Pharmacotherapeutic group: Antimycotics for systemic use, triazole derivatives, ATC code: J02A C03
Mode of action
Voriconazole is a triazole antifungal agent. The primary mode of action of voriconazole is the inhibition of fungal cytochrome P450-mediated 14 alpha-lanosterol demethylation, an essential step in fungal ergosterol biosynthesis. The accumulation of 14 alpha-methyl sterols correlates with the subsequent loss of ergosterol in the fungal cell membrane and may be responsible for the antifungal activity of voriconazole. Voriconazole has been shown to be more selective for fungal cytochrome P-450 enzymes than for various mammalian cytochrome P-450 enzyme systems.
Pharmacokinetic/pharmacodynamic relationship
In 10 therapeutic studies, the median for the average and maximum plasma concentrations in individual subjects across the studies was 2425 ng/ml (inter-quartile range 1193 to 4380 ng/ml) and 3742 ng/ml (inter-quartile range 2027 to 6302 ng/ml), respectively. A positive association between mean, maximum or minimum plasma voriconazole concentration and efficacy in therapeutic studies was not found and this relationship has not been explored in prophylaxis studies.
Pharmacokinetic-Pharmacodynamic analyses of clinical trial data identified positive associations between plasma voriconazole concentrations and both liver function test abnormalities and visual disturbances. Dose adjustments in prophylaxis studies have not been explored.
Clinical efficacy and safety
In vitro, voriconazole displays broad-spectrum antifungal activity with antifungal potency against Candida species (including fluconazole -resistant C. krusei and resistant strains of C. glabrata and C. albicans) and fungicidal activity against all Aspergillus species tested. In addition voriconazole shows in vitro fungicidal activity against emerging fungal pathogens, including those such as Scedosporium or Fusarium which have limited susceptibility to existing antifungal agents.
Clinical efficacy defined as partial or complete response, has been demonstrated for Aspergillus spp. including A. flavus, A. fumigatus, A. terreus, A. niger, A. nidulans; Candida spp., including C. albicans, C. glabrata, C. krusei, C. parapsilosis and C. tropicalis; and limited numbers of C. dubliniensis, C. inconspicua, and C. guilliermondii, Scedosporium spp., including S. apiospermum, S. prolificans; and Fusarium spp.
Other treated fungal infections (often with either partial or complete response) included isolated cases of Alternaria spp., Blastomyces dermatitidis, Blastoschizomyces capitatus, Cladosporium spp., Coccidioides immitis, Conidiobolus coronatus, Cryptococcus neoformans, Exserohilum rostratum, Exophiala spinifera, Fonsecaea pedrosoi, Madurella mycetomatis, Paecilomyces lilacinus, Penicillium spp. including P. marneffei, Phialophora richardsiae, Scopulariopsis brevicaulis and Trichosporon spp. including T. beigelii infections.
In vitro activity against clinical isolates has been observed for Acremonium spp., Alternaria spp., Bipolaris spp., Cladophialophora spp., and Histoplasma capsulatum, with most strains being inhibited by concentrations of voriconazole in the range 0.05 to 2 µg/ml.
In vitro activity against the following pathogens has been shown, but the clinical significance is unknown: Curvularia spp. and Sporothrix spp.
Breakpoints
Specimens for fungal culture and other relevant laboratory studies (serology, histopathology) should be obtained prior to therapy to isolate and identify causative organisms. Therapy may be instituted before the results of the cultures and other laboratory studies are known; however, once these results become available, anti-infective therapy should be adjusted accordingly.
The species most frequently involved in causing human infections include C. albicans, C. parapsilosis, C. tropicalis, C. glabrata and C. krusei, all of which usually exhibit minimal inhibitory concentration (MICs) of less than 1 mg/L for voriconazole.
However, the in vitro activity of voriconazole against Candida species is not uniform. Specifically, for C. glabrata, the MICs of voriconazole for fluconazole-resistant isolates are proportionally higher than are those of fluconazole-susceptible isolates. Therefore, every attempt should be made to identify Candida to species level. If antifungal susceptibility testing is available, the MIC results may be interpreted using breakpoint criteria established by European Committee on Antimicrobial Susceptibility Testing (EUCAST).
