Phase 2 Single Arm Study of Efficacy and Safety of P1101 for Polycythemia Vera (PV) Patients for Whom the Current Standard of Treatment is Difficult to Apply

P1101 (ropeginterferon alfa-2b) will be administered subcutaneously every 2 weeks at the starting dose of 100 μg every two weeks (or 50 μg in patients under another cytoreductive therapy). The dose should be gradually increased by 50 μg every two weeks (in parallel, other cytoreductive therapy should be decreased gradually, as appropriate) until stabilization of the hematological parameters is achieved (hematocrit \<45%, platelets \<400 x 10\^9/L and leukocytes \<10 x 10\^9/L). The maximum recommended single dose is 500 μg injected every two weeks. The dose will be maintained at the highest level which can be tolerated and delivers best possible disease response.

Low-dose aspirin (acetylsalicylic acid) (75-150 mg/day) will be given as background therapy during the 12 months of study treatment, unless contraindicated.

Phlebotomy is performed aiming at a hematocrit \< 45%. When the hematocrit value is 45% or higher, phlebotomy is performed. The volume of phlebotomy per procedure should be 200 to 400 mL while monitoring the circulatory dynamics such as blood pressure and pulse. In the elderly and patients with cardiovascular disorders, a small volume (100-200 mL) should be considered to avoid rapid changes in hemodynamics.