Nationwide survey on the use of eltrombopag in patients with severe aplastic anemia: a report on behalf of the French Reference Center for Aplastic Anemia

[Acquired severe aplastic anemia in emerging countries: Management from allogeneic hematopoietic cell transplantation indication until post-transplant follow-up SFGM-TC]

Management of acquired aplastic anemia (AA) in emerging countries depends on the means of prognostic stratification, treatment and logistics available. During the 13th annual harmonization workshop of the francophone Society of bone marrow transplantation and cellular therapy (SFGM-TC), a designated working group reviewed the literature in order to elaborate unified guidelines for allogeneic hematopoietic cell transplantation (Allo-HCT) in this disease. In terms of practice, the conclusions are as follows; The use of anti-tymocyte globuline (ATG) is mainly from rabbit and very little from horse. Access to bone marrow graft, total body irradiation, and the international unrelated donor registries is limited, which justifies the use of peripheral blood stem cells, chemotherapy-based conditioning, and related alternative donor. The workshop recommends matched sibling allo-HCT in all patients aged less than 40 years with acquired severe or very severe AA. For patients aged over than 40 years, or who lack an HLA-identical donor, treatment with the combination of cyclosporin, horse ATG, eltrombopag or cyclosporine, eltrombopag is recommended. If horse ATG and eltrombopag are not available, matched sibling allo-HCT may be indicated as first-line therapy in patients aged between 40-60 years, and good performance status. Although, in patients who have failed immunosuppressive treatments and thrombopoietin agonists, and in the absence of HLA-matched donor, a haplo-identical allo-HCT with modified Baltimore conditioning is recommended.

Diagnosis and management of acquired aplastic anemia in childhood. Guidelines from the Marrow Failure Study Group of the Pediatric Haemato-Oncology Italian Association (AIEOP)

Acquired aplastic anemia (AA) is a rare heterogeneous disorder characterized by pancytopenia and hypoplastic bone marrow. The incidence is 2-3 per million population per year in the Western world, but 3 times higher in East Asia. Survival in severe aplastic anemia (SAA) has improved significantly due to advances in hematopoietic stem cell transplantation (HSCT), immunosuppressive therapy, biologic agents, and supportive care. In SAA, HSCT from a matched sibling donor (MSD) is the first-line treatment. If a MSD is not available, options include immunosuppressive therapy (IST), matched unrelated donor, or haploidentical HSCT. The purpose of this guideline is to provide health care professionals with clear guidance on the diagnosis and management of pediatric patients with AA. A preliminary evidence-based document prepared by a group of pediatric hematologists of the Bone Marrow Failure Study Group of the Italian Association of Pediatric Hemato-Oncology (AIEOP) was discussed, modified and approved during a series of consensus conferences that started online during COVID 19 and continued in the following years, according to procedures previously validated by the AIEOP Board of Directors.

Comparison of efficacy of eltrombopag combined with immunosuppression in the treatment of severe aplastic anemia and very severe aplastic anemia: real-world data and evidence

Eltrombopag combined with immunosuppressive therapy (IST) was superior to IST alone for severe aplastic anemia (SAA) in the previous studies. But in China, horse antithymocyte globulin (hATG) is not available, instead, we use rabbit ATG (rATG). Here, we compared the efficacy and safety of IST (rATG combined with cyclosporine) combined with or without eltrombopag for the first-line treatment of SAA and very severe aplastic anemia (VSAA). A total of 371 patients in ten institutions in China from April 1, 2017 to December 1, 2022 were enrolled. The overall response (OR) rate at 3 months (54.2% vs. 41%; P = 0.046), the complete response (CR) (31.3% vs. 19.4%; P = 0.041) and OR (78.3% vs. 51.1%; P < 0.0001) rates at 6 months were significantly higher with IST combined with eltrombopag than with IST alone in SAA patients. While in VSAA patients, the addition of eltrombopag to IST only increased the CR rate at 6 months (29.8% vs. 9.43%; P = 0.010). Liver injury increased significantly in groups treated with IST combined with eltrombopag (P < 0.05). Serious treatment-related toxicities were similar (P > 0.05). In patients with SAA, 3-year failure-free survival (FFS) of eltrombopag combined with IST group was significantly higher than that of IST group (70.7 ± 5.3% vs. 50.3 ± 3.9%; P = 0.007). In patients with VSAA, the addition of eltrombopag significantly improved 3-year overall survival (OS) (82.2 ± 5.7% vs. 57.3 ± 7.2%; P = 0.020). Our findings suggested that IST combined with eltrombopag could improve the hematological recovery of newly diagnosed SAA without increasing severe toxicities. But in VSAA, the addition of eltrombopag seemed to show no other improvement to efficacy except the CR rate at 6 months.

A Systematic Review and Meta-Analysis of Eltrombopag Efficacy Combined With Immunosuppressive Drugs in Treatment of Severe Aplastic Anemia

Severe aplastic anemia (SAA) is a life-threatening disorder with high mortality. The only curative treatment is hematopoietic stem cell transplantation (HSCT), but it is mainly for young patients with suitable donors. The alternative is immunosuppressive therapy (IST), which can improve blood counts in about 58% of patients, but many relapse after discontinuation. Recently, eltrombopag, a thrombopoietic receptor agonist, was tested. As a single drug, it improved blood counts in 40-50% of patients. However, combining eltrombopag and IST proved more effective and safer. A review of 20 randomized controlled trials with 2,469 patients showed that the group receiving eltrombopag and IST had a significantly higher overall response rate (86% vs. 74%) after six months. After two years, 54% of the experimental group had relapsed compared to 39% in the control group. Despite this, eltrombopag tends to increase relapse rates over time. In conclusion, combining eltrombopag with IST is a superior treatment for SAA.

Urinary schistosomiasis and anemia among school-aged children from southwestern Nigeria

Schistosomiasis and anemia, are one of the leading global public health problem among children between age 5 and 14 years in marginalized settings. In this study, we provide prevalence and intensity data for both conditions in three southwestern states of Nigeria, where such are lacking. Epidemiological assessment involving parasitological analysis of urine and blood samples was conducted among 1783 consenting school-aged children in Ondo, Osun, Ekiti States of Nigeria. Participants' age and sex data were obtained using field forms, and statistical analysis was performed in R software with a significance level of 95%. An overall prevalence of 26.8% and 29.5% was recorded for urinary schistosomiasis and anemia, respectively. Prevalence varied by location with (40.3% and 29.8%) in Ondo (34.4% and 37.5%) in Osun and (13.4% and 20.9%) in Ekiti for urinary schistosomiasis and anemia, respectively (p=0.00). Schistosoma infections were found among males (28.7%, p=0.05) and children between the age 9-11 years (30.0%, p=0.01). About 36% of children with anemia was also infected with schistosomiasis. Children who were positive for schistosomiasis (OR:1.51; 95% CI: 1.19, 1.93; p=0.001) and between the age category 15-16 years, (OR:1.86; 95% CI: 1.12, 3.09; p<0.05) were twice likely to become anemic. Our findings have shown that children infected with schistosomiasis are twice likely to become anemic than those without infection. It is important to complement ongoing MDA programmes targeted at schistosomiasis with nutrition intervention programs for example micronutrient supplementation for better impact and cost-effectiveness.

