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Micafungin

Micafungin is a semisynthetic belonging to the class, primarily used for the intravenous treatment of , including candidemia and acute disseminated , as well as , and for the prophylaxis of infections in patients undergoing . It functions by noncompetitively inhibiting the enzyme 1,3-β-D-glucan synthase, which is essential for the synthesis of β-1,3-D-glucan, a key structural component of the fungal , leading to cell wall disruption and fungal ; this mechanism renders it fungicidal against most species and fungistatic against species. Derived from the natural product FR901379 isolated from the fungus Coleophoma empetri by Fujisawa Pharmaceutical (now ), micafungin was first approved by the U.S. in 2005 under the brand name Mycamine for use in adults and pediatric patients aged 4 months and older. Micafungin's spectrum of activity encompasses a broad range of clinically significant fungi, including various Candida species (such as C. albicans, C. glabrata, C. krusei, and fluconazole-resistant strains), Aspergillus species, and certain molds like Paecilomyces and Penicillium, though it shows no activity against Cryptococcus, Trichosporon, or zygomycetes such as Mucor. Clinically, it has demonstrated efficacy in randomized controlled trials, achieving success rates of approximately 71% for candidemia and acute disseminated candidiasis compared to caspofungin, 88% endoscopic cure rates for esophageal candidiasis versus fluconazole, and 81% success in preventing invasive candidiasis during HSCT prophylaxis relative to fluconazole. Standard adult dosing includes 100 mg daily for candidemia, 150 mg daily for esophageal candidiasis, and 50 mg daily for prophylaxis, with pediatric doses weight-based (e.g., 2 mg/kg/day for candidemia, maximum 100 mg), administered via 1-hour infusion. Pharmacokinetically, micafungin exhibits linear with a of about 15 hours, high (>99%), hepatic metabolism independent of enzymes, and primary biliary excretion, necessitating no dose adjustments for renal impairment or mild-to-moderate hepatic dysfunction but caution in severe hepatic cases. Its safety profile is generally favorable, with common adverse effects including gastrointestinal symptoms (diarrhea, nausea, vomiting), fever, headache, and hematologic changes like ; serious risks are rare but include reactions, , and potential , requiring monitoring of liver function, renal parameters, and complete blood counts during therapy. Micafungin has minimal drug interactions due to its non-CYP450 metabolism, though it may slightly increase concentrations of substrates like or .

Medical uses

Indications

Micafungin is indicated for the treatment of candidemia and acute disseminated in adult and pediatric patients 4 months of age and older, and in neonates and infants younger than 4 months (without or ocular dissemination). In December 2019, the FDA expanded approval to include neonates and infants younger than 4 months for these indications at a dose of 4 mg/kg once daily. It is also approved for the treatment of in adult and pediatric patients 4 months of age and older, as well as peritonitis and abscesses due to species in adults, pediatric patients 4 months of age and older, and neonates and infants younger than 4 months (without or ocular dissemination). For prophylaxis, micafungin is indicated to prevent infections in patients 4 months of age and older undergoing . In clinical trials, micafungin has shown efficacy comparable to for this purpose, with success rates exceeding 80% in preventing . Although not formally approved by the FDA, micafungin has been used off-label for oropharyngeal , particularly in cases refractory to other therapies, based on its activity against . Limited evidence supports its use as salvage therapy for invasive , where it may be combined with other antifungals, though remains the primary agent. Phase III clinical trials have demonstrated micafungin's non-inferiority to comparators such as and liposomal for treating candidemia and , with overall treatment success rates ranging from 71% to 76% at the end of . In pediatric patients, including neonates with , micafungin achieved success rates around 75-80%, supporting its approval for use in children younger than 4 months. Safety and efficacy of micafungin are established in pediatric patients younger than 4 months for the treatment of candidemia, acute disseminated , peritonitis, and abscesses (without or ocular dissemination).

