Activity of the new antifungal triazole, posaconazole, against Cryptococcus neoformans

Clinical safety and efficacy of a single-dose gentamicin, posaconazole and mometasone furoate otic suspension for treatment of canine otitis externa

BACKGROUND

A single-dose, in-clinic, veterinary professional-administered treatment for canine otitis externa was developed to improve compliance and canine welfare.

METHODS

This multicentre, controlled, examiner-masked, randomised field trial was conducted in 316 dogs over 42 days. Dogs were treated once, on day 0, with the investigational product containing gentamicin, posaconazole and mometasone furoate (Mometamax Ultra [MU]) or twice (days 0 and 7) with a control product containing florfenicol, terbinafine and betamethasone acetate (CP). The primary endpoint was a composite otitis index score of 4 or less (of 12) on day 14 and 3 or less (of 12) on day 28.

RESULTS

On day 28, treatment success was recorded in 128 of 143 MU-treated dogs (89.5%), significantly non-inferior to 116 of 133 (87.2%) CP-treated dogs (Farrington-Manning test, Z = 4.1351, p < 0.0001). For mixed cultures of Staphylococcus pseudintermedius and Malassezia pachydermatis, there was 100% treatment success in MU-treated dogs (n = 33), significantly non-inferior to 90.2% (37 of 41) in CP-treated dogs (Farrington-Manning test, Z = 3.1954, p = 0.0007).

LIMITATIONS

Efficacy in chronic otitis externa cases was not investigated. Cytology was not used to aid in diagnosis or for identification of secondary pathogens.

CONCLUSION

This unique combination, single-dose product is safe and effective in dogs with otitis externa. It offers enhanced compliance, canine welfare and quality of life by eliminating the owner burden of treating this painful condition.

A Prospective Study to Evaluate the Effect of Therapeutic Drug Monitoring-Based Posaconazole Prophylaxis on Invasive Fungal Infection Rate During Acute Myeloid Leukemia Induction Therapy

Invasive fungal infections (IFIs) are a significant cause of morbidity and mortality in de-novo acute myeloid leukemia patients receiving induction chemotherapy. Despite using posaconazole, a broad-spectrum antifungal, for IFI prophylaxis, the breakthrough IFI rate is high in the real-world setting. One of the reasons could be frequent suboptimal plasma posaconazole levels. In the present study, we evaluated if therapeutic drug monitoring (TDM) guided posaconazole prophylaxis can reduce the IFI rates in comparison to a historical cohort. We enrolled 90 patients, > / = 16 years of age, without baseline IFIs, planned for remission induction therapy. All patients were started on posaconazole suspension 200 mg TDS and the dose was increased in a stepwise manner if trough levels were found to be suboptimal (< 350 ng/ml for day 2 or < 700 ng/ml subsequently). The TDM based approach resulted in a significant decline in breakthrough IFI rates (18% versus 52%, P < 0.0001) A total of 69 patients (78%) required dose escalation. Thirty-one patients required change in antifungals due to either suboptimal levels, persistent fever, diarrhoea or vomiting. We could not demonstrate an exposure-response relationship but the difference in IFI rates in patients with a median posaconazole level > / = 700 ng/ml (0%) and < 700 ng/ml (21.6%) was clinically meaningful. Posaconazole levels were found to be significantly lower in patients on antacids and prokinetics. The incidence of posaconazole-related grade 3 toxicity was low (2.3%). Thus TDM-based dosing of posaconazole helps reduce breakthrough IFI rate and should be a part of posaconazole prophylaxis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12288-023-01709-3.

The Specific Binding and Promotion Effect of Azoles on Human Aldo-Keto Reductase 7A2

Human AKR 7A2 broadly participates in the metabolism of a number of exogenous and endogenous compounds. Azoles are a class of clinically widely used antifungal drugs, which are usually metabolized by CYP 3A4, CYP2C19, and CYP1A1, etc. in vivo. The azole-protein interactions that human AKR7A2 participates in remain unreported. In this study, we investigated the effect of the representative azoles (miconazole, econazole, ketoconazole, fluconazole, itraconazole, voriconazole, and posaconazole) on the catalysis of human AKR7A2. The steady-state kinetics study showed that the catalytic efficiency of AKR7A2 enhanced in a dose-dependent manner in the presence of posaconazole, miconazole, fluconazole, and itraconazole, while it had no change in the presence of econazole, ketoconazole, and voriconazole. Biacore assays demonstrated that all seven azoles were able to specifically bind to AKR7A2, among which itraconazole, posaconazole, and voriconazole showed the strongest binding. Blind docking predicted that all azoles were apt to preferentially bind at the entrance of the substrate cavity of AKR7A2. Flexible docking showed that posaconazole, located at the region, can efficiently lower the binding energy of the substrate 2-CBA in the cavity compared to the case of no posaconazole. This study demonstrates that human AKR7A2 can interact with some azole drugs, and it also reveals that the enzyme activity can be regulated by some small molecules. These findings will enable a better understanding of azole-protein interactions.