Conditional survival and standardized mortality ratios of patients with severe aplastic anemia surviving at least one year after hematopoietic cell transplantation or immunosuppressive therapy

Immunosuppressive treatment (IST) and hematopoietic cell transplant (HCT) are standard therapies for severe aplastic anemia (SAA). We report on conditional survival and standardized mortality ratios (SMR), which compare the mortality risk with the general population adjusted for age, gender, and race/ethnicity, in patients with SAA alive for at least 12 months after treatment with IST or HCT between 2000 and 2018. Given changes to treatment regimens and differences in length of follow-up, two treatment periods were defined a priori: 2000-2010 and 2011-2018. The SMR of patients treated during the period 2000-2010 and who survived one year were 3.50 (95% confidence interval [CI]: 2.62-4.58), 4.12 (95% CI: 3.20-5.21), and 8.62 (95% CI: 6.88-10.67) after IST, matched related donor HCT, and alternative donor HCT, respectively. For the period 2011-2018, the corresponding SMR were 2.89 (95% CI: 1.54-4.94), 3.12 (95% CI: 1.90-4.82), and 4.75 (95% CI: 3.45-6.38), respectively. For IST patients, their mortality risk decreased over time, and became comparable to the general population by five years. For patients who underwent HCT during 2000-2010 and 2011-2018, their mortality risk became comparable to the general population after ten years and after five years, respectively. Thus, 1-year survivors after IST or HCT can expect their longevity beyond five years to be comparable to that of the general US population.

Comparison of eltrombopag and avatrombopag in the treatment of refractory/relapsed aplastic anemia: a single-center retrospective study in China

Background

Eltrombopag (ELT), a thrombopoietin receptor agonist (TPO-RA), has been approved for relapsed/refractory aplastic anemia (AA). However, data on avatrombopag (AVA), another TPO-RA, are limited, and the comparisons between the two TPO-RAs are lacking.

Objectives

We aimed to compare the efficacy and safety between ELT and AVA in relapsed/refractory AA patients.

Design

In this retrospective study, patients with relapsed/refractory AA who had been treated with ELT (N = 45) or AVA (N = 30) alone and had compatible baseline hematological parameters were compared.

Methods

Data from patients diagnosed with acquired AA were retrospectively collected. All patients were refractory/relapsed to standard immunosuppressive therapy (IST) for at least 6 months before ELT or AVA. Patients had to be treated with ELT or AVA alone for at least 6 months before evaluation if they did not respond. Baseline characteristics, overall response (OR), complete response (CR), relapse, adverse events, and factors that may affect efficacy were analyzed.

Results

Of the 75 patients enrolled, 45 received ELT and 30 received AVA. Patients with AVA had a higher percentage of abnormal liver or renal function than those with ELT (p = 0.036). No significant difference was found in the OR/CR rate in the first/second/third/sixth month between the two cohorts (p > 0.05). Patients treated with AVA had a shorter median time to response than those treated with ELT (p = 0.012) and had a higher platelet level in the second month (p = 0.041). AVA had fewer adverse events than ELT (p = 0.046). Under compatible follow-up time (p = 0.463), no difference was found between the ELT and AVA cohorts in relapse (p = 1.000) or clone evolution (p = 0.637). No predictive factors for OR and CR in the sixth month were found for either ELT or AVA.

Conclusion

With worse liver or renal function, AVA had a similar OR/CR rate but a shorter median time to response and fewer adverse events for patients with relapsed/refractory AA.

Idiopathic Aplastic anemia: Indian Perspective

Aplastic anemia (AA) is a rare immunologically mediated bone marrow failure syndrome, characterized by progressive loss of hematopoietic stem cells resulting in peripheral pancytopenia. Elaborative investigation including molecular tests is required to exclude inherited bone marrow failure syndrome (IMBFS) as the treatment and prognosis vary dramatically between them. Haematopoietic stem cell transplant with a fully matched sibling donor (MSD-HSCT) is still the only curative treatment. Management of AA is a real-time challenge in India, because of the delay in the diagnosis, lack of proper supportive care, limited availability of the expertise centre, and the patient's affordability. Recently, results with intensified immunosuppressive therapy that includes anti-thymocyte globulin with cyclosporine-A (CsA) and eltrombopag, are enough encouraging to consider it as treatment of choice in patients lacking MSD or who are not fit for HSCT. However, limitations in resource constraints settings including the cost of therapy limit its full utilization. Relapse of the disease or evolution to myelodysplasia or paroxysmal nocturnal haemoglobinuria (PNH) in a proportion of patients is another challenge with immunosuppressants. The majority of the AA patients still receive CsA with or without androgens in India, mostly because of increased cost and limited availability of HSCT and ATG. The use of the unrelated or alternative donor is still upcoming in India, with unavailable data in terms of response and survival. Therefore, there is an utmost need for novel agents for the better management of AA having a balanced efficacy and toxicity profile to improve the survival and quality of life.

Mass cytometry analysis identifies T cell immune signature of aplastic anemia and predicts the response to cyclosporine

Aplastic anemia (AA) is an auto-activated T cell-mediated bone marrow failure. Cyclosporine is often used to treat non-severe AA, which demonstrates a more heterogeneous condition than severe AA. The response rate to cyclosporine is only around 50% in non-severe AA. To better predict response to cyclosporine and pinpoint who is the appropriate candidate for cyclosporine, we performed phenotypic and functional T cell immune signature at single cell level by mass cytometry from 30 patients with non-severe AA. Unexpectedly, non-significant differences of T cell subsets were observed between AA and healthy control or cyclosporine-responder and non-responders. Interestingly, when screening the expression of co-inhibitory molecules, T cell trafficking mediators, and cytokines, we found an increase of cytotoxic T lymphocyte antigen 4 (CTLA-4) on T cells in response to cyclosporine and a lower level of CTLA-4 on CD8⁺ T cells was correlated to hematologic response. Moreover, a decreased expression of sphingosine-1-phosphate receptor 1 (S1P₁) on naive T cells and a lower level of interleukin-9 (IL-9) on T helpers also predicted a better response to cyclosporine, respectively. Therefore, the T cell immune signature, especially in CTAL-4, S1P₁, and IL-9, has a predictive value for response to cyclosporine. Collectively, our study implies that immune signature analysis of T cell by mass cytometry is a useful tool to make a strategic decision on cyclosporine treatment of AA.

Partial SAA patients benefit from delayed response of IST

Introduction

Severe aplastic anemia(SAA)is a severe disease characterized by immune-mediated bone marrow failure and pancytopenia. Immunosuppressive therapy (ATG plus CsA, IST) is the standard treatment for patients who are not suitable for allogeneic hematopoietic stem cell transplantation (allo-HSCT). Some patients have a delayed response after 6 months of ATG, and unnecessary to be given secondary ATG or allo-HSCT. We attempted to distinguish patients who may get potential delayed response from those who were really not responsive to IST.

Methods

We collected data from 45 SAA patients who were assessed no-response to IST at 6 months after rATG and failed to receive secondary ATG or allo-HSCT.

Results

CsA plus eltrombopag (EPAG) group has an extra 75% response rate while CsA maintenance group has an extra 44% response rate at 12 months. ATG was applied within 30 days after diagnosis, ATG dosage was suffificient (ATG/lymphocyte ≥2), and absolute reticulocyte count (ARC) was ≥30×109 /L at 6 months, indicated patients could get delayed response and benefifit from CsA maintenance. Addition of EPAG could give an even better response. Otherwise, secondary ATG or allo-HSCT treatment were recommended to be given immediately.

Clinical Trial Registration

https://www.chictr.org.cn/searchproj.aspx, identifier ChiCTR2300067615.

Aplastic Anemia as a Roadmap for Bone Marrow Failure: An Overview and a Clinical Workflow

In recent years, it has become increasingly apparent that bone marrow (BM) failures and myeloid malignancy predisposition syndromes are characterized by a wide phenotypic spectrum and that these diseases must be considered in the differential diagnosis of children and adults with unexplained hematopoiesis defects. Clinically, hypocellular BM failure still represents a challenge in pathobiology-guided treatment. There are three fundamental topics that emerged from our review of the existing data. An exogenous stressor, an immune defect, and a constitutional genetic defect fuel a vicious cycle of hematopoietic stem cells, immune niches, and stroma compartments. A wide phenotypic spectrum exists for inherited and acquired BM failures and predispositions to myeloid malignancies. In order to effectively manage patients, it is crucial to establish the right diagnosis. New theragnostic windows can be revealed by exploring BM failure pathomechanisms.

