Does anidulafungin have better efficacy data compared to micafungin for aspergillosis that is azole resistant?

Comment by InpharmD Researcher

There is an overall lack of direct comparative clinical data between anidulafungin vs micafungin in the treatment of azole-resistant invasive aspergillosis. In general, guidance for invasive aspergillosis suggests echinocandins can be considered in settings where azole and polyene antifungals are contraindicated and in patients with hematologic malignancies and/or persistent neutropenia, and does not recommend primary therapy with an echinocandin; no recommendations are provided to guide selection between echinocandin agents, however. Anidulafungin has primarily been evaluated in combination with voriconazole vs as monotherapy for primary or salvage invasive aspergillosis. In refractory or progressive aspergillosis, micafungin is specifically named as an option for salvage therapy, though recommendations regarding anidulafungin are scarce due to limited literature assessing its efficacy as monotherapy in primary or salvage therapy for invasive aspergillosis. Notably, neither anidulafungin nor micafungin is currently approved by the Food and Drug Administration (FDA) for treatment of invasive aspergillosis.

An extensive literature search identified 2 clinical practice guidelines and 4 primary sources relevant to this inquiry which are summarized in this response.

Background

Available guideline statements do not provide comparative efficacy data between anidulafungin and micafungin for azole-resistant invasive aspergillosis. Notably, neither anidulafungin nor micafungin is currently approved by the Food and Drug Administration (FDA) for treatment of invasive aspergillosis. Anidulafungin has primarily been evaluated in combination with voriconazole rather than as monotherapy for primary or salvage invasive aspergillosis. The 2016 Infectious Diseases Society of America (IDSA) aspergillosis guidelines acknowledge that there is limited clinical experience with anidulafungin for both adult and pediatric patients at the time of issuance of these guidelines. In a randomized trial of 454 patients with hematologic malignancy, mortality at 6 weeks was 19.3% with voriconazole plus anidulafungin combination versus 27.5% with voriconazole monotherapy (p=0.087), while a post hoc analysis in patients with “probable” aspergillosis showed mortality rates of 15.7% versus 27.3%, respectively (p=0.037) with no significant toxicity differences between groups. Based on this study, the panel recommended consideration for initial combination therapy with voriconazole plus an echinocandin for patients with severe invasive aspergillosis, especially associated with hematologic malignancies and/or profound neutropenia. The 2025 American Thoracic Society guideline on treatment of invasive pulmonary aspergillosis also described this study as showing a nonsignificant but potentially clinically meaningful reduction in mortality with combination therapy, although certainty of evidence was considered low. In comparison, micafungin has been studied as salvage therapy, with a reported 44% survival rate at 6 weeks in a study of 326 patients. Current guidelines support consideration of echinocandins in combination regimens because of their differing mechanisms of action, but do not identify evidence demonstrating superiority of anidulafungin over micafungin in azole-resistant disease. Notably, the IDSA aspergillosis guidelines are currently in process of being updated, and clinicians should be mindful of any pertinent updated recommendations once the new iteration of these guidelines is issued. [1], [2]

References: [1] Patterson TF, Thompson GR 3rd, Denning DW, et al. Practice Guidelines for the Diagnosis and Management of Aspergillosis: 2016 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2016;63(4):e1-e60. doi:10.1093/cid/ciw326
[2] Epelbaum O, Marinelli T, Haydour Q, et al. Treatment of Invasive Pulmonary Aspergillosis and Preventive and Empirical Therapy for Invasive Candidiasis in Adult Pulmonary and Critical Care Patients: An Official American Thoracic Society Clinical Practice Guideline. Am J Respir Crit Care Med. 2025;211(1):34-53. doi:10.1164/rccm.202410-2045ST
Literature Review

A search of the published medical literature revealed 4 studies investigating the researchable question:

Does anidulafungin have better efficacy data compared to micafungin for aspergillosis that is azole resistant?

Level of evidence

B - One high-quality study or multiple studies with limitations  Read more→


Please see Tables 1-4 for your response.

