This clinical trial is focused on studying a condition called Myelofibrosis, which is a type of blood cancer that affects the bone marrow. The study is exploring the use of a treatment called KER-050, which is being tested both on its own and in combination with another medication called Ruxolitinib. Ruxolitinib is also known by its code name INCB018424. The purpose of the study is to evaluate the safety and effectiveness of these treatments in people with Myelofibrosis who also have anemia, a condition where there is a lack of healthy red blood cells.

The study is divided into different parts. Initially, participants will receive increasing doses of KER-050 to determine the safest and most effective dose. This phase will help understand how well participants tolerate the treatment. In the next phase, the study will expand to include more participants to further assess the safety of the chosen dose. There is also a long-term extension part of the study to evaluate the ongoing safety of KER-050, with or without Ruxolitinib, over a longer period.

Participants in the study will receive either KER-050 alone or in combination with Ruxolitinib. The study will monitor the participants for any side effects and measure how the treatments affect their condition. The study aims to find out if these treatments can help manage Myelofibrosis symptoms, improve blood cell counts, and reduce the need for blood transfusions. The study will also look at changes in spleen size using imaging techniques like CT or MRI. The trial is expected to continue until 2029, providing valuable information on the long-term effects of these treatments.