Eltrombopag as frontline treatment of aplastic anaemia in routine practice: implications on cost and efficacy

The thrombopoietin mimetic eltrombopag (EPAG) is efficacious in clinical trials of newly diagnosed moderate (M), severe (S) and very severe (vS) aplastic anaemia (AA). Its use in routine practice and resource-constrained settings is not well described. Twenty-five men and 38 women at a median age of 54 (18-86) years with newly diagnosed AA treated consecutively in a 7-year period with EPAG (N = 6), EPAG/cyclosporine (CsA) (N = 33) and EPAG/CsA/anti-thymocyte globulin (ATG) (N = 24) were analyzed. Because EPAG was not reimbursed, peak doses ranged from 25 to 200 mg/day depending on affordability. EPAG/CsA-treated patients were older (median age: 61 years) with less severe AA (MAA, N = 15; SAA, N = 14; vSAA, N = 4), whereas EPAG/CsA/ATG-treated patients were younger (median age: 44 years) with more severe AA (MAA, N = 2; SAA, N = 12, vSAA, N = 10). The overall/trilineage response rates were 83%/50% for EPAG-treated patients; 79%/42% for EPAG/CsA-treated patients and 75%/63% for EPAG/CsA/ATG-treated patients. Adverse events included grade 1 liver derangement (N = 7) and grade 1 dyspepsia (N = 3). The 5-year overall survivals/failure-free survivals were 62%/80% for the entire cohort; 55%/75% for EPAG/CsA-treated patients and 82%/78% for EPAG/CsA/ATG-treated patients. EPAG showed robust efficacy in AA in routine practice. However, EPAG dosage and combinations remain to be optimized for AA of different severities.

A multicenter phase II study on the efficacy and safety of hetrombopag in patients with severe aplastic anemia refractory to immunosuppressive therapy

Background:

In this single-arm phase II study (NCT03557099), we evaluated the efficacy and safety of hetrombopag, a small molecule thrombopoietin (TPO) receptor agonist, in patients with severe aplastic anemia (SAA) who were refractory to standard first-line immunosuppressive therapy (IST).

Methods:

SAA patients who were refractory to standard first-line IST were given hetrombopag orally at an initial dose of 7.5 mg once daily to a maximum of 15 mg once daily, for a total of 52 weeks. The primary endpoint was proportion of patients achieving hematologic responses in ⩾1 lineage at week 18.

Results:

A total of 55 eligible patients were enrolled and received hetrombopag treatment. This study met its primary endpoint, with 23 [41.8%, 95% confidence interval (CI) = 28.7–55.9] patients achieving hematologic response in ⩾1 lineage at week 18 after initiation of hetrombopag treatment. Twenty-four (43.6%, 95% CI = 30.3–57.7) and 27 (49.1%, 95% CI = 35.4–62.9) of the 55 patients responded in ⩾1 lineage at weeks 24 and 52, respectively. Median time to initial hematologic response was 7.9 weeks (range = 2.0–32.1). The responses were durable, with a 12-month relapse-free survival rate of 82.2% (95% CI = 62.2–92.2). Adverse events occurred in 54 (98.2%) patients, and 28 (50.9%) patients had treatment-related adverse events. Seventeen (30.9%) patients had adverse events of grade ⩾3. Serious adverse events occurred in 15 (27.3%) patients and three deaths (5.5%) were reported.

Conclusion:

Hetrombopag showed encouraging efficacy with durable hematologic responses in patients with SAA who were refractory to IST. Hetrombopag was well tolerant and safe for long-term use.

ClinicalTrials.gov identifier:

NCT03557099

Eltrombopag Added to Immunosuppression in Severe Aplastic Anemia

BACKGROUND

A single-group, phase 1-2 study indicated that eltrombopag improved the efficacy of standard immunosuppressive therapy that entailed horse antithymocyte globulin (ATG) plus cyclosporine in patients with severe aplastic anemia.

METHODS

In this prospective, investigator-led, open-label, multicenter, randomized, phase 3 trial, we compared the efficacy and safety of horse ATG plus cyclosporine with or without eltrombopag as front-line therapy in previously untreated patients with severe aplastic anemia. The primary end point was a hematologic complete response at 3 months.

RESULTS

Patients were assigned to receive immunosuppressive therapy (Group A, 101 patients) or immunosuppressive therapy plus eltrombopag (Group B, 96 patients). The percentage of patients who had a complete response at 3 months was 10% in Group A and 22% in Group B (odds ratio, 3.2; 95% confidence interval [CI], 1.3 to 7.8; P = 0.01). At 6 months, the overall response rate (the percentage of patients who had a complete or partial response) was 41% in Group A and 68% in Group B. The median times to the first response were 8.8 months (Group A) and 3.0 months (Group B). The incidence of severe adverse events was similar in the two groups. With a median follow-up of 24 months, a karyotypic abnormality that was classified as myelodysplastic syndrome developed in 1 patient (Group A) and 2 patients (Group B); event-free survival was 34% and 46%, respectively. Somatic mutations were detected in 29% (Group A) and 31% (Group Β) of the patients at baseline; these percentages increased to 66% and 55%, respectively, at 6 months, without affecting the hematologic response and 2-year outcome.

CONCLUSIONS

The addition of eltrombopag to standard immunosuppressive therapy improved the rate, rapidity, and strength of hematologic response among previously untreated patients with severe aplastic anemia, without additional toxic effects. (Funded by Novartis and others; RACE ClinicalTrials.gov number, NCT02099747; EudraCT number, 2014-000363-40.).

Treatment outcome of 301 aplastic anemia patients in China: a 10-year follow-up and real-world data from single institute experience

OBJECTIVE

This study was carried out to explore clinical treatment and prognosis of patients with AA with different economic status. Methods: We retrospectively analyzed the clinical outcome of 301 patients with AA in our center from April 2008 to November 2017.

RESULTS

Treatments included anti-thymocyte globulin (ATG) or anti-lymphocyte globulin (ALG) combined with cyclosporineA (CsA) (9%), allogeneic hematopoietic stem cell transplantation (allo-HSCT) (7%), CsA combined with androgen or CsA alone (hereinafter referred to as CsA group) (77%), no specific therapy (7%). The 5-year overall survival (OS) was higher in patients with non-severe AA (94.6%) compared with those with severe AA (SAA) (66.6%, P <.001), very severe AA (VSAA) (41.3%, P <.001). The 5-year OS was 76.5% in patients with SAA/VSAA treated with ATG/ALG combined with CsA, 75% in allo-HSCT group(P =.936), 63.6% in CsA group (P =.557), which was significantly higher than no specific therapy group (21.8%, P =.002). For those who responded to CsA , the duration of CsA (median follow-up time: 27 months, 1-101 months) was positively correlated with progression-free survival (r=0.603, P <.001). Multivariate analysis revealed that 36-65 years of age, SAA/VSAA, and no specific therapy were independent risk factors for inferior survival.

CONCLUSION

The treatment of elderly patients with AA still faces challenges. CsA is benefit to the survival of SAA/VSAA patients. AA patients, who responded to initialy CsA treatment, may benefit from prolonged CsA treatment. In view of the side effects of CsA, the timing of withdrawal is worth further exploration.