Randomised, multicentre trial of micafungin vs. an institutional standard regimen for salvage treatment of invasive aspergillosis
Design

Randomized, phase 2, multicenter, prospective, controlled, open-label, parallel arm clinical study

N= 17
Objective To evaluate the efficacy and safety of micafungin as salvage monotherapy in patients with proven or probable invasive aspergillosis who were refractory or intolerant to previous systemic antifungal therapy
Study Groups

Micafungin (n= 12)

Control (n= 5)
Inclusion Criteria Patients aged ≥18 years with proven invasive aspergillosis, an allogeneic or autologous haematopoietic stem cell transplant, acute leukemia or myelodysplastic syndrome, refractory or intolerant to a systemic antifungal agent used as first-line therapy. Refractory condition defined as those patients who had received >7 consecutive days of systemic antifungal therapy prior to the start of the study and who had infection progression.
Exclusion Criteria Not specified
Methods Patients were randomized 2:1 to receive either 300 mg intravenous (IV) once daily micafungin monotherapy or an alternative IV control salvage monotherapy as control (i.e., amphotericin B liposomal, colloidal dispersion or lipid complex; voriconazole; or caspofungin) for 3–12 weeks. Final assessment was conducted 12 weeks after treatment start.
Duration June 30, 2006 through September 7, 2008
Outcome Measures

Primary: Overall treatment success at end of treatment (EOT)

Secondary: Overall treatment success at 12 weeks after the start of treatment
Baseline Characteristics  

Micafungin

(n= 12)

Control

(n= 5)
Male 8 (66.7%) 3 (60.0%)
Mean age, years 53.6 53.6
Neutropenia 9 (75.0%) 0 (0.0%)
Allogeneic stem cell transplant 5 (41.7%) 0 (0.0%)
Acute myelogenous leukemia 8 (66.7%) 4 (80.0%)
Results  

Micafungin

(n= 12)

Control

(n= 5)
Successful therapy at EOT 3 (25.0%), 95% CI 5.5% to 57.2% 3 (60.0%), 95% CI 14.7% to 94.7%
Successful therapy at 12 weeks 6 (50.0%), 95% CI 21.1% to 78.9% 1 (20.0%), 95% CI 0.5% to 71.6%

Causative organisms identified (micafungin vs control): Aspergillus fumigatus (n/n = 1/1); Aspergillus flavus (n/n = 1/0); unidentified Aspergillus spp. (n/n = 9/4); other mold, not other-wise specified (n/n = 1/0). Of the 13 patients with an unidentified Aspergillus spp. infection, 10 (n/n = 6/4) had a positive galactomannan antigen test result.
Adverse Events Fifteen patients (88.2%) experienced adverse events. Common adverse events included leucocytosis, neutropenia, melaena, nausea, chest pain, and sepsis. Three patients in the micafungin arm experienced nausea, vomiting, diarrhoea, and hyperbilirubinaemia related to treatment. One patient in the control arm experienced cholestasis related to caspofungin treatment.
Study Author Conclusions No clear trends in efficacy and safety can be concluded due to the small, heterogeneous patient population and imbalance in patient numbers between treatment arms. The study was discontinued early due to low enrollment and a shift towards combination therapy for salvage treatment. No other trends in efficacy and safety can be concluded.
Critique The study was limited by its small sample size, early discontinuation, and the shift in clinical practice towards combination therapy, which affected enrolment. The lack of statistical comparisons between treatment arms and the imbalance in patient numbers further limit the conclusions that can be drawn from the study.

