Activity of eltrombopag in severe aplastic anemia

Abstract

Since the approval of horse antithymocyte globulin (ATG) decades ago, there was a long hiatus in therapies with activity in severe aplastic anemia (SAA). This scenario changed in 2014 when eltrombopag, a thrombopoietin receptor agonist, was approved for SAA after an insufficient response to initial immunosuppressive therapy (IST). The basis for this approval was the observation of single-agent activity of eltrombopag in this patient population, where 40% to 50% recovered blood counts at times involving >1 lineage. The achievement of transfusion independence confirmed the clinical benefit of this approach. Increase in marrow cellularity and CD34+ cells suggested a recovery to a more functioning bone marrow. Further in its development, eltrombopag was associated with standard horse ATG plus cyclosporine in first line, producing increases in overall (at about 90%) and complete response rates (at about 40%) and leading to transfusion independence and excellent survival. Interestingly, best results were observed when all drugs were started simultaneously. The cumulative incidence of clonal cytogenetic abnormalities to date has compared favorably with the vast experience with IST alone in SAA. Longer follow-up will help in define these long-term risks. In this review, the development of eltrombopag in SAA will be discussed.

Conflict of interest statement

Conflict-of-interest disclosure: P.S. is on the Board of Directors or an advisory committee for Novartis and has been affiliated with the Speaker’s Bureau for Pfizer and Novartis.

© 2018 by The American Society of Hematology. All rights reserved.

Figures

Figure 1.

Different proposed mechanisms by which eltrombopag is improving hematopoiesis in aplastic anemia. IFNγ, interferon-γ; TGFβ, transforming growth factor-β.