Eltrombopag With Standard Immunosuppression for Severe Aplastic Anemia

Background: Severe aplastic anemia is a rare and serious blood disorder. It happens when the immune system starts to attack the bone marrow cells. This causes the bone marrow to stop making red blood cells, platelets, and white blood cells. Standard treatment for this disease is horse-ATG and cyclosporine, which suppress the immune system and stop it from attacking the bone marrow. However, this treatment does not work in all people. Some people still have poor blood cell counts even after treatment. Eltrombopag is a drug designed to mimic a protein in the body called thrombopoietin. It helps the body to make more platelets. It may also cause the body to make more red and white blood cells. Studies have shown that eltrombopag may be useful when added to standard treatment for severe aplastic anemia. It may help improve poor blood cell counts. Objectives: - To test the safety and effectiveness of adding eltrombopag to standard immunosuppressive therapy for severe aplastic anemia. Eligibility: - Individuals at least 2 years of age who have severe aplastic anemia that has not yet been treated. Design: Participants will be screened with a physical exam, medical history, and blood tests. Blood and urine samples will be collected. Participants will start treatment with horse-ATG and cyclosporine. Treatment will be given according to the standard of care for the disease. Cohort 1: After 14 days, participants will start taking eltrombopag. They will take eltrombopag for up to 6 months. Cohort 2: After 14 days, participants will start taking eltrombopag. They will take eltrombopag for up to 3 months. Cohort 3 and Extension Cohort: Participants will start taking eltrombopag on Day 1. They will take eltrombopag for up to 6 months. Participants may receive other medications to prevent infections during treatment. Treatment will be monitored with frequent blood tests. Participants will also fill out questionnaires about their symptoms and their quality of life.

Severe aplastic anemia (SAA) is a life-threatening bone marrow failure disorder characterized by pancytopenia and a hypocellular bone marrow. Allogeneic bone marrow transplantation offers the opportunity for cure in younger patients, but most are not suitable candidates for transplantation due to advanced age or lack of a histocompatible donor. Comparable long-term survival in SAA is attainable with immunosuppressive treatment with horse anti-thymocyte globulin (h-ATG) and cyclosporine (CsA). However, of those patients treated with h-ATG/CsA, one quarter to one third will not respond, and 30-40% of responders relapse. The majority of the hematologic responses observed following initial h-ATG/CsA are partial, with only a few patients achieving normal blood counts. Furthermore, analysis of our own extensive clinical data suggests that poor blood count responses to a single course of ATG (non-robust responders), even when transfusion-independence is achieved, predicts a worse prognosis than when robust hematologic improvement is achieved (protocol 90-H-0146). The explanation for partial recovery and relapse are not fully understood, but incomplete elimination of auto-reactive T cells and insufficient stem cell reserve are both possible. Furthermore, 10-15% of SAA patients treated with standard immunosuppression will develop an abnormal karyotype in follow-up, with monosomy 7 being most common, which portends progression to myelodysplasia and leukemia. In contrast, malignant clonal evolution is rare in complete responders to immunosuppression. Although horse ATG/CsA represented a major advance in the treatment of SAA, refractoriness, incomplete responses, relapse, and clonal evolution limit the success of this modality. Thus, newer regimens are needed to address these limitations, and provide a better alternative to stem cell transplantation. One approach to augment the quality of hematologic responses is to improve underlying stem cell function. Previous attempts to improve responses in SAA with hematopoietic cytokines including erythropoietin, G-CSF, and stem cell factor, have failed. Thrombopoietin (TPO) is the principal endogenous regulator of platelet production. In addition, TPO also has stimulatory effects on more primitive multilineage progenitors and stem cells in vitro and in animal models. Eltrombopag (Promacta ), an oral 2nd generation small molecule TPO-agonist, is currently approved for treatment of chronic immune thrombocytopenic purpura (ITP), chronic hepatitis C-associated thrombocytopenia, and severe aplastic anemia who have had an insufficient response to immunosuppressive therapy. Eltrombopag increases platelets in healthy subjects and in thrombocytopenic patients with chronic ITP and hepatitis C virus (HCV) infection. Our Branch recently completed a pilot study of eltrombopag in refractory SAA. We saw encouraging clinical results in a cohort of patients who have failed on average two prior immunosuppressive regimens (Olnes et al. ASH Annual Meeting Abstracts, San Diego, CA, 2011, oral presentation and N Engl J Med 2012;367:11-9.1). Of the twenty-five SAA patients treated with eltrombopag by mouth for three months, eleven (44%) patients met protocol criteria of clinically meaningful hematologic responses, without significant toxicity. Nine patients demonstrated an improvement in thrombocytopenia (>20k/ L increase or transfusion independence), hemoglobin improved in two patients (>1.5g/dL or achieved transfusion independence, and four patients had a significant response in their neutrophil count. When responders continued the drug beyond three months, the hematologic response to eltrombopag increased; a trilineage response was observed in four patients, and a bilineage response occurred in another four, with median follow-up of 13 months. These results suggest that stem cell depletion, a major component of the pathophysiology of SAA, might be directly addressed by eltrombopag administration. The aim of the current study would be to improve the hematologic response rate and its quality, as well as prevent late complications such as relapse and clonal progression, by addition of eltrombopag to standard immunosuppressive therapy. This trial will evaluate the safety and efficacy of combining eltrombopag with standard hATG/CSA as first line therapy in patients with SAA. The primary endpoint will be the rate of complete hematologic response at six months. Secondary endpoints are relapse, robust hematologic blood count recovery at 3, 6, and 12 months, survival, clonal evolution to myelodysplasia and leukemia, marrow stem cell content and hematological response of relapse patients that re-start treatment.

Receive horse ATG days 1- 4, receive CsA day 1 to month 6 at higher dose, then reduced dose for 18months, and receive eltrombopag day 1 to month 6

Receive horse ATG days 1- 4, receive CsA day 1 to month 6 at higher dose, then reduced dose for 18 months, and receive eltrombopag day 1 to month 6

hATG (standard of care) administered for 4 days, CsA (standard of care) administered starting day 1 for 6 months, eltrombopag (experimental) administered Day 14 to month 6

hATG (standard of care) administered for 4 days, CsA (standard of care) administered starting day 1 for 6 months, eltrombopag (experimental) administered Day 14 to month 3

hATG (standard of care) administered for 4 days, CsA (standard of care) administered starting day 1 for 6 months at higher dose, then reduced dose for 18 months, eltrombopag (experimental) administered Day 1 to month 6

Receive horse ATG days 1- 4, receive CsA day 1 to month 6 at higher dose, then reduced dose for 18 months, and receive eltrombopag day 1 to month 6

Rate of Response at 3 and 12 Months Then Yearly; Rate of Relapse; Rate of Clonal Evolution to PNH, MDS and AML; Rate of Survival; Rate of Response for Relapse Subjects That Re-start Treatment and Effects of CsA Dose Starting at Month 6 to Month 24.

Secondary endpoints will also be evaluated for the study to include: (a) hematological response at 3 and 12 months and yearly thereafter; (b) relapse (c) clonal evolution to PNH, clonal chromosomal population in bone marrow, myelodysplasia by morphology, or acute leukemia; (d) survival; (e) health-related quality of life; (f) hematological response of relapse subjects that re-start treatment; and (g) affects of a 2.0mg/kg/day CsA dose starting month 6 for 18 months until month 24 on the rate of relapse of subjects deemed responders at month 6.

-INCLUSION CRITERIA: Severe aplastic anemia characterized by Bone marrow cellularity less than 30 percent (excluding lymphocytes) AND At least two of the following: Absolute neutrophil count less than 500/microL Platelet count less than 20,000/microL Absolute reticulocyte count less than 60,000/microL Age greater than or equal to 2 years old Weight greater than 12 kg EXCLUSION CRITERIA: Known diagnosis of Fanconi anemia Evidence of a clonal disorder on cytogenetics performed within 12 weeks of study entry. Patients with super severe neutropenia (ANC less than 200 /microL) will not be excluded initially if cytogenetics are not available or pending. If evidence of a clonal disorder consistent with myelodysplasia is later identified, the patient will go off study. Prior immunosuppressive therapy with any ATG, alemtuzumab, or high dose cyclophosphamide SGOT or SGPT >5 times the upper limit of normal Subjects with known liver cirrhosis in severity that would preclude tolerability of cyclosporine and eltrombopag as evidenced by albumin < 35g/L Hypersensitivity to eltrombopag or its components Infection not adequately responding to appropriate therapy Moribund status or concurrent hepatic, renal, cardiac, neurologic, pulmonary, infectious, or metabolic disease of such severity that it would preclude the patient s ability to tolerate protocol therapy, or that death within 7-10 days is likely Potential subjects with cancer who are on active chemotherapeutic treatment or who take drugs with hematological effects will not be eligible Current pregnancy, or unwillingness to take oral contraceptives or use a barrier method of birth control or practice abstinence to refrain from pregnancy if of childbearing potential during the course of this study Inability to understand the investigational nature of the study or to give informed consent or does not have a legally authorized representative or surrogate that can provide informed consent.