 

References:
[1] [1] Cornely OA, Meems L, Herbrecht R, Viscoli C, van Amsterdam RG, Ruhnke M. Randomised, multicentre trial of micafungin vs. an institutional standard regimen for salvage treatment of invasive aspergillosis. Mycoses. 2015;58(1):58-64. doi:10.1111/myc.12274
In Vitro Susceptibility of Clinical Isolates of Aspergillus spp. to Anidulafungin, Caspofungin, and Micafungin: a Head-to-Head Comparison Using the CLSI M38-A2 Broth Microdilution Method
Design

In vitro, multicenter, international study across >60 sites

N= 526
Objective To determine the in vitro activities of anidulafungin, caspofungin, and micafungin against clinical isolates of Aspergillus spp. using the CLSI M38-A2 broth microdilution method
Study Groups

A. flavus (n= 64)

A. fumigatus (n= 391)

A. niger (n= 46)

A. terreus (n= 25)
Inclusion Criteria Clinical isolates of Aspergillus spp. collected
Methods Susceptibility testing was performed using the CLSI M38-A2 broth microdilution method. Reference powders of anidulafungin, caspofungin, and micafungin were used. Stock solutions were prepared in water or dimethyl sulfoxide, and serial twofold dilutions were made in RPMI 1640 medium buffered to pH 7.0. The minimum effective concentration (MEC) was determined after 48 hours of incubation at 35°C.
Duration January 2001 to December 2007
Outcome Measures

Primary: In vitro susceptibility of Aspergillus spp. to anidulafungin, caspofungin, and micafungin

Secondary: MEC50 and MEC90 values for each echinocandin against Aspergillus spp.
Baseline Characteristics  

A. flavus

(n=64)

A. fumigatus

(n=391)

A. niger

(n=46)

A. terreus

(n=25)
Anidulafungin MEC50 (mcg/mL) 0.007 0.007 0.007 0.007
Anidulafungin MEC90 (mcg/mL) 0.015 0.015 0.015 0.015
Caspofungin MEC50 (mcg/mL) 0.015 0.015 0.015 0.015
Caspofungin MEC90 (mcg/mL) 0.03 0.03 0.03 0.03
Micafungin MEC50 (mcg/mL) 0.007 0.007 0.007 0.007
Micafungin MEC90 (mcg/mL) 0.015 0.015 0.015 0.015
Results   Anidulafungin Caspofungin Micafungin
A. flavus 100% 100% 100%
A. fumigatus 100% 99% 100%
A. niger 100% 100% 100%
A. terreus 100% 100% 100%
Study Author Conclusions The study demonstrates the comparable and excellent levels of inhibitory activity of anidulafungin, caspofungin, and micafungin against Aspergillus spp., with a distinct lack of isolates showing significantly decreased susceptibility. Continued surveillance is warranted to monitor the activities of these agents.
Critique The study provides a comprehensive head-to-head comparison of echinocandins against Aspergillus spp. using a large, globally diverse collection of isolates. However, it is limited by its in vitro nature, which may not fully represent clinical outcomes. The study does not address potential resistance mechanisms or clinical efficacy in patients.

 

References:
[1] [1] Pfaller MA, Boyken L, Hollis RJ, et al. In vitro susceptibility of clinical isolates of Aspergillus spp. to anidulafungin, caspofungin, and micafungin: a head-to-head comparison using the CLSI M38-A2 broth microdilution method. J Clin Microbiol. 2009;47(10):3323-3325. doi:10.1128/JCM.01155-09
Comparison Between Etest and Broth Microdilution Methods for Testing Itraconazole-Resistant Aspergillus fumigatus Susceptibility to Antifungal Combinations
Design

Comparative study evaluating two methods (Etest and Broth Microdilution, BMD) for antifungal susceptibility testing

N= 15 itraconazole-resistant Aspergillus fumigatus clinical strains
Objective To evaluate the correlation between Etest and BMD methods in testing antifungal combinations against itraconazole-resistant Aspergillus fumigatus
Methods The study compared the Etest and BMD methods for testing antifungal combinations. Etest and BMD were used to evaluate combinations of azoles (itraconazole, posaconazole, voriconazole) with echinocandins (anidulafungin, caspofungin, micafungin) against 15 itraconazole-resistant Aspergillus fumigatus strains. Readings were taken at 24 and 48 hours, considering minimum inhibitory concentration (MIC) and minimum effective concentration (MEC) endpoints.
Outcome Measures

