Inclusion Criteria:

   - Participants with MF who are transfusion-dependent or present with symptomatic anemia,
   defined as follows:

      1. Anemia: An Hgb value < 10 g/dL demonstrated during screening recorded on 3
      separate occasions with at least 7 days between measurements (Note: RBC
      transfusion must be at least 2 weeks before the Hgb measurement during
      screening).

      2. Transfusion-dependent: Participant has received at least 4 units of RBC
      transfusions during the 28 days immediately preceding Cycle 1 Day 1 OR has
      received an average of at least 4 units of RBC transfusions in the 8 weeks
      immediately preceding Cycle 1 Day 1, for an Hgb level of < 8.5 g/dL, in the
      absence of bleeding or treatment-induced anemia. In addition, the most recent
      transfusion episode must have occurred in the 28 days before Cycle 1 Day 1.

   - ECOG performance status score of the following:

      1. 0 or 1 for the dose-escalation stages.

      2. 0, 1, or 2 for the dose-expansion stage.

   - Life expectancy is greater than 6 months

   - Agreement to avoid pregnancy or fathering children.

   - Ineligible to receive or have not responded to available therapies for anemia such as
   ESAs.

   - For TGA:

   - Participants previously treated with JAK inhibitors for at least 12 weeks.

   - Participants with intermediate-2 or high DIPSS MF according to IWG-MRT criteria.

   - For TGB:

   - Participants must have been on a therapeutic and stable regimen of ruxolitinib for at
   least 12 consecutive weeks immediately preceding the first dose of study treatment.

   - Participants with intermediate-1, intermediate-2, or high DIPSS MF according to
   IWG-MRT criteria.

   - For TGC:

   - Participants must be JAK inhibitor treatment naive (no prior treatment with any JAK
   inhibitor) and have an indication for initiation of ruxolitinib treatment.

   - Participants with intermediate-1, intermediate-2, or high DIPSS MF according to
   IWG-MRT criteria.

Exclusion Criteria:

   - Undergone any prior allogenic or autologous stem cell transplantation or a candidate
   for such transplantation.

   - Any prior chemotherapy, immunomodulatory drug therapy, immunosuppressive therapy,
   biological therapy, endocrine therapy, targeted therapy, antibody or hypomethylating
   agent to treat the participant's disease, with the exception of ruxolitinib for TGB
   only, within 5 half-lives or 28 days (whichever is shorter) before the first dose of
   study treatment.

   - Laboratory Values outside of protocol defined range at screening.