Pharmacotherapeutic group: Antimycotics for systemic use, other antimycotics for systemic use. ATC code: JO2AX06
Mechanism of action
Anidulafungin is a semi-synthetic echinocandin, a lipopeptide synthesised from a fermentation product of Aspergillus nidulans.
Anidulafungin selectively inhibits 1,3-β-D glucan synthase, an enzyme present in fungal, but not mammalian cells. This results in inhibition of the formation of 1,3-β-D-glucan, an essential component of the fungal cell wall. Anidulafungin has shown fungicidal activity against Candida species and activity against regions of active cell growth of the hyphae of Aspergillus fumigatus.
Susceptibility testing breakpoints
MIC (minimum inhibitory concentration) interpretative criteria for susceptibility testing have been established by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for anidulafungin and are listed here: https://www.ema.europa.eu/documents/other/minimum-inhibitory-concentration-mic-breakpoints_en.xlsx
Activity in vitro
Anidulafungin exhibited in-vitro activity against C. albicans, C. glabrata, C. parapsilosis, C. krusei and C. tropicalis. For the clinical relevance of these findings see “Clinical efficacy and safety.”
Isolates with mutations in the hot spot regions of the target gene have been associated with clinical failures or breakthrough infections. Most clinical cases involve caspofungin treatment. However, in animal experiments these mutations confer cross resistance to all three echinocandins and therefore such isolates are classified as echinocandin resistant until further clinical experience are obtained concerning anidulafungin.
The in vitro activity of anidulafungin against Candida species is not uniform. Specifically, for C. parapsilosis, the MICs of anidulafungin are higher than are those of other Candida species.
Activity in vivo
Parenterally administered anidulafungin was effective against Candida species in immunocompetent and immunocompromised mouse and rabbit models. Anidulafungin treatment prolonged survival and also reduced the organ burden of Candida species, when determined at intervals from 24 to 96 hours after the last treatment.
Experimental infections included disseminated C. albicans infection in neutropenic rabbits, oesophageal/oropharyngeal infection of neutropenic rabbits with fluconazole-resistant C. albicans and disseminated infection of neutropenic mice with fluconazole-resistant C. glabrata.
Clinical efficacy and safety
Candidaemia and other forms of Invasive Candidiasis
The safety and efficacy of anidulafungin were evaluated in a pivotal Phase 3, randomised, double-blind, multicentre, multinational study of primarily non-neutropenic patients with candidaemia and a limited number of patients with deep tissue Candida infections or with abscess-forming disease. Patients with Candida endocarditis, osteomyelitis or meningitis, or those with infection due to C. krusei, were specifically excluded from the study. Patients were randomised to receive either anidulafungin (200 mg intravenous loading dose followed by 100 mg intravenous daily) or fluconazole (800 mg intravenous loading dose followed by 400 mg intravenous daily), and were stratified by APACHE II score (≤20 and >20) and the presence or absence of neutropenia. Treatment was administered for at least 14 and not more than 42 days. Patients in both study arms were permitted to switch to oral fluconazole after at least 10 days of intravenous therapy, provided that they were able to tolerate oral medicinal products and were afebrile for at least 24 hours, and that the most recent blood cultures were negative for Candida species.
Patients who received at least one dose of study medicinal products and who had a positive culture for Candida species from a normally sterile site before study entry were included in the modified intent-to-treat (MITT) population. In the primary efficacy analysis, global response in the MITT populations at the end of intravenous therapy, anidulafungin was compared to fluconazole in a pre-specified two-step statistical comparison (non-inferiority followed by superiority). A successful global response required clinical improvement and microbiological eradication. Patients were followed for six weeks beyond the end of all therapy.
