in vitro susceptibility of 17 strains of Mucor circinelloides to amphotericin B and posaconazole was ascertained by using broth microdilution and disk diffusion methods and by determining the minimal fungicidal concentration (MFC). We evaluated the efficacy of posaconazole at 40 mg/kg of body weight/day and amphotericin B at 0.8 mg/kg/day in a neutropenic murine model of disseminated infection by M. circinelloides by using 6 different strains tested previously in vitro. In general, most of the posaconazole MICs were within the range of susceptibility or intermediate susceptibility, while the small inhibition zone diameters (IZDs) were indicative of nonsusceptibility for all isolates tested. The MFCs were ≥ 3 dilutions higher than the corresponding MICs. In contrast, amphotericin B showed good activity against all of the strains tested regardless of the method used. The in vivo studies demonstrated that amphotericin B was effective in prolonging survival and reducing the fungal load. Posaconazole showed poor in vivo efficacy with no correlation with the MIC values. The results suggested that posaconazole should be used with caution in the treatment of infections caused by Mucor circinelloides or by strains of Mucor not identified to the species level.

Posaconazole in Human Serum: a Greater Pharmacodynamic Effect than Predicted by the Non-Protein-Bound Serum Concentration

It is generally accepted that only the unbound fraction of a drug is pharmacologically active. Posaconazole is an antifungal agent with a protein binding of 98 to 99%. Taking into account the degree of protein binding, plasma levels in patients, and MIC levels of susceptible strains, it can be assumed that the free concentration of posaconazole sometimes will be too low to exert the expected antifungal effect. The aim was therefore to test the activity of posaconazole in serum in comparison with that of the calculated unbound concentrations in protein-free media. Significant differences (P < 0.05) from the serum control were found at serum concentrations of posaconazole of 1.0 and 0.10 mg/liter, with calculated free concentrations corresponding to 1× MIC and 0.1× MIC, respectively, against one Candida lusitaniae strain selected for proof of principle. In RPMI 1640, the corresponding calculated unbound concentration of 0.015 mg/liter resulted in a significant effect, whereas that of 0.0015 mg/liter did not. Also, against seven additional Candida strains tested, there was an effect of the low posaconazole concentration in serum, in contrast to the results in RPMI 1640. Fluconazole, a low-grade-protein-bound antifungal, was used for comparison at corresponding concentrations in serum and RPMI 1640. No effect was observed at the serum concentration, resulting in a calculated unbound concentration of 0.1× MIC. In summary, there was a substantially greater pharmacodynamic effect of posaconazole in human serum than could be predicted by the non-protein-bound serum concentration. A flux from serum protein-bound to fungal lanosterol 14α-demethylase-bound posaconazole is suggested.

Antifungal activity of posaconazole and granulocyte colony‐stimulating factor in the treatment of disseminated zygomycosis (mucormycosis) in a neutropaenic murine model

The aim of this study was to evaluate the pharmacokinetics and efficacy of posaconazole (PSC) in combination with granulocyte colony-stimulating factor (G-CSF) in a neutropaenic murine model of disseminated zygomycosis (mucormycosis) due to Rhizopus microsporus. Male BALB/c mice were rendered neutropaenic with cyclophosphamide (200 mg kg(-1), intraperitoneally) administered on days -1 and +5 postinfection. Mice were infected with R. microsporus (5 × 10(4) spores ml(-1)) intravenously. Mice were treated with PSC (40 mg kg(-1) day(-1) by gavage) or G-CSF (300 μg kg(-1) day(-1) subcutaneously) or with the combination of PSC and G-CSF. The fungal burden was assessed by culturing the brain, liver, kidneys and lungs. Blood levels of PSC were measured by high performance liquid chromatography. The survival rates were 33%, 27% and 31% for PSC-treated-, G-CSF-treated- and PSC + G-CSF-treated mice, respectively, as compared to 18% for the controls (P = NS). PSC monotherapy and combination therapy significantly reduced the fungal burden in the kidneys, but not in the rest of the organs. Combination therapy was not superior to PSC monotherapy in terms of either survival or reduction in fungal burden. Serum concentrations of PSC were well-above the MIC of PSC for the particular isolate. PSC monotherapy has a modest efficacy against R. microsporus in reducing fungal burden in neutropaenic mice. Combining G-CSF with PSC does not substantially affect the antifungal activity of PSC.