Thrombopoietin receptor agonists for marrow failure: A concise clinical review

Bone marrow failure is characterized by a disruption of hematopoietic stem cell (HSC) homeostasis and function, which causes decreased blood counts. Germline and somatic mutations within HSCs and immune dysregulation contribute to the pathogenesis of marrow failure. Allogeneic HSC transplant is a potentially curative therapy for marrow failure, although not all patients are candidates for this procedure. Immune suppressive therapy (IST) is an effective treatment for patients with aplastic anemia (AA) and select patients with myelodysplastic syndromes, but some patients fail to respond or relapse after IST. Over the past decade, the oral thrombopoietin receptor agonist eltrombopag has become a therapeutic option for AA in combination with frontline IST, and as a single agent for relapsed and refractory patients after IST. In this review, we highlight current knowledge of thrombopoietin receptor agonist mechanisms of action, and clinical indications and toxicities in patients with marrow failure, including the risk of clonal evolution.

Special issues related to the diagnosis and management of acquired aplastic anemia in countries with restricted resources, a report on behalf of the Eastern Mediterranean blood and marrow transplantation (EMBMT) group and severe aplastic anemia working party of the European Society for blood and marrow transplantation (SAAWP of EBMT)

Aplastic anemia is a relatively rare but potentially fatal disorder, with a reported higher incidence in developing countries in comparison to the West. There are significant variations in epidemiological as well as etiological factors of bone marrow failure syndromes in the developing countries in comparison to the developed world. Furthermore, the management of bone marrow failure syndromes in resource constraint settings has significant challenges including delayed diagnosis and referral, limited accessibility to healthcare facilities, treatment modalities as well as limitations related to patients who require allogeneic stem cell transplantation. Here we will provide a review of the available evidence related to specific issues of aplastic anemia in the developing countries and we summarize suggested recommendations from the Eastern Mediterranean blood and bone marrow transplantation (EMBMT) group and the severe aplastic anemia working party of the European Society of blood and marrow transplantation (SAAWP of EBMT) related to the diagnosis and therapeutic options in countries with restricted resources.

Predicting response of severe aplastic anemia to immunosuppression combined with eltrombopag

Pretreatment blood counts, particularly an absolute reticulocyte count ≥25×10⁹/L, correlate with response to immunosuppressive therapy in severe aplastic anemia. In recent trials, eltrombopag combined with standard immunosuppressive therapy yielded superior responses than those to immunosuppressive therapy alone. Our single institution retrospective study aimed to elucidate whether historical predictors of response to immunosuppressive therapy alone were also associated with response to immunosuppressive therapy plus eltrombopag. We sought correlations of blood counts, thrombopoietin levels and the presence of paroxysmal nocturnal hemoglobinuria clones with both overall and complete responses in 416 patients with severe aplastic anemia, aged 2-82 years (median, 30 years), initially treated with immunosuppressive therapy plus eltrombopag between 2012 and 2019 (n=176) or with immunosuppressive therapy alone between 1999 and 2010 (n=240). Compared to non-responders, patients in the group of overall responders to immunosuppressive therapy plus eltrombopag had significantly higher pretreatment absolute reticulocyte counts, higher neutrophil counts and reduced thrombopoietin levels, as also observed for the group treated with immunosuppressive therapy alone. Addition of eltrombopag markedly improved the overall response in subjects with an absolute reticulocyte count between 10-30×10⁹/L from 60% (54 of 90) to 91% (62 of 68). Absolute lymphocyte count correlated with complete response in the groups treated with immunosuppressive therapy with or without eltrombopag, especially in adolescents aged ≥10 years and adults, but the correlation was reversed in younger children. Platelet count and the presence of a paroxysmal nocturnal hemoglobinuria clone did not correlate with responses to immunosuppressive therapy. Blood counts remain the best predictors of response to nontransplant therapies in severe aplastic anemia. Addition of eltrombopag to immunosuppressive therapy shifted patients with a lower absolute reticulocyte count into a better prognostic category.

Acquired severe aplastic anaemia: how medical therapy evolved in the 20th and 21st centuries

The progress in aplastic anaemia (AA) management is one of success. Once an obscure entity resulting in death in most affected can now be successfully treated with either haematopoietic stem cell transplantation (HSCT) or immunosuppressive therapy (IST). The mechanisms that underly the diminution of haematopoietic stem cells (HSCs) are now better elucidated, and include genetics and immunological alterations. Advances in supportive care with better antimicrobials, safer blood products and iron chelation have greatly impacted AA outcomes. Working somewhat 'mysteriously', anti-thymocyte globulin (ATG) forms the base for both HSCT and IST protocols. Efforts to augment immunosuppression potency have not, unfortunately, led to better outcomes. Stimulating HSCs, an often-sought approach, has not been effective historically. The thrombopoietin receptor agonists (Tpo-RA) have been effective in stimulating early HSCs in AA despite the high endogenous Tpo levels. Dosing, timing and best combinations with Tpo-RAs are being defined to improve HSCs expansion in AA with minimal added toxicity. The more comprehensive access and advances in HSCT and IST protocols are likely to benefit AA patients worldwide. The focus of this review will be on the medical treatment advances in AA.

Eltrombopag Improves Erythroid Differentiation in a Human Induced Pluripotent Stem Cell Model of Diamond Blackfan Anemia

Diamond Blackfan Anemia (DBA) is a congenital macrocytic anemia associated with ribosomal protein haploinsufficiency. Ribosomal dysfunction delays globin synthesis, resulting in excess toxic free heme in erythroid progenitors, early differentiation arrest, and pure red cell aplasia. In this study, DBA induced pluripotent stem cell (iPSC) lines were generated from blood mononuclear cells of DBA patients with inactivating mutations in RPS19 and subjected to hematopoietic differentiation to model disease phenotypes. In vitro differentiated hematopoietic cells were used to investigate whether eltrombopag, an FDA-approved mimetic of thrombopoietin with robust intracellular iron chelating properties, could rescue erythropoiesis in DBA by restricting the labile iron pool (LIP) derived from excessive free heme. DBA iPSCs exhibited RPS19 haploinsufficiency, reduction in the 40S/60S ribosomal subunit ratio and early erythroid differentiation arrest in the absence of eltrombopag, compared to control isogenic iPSCs established by CRISPR/Cas9-mediated correction of the RPS19 point mutation. Notably, differentiation of DBA iPSCs in the presence of eltrombopag markedly improved erythroid maturation. Consistent with a molecular mechanism based on intracellular iron chelation, we observed that deferasirox, a clinically licensed iron chelator able to permeate into cells, also enhanced erythropoiesis in our DBA iPSC model. In contrast, erythroid maturation did not improve substantially in DBA iPSC differentiation cultures supplemented with deferoxamine, a clinically available iron chelator that poorly accesses LIP within cellular compartments. These findings identify eltrombopag as a promising new therapeutic to improve anemia in DBA.

Eltrombopag restores erythropoiesis in refractory adult acquired pure red cell aplasia

Acquired pure red cell aplasia is a rare condition characterized by normocytic normochromic anemia with severe reticulocytopenia. In refractory acquired pure red cell aplasia, the low response rate of immunosuppressive therapy also constitutes a challenge. We herein report the case of a 58-year-old male with refractory acquired pure red cell aplasia that was successfully treated by eltrombopag at a dose of 75 mg/day. After application of eltrombopag, the patient achieved complete remission and tolerated the treatment very well, with only mild bilirubin elevation. These preliminary findings showed that eltrombopag may be effective and well tolerated in adult patients with refractory acquired pure red cell aplasia.

