(A) In acquired aplastic anemia, cytotoxic T lymphocytes (CTLs) attack HSPCs, leading to bone marrow aplasia. Elevated levels of inflammatory cytokines cause further bone marrow suppression, in part by interferon-γ (IFN-γ)–mediated inhibition of the endogenous thrombopoietin (TPO) signaling through the c-MPL receptor. A small molecule thrombopoietin mimetic eltrombopag is not affected by IFN-γ and can stimulate c-MPL signaling leading to HSPC recovery. (B) Extending the course of eltrombopag therapy from 12 to 24 weeks in patients with rSAA increased hematologic responses from 40% to 50% and nearly doubled the rate of multilineage hematologic responses. Eighteen percent of rSAA patients treated with eltrombopag developed chromosomal abnormalities within the 24-week study period.