Exelixis, Inc. announced that it has submitted an investigational new drug (IND) application to the U.S. Food and Drug Administration for XL888, a novel anticancer compound. 

XL888 is an orally available small molecule inhibitor of HSP90, which is a chaperone protein that promotes the activity and stability of a range of key regulatory proteins, including kinases. The activity of HSP90 is particularly prominent in tumor cells where it promotes the activity of proteins controlling growth and survival.

Natural product-based inhibitors of HSP90 are currently in clinical trials and have shown encouraging signs of efficacy, but their utility has been limited by poor pharmacokinetic properties and by their side effect profiles,” said Gisela M. Schwab, MD, Executive Vice President and Chief Medical Officer of Exelixis. “XL888 inhibits HSP90 with potency comparable to that of natural product-based inhibitors, but with good oral bioavailability and an improved preclinical tolerability profile. XL888 exhibits substantial anti-tumor activity at well-tolerated doses in multiple preclinical xenograft models. Therefore, we believe this novel HSP90 inhibitor has the potential to become a best-in-class therapy, and we are excited to advance it into clinical development.”