Jaktinib Versus Hydroxycarbamide in Subjects With Intermediate-2 or High-risk Myelofibrosis

Inclusion Criteria: * Age ≥ 18 years old,either male or female; * Subjects diagnosed with a PMF according to World Health Organiztion criteria (2016 Edition), or patients diagnosed with a Post-PV-MF or Post-EF-MF according to International Working Group for Myeloproliferative Neoplasms Research and Treatment criteria; * High risk or intermediate-2 risk as defined by the Dynamic International Prognostic Scoring System (DIPSS) for Primary Myelofibrosis; * Subjects have no plan for stem cell transplantation in the near future; * Life expectancy of \> 24 weeks; * ECOG performance status of 0-1; * Palpable splenomegaly at least 5 cm below left costal margin; * Peripheral blood blast count ≤ 10%; * Subjects who have not yet received treatment with a JAK inhibitor, or Subjects who have been treated with JAK inhibitors for ≤10 days; * Subjects have not received growth factor, thrombopoietin mimetics or platelet transfusion(s) within 2 weeks before the randomization; ANC≥ 1.0×10\^9/L, platelet count ≥ 100×10\^9/L within 2 days before the randomization; * Normal functions in major organs within 7 days before the randomization, fulfilling the following criteria: ALT and AST ≤ 2.5×ULN; DBIL and TBIL ≤ 2.0×ULN; serum creatinine ≤ 1.5×ULN; * If the subject is receiving any anti-myelofibrosis treatment (except for JAK inhibitors and hydroxyurea) at screening, the dosing regimen must remain unchanged for at least 2 weeks before screening. If the investigator judges that there is no need to continue to use, stop the use of thalidomide, androgens and prednisone\> 10 mg during screening. The drugs used to improve anemia should be stopped for at least 6 half-lives or 2 weeks before randomization(whichever is the longer); * If the subject is receiving Hydroxycarbamide treatment at screening, the drug must be discontinued ≥ 2 weeks before the randomization; * Meet the requirements of the ethics committee and willing to sign the informed consent form; * Ability to comply with trial and follow-up procedures. Exclusion Criteria: * Subjects with any significant clinical and laboratory abnormalities which may affect the safety evaluation, such as uncontrolled diabetes, uncontrolled hypertension after taking two or more hypotensive drugs, peripheral neuropathy; * Subjects with congestive heart failure, uncontrolled or unstable angina or myocardial infarction, cerebrovascular accident, or pulmonary embolism within 24 weeks prior to screening; * Subjects who have not fully recovered from surgical operation within 4 weeks prior to screening; * Subjects suffering from arrhythmia and requiring treatment at screening; * Subjects with clinical symptoms of active bacterial, viral, parasitic or fungal infections requiring treatment at screening; * Chest X-rays suggest an active lung infection at screening; * Subjects who had active tuberculosis infection within 48 weeks before screening;γ-Interferon release test suggests latent tuberculosis infection at screening; * Subjects who had undergone splenectomy, or received radiotherapy to the spleen within 48 weeks before screening; * Subjects with known human immunodeficiency virus (HIV), known active infectious Hepatitis B (HepB), and/or known active infectious Hepatitis C (HepC); * Subjects with epilepsy or patients who have received psychotropic drug or sedatives during screening; * Female subjects who are pregnant, currently breastfeeding, planning to become pregnant;Subjects who are unable to adopt effective contraceptive methods during the study; Male subjects who did not use condoms during the dosing period and within 2 days after the last dose * Subjects who had experienced malignant tumors within the past 5 years (except for adequately treated local basal cell carcinoma of the skin and cervical carcinoma in situ that have been cured); * Subjects who are unsuitable to the trial in combination with other serious diseases, as identified by the investigator; * Subjects with suspected allergies to Jaktinib or its excipient; * Subjects who have participated in another clinical trial of a new drug or medical instrument within 12 weeks before screening.