Responses were higher in those patients with SF3B1 mutations (77% vs. 40%, respectively), leading to a phase 3 trial focused on LR-MDS patients with ≥15% ring sideroblast (RS) (or ≥5% RS plus SF3B1 mutation), who were transfusion-dependent with disease refractory to or unlikely to respond to ESA (MEDALIST trial). Here, SF3B1 is linked to myelodysplastic syndrome.