Micafungin

Absorption

Not absorbed orally

Toxicity

Intravenous LD50 in rats is 125mg/kg. In dogs it is >200mg/kg. No cases of overdosage have been reported. Repeated daily doses up to 8 mg/kg (maximum total dose of 896 mg) in adult patients have been administered in clinical trials with no reported dose-limiting toxicity. The minimum lethal dose is 125 mg/kg in rats, equivalent to 8.1 times the recommended human clinical dose for esophageal candidiasis based on body surface area comparisons.

Description

Micafungin, the second member of the echinocandin class of antifungal agents was launched in Japan for the parenteral treatment of various fungal infections caused by Aspergillus and Candida spp. such as fungaemia and respiratory and gastrointestinal mycoses. This water-soluble semisynthetic cyclic lipopeptide is synthesized by acylation with (5-(4- pentyloxyphenyl)isoxazol-3-yl)benzoate of the cyclic peptide nucleus (FR-179642).obtained by enzymatic cleavage of the naturally occurring echinocandin FR-901379, derived from the fungus Coleophoma empedri Micafungin acts by inhibiting the synthesis of 1,3-beta-glucan, an essential polysaccharide of the cell wall of many pathogenic fungi. Micafungin has a marked fungicidal effect on almost all species of Candida, including fluconazole-resistant spp. C. albicans, C. glabrata, C. Krusei, C. parapsilosis and C. tropicalis and a fungistatic effect on a range of Aspergillus species including A. flaws, A. fumigates and A. terreus. Like caspofungin, micafungin is inactive against Cryptococcus neoformans, and the emerging pathogen Trichosporon cutaneum and Fusarium solani. Micafungin has proved highly effective in mouse models of Cancfidiasis and Aspergillus infections (including those using an amphotericin B- and itraconazole-resistant isolate of A. fumigatus). In phase I studies, micafungin had linear pharmacokinetics with an elimination half-life ranging from 11.7 to 15.2 h after injection and was well tolerated.

The Uses of Micafungin

Micafungin is a semi-synthetic cyclic lipopeptide belonging to the echinocandin class that was reported in 1999 from Fujisawa in Japan. Unlike other marketed semi-synthetic derivatives in this class, micafungin is not derived from echinocandin but rather from FR901379 which contains a phenolic sulphate to enhance aqueous solubility, a serious limitation in the class. Micafungin inhibits the synthesis of β-(1,3)-D-glucan, an essential component of the cell wall of susceptible fungi and is extensively referenced in the literature with over 700 citations.

Background

Micafungin is an antifungal drug. It belongs to the antifungal class of compounds known as echinocandins and exerts its effect by inhibiting the synthesis of 1,3-beta-D-glucan, an integral component of the fungal cell wall.

Indications

Indicated for the treatment of candidemia, acute disseminated candidiasis, and certain other invasive Candida infections, as well as esophageal candidiasis, and prophylaxis of Candida infections in patients undergoing hematopoietic stem cell transplantation. Micafungin is also used as an alternative for the treatment of oropharyngeal candidiases and has been used with some success as primary or salvage therapy, alone or in combination with other antifungals, for the treatment of invasive aspergillosis.
Indicated for the prophylaxis of Candida infections in patients undergoing hematopoietic stem cell transplantation.

What are the applications of Application

Micafungin is a semi-synthetic cyclic lipopeptide of the echinocandin class

Pharmacokinetics

Formerly known as FK463, micafungin is a semisynthetic lipopeptide synthesized from a fermentation product of Coleophoma empetri that works as an antifungal agent. It is a glucan synthesis inhibitor of the echinocandin structural class. The U.S. Food and Drug Administration approved micafungin in March 2005. Micafungin inhibits an enzyme essential for fungal cell-wall synthesis. Depending on its concentration, micafungin may be fungicidal against some Candida, but is usually fungistatic against Apergillus. Micafungin can be used concomitantly with a variety of other drugs, including the HIV protease inhibitor ritonavir and the transplant medications cyclosporine and tacrolimus.

Metabolism

Micafungin is metabolized to M-1 (catechol form) by arylsulfatase, with further metabolism to M-2 (methoxy form) by catechol-O-methyltransferase. M-5 is formed by hydroxylation at the side chain (w-1 position) of micafungin catalyzed by cytochrome P450 (CYP) isozymes. Even though micafungin is a substrate for and a weak inhibitor of CYP3A in vitro, hydroxylation by CYP3A is not a major pathway for micafungin metabolism in vivo.