Heat shock protein 90 (Hsp90) is a chaperone that maintains the functionality of client proteins involved in cell proliferation, cell cycling, and apoptosis. XL888 is an ATP-competitive inhibitor of Hsp90. Through this action, specific client proteins are degraded, resulting in cell cycle arrest or apoptosis. XL888 is orally bioavailable and shows efficacy in tumor regression in gastric carcinoma and melanoma xenografts in mice.
