CUDC-305, is a novel heat shock protein 90 (HSP90) inhibitor with strong affinity for HSP90 alpha/beta, high oral bioavailability and potent anti-proliferative activity against a broad range of cancer cell lines (with a mean IC50 of 220 nmol/L), including many non-small cell lung cancer (NSCLC) cell lines which are resistant to standard-of-care (SOC) agents. In both laboratory and animal testing, CUDC-305 demonstrated high potency in vitro and/or in vivo across a wide range of cancers. Most notably, Curis scientists observed complete tumor regression following oral administration of CUDC-305 in a mouse xenograft model of acute myelogenous leukemia (AML). Tumor regression has also been observed after treatment of CUDC-305 in mouse xenograft models of breast, non-small cell lung, gastric cancer and glioblastoma brain cancers. In this preclinical testing, the compound also demonstrated an ability to effectively cross the blood brain barrier, and demonstrated an ability to extend survival in an intracranial glioblastoma model. Early stage toxicity studies suggest that CUDC-305 appears to have a better therapeutic window than several leading Hsp90 inhibitors in clinical development.