Efficacy, safety and feasibility of antifungal prophylaxis with posaconazole tablet in paediatric patients after haematopoietic stem cell transplantation

PURPOSE

Paediatric recipients of haematopoietic stem cell transplantation (HSCT) have a high risk for invasive fungal infections. Posaconazole oral suspension has proven to be effective in antifungal prophylaxis in adult and paediatric patients. A new posaconazole tablet formulation with absorption independent of the gastric conditions was approved by the FDA in 2013. This is the first report on the use of posaconazole tablets in paediatric patients.

METHODS

This single-centre study included 63 paediatric patients with haemato-oncological malignancies who received posaconazole for antifungal prophylaxis after HSCT. They were analysed for efficacy, feasibility and the safety of posaconazole. Out of 63 patients, 31 received posaconazole oral suspension and 32 received posaconazole tablets up to 200 days after transplantation. Analyses of the posaconazole trough levels were determined.

RESULTS

No possible, probable or proven invasive fungal infection was observed in either group. Posaconazole trough levels were significantly higher in the tablet group than in the suspension group at all analysed time points. Drug-related adverse events were similarly low in both groups.

CONCLUSIONS

Posaconazole tablets are effective in preventing invasive fungal infections in paediatric patients. As early as day 3 after starting posaconazole tablets, over 50% of the posaconazole trough levels were >500 ng/mL, while this was observed on day 14 after start with posaconazole suspension. The administration of posaconazole tablets was safe, effective and feasible as antifungal prophylaxis in paediatric patients after HSCT.

Sodium Lauryl Sulfate Competitively Interacts with HPMC-AS and Consequently Reduces Oral Bioavailability of Posaconazole/HPMC-AS Amorphous Solid Dispersion

Sodium lauryl sulfate (SLS), as an effective surfactant, is often used as a solubilizer and/or wetting agent in various dosage forms for the purpose of improving the solubility and dissolution of lipophilic, poorly water-soluble drugs. This study aims to understand the impact of SLS on the solution behavior and bioavailability of hypromellose acetate succinate (HPMC-AS)-based posaconazole (PSZ) ASDs, and to identify the underlying mechanisms governing the optimal oral bioavailability of ASDs when surfactants such as SLS are used in combination. Fluorescence spectroscopy and optical microscopy showed that "oil-out" or "liquid-liquid phase separation (LLPS)" occurred in the supersaturated PSZ solution once drug concentration surpassed ∼12 μg/mL, which caused the formation of drug-rich oily droplets with initial size of ∼300-400 nm. Although FT-IR study demonstrated the existence of specific interactions between PSZ and HPMC-AS in the solid state, predissolved HPMC-AS was unable to delay LLPS of the supersaturated PSZ solution and PSZ-rich amorphous precipitates with ∼16-18% HPMC-AS were formed within 10 min. The coprecipitated HPMC-AS was found to be able to significantly delay the crystallization of PSZ in the PSZ-rich amorphous phase from less than 10 min to more than 4 h, yet coexistent SLS was able to negate this crystallization inhibition effect of HPMC-AS in the PSZ-rich amorphous precipitates and cause fast PSZ crystallization within 30 min. 2D-NOESY and the CMC/CAC results demonstrated that SLS could assemble around HPMC-AS and competitively interact with HPMC-AS in the solution, thus prevent HPMC-AS from acting as an effective crystallization inhibitor. In a crossover dog PK study, this finding was found to be correlating well with the in vivo bioavailability of PSZ ASDs formulated with or without SLS. The SLS containing PSZ ASD formulation demonstrated an in vivo bioavailability ∼30% of that without SLS, despite the apparently better in vitro dissolution, which only compared the dissolved drug in solution, a small fraction of the total PSZ dose. We conclude that the bioavailability of ASDs is highly dependent on the molecular interactions between drug, surfactant, and polymer, not only in the solution phase but also in the drug-rich "oily" phase caused by supersaturation.