EUCAST Breakpoints
| Candida and Aspergillus species | Minimal Inhibitory Concentration (MIC) breakpoint (mg/L) |
| ≤S (Susceptible) | >R (Resistant) |
| Candida albicans1 | 0.06 | 0.25 |
| Candida dubliniensis1 | 0.06 | 0.25 |
| Candida glabrata | Insufficient evidence (IE) | IE |
| Candida krusei | IE | IE |
| Candida parapsilosis1 | 0.125 | 0.25 |
| Candida tropicalis1 | 0.125 | 0.25 |
| Candida guilliermondii2 | IE | IE |
| Non-species related breakpoints for Candida3 | IE | IE |
| Aspergillus fumigatus4 | 1 | 1 |
| Aspergillus nidulans4 | 1 | 1 |
| Aspergillus flavus | IE5 | IE5 |
| Aspergillus niger | IE5 | IE5 |
| Aspergillus terreus | IE5 | IE5 |
| Non-species related breakpoints6 | IE | IE |
| 1 Strains with MIC values above the Susceptible/Intermediate (S/I) breakpoint are rare or not yet reported. The identification and antifungal susceptibility tests on any such isolate must be repeated and if the result is confirmed the isolate sent to a reference laboratory. Until there is evidence regarding clinical response for confirmed isolates with MIC above the current resistant breakpoint they should be reported resistant. A clinical response of 76% was achieved in infections caused by the species listed below when MICs were lower than or equal to the epidemiological cut-offs. Therefore, wild type populations of C. albicans, C. dubliniensis, C. parapsilosis and C. tropicalis are considered susceptible. 2 The epidemiological cut-off values (ECOFFs) for these species are in general higher than for C. albicans. 3 Non-species related breakpoints have been determined mainly on the basis of PK/PD data and are independent of MIC distributions of specific Candida species. They are for use only for organisms that do not have specific breakpoints. 4 Area of technical uncertainty (ATU) is 2. Report as R with the following comment: "In some clinical situations (non-invasive infections forms) voriconazole can be used provided sufficient exposure is ensured". 5 The ECOFFs for these species are in general one two-fold dilution higher than for A. fumigatus. 6 Non-species related breakpoints have not been determined. |
Clinical experience
Successful outcome in this section is defined as complete or partial response.
Aspergillus infections – efficacy in aspergillosis patients with poor prognosis
Voriconazole has in vitro fungicidal activity against Aspergillus spp. The efficacy and survival benefit of voriconazole versus conventional amphotericin B in the primary treatment of acute invasive aspergillosis was demonstrated in an open, randomised, multicentre study in 277 immunocompromised patients treated for 12 weeks. Voriconazole was administered intravenously with a loading dose of 6 mg/kg every 12 hours for the first 24 hours followed by a maintenance dose of 4 mg/kg every 12 hours for a minimum of 7 days. Therapy could then be switched to the oral formulation at a dose of 200 mg every 12 hours. Median duration of IV voriconazole therapy was 10 days (range 2-85 days). After IV voriconazole therapy, the median duration of oral voriconazole therapy was 76 days (range 2-232 days).
A satisfactory global response (complete or partial resolution of all attributable symptoms, signs, radiographic/bronchoscopic abnormalities present at baseline) was seen in 53% of voriconazole-treated patients compared to 31% of patients treated with comparator. The 84-day survival rate for voriconazole was statistically significantly higher than that for the comparator and a clinically and statistically significant benefit was shown in favour of voriconazole for both time to death and time to discontinuation due to toxicity.
This study confirmed findings from an earlier, prospectively designed study where there was a positive outcome in subjects with risk factors for a poor prognosis, including graft versus host disease, and, in particular, cerebral infections (normally associated with almost 100% mortality).
The studies included cerebral, sinus, pulmonary and disseminated aspergillosis in patients with bone marrow and solid organ transplants, haematological malignancies, cancer and AIDS.
Candidaemia in non-neutropenic patients
The efficacy of voriconazole compared to the regimen of amphotericin B followed by fluconazole in the primary treatment of candidaemia was demonstrated in an open, comparative study. Three hundred and seventy non-neutropenic patients (above 12 years of age) with documented candidaemia were included in the study, of whom 248 were treated with voriconazole. Nine subjects in the voriconazole group and 5 in the amphotericin B followed by fluconazole group also had mycologically proven infection in deep tissue. Patients with renal failure were excluded from this study. The median treatment duration was 15 days in both treatment arms. In the primary analysis, successful response as assessed by a Data Review Committee (DRC) blinded to study medicinal product was defined as resolution/improvement in all clinical signs and symptoms of infection with eradication of Candida from blood and infected deep tissue sites 12 weeks after the end of therapy (EOT). Patients who did not have an assessment 12 weeks after EOT were counted as failures. In this analysis a successful response was seen in 41% of patients in both treatment arms.
