Immunosuppressive Therapy For Aplastic Anemia Research Articles

Relapse and transformation to myelodysplastic syndrome and acute myeloid leukemia following immunosuppressive therapy for aplastic anemia is more common as compared to allogeneic stem cell transplantation with a negative impact on survival.

We studied the incidence of relapse, transformation to myelodysplastic syndrome/acute myeloid leukemia, and survival in patients with aplastic anemia (AA) surviving more than 1year after ATG/ALG-based immunosuppressive therapy (IST) between 1985 and 2020. Four-hundred seventy patients (413 adults and 57 children) were studied, and data were compared with 223 patients who underwent matched sibling donor transplant (MSD HSCT). Median follow-up is 50months (12-359). Relapse occurred in 21.9% at a median time of 33.5months (5-228) post IST. Twenty-six (5.5%) patients progressed to PNH, while 20 (4.3%) evolved to MDS/AML. Ten-year estimated overall survival (OS) is 80.9 ± 3% and was significantly better in patients without an event (85.1 ± 4%) compared to relapse (74.6% ± 6.2%) or clonal evolution (12.8% ± 11.8%) (p = 0.024). While the severity of AA (p = 0.011) and type of ATG (p = 0.028) used predicted relapse, only age at IST administration influenced clonal evolution (p = 0.018). Among HSCT recipients, relapse rates were 4.9% with no clonal evolution, and the 10-year OS was 94.5 ± 2%. In patients who survived 1year following IST, outcomes were good except with clonal evolution to MDS/AML. These outcomes, however, were still inferior compared to matched sibling donor HSCT.

Real-world outcomes with immunosuppressive therapy for aplastic anemia in patients treated at the University of Michigan.

Aplastic anemia (AA) is a rare bone marrow failure disorder that is treated with either allogeneic stem cell transplant or immunosuppressive therapy (IST) consisting of antithymocyte globulin (ATG), cyclosporine (CSA), and eltrombopag. While outcomes are favorable in younger patients, older patients (>60) have significantly worse long-term survival. The dose of ATG is often reduced in older patients and those with multiple comorbidities given concerns for tolerability. The efficacy and safety of dose-attenuated IST in this population is largely undescribed. We performed a retrospective review of patients with AA treated with IST. Our analysis was confounded by changes in practice patterns and the introduction of eltrombopag. We identified 53 patients >60 years old, of which, 20 received dose-attenuated IST, with no statistically significant difference in overall survival between full and attenuated dose cohorts. Overall response rates in both cohorts were similar at 6 months at 71% and 68%. There were more documented infectious complications in the full dose cohort (13 vs. 3). This supports the consideration of dose-attenuated IST in older patients with concerns about tolerance of IST. Lastly, our data confirmed favorable outcomes of younger patients receiving IST, especially in combination with eltrombopag.

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.

Real-World Outcomes with Immunosuppressive Therapy for Aplastic Anemia in Patients Treated at the University of Michigan