Posaconazole: An Update of Its Clinical Use

Posaconazole (PCZ) is a relatively new addition to the azole antifungals. It has fungicidal activities against Aspergillus fumigatus, Blastomyces dermatitidis, selected Candida species, Crytopcoccus neoformans, and Trichosporon. PCZ also has fungistatic activities against Candida, Coccidioides, selected Fusarium spp., Histoplasma, Scedosporium and Zygomycetes. In addition, combining the drug with caspofungin or amphotericin B results in a synergistic interaction against A. fumigatus, C. glabrata and C. neoformans. The absorption of PCZ suspension is enhanced when given with food, nutritional supplements, and carbonated beverages. Oral administration of PCZ in divided doses also increases its bioavailability. PCZ has a large volume of distribution and is highly protein bound (>95%). The main elimination route of PCZ is fecal. PCZ is an inhibitor of the CYP3A4 enzyme; therefore, monitoring for drug-drug interactions is warranted with other CYP3A4 substrates/inhibitors/inducers. The most common adverse effects include headache, fatigue, nausea, vomiting and elevated hepatic enzymes. PCZ, with its unique antifungal activities, expands the azole class of antifungal agents. Because of its limit in formulation, PCZ oral suspension is recommended in immunocompromised patients with functional gastrointestinaltracts who fail conventional antifungal therapies or who are suspected to have a breakthrough fungal infection. However, a delayed-release tablet formulation and intravenous (IV) injection became available in 2014, expanding the use of PCZ in other patient populations, including individuals who are unable to take oral formulations.

Posaconazole plasma concentration in pediatric patients receiving antifungal prophylaxis after allogeneic hematopoietic stem cell transplantation

Posaconazole has been proven to be effective for antifungal prophylaxis in adults after hematopoietic stem cell transplantation (HSCT). Due to low gastrointestinal resorption of posaconazole suspension, bioavailability is impaired. Fatty food improves the uptake of posaconazole, but insufficient data on the pharmacokinetics of posaconazole in pediatric patients are available so far. The single-center analysis investigated 161 posaconazole serum concentrations in 27 pediatric patients after HSCT receiving 12 mg·kg BW(-1)·d(-1) posaconazole suspension depending on age, gender, and intestinal graft-versus-host (iGvHD) disease, and the influence of posaconazole on cyclosporine A plasma concentrations. To improve the uptake of posaconazole, one patient cohort received higher fat nutrition with the drug administration. A comparison of the regular nutrition and higher-fat nutrition groups revealed the following values: 31 (27.4%) versus 8 (16.7%) < 500 ng/ml; 12 (10.6%) versus 7 (14.6%) 500-700 ng/ml; 8 (7.1%) versus 6 (12.5%) 700-1000 ng/ml; 51 (45.1%) versus 21 (43.8%) 1000-2000 ng/ml; and 11 (9.7%) versus 6 (12.5%) > 2000 ng/ml. The mean posaconazole concentrations in patients with regular nutrition was 1123 ± 811 ng/ml and with higher-fat nutrition was 1191 ± 673 ng/ml. Posaconazole levels in patients with iGvHD were significantly lower (P = 0.0003) than in patients without GvHD. The majority of samples showed a sufficient posaconazole concentration above 700 ng/ml. Posaconazole levels were slightly higher in patients with higher-fat nutrition and significantly lower in patients with iGvHD. Cyclosporine A levels were not significantly higher during posaconazole administration.

Clinical pharmacodynamics and pharmacokinetics of the antifungal extended-spectrum triazole posaconazole: an overview

In recent years, the antifungal triazole posaconazole has become increasingly important for the prophylaxis and treatment of systemic mycoses. Although oral bioavailability of posaconazole can be enhanced by concomitant food intake and administration in divided daily doses, increased gastric pH or gut motility, as well as enzyme-inducing drugs, can result in lower plasma concentrations than expected. Whether therapeutic drug monitoring can reduce the risk of treatment failures by avoiding sub-therapeutic plasma concentrations needs further examination. Based on the ability of posaconazole to inhibit cytochrome P450 3A4, several drug interactions can be expected, especially with agents that undergo extensive first-pass effect through the gut and the liver. However, more information is needed regarding dose modifications during concomitant administration of posaconazole with drugs in certain categories, such as vinca alkaloids and retinoids, along with selected individual drugs such as everolimus.

Antifungal therapy in a murine model of disseminated infection by Cryptococcus gattii

We have evaluated the efficacy of posaconazole (PSC), voriconazole (VRC), and amphotericin B (AMB) in a murine model of systemic infection by Cryptococcus gattii using immunocompromised animals and three clinical strains of the fungus. AMB was the most effective drug in prolonging the survival of mice and also in reducing tissue burden in all organs tested. To a lesser degree, VRC at 60 mg/kg of body weight in lung tissue and PSC at 40 mg/kg also in spleen demonstrated good efficacy in reducing the fungal load. The PSC and VRC levels in serum and brain tissue, determined by an agar diffusion bioassay method at 4 h after the last dose of the therapy, were above the corresponding MIC values. However, these drugs were not able to reduce the fungal load in brain tissue. Our results demonstrated that PSC and, to a lesser degree, VRC, have fungistatic activity and potential for the treatment of human pulmonary cryptococcosis.