In a secondary analysis, which utilised DRC assessments at the latest evaluable time point (EOT, or 2, 6, or 12 weeks after EOT) voriconazole and the regimen of amphotericin B followed by fluconazole had successful response rates of 65% and 71%, respectively.
The Investigator's assessment of successful outcome at each of these time points is shown in the following table.
| Timepoint | Voriconazole (N=248) | Amphotericin B → fluconazole (N=122) |
| EOT | 178 (72%) | 88 (72%) |
| 2 weeks after EOT | 125 (50%) | 62 (51%) |
| 6 weeks after EOT | 104 (42%) | 55 (45%) |
| 12 weeks after EOT | 104 (42%) | 51 (42%) |
Serious refractory Candida infections
The study comprised 55 patients with serious refractory systemic Candida infections (including candidaemia, disseminated and other invasive candidiasis) where prior antifungal treatment, particularly with fluconazole, had been ineffective. Successful response was seen in 24 patients (15 complete, 9 partial responses). In fluconazole-resistant non-albicans species, a successful outcome was seen in 3/3 C. krusei (complete responses) and 6/8 C. glabrata (5 complete, 1 partial response) infections. The clinical efficacy data were supported by limited susceptibility data.
Scedosporium and Fusarium infections
Voriconazole was shown to be effective against the following rare fungal pathogens:
Scedosporium spp.: Successful response to voriconazole therapy was seen in 16 (6 complete, 10 partial responses) of 28 patients with S. apiospermum and in 2 (both partial responses) of 7 patients with S. prolificans infection. In addition, a successful response was seen in 1 of 3 patients with infections caused by more than one organism including Scedosporium spp.
Fusarium spp.: Seven (3 complete, 4 partial responses) of 17 patients were successfully treated with voriconazole. Of these 7 patients, 3 had eye, 1 had sinus, and 3 had disseminated infection. Four additional patients with fusariosis had an infection caused by several organisms; 2 of them had a successful outcome.
The majority of patients receiving voriconazole treatment of the above mentioned rare infections were intolerant of, or refractory to, prior antifungal therapy.
Primary Prophylaxis of Invasive Fungal Infections – Efficacy in HSCT recipients without prior proven or probable IFI
Voriconazole was compared to itraconazole as primary prophylaxis in an open-label, comparative, multicenter study of adult and adolescent allogeneic HSCT recipients without prior proven or probable IFI. Success was defined as the ability to continue study drug prophylaxis for 100 days after HSCT (without stopping for >14 days) and survival with no proven or probable IFI for 180 days after HSCT. The modified intent-to-treat (MITT) group included 465 allogeneic HSCT recipients with 45% of patients having AML. From all patients 58% were subject to myeloablative conditions regimens. Prophylaxis with study drug was started immediately after HSCT: 224 received voriconazole and 241 received itraconazole. The median duration of study drug prophylaxis was 96 days for voriconazole and 68 days for itraconazole in the MITT group.
