Importantly, the use of the activin receptor ligand traps Sotatercept (ACE-011) or ACE-536 in humans, or RAP-011 (the mouse equivalent) leads to efficient inhibition of GDF11 signaling, and restoration of hematologic parameters, suggesting that GDF11 is a major component of the ineffective erythropoiesis in thalassemia. Here, GDF11 is linked to thalassemia.