Helicobacter pylori: prevalence and antibiotic susceptibility among Kenyans

BACKGROUND

Helicobacter pylori infection in Kenya is staggeringly high. Evidence links infection of the gastric mucosa by H. pylori with subsequent development of gastric pathologies.

AIM

We investigated the prevalence of H. pylori in dyspeptic patients, its relationship with gastric pathologies, and associated antibiotic susceptibility profiles, and compared two media to find the appropriate medium that enhances growth and expedites culture and isolation.

METHODS

Rapid urease and histological tests were used to screen for H. pylori. Culture was performed to test sensitivity and evaluate media. Selective and nutritional supplements were added to culture media (Colombia blood agar and brain-heart infusion agar) for growth enhancement. E-test strips for metronidazole, amoxicillin and clarithromycin were used for susceptibility testing.

RESULTS

The prevalence of H. pylori infection in children was 73.3%, and 54.8% in adults. All the H. pylori investigated in this study were largely sensitive to clarithromycin (100%, minimum inhibiting concentration (MIC) <2 microg/ml), amoxicillin (100%, MIC <2 microg/ml) and metronidazole (95.4%, MIC <8 microg/ml). There was, however, occasional resistance to metronidazole (4.6%, MIC >8 microg/ml). Both Colombia blood and brain-heart infusion agar, with the supplements, effectively supported H. pylori growth. Growth was achieved in an average of 36 hours for primary isolations and 24 hours for subcultures.

CONCLUSION

The media described here reduce the time required to culture and isolate bacteria and perform susceptibility testing. Despite the high prevalence of H. pylori infection, the associated pathology is low and does not parallel H. pylori prevalence in the population.

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.

Posaconazole: a next-generation triazole antifungal

Posaconazole is a new drug in the triazole class that has recently been investigated in pivotal Phase III clinical trials. Its antifungal activity is based on the inhibition of the fungal ergosterol synthesis. As demonstrated in vitro, posaconazole exhibits fungicidal activity against Aspergillus spp., Candida spp. and zygomycetes. Currently, posaconazole is only available as an oral suspension. Food consumption affects the bioavailability of posaconazole, while the exposure to posaconazole increases in a dose-proportional manner with a saturation of absorption occurring with a daily dose over 800 mg. Posaconazole is well tolerated without an increase in risk of any treatment-related adverse events during prolonged treatment for 6 or more months (n = 108). Posaconazole has been recently approved by the US FDA and other regulatory bodies for the treatment of oropharyngeal candidiasis, and the prophylaxis of invasive Aspergillus and Candida infections in severely immunocompromised patients. As demonstrated in two pivotal Phase III trials, posaconazole prophylaxis of invasive fungal infection in patients severely immunocompromised by graft-versus-host disease (n = 600) or neutropenia (n = 602) is superior to fluconazole and/or itraconazole prophylaxis. Significantly more patients who received posaconazole, instead of fluconazole, as treatment for oropharyngeal candidiasis sustained clinical success after the treatment was stopped. Preliminary data from a subgroup analysis (n = 24) of two salvage therapy trials for invasive fungal infections, as well as single case reports and series and in vitro studies, suggest that posaconazole might be an attractive oral treatment alternative for zygomycosis.

Posaconazole: a new broad-spectrum antifungal agent

The rising incidence of invasive fungal infections and the emergence of broader fungal resistance have led to the need for novel antifungal agents. Posaconazole is a new member of the triazole class of antifungals. It is available as an oral suspension and has a favorable toxicity profile, has demonstrated clinical efficacy in the treatment of oropharyngeal candidiasis and has shown promise as salvage therapy for invasive aspergillosis, zygomycosis, cryptococcal meningitis and a variety of other fungal infections. In addition, data from randomized controlled studies support its efficacy for use in prophylaxis of invasive fungal infections in patients who are severely immunocompromised. The wide spectrum activity of posaconazole in in vitro studies, animal models and preliminary clinical studies suggest that posaconazole represents an important addition to the antifungal armamentarium.

Drug interaction assessment following concomitant administration of posaconazole and phenytoin in healthy men

OBJECTIVE

Posaconazole is an extended-spectrum triazole antifungal agent for the treatment and prophylaxis of invasive fungal infections. This randomized, open-label, parallel-group, multiple-dose study was conducted in healthy adult volunteers to assess the potential for a drug interaction between phenytoin and the posaconazole tablet formulation.

METHODS

Subjects were randomly assigned for 10 days to one of the following treatments: posaconazole (200 mg once daily), phenytoin (200 mg once daily), or posaconazole (200 mg once daily) and phenytoin (200 mg once daily). Blood samples were collected on days 1 and 10 for pharmacokinetic evaluation of posaconazole and phenytoin concentrations.

