A Study to Evaluate P1101 in Japanese PV Patients

"The subjects will be treated with P1101(ropeginterferon alfa-2b), starting at a dose of 250 micrograms. The dose of P1101 will be increased to 350 micrograms 2 weeks later and to 500 micrograms another 2 weeks later, and then P1101 will be administered at a fixed dose of 500 micrograms throughout the treatment period. Although the dose may be reduced to the prior dose for reasons related to the safety or tolerability, the increased dose should be preferably maintained throughout the treatment period.~The dose of P1101 will be increased or decreased appropriately depending on the pathological condition in the range up to 500 micrograms."

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.