Incyte Corp.’s (INCY) blockbuster drug Jakafi is under Priority Review by the FDA as a potential treatment for steroid-refractory acute graft-versus-host disease, with a decision expected on February 24, 2019.Graft-versus-host disease, or GVHD, is a medical complication following allogeneic hematopoietic stem cell transplantation when the donor's stem cells react against the patient’s own cells. There are two types of GVHD - acute and chronic.Acute GvHD might occur once the donor's cells have engrafted in the transplant recipient, say within 100 days of transplantation, whereas chronic GvHD can appear at any time after allogeneic transplant or several years after transplantation.Corticosteroids are the mainstay of treatment for acute and chronic graft-versus-host disease.If approved, Jakafi will be the first and only treatment available in the U.S. for patients with acute GVHD who have not responded adequately to corticosteroid therapy.Jakafi, whose generic name is Ruxolitinib, is already approved in the U.S. for the treatment of patients with myelofibrosis and polycythemia vera. The drug generated revenue of $1.0 billion in the nine months ended September 30, 2018, compared to $831 million for the same period in 2017.INCY closed Tuesday’s (Jan.29, 2019) trading at $79.29, down 1.70%.