CR indicates complete response; PR, partial response; GI, gastrointestinal; Xs, clinical improvement for splenomegaly (> 50% reduction in palpable component if > 10 cm below left costal margin); LFTs, liver function tests; DVTs, deep vein thrombosis; Xa, clinical improvement for anemia (> 2 g/dL improvement durable > 2 months, or becoming transfusion independent).

*IWG-MRT responses.