RESULTS

A total of 36 healthy men enrolled in the study. On day 1, the maximum plasma concentration (C(max)) and area under the concentration-time curve calculated from time 0-24 h post-dose (AUC(0-24)) were unchanged upon co-administration. At steady state (day 10), co-administration of posaconazole with phenytoin resulted in 44% (p = 0.012) and 52% (p = 0.007) decreases in posaconazole C(max) and AUC(0-24), respectively. These decreases in exposure corresponded with a 90% increase in steady-state clearance of orally administered posaconazole. Phenytoin C(max) and AUC(0-24) were not significantly altered upon co-administration of the two agents, 24% increase in C(max) (p = 0.196) and 25% increase in AUC(0-24) (p = 0.212) values, although inter-subject variability was observed within this group.

CONCLUSION

Because co-administration of phenytoin and posaconazole significantly reduces posaconazole exposure and increases phenytoin levels in some subjects, concomitant use of these agents should be avoided unless the benefit outweighs the risk.

Antifungal efficacy and pharmacodynamics of posaconazole in experimental models of invasive fungal infections

Posaconazole is a novel lipophilic antifungal triazole with potent and broad-spectrum activity against opportunistic, endemic and dermatophytic fungi. This activity extends to organisms that are often refractory to existing triazoles, amphotericin B or echinocandins such as Candida glabrata, Candida krusei, Aspergillus terreus, Fusarium spp. and the Zygomycetes. A large number of experimental animal models of invasive fungal infections has demonstrated the potent and broad-spectrum efficacy of posaconazole in vivo, both in normal and in immunocompromised animals. Consistent with these preclinical data, posaconazole showed strong a antifungal efficacy in phase II and phase III clinical trials in immunocompromised patients with oropharyngeal and oesophageal candidiasis and as salvage therapy in patients with invasive fungal infections, and was effective as antifungal prophylaxis in high-risk patients. This paper reviews the preclinical disposition, antifungal efficacy and pharmacodynamics of posaconazole in and its implications for treatment and prevention of invasive fungal infections.

[The latest data on posaconazole]

Posaconazole is a lipophilic triazole antifungal agent that is structurally similar to itraconazole but has an expended spectrum of activity including yeast, molds, and dimorphic fungi. Posaconazole was licensed by the European Commission for the treatment of invasive aspergillosis, fusariosis, mycetoma, chromoblastomycosis, and coccidioidomycosis in adults who are refractory, or intolerant to other antifungal agents. Posaconazole was recently indicated for prophylaxis of invasive fungal infections in the following patients: patients receiving remission-induction chemotherapy for acute myelogenous leukemia (AML) or myelodysplastic syndromes (MDS) expected to result in prolonged neutropenia and hematopoietic stem cell transplant (HSCT) recipients who are undergoing high-dose immunosuppressive therapy for versus host disease. The spectacular activity of posaconazole against refractory infections due to zygomycetes is encouraging and suggests using posaconazole in this case. Posaconazole is only available in oral suspension formulation. Posaconazole was well tolerated in clinical trials and has lower drug interaction profile compared to other available azoles.

Posaconazole: clinical pharmacology and potential for management of fungal infections

Posaconazole is a novel lipophilic antifungal triazole that inhibits cytochrome P450-dependent 14-alpha demethylase in the biosynthetic pathway of ergosterol. Inhibition of this enzyme leads to an accumulation of toxic 14-alpha methylsterols and a depletion of ergosterol, resulting in a perturbation of the function of the fungal cell membrane and blockage of cell growth and division. In vitro, posaconazole has potent and broad-spectrum activity against opportunistic, endemic and dermatophytic fungi. This activity extends to organisms that are often refractory to existing triazoles, amphotericin B or echinocandins, such as Candida glabrata, Candida krusei, Aspergillus terreus, Fusarium spp. and the Zygomycetes. A large variety of animal models of invasive fungal infections have provided consistent evidence of efficacy against these organisms in vivo, both in normal and immunocompromised animals. Posaconazole is available as an oral suspension and optimal exposure is achieved when the drug is administered in two to four divided doses along with food or a nutritional supplement. The compound has a large volume of distribution, in the order of 5 l/kg, and a half-life of approximately 20 h. Posaconazole is not metabolized to a significant extent through the cytochrome P450 enzyme system and is primarily excreted in an unchanged form in the feces. Although it is inhibitory, cytochrome P3A4 has no effect on 1A2, 2C8, 2C9, 2D6 and 2E1 isoenzymes, and therefore, a limited spectrum of drug-drug interactions can be expected. Pharmacokinetic studies in special populations revealed no necessity for dosage adjustment based on differences in age, gender, race, renal or hepatic function. Posaconazole has demonstrated strong antifungal efficacy in Phase II and III clinical trials in immunocompromised patients with oropharyngeal and esophageal candidiasis. Posaconazole also showed promising efficacy as salvage therapy in a large Phase II study including 330 patients with invasive fungal infections intolerant to or refractory to standard therapies. Posaconazole appears to be well tolerated in a manner comparable with that of fluconazole and it is currently under regulatory review in the USA and Europe for the treatment of refractory invasive fungal infections. This drug profile reviews the preclinical and clinical pharmacology of posaconazole and its potential role for prevention and treatment of invasive fungal infections.

