Pharmacotherapeutic group: Antimycotics for systemic use, other antimycotics for systemic use, ATC code: J02AX05
Mechanism of action
Micafungin non-competitively inhibits the synthesis of 1,3-β-D-glucan, an essential component of the fungal cell wall. 1,3-β-D-glucan is not present in mammalian cells.
Micafungin exhibits fungicidal activity against most Candida species and prominently inhibits actively growing hyphae of Aspergillus species.
PK/PD relationship
In animals models of candidiasis, a correlation was observed between exposure of micafungin divided by MIC (AUC/MIC) and efficacy defined as the ratio required to prevent progressive fungal growth. A ratio of ~2400 and ~1300 was required for C. albicans and C. glabrata, respectively, in these models. At the recommended therapeutic dosage of Micafungin, these ratios are achievable for the wild-type distribution of Candida spp.
Mechanism(s) of resistance
As for all antimicrobial agents, cases of reduced susceptibility and resistance have been reported and cross-resistance with other echinocandins cannot be excluded. Reduced susceptibility to echinocandins has been associated with mutations in the Fks1 and Fks2 genes coding for a major subunit of glucan synthase.
Breakpoints
EUCAST breakpoints
| Candida species | MIC breakpoint (mg/L) |
| ≤ S (Susceptible) | > R (Resistant) |
| Candida albicans | 0.016 | 0.016 |
| Candida glabrata | 0.03 | 0.03 |
| Candida parapsilosis | 0.002 | 2 |
| Candida tropicalis1 | Insufficient evidence |
| Candida krusei1 | Insufficient evidence |
| Candida guilliermondii1 | Insufficient evidence |
| Other Candida spp. | Insufficient evidence |
| 1 MICs for C. tropicalis are 1-2 two-fold dilution steps higher than for C. albicans and C. glabrata. In the clinical study, successful outcome was numerically slightly lower for C. tropicalis than for C. albicans at both dosages (100 and 150 mg daily). However, the difference was not significant and whether it translates into a relevant clinical difference is unknown. MICs for C. krusei are approximately 3 two-fold dilution steps higher than those for C. albicans and, similarly, those for C. guilliermondii are approximately 8 two-fold dilutions higher. In addition, only a small number of cases involved these species in the clinical trials. This means there is insufficient evidence to indicate whether the wild-type population of these pathogens can be considered susceptible to micafungin. |
Information from clinical studies
Candidaemia and Invasive Candidiasis: Micafungin (100 mg/day or 2 mg/kg/day) was as effective as and better tolerated than liposomal amphotericin B (3 mg/kg) as first-line treatment of candidaemia and invasive candidiasis in a randomised, double-blind, multinational non-inferiority study.
Micafungin and liposomal amphotericin B were received for a median duration of 15 days (range, 4 to 42 days in adults; 12 to 42 days in children).
Non-inferiority was proven for adult patients, and similar findings were demonstrated for the paediatric subpopulations (including neonates and premature infants). Efficacy findings were consistent, independent of the infective Candida species, primary site of infection and neutropenic status (see table). Micafungin demonstrated a smaller mean peak decrease in estimated glomerular filtration rate during treatment (p<0.001) and a lower incidence of infusion-related reactions (p = 0.001) than liposomal amphotericin B.
Overall Treatment Success in the Per Protocol Set, Invasive Candidiasis Study
| | Micafungin | Liposomal Amphotericin B | % Difference [95 % CI] |
| N | n (%) | N | n (%) | |
| Adult Patients |
| Overall Treatment Success | 202 | 181 (89.6) | 190 | 170 (89.5) | 0.1 [-5.9, 6.1] † |
| Overall Treatment Success by Neutropenic Status |
| Neutropenia at baseline | 24 | 18 (75.0) | 15 | 12 (80.0) | 0.7 [-5.3, 6.7] ‡ |
| No neutropenia at baseline | 178 | 163 (91.6) | 175 | 158 (90.3) |
| Paediatric Patients |
| Overall Treatment Success | 48 | 35 (72.9) | 50 | 38 (76.0) | -2.7 [-17.3, 11.9] § |
| < 2 years old | 26 | 21 (80.8) | 31 | 24 (77.4) |
| Premature Infants | 10 | 7 (70.0) | 9 | 6 (66.7) |
| Neonates (0 days to < 4 weeks) | 7 | 7 (100) | 5 | 4 (80) |
| 2 to 15 years old | 22 | 14 (63.6) | 19 | 14 (73.7) |
| Adults and Children Combined, Overall Treatment Success by Candida Species |
| Candida albicans | 102 | 91 (89.2) | 98 | 89 (90.8) | |
| Non-albicans species ¶: all | 151 | 133 (88.1) | 140 | 123 (87.9) |
| C. tropicalis | 59 | 54 (91.5) | 51 | 49 (96.1) |
| C. parapsilosis | 48 | 41 (85.4) | 44 | 35 (79.5) |
| C. glabrata | 23 | 19 (82.6) | 17 | 14 (82.4) |
| C. krusei | 9 | 8 (88.9) | 7 | 6 (85.7) |
† Micafungin rate minus the liposomal amphotericin B rate, and 2-sided 95 % confidence interval for the difference in overall success rate based on large sample normal approximation.
‡ Adjusted for neutropenic status; primary endpoint.
§ The paediatric population was not sized to test for non-inferiority.
¶ Clinical efficacy was also observed (< 5 patients) in the following Candida species: C. guilliermondii, C. famata, C. lusitaniae, C. utilis, C. inconspicua and C. dubliniensis.
Oesophageal Candidiasis: In a randomised, double-blind study of micafungin versus fluconazole in the first-line treatment of oesophageal candidiasis, 518 patients received at least a single dose of study drug. The median treatment duration was 14 days and the median average daily dose was 150 mg for micafungin (N = 260) and 200 mg for fluconazole (N = 258). An endoscopic grade of 0 (endoscopic cure) at the end of treatment was observed for 87.7 % (228/260) and 88.0 % (227/258) of patients in the micafungin and fluconazole groups, respectively (95 % CI for difference: [-5.9 %, 5.3 %]). The lower limit of the 95 % CI was above the predefined non-inferiority margin of -10 %, proving non-inferiority. The nature and incidence of adverse events were similar between treatment groups.
Prophylaxis: Micafungin was more effective than fluconazole in preventing invasive fungal infections in a population of patients at high risk of developing a systemic fungal infection (patients undergoing haematopoietic stem cell transplantation [HSCT] in a randomised, double-blind, multicentre study). Treatment success was defined as the absence of a proven, probable, or suspected systemic fungal infection through the end of therapy and absence of a proven or probable systemic fungal infection through the end of study. Most patients (97 %, N = 882) had neutropenia at baseline (< 200 neutrophils/µL). Neutropenia persisted for a median of 13 days. There was a fixed daily dose of 50 mg (1.0 mg/kg) for micafungin and 400 mg (8 mg/kg) for fluconazole. The mean period of treatment was 19 days for micafungin and 18 days for fluconazole in the adult population (N = 798) and 23 days for both treatment arms in the paediatric population (N = 84). The rate of treatment success was statistically significantly higher for micafungin than fluconazole (1.6 % versus 2.4 % breakthrough infections). Breakthrough Aspergillus infections were observed in 1 versus 7 patients, and proven or probable breakthrough Candida infections were observed in 4 versus 2 patients in the micafungin and fluconazole groups, respectively. Other breakthrough infections were caused by Fusarium (1 and 2 patients, respectively) and Zygomycetes (1 and 0 patients, respectively). The nature and incidence of adverse reactions were similar between treatment groups.