PF-04449913 is a potent and selective inhibitor of the Hh signaling pathway through binding to the target, smoothened. PF-04449913 inhibits Hh signaling in vitro and has demonstrated significant antitumor activity in vivo. In the clinic, PF-04449913 is being evaluated both in hematological and solid malignancies, with a phase II trial currently underway in both fit and unfit patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS). Treatment-related adverse-events were nausea, dizziness, somnolence, QT prolongation and pruritus. Based on pre-clinical assessments, CYP3A4 is believed to be primarily involved in the metabolism of PF-04449913 that is why PF-04449913 plasma exposures and peak concentrations were increased following concurrent administration of ketoconazole (CYP3A4 inhibitor).