Collectively, these data suggest that, in patients with moderate-to-severe anemia and/or in need of RBC transfusions, outcomes—notably anemia benefits, including week 24 transfusion independence rates, onset and duration of transfusion independence, median transfusion rates through week 24, and mean Hb levels over time—are improved by switching to momelotinib rather than continuing ruxolitinib and using ESAs or other supportive therapies to manage anemia. The gene discussed is GSTM1; the disease is anemia (phenotype).