XL-888 is a novel and orally-bioavailable inhibitor of heat shock protein 90 (HSP90) that selectively inhibits HSP90α and HSP90β with values of 50% inhibition concentration IC₅₀ of 22 nM and 44 nM respectively. It also exerts considerably weaker inhibition against a range of other diverse kinases with IC₅₀ more than 3600 nM for all. X-ray crystallographic analysis reveals that the XL-888 binds to HSP90 through the formation of H-bonding between the N-(R)-sec-butylanthranilamide moiety of XL-888 and ASP93 of HSP90. In recent studies, XL-888 has exhibits strong anti-proliferative activities in a panel of tumor cells with values of IC₅₀ ranging from 0.1 nM to 45.5 nM.

Reference

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