Eltrombopag Added to Standard Immunosuppressive Treatment as Front-Line Therapy for Severe Aplastic Anemia: Long-Term Outcomes of the Phase-3 Randomized Superiority EBMT-SAAWP RACE Study.

The RACE study (NCT02009747) compared horse antithymocyte globulin (hATG) plus cyclosporine A (CsA) ± eltrombopag as initial immunosuppressive treatment (IST) for severe aplastic anemia. Here we report the final 2-year analysis of this prospective randomized phase III study. One hundred ninety-seven treatment-naive patients were randomized to standard IST (hATG 40 mg/kg × 4 days and CsA 5 mg/kg/day; arm A; n = 101) or standard IST + eltrombopag at the dose of 150 mg/day (arm B; n = 96) from day +14 until 6 months (or 3 months, in case of complete response). The median follow-up was 23.2 months. The 2-year cumulative incidence of complete response was significantly superior in arm B (62.4% vs. 35.3%; p < 0.001). The 2-year overall survival (OS) was 86% in arm A and 91% in arm B (p = 0.081), with hazard ratio (HR), adjusted for age and disease severity, of 0.54 (p = 0.064). The 2-year disease-free survival (DFS) was 56% vs. 37% (adjusted HR = 0.49; p < 0.001), while event-free survival (EFS) was 48% vs. 32% (p < 0.001), with adjusted HR = 0.54 (p < 0.001), both significantly superior for arm B. The cumulative incidence of relapse was comparable in the two arms, while evolution to clinical paroxysmal nocturnal hemoglobinuria was 8% in arm A and 1% in arm B (p = 0.041). The risk of clonal evolution remained negligible, with one patient in arm A and two in arm B developing karyotypic abnormalities. The initial hematological response benefit of eltrombopag added to IST as front-line treatment of AA is associated with better 2-year OS, DFS, and EFS without increased risk of secondary myeloid malignancies.