Contraindications

Micafungin is contraindicated in patients with known hypersensitivity to micafungin sodium, any component of the formulation, or other echinocandins, as anaphylaxis and anaphylactoid reactions, including shock, have been reported. Use of micafungin requires caution in patients with hepatic impairment, as abnormal liver function tests and hepatic failure have been observed; liver function tests should be monitored, and the drug discontinued if significant abnormalities occur. In patients with renal impairment, no dosage adjustment is necessary, but serum creatinine and blood urea nitrogen levels should be monitored due to reports of renal dysfunction and acute renal failure. Based on findings from animal reproduction studies, micafungin may cause fetal harm when administered to pregnant women; animal studies showed visceral abnormalities and reduced fetal weights at doses similar to human exposure. It should be used during pregnancy only if the potential benefit justifies the risk to the fetus. For breastfeeding, micafungin is present in the milk of lactating rats, and although human data are lacking, the decision to continue nursing or discontinue the drug should weigh the benefits of breastfeeding against potential risks to the infant. Precautions are advised with concomitant use of certain drugs due to potential interactions. Micafungin may increase exposure to (AUC increased by 21%), requiring monitoring for toxicity and possible dose reduction of . Similarly, increased levels of (AUC increased by 18%, Cmax by 42%) and (AUC increased by 22%, Cmax by 11%) have been observed, necessitating close monitoring and potential dosage adjustments for these agents. Baseline and periodic monitoring of is recommended for all patients, particularly those with preexisting hepatic impairment or risk factors, to detect any early. Renal function should also be assessed regularly in patients with known impairment or those receiving nephrotoxic agents.

Administration

Dosage

Micafungin is administered by intravenous infusion once daily, with doses tailored to the indication, patient age, and weight. For adults with , acute disseminated , , and abscesses, the recommended dosage is 100 mg once daily. For esophageal in adults, the dosage is 150 mg once daily. For prophylaxis of infections in adult recipients of , the dosage is 50 mg once daily. In the United States, micafungin is not approved for the treatment of invasive , but investigational use has employed doses of 150 mg once daily in adults. In pediatric patients aged 4 months and older, dosing is weight-based for treatment of candidemia, acute disseminated , peritonitis, and abscesses at 2 mg/kg once daily (maximum 100 mg daily). For , the dose is 3 mg/kg once daily (maximum 150 mg daily) in patients weighing 30 kg or less, or 2.5 mg/kg once daily (maximum 150 mg daily) in those over 30 kg. Prophylaxis in pediatric transplant recipients is 1 mg/kg once daily (maximum 50 mg daily). For neonates and infants younger than 4 months with (excluding candidemia with meningoencephalitis or ocular dissemination), the recommended dosage is 4 mg/kg once daily. The duration of therapy depends on clinical and mycological response as well as resolution of symptoms. For treatment of candidemia and similar infections, therapy typically lasts 10 to 47 days, with a mean of 15 days; for , 10 to 30 days (mean 15 days); and for prophylaxis, until resolution of neutropenia or engraftment (mean 19 days). No dosage adjustments are required for patients with renal impairment or mild to moderate hepatic impairment, though use in severe hepatic impairment has not been adequately studied and requires caution. Each dose should be infused over approximately 1 hour in a compatible intravenous to reduce the risk of infusion-related reactions. In cases of overdose, no specific antidote exists, and treatment is supportive, including monitoring for hypersensitivity reactions or hepatic effects; micafungin is not dialyzable.