Eltrombopag, oral immunosuppressant and androgen combination therapy in twelve patients with refractory severe aplastic anemia

Objective: Eltrombopag monotherapy or eltrombopag combined with immunosuppressant has achieved robust hematologic responses in severe aplastic anemia (SAA). In patients with refractory SAA, for whom hematopoietic stem cell transplantation is unavailable, we attempted to combine eltrombopag with oral immunosuppressant and androgen, to further improve hematologic response. Methods: We collected and analyzed data retrospectively from twelve refractory SAA cases who had received combination therapy of eltrombopag, oral immunosuppressant and androgen. All these patients had received intensive immunosuppressive treatment (IST) for more than 6 months and were evaluated as nonresponders. Results: A total of 12 SAA patients were treated with a combination of eltrombopag, an oral immunosuppressant (cyclosporine, N = 9; tacrolimus, N = 3) and androgen. The median maximum dose of eltrombopag was 75 mg/day (range, 75-150). After a median follow-up of 8.5 months (7-23), the overall response rate (ORR) was 42% (5/12, including trilineage, N = 4; hemoglobin + platelet, N = 1). Two of 5 responders reached normal blood counts. Optimal hematological response rates were reached at 6 months. The median increase in neutrophil, hemoglobin and platelet count were 1.64 × 10⁹ /L (0.71-2.66), 53 g/L (25-66.5) and 25 × 10⁹ /L (14-230), respectively. In general, the combination therapy was well tolerated; however, two patients suffered from non-lethal upper extremity venous thrombosis when they were platelet transfusion-dependent. Conclusion: Eltrombopag, oral immunosuppressant and androgen combination therapy in patients with IST-refractory SAA is feasible and could restore multi-lineage hematopoiesis. Thrombosis risk of eltrombopag still needs to be monitored.

Correlation of the Plasma Concentration of Eltrombopag With Efficacy in the Treatment of Refractory Aplastic Anemia: A Single-Centre Study in China

Background and purpose: Eltrombopag (ELT) can be effective in the treatment of relapse/refractory aplastic anemia (AA) patients. Responses and adverse drug reactions (ADRs) differed greatly among individuals treated at the same dosage of ELT.

Methods: Patients diagnosed with nonsevere aplastic anemia (NSAA) between January 2018 and January 2019 in Peking Union Medical Colleague Hospital who were refractory to immunosuppressive therapy were treated with ELT and followed up for at least 6 months. Plasma concentrations of ELT were detected by high-performance liquid chromatography-mass spectrometry after at least two months of ELT treatment and treatment at the same dosage for at least 2 weeks. The dose-concentration, concentration-response and concentration-ADR relationships were evaluated.

Results: Among the 72 patients treated with ELT during the study period, 44 patients with complete data were enrolled. Six (13.6%) were males, and 38 were females (86.4%), with a median age of 54 years [interquartile range (IQR): 38.5–63]. At the time the ELT plasma concentration was detected, the median dosage of ELT was 75 (IQR 50–100) mg/d, the median time of total ELT exposure was 3 (IQR 2.0–6.0) months, and 37 (70.5%) patients had responded to ELT. The median concentration of ELT was 10.4 μg/ml (IQR 3.7–24.4 μg/ml). The concentration of ELT was positively correlated with the daily dose of ELT (r = 0.68, p < 0.001). Multivariate logistic regression analysis showed that the risk of inefficacy of ELT at a concentration between 11.2 and 15.2 μg/ml was 0.028-fold (95% CI: 0.001–0.864; p = 0.041) of that at a concentration between 3.2 and 7.2 μg/ml. The cutoff value for the concentration of ELT showing efficacy was 12.50 μg/ml according to the receiver operation characteristic curve. A higher risk of ADR was related to a longer total exposure to ELT (p = 0.012). Although the correlation was not significant, the odds ratio increased with the ELT concentration, suggesting that it was possible that an elevated risk of ADR was correlated with the ELT blood concentration.

Conclusion: ELT is effective for the treatment of NSAA and has acceptable side effects. The plasma concentration of ELT was correlated with the dose and the effects of ELT.

[Efficacy and safety of eltrombopag in aplastic anemia: A multi-center survey in China]

Objective: To evaluate the safety and efficacy of eltrombopag combined with immunosuppressive therapy in patients with aplastic anemia (AA) in China. Methods: We investigated and analyzed the clinical data of AA patients from 14 hematological treatment centers who were treated with oral eltrombopag for at least 3 mon. Results: We enrolled 56 AA patients, including 19 treatment-naïve patients and 37 IST-refractory patients. The median administration period for eltrombopag was 7 (3-31) months, and the median maximum stable dosage was 75 mg/d (50-150 mg/d) . The 3-month hematological response (HR) rate was 60%, and the complete response (CR) rate was 30% in 10 SAA patients who were treated with first-line eltrombopag and standard IST (ATG+CsA) . Eight of 9 eltrombopag and CsA ± androgen first-line treated SAA patients responded (8/9, 89%) and 4 (44%) gave CR. The overall HR and CR rates were 79% and 52.6%, respectively, among these 19 patients by the end of the follow-up period. Of the 19 AA patients who were refractory to CsA ± androgen, 11 achieved HR (57.9%) at 3 mon, and the best HR rate was 44% in standard IST (ATG+CsA) refractory 18 patients after eltrombopag treatment. Fifty-one percent of the patients experienced mild or moderate adverse events, and gastrointestinal discomfort was the most common adverse effect reported by the study subjects. Conclusion: Adding Eltrombopag in first-line IST can accelerate the acquisition and improve the quality of hematological responses in AA patients. AA with relatively more residual hematopoietic cells may be well treated with eltrombopag and non-ATG IST. Eltrombopag can be used as salvage therapy for CsA±androgen refractory patients. Eltrombopag was generally safe and well tolerated by AA patients in China.

The Effectiveness of Rapamycin Combined with Eltrombopag in Murine Models of Immune-Mediated Bone Marrow Failure

Severe aplastic anemia (SAA) is a rare disease characterized by severe pancytopenia and bone marrow failure. Most patients with AA respond to immunosuppressive therapy (IST), usually as antithymocyte globulin (ATG) and cyclosporine (CsA), but some relapse on CsA withdrawal or require long-term administration of CsA to maintain blood counts. Recent research has found that rapamycin (Rapa) was an effective therapy in mouse models of immune-mediated bone marrow failure. However, it has not achieved a satisfactory effect in clinical application. At present, many studies have confirmed that eltrombopag (ELT) combined with IST can improve the curative effect of AA patients. Then, whether Rapa combined Elt in the treatment of AA will acquire better efficacy than a single drug application remains unclear. In this study, an immune attack-mediated AA mouse model was constructed by total body irradiation (TBI) and allo-lymphocyte infusion. In our study, we tested the efficacy of Rapa combined with Elt as a new treatment in mouse models of immune-mediated bone marrow failure. It showed that treatment with Rapa in combination Elt in the AA mouse model ameliorated pancytopenia and extended animal survival in a manner comparable to the standard dose of CsA and Rapa alone. However, there was no significant improvement effect on the number and function of NK cells and their subsets, mDCs, and CD4+/CD8+ ratio in AA mice after the therapy of Rapa combined with Elt compared with Rapa alone. Furthermore, the secretion of IL-10 of Tregs in AA mice increased significantly after the therapy of Rapa combined with Elt, but there was no significant difference in the number of Treg cells. We did not observe the difference in the curative effect of the Rapa group and CsA group, but for IL-10/Tregs ratio, the Rapa group was superior to the CsA group. And the IFN-r secretion of CD8+T cells in AA mice decreased significantly after the combination therapy of Rapa and Elt than Rapa alone. Compared with the AA group, the level of plasma IFN-γ, IL-2, and TNF-α decreased significantly (P < 0.05), but IL-10, IL-4, IL-5, and IL-1β increased significantly in the Rapa group (P < 0.05). As for IL-10, IL-12p70, IL-2, IL-6, KC/GRO, and TNF-α, the therapy of Rapa combined with Elt showed a more significant effect than Rapa alone in AA mice. To some extent, this study had shown a relatively better synergistic effect in murine models of immune-mediated bone marrow failure after the combination therapy of Rapa and Elt, which was a promising clinical utility in SAA treatment.

