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Heat shock protein 90 (Hsp90); heat shock 90 kDa protein b1 (Hsp90B1; GP96; GRP94)

In vitro studies identified a purine-based specific inhibitor of the Hsp90 family protein GRP94 that could treat cancer. Pan-inhibitors of Hsp90 are known to kill cancer cells but also can trigger upregulation of other heat shock proteins. In a human breast cancer cell line, inhibition of GRP94 with small interfering RNA or a purine-based inhibitor decreased viability compared with no inhibition. In the cell line, the purine-based inhibitor did not trigger upregulation of Hsp70, which protects against apoptosis. Next steps could include evaluating the selective Hsp90 inhibitor in animal cancer models.
Samus Therapeutics LLC has PU-H71, a purine-based pan-Hsp90 inhibitor, in Phase I testing.
At least 19 other companies have Hsp90 inhibitors in Phase III testing or earlier to treat various cancers.

SciBX 6(38); doi:10.1038/scibx.2013.1058
Published online Oct. 3, 2013

Patent application filed covering purine-scaffold Hsp90 inhibitors; PU-H71 licensed to Samus Therapeutics

Patel, P.D. et al. Nat. Chem. Biol.; published online Sept. 1, 2013;
Contact: Gabriela Chiosis, Memorial Sloan-Kettering Cancer Center, New York, N.Y.

Contact: Daniel T. Gewirth, State University of New York at Buffalo, Buffalo, N.Y.