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

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.

Treatment of relapsed/refractory severe aplastic anemia in children: Evidence-based recommendations

Severe aplastic anemia (SAA) is a rare potentially fatal hematologic disorder. Although overall outcomes with treatment are excellent, there are variations in management approach, including differences in treatment between adult and pediatric patients. Certain aspects of treatment are under active investigation in clinical trials. Because of the rarity of the disease, some pediatric hematologists may have relatively limited experience with the complex management of SAA. The following recommendations reflect an up-to-date evidence-based approach to the treatment of children with relapsed or refractory SAA.

Rapid and sustained response to luspatercept and eltrombopag combined treatment in one case of clonal cytopenias of undetermined significance with prior failure to cyclosporin and androgen therapy: a case report

Clonal cytopenia of undetermined significance (CCUS) has the characteristics of high-risk transformation into myelodysplastic syndromes. At present, there are few effective treatments for CCUS, and there is no consensus or evidence-based recommendation. We present a case demonstrating a rapid, significant and sustained response to combined treatment with luspatercept and eltrombopag, following the failure of cyclosporin and androgen therapy. Even after discontinuing luspatercept for 10 months, trilineage haematopoiesis remained normal with the use of cyclosporin and other haematopoietic stimulants. This case suggests that the inhibition of transforming growth factor-β could potentially have an immunomodulatory effect, thereby promoting the recovery of haematopoietic function. Luspatercept, along with Acalabrutinib or Cyclosporine, may synergistically stimulate haematopoiesis.

Guidelines for the diagnosis and management of adult aplastic anaemia: A British Society for Haematology Guideline

Pancytopenia with hypocellular bone marrow is the hallmark of aplastic anaemia (AA) and the diagnosis is confirmed after careful evaluation, following exclusion of alternate diagnosis including hypoplastic myelodysplastic syndromes. Emerging use of molecular cyto-genomics is helpful in delineating immune mediated AA from inherited bone marrow failures (IBMF). Camitta criteria is used to assess disease severity, which along with age and availability of human leucocyte antigen compatible donor are determinants for therapeutic decisions. Supportive care with blood and platelet transfusion support, along with anti-microbial prophylaxis and prompt management of opportunistic infections remain key throughout the disease course. The standard first-line treatment for newly diagnosed acquired severe/very severe AA patients is horse anti-thymocyte globulin and ciclosporin-based immunosuppressive therapy (IST) with eltrombopag or allogeneic haemopoietic stem cell transplant (HSCT) from a matched sibling donor. Unrelated donor HSCT in adults should be considered after lack of response to IST, and up front for young adults with severe infections and a readily available matched unrelated donor. Management of IBMF, AA in pregnancy and in elderly require special attention. In view of the rarity of AA and complexity of management, appropriate discussion in multidisciplinary meetings and involvement of expert centres is strongly recommended to improve patient outcomes.

Progress in medical therapy in aplastic anemia: why it took so long?

The treatment of aplastic anemia (AA) has significantly advanced in the last 50 years, evolving from a fatal condition to one where survival rates now exceed 80-85%. Hematopoietic stem cell transplantation (HSCT) and immunosuppressive therapy (IST) have become the primary treatments, with the latter widely adopted due to factors like the scarcity of compatible donors, patient age, comorbidities, and limited HSCT access. A therapy breakthrough was the introduction of antithymocyte globulin (ATG), with its effectiveness further boosted by cyclosporine. However, it took years to achieve another major milestone in management. Initially, treatments aimed to intensify immunosuppression following the success of the ATG-cyclosporine combination, but these methods fell short of expectations. A major turning point was combining immunosuppression with stem cell stimulation, surpassing the efficacy of IST alone. Earlier, growth factors had shown limited success in AA treatment, but thrombopoietin receptor agonists represented a significant advancement. Initially applied alone as salvage, these were later combined with IST, forming the most effective current regimen for medically managing SAA. Horse ATG is the preferred formulation combined with cyclosporine and eltrombopag. This progress in AA treatment offers improved outcomes for patients afflicted with this once-lethal disease.

A multicentre ambispective observational study into the incidence and clinical management of aplastic anaemia in Spain (IMAS study)

Aplastic anemia (AA) is a rare, life-threatening hematological disease, with a poorly defined incidence. As the data available on AA varies substantially worldwide, a multicenter, ambispective, observational study was carried out between 2010 and 2019 to assess the incidence, clinical management and survival of AA at seven Spanish hospitals. The incidence of AA was 2.83 per million inhabitants per year, consistent with that reported previously in Europe, with a median age at diagnosis of 61 years-old (range 12-86), and a similar number of males and females. The initial diagnosis was severe or very severe AA in 55.8% of cases and 93.7% required transfusion. The most frequent first line therapy was anti-thymocyte globulin (ATG) plus cyclosporin A (CsA, 44.2%), followed by other CsA-based regimes (46.3%), with hematopoietic stem cell transplantation an infrequent 1st line therapy. The 6-month response rate was 68.2%, which then increased over a median follow-up of 3.9 years. The 5-year overall survival (5OS) was 73.6%, similar in severe (78.6%) and very severe AA patients (74.6%) but lower in moderate AA (MAA) patients (68.4%). The 5OS was 100% in 0-25 year-old patients but dropping to 58.3% in patients ≥ 60 years-old. At the last contact, 75.8% of the patients were alive. In conclusion, the incidence, characteristics and management of AA in our study are consistent with that reported previously. In terms of survival, although the global long-term OS rate was good, there is room for improvement, particularly in older patients. Finally, what appears to be a worse long-term survival of MAA patients, as reported previously, reinforces the importance of not underestimating this condition when diagnosed as MAA.

