Learn about Jakafi®/Jakafi XR™ (ruxolitinib) – Used to treat adults with polycythemia vera who have taken hydroxyurea and it did not work well enough or they could not tolerate it, and adults with certain types of myelofibrosis. Jakafi is used to treat adults and children 12 years of age and older with acute graft-versus-host disease (GVHD) who have taken corticosteroids and they did not work well enough. Jakafi is also used to treat adults and children 12 years of age and older with chroni