Primary: Correlation coefficients between Etest and BMD methods

Secondary: Synergism, indifference, and antagonism percentages for drug combinations
Results   Etest-24 h-MIC Etest-48 h-MIC Etest-24 h-MEC Etest-48 h-MEC BMD-24 h-MEC BMD-48 h-MIC
ITZ + CAS 0.153 0.226 0.529 0.756 0.661 0.608
ITZ + MFG 0.226 0.349 0.616 1.341 3.149 0.727
ITZ + ANF 0.144 0.190 1.296 1.724 4.931 0.595
Study Author Conclusions The Etest method showed higher percentages of synergism compared to the BMD method, especially when MIC values were considered. Improvements in experimental conditions may increase the correlation between the two methods, making Etest a viable option for evaluating antifungal combinations against Aspergillus species.
Critique The study provides valuable insights into the correlation between Etest and BMD methods, highlighting the potential of Etest for antifungal susceptibility testing. However, the small sample size and lack of detailed patient data may limit the generalizability of the findings. Additionally, the study does not specify the duration of the testing period, which could impact the interpretation of results.

 

References:
[1] [1] Denardi LB, Keller JT, de Azevedo MI, et al. Comparison Between Etest and Broth Microdilution Methods for Testing Itraconazole-Resistant Aspergillus fumigatus Susceptibility to Antifungal Combinations. Mycopathologia. 2018;183(2):359-370. doi:10.1007/s11046-017-0208-7
Comparative Pharmacodynamics of Echinocandins against Aspergillus fumigatus Using an In Vitro Pharmacokinetic/Pharmacodynamic Model That Correlates with Clinical Response to Caspofungin Therapy: Is There a Place for Dose Optimization?
Design

In vitro pharmacokinetic/pharmacodynamic model study
Objective To explore the efficacy of dose escalation in echinocandins for the treatment of invasive aspergillosis and to correlate in vitro pharmacokinetic/pharmacodynamic indices with clinical outcomes of caspofungin therapy
Methods In vitro PK/PD model simulating anidulafungin, caspofungin, and micafungin exposures with varying fCmax and half-lives. Analyzed the relationship between fAUC0–24/MEC and % aberrant mycelium formation. Monte Carlo analysis for probability of target attainment (PTA) of different dosing regimens.
Outcome Measures

Primary: PK/PD indices associated with 50 to 99.99% maximal activity (EI50 to EI99.99) correlated with clinical outcomes

Secondary: PTA for different dosing regimens
Baseline Characteristics   Wild-type (WT) isolates Non-WT isolates
CLSI MEC for anidulafungin 0.016 mg/liter 2 to 16 mg/liter
CLSI MEC for caspofungin 0.25 mg/liter 4 to 16 mg/liter
CLSI MEC for micafungin 0.016 mg/liter 1 to 8 mg/liter
Results   Anidulafungin Caspofungin Micafungin
EI99 fAUC0–24/CLSI MEC 766 8.8 115
PTA for standard dose 10% 13% 0%
PTA for optimized dose 10% (1,500 mg/day) 90% (100 mg/day) 90% (1,400 mg/day)
Study Author Conclusions Caspofungin dose escalation might deserve clinical validation as it showed a high probability of target attainment at higher doses, suggesting potential for dose optimization in the treatment of invasive aspergillosis.
Critique The in vitro nature of the study limits direct clinical applicability, and further clinical trials are needed to validate the findings.

 

References:
[1] [1] Siopi M, Perlin DS, Arendrup MC, Pournaras S, Meletiadis J. Comparative Pharmacodynamics of Echinocandins against Aspergillus fumigatus Using an In Vitro Pharmacokinetic/Pharmacodynamic Model That Correlates with Clinical Response to Caspofungin Therapy: Is There a Place for Dose Optimization?. Antimicrob Agents Chemother. 2021;65(4):e01618-20. Published 2021 Mar 18. doi:10.1128/AAC.01618-20