Posaconazole Oral Suspension

Each month, subscribers to The Formulary Monograph Service receive five to six well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to your Pharmacy and Therapeutics Committee. Subscribers also receive monthly one-page summary monographs on the agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation (DUE) is also provided each month. With a subscription, the monographs are sent to you in print and CD-ROM forms and are available online. Monographs can be customized to meet the needs of your facility. Subscribers to the The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X.). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X.

Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. If you would like information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The January 2007 monograph topics are telbivudine, budesonide/formoterol inhalation aerosol, ciclesonide nasal spray, eculizumab, ceftobiprole medocaril. The DUE is telbivudine.

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.

Antifungal activity of posaconazole compared with fluconazole and amphotericin B against yeasts from oropharyngeal candidiasis and other infections

OBJECTIVES

The in vitro antifungal activity of posaconazole was compared with that of fluconazole and amphotericin B.

MATERIALS AND METHODS

A microdilution method (M27-A2) was used with 331 clinical yeast isolates.

RESULTS

The geometric mean MICs of posaconazole, fluconazole and amphotericin B were 0.16, 0.91 and 0.15 mg/L, respectively. Posaconazole was markedly more active than fluconazole and was active against 9/11 fluconazole-resistant Candida albicans, and five Candida glabrata had an MIC of posaconazole of 16 mg/L.

CONCLUSIONS

These data indicate that posaconazole is a potentially effective antifungal agent for the treatment of mycoses caused by yeasts.

New agents for invasive mycoses in children

PURPOSE OF REVIEW

Invasive fungal infections are an important cause of morbidity and mortality in immunocompromised children of all ages. This review summarizes information on new antifungal agents, including current data on their clinical use in children, as well as alternative strategies such as antifungal combination and immunomodulation therapy.

RECENT FINDINGS

Novel antifungal agents, such as the echinocandins and the second-generation triazoles, were recently introduced that exhibit promising efficacy against Candida spp., Aspergillus spp., and other opportunistic fungal pathogens. These compounds are generally well tolerated and show substantial efficacy as salvage treatment and equal or even superior efficacy compared with older azoles or amphotericin B as first-line or empiric therapy for fungal infections. Clinical studies of pharmacokinetics and efficacy of the new agents in the pediatric population are, however, limited.

SUMMARY

The response rates observed with the recently introduced drugs, although superior in some cases compared with older antifungal agents, are still far from satisfactory. The development of new antifungal compounds as well as the use of alternative approaches of combination therapy and immunomodulation should be pursued through well-designed laboratory and clinical studies in pediatric patients.

In vitroactivities of posaconazole, ravuconazole, terbinafine, itraconazole and fluconazole against dermatophyte, yeast and non-dermatophyte species

The in vitro activities of two new triazole antifungal agents with broad-spectrum antifungal activity, posaconazole and ravuconazole, were compared with those of three well-established antifungal agents, terbinafine, itraconazole and fluconazole, against 184 clinical isolates. These included 129 dermatophyte isolates (twelve species), 25 yeast isolates (five species) and 28 non-dermatophyte isolates (nine species). In vitro testing was conducted using microdilution plates with RPMI 1640 and National Committee for Clinical Laboratory Standards (NCCLS) guidelines (M27-38P) were followed, except for the preparation of the dermatophyte inoculum. Both posaconazole and ravuconazole showed similar broad-spectrum activity against dermatophyte, yeast and non-dermatophyte species. Mean inhibitory concentrations (MIC) at which 90% [MIC90] of the isolates were inhibited by posaconazole and ravuconazole were 0.25 and 0.5 microg/ml for dermatophytes, 0.5 and 0.25 microg/ml for yeasts, and >4 and 8 microg/ml for non-dermatophytes. The MIC ranges against Trichophyton (six species), Microsporum (five species) and Epidermophyton flocossum were: posaconazole (0.007-1.0/0.007-0.25/0.007-1.0 microg/ml), ravuconazole (0.015-8.0/0.015-1.0/0.015-1.0 microg/ml), itraconazole (0.015- >8.0/0.015-0.5/ 0.015-8.0 microg/ml), fluconazole (0.125- >64.0/4.0 >64.0/0.5-64.0 microg/ml) and terbinafine (0.003 >2.0/0.007-2.0/0.007 >2.0 microg/ml). Overall ranking of the antifungal activity of the five antifungal agents was: terbinafine > posaconazole > ravuconazole > itraconazole > fluconazole, for dermatophytes; ravuconazole > posaconazole > itraconazole > fluconazole > terbinafine, against yeasts; and posaconazole > ravuconazole > terbinafine > itraconazole > fluconazole, for non-dermatophytes.

