Extended Dosing With Eltrombopag for Severe Aplastic Anemia
Condition: Severe Aplastic Anemia (SAA)
MeSH terms: Anemia; Anemia, Aplastic
Study type: Interventional
Phase: Phase 2

Summary: 
      Background:

      - Eltrombopag is a drug being tested for treating severe aplastic anemia. It can help improve
      blood counts in these patients. However, researchers do not know how long the drug can and
      should be taken for this type of anemia.

      Objectives:

      - To look at whether 6 months of treatment with eltrombopag can improve patient s blood
      counts.

      Eligibility:

      - Individuals at least 2 years of age who are taking eltrombopag for severe aplastic anemia.

      Design:

        -  Participants will take eltrombopag by mouth once a day for 6 months.

        -  Blood samples will be collected every 2 weeks for the first 6 months. Bone marrow
           samples will be collected at 3 and 6 months. These samples will look at the effects of
           the study drug on the marrow.

        -  Participants will continue to take the study drug for as long as it is effective and if
           the side effects are not severe.
    

Detailed description: 
      Severe aplastic anemia (SAA) is a life-threatening blood disease that can be successfully
      treated with immunosuppressive drug regimens or allogeneic stem cell transplantation.
      However, 20-40% of patients are ineligible for transplant due to lack of an appropriate
      donor, age, or comorbidities. Immunosuppression can be more broadly utilized, but about 1/3
      of patients do not respond to a single course of horse ATG and cyclosporine and have
      persistent severe cytopenias. Among patients who do respond to immunosuppression, responses
      may be partial, with persistent thrombocytopenia, neutropenia, and/or anemia. About 30% of
      responding patients either relapse or are dependent on continued cyclosporine administration.
      Patients with refractory severe cytopenias are at risk of dying from infection or bleeding,
      and they require regular platelet and/or red blood cell transfusions, which are expensive and
      inconvenient, Patients with refractory SAA are also at risk for progression to other
      hematologic disorders, including myelodysplasia and leukemia.

      Thrombopoietin (TPO) was first identified as the principal protein regulating platelet
      production, and it stimulates the proliferation of megakaryocytes and release of platelets.
      TPO was later shown to stimulate proliferation of more primitive bone marrow stem and
      progenitor cells in vitro and in animal models, suggesting it could have an impact of
      production of red and white blood cells as well as platelets.

      The 2nd generation oral small molecule TPO-agonist eltrombopag (Promacta ) has been shown to
      increase platelets in healthy subjects and in thrombocytopenic patients with chronic immune
      thrombocytopenic purpura (ITP) and hepatitis C virus (HCV)-infection. Eltrombopag has been
      well-tolerated in clinical trials, and unlike recombinant TPO, it does not induce
      autoantibodies. Eltrombopag received FDA accelerated approval on November 20, 2008 for the
      treatment of thrombocytopenia in patients with chronic immune (idiopathic) thrombocytopenic
      purpura who have had an insufficient response to corticosteroids, immunoglobulins, or
      splenectomy. In November 2012, FDA approval was received for hepatitis C associated
      thrombocytopenia.

      We conducted a pilot dose finding study in patients with severe aplastic anemia who had
      refractory thrombocytopenia following standard immunosuppressive therapy. Patients began at a
      dose of 50 mg/day and escalated every two weeks to a maximum dose of 150 mg/day. We reported
      that 11 of 25 patients (44%) achieved hematological response in at least one lineage
      following 12 weeks of dose-escalating eltrombopag therapy, with minimal toxicity. Responding
      patients as assessed at 12 weeks were invited to continue on drug in an extension phase. With
      a median follow-up of 27 months on drug, 7 eventually became tri-lineage responders. Nine
      became transfusion-independent for platelets (median increase in platelet count 34,000/micro
      l), six had improved hemoglobin levels (median increase of 3.8g/dL), including three
      previously dependent on red cell transfusions achieving transfusion-independence, and eight
      exhibiting increased neutrophil counts (median increase 590 cells/mico L). Serial bone marrow
      biopsies demonstrated normalization of tri-lineage hematopoiesis in responders, without
      increased fibrosis.

      In the previous study, response assessment occurred at 12 weeks, and patients not fulfilling
      response criteria at that time had the drug discontinued. Several patients began to have
      detectable changes in transfusion requirements or blood counts by 12 weeks, but did not
      fulfill response criteria by that time point and therefore had to discontinue eltrombopag.
      Other patients who barely met response criteria at 12 weeks showed very marked further
      improvements in blood counts in all lineages during the extension phase, in some cases not
      reaching maximal responses until one year after initiating eltrombopag. We hypothesize that a
      larger fraction of patients may respond if eltrombopag is continued for longer than 12 weeks.

      We, therefore propose a follow-up Phase 2 study giving eltrombopag treatment for 24 weeks
      prior to definitive response assessment, and initiating study medication at a fixed dose of
      150 mg/day (75 mg /day for individuals of East Asian ethnicity), given lack of toxicity at
      that dose in the prior study, and no evidence for response in any patient during dose
      escalation prior to reaching this dose. Responses will be assessed in all three lineages.
      Subjects with platelet, red cell, and/or neutrophil responses at 24 weeks may continue study
      medication (extended access) until they meet off study criteria.

      The primary objective is to assess the efficacy of 6 months of eltrombopag administration in
      improving bone marrow function in SAA patients with persistent severe cytopenias refractory
      to treatment with immunosuppressive treatment.

      Secondary objectives include assessment of relapse or clonal evolution, pre-treatment
      characteristics predicting response, and the impact of treatment and treatment response on
      quality of life.
    

Intervention name(s): Eltrombopag
Intervention type(s): Drug
Intervention description(s): Oral administration of eltrombopag 150mg/day (75 mg/day for East Asian ancestry) for 6 months
Other intervention name(s): Promacta
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Cytokine; Hematopoiesis; Autoimmunity; Thrombocytopenia; Neutropenia