Dosage forms

Micafungin is available in two primary pharmaceutical presentations for intravenous administration: lyophilized powder for injection in single-use vials and a ready-to-use premixed injection in flexible containers. The lyophilized form is supplied as 50 mg or 100 mg single-dose vials containing micafungin sodium with lactose as the inactive ingredient, adjusted to pH with citric acid and/or sodium hydroxide. The ready-to-use form is provided in single-dose Galaxy containers as 50 mg/50 mL (1 mg/mL), 100 mg/100 mL (1 mg/mL), or 150 mg/150 mL (1 mg/mL) solutions in 0.9% sodium chloride, with no additional reconstitution required. For the lyophilized powder, reconstitution involves adding 5 mL of 0.9% Injection, USP, or 5% Dextrose Injection, USP, to the vial, followed by gentle swirling to yield a 10 mg/mL concentration for the 50 mg vial or 20 mg/mL for the 100 mg vial; the solution must be inspected for and discarded if any are present. The reconstituted solution is then further diluted in 100 mL of the same compatible diluents to achieve a final concentration of 0.5 to 4 mg/mL, though concentrations exceeding 1.5 mg/mL should be administered via a central to minimize infusion reactions. The ready-to-use premixed injection requires no preparation and is administered directly from the container. Unopened vials of the lyophilized powder should be stored at 25°C (77°F) with excursions permitted between 15°C and 30°C (59°F and 86°F), while the ready-to-use containers are refrigerated at 2°C to 8°C (36°F to 46°F) with a 12-month . Post-reconstitution, the solution remains stable for up to 24 hours at 25°C (77°F) when protected from light, and the diluted solution is stable for the same duration; total handling time from reconstitution to administration should not exceed 48 hours. Micafungin is administered exclusively by intravenous over approximately 1 hour, using aseptic technique and flushing the IV line with 0.9% Injection, , prior to infusion; it is not intended for oral, intramuscular, or subcutaneous use. It is compatible with 0.9% Injection, , and 5% Dextrose Injection, , but must not be mixed or co-infused with other medications due to the risk of , and the ready-to-use form carries a warning for use in patients sensitive to high sodium content (200–600 mg per container).

Pharmacology

Mechanism of action

Micafungin is a semisynthetic agent that inhibits the enzyme complex responsible for synthesizing 1,3-β-D-glucan, a critical in the fungal . This inhibition disrupts the structural integrity of the fungal , which is essential for maintaining osmotic balance in fungi but absent in mammalian cells, thereby providing selectivity. At the molecular level, micafungin exerts by binding to the Fks1 subunit of the 1,3-β-D-glucan , preventing the incorporation of UDP-glucose into β-1,3-glucan chains. This blockade halts β-1,3-glucan , leading to weakened cell walls, osmotic instability, and eventual cell in susceptible fungi. The result is fungicidal activity against most species, characterized by rapid cell death, while activity against species is fungistatic, primarily causing hyphal tip damage and growth arrest without complete . Micafungin demonstrates broad activity against clinically relevant species, including C. albicans, C. glabrata, and C. krusei, as well as species. It lacks efficacy against and Mucorales (zygomycetes) due to the absence or minimal presence of β-1,3-glucan in their cell walls, and shows limited activity against dermatophytes. Resistance to micafungin is uncommon in clinical settings and primarily arises from point mutations in the "hotspot" regions of FKS1 (and sometimes FKS2) genes, which encode the glucan synthase subunit and reduce drug binding affinity. These mutations can confer cross-resistance to other echinocandins but are rare, with prevalence below 5% in most surveillance studies of .

Pharmacokinetics

Micafungin is administered intravenously due to its lack of oral , achieving complete upon . It exhibits linear over the clinically relevant dose range of 50–150 mg daily in adults. Following intravenous infusion, micafungin distributes widely with a steady-state of 0.39 ± 0.11 L/kg in healthy adults. The drug is highly bound to proteins, exceeding 99% binding primarily to . Metabolism of micafungin occurs primarily through non-CYP450 pathways, including arylsulfatase to form the derivative M-1, to form the methoxy derivative M-2, and , with minor /5-mediated contributing to metabolite M-5; these metabolites (M1–M5) are inactive and account for low systemic exposure relative to the parent compound (e.g., M-1 at 11%, M-2 at 2%, M-5 at 12% of parent ). Elimination of micafungin is characterized by a of 14–17 hours in adults, with clearance of approximately 0.010–0.015 L/h/kg. The drug undergoes biliary excretion, with 71% of the dose recovered in and 12% in over 28 days, and total recovery averaging 83%; it is not significantly dialyzable. No dosage adjustment is required for renal impairment, as remain unchanged in patients with creatinine clearance below 30 mL/min. In pediatric patients, micafungin clearance is higher than in adults on a mg/kg basis—approximately 20 mL/h/kg in children over 4 months and 40–80 mL/h/kg in neonates—necessitating weight-based dosing adjustments (e.g., 2–4 mg/kg/day in older children and up to 10 mg/kg/day in neonates) to achieve comparable systemic exposure. Placental transfer is minimal, limited by the drug's high molecular weight (approximately 1,292 ) and extensive , though animal studies indicate potential fetal harm and human data are limited.