Efficacy of posaconazole in a murine model of central nervous system aspergillosis

Human central nervous system (CNS) aspergillosis has >90% mortality. We compared posaconazole with other antifungals for efficacy against murine CNS aspergillosis. All tested regimens of posaconazole were equivalent to those of amphotericin B and superior in prolonging survival and reducing CFU to those of itraconazole and caspofungin and to vehicle controls. No antifungal regimen effected cure. No toxicity was noted. Overall, posaconazole shows potential for treating CNS aspergillosis.

Disposition of posaconazole following single-dose oral administration in healthy subjects

Posaconazole is a potent, broad-spectrum triazole antifungal agent currently in clinical development for the treatment of refractory invasive fungal infections. Eight healthy male subjects received a single 399-mg (81.7 microCi) oral dose of [(14)C]posaconazole after consuming a high-fat breakfast. Urine, feces, and blood samples were collected for up to 336 h postdose and assayed for total radioactivity; plasma and urine samples were also assayed for parent drug. Posaconazole was orally bioavailable, with a median maximum posaconazole concentration in plasma achieved by 10 h postdose. Thereafter, posaconazole was slowly eliminated, with a mean half-life of 20 h. The greatest peak in the radioactivity profile of pooled plasma extracts was due to posaconazole, with smaller peaks due to a monoglucuronide, a diglucuronide, and a smaller fragment of the molecule. The mean total amount of radioactivity recovered was 91.1%; the cumulative excretion of radioactivity in feces and in urine was 76.9 and 14.0% of the dose, respectively. Most of the fecal radioactivity was associated with posaconazole, which accounted for 66.3% of the administered dose; however, urine contained only trace amounts of unchanged posaconazole. The radioactivity profile of pooled urine extracts included two monoglucuronide conjugates and a diglucuronide conjugate of posaconazole. These observations suggest that oxidative (phase 1) metabolism by cytochrome P450 isoforms represents only a minor route of elimination for posaconazole, and therefore cytochrome P450-mediated drug interactions should have a limited potential to impact posaconazole pharmacokinetics.

Pharmacokinetics of posaconazole coadministered with antacid in fasting or nonfasting healthy men

Posaconazole is a potent broad-spectrum azole antifungal agent in clinical development for the treatment of invasive fungal infections. This study evaluated the potential for a pH-dependent pharmacokinetic interaction between posaconazole and an antacid (Mylanta), under fasting and nonfasting conditions. Twelve men completed this randomized, four-period crossover, single-dose study. Subjects received 200 mg of posaconazole following a 10-h fast, with 20 ml of Mylanta and a 10-h fast, with 20 ml of Mylanta and a high-fat breakfast, and with a high-fat breakfast alone. Antacid coadministration had no statistically significant effects on posaconazole bioavailability under fasting or nonfasting conditions. In the fasting state, antacid slightly increased the relative oral bioavailability of posaconazole by 15% (P = 0.296); in the nonfasting state, antacid decreased the relative bioavailability of posaconazole by 12% (P = 0.352). Food increased the relative oral bioavailability of posaconazole by 400% (P = 0.001). In conclusion, the effect of antacid on posaconazole exposure in the fasting or nonfasting state was small and is not considered clinically significant.

Effect of food on the relative bioavailability of two oral formulations of posaconazole in healthy adults

AIMS

This randomized, crossover, single-dose study evaluated the relative oral bioavailability of posaconazole suspension and coprecipitate tablet formulations. Additionally, the study determined whether systemic exposure to posaconazole was affected by prandial status or by the fat content of a meal.

METHODS

This was a randomized, open-label, four-way crossover, single-dose study in 20 healthy men. Posaconazole pharmacokinetics were evaluated over 72 h following a single oral dose of posaconazole suspension (200 mg/5 ml) administered with a high-fat meal, a nonfat breakfast, or after a 10 h fast, or posaconazole tablets (2 x 100 mg) administered with a high-fat meal.

RESULTS

The posaconazole suspension showed a significant increase in bioavailability compared with the tablet (increase in AUC(0,72 h) = 137% (90% confidence interval (CI) 119%, 156% and Cmax = 123% (90% CI 104%, 146%). The mean increases in AUC(0,72 h) and Cmax values were about 400% when administered with a high-fat meal compared with administration of the suspension in the fasting state (AUC(0,72 h) 90% CI 343%, 448%; Cmax 90% CI 352%, 493%). Administration of the suspension with a nonfat meal enhanced exposure, resulting in an increase in AUC(0,72 h) of 264% (90% CI 231%, 302%) and in Cmax of 296% (90% CI 250%, 350%) relative to the fasted state.

