Anidulafungin, also known as LY303366, is a semisynthetic echinocandin used as an antifungal drug. Anidulafungin was approved on 2/21/2006. Anidulafungin has proven efficacy against esophageal candidiasis, but its main use will probably be in invasive Candida infection; it may also have application in treating invasive Aspergillus infection. It is a member of the class of antifungal drugs known as the echinocandins; its mechanism of action is by inhibition of (1→3)-β-D-glucan synthase, an enzyme important to the synthesis of the fungal cell wall. Anidulafungin inhibits glucan synthase, an enzyme important in the formation of (1→3)-β-D-glucan, a major fungal cell wall component. Glucan synthase is not present in mammalian cells, so it is an attractive target for antifungal activity.