What they are
Echinocandins are antifungal drugs built on a peptide ring. Each one is a cyclic hexapeptide — six amino acids joined head to tail into a ring — with a long fatty side chain attached. The US labels call them semisynthetic lipopeptides: a fungus makes the starting molecule by fermentation, and chemists modify it.
The class takes its name from echinocandin B, the natural product two of the four drugs are still made from. The building blocks are unusual: every label's chemical name lists hydroxylated ornithines and threonines, amino acids that do not occur in ordinary proteins.
How they work
Every label gives the same mechanism: echinocandins inhibit the synthesis of 1,3-beta-D-glucan, a sugar polymer that holds the fungal cell wall together. Micafungin's label adds the point that makes the class selective — the polymer "is not present in mammalian cells." The bacterial counterpart, a wall cross-linked by short peptides, is described in the peptidoglycan entry.
The four approved echinocandins, side by side
A census of the labels, in order of approval — not a ranking.
| Drug (brand) | US approval | Made from | Labelled half-life | Dosing rhythm |
|---|---|---|---|---|
| Caspofungin (Cancidas) | 2001-01-26 | Glarea lozoyensis (pneumocandin B0) | 9–11 h main phase, 40–50 h late phase | Daily |
| Micafungin (Mycamine) | 2005-03-16 | Coleophoma empetri (pneumocandin A0) | about 13–17 h | Daily |
| Anidulafungin (Eraxis) | 2006-02-17 | Aspergillus nidulans (echinocandin B) | 40–50 h | Daily |
| Rezafungin (Rezzayo) | 2023-03-22 | Aspergillus nidulans (echinocandin B) | 152 ± 29 h | Weekly |
Two details from the labels explain the spread. Anidulafungin is not broken down by the liver at all: it degrades chemically in the blood into a ring-opened form, with a half-life of about 24 hours for that step, which is then "converted to peptidic degradants." Rezafungin is made from the same starting molecule as anidulafungin, yet its label shows no observed liver metabolism and a terminal half-life of about six days (152 hours).
What each is approved for
- Caspofungin: candidemia and several deep Candida infections, oesophageal candidiasis, presumed fungal infection in feverish neutropenic patients, and invasive aspergillosis in patients who do not respond to or tolerate other therapy.
- Micafungin: candidemia and invasive candidiasis, oesophageal candidiasis, and prevention of Candida infection in stem-cell transplant recipients.
- Anidulafungin: candidemia and other Candida infections (including in children from 1 month) and oesophageal candidiasis in adults; its label warns of high relapse rates in the oesophageal indication.
- Rezafungin: candidemia and invasive candidiasis in patients aged 12 and over "who have limited or no alternative options" — the label states that approval rests on "limited clinical safety and efficacy data."
What rezafungin's trial showed
The newest member was tested against caspofungin in one randomised, double-blind trial (NCT03667690, Rezzayo label):
| Outcome (label, mITT) | Rezafungin (n = 93) | Caspofungin (n = 94) | Difference (95% CI) |
|---|---|---|---|
| All-cause mortality, day 30 | 22 (23.7%) | 20 (21.3%) | 2.4 (−9.7 to 14.4) |
| Global cure, day 14 | 55 (59.1%) | 57 (60.6%) | −1.5 (−15.4 to 12.5) |
Both intervals cross zero: the trial supports similar performance with a once-weekly schedule, not superiority. Doses below are reported from the label for reference; dosing is the treating team's decision. The label's regimen is a 400 mg loading dose, then 200 mg once weekly, and its safety "has not been established beyond 4 weekly doses."
Resistance: the FKS genes
Because every echinocandin hits the same enzyme, resistance tends to cross the class. Rezafungin's label states the mechanism: reduced susceptibility "predominantly arises from mutations in glucan synthase catalytic subunit-encoding FKS genes (FKS1 and/or FKS2)" that change "hot spot" regions of the enzyme, and rezafungin "exhibits some degree of cross-resistance to all fks mutations that confer reduced susceptibility to echinocandins." Micafungin's label records clinical failures linked to the same FKS mutations.
The label is also careful about species. It lists Candida auris among organisms for which activity has been shown in the laboratory but efficacy "has not been established in adequate and well-controlled clinical trials." PubMed holds 216 records on FKS-based echinocandin resistance and 423 on Candida auris with echinocandins (2026-11-03) — a large literature, mostly laboratory and surveillance work rather than treatment trials.
Safety on the labels
Reported from the labels for reference; monitoring belongs to the treating team.
- Shared warnings: serious allergic reactions including anaphylaxis, infusion reactions, and abnormal liver tests appear across the class (micafungin, rezafungin labels).
- Rezafungin only: photosensitivity — the label's warning section 5.3 — and the most common reactions at 5% or more in its trials: low potassium, fever, diarrhoea, anaemia, vomiting, nausea, low magnesium, abdominal pain, constipation and low phosphate. Discontinuation for an adverse reaction was 9.3% on rezafungin vs 9.0% on caspofungin.
- An animal finding, labelled as one: in a 3-month monkey study with dosing every third day, tremors began after 35–43 days at 30 mg/kg and above — about 9 times the clinical exposure — with Schwann-cell changes and nerve-fibre degeneration (Rezzayo label, section 13.2). The label's dose-finding trial excluded people with severe ataxia, tremor, neuropathy or movement disorders. The label does not report this effect in people.
Where they stand
- Caspofungin: the Cancidas brand (Merck, NDA 021227) is listed discontinued, with an FDA determination that this was not for safety or effectiveness reasons; generic caspofungin is listed as prescription (Drugs@FDA, 2026-11-03).
- Micafungin: Mycamine vials under NDA 021506 listed discontinued on the same terms; generics are prescription products.
- Anidulafungin: Eraxis (NDA 021632) listed as prescription.
- Rezafungin: Rezzayo (NDA 217417) listed as prescription; the current label (2026-07-01) names Melinta Therapeutics.
- Research record: 6,448 PubMed records; 41 randomised trials name an echinocandin (2026-11-03).
Related reading
The class's longest-covered member has its own entry: micafungin. Another ring-plus-fatty-tail antibiotic, aimed at bacteria rather than fungi, is daptomycin. The body's own antimicrobial peptide is described in the LL-37 entry.