P1101 in Treating Patients With Early PMF or Overt PMF at Low or Intermediate-1 Risk

Inclusion Criteria:

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

2. Patients with pre-fibrotic/early PMF (Pre-PMF) or overt primary myelofibrosis at lowto intermediate-1 risk according to DIPSS plus, diagnosed according to WHO 2016 or 2022 classification;

3. 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. Hgb ≥10.0 g/dL at screening;

5. Neutrophil count ≥1.0 × 10^9/L at screening;

6. Creatinine clearance rate ≥30 mL/min at screening (according to the Cockcroft-Gaultformula);

7. Females of childbearing potential, as well as all women <2 years after the onsetof menopause, must agree to use an acceptable form of birth control until 60 daysfollowing the last dose of the study drug, and females must agree to not breastfeedduring 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 known contraindications to interferon α or hypersensitivity to interferon α;

2. Patients with prior interferon therapy having poor tolerability or lack of efficacyto the previous interferon therapy per investigator's judgement;

3. Patients with an ongoing cytoreduction (e.g., HU or IFN-α) at the time of screeningif, in the Investigator's opinion, randomizing them into the placebo arm will leadto immediate rebound increase of peripheral blood counts and thus may jeopardizetheir health status;

4. With severe or serious diseases that, in the Investigator's opinion, may affect thepatient's participation in this study;

5. History of major organ transplantation;

6. Pregnant or breastfeeding women;

7. Patients with any other diseases that will affect the study results or may weakenthe compliance to protocol per the Investigator's judgment;

8. Use any investigational drug <4 weeks prior to the first dose of study drug, ornot recovered from effects of prior administration of any investigational drug.

9. Eligible for JAK inhibitor therapy at screening.