The active form of Hsp inhibitor I; a benzylidene lactam compound; prevents the synthesis of inducible Hsps, including Hsp105, Hsp72, and Hsp40; decreases Hsp72 synthesis in vivo; at 100 µM, inhibits the development of thermotolerance in COLO 320 DM cells; reduces thermotolerance of tumors in SCC VII tumor-containing mice; in combination with AmB increases susceptibility of AmB-susceptible (MICs = 0.058 versus 0.27 UG/ml for combined and AmB alone, respectively) and AmB-resistant (MICs = 21.33 versus >32 UG/ml for combined and AmB alone, respectively) strains of A. fumigatus