ABSTRACT
Echinocandins are a novel class of antifungal agents that were first isolated from the broth of Aspergillus species, including Aspergillus aculeatus and Aspergillus rugulovalvus, in the mid-1970s (1,2). The echinocandins block cell wall formation by inhibiting the enzyme 1,3-b-D-glucan synthase, resulting in fungal death. These compounds are poorly absorbed through the gastrointestinal tract and, therefore, are administered intravenously. Since initial investigations centered on the therapeutic activity of these compounds against Pneumocystis carinii and Candida species, the compounds were named pneumocandins. However, the spectrum of activity includes some molds, including Aspergillus species (Table 1). The three echinocandins that have reached clinical development are semisynthetic cyclic hexapeptides with N-linked fatty acyl side chains attached to pneumocandin B0 (Fig. 1) (7). Caspofungin was the first echinocandin to be licensed for clinical use (in many countries, including the United States). Micafungin is licensed for clinical use in Japan and in the United States, and anidulafungin is licensed in the United States.
