I am currently taking a similar drug for Myelofibrosis on a clinical trial holed up after a stem cell transplant here at MD Anderson Cancer Center. It's called Itacitinib, and is supposed to prevent GVHD. It's by the same company that makes Jakafi (brand name). These are expensive drugs for sure, and my DR is running the clinical trial. Just wanted to chime in from the inside. ;p