Momelotinib is a medication being studied for its potential to help people with a type of bone marrow disorder called myelofibrosis. This condition can occur on its own or after other blood disorders like polycythemia vera or essential thrombocythemia. The trial aims to provide extended access to this medication for patients who are already receiving it and to monitor its long-term safety.

Primary Myelofibrosis – A rare bone marrow disorder where the marrow is replaced by fibrous tissue, leading to severe anemia, weakness, and fatigue. Over time, the spleen and liver may enlarge due to the body’s attempt to produce blood cells outside the bone marrow. Patients often experience symptoms like night sweats, fever, and weight loss. The disease progresses slowly, but the fibrous tissue can eventually lead to bone marrow failure. Blood cell production becomes increasingly impaired, causing complications related to low blood counts.

Post-polycythemia Vera Myelofibrosis – This condition arises as a progression from polycythemia vera, a disorder where the body produces too many red blood cells. Over time, the bone marrow becomes fibrotic, leading to symptoms similar to primary myelofibrosis, such as anemia and an enlarged spleen. Patients may experience fatigue, night sweats, and weight loss. The disease progression involves increasing difficulty in producing blood cells, leading to various complications. The fibrotic transformation can cause significant changes in blood cell counts and function.

Post-essential Thrombocythemia Myelofibrosis – This disease develops from essential thrombocythemia, a condition characterized by excessive platelet production. As the disease progresses, the bone marrow becomes fibrotic, resulting in symptoms like anemia, fatigue, and an enlarged spleen. Patients may also experience night sweats and weight loss. The progression involves a gradual decline in the bone marrow’s ability to produce blood cells effectively. This leads to complications associated with low blood counts and impaired blood cell function.