Prospective randomized trial comparing two doses of rabbit anti‐thymocyte globulin in patients with severe aplastic anaemia

Adjunctive effects of eltrombopag on immunosuppressive therapy for childhood aplastic anemia

Eltrombopag is used with first-line immunosuppressive therapy for adult aplastic anemia, although its practical utility in childhood remains unclear. We retrospectively analyzed the outcomes of pediatric patients who received eltrombopag in Japan. Of the 27 eligible patients, 23 (85%) were previously treated, and 15 (56%) had severe or very-severe disease. Seventeen (63%) received eltrombopag with or after rabbit anti-thymocyte globulin plus cyclosporin-A. Within the first year of eltrombopag therapy, 12 patients showed a good or partial response, 15 showed no response, and 8 non-responders successfully underwent hematopoietic cell transplantation. Within the first 3 months after eltrombopag therapy, all but one of the transfusion-dependent responders became transfusion-independent. At 12 months, 6 of 12 responders were disease-free off-treatment. The one-year overall response rate was higher for severe or very-severe than non-severe cases (p = 0.006). Multivariable analysis showed that very-severe disease at the start of eltrombopag therapy was a predictor of being disease-free off-treatment (p = 0.03). No cytogenetic abnormalities developed, but myelofibrosis occurred 4 months after eltrombopag therapy in one non-responder with very-severe disease. The first 3 months' response to adjunctive eltrombopag may guide to the safe and effective use for the cure of disease, although prospective trials are needed to determine its long-term effects.

Recent advances in the diagnosis and treatment of pediatric acquired aplastic anemia

Acquired aplastic anemia (AA) in children is a rare bone marrow failure that requires several special considerations for its diagnosis and treatment compared with that in adults. The most common issue is the differential diagnosis with refractory cytopenia of childhood and inherited bone marrow failure syndromes, which is crucial for making decisions on the appropriate treatment for pediatric AA. In addition to detailed morphological evaluation, a comprehensive diagnostic work-up that includes genetic analysis using next-generation sequencing will play an increasingly important role in identifying the underlying etiology of pediatric AA. When discussing treatment strategies for children with acquired AA, the long-term sequelae and level of hematopoietic recovery that affect daily or school life should also be considered, although the overall survival rate has reached 90% after immunosuppressive therapy or hematopoietic cell transplantation (HCT). Recent advances in HCT for pediatric patients with acquired AA have been remarkable, with the successful use of upfront bone marrow transplantation from a matched unrelated donor, unrelated cord blood transplantation or haploidentical HCT as salvage treatment, and fludarabine/melphalan-based conditioning regimens. This review discusses current clinical practices in the diagnosis and treatment of acquired AA in children based on the latest data.

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.

Single-cell RNA Sequencing Reveals Novel Cellular Factors for Response to Immunosuppressive Therapy in Aplastic Anemia

Aplastic anemia (AA) is a lethal hematological disorder; however, its pathogenesis is not fully understood. Although immunosuppressive therapy (IST) is a major treatment option for AA, one-third of patients do not respond to IST and its resistance mechanism remains elusive. To understand AA pathogenesis and IST resistance, we performed single-cell RNA sequencing (scRNA-seq) of bone marrow (BM) from healthy controls and patients with AA at diagnosis. We found that CD34+ early-stage erythroid precursor cells and PROM1+ hematopoietic stem cells were significantly depleted in AA, which suggests that the depletion of CD34+ early-stage erythroid precursor cells and PROM1+ hematopoietic stem cells might be one of the major mechanisms for AA pathogenesis related with BM-cell hypoplasia. More importantly, we observed the significant enrichment of CD8+ T cells and T cell-activating intercellular interactions in IST responders, indicating the association between the expansion and activation of T cells and the positive response of IST in AA. Taken together, our findings represent a valuable resource offering novel insights into the cellular heterogeneity in the BM of AA and reveal potential biomarkers for IST, building the foundation for future precision therapies in AA.

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.

First-line immunosuppressive therapy with rATG and CsA for severe aplastic anemia: 15 years' experience

Rabbit antithymocyte globulin (rATG) instead of horse ATG has been used for severe aplastic anemia (SAA) patients in China. This study aimed to investigate the hematologic responses and long-term overall survival (OS) outcomes in SAA patients who received rATG and cyclosporine as first-line immunosuppressive therapy. We analyzed data of 542 SAA patients treated with this therapy between 2005 and 2019. The median age was 20 (range, 2-80) years, and the median follow-up time was 45.5 (range, 0.1-191.4) months. The early mortality rate was 3.9%. The overall response rates (ORRs) were 40.2%, 56.1%, and 62.4% at 3, 6, and 12 months, respectively. The 6- and 12-month ORR of patients treated with 3 mg/kg/d of rATG in 2015-2019 seemed higher than that of patients treated with 3.5-3.75 mg/kg/day in 2005-2014 (60.2% vs. 54.9%, P = 0.30 and 69.9% vs. 60.1%, P = 0.049, respectively). The 10-year cumulative incidences of relapse and clonal evolution were 10.6 ± 2.9% and 7.5 ± 1.5%, respectively. The 10-year OS rate and event-free survival rate were 80.1 ± 2.1% and 75.6 ± 3.7%, respectively. Age, disease severity, treatment periods, and the interval from diagnosis to IST were independent predictors of OS. In conclusion, 3 mg/kg/day rATG is effective as first-line treatment for SAA.