Two hundred and fifty-six patients, ranging from 16 to 91 years in age, were randomised to treatment and received at least one dose of study medication. The most frequent species isolated at baseline were C. albicans (63.8% anidulafungin, 59.3% fluconazole), followed by C. glabrata (15.7%, 25.4%), C. parapsilosis (10.2%, 13.6%) and C. tropicalis (11.8%, 9.3%) - with 20, 13 and 15 isolates of the last 3 species, respectively, in the anidulafungin group. The majority of patients had Apache II scores ≤ 20 and very few were neutropenic.
Efficacy data, both overall and by various subgroups, are presented below in Table 2.
| Table 2. Global success in the MITT population: primary and secondary endpoints |
| | Anidulafungin | Fluconazole | Between group difference a (95% CI) |
| End of IV Therapy (1° endpoint) | 96/127 (75.6%) | 71/118 (60.2%) | 15.42 (3.9, 27.0) |
| Candidaemia only | 88/116 (75.9%) | 63/103 (61.2%) | 14.7 (2.5, 26.9) |
| Other sterile sitesb | 8/11 (72.7%) | 8/15 (53.3%) | - |
| Peritoneal fluid/IAc abscess | 6/8 | 5/8 | |
| Other | 2/3 | 3/7 | |
| C. albicansd | 60/74 (81.1%) | 38/61 (62.3%) | - |
| Non-albicans speciesd | 32/45 (71.1%) | 27/45 (60.0%) | - |
| Apache II score ≤ 20 | 82/101 (81.2%) | 60/98 (61.2%) | - |
| Apache II score > 20 | 14/26 (53.8%) | 11/20 (55.0%) | - |
| Non-neutropenic (ANC, cells/mm3 > 500) | 94/124 (75.8%) | 69/114 (60.5%) | - |
| Neutropenic (ANC, cells/mm3 ≤ 500) | 2/3 | 2/4 | - |
| At Other Endpoints | | | |
| End of All Therapy | 94/127 (74.0%) | 67/118 (56.8%) | 17.24 (2.9, 31.6)e |
| 2 Week Follow-up | 82/127 (64.6%) | 58/118 (49.2%) | 15.41 (0.4, 30.4)e |
| 6 Week Follow-up | 71/127 (55.9%) | 52/118 (44.1%) | 11.84 (-3.4, 27.0)e |
a Calculated as anidulafungin minus fluconazole
b With or without concurrent candidaemia
c Intra-abdominal
d Data presented for patients with a single baseline pathogen.
e 98.3% confidence intervals, adjusted post hoc for multiple comparisons of secondary time points.
Mortality rates in both the anidulafungin and fluconazole arms are presented below in Table 3:
| Table 3. Mortality |
| | Anidulafungin | Fluconazole |
| Overall study mortality | 29/127 (22.8%) | 37/118 (31.4%) |
| Mortality during study therapy | 10/127 (7.9%) | 17/118 (14.4%) |
| Mortality attributed to Candida infection | 2/127 (1.6%) | 5/118 (4.2%) |
Additional Data in Neutropenic Patients
The efficacy of anidulafungin (200 mg intravenous loading dose followed by 100 mg intravenous daily) in adult neutropenic patients (defined as absolute neutrophil count ≤ 500 cells/mm3, WBC ≤ 500 cells/mm3 or classified by the investigator as neutropenic at baseline) with microbiologically confirmed invasive candidiasis was assessed in an analysis of pooled data from 5 prospective studies (1 comparative versus caspofungin and 4 open-label, non-comparative). Patients were treated for at least 14 days. In clinically stable patients, a switch to oral azole therapy was permitted after at least 5 to 10 days of treatment with anidulafungin. A total of 46 patients were included in the analysis. The majority of patients had candidaemia only (84.8%; 39/46). The most common pathogens isolated at baseline were C. tropicalis (34.8%; 16/46), C. krusei (19.6%; 9/46), C. parapsilosis (17.4%; 8/46), C. albicans (15.2%; 7/46), and C. glabrata (15.2%; 7/46). The successful global response rate at End of Intravenous Treatment (primary endpoint) was 26/46 (56.5%) and End of All Treatment was 24/46 (52.2%). All-cause mortality up to the end of the study (6 Week Follow-up Visit) was 21/46 (45.7%).