Clinical implications of myeloid malignancy‑related somatic mutations in aplastic anemia

Aplastic anemia (AA) is a potentially fatal bone marrow failure syndrome characterized by a paucity of hematopoietic stem cells and progenitor cells with varying degrees of cytopenia and fatty infiltration of the bone marrow space. Recent advances in genomics have uncovered a link between somatic mutations and myeloid cancer in AA patients. At present, the impact of these mutations on AA patients remains uncertain. We retrospectively investigated 279 AA patients and 174 patients with myelodysplastic syndromes (MDS) and performed targeted sequencing of 22 genes on their bone marrow cells using next-generation sequencing (NGS). Associations of somatic mutations with prognostic relevance and response to treatment were analyzed. Of 279 AA patients, 25 (9.0%) patients had somatic mutations, and 20 (7.2%) patients had one mutation. The most frequently mutated genes were ASXL1(3.2% of the patients), DNMT3A (1.8%) and TET2 (1.8%). In the MDS group, somatic mutations were detected in 120 of 174 (69.0%) patients, and 81 patients (46.6%) had more than one mutation. The most frequently mutated genes were U2AF1 (24.7% of the patients), ASXL1 (18.4%) and TP53 (13.2%). Compared with MDS patients, AA patients had a significantly lower frequency of somatic mutations and mostly one mutation. Similarly, the median variant allele frequency was lower in AA patients than in MDS patients (6.9% vs. 28.4%). The overall response of 3 and 6 months in the somatic mutation (SM) group was 37.5% and 66.7%, respectively. Moreover, there was no significant difference compared with the no somatic mutation (N-SM) group. During the 2-years follow-up period, four (20%) deaths occurred in the SM group and 40 (18.1%) in the N-SM group, with no significant difference in overall survival and event-free survival between the two groups. Our data indicated that myeloid tumor-associated somatic mutations in AA patients were detected in only a minority of patients by NGS. AA and MDS patients had different gene mutation patterns. The somatic mutations in patients with AA were characterized by lower mutation frequency, mostly one mutation, and lower median allelic burden of mutations than MDS. Somatic mutations were a common finding in the elderly, and the frequency of mutations increases with age. The platelet count affected the treatment response at 3 months, and ferritin level affected the outcome at 6 months, while somatic mutations were not associated with treatment response or long-term survival. However, our cohort of patients with the mutation was small; this result needs to be further confirmed with large patient sample.

Efficacy and safety of eltrombopag in Chinese patients with refractory or relapsed severe aplastic anemia

For patients with severe aplastic anemia (SAA) in China who have had an insufficient response to the first-line treatment with hematopoietic stem cell transplantation or immunosuppressive therapy, there is no established standard of care other than transfusion support and treatment of infections. This non-randomized, open-label, Phase II multicenter trial investigated the efficacy and safety of eltrombopag in 20 adult Chinese patients with refractory or relapsed (r/r) SAA. The primary endpoint of hematologic response rate at Week 26, defined as the proportion of patients who met any of the International Working Group criteria, was observed in 70% (14/20) of patients, with more than 50% of these having at least bi-lineage response. Reduced red blood cell and platelet transfusion at Week 26 were observed in 57% (8/14) and 80% (8/10) of patients, respectively. Safety findings were consistent with the established safety profile of eltrombopag and no new safety signals were reported. None of the patients discontinued eltrombopag because of safety concerns. Although the sample size was small, this is the first prospective study to show that eltrombopag is efficacious and has a favorable safety profile in a Chinese patient population with r/r SAA.Trial registration: This trial is registered on ClinicalTrials.gov (NCT03988608); registered 17 June 2019.

Repeated immunosuppressive rabbit antithymocyte globulin therapy for adult patients with relapsed or refractory aplastic anemia

OBJECTIVES

Immunosuppressive therapy (IST) with antithymocyte globulin (ATG) and cyclosporin A is the standard treatment for aplastic anemia (AA). However, the efficacy of repeated IST with rabbit ATG (rATG) as salvage therapy remains unclear in patients with relapsed or refractory AA.

METHODS

We retrospectively evaluated the efficacy and safety of IST2 with rATG (IST2-rATG) in 19 consecutive patients with relapsed or refractory AA who received first-line IST with rATG in two centers between 2009 and 2020.

RESULTS

The overall 6-month response rate of the patients was 58%. The response rates were similar between patients with relapsed and refractory AA. The presence of glycophosphatidylinositol-deficient blood cells was associated with a better response to IST2-rATG. Despite retreatment with the same rATG, serum disease and severe allergic reactions were not observed.

CONCLUSION

IST2-rATG is effective and safe for the treatment of adult patients with relapsed and refractory AA after receiving first-line IST with rATG.

Prolonged use of eltrombopag in patients with severe aplastic anemia in the real world

Eltrombopag (EPAG) can improve the efficacy of immunosuppressive therapy (IST) consisting of antithymocyte immunoglobulin (ATG) and cyclosporin in severe aplastic anemia (SAA) patients. This study explored whether patients with SAA could benefit from continuous usage of EPAG beyond 6 months.Seventy-four treatment-naive Chinese patients with SAA were administrated with rabbit ATG-based IST plus EPAG for 6 months. Patients not achieving complete remission (CR) at 6 months were treated with EPAG for another 6 months.At 1, 3, 6 and 12 months after IST, the cumulative response rates were 31%, 61%, 82% and 90%, and the cumulative CR rates were 0, 14%, 27% and 45%, respectively. The cumulative effect curve showed that 93% and 53% of all remission and CR occurred within 6 months, while 98% and 83% of all remission and CR occurred within 12 months. Thirty-seven percent of patients (11 of 30) with partial remission (PR) at 6 months continuously exposed to EPAG improved to CR within 3 (1-5) months of the extended median time. Six patients failing at 6 months continued to use EPAG. Three patients showed improved responses with an extended median time of 6 (1-6) months. The 2-year event-free survival (EFS) was better in those continuing with EPAG (89% vs. 49%, P = 0.006) for patients with PR or non-remission at 6 months.Continuous administration with EPAG could improve the hematologic response and EFS in patients without achieving CR at 6 months.This trial has been registered at the Chinese Clinical Trial Registry (ChiCTR2100045895).