IntroductionAplastic anemia is a challenging disease to treat due to its rarity and severity. The current standard of care for severe and very severe aplastic anemia includes consideration of frontline allogeneic stem cell transplant (ASCT) in patients who are under 40 years of age and have an HLA-matched sibling. For patients who do not meet this criteria, immunosuppressive therapy (IST) consisting typically of horse antithymocyte-globulin (ATG) and cyclosporine (CsA) is considered, with recent data supporting the addition of eltrombopag. The main risks of IST are infusion reactions, serum sickness, kidney injury, and infection. While it is generally well tolerated in younger patients, older patients have historically been treated with transfusion support alone due to concerns for higher complications. Unfortunately, data to support clinical decisions regarding these concerns is limited, with small studies showing that reduced dosing or attenuated doses of ATG with or without CsA is safe and can be effective. At the University of Michigan, we have been treating older patients with attenuated doses of ATG +/- CsA since the late-2000s and have recently added eltrombopag to our standard of care. Herein, we present the results of our experience using IST to treat aplastic anemia, specifically presenting our outcomes in patients over 60 years old at the time of initiation of IST.MethodsWe used the Electronic Medical Record Search Engine (EMERSE) to query patients with aplastic anemia who were treated at the University of Michigan between 1995 and 2021. Patients included in our analysis were diagnosed with idiopathic aplastic anemia or hepatitis-associated aplastic anemia, were 18 years or older at the date of initiating IST, were treated with IST first-line, had adequate physician follow up at the University of Michigan, and were reported as being complaint with IST. Patients diagnosed or with high concern for hypoplastic myelodysplastic syndrome (MDS) were excluded in addition to those who received treatment for paroxysmal nocturnal hemoglobinuria (PNH). Statistical analysis was performed using SPSS Statistics v.27 (IBM, 2020).ResultsWe identified 62 patients aged 18 - 60 and 54 patients over 60 years old who met inclusion criteria. Descriptive statistics of the two cohorts are available in Table 1. All patients in our study received horse ATG in addition to cyclosporine. 63% of patients over 60 received full dose horse ATG (20mg/kg for 5 days) and 37% received attenuated horse ATG (20mg/kg for 5 days), while 46% received eltrombopag as part of their IST. OS was superior in patients 18-60 receiving IST with median OS NR vs. 2760 days (Figure 1; p=0.009). In patients over 60, no difference in OS was observed in those who received attenuated (3646 days) vs. full dose IST (2760 days) (Figure 2, p=0.83). Lastly, no difference in median OS was seen in patients > 60 years old who received eltrombopag compared to those who did not (2821 vs 2760 days, Figure 3, p=0.795).Using a Chi-squared test, no statistically significant differences in rates of PR at 12 months, CR at 12 months, primary refractory disease, febrile neutropenia within 6 months of IST, bacterial infections within 6 months IST, and viral infections within 6 months of IST were noted between those who received dose attenuated ATG and those who received full dose ATG in patients > 60. PR in older patients was 48% (12) and 36% (9) at 3 and 12 months with eltrombopag, compared to 40% (10) and 36% (9) without. CR in older patients was 12% (3) and 16% (4) with eltrombopag at 3 and 12 months, compared to 12% (3) and 12% (3) without. In patients > age 60 who received dose attenuated IST, the addition of eltrombopag did not affect OS (Figure 4). A trend toward better OS was seen in patients 18-60 who received eltrombopag, but this was not statistically significant (Figure 5).DiscussionIn conclusion, we present our experience using IST to treat aplastic anemia at the University of Michigan. Dose attenuated IST has been proposed as a potential option for elderly patients, but we found no significant difference in OS, rates of response, or rates of infection between patients who received full dose and those who did not. There was also a trend toward improved survival with the addition of eltrombopag in younger patients, but additional follow up time is needed. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

A Nationwide Survey of Lower Risk Myelodysplastic Syndromes in Japan

A Nationwide Survey of Lower Risk Myelodysplastic Syndromes in Japan

The predictive value of pre-treatment paroxysmal nocturnal hemoglobinuria clone on response to immunosuppressive therapy in patients with aplastic anemia: a meta-analysis

ABSTRACT Background Although pre-treatment paroxysmal nocturnal hemoglobinuria (PNH) clone has been reported in a fraction of aplastic anemia (AA) for a long time, its predictive value on response to immunosuppressive therapy (IST) remained debatable. Therefore, we conducted a meta-analysis to elaborate this issue. Methods The identified articles were retrieved from five English databases PubMed, EMBASE, Web of Science, Medline, the Cochrane Library, and four Chinese databases Weipu, Wangfang, China National Knowledge Infrastructure (CNKI), and SinoMed. We extracted odds ratios (ORs) and the corresponding 95% confidential intervals (CIs) for response to IST in AA patients with pre-treatment PNH clone versus those without from the available studies. Results Twelve studies covering 1787 patients were included this meta-analysis. The pooled ORs indicated that the pre-treatment PNH clone had no impact on 3-month response (pooled OR: 1.323, 95% CI: 0.260–6.735, p = 0.736), 6-month response (OR: 1.668, 95% CI: 0.802–3.470, p = 0.171), and overall response (OR: 2.220, 95% CI: 0.870–5.665, p = 0.095), including overall response in pediatric patients (OR: 1.919, 95% