Extension Study of P1101 After Completion of Phase 2 Study in PV Patients or Phase 3 Study in ET Patients

Extension Study of P1101 After Completion of Phase 2 Study in PV Patients or Phase 3 Study in ET Patients

Extension Study of P1101 in Japanese Patients Who Have Completed Phase 2 Single Arm Study in Polycythemia Vera (PV) Patients (Study A19-201) or Phase 3 Study in Essential Thrombocythemia (ET) Patients (Study P1101 ET)

This is a Phase 3 open-label, multicenter, single arm study designed to evaluate the efficacy and safety and tolerability of P1101 patient with PV or ET in long-term.

The study is to evaluate the long-term safety and efficacy of P1101 in PV or ET patients who participated in Study A19-201 or Study P1101 ET. The subjects who have completed the 52-week P1101 treatment duration in Study A19-201 will start treatment with P1101 at the dose at Week 50. The subjects who have completed the follow-up/end-of-study visit in Study P1101 ET will start treatment with P1101 at the dose at Week 50. The subjects who were treated with anagrelide will start treatment with P1101 at a dose of 250 μg. The dose of P1101 during this study may be increased or decreased up to 500 μg depending on the condition. Evaluation of safety will include assessing vital signs, clinical safety laboratory tests, physical examinations, ECG evaluation, heart ECHO, lung X-ray, ECOG performance status, ocular examination, and AEs. Efficacy evaluations, safety assessments, and immunogenicity evaluations of P1101 will be performed. Evaluation of efficacy will include clinical laboratory assessments, allelic burden measurements of CALR, JAK-2, and MPL, spleen size measurements, bone marrow sampling.

Conventional treatment based on phlebotomies, low-dose aspirin (acetylsalicylic acid, 75-150 mg/day) plus the subcutaneous administration of P1101 (ropeginterferon alfa-2b) once every 2 weeks

Conventional treatment based on phlebotomies, lowdose aspirin (acetylsalicylic acid, 75-150 mg/day) plus the subcutaneous administration of pegylated prolineinterferon alpha-2b (P1101, Ropeginterferon alfa-2b) once every 2 weeks.

The subjects who have completed the 52-week treatment duration in Study A19-201 will be treated with P1101, starting at the dose at Week 50. The dose during this study may be increased or decreased up to 500 μg depending on the condition. This study will be continued as a post-marketing clinical study after acquisition of the marketing approval of P1101.

CHR will be defined as follows. Hematocrit <45% phlebotomy-free (absence of phlebotomy during the previous 12 weeks) Platelet count ≤ 400 x 10^9/L WBC count ≤ 10 x 10^9/L

Bone marrow histological remission was defined as the disappearance of hypercellularity and trilineage growth (panmyelosis), and absence of >grade 1 reticulin fibrosis in the subjects who gave informed consent in Study A19-201

Inclusion Criteria: Patients who have completed the 52-week treatment duration in Study A19-201 and are considered by the investigator or sub investigator to be eligible for participation in this study Patients who have given written informed consent to participate in this study Exclusion Criteria: Patients who are considered by the investigator or sub investigator to be ineligible for continued treatment with P1101