CONCLUSIONS

The suspension formulation of posaconazole was associated with enhanced systemic exposure and increased relative bioavailability compared with the tablet. Food substantially enhanced the rate and extent of posaconazole absorption in healthy subjects.

IDENTIFICATION OF HUMAN UDP-GLUCURONOSYLTRANSFERASE ENZYME(S) RESPONSIBLE FOR THE GLUCURONIDATION OF POSACONAZOLE (NOXAFIL)

Posaconazole (Noxafil, SCH 56592), an orally available broad-spectrum triazole antifungal, is currently in phase III clinical studies for treating serious opportunistic fungal infections. The major in vitro metabolite of posaconazole formed by human liver microsomes supplemented with uridine 5'-diphosphate-glucuronic acid was a glucuronide of posaconazole (m/z877). Screening of 10 cDNA-expressed recombinant human UDP-glucuronosyltransferase (UGT) enzymes showed that only UGT1A4 exhibited catalytic activity with respect to the formation of the glucuronide of posaconazole. The formation of glucuronide by human liver microsomes and UGT1A4 was inhibited by bilirubin, a known inhibitor of UGT1A4. There was a high correlation (r =0.90) between the rate of formation of glucuronide, determined in 10 human liver microsomal samples, and trifluoperazine glucuronidation catalyzed by UGT1A4. These results confirmed that the formation of major posaconazole-glucuronide produced from human liver microsomes was mediated via UGT1A4.

Pharmacokinetics, safety, and tolerability of oral posaconazole administered in single and multiple doses in healthy adults

The pharmacokinetics, safety, and tolerability of posaconazole, an investigational triazole antifungal, were evaluated following the administration of rising single and multiple oral doses. A total of 103 healthy adults were enrolled in two phase I trials. Each study had a double-blind, placebo-controlled, parallel-group design with a rising single-dose (RSD) or rising multiple-dose (RMD) scheme. In the RSD study, subjects received single doses of posaconazole oral tablets (50 to 1200 mg) or placebo. In the RMD study, subjects received posaconazole oral tablets (50 to 400 mg) or placebo twice daily for 14 days. By using model-independent methods, the area under the plasma concentration-time curve and the maximum concentration in plasma were determined and used to assess dose proportionality. In the RSD study, the levels of posaconazole in plasma increased proportionally between the 50- and 800-mg dose range, with saturation of absorption occurring above 800 mg. Dose proportionality was also observed in the RMD study. In both studies, the apparent volume of distribution was large (range, 343 to 1341 liters) and the terminal-phase half-life was long (range, 25 to 31 h). Posaconazole was well tolerated at all dose levels, and the adverse events were not dose dependent. No clinically significant changes in clinical laboratory test values or electrocardiograms were observed. Following the administration of single and twice-daily rising doses, the level of posaconazole exposure increased in a dose-proportional manner. The long elimination-phase half-life of posaconazole supports once- or twice-daily dosing in clinical trials; however, additional studies are required to determine if further division of the dose will enhance exposure.

Laboratory evaluation of new antifungal agents against rare and refractory mycoses

PURPOSE OF REVIEW

An increase in refractory invasive fungal infections in the setting of marrow/solid organ transplantation and other immune-compromising clinical entities has provided the impetus for the development of new, more efficacious/less toxic antifungal agents. This review (1) examines currently available laboratory methods for the in-vitro evaluation of these new agents against both yeasts and filamentous fungi; (2) provides a summary of the most attractive investigational agents currently undergoing clinical trials/development; and (3) outlines the major refractory mycoses in contemporary medicine.

RECENT FINDINGS

Fluconazole-resistant Candida spp., Trichosporon spp., zygomycetous genera, the endemic mycoses, Scedosporium, Aspergillus, and Fusarium spp., and an ever-expanding list of lesser-known hyaline and phaeoid genera inciting invasive fungal infections comprise the bulk of refractory mycoses in the immune-compromised host. In-vitro data generated from reference-based antifungal susceptibility testing methods indicate an increased armamentarium of potentially efficacious agents against most of these mycoses.

SUMMARY

The newly approved antifungal agents caspofungin and voriconazole, used either as monotherapy or in combination regimens, have a significantly improved spectrum of activity over previously available therapeutic options. Correlation of clinical outcomes with investigational agents demonstrating in-vivo/in-vitro activity will provide critical information needed for the development of clinically significant minimum inhibitory concentration interpretative breakpoints.