The efficacy of anidulafungin in adult neutropenic patients (defined as absolute neutrophil count ≤ 500 cells/mm3 at baseline) with invasive candidiasis was assessed in a prospective, double-blind, randomized, controlled trial. Eligible patients received either anidulafungin (200 mg intravenous loading dose followed by 100 mg intravenous daily) or caspofungin (70 mg intravenous loading dose followed by 50 mg intravenous daily) (2:1 randomization). Patients were treated for at least 14 days. In clinically stable patients, a switch to oral azole therapy was permitted after at least 10 days of study treatment. A total of 14 neutropenic patients with microbiologically confirmed invasive candidiasis (MITT population) were enrolled in the study (11 anidulafungin; 3 caspofungin). The majority of patients had candidaemia only. The most common pathogens isolated at baseline were C. tropicalis (4 anidulafungin, 0 caspofungin), C. parapsilosis (2 anidulafungin, 1 caspofungin), C. krusei (2 anidulafungin, 1 caspofungin), and C. ciferrii (2 anidulafungin, 0 caspofungin). The successful global response rate at the End of Intravenous Treatment (primary endpoint) was 8/11 (72.7%) for anidulafungin and 3/3 (100.0%) for caspofungin (difference -27.3, 95% CI -80.9, 40.3); the successful global response rate at the End of All Treatment was 8/11 (72.7%) for anidulafungin and 3/3 (100.0%) for caspofungin (difference -27.3, 95% CI -80.9, 40.3). All-cause mortality up to the 6 Week Follow-Up visit for anidulafungin (MITT population) was 4/11 (36.4%) and 2/3 (66.7%) for caspofungin.
Patients with microbiologically confirmed invasive candidiasis (MITT population) and neutropenia were identified in an analysis of pooled data from 4 similarly designed prospective, open-label, non-comparative studies. The efficacy of anidulafungin (200 mg intravenous loading dose followed by 100 mg intravenous daily) was assessed in 35 adult neutropenic patients defined as absolute neutrophil count ≤ 500 cells/mm3 or WBC ≤ 500 cells/mm3 in 22 patients or classified by the investigator as neutropenic at baseline in 13 patients. All patients were treated for at least 14 days. In clinically stable patients, a switch to oral azole therapy was permitted after at least 5 to 10 days of treatment with anidulafungin. The majority of patients had candidaemia only (85.7%). The most common pathogens isolated at baseline were C. tropicalis (12 patients), C. albicans (7 patients), C. glabrata (7 patients), C. krusei (7 patients), and C. parapsilosis (6 patients). The successful global response rate at the End of Intravenous Treatment (primary endpoint) was 18/35 (51.4%) and 16/35 (45.7%) at the End of All Treatment. All-cause mortality by Day 28 was 10/35 (28.6%). The successful global response rate at End of Intravenous Treatment and End of All Treatment were both 7/13 (53.8%) in the 13 patients with neutropenia assessed by investigators at baseline.
Additional Data in Patients with Deep Tissue Infections
The efficacy of anidulafungin (200 mg intravenous loading dose followed by 100 mg intravenous daily) in adult patients with microbiologically confirmed deep tissue candidiasis was assessed in an analysis of pooled data from 5 prospective studies (1 comparative and 4 open-label). Patients were treated for at least 14 days. In the 4 open-label studies, a switch to oral azole therapy was permitted after at least 5 to 10 days of treatment with anidulafungin. A total of 129 patients were included in the analysis. Twenty-one (16.3%) had concomitant candidaemia. The mean APACHE II score was 14.9 (range, 2 – 44). The most common sites of infection included the peritoneal cavity (54.3%; 70 of 129), hepatobiliary tract (7.0%; 9 of 129), pleural cavity (5.4%; 7 of 129) and kidney (3.1%; 4 of 129). The most common pathogens isolated from a deep tissue site at baseline were C. albicans (64.3%; 83 of 129), C. glabrata (31.0%; 40 of 129), C. tropicalis (11.6%; 15 of 129), and C. krusei (5.4%; 7 of 129). The successful global response rate at the end of intravenous treatment (primary endpoint) and End of all treatment and all-cause mortality up to the 6 week follow-up visit is shown in Table 4.
