Incyte Corp.’s (INCY) blockbuster drug Jakafi is under FDA review for the expanded indication as a treatment for steroid-refractory acute graft-versus-host disease, with a decision expected on May 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. In the U.S., the drug generated annual product revenue of $1.4 billion in 2018 compared to $1.1 billion in 2017.Jakafi is marketed by Incyte in the United States and by Novartis as Jakavi outside the United States.INCY closed Thursday’s trading at $73.94, up 0.57%.