Adverse effects

Common adverse effects

Micafungin is associated with a range of common adverse effects that are typically mild to moderate in severity, often resolving without intervention. These effects are generally self-limiting and managed with supportive care, such as antiemetics for gastrointestinal symptoms or analgesics for . Gastrointestinal disturbances are among the most frequently reported, including (affecting about 3% of patients), (2%), (2-3%), and . These symptoms are usually transient and do not require discontinuation of therapy. Neurological effects commonly include , reported in 7-13% of cases, and in around 4% of patients. Such events are often mild and resolve spontaneously upon continuation or completion of treatment. Hematological abnormalities, such as (4-6%) and , may occur but are typically and monitored through routine assessments. Dermatological reactions encompass (2-4%) and pruritus, which present as mild skin irritations without systemic involvement. Other common effects include fever, (7%), and mild, transient elevations in liver enzymes, which seldom progress to serious hepatic issues.

Serious adverse effects

Serious adverse effects of micafungin are infrequent but can involve significant organ toxicity or reactions, requiring prompt monitoring and potential discontinuation of . These include hepatic dysfunction, renal impairment, severe responses, hematologic abnormalities, and infusion-related complications, primarily identified through clinical trials and post-marketing surveillance. Hepatic effects represent a key concern, with abnormal liver function tests (LFTs), such as elevations in , , , or , occurring in up to 10% of patients in clinical settings, though often asymptomatic and reversible. More severe manifestations, including , hepatic impairment, and rare cases of hepatic failure (incidence <1%, classified as uncommon), have been reported, particularly in patients with underlying liver conditions; monitoring of and is recommended throughout treatment. Post-marketing data have documented isolated fatal hepatic events, underscoring the need for regular hepatic function assessment. Renal toxicities are less common, with elevations in serum creatinine and blood urea nitrogen observed in approximately 0.4% of micafungin-treated patients in clinical trials, compared to 0.5% with fluconazole. Acute kidney injury or significant renal dysfunction occurs in 1-2% of cases, potentially linked to infusion-related factors, and isolated instances of acute renal failure have been noted; renal function should be monitored, especially in at-risk patients. Hypersensitivity reactions can be severe, including and anaphylactoid responses (uncommon, ≥1/1,000 to <1/100), which may progress to (rare, <1/1,000); immediate discontinuation and supportive care are essential. Very rare post-marketing reports include Stevens-Johnson syndrome and , often histamine-mediated and presenting with flushing or rash during infusion. Hematologic adverse effects encompass and , with incidences varying by population— reported in up to 19% of pediatric patients in trials, though severe cases are rarer—and isolated episodes of or acute intravascular (rare, <1/1,000). Close monitoring for worsening blood counts is advised, particularly in hematologically compromised individuals. Post-marketing surveillance has identified in exceptional cases. Infusion-related reactions, such as (up to 19% in some adult trials with peripheral administration) and rigors, can occasionally escalate to serious events like ; slowing the infusion rate mitigates histamine-mediated symptoms. Post-marketing surveillance by the FDA and has captured additional rare serious events, including shock and severe , emphasizing ongoing reporting to systems for early detection. While some overlap exists with common adverse effects like mild LFT elevations, serious reactions demand heightened vigilance due to their potential for life-threatening outcomes.

