This study is examining a new medicine called **INCB000928** for people with a condition called **myelofibrosis (MF)**, which is a type of disease where the bone marrow does not make enough healthy blood cells, leading to anemia (low red blood cells). Some participants will take **INCB000928** alone, and others will take it with another medicine called **ruxolitinib**. The study has two parts where they will try different doses to find out which one works best and is safe. To join, you must have MF with anemia or need frequent blood transfusions, and can't have had certain treatments before.

• The study has two parts: dose escalation and expansion.
• Participants must not have had certain treatments recently.
• Participants must be able to avoid pregnancy during the study.

People with MF often need regular blood transfusions because of low hemoglobin (Hgb) levels. This study seeks to help those who have tried other treatments without success. If you participate, you'll need to meet certain criteria and might be on the study for several weeks. Always discuss with your doctor to see if this study could be right for you.