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.

The effectiveness of a novel treatment of TIM-3(-) NK cells infusion in murine models of immune-mediated bone marrow failure

BACKGROUND

T-cell immunoglobulin and mucin-containing domain (TIM)-3 exerts its inhibitory effect on NK cells and participates in the immune pathogenesis of SAA. In this study, we aimed to explore a novel treatment method of TIM-3(+) NK or TIM-3(-) NK cell infusion in combination with immunosuppressive therapy for bone marrow failure (BMF)/aplastic anemia (AA) mice.

METHODS

BMF/AA mouse model was constructed. The TIM-3 expression and functional molecules on TIM-3(+) and TIM-3(-) NK cells of the BMF group, total body irradiation (TBI) group, and normal control (NC) group mice were detected by flow cytometry. After treatment, the general condition, whole blood cell and bone marrow cell (BMC) count, and immune condition of mice from each group were compared.

RESULTS

TIM-3 expression in the peripheral blood NK cells of BMF mice was significantly lower than that of the TBI and NC group mice. TIM-3(-) NK cells expressed more NKG2D receptors than TIM-3(+) NK cells. The levels of P-Akt and PI3K in TIM-3(-) NK cells were higher than those in TIM-3(+) NK cells. On the 17th day after BMF induction, the weight, peripheral whole blood cell count, and BMC count of BMF mice decreased significantly compared with that of the NC group mice. The therapeutic effect in the TIM-3(-) NK cell treatment group was better than that in the TIM-3(+) NK cell treatment and CsA treatment groups. Concurrently, the ratio of CD4+ T and CD8+ T cells of BMF mice was significantly lower than that of the NC group mice. The therapeutic effect in CsA + TIM-3(-) NK group was more significant than that of the CsA treatment and the CsA + TIM-3(+) NK groups.

CONCLUSIONS

In this study, we found that the general condition, peripheral whole blood cell and BMC count, and immune status of BMF mice improved significantly after CsA + TIM-3(-) NK cell treatment. These results may provide further insights into the immune pathogenesis of SAA and novel therapeutic ideas for improving SAA treatment.

Eltrombopag Preserves the Clonogenic Potential of Hematopoietic Stem Cells During Treatment With Antithymocyte Globulin in Patients With Aplastic Anemia

Aplastic anemia (AA) is frequently caused by a T-cell mediated autoimmune depletion of the hematopoietic stem and progenitor cell (HSPC) compartment. Immunosuppressive therapy (IST) with antithymocyte globulin (ATG) and cyclosporine represents the first-line treatment of AA. One side effect of ATG therapy is the release of proinflammatory cytokines such as interferon-gamma (IFN-γ), which is considered a major factor in the pathogenic autoimmune depletion of HSPC. Recently, eltrombopag (EPAG) was introduced for therapy of refractory AA patients due to its ability to bypass IFN-γ-mediated HSPC inhibition among other mechanisms. Clinical trials have evidenced that EPAG started simultaneously with IST leads to a higher response rate compared with its later administration schedules. We hypothesize that EPAG might protect HSPC from negative effects of ATG-induced release of cytokines. We observed a significant decrease in colony numbers when both healthy peripheral blood (PB) CD34⁺ cells and AA-derived bone marrow cells were cultured in the presence of serum from patients under ATG treatment, as compared with before treatment. Consistent with our hypothesis, this effect could be rescued by adding EPAG in vitro to both healthy and AA-derived cells. By employing an IFN-γ neutralizing antibody, we also demonstrated that the deleterious early ATG effects on the healthy PB CD34⁺ compartment were mediated at least partially by IFN-γ. Hence, we provide evidence for the hitherto unexplained clinical observation that concomitant use of EPAG in addition to IST comprising ATG leads to improved response in patients with AA.

Efficacy of Eltrombopag with Immunosuppressive Therapy Versus Immunosuppressive Therapy Alone on Severe Aplastic Anaemia: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVE

Severe aplastic anaemia (SAA) is a syndrome of bone marrow failure caused by T cell-mediated destruction of haematopoietic stem cells and progenitor cells. Whether patients with SAA should be treated with eltrombopag (EPAG) and immunosuppressive therapy (IST) or IST alone remains debatable. Therefore, we conducted this meta-analysis to compare the efficacy of eltrombopag + IST with that of IST alone in patients with SAA and to assess the difference in the efficacy of eltrombopag in adults and children.

METHODS

We performed this meta-analysis by retrieving studies that met the inclusion and exclusion criteria from PubMed, EMBASE, and the Cochrane Library up to 1 January 2023. We used a random-effects model to calculate odds ratios (ORs) with 95% confidence intervals (CIs) for primary and secondary outcomes. I² statistics were used to evaluate the heterogeneity of the included studies.

RESULTS

Six studies involving a total of 699 patients were included. In terms of the primary outcomes, our pooled results indicated that patients treated with EPAG + IST had a higher 6-month overall response rate (OR = 2.25; 95% CI, 1.60-3.16; p < 0.00001), a higher 6-month complete response rate (OR = 2.61; 95% CI, 1.82-3.74; p < 0.00001), and a lower 6-month nonresponse rate (OR = 0.32; 95% CI, 0.19-0.52; p < 0.00001). However, there was no significant difference in the rate of 6-month partial response (OR = 0.94; 95% CI, 0.49-1.81; p = 0.85).

CONCLUSION

This meta-analysis indicated that patients treated with additional eltrombopag for IST may have a higher rate of haematological response.

