More recently, a renewed interest in interferon-α for the treatment of PV as an alternative therapeutic approach has led to the evaluation of pegylated interferon-α 2a (Pegasys, Roche) in several phase II studies. Pegasys has an improved toxicity profile over intron-a and can be self-administered by the patient on a weekly basis. Currently, Pegasys is being evaluated in two large international trials within the myeloproliferative disorder research consortium (MPD-RC). The MPD-RC 111 study is a phase II study intended to evaluate the response by European LeukemiaNet (ELN) criteria in patients with high risk ET/PV who are intolerant or resistant to hydroxyurea therapy treated with Pegasys. In addition, patients with documented JAK2V617F and splanchnic vein thrombosis are also eligible for this clinical trial. MPD-RC 112 is a phase III study for newly diagnosed high risk PV/ET patients in which patients are randomized to either Pegasys or hydroxyurea with a primary endpoint of response rate comparison between the two treatment arms.