A Study to Assess Efficacy, Safety, and Tolerability of P1101 in Adult Patients With PV

Inclusion Criteria:

1. Male or female subjects aged ≥18 years at the time of signing the informed consentform

2. Subjects diagnosed with PV according to the 2008 or 2016 World Health Organization (WHO) criteria

3. Subjects with good liver function at screening, which is defined as total bilirubin ≤1.5 × upper limit of normal (ULN), international normalized ratio (INR) ≤1.5 × ULN,albumin >3.5 g/dL, alanine aminotransferase (ALT) ≤2.0 × ULN, and aspartateaminotransferase (AST) ≤2.0 × ULN

4. Hemoglobin (HGB) ≥10 g/dL for females, and HGB ≥11 g/dL for males at screening

5. Neutrophil count ≥1.5 × 10^9/L at screening

6. Creatinine clearance rate ≥40 mL/min at screening (according to the Cockcroft-Gaultformula)

7. Males and females of childbearing potential, as well as all women <2 years after theonset of menopause, must agree to use an acceptable form of birth control until 60days following the last dose of the study drug, and females must agree to notbreastfeed during the study

8. Written informed consent obtained from the subject and ability for the subject tocomply with the requirements of the study

Exclusion Criteria:

1. Any contraindications to interferon alfa or hypersensitivity to interferon alfa

2. Subjects who stopped prior to interferon alfa therapy due to low efficacy or poortolerability

3. Subjects with severe or serious diseases that the Investigator determines may affectthe subject's participation in this study

4. History of major organ transplantation

5. Pregnant or breastfeeding women

6. Subjects with any other diseases that the Investigator determines will affect thestudy results or may weaken the compliance to protocol, including but not limitedto:

7. Prior or current autoimmune thyroid disease (clinical symptoms of hyper- orhypo-thyroidism), except subjects with controlled thyroid replacement therapy,could be enrolled

8. Other documented autoimmune diseases (such as hepatitis, immunethrombocytopenia [ITP], scleroderma, psoriasis, or any autoimmune arthritis)

9. Clinically significant pulmonary infiltration, infectious pneumonia, andnon-infectious pneumonia, or a past history of interstitial pneumonia atscreening

10. Active infection with systemic manifestations (e.g., presence of bacteria,fungi, and/or human immunodeficiency virus [HIV] at screening, excludinghepatitis B [HBV] and/or hepatitis C [HCV] at screening)

11. Evidence of severe retinopathy (e.g., cytomegalovirus [CMV]-induced retinitis,macular degeneration) or clinically significant eye diseases (due to diabetesor hypertension)

12. History or presence of clinically relevant depression per Investigator'sjudgment

13. Previously had suicidal attempts or has any risk for suicidal tendency atscreening

14. Poorly controlled diabetes defined as HbA1c >8.0% for at least 1 year

15. Active thromboembolic complications caused by PV and abdominal hemorrhage inthe active phase

16. History of any malignancy within 5 years (except adequately treatednon-melanoma skin cancer, prostate cancer status post resection with anundetectable prostate-specific antigen (PSA), curative treated in-situ cancerof the cervix, ductal carcinoma in situ (DCIS) of the breast, Stage 1 Grade 1endometrial carcinoma, or other solid tumors including lymphomas (without bonemarrow involvement) curatively treated with no evidence of disease for ≥2 yearsprior to study)

17. History of alcohol or drug abuse in the past year

18. History or evidence of post-polycythemia vera-myelofibrosis (PPV-MF), essentialthrombocythemia, or any non-PV MPN

19. Presence of blast cells in the peripheral blood in the past 12 weeks

20. Use any investigational drug <4 weeks prior to the first dose of study drug, or notrecovered from effects of prior administration of any investigational drug

21. Any subject requiring a legally authorized representative