Efungumab is a human recombinant monoclonal antibody fragment—specifically, a single-chain variable fragment (scFv). It was developed as a novel adjuvant therapy for the treatment of invasive candidiasis, a serious and often life-threatening fungal infection. Unlike traditional antifungals, efungumab does not directly kill the fungus. Instead, it functions as a targeted immunotherapeutic agent that binds to a heat shock protein on the fungal cell, aiming to enhance the efficacy of conventional antifungal drugs like amphotericin B.