Rezafungin acetate (CAS 1631754-41-0) has a chemical story that connects molecular identity with practical chemistry. Rezafungin acetate is the acetate salt associated with rezafungin, a long-acting echinocandin antifungal developed as CD101 and Biafungin. Echinocandins inhibit fungal beta-(1,3)-D-glucan synthase, weakening synthesis of an essential fungal cell-wall polymer absent from human cells. Rezafungin was engineered for improved chemical stability and a prolonged pharmacokinetic profile enabling once-weekly intravenous administration. FDA approved REZZAYO in March 2023 for adults with candidemia and invasive candidiasis who have limited or no alternative treatment options. The acetate counterion belongs to the drug-substance salt identity; pharmacological activity is attributed to rezafungin.
The exact CAS identity matters because related salts, stereoisomers, intermediates and finished medicines can play very different roles even when their names look closely related.
Its story also shows why synthesis and analytical control belong together: chemists must create the intended structure, distinguish it from process-related species and verify the form actually being handled.
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