Avatrombopag is effective in patients with chemoradiotherapy-induced aplastic anemia: a single-center, retrospective study

Aplastic anemia (AA) secondary to radiotherapy presents a difficult situation in the treatment of both the malignant tumor and AA itself. We aimed to evaluate the efficacy of avatrombopag (AVA), a thrombopoietin receptor agonist, in patients with AA secondary to chemoradiotherapy. In this retrospective study, patients with malignant tumors who were diagnosed with AA after radiotherapy and chemotherapy and accepted AVA between September 2020 and October 2021 at Peking Union Medical College Hospital were selected. A total of 34 patients were enrolled, including 13 (38.2%) men, with a median age of 60 (20-71) years. At a median of 8 (6-18) months of follow-up, the overall response rates (ORRs) at 1, 3, and 6 months were 32.4%, 55.9%, and 58.8%, respectively, and the complete response rates (CRRs) were 5.9%, 14.7%, and 23.5%, respectively. The median time to respond was 3 (1-6) months. In total, 15.0% of patients relapsed during follow-up, but no clonal evolution was noticed. Mild side effects were observed in 17.6% of patients without drug withdrawal. At the end of follow-up, 17.6% of patients had tumors relapsed. Four patients died, three from tumor relapse and one from cerebral hemorrhage. The ORR and CRR did not correlate with eltrombopag before AVA (p > 0.05) but increased when the total exposure of AVA increased (p = 0.011), and the threshold for AVA response was a cumulative dose > 3,000 mg (p = 0.013). AVA yielded good response and tolerance in patients treated for AA secondary to chemoradiotherapy, and a higher dose may correlate with better response.

Iron chelation of hetrombopag in aplastic anemia: a post hoc analysis of a phase II study

Hetrombopag is the only CFDA-approved thrombopoietin (TPO) receptor agonist for severe aplastic anemia (SAA) in China. Its chemical structure has an iron chelation domain. To explore the iron chelation effect of hetrombopag, we performed a post hoc analysis of the phase II clinical trial (NCT03557099). Thirty-five immunosuppressive therapy (IST)-refractory SAA patients were enrolled in the study, and the longitudinal changes of serum ferritin (SF) were assessed. At 18 weeks post-hetrombopag initiation, 51.4% of patients showed decreased SF levels by a median of 49.0 (18.1-95.5) % from baseline (median ΔSF decrease value, 917.2 ng/ml, range from 104.0 to 7030.0 ng/ml). A decrease in SF was found in 75.0% of hematologic responders and 31.6% of non-responders. Among the 24 patients with iron overload, 12 had decreased SF levels by up to 51% of the baseline. Patients with normal SF levels also showed decreased SF levels, and iron deficiency occurred in two patients. In conclusion, hetrombopag showed a powerful and rapid iron chelation effect.

Avatrombopag for the treatment of thrombocytopenia post hematopoietic stem-cell transplantation

Background:

Thrombocytopenia post hematopoietic stem-cell transplantation (HCT) usually contributes to poor outcomes with no standardized treatment. Eltrombopag and romiplostim can be feasible for post-HCT thrombocytopenia, but the use of avatrombopag has not yet been evaluated.

Objectives:

We aimed to evaluate the efficacy and safety of avatrombopag treatment in patients diagnosed with post-HCT thrombocytopenia.

Design:

In this retrospective study, we evaluated the efficacy and safety of avatrombopag treatment in a cohort of 61 patients diagnosed with thrombocytopenia post HCT in our clinical center.

Methods:

Avatrombopag was initiated at 20 mg daily, with a dosage adjustment to achieve platelet recovery to >20 × 10⁹/l independent from transfusion for 7 consecutive days (overall response, OR) or to >50 × 10⁹/l free from transfusion for 7 consecutive days (complete response, CR). Factors influencing OR and CR were studied in univariate and multivariate analyses, respectively. Within the follow-up, adverse events like myelofibrosis, thrombosis, and organ toxicities were monitored carefully.

Results:

The overall response rate (ORR) to avatrombopag was 68.9% and the cumulative incidence (CI) of OR was 69.1%. The complete response rate (CRR) and the CI of CR were both 39.3%. The median days from avatrombopag initiation to OR and CR were 21 and 25 days, respectively. An adequate number of megakaryocytes before the initiation of avatrombopag was an independent protective factor of avatrombopag treatment for OR (hazard ratio, HR = 4.628, 95% confidence interval 1.92–11.15, p = 0.0006) and CR (HR = 4.892, 95% confidence interval 1.58–15.18, p = 0.006). Avatrombopag was well tolerated in all patients with no severe adverse events.

Conclusion:

Our findings suggested that avatrombopag can be optional for thrombocytopenia post HCT.

Predictors of clonal evolution and myeloid neoplasia following immunosuppressive therapy in severe aplastic anemia

Predictors, genetic characteristics, and long-term outcomes of patients with SAA who clonally evolved after immunosuppressive therapy (IST) were assessed. SAA patients were treated with IST from 1989-2020. Clonal evolution was categorized as "high-risk" (overt myeloid neoplasm [meeting WHO criteria for dysplasia, MPN or acute leukemia] or isolated chromosome-7 abnormality/complex karyotype without dysplasia or overt myeloid neoplasia) or "low-risk" (non-7 or non-complex chromosome abnormalities without morphological evidence of dysplasia or myeloid neoplasia). Univariate and multivariate analysis using Fine-Gray competing risk regression model determined predictors. Long-term outcomes included relapse, overall survival (OS) and hematopoietic stem cell transplant (HSCT). Somatic mutations in myeloid cancer genes were assessed in evolvers and in 407 patients 6 months after IST. Of 663 SAA patients, 95 developed clonal evolution. Pre-treatment age >48 years and ANC > 0.87 × 10⁹/L were strong predictors of high-risk evolution. OS was 37% in high-risk clonal evolution by 5 years compared to 94% in low-risk. High-risk patients who underwent HSCT had improved OS. Eltrombopag did not increase high-risk evolution. Splicing factors and RUNX1 somatic variants were detected exclusively at high-risk evolution; DNMT3A, BCOR/L1 and ASXL1 were present in both. RUNX1, splicing factors and ASXL1 somatic mutations detected at 6 months after IST predicted high-risk evolution.

