In contrast, most patients in the present analysis received full daily doses of momelotinib, which not only provides spleen and symptom benefits through inhibition of JAK1/JAK2 but directly addresses anemia in myelofibrosis through inhibition of ACVR1, leading to increased serum iron availability and erythropoiesis [3, 20]. Here, ACVR1 is linked to anemia (phenotype).