Heat shock protein (Hsp) inhibitor II is the active form of Hsp inhibitor I and a benzylidene lactam compound that prevents the synthesis of inducible Hsps, such as Hsp105, Hsp72, and Hsp40. Hsp inhibitor II decreases Hsp72 synthesis in vivo and reduces thermotolerance of tumors in SCC VII tumor-containing mice. At 100 μM, it inhibits the development of thermotolerance in COLO 320 DM cells. Inhibition of Hsp70 with Hsp inhibitor II in combination with amphotericin B increases susceptibility of AmB-susceptible (MICs = 0.058 versus 0.27 μg ml for combined and AmB alone, respectively) and AmB-resistant (MICs = 21.33 versus >32 μg ml for combined and AmB alone, respectively) strains of A. fumigatus.
Luminespib, also known as AUY-922, NVP-AUY922, VER52296, is a derivative of 4,5-diarylisoxazole and a third-generation heat shock protein 90 (Hsp90) inhibitor with potential antineoplastic activity. Hsp90 inhibitor AUY922 has been shown to bind with high affinity to and inhibit Hsp90, resulting in the proteasomal degradation of oncogenic client proteins; the inhibition of cell proliferation; and the elevation of heat shock protein 72 (Hsp72) in a wide range of human tumor cell lines.