A New Immunosuppressive Therapy for Very Severe Aplastic Anemia in Children with Autoantibodies

OBJECTIVE

At present, a number of very severe aplastic anemia (VSAA) patients cannot receive hematopoietic stem cell transplantation (HSCT) or standard immunosuppressive therapy (IST) due to the high cost of therapy, shortage of sibling donors, and lack of resources to support the HSCT. In addition, some VSAA patients with autoantibodies have no life-threatening infections or bleeding at the time of initial diagnosis. Considering the disease condition, economics and other factors, the present study designed a new and relatively mild treatment strategy: cyclosporine A plus pulsed high-dose prednisone (CsA+HDP).

METHODS

The present study retrospectively analyzed 11 VSAA patients, who were treated with CsA+HDP in our hospital from August 2017 to August 2019.

RESULTS

The median follow-up time for these patients was 24.9 months. The overall response rate was 54.5% (6/11) at six months after the initiation of IST and 81.8% (9/11) at deadline. Five patients achieved complete remission and four patients met the criteria for partial response at the last follow-up. The median time to response for responders was 110 days. Three patients underwent HSCT due to the poor effect of CsA+HDP or to find a suitable transplant donor. Recurrence and clonal evolution were not found in any of these patients. The estimated 3-year overall survival rate and 3-year failure-free survival rate were 100.0% and 72.7%, respectively. In addition, the results revealed that the cyclosporine-prednisone-associated toxicity was mild and well-tolerated by most patients.

CONCLUSION

The novel CsA+HDP regimen has good therapeutic effect and safety for VSAA patients with autoantibodies, who have no serious life-threatening infections or bleeding at the time of initial diagnosis.

Prospective validation of the provisional entity of refractory cytopenia of childhood, proposed by the World Health Organization

In 2008, the World Health Organization proposed a new entity of childhood myelodysplastic syndrome (MDS), which was referred to as refractory cytopenia of childhood (RCC). However, whether this morphological classification reflects clinical outcomes remains unclear. We performed a prospective evaluation of bone marrow morphology in 252 children with acquired bone marrow failure between 2009 and 2013. Of 252 patients, 63 were diagnosed with aplastic anaemia (AA), 131 with RCC without multilineage dysplasia (RCC-w/o-MLD) and 58 with RCC with MLD (RCC-MLD). One patient with AA, three with RCC-w/o-MLD and nine with RCC-MLD presented with chromosomal abnormalities at diagnosis (P = 0·001). The response rates to immunosuppressive therapy (IST) at 6 months and the cumulative incidence of clonal evolution at 5 years did not significantly differ among the three groups. A multivariate analysis revealed that the morphological classification of RCC-MLD was a significant risk factor for secondary graft failure after haematopoietic cell transplantation (HCT) (P = 0·003). In view of these findings, RCC could be divided into two categories, RCC-w/o-MLD and RCC-MLD, because children with this condition exhibited a distinct morphology, frequent chromosomal abnormalities at diagnosis and a high frequency of secondary graft failure after HCT.

Relationship between plasma rabbit anti-thymocyte globulin concentration and immunosuppressive therapy response in patients with severe aplastic anemia

OBJECTIVES

Patients with acquired aplastic anemia (AA) without HLA-matched sibling donors or aged >40 years receive immunosuppressive therapy (IST) with anti-thymocyte globulin (ATG). We investigated the relationship between plasma rabbit ATG (r-ATG) concentration and IST response.

METHODS

From May 2012 to October 2017, 81 patients with severe AA who required initial IST were included. A 1:1 block randomization was employed for 2.5 and 3.5 mg/kg doses of r-ATG.

RESULTS

No significant difference in response rates was observed between the 2.5 and 3.5 mg/kg groups (63% vs. 58%, P = .894). Median r-ATG concentrations on days 14 and 28 after IST were 15.2 (0.0-97.7) and 1.8 (0.0-74.9 µg/mL), respectively. According to r-ATG concentration, response rates were significantly higher in the group with higher r-ATG concentration than in those with lower r-ATG concentration (day 14, 88% vs. 52%; P = .006 and day 28, 79% vs. 46%; P = .005). In multivariate analysis, higher r-ATG concentrations at day 28 were independent predictors of favorable response to IST at 6 months (odds ratio, 0.29; 95% confidence interval, 0.09-0.93; P = .037).

CONCLUSIONS

The present data indicate that higher r-ATG concentration at day 28 resulted in improved IST response.

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.