| Table 4. Rate of Successful Global Responsea and All-Cause Mortality in Patients with Deep Tissue Candidiasis – Pooled Analysis |
| | MITT Population n/N (%) |
| Global Response of Success at EOIVTb | |
| Overall | 102/129 (79.1) |
| Peritoneal cavity | 51/70 (72.9) |
| Hepatobiliary tract | 7/9 (77.8) |
| Pleural cavity | 6/7 (85.7) |
| Kidney | 3/4 (75.0) |
| Global Response of Success at EOTb | 94/129 (72.9) |
| All-Cause Mortality | 40/129 (31.0) |
| a A successful global response was defined as both clinical and microbiologic success b EOIVT, End of Intravenous Treatment; EOT, End of All Treatment |
Paediatric population
A prospective, open-label, non-comparative, multi-national study assessed the safety and efficacy of anidulafungin in 68 paediatric patients aged 1 month to < 18 years with ICC. Patients were stratified by age (1 month to < 2 years, 2 to < 5 years, and 5 to < 18 years) and received once daily intravenous anidulafungin (3.0 mg/kg loading dose on Day 1, and 1.5 mg/kg daily maintenance dose thereafter) for up to 35 days followed by an optional switch to oral fluconazole (6-12 mg/kg/day, maximum 800 mg/day). Patients were followed at 2 and 6 weeks after EOT.
Among 68 patients who received anidulafungin, 64 had microbiologically confirmed Candida infection and were evaluated for efficacy in the modified intent-to-treat (MITT) population. Overall, 61 patients (92.2%) had Candida isolated from blood only. The most commonly isolated pathogens were Candida albicans (25 [39.1%] patients), followed by Candida parapsilosis (17 [26.6%] patients), and Candida tropicalis (9 [14.1%] patients). A successful global response was defined as having both a clinical response of success (cure or improvement) and a microbiological response of success (eradication or presumed eradication). The overall rates of successful global response in the MITT population are presented in Table 5.
| Table 5. Summary of Successful Global Response by Age Group, MITT Population |
| | Successful Global Response, n (%) |
| Timepoint | Global Response | 1 month to < 2 years (N=16) n (n/N, %) | 2 to < 5 years (N=18) n (n/N, %) | 5 to < 18 years (N=30) n (n/N, %) | Overall (N=64) n (n/N, %) |
| EOIVT | Success | 11 (68.8) | 14 (77.8) | 20 (66.7) | 45 (70.3) |
| 95% CI | (41.3, 89.0) | (52.4, 93.6) | (47.2, 82.7) | (57.6, 81.1) |
| EOT | Success | 11 (68.8) | 14 (77.8) | 21 (70.0) | 46 (71.9) |
| 95% CI | (41.3, 89.0) | (52.4, 93.6) | (50.6, 85.3) | (59.2, 82.4) |
| 2-week FU | Success | 11 (68.8) | 13 (72.2) | 22 (73.3) | 46 (71.9) |
| 95% CI | (41.3, 89.0) | (46.5, 90.3) | (54.1, 87.7) | (59.2, 82.4) |
| 6-week FU | Success | 11 (68.8) | 12 (66.7) | 20 (66.7) | 43 (67.2) |
| 95% CI | (41.3, 89.0) | (41.0, 86.7) | (47.2, 82.7) | (54.3, 78.4) |
| 95% CI = exact 95% confidence interval for binomial proportions using Clopper-Pearson method; EOIVT = End of Intravenous Treatment; EOT = End of All Treatment; FU = follow-up; MITT = modified intent-to-treat; N = number of subjects in the population; n = number of subjects with responses |