Chemistry

Chemical structure

Micafungin is the sodium salt of a semisynthetic agent belonging to the class, characterized by a cyclic hexapeptide core. Its molecular formula is C₅₆H₇₀N₉NaO₂₃S, and it has a molecular weight of 1292.26 g/mol. The core structure consists of a macrocyclic hexapeptide ring derived from the natural product FR-901379 isolated from the Coleophoma empetri, with a lipophilic consisting of a 4-[5-(4-pentyloxyphenyl)isoxazol-3-yl]benzoyl moiety attached to the N² position of the modified residue at position 3. This side chain enhances the molecule's amphiphilic nature. Key modifications to the nucleus occur at positions 3, 4, and 5, including a sulfated derivative at position 4 and an N-linked modified at position 5, contributing to its structural stability. Micafungin features complex with numerous chiral centers, as evidenced by its detailed configuration. Its systematic IUPAC name is 1-[(4R,5R)-4,5-dihydroxy-N²-[4-[5-[4-(pentyloxy)phenyl]-3-isoxazolyl]benzoyl]-L-ornithine]-4-[(4S)-4-hydroxy-4-[4-hydroxy-3-(sulfooxy)phenyl]-L-threonine]pneumocandin A₀, monosodium salt.

Physical properties

Micafungin sodium is presented as a white to off-white, amorphous, hygroscopic powder that is light-sensitive, influencing its handling and storage requirements in pharmaceutical formulations. The form is freely soluble in , achieving concentrations greater than 200 mg/mL, as well as in solution and N,N-dimethylformamide; in contrast, the is poorly soluble in , with a predicted of approximately 0.215 mg/mL. Micafungin features multiple ionizable groups, with reported values of approximately 3.3 (acidic) and 9.9 (basic), which enhance its across the physiological range due to polar moieties in its structure. Its experimental logP value of -1.5 underscores a hydrophilic character and low , attributable to the abundance of polar functional groups. The (log P, octanol/ 7 buffer) is -0.39, further confirming its preference for aqueous environments over phases. Micafungin exhibits to , , and , necessitating protection from during storage; reconstituted solutions maintain for up to 24 hours at when shielded from and are optimally stable at 5-7.

History

Development

Micafungin originated from the discovery of the natural product FR901379 in 1989 by researchers at Fujisawa Pharmaceutical Company. This sulfated precursor was isolated from the broth of the Coleophoma empetri strain F-11899, obtained from a sample collected in . Initial screening identified FR901379 for its potent antifungal activity against synthesis in fungi, particularly species. To enhance its pharmacological profile, including water solubility and stability, Fujisawa chemists modified the , leading to the semisynthetic FK-463, which became known as micafungin. Preclinical evaluation of micafungin revealed broad-spectrum activity against key fungal pathogens. In vitro studies showed low minimum inhibitory concentrations against various Candida species and Aspergillus spp., outperforming earlier echinocandins in potency. In vivo experiments using animal models, such as persistently neutropenic mice with disseminated candidiasis or invasive aspergillosis, demonstrated high efficacy, with micafungin achieving significant survival rates and fungal burden reductions comparable to or better than amphotericin B. These findings established micafungin as a promising candidate for treating systemic fungal infections, particularly in immunocompromised hosts. Clinical development progressed through phased trials in the 1990s and early . I studies focused on , tolerability, and in healthy volunteers, confirming dose-proportional exposure and minimal renal or hepatic metabolism. II and III trials, conducted between 2000 and 2004, evaluated micafungin in patients with candidemia and , including neutropenic individuals. In a pivotal III study, micafungin at 100 mg daily proved non-inferior to liposomal (3 mg/kg daily), with treatment success rates around 70-80% and fewer nephrotoxic adverse events. Later pediatric trials extended these findings to children and neonates, supporting dosing adjustments based on body weight and confirming similar and profiles. As the second antifungal to reach advanced development, micafungin followed and addressed gaps in the class by offering improved solubility for intravenous administration. Its progression was supported by Fujisawa until the 2005 merger with Yamanouchi Pharmaceutical to form , which continued global clinical and manufacturing efforts.