Anti-COX-2 autoantibody is a novel biomarker of immune aplastic anemia

In immune aplastic anemia (IAA), severe pancytopenia results from the immune-mediated destruction of hematopoietic stem cells. Several autoantibodies have been reported, but no clinically applicable autoantibody tests are available for IAA. We screened autoantibodies using a microarray containing >9000 proteins and validated the findings in a large international cohort of IAA patients (n = 405) and controls (n = 815). We identified a novel autoantibody that binds to the C-terminal end of cyclooxygenase 2 (COX-2, aCOX-2 Ab). In total, 37% of all adult IAA patients tested positive for aCOX-2 Ab, while only 1.7% of the controls were aCOX-2 Ab positive. Sporadic non-IAA aCOX-2 Ab positive cases were observed among patients with related bone marrow failure diseases, multiple sclerosis, and type I diabetes, whereas no aCOX-2 Ab seropositivity was detected in the healthy controls, in patients with non-autoinflammatory diseases or rheumatoid arthritis. In IAA, anti-COX-2 Ab positivity correlated with age and the HLA-DRB1*15:01 genotype. 83% of the >40 years old IAA patients with HLA-DRB1*15:01 were anti-COX-2 Ab positive, indicating an excellent sensitivity in this group. aCOX-2 Ab positive IAA patients also presented lower platelet counts. Our results suggest that aCOX-2 Ab defines a distinct subgroup of IAA and may serve as a valuable disease biomarker.

Clonality in immune aplastic anemia: Mechanisms of immune escape or malignant transformation

Aplastic anemia (AA) is the prototypic bone marrow failure syndrome and can be classified as either acquired or inherited. Inherited forms are due to the effects of germline mutations, while acquired AA is suspected to result from cytotoxic T-cell mediated immune attack on hematopoietic stem and progenitor cells. Once thought to be a purely "benign" condition, clonality in the form of chromosomal abnormalities and single nucleotide variants is now well recognized in AA. Mechanisms underpinning this clonality likely relate to selection of clones that allow immune evasion or increased cell survival the marrow environment under immune attack. Widespread use and availability of next generation and other genetic sequencing techniques has enabled us to better understand the genomic landscape of aplastic anemia. This review focuses on the current concepts associated with clonality, in particular somatic mutations and their impact on diagnosis and clinical outcomes in immune aplastic anemia.

Long-term eltrombopag for bone marrow failure depletes iron

Eltrombopag (EPAG) has been approved for the treatment of aplastic anemia and for immune thrombocytopenia, and a subset of patients require long-term therapy. Due to polyvalent cation chelation, prolonged therapy leads to previously underappreciated iron depletion. We conducted a retrospective review of patients treated at the NIH for aplastic anemia, myelodysplastic syndrome, and unilineage cytopenias, comparing those treated with EPAG to a historical cohort treated with immunosuppression without EPAG. We examined iron parameters, duration of therapy, response assessment, relapse rates, and common demographic parameters. We included 521 subjects treated with (n = 315) or without EPAG (n = 206) across 11 studies with multiyear follow-up (3.6 vs. 8.5 years, respectively). Duration of EPAG exposure correlated with ferritin reduction (p = 4 × 10^-14 ) regardless of response, maximum dose, or degree of initial iron overload. Clearance followed first-order kinetics with faster clearance (half-life 15.3 months) compared with historical responders (47.5 months, p = 8 × 10^-10 ). Risk of iron depletion was dependent upon baseline ferritin and duration of therapy. Baseline ferritin did not correlate with response of marrow failure to EPAG or to relapse risk, and timing of iron clearance did not correlate with disease response. In conclusion, EPAG efficiently chelates total body iron comparable to clinically available chelators. Prolonged use can deplete iron and ultimately lead to iron-deficiency anemia mimicking relapse, responsive to iron supplementation.

Exploring the Potential of Eltrombopag: Room for More?

Since its introduction in clinical practice, eltrombopag (ELT) has demonstrated efficacy in heterogeneous clinical contexts, encompassing both benign and malignant diseases, thus leading researchers to make a more in-depth study of its mechanism of action. As a result, a growing body of evidence demonstrates that ELT displays many effects ranging from native thrombopoietin agonism to immunomodulation, anti-inflammatory, and metabolic properties. These features collectively explain ELT effectiveness in a broad spectrum of indications; moreover, they suggest that ELT could be effective in different, challenging clinical scenarios. We reviewed the extended ELT mechanism of action in various diseases, with the aim of further exploring its full potential and hypothesize new, fascinating indications.

New Trends of Nontransplant therapy for Acquired Aplastic Anemia

Aplastic anemia (AA) is a hematological disease that is characterized by pancytopenia and hypofunctional bone marrow hematopoiesis. Patients with AA are treated with either immunosuppressive therapy (IST) using anti-thymocyte globulin (ATG) and Cyclosporine (CsA) or hematopoietic stem cell transplantation (HSCT), if a matched donor is available. The standard IST regimen for AA patients which results in response rates up to 70%, and even higher overall survival. However, primary and secondary failures after IST remain frequent, and to date all attempts aiming to overcome this problem have been unfruitful. The nontransplant therapeutic options for AA have significantly expanded during the last few years. Here, we review the new trends of nontransplant therapy for AA and summarize the current therapeutic effect of AA.