Novel therapeutic choices in immune aplastic anemia

Aplastic anemia (AA) in its severe form has historically been associated with high mortality. With limited supportive care and no effective strategy to reverse marrow failure, most patients diagnosed with severe AA (SAA) died of pancytopenia complications. Since the 1970s, hematopoietic stem cell transplantation (HSCT) and immunosuppressive therapy (IST) have changed SAA's natural history by improving marrow function and pancytopenia. Standard IST with horse anti-thymocyte globulin plus cyclosporine produces a hematologic response rate of 60 to 70%. In the long term, about one-third of patients relapse, and 10 to 15% can develop cytogenetic abnormalities. Outcomes with either HSCT or IST are similar, and choosing between these modalities relies on age, availability of a histocompatible donor, comorbidities, and patient preference. The introduction of eltrombopag, a thrombopoietin receptor agonist, improved SAA outcomes as both salvage (second-line) and upfront therapy combined with IST. As a single agent, eltrombopag in doses up to 150 mg daily improved cytopenias in 40 to 50% in those who failed initial IST, which associated with higher marrow cellularity, suggesting a pan-stimulatory marrow effect. When eltrombopag was combined with IST as upfront therapy, overall (about 90%) and complete responses (about 50%) were higher than observed extensively with IST alone of 65% and 10%, respectively. Not surprisingly, given the strong correlation between hematologic response rates and survival in SAA, most (>90%) were alive after a median follow-up of 18 months. Longer follow-up and real-word data continue to confirm the activity of this agent in AA. The use of eltrombopag in different combinations and doses are currently being explored. The activity of another thrombopoietin receptor agonist in AA, romiplostim, suggests a class effect. In the coming years, the mechanisms of their activity and the most optimal regimen are likely to be elucidated.

Romiplostim is effective for eltrombopag-refractory aplastic anemia: results of a retrospective study

Eltrombopag (EPAG) and romiplostim (ROM), thrombopoietin receptor-agonists with demonstrated efficacy against aplastic anemia (AA) in prospective controlled studies, were authorized in Japan for use in adults with aplastic anemia in 2017 and 2019, respectively. So far, no data are available on the potential contribution of switching from ROM to EPAG or vice versa in terms of efficacy or tolerance. Efficacies and tolerance profiles of ten patients, who failed to respond to the maximum dose of EPAG and then switched to ROM, were evaluated. All ten patients received a maximum dose of ROM (20 μg/kg/week). At a median follow-up of twelve months, seven of ten patients (70%) had achieved either neutrophil, erythroid, or platelet response, including one complete response. No patients showed platelet count fluctuations that were reported during ROM treatment for immune thrombocytopenia. In univariate analysis of the relationship between efficacy and demographics, the response had a correlation with neither factors. None of the patients stopped the ROM treatment because of adverse events. Although a larger number of patients and a longer follow-up period are needed to confirm our findings, our results show the efficacy of ROM in patients with EPAG-refractory AA.

[Evaluation of the efficacy of cyclosporin A combined with recombined human thrombopoietin for treating patients with non-severe aplastic anemia]

Objectives: To compare the efficacy of cyclosporin A (CsA) alone and CsA combined with recombined human thrombopoietin (rhTPO) in patients with non-severe aplastic anemia (NSAA) . Methods: Data from 83 patients with NSAA between August 2014 and February 2019 were collected retrospectively. The study population included 35 men and 48 women, with a median age of 45 years (14-85 years) . Among them, 57 had been treated with CsA + rhTPO, TPO was administered at 15 000 U QD for 7 days, once a month for 3 months, and the other 26 patients with compatible baseline characters were treated with CsA alone. All the enrolled patients had been treated with CsA for at least 6 months and were followed up for at least 1 year. The efficacy and outcome were compared between the two groups. Results: Total 23 men and 34 women, with a median age of 46 years (14-85 years) were treated with CsA + rhTPO. The median duration of CsA treatment was 17 (8-28) months, and the patients were followed up for a median of 27 (12-45) months. Total 12 men and 14 women, with a median age of 40 years (20-64) were treated with CsA alone. The median duration of CsA treatment was 19 months (9-30 months) , and the median follow-up duration was 29 months (16-66 months) . There was no significant difference in the baseline characteristics of the two groups (P>0.05) . There was no significant difference in the CR and OR rates of the two groups at 1, 3, 6, 12, and 24 months of treatment (P>0.05) . The change in the platelet level for the CsA + rhTPO treated group after 1 month[8 (-12-86) ×10(9)/L vs. 3 (16-57) ×10(9)/L, P=0.029) , 3 months[24 (-6-102) ×10(9)/L vs. 7 (-9-76) ×10(9)/L, P=0.006], and 6 months[33.5 (-4-123) ×10(9)/L vs. 12.5 (-14-109) ×10(9)/L, P=0.048] of treatment was higher than that in the CsA alone group, while no significant difference was found between the two groups at other time points. There was no significant difference in the change in the megakaryocyte level between the two groups[3 (0-4) vs. 2 (0-5) , z=-0.868, P=0.385] after 6 months of treatment. Apart from 10.5% (6/57) of the patients in the CsA + rhTPO treated group who reported soreness at the injection site, there was no other significant difference between the two groups in terms of adverse effects. During the follow-up period, there were two cases of increasing paroxysmal nocturnal hemoglobinuria clone to over 10%, one in the CsA + rhTPO treated group, the other in the CsA alone group; and there was one case of progression to SAA in the CsA + rhTPO treated group; while no case of death or thromboembolic event (TEE) , fibrosis or reticulin proliferation, progression to myelodysplastic syndrome (MDS) , or acute myeloid leukemia was observed in either group. There was one case of progression to SAA in the CsA + rhTPO treated group but none in the CsA alone group. Conclusion: Compared to CsA alone, CsA + rhTPO treatment can accelerate the recovery of the platelet level with acceptable adverse effects.

Effective treatment of refractory acquired pure red blood cell aplasia with eltrombopag and sirolimus: a case report

Acquired pure red cell aplasia (aPRCA) is a kind of anemia characterized by severe reticulocytopenia and reduced bone marrow erythroblastic cells. For patients who are refractory to the first-line therapy (cyclosporin A with/without glucocorticoids), second-line therapy is considered less effective. We report on a patient with primary aPRCA who was refractory to cyclosporin A, glucocorticoids, and several second-line regimens. The patient was treated with sirolimus for 10 months with no improvement in hemoglobin but complete response was achieved after adding eltrombopag at a dosage of 25 mg/day. Eltrombopag was well tolerated with no evidence of clonal evolution at the end of follow up. This case provided a new attempt at treating patients with refractory/relapse aPRCA with eltrombopag, probably in combination with sirolimus.

Disappearance of monosomy 7 in a patient with aplastic anemia after eltrombopag treatment

We present the case of a patient with aplastic anemia (AA) who was treated with eltrombopag. To the best of our knowledge, this is the first report of the disappearance of monosomy 7 after eltrombopag treatment. The patient was a 77-year-old woman with intraoral hematoma and purpura who was diagnosed with very severe AA with a normal karyotype. After combination therapy with rabbit antithymocyte globulin, cyclosporin, and granulocyte-colony-stimulating factor (G-CSF), pancytopenia transiently improved. When pancytopenia worsened again, the patient was administered darbepoetin alfa for renal anemia and danazol. Bone marrow examination showed 2.5% blasts with the karyotype 45,XX,-7[17]/46,XX[3], and 87.0% of marrow cells had monosomy 7, as determined by 7q31 interphase fluorescence in situ hybridization (FISH) analysis. Pancytopenia was considered owing to the evolution of myelodysplastic syndrome, and we stopped G-CSF and darbepoetin treatment. As she refused treatment with a hypomethylating agent, considering her age, eltrombopag was started against refractory pancytopenia after obtaining informed consent. She showed an improvement in pancytopenia and became transfusion independent. After 1 year of eltrombopag treatment, bone marrow examination revealed 0.7% blasts with the karyotype 46,XX[20] and without monosomy 7 clone by FISH analysis. After a further 1 year of eltrombopag treatment with dose tapering, she has achieved a complete response. This case suggested that eltrombopag treatment is not necessarily contraindicated in patients with monosomy 7.

Burden of illness among patients with severe aplastic anemia who have had insufficient response to immunosuppressive therapy: a multicenter retrospective chart review study

This study assessed treatment patterns and healthcare resource utilization (HRU) of patients with severe aplastic anemia (SAA) with insufficient response to immunosuppressive therapy (IST). A retrospective chart review was conducted at Dana-Farber Cancer Institute (DFCI), United States, and Hôpital Saint-Louis (HSL), France. Eligible patients were ≥ 18 years old, diagnosed with acquired SAA between January 1, 2006, and July 31, 2016, had insufficient response to IST, and had ≥ 12 months of follow-up post-diagnosis. Overall survival (OS) was estimated using the Kaplan-Meier method. Among the 40 patients, mean age at diagnosis was 44 years and 53% were women. Median follow-up time after SAA diagnosis was 48.3 months. Ninety-five percent of patients received antithymocyte globulin (ATG) as primary therapy prior to hematopoietic stem cell transplant (HSCT). Most common secondary SAA therapies prior to HSCT were eltrombopag (28%) and androgens (15%). Seventy-five percent of patients received HSCT. Prior to HSCT, patients received an average of 2.7 red blood cell (RBC) and 3.3 platelet transfusions per month; patients had 0.9 hospitalizations, 0.4 emergency room visits, and 12.8 office visits per year. Five-year OS was 75%, with infection as the primary cause of death. Additionally, this study provides information on the subgroup of patients receiving eltrombopag which was the most common secondary therapy. This study quantified transfusion and HRU burden associated with SAA and demonstrated high 5-year survival in a recently treated cohort.

Haploidentical transplantation and posttransplant cyclophosphamide for treating aplastic anemia patients: a report from the EBMT Severe Aplastic Anemia Working Party

In the absence of an HLA-matched donor, the best treatment for acquired aplastic anemia patients refractory to immunosuppression is unclear. We collected and analyzed data from all acquired aplastic anemia patients who underwent a haploidentical transplantation with posttransplant cyclophosphamide in Europe from 2011 to 2017 (n = 33). The cumulative incidence of neutrophil engraftment was 67% (CI_95%: 51-83%) at D +28 and was unaffected by age group, stem cell source, ATG use, or Baltimore conditioning regimen. The cumulative incidence of grades II-III acute GvHD was 23% at D +100, and limited chronic GvHD was 10% (0-20) at 2 years, without cases of grade IV acute or extensive chronic GvHD. Two-year overall survival was 78% (64-93), and 2-year graft-versus-host disease-free survival was 63% (46-81). In univariate analysis, the 2-year OS was higher among patients who received the Baltimore conditioning regimen (93% (81-100) versus 64% (41-87), p = 0.03), whereas age group, stem cell source, and ATG use had no effect. Our results using unmanipulated haploidentical transplantation and posttransplant cyclophosphamide for treating refractory AA patients are encouraging, but warrant confirmation in a prospective study with a larger number of patients and longer follow-up.

Mechanisms and therapeutic prospects of thrombopoietin receptor agonists

The second-generation thrombopoietin (TPO) receptor agonists eltrombopag and romiplostim are potent activators of megakaryopoiesis and represent a growing treatment option for patients with thrombocytopenic hematological disorders. Both TPO receptor agonists have been approved worldwide for the treatment of children and adults with chronic immune thrombocytopenia. In the EU and USA, eltrombopag is approved for the treatment of patients with severe aplastic anemia who have had an insufficient response to immunosuppressive therapy and in the USA for the first-line treatment of severe aplastic anemia in combination with immunosuppressive therapy. Eltrombopag has also shown efficacy in several other disease settings, for example, chemotherapy-induced thrombocytopenia, selected inherited thrombocytopenias, and myelodysplastic syndromes. While both TPO receptor agonists stimulate TPO receptor signaling and enhance megakaryopoiesis, their vastly different biochemical structures bestow upon them markedly different molecular and functional properties. Here, we review and discuss results from preclinical and clinical studies on the functional and molecular mechanisms of action of this new class of drug.

Eltrombopag in Immune Thrombocytopenia, Aplastic Anemia, and Myelodysplastic Syndrome: From Megakaryopoiesis to Immunomodulation

Eltrombopag is an orally available thrombopoietin receptor agonist indicated for the treatment of immune thrombocytopenia (ITP). Beyond the effect on megakaryopoiesis, the drug also showed a stimulating effect on the hematopoietic stem cell with consistent clinical efficacy in aplastic anemia (AA) and myelodysplastic syndromes (MDS). Eltrombopag is highly effective in ITP and less so in AA and MDS. This observation underlines the importance of residual normal hematopoiesis, which is maximal in ITP, minimal/absent in AA, and dysregulated in MDS. In ITP, the drug at 50-75 mg daily induced up to 85% responses both in clinical trials and real-life studies, with the possibility of tapering and discontinuation. In AA, eltrombopag at 150 mg daily was effective in about 40% of cases relapsed/refractory to standard immunosuppression or ineligible for bone marrow transplant. In MDS, the drug seems less effective, with responses in about a quarter of patients at various schedules. The efficacy of eltrombopag in ITP, AA, and MDS suggests the existence of common immune-pathological mechanisms in these diseases, including autoimmunity against peripheral blood cells and bone marrow precursors, as well as a possible evolution of one condition into the other. Additional mechanisms of action emerging from the clinical use of eltrombopag include modulation of T-regulatory cells, restoration of Fc-γ receptor balance in phagocytes, and an iron-mobilizing effect. In this review, we analyzed the most recent literature on eltrombopag use and efficacy in patients with ITP, AA, and MDS, exploring the basis for different dosing, combined treatments, and discontinuation in each context.

Activity of eltrombopag in severe aplastic anemia

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.

Management of aplastic anemia after failure of frontline immunosuppression

Introduction: About 60% of aplastic anemia (AA) patients are in need of further treatment after frontline standard immunosuppressive therapy (IST). This along with the prolonged survival of AA subjects who do not respond to or relapse after this treatment makes management of these patients a rising and very challenging issue. Areas covered: Literature research, carried out from the most commonly used databases, included the following keywords: aplastic anemia, immunosuppressive treatment, antithymocyte globuline, ciclosporine A, refractory aplastic anemia, relapsing aplastic anemia, hematopoietic stem cell transplantation including haploidentical and cord blood transplantations thrombopoietin mimetics, supportive treatment, chelation and infections. Studies on the treatment of aplastic anemia with different levels of evidence were included. Top level of evidence studies (metanalyses and randomized prospective controlled trials) were a minority because severe AA, particularly in the subset of patients who fail upfront IST, is an extremely rare disease. Guidelines from National Societies and review articles were also included. Expert opinion: The most commonly used treatments after failure of upfront immunosuppression are hematopoietic stem cell transplantation, a second course of immunosuppression and thrombopoietin mimetics alone or in combination with immunosuppression. Other potential options are alemtuzumab, androgens, oral cyclosporine A in monotherapy. Not many comparative studies exist to clearly establish the superiority of one over another strategy. Therefore, the choice of the best treatment for these patients should rely on major driving factors like patient's age and comorbidities, availability of a matched unrelated donor, donor's characteristics and drug-availability.

The Case for Upfront HLA-Matched Unrelated Donor Hematopoietic Stem Cell Transplantation as a Curative Option for Adult Acquired Severe Aplastic Anemia

The improved success of HLA-matched unrelated donor (MUD) hematopoietic stem cell transplantation (HSCT) for severe aplastic anemia (SAA) in recent decades has had an impact on the indications for and timing of this treatment modality. In the absence of a matched sibling donor (MSD), historically MUD HSCT was reserved as an option after failure to respond to at least 2 courses of immunosuppressive therapy (IST) in adults with SAA, but with improved outcomes over time, it is now considered following failure to respond to 1 course of IST. Recent national and international studies and guidelines now recommend upfront MUD HSCT as an option for children for whom an MUD is readily available, because outcomes are similar to those for MSD HSCT. Fludarabine-based conditioning and the use of in vivo T cell depletion with antithymocyte globulin or alemtuzumab has been associated with a reported overall survival (OS) of >85% in adult patients undergoing MUD HSCT. However, the recent introduction of eltrombopag for patients with SAA has transformed the treatment landscape, and there is currently much interest in its use with IST as upfront treatment, which showed a high response rate in an early-phase study. The risks of HSCT, especially graft-versus-host disease (GVHD), need to be carefully balanced against the concerns of IST, namely relapse and later clonal evolution to myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML). In the absence of a current prospective randomized trial comparing these 2 approaches, in this review we examine the evidence supporting consideration of early MUD HSCT in adults with SAA who would have been considered for MSD HSCT but who lack a MSD and for whom an MUD is readily available, especially using an irradiation-free conditioning regimen, with a low risk of GVHD, as another treatment option. This option may be offered to patients to provide them with an informed choice, with the aim of curing disease rather than achieving freedom from disease, relapse-free survival, or OS. Furthermore, understanding the immune signature for the response to IST and the immunologic responses to somatic mutations and clonal progression to MDS/AML may help define the future indications for upfront HSCT and a more precise medical approach to therapy.

Treatment optimization and genomic outcomes in refractory severe aplastic anemia treated with eltrombopag

Eltrombopag (EPAG) received approval from the US Food and Drug Administration for the treatment of refractory severe aplastic anemia (rSAA) based on treatment of 43 patients with doses escalating from 50 to 150 mg daily for 12 weeks. Response kinetics suggested that more prolonged administration of EPAG at a dose of 150 mg could speed and improve response rates. We enrolled 40 patients with rSAA in a study of EPAG 150 mg daily, with a primary end point of response at 24 weeks. Twenty (50%) of 40 patients responded at 24 weeks; 5 (25%) of 20 would have been deemed nonresponders at 12 weeks, the end point of the previous study. Fifteen of the 19 responding patients continuing on EPAG had drug discontinued for robust response; 5 of the 15 required EPAG re-initiation for relapse, with all recovering response. To analyze risk of clonal progression, we combined long-term data from the 83 patients with rSAA enrolled in both studies. Evolution to an abnormal karyotype occurred in 16 (19%), most within 6 months of EPAG initiation. Targeted deep sequencing/whole-exome sequencing was performed pre-EPAG and at primary response end point and/or time of clonal evolution or longest follow-up. Cytogenetic evolution did not correlate with mutational status, and overall mutated allele fractions of myeloid cancer genes did not increase on EPAG. In summary, extended administration of EPAG at a dose of 150 mg for 24 weeks rescued responses in some patients with rSAA not responding at 12 weeks. The temporal relationship between clonal evolution and drug exposure suggests that EPAG may promote expansion of dormant preexisting clones with an aberrant karyotype. The studies were registered at www.clinicaltrials.gov as #NCT00922883 and #NCT01891994.

Indications for haematopoietic stem cell transplantation for haematological diseases, solid tumours and immune disorders: current practice in Europe, 2019

This is the seventh special EBMT report on the indications for haematopoietic stem cell transplantation for haematological diseases, solid tumours and immune disorders. Our aim is to provide general guidance on transplant indications according to prevailing clinical practice in EBMT countries and centres. In order to inform patient decisions, these recommendations must be considered together with the risk of the disease, the risk of the transplant procedure and the results of non-transplant strategies. In over two decades since the first report, the EBMT indications manuscripts have incorporated changes in transplant practice coming from scientific and technical developments in the field. In this same period, the establishment of JACIE accreditation has promoted high quality and led to improved outcomes of patient and donor care and laboratory performance in transplantation and cellular therapy. An updated report with operating definitions, revised indications and an additional set of data with overall survival at 1 year and non-relapse mortality at day 100 after transplant in the commonest standard-of-care indications is presented. Additional efforts are currently underway to enable EBMT member centres to benchmark their risk-adapted outcomes as part of the Registry upgrade Project 2020 against national and/or international outcome data.

Use of eltrombopag in aplastic anemia in Europe

Eltrombopag (ELT), an oral thrombopoietin receptor agonist, has recently emerged as a promising new drug for the treatment of aplastic anemia (AA). How ELT is used outside of clinical trials in the real-world setting and results of this treatment are not known. We conducted therefore a retrospective survey on the use of ELT in AA among EBMT member centers. We analyzed the 134 patients reported in our survey together with 46 patients recently published by Lengline et al. The median follow-up from start of ELT treatment was 15.3 months, with 85.6% patients alive at last follow-up. Importantly, only 28.9% of our patients received ELT according to the FDA/EMA label as monotherapy in the relapsed/refractory setting, whereas 16.7% received ELT upfront. The overall response rate in our cohort was 62%, very similar to the results of the pivotal ELT trial. In multivariate analysis, combination therapy with ELT/cyclosporine/ATG and response to previous therapy were associated with response. Overall survival was favorable with a 1-year survival from ELT start of 87.4%. We identified age, AA severity before ELT start and response to ELT as variables significantly associated with OS. Two patients transformed to MDS; other adverse events were mostly benign. In sum, ELT is used widely in Europe to treat AA patients, mostly in the relapsed/refractory setting. Response to ELT is similar to the clinical trial data across different age groups, treatment lines, and treatment combinations and results in favorable survival.

Evaluation of eltrombopag in patients with aplastic anemia in real-world experience

Background

Although eltrombopag has recently been approved for treating AA, the effects of its clinical use remain unknown.

Methods

We retrospectively analyzed 11 patients with AA, who had been treated with eltrombopag from August 2017 to May 2018.

Results

Overall response rate was 55%. There was tri-lineage recovery in four patients and platelet recovery in two. The reactive time was within 8 weeks after treatment initiation. Stage at the initial assessment, the neutrophil-to-lymphocyte ratio and platelet counts were significantly different between the responders and non-responders.

Conclusion

Eltrombopag is a promising agent for treating patients with any degree of AA.

Idiopathic Aplastic Anemia: An Update

"Bone marrow failure" encompass all the conditions and syndromes in which there are qualitative or quantitative disorders of one or more lineages (erythroid, myelomonocytic, and/or megakaryocytic). A few years ago, the pathophysiology of these syndromes was completely unknown. Today we have better knowledge for these diseases, allowing the development of new treatment options and the improvement of patients' outcome. Acquired bone marrow failure syndromes include myelodysplastic syndromes, aplastic anemia, paroxysmal nocturnal hemoglobinuria, idiopathic neutropenia and large granular leukemia. All these syndromes share some common features and pathophysiology. The most important feature is the possibility of clonal evolution and progression into acute myelogenous leukemia, and open questions still remain on how to prevent evolution in these patients.