Regulatory approvals

Micafungin received its initial regulatory approval in in 2002, marketed as Funguard by for the treatment of and . The (FDA) approved micafungin (as Mycamine) on March 16, 2005, for the treatment of esophageal in adults and adolescents aged 16 years and older, as well as for prophylaxis of infections in patients undergoing . On January 23, 2008, the FDA expanded the indications to include treatment of candidemia, acute disseminated , peritonitis, and abscesses without major abscesses in adults. On June 21, 2013, the FDA further approved these treatment indications and prophylaxis for pediatric patients aged 4 months and older. In January 2020, the FDA approved its use for the treatment of in neonates and young infants less than 4 months of age at a dose of 4 mg/kg once daily. The () authorized micafungin (as Mycamine) on April 25, 2008, for the treatment of , , and prophylaxis of infections in patients undergoing , applicable to adults, adolescents aged 16 years and older, the elderly, and pediatric patients aged 4 months and older (including neonates for ). At the time of approval, a warning was added to the labeling regarding the potential risk of hepatic carcinogenicity, stemming from observations of liver tumors in preclinical rat studies, with recommendations for post-marketing surveillance of hepatic function. Regulatory approvals followed in other regions, including in May 2007 for and prophylaxis, and in May 2013 for similar indications in adults and children. Patent protections for the original expired between 2021 and 2025 in major markets, enabling the approval and availability of versions, such as those approved by the FDA as early as 2019 and launched by 2020. As of November 2025, micafungin maintains broad regulatory approval worldwide for managing invasive fungal infections and remains on the World Health Organization's List of (23rd list, 2023), prioritizing it for candidemia and due to its efficacy and availability data.

Society and culture

Brand names

Micafungin is primarily marketed under the brand name Mycamine by worldwide, including in the United States, , and (as Funguard), following 's acquisition of the global brand rights from in August 2023. The drug was originally developed by Fujisawa Pharmaceutical Co., Ltd. (under the code FK463) and first approved in in 2002 as Funguard; Fujisawa merged with Yamanouchi Pharmaceutical Co. in 2005 to form , which held rights until the 2023 sale. Generic versions of micafungin became available in the United States starting in 2020, with approvals for manufacturers including Fresenius Kabi (first generic launch in May 2020), (October 2021), Pharma (May 2024), and (September 2025). In the , generic micafungin has been authorized since at least 2022, as evidenced by national approvals such as in the . In and , micafungin is available primarily as generics rather than under proprietary brands; examples in India include Micafung Plus (Gufic Bioscience Ltd.), Ivfungin (Alniche Life Sciences Pvt. Ltd.), and Brumica ( Medical Pvt. Ltd.), while in China, products are marketed by companies such as Renfu Pharmaceutical Co., Ltd. All marketed formulations of micafungin are lyophilized powders for reconstitution and intravenous administration, with no oral brands available globally.

Availability

Micafungin is a prescription-only intravenous medication, primarily administered in hospital settings or specialized pharmacies across the , , , and most developed countries. In the as of 2025, a 100 mg dose of branded micafungin typically costs between $500 and $1,000, while generic versions reduce this to approximately $100–300 per dose, depending on the supplier and quantity; inclusion in national formularies in countries like those in the can further lower patient costs through reimbursement programs. Supply chain disruptions have occasionally led to shortages of micafungin, often stemming from manufacturing quality issues or active pharmaceutical ingredient () constraints, as seen in regional reports from the and a resolved shortage in in ; during such periods, alternatives like are recommended to maintain treatment continuity. Access to micafungin remains limited in low-resource settings due to its high cost, need for intravenous infrastructure, and reliance on imported supplies, though global initiatives like the Global Action Fund for Fungal Infections and Immunity (GAFFI) target 95% population access to antifungals by 2025, with emerging generics from manufacturers in and elsewhere showing potential for broader availability despite the absence of current WHO prequalification. As an agent with no known abuse potential, micafungin is not classified as a and is regulated solely as a prescription worldwide. formulations, approved by the FDA since 2019, improve affordability and access compared to branded products like Mycamine.