Success rates and other secondary endpoints are presented in the table below:
| Study Endpoints | VoriconazoleN=224 | ItraconazoleN=241 | Difference in proportions and the 95% confidence interval (CI) | P-Value |
| Success at day 180* | 109 (48.7%) | 80 (33.2%) | 16.4% (7.7%, 25.1%)** | 0.0002** |
| Success at day 100 | 121 (54.0%) | 96 (39.8%) | 15.4% (6.6%, 24.2%)** | 0.0006** |
| Completed at least 100 days of study drug prophylaxis | 120 (53.6%) | 94 (39.0%) | 14.6% (5.6%, 23.5%) | 0.0015 |
| Survived to day 180 | 184 (82.1%) | 197 (81.7%) | 0.4% (-6.6%, 7.4%) | 0.9107 |
| Developed proven or probable IFI to day 180 | 3 (1.3%) | 5 (2.1%) | -0.7% (-3.1%, 1.6%) | 0.5390 |
| Developed proven or probable IFI to day 100 | 2 (0.9%) | 4 (1.7%) | -0.8% (-2.8%, 1.3%) | 0.4589 |
| Developed proven or probable IFI while on study drug | 0 | 3 (1.2%) | -1.2% (-2.6%, 0.2%) | 0.0813 |
* Primary endpoint of the study
** Difference in proportions, 95% CI and p-values obtained after adjustment for randomization
The breakthrough IFI rate to Day 180 and the primary endpoint of the study, which is Success at Day 180, for patients with AML and myeloablative conditioning regimens respectively, is presented in the table below:
AML
| Study endpoints | Voriconazole (N=98) | Itraconazole (N=109) | Difference in proportions and the 95% confidence interval (CI) |
| Breakthrough IFI – Day 180 | 1 (1.0%) | 2 (1.8%) | -0.8% (-4.0%, 2.4%)** |
| Success at Day 180* | 55 (56.1%) | 45 (41.3%) | 14.7% (1.7%, 27.7%)*** |
* Primary endpoint of study
** Using a margin of 5%, non inferiority is demonstrated
***Difference in proportions, 95% CI obtained after adjustment for randomization
Myeloablative conditioning regimens
| Study endpoints | Voriconazole (N=125) | Itraconazole (N=143) | Difference in proportions and the 95% confidence interval (CI) |
| Breakthrough IFI – Day 180 | 2 (1.6%) | 3 (2.1%) | -0.5% (-3.7%, 2.7%)** |
| Success at Day 180* | 70 (56.0%) | 53 (37.1%) | 20.1% (8.5%, 31.7%)*** |
* Primary endpoint of study
** Using a margin of 5%, non inferiority is demonstrated
*** Difference in proportions, 95% CI obtained after adjustment for randomization
Secondary Prophylaxis of IFI – Efficacy in HSCT recipients with prior proven or probable IFI
Voriconazole was investigated as secondary prophylaxis in an open-label, non-comparative, multicenter study of adult allogeneic HSCT recipients with prior proven or probable IFI. The primary endpoint was the rate of occurrence of proven and probable IFI during the first year after HSCT. The MITT group included 40 patients with prior IFI, including 31 with aspergillosis, 5 with candidiasis, and 4 with other IFI. The median duration of study drug prophylaxis was 95.5 days in the MITT group.
Proven or probable IFIs developed in 7.5% (3/40) of patients during the first year after HSCT, including one candidemia, one scedosporiosis (both relapses of prior IFI), and one zygomycosis. The survival rate at Day 180 was 80.0% (32/40) and at 1 year was 70.0% (28/40).
Duration of treatment
In clinical trials, 705 patients received voriconazole therapy for greater than 12 weeks, with 164 patients receiving voriconazole for over 6 months.
Paediatric population
Fifty-three paediatric patients aged 2 to <18 years were treated with voriconazole in two prospective, open-label, non-comparative, multi-center clinical trials. One study enrolled 31 patients with possible, proven or probable invasive aspergillosis (IA), of whom 14 patients had proven or probable IA and were included in the MITT efficacy analyses. The second study enrolled 22 patients with invasive candidiasis including candidaemia (ICC), and esophageal candidiasis (EC) requiring either primary or salvage therapy, of whom 17 were included in the MITT efficacy analyses. For patients with IA the overall rates of global response at 6 weeks were 64.3% (9/14), the global response rate was 40% (2/5) for patients 2 to <12 years and 77.8% (7/9) for patients 12 to <18 years of age. For patients with ICC the global response rate at EOT was 85.7% (6/7) and for patients with EC the global response rate at EOT was 70% (7/10). The overall rate of response (ICC and EC combined) was 88.9% (8/9) for 2 to <12 years old and 62.5% (5/8) for 12 to <18 years old.
Clinical studies examining QTc interval
A placebo-controlled, randomized, single-dose, crossover study to evaluate the effect on the QTc interval of healthy volunteers was conducted with three oral doses of voriconazole and ketoconazole. The placebo-adjusted mean maximum increases in QTc from baseline after 800, 1200 and 1600 mg of voriconazole were 5.1, 4.8, and 8.2 msec, respectively and 7.0 msec for ketoconazole 800 mg. No subject in any group had an increase in QTc of ≥ 60 msec from baseline. No subject experienced an interval exceeding the potentially clinically-relevant threshold of 500 msec.