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.

Zoumbos NC, Gascon P, Djeu JY, Trost SR, Young NS. Circulating activated suppressor T lymphocytes in aplastic anemia. N Engl J Med. 1985 Jan 31;312(5):257-65. doi: 10.1056/NEJM198501313120501.

Young NS, Leonard E, Platanias L. Lymphocytes and lymphokines in aplastic anemia: pathogenic role and implications for pathogenesis. Blood Cells. 1987;13(1-2):87-100.

Townsley DM, Scheinberg P, Winkler T, Desmond R, Dumitriu B, Rios O, Weinstein B, Valdez J, Lotter J, Feng X, Desierto M, Leuva H, Bevans M, Wu C, Larochelle A, Calvo KR, Dunbar CE, Young NS. Eltrombopag Added to Standard Immunosuppression for Aplastic Anemia. N Engl J Med. 2017 Apr 20;376(16):1540-1550. doi: 10.1056/NEJMoa1613878.

Zaimoku Y, Patel BA, Adams SD, Shalhoub R, Groarke EM, Lee AAC, Kajigaya S, Feng X, Rios OJ, Eager H, Alemu L, Quinones Raffo D, Wu CO, Flegel WA, Young NS. HLA associations, somatic loss of HLA expression, and clinical outcomes in immune aplastic anemia. Blood. 2021 Dec 30;138(26):2799-2809. doi: 10.1182/blood.2021012895.

Patel BA, Groarke EM, Lotter J, Shalhoub R, Gutierrez-Rodrigues F, Rios O, Quinones Raffo D, Wu CO, Young NS. Long-term outcomes in patients with severe aplastic anemia treated with immunosuppression and eltrombopag: a phase 2 study. Blood. 2022 Jan 6;139(1):34-43. doi: 10.1182/blood.2021012130.

Zaimoku Y, Patel BA, Shalhoub R, Groarke EM, Feng X, Wu CO, Young NS. Predicting response of severe aplastic anemia to immunosuppression combined with eltrombopag. Haematologica. 2022 Jan 1;107(1):126-133. doi: 10.3324/haematol.2021.278413.

Groarke EM, Patel BA, Gutierrez-Rodrigues F, Rios O, Lotter J, Baldoni D, St Pierre A, Shalhoub R, Wu CO, Townsley DM, Young NS. Eltrombopag added to immunosuppression for children with treatment-naive severe aplastic anaemia. Br J Haematol. 2021 Feb;192(3):605-614. doi: 10.1111/bjh.17232. Epub 2021 Jan 7. Erratum In: Br J Haematol. 2022 Jun;197(5):640-641.

Giudice V, Wu Z, Kajigaya S, Fernandez Ibanez MDP, Rios O, Cheung F, Ito S, Young NS. Circulating S100A8 and S100A9 protein levels in plasma of patients with acquired aplastic anemia and myelodysplastic syndromes. Cytokine. 2019 Jan;113:462-465. doi: 10.1016/j.cyto.2018.06.025. Epub 2018 Jun 27.

Giudice V, Banaszak LG, Gutierrez-Rodrigues F, Kajigaya S, Panjwani R, Ibanez MDPF, Rios O, Bleck CK, Stempinski ES, Raffo DQ, Townsley DM, Young NS. Circulating exosomal microRNAs in acquired aplastic anemia and myelodysplastic syndromes. Haematologica. 2018 Jul;103(7):1150-1159. doi: 10.3324/haematol.2017.182824. Epub 2018 Apr 19.

Giudice V, Feng X, Lin Z, Hu W, Zhang F, Qiao W, Ibanez MDPF, Rios O, Young NS. Deep sequencing and flow cytometric characterization of expanded effector memory CD8+CD57+ T cells frequently reveals T-cell receptor Vbeta oligoclonality and CDR3 homology in acquired aplastic anemia. Haematologica. 2018 May;103(5):759-769. doi: 10.3324/haematol.2017.176701. Epub 2018 Feb 1.

Hosokawa K, Muranski P, Feng X, Keyvanfar K, Townsley DM, Dumitriu B, Chen J, Kajigaya S, Taylor JG, Hourigan CS, Barrett AJ, Young NS. Identification of novel microRNA signatures linked to acquired aplastic anemia. Haematologica. 2015 Dec;100(12):1534-45. doi: 10.3324/haematol.2015.126128. Epub 2015 Sep 9.