Study of DISC-0974 (RALLY-MF) in Participants With Myelofibrosis or Myelodysplastic Syndrome and Anemia

This phase 1b/2a open-label study will evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and clinical activity of DISC-0974 as well as categorize the effects on hematologic response in participants with myelofibrosis or myelodysplastic syndrome and anemia.

Inclusion Criteria for Participants with MF and Anemia: Participants are eligible for the study if all of the following criteria apply: 1. Age 18 years or older at the time of signing the informed consent form (ICF). 2. For Phase 1b: Dynamic International Prognostic Scoring System (DIPSS) score of 3 to 4 (intermediate 2 risk) or ≥5 (high-risk) primary MF, post PV MF, and/or post ET MF, as confirmed in the most recent local bone marrow biopsy report, according to World Health Organization (WHO) 2016 criteria. For Phase 2: In addition to the criteria above, DIPSS score of ≥2 (intermediate 1 risk) may also be included. 3. Washout of at least 28 days prior to Screening of the following treatments: 1. Androgens 2. EPO 3. Cladribine 4. Immunomodulators (lenalidomide, thalidomide) 5. Luspatercept/sotatercept 6. Systemic corticosteroids are permitted for non-hematological conditions if stable or decreasing dose for ≥28 days prior to Screening and receiving an equivalent to ≤10 mg prednisone for the 28 days immediately prior to Screening. Screening can begin before the 28 day washout is completed, but the washout period must be completed prior to collection of Screening blood samples. 4. Anemia: For Phase 1b: Hgb \