A Pilot Study of the Thrombopoietin-Receptor Agonist Eltrombopag in Refractory Aplastic Anemia Patients

Summary

Severe aplastic anemia (SAA) is a life-threatening blood disease which can be effectively treated with immunosuppressive drug regimens or allogeneic stem cell transplantation. However, 20-40% of patients without transplant options do not respond to immunosuppressive therapies, and have persistent severe cytopenias, requiring regular platelet transfusions, which are expensive and inconvenient, and are a risk for further serious bleeding complications. Thrombopoietin (TPO) is the principal endogenous regulator of platelet production and also stimulates hematopoietic stem and progenitor cells. A small molecule oral TPO-agonist, eltrombopag has been shown to increase platelets in healthy subjects and in patients with immune thrombocytopenic purpura (ITP), and received FDA approval in 2008 for the treatment of thrombocytopenia in ITP. This Phase 2, non-randomized pilot study of eltrombopag in aplastic anemia patients with immunosuppressive therapy refractory thrombocytopenia will test the safety and potential efficacy of eltrombopag treatment patients with refractory thrombocytopenia following immunosuppression for aplastic anemia. Subjects will initiate study medication at an oral dose of 50 mg/day, which will be increased up to 150 mg/day as clinically indicated to the lowest dose that maintains a stable platelet count 20,000/(micro)L above baseline while maximizing tolerability. Response will be assessed at 3-4 months. Platelet response is defined as platelet count increases to 20,000/L above baseline at three months. or stable platelet counts with transfusion independence for a minimum of 8 weeks. Erythroid response for subjects with a pretreatment hemoglobin of less than 9 g/dL will be defined as an increase in hemoglobin by greater than or equal to 1.5g/dL without packed red blood cell (PRBC) transfusion support, or a reduction in the units of transfusions by an absolute number of at least 4 PRBC transfusions for eight consecutive weeks compared with the pretreatment transfusion number in the previous 8 weeks. Neutrophil response will be defined in those with a pretreatment absolute neutrophil count (ANC) of less than 0.5 times 10(9)/L as at least a 100 percent increase or an absolute increase greater than 0.5 times 10(9)/L. Subjects with response at 3-4 months may continue study medication (extended access) until they meet an off study criteria. The primary objective is to assess the safety and efficacy of the oral thrombopoietin receptor agonist (TPO-R agonist) eltrombopag in aplastic anemia patients with immunosuppressive-therapy refractory thrombocytopenia. Secondary objectives include the analysis of the incidence and severity of bleeding episodes, and the impact on quality of life.

Timeline

Start

2009-05-29

Primary completion

2013-05-07

Completion

2018-04-24

Publications

• Background Young NS, Calado RT, Scheinberg P. Current concepts in the pathophysiology and treatment of aplastic anemia. Blood. 2006 Oct 15;108(8):2509-19. doi: 10.1182/blood-2006-03-010777. Epub 2006 Jun 15.
• Background Emmons RV, Reid DM, Cohen RL, Meng G, Young NS, Dunbar CE, Shulman NR. Human thrombopoietin levels are high when thrombocytopenia is due to megakaryocyte deficiency and low when due to increased platelet destruction. Blood. 1996 May 15;87(10):4068-71.
• Results Desmond R, Townsley DM, Dumitriu B, Olnes MJ, Scheinberg P, Bevans M, Parikh AR, Broder K, Calvo KR, Wu CO, Young NS, Dunbar CE. Eltrombopag restores trilineage hematopoiesis in refractory severe aplastic anemia that can be sustained on discontinuation of drug. Blood. 2014 Mar 20;123(12):1818-25. doi: 10.1182/blood-2013-10-534743. Epub 2013 Dec 17.
• Results Olnes MJ, Scheinberg P, Calvo KR, Desmond R, Tang Y, Dumitriu B, Parikh AR, Soto S, Biancotto A, Feng X, Lozier J, Wu CO, Young NS, Dunbar CE. Eltrombopag and improved hematopoiesis in refractory aplastic anemia. N Engl J Med. 2012 Jul 5;367(1):11-9. doi: 10.1056/NEJMoa1200931.
• Winkler T, Fan X, Cooper J, Desmond R, Young DJ, Townsley DM, Scheinberg P, Grasmeder S, Larochelle A, Desierto M, Valdez J, Lotter J, Wu C, Shalhoub RN, Calvo KR, Young NS, Dunbar CE. Treatment optimization and genomic outcomes in refractory severe aplastic anemia treated with eltrombopag. Blood. 2019 Jun 13;133(24):2575-2585. doi: 10.1182/blood.2019000478. Epub 2019 Apr 16.

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