Objectives: To compare the efficacy and safety in Adult patients (≥18 years) diagnosed as essential thrombocythemia treated with the Pegylated Interferon Alfa-2b vs. Interferon Alfa. Study Design: A prospective, open-label, multicenter, randomized controlled clinical trial.

This is a prospective, open-label, multicenter, randomized controlled clinical trial between Interferon Alfa and Pegylated Interferon Alfa-2b in adult essential thrombocythemia (≥18 years).

Patients will be randomly divided into the following two treatment groups: 1. Recombinant Interferon Alpha, with an initial dose of 300 wu three times a week. Other interferons that have been listed can be used if Recombinant Interferon Alpha (300 wu) is not available. 2. Pegylated Interferon Alfa-2b, with an initial dose of 135 ug at week 0 , and then 180 ug once a week from week 1 to week 52.

The dosage will be adjusted according to the results of laboratory examinations and patient tolerance. The patient will be transferred to the other group if intolerance or resistance occurs.

Inclusion Criteria:

• ≥18 years old.
• Male or Female.
• Diagnosis of essential thrombocythemia according to the 2016 World Health Organization criteria.
• Those who have not use interferon within 4 weeks before the first medication.
• Patients with indications for cytoreductive therapy.
• Men and women with reproductive potential, as well as all women with menopause less than 2 years, must agree to use acceptable contraceptive methods until 28 days after the last dose of study drug, and women must agree not to breastfeed during the study period.
• Voluntary written informed consent.

Exclusion Criteria:

• Resistance, or intolerance, or any contraindications to interferon.
• Patients with active thrombosis or active bleeding.
• Neutrophil count < 1.0x10^9/L.
• Hemoglobin < 11g/dL for male, or < 10g/dL for female.
• Poor control of thyroid dysfunction.
• Patients with a prior malignancy within the last 3 years.
• Patients with severe cardiac or pulmonary dysfunction.
• Severe renal damage (creatinine clearance < 30 ml / min).
• Severe liver dysfunction (ALT or AST > 2.5×ULN).
• Patients with hepatitis B virus, hepatitis C virus replication or HIV infection.
• Patients with a history of drug / alcohol abuse (within 2 years before the study).
• Patients that have participated in other experimental researches within one month before enrollment.
• History of psychiatric disorder.
• Any other circumstances that the investigator considers that the patient is not suitable to participate in the trial.