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 inhibits TET dioxygenase to contribute to hematopoietic stem cell expansion in aplastic anemia

Eltrombopag, an FDA-approved non-peptidyl thrombopoietin receptor agonist, is clinically used for the treatment of aplastic anemia, a disease characterized by hematopoietic stem cell failure and pancytopenia, to improve platelet counts and stem cell function. Eltrombopag treatment results in a durable trilineage hematopoietic expansion in patients. Some of the eltrombopag hematopoietic activity has been attributed to its off-target effects, including iron chelation properties. However, the mechanism of action for its full spectrum of clinical effects is still poorly understood. Here, we report that eltrombopag bound to the TET2 catalytic domain and inhibited its dioxygenase activity, which was independent of its role as an iron chelator. The DNA demethylating enzyme TET2, essential for hematopoietic stem cell differentiation and lineage commitment, is frequently mutated in myeloid malignancies. Eltrombopag treatment expanded TET2-proficient normal hematopoietic stem and progenitor cells, in part because of its ability to mimic loss of TET2 with simultaneous thrombopoietin receptor activation. On the contrary, TET inhibition in TET2 mutant malignant myeloid cells prevented neoplastic clonal evolution in vitro and in vivo. This mechanism of action may offer a restorative therapeutic index and provide a scientific rationale to treat selected patients with TET2 mutant-associated or TET deficiency-associated myeloid malignancies.

Long-term outcomes in patients with severe aplastic anemia treated with immunosuppression and eltrombopag: a phase 2 study

Patients with severe aplastic anemia (SAA) are either treated with bone marrow transplant (BMT) or immunosuppression (IST) depending on their age, comorbidities, and available donors. In 2017, our phase 2 trial reported improved hematologic responses with the addition of eltrombopag (EPAG) to standard IST for SAA when compared with a historical cohort treated with IST alone. However, the rates and characteristics of long-term complications, relapse, and clonal evolution, previously described in patients treated with IST alone, are not yet known with this new regimen, IST and EPAG. Patients were accrued from 2012 to 2020, with a total of 178 subjects included in this secondary endpoint analysis. With double the sample size and a much longer median follow-up (4 years) since the original publication in 2017, we report a cumulative relapse rate of 39% in responding patients who received cyclosporine (CSA) maintenance and clonal evolution of 15% in all treated patients at 4 years. Relapse occurred at distinct timepoints: after CSA dose reduction and EPAG discontinuation at 6 months, and after 2 years when CSA was discontinued. Most relapsed patients were retreated with therapeutic doses of CSA +/- EPAG, and two-thirds responded. Clonal evolution to a myeloid malignancy or chromosome 7 abnormality (high-risk) was noted in 5.7% of patients and conferred a poorer overall survival. Neither relapse nor high-risk evolution occurred at a higher rate than was observed in a historical comparator cohort, but the median time to both events was earlier in IST and EPAG treated patients. This trial was registered at www.clinicaltrials.gov as #NCT01623167.

Emergence of t(3;21)(q26.2;q22) during eltrombopag treatment in a patient with relapsed aplastic anemia who received chemotherapy for angioimmunoblastic T-cell lymphoma

A 65-year-old man with nonsevere aplastic anemia received rabbit anti-thymocyte globulin and cyclosporine and partially responded. Six months after the initiation of treatment, he was diagnosed with stage IV angioimmunoblastic T-cell lymphoma and received chemotherapy. PET/CT scan analysis indicated a complete response. However, he showed sustained myelosuppression and was diagnosed with relapse of aplastic anemia. He did not respond to cyclosporine, eltrombopag or methenolone. Fifteen months after eltrombopag administration, he developed MDS with t(3;21)(q26.2;q22). Patients should be monitored carefully for the emergence of not only -7/del(7q) but also 3q26 abnormalities, including t(3;21)(q26.2;q22), during and after eltrombopag treatment.

Toward a pathophysiology inspired treatment of VEXAS syndrome

VEXAS syndrome has an unmet need for therapeutic interventions. Even if few data exist regarding the treatment of this newly described syndrome, different options can be proposed given the unique pathophysiological consequences of the clonal dominance of UBA1 mutated hematopoietic stem cells. To date, allogeneic transplantation is the only curative option, but many questions remain regarding the selection of eligible patients, the conditioning regimen or management of toxicities that may be unique to VEXAS patients. Alternatively, drugs used in myelodysplastic syndrome such as hypomethylating agents or lenalidomide are interesting candidates, which could theoretically have also an effect on the clone. Another strategy is to target the inflammatory cascade, by inhibiting proinflammatory cytokines (such as TNFα, IL1, IL6) or effector cells, for example with JAK inhibitors. Whatever the choice of treatment for VEXAS patients, supportive care is always needed to be considered to manage frequent complications such as cytopenia, thrombosis and infections. Finally, we discuss the challenges of the design of clinical trials for VEXAS patients, from inclusion criteria to clinical and biological endpoints of activity.

Efficacy and safety of immunosuppressive therapy with or without eltrombopag in pediatric patients with acquired aplastic anemia: A Chinese retrospective study

To determine the efficacy and safety of eltrombopag (E-PAG) combined with intensive immunosuppressive therapy (IST) for the treatment of pediatric patients with severe aplastic anemia (SAA). A total of 57 pediatric patients with newly diagnosed severe aplastic anemia were enrolled in this study. Thirty nine patients were treated with IST alone, consisting of porcine anti-human thymocyte globulin (30 mg/kg/day × 5 days) and cyclosporine A (CsA) (treated for 2 years, with a trough concentration maintained at 200-250 ng/mL), and 18 patients were treated with IST + E-PAG (12.5-50 mg/day, maintained for 6 months). We found no statistical difference between the response rates at 3 months for the two groups (CR: 12.8% vs. 22.2% p > 0.05, ORR: 56.4% vs. 77.7% p > 0.05). However, we found a statistical difference between the response rates at 6 months for the two groups (CR: 17.9% vs. 50% p < 0.05, ORR: 69.2% vs. 94.4% p < 0.05). The main side-effect during treatment with E-PAG was having a slightly to moderately elevated bilirubin level, which was temporary and controllable, accounting for approximately 66.6% (12/18) of patients in the IST + E-PAG group vs. 20.5% (8/39) of those in the IST group (p < 0.05). IST + E-PAG therapy appears to be more effective than IST alone for the treatment of pediatric SAA, with good tolerability and compliance. This approach deserves further exploration.

Efficacy and safety of eltrombopag in the first-line therapy of severe aplastic anemia in children

Eltrombopag is being investigated for the treatment of aplastic anemia (AA) by stimulating hematopoietic stem cell (HSC) proliferation. To evaluate the efficacy and safety of eltrombopag in the first-line therapy of pediatric AA. The present retrospective study assessed pediatric patients with newly diagnosed AA administered immunosuppressive therapy (IST) (rabbit ATG combined with CSA) with eltrombopag at a single center from March to September 2017. All patients were followed up for >2 years. A total of 14 patients (8 males), averagely aged 86 months, were enrolled in this study. Eltrombopag was administered with a median time to initiation of 19.5 days after IST; the median course of treatment was 253 days. Complete and overall response rates at 6 months were 64.3% (9/14 case) and 78.6% (11/14 cases), respectively. The survival rate was 100%, and no relapse occurred in responders. Eltrombopag was well-tolerated; however, the most common adverse events included indirect bilirubin elevation, jaundice, and transient liver-enzyme elevation. By the end of follow-up, bone marrow chromosomes were normal, and no abnormal myelodysplastic syndrome (MDS)-related clones appeared. Addition of eltrombopag to IST is associated with markedly increased complete response with respect to hematology in pediatric patients with SAA compared with a historical cohort, without intolerable side effects.

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.

Haploidentical BMT for severe aplastic anemia with intensive GVHD prophylaxis including posttransplant cyclophosphamide

Severe aplastic anemia (SAA) is a stem cell disorder often treated with bone marrow transplantation (BMT) to reconstitute hematopoiesis. Outcomes of related HLA-haploidentical (haplo) donors after reduced-intensity conditioning with intensive graft-versus-host disease (GVHD) prophylaxis including posttransplantation cyclophosphamide are presented here from 37 SAA, 20 relapsed/refractory (R/R), and 17 treatment-naïve (TN) SAA patients. Median follow-up is 32 months (90% confidence interval [CI], 29-44). The median age was 25 (range, 4-69) years. The median time to neutrophil recovery was 17 days (range, 15-88). Four of 37 patients (11%) experienced graft failure (GF). There was 1 primary GF of 20 patients in the R/R group and 3 of 17 in the TN group at 200 cGy (1 primary, 2 secondary), but none in the 10 patients who received 400 cGy total body irradiation. Two patients with GF succumbed to infection and 2 were rescued with second haplo BMT. The overall survival for all patients is 94% (90% CI, 88-100) at 1 and 2 years. The cumulative incidence of grade II-IV acute GVHD at day 100 is 11%. The cumulative index of chronic GVHD at 2 years is 8%. Similar results were seen in 10 SAA patients who received the identical nonmyeloablative regimen with posttransplant cyclophosphamide but matched donor transplants. Haplo BMT with posttransplant cyclophosphamide represents a potential cure in SAA, with all 20 R/R currently alive, disease-free, and with no evidence of active GVHD. Extending this approach to TN patients was associated with higher GF rates, but an increase in total body irradiation dose to 400 cGy was associated with durable engraftment without greater early toxicity. Nonmyeloablative haplo BMT in TN SAA could lead to a paradigm shift, such that essentially all patients can proceed quickly to safe, curative BMT. These trials were registered at www.cincialtrials.gov as #NCT02224872) and #NCT02833805.

Eltrombopag for patients with moderate aplastic anemia or uni-lineage cytopenias

There is no standard or widely effective treatment of patients with moderate aplastic anemia (MAA) or hypo-productive uni-lineage cytopenias (UC). Eltrombopag (EPAG), a small molecule thrombopoietin mimetic, has previously been shown to result in durable multi-lineage hematologic responses with low toxicity in patients with refractory severe aplastic anemia (SAA). Its safety and efficacy in MAA are unknown. This prospective phase 2 study enrolled previously untreated and treated MAA and UC patients with clinically relevant cytopenias. EPAG was administered at doses escalating from 50 to 300 mg/d. Hematologic responses were assessed at 16 to 20 weeks. Responding patients were continued on EPAG until reaching defined robust or stable blood counts. EPAG was reinstituted for relapse. Thirty-four patients were enrolled between 2012 and 2017, including 31 with MAA and 3 with UC. Seventeen patients responded in at least 1 eligible lineage by the primary end point. A striking improvement in anemia was observed in a patient with Diamond-Blackfan anemia. EPAG was well tolerated, and it was discontinued for robust or stable blood counts in 12 of 17 patients after a median of 8 months. A majority required re-initiation of EPAG for declining counts, and all regained response. Two of 34 patients developed non-chromosome 7 bone marrow cytogenetic abnormalities while taking EPAG, without dysplasia or increased blasts. Somatic mutation allele frequencies in cancer genes did not increase overall on EPAG. EPAG is a well-tolerated oral treatment of cytopenias in patients with MAA/UC. This trial was registered at www.clinicaltrials.gov as #NCT01328587.

Comparisons Between Frontline Therapy and a Combination of Eltrombopag Plus Immunosuppression Therapy and Human Leukocyte Antigen-Haploidentical Hematopoietic Stem Cell Transplantation in Patients With Severe Aplastic Anemia: A Systematic Review

Background and Aims: This study aimed at comparing the efficacy and safety of eltrombopag (EPAG) plus immunosuppressive therapies (ISTs) and haploidentical hematopoietic stem cell transplantation (haplo-HSCT) in the frontline treatment for severe aplastic anemia (SAA) patients. Methods: Four electronic databases and Clinicaltrials.gov were comprehensively searched from January 2010 to August 2020. Studies that aimed at evaluating the efficacy and safety of EPAG+IST or haplo-HSCT in SAA patients were included. One-/2-year overall survival (OS), complete response (CR), and overall response rates (ORRs) were indirectly compared between EPAG+IST and haplo-HSCT. Results: A total of 447 patients involved in 10 cohort studies were found to be eligible for this study. A narrative synthesis was performed due to lack of data directly comparing the outcome of EPAG+IST and haplo-HSCT. Consistent with the analysis results in the whole population, subgroup analyses in the age-matched population showed that there was no significant difference in ORR between EPAG+IST and haplo-HSCT groups. However, the CR rate was lower in the EPAG+IST group when compared with the haplo-HSCT group. The incidence rate of clonal evolution/SAA relapse ranged at 8-14 and 19-31% in the EPAG+IST group but not reported in the haplo-HSCT group. The incidence rate for acute graft vs. host disease (aGVHD) and chronic graft vs. host disease (cGVHD) ranged at 52-57 and 12-67%, respectively, for the haplo-HSCT group. The main causes of deaths were infections in the EPAG+IST group, and GVHD and infections in the haplo-HSCT group. Conclusion: EPAG+IST has a comparable ORR and 1-/2-year OS but lower CR rate when indirectly compared with haplo-HSCT in the frontline treatment of patients with SAA. Patients treated with haplo-HSCT may exhibit a high incidence of GVHD, whereas patients treated with EPAG+IST may experience more relapses or clone evolution.

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.

[Diagnosis and Therapy of aplastic anemia - update 2021]

The landscape of aplastic anemia (AA) is changing as new therapeutic options become available and sophistic diagnostics enable us to decipher various subgroups of bone marrow failure syndromes (BMFS) such as telomeropathies and other constitutional diseases with manifestations beyond childhood.This article briefly summarizes developments of the last few years with potential clinical impact and puts it into perspective. Focus is given to the growing list of inherited BMFS and the need to e. g. screen patients at all ages for telomeropathies before initiation of treatment as part of routine evaluation of AA. The usage of next generation sequencing (NGS) to differentiate between AA and malignancies such as myelodysplatic syndrome (MDS) and the need to watch out for potential clonal evolution during and after treatment is also briefly discussed. Recent data on combinations of immunosuppressive therapy (IST) with thrombopoietin receptor agonists (TRA) for patients with severe AA as well as newer data with TRA mono-therapy for patients with moderate AA are presented. Finally the importance of supportive measures, structures and quality of life aspects are highlighted.

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.

CCR5 maintains macrophages in the bone marrow and drives hematopoietic failure in a mouse model of severe aplastic anemia

Severe aplastic anemia (SAA) is an acquired, T cell-driven bone marrow (BM) failure disease characterized by elevated interferon gamma (IFNγ), loss of hematopoietic stem cells (HSCs), and altered BM microenvironment, including dysfunctional macrophages (MΦs). T lymphocytes are therapeutic targets for treating SAA, however, the underlying mechanisms driving SAA development and how innate immune cells contribute to disease remain poorly understood. In a murine model of SAA, increased beta-chemokines correlated with disease and were partially dependent on IFNγ. IFNγ was required for increased expression of the chemokine receptor CCR5 on MΦs. CCR5 antagonism in murine SAA improved survival, correlating with increased platelets and significantly increased platelet-biased CD41^hi HSCs. T cells are key drivers of disease, however, T cell-specific CCR5 expression and T cell-derived CCL5 were not necessary for disease. CCR5 antagonism reduced BM MΦs and diminished their expression of Tnf and Ccl5, correlating with reduced frequencies of IFNγ-secreting BM T cells. Mechanistically, CCR5 was intrinsically required for maintaining BM MΦs during SAA. Ccr5 expression was significantly increased in MΦs from aged mice and humans, relative to young counterparts. Our data identify CCR5 signaling as a key axis promoting the development of IFNγ-dependent BM failure, particularly relevant in aging where Ccr5 expression is elevated.

Eltrombopag for the treatment of refractory thrombocytopenia associated with connective tissue disease

To assess the efficacy and safety of eltrombopag in connective tissue disease (CTD)-immune thrombocytopenia (ITP), we conducted this single-center retrospective observational study, including patients with refractory CTD-ITP who were treated with eltrombopag between January 2018 and August 2019. The characteristics of patients at baseline, and the efficacy and safety of the drug were analyzed. The predictors for a response were analyzed using a univariate analysis such as Chi-square or nonparametric test and a multiple correspondence analysis (MCA) method. A total of 15 patients with refractory CTD-ITP were included in the study. Their median age at the time of inclusion was 40.6 years. The median platelet count at initiation of eltrombopag was 11.53 × 10⁹/L. The median remission time was 3.42 weeks. The complete remission (CR) and overall response rate decreased with time. The factors that associated with response to eltrombopag in patients with CTD-ITP were protopathy, WBC counts, levels of hemoglobin, and characteristics of bone marrow findings in univariate analysis. In addition, MCA indicated that a poor response to eltrombopag in patients with refractory CTD-ITP was closely associated with a protopathy with SS, medium to severe degree of anemia, leukopenia, and bone marrow aspiration showing aplastic anemia, an absence of megakaryocytes or macrophage activation syndrome (MAS). In conclusion, eltrombopag was effective and well-tolerated in patients with CTD-associated thrombocytopenia. Some factors should be considered in the use of eltrombopag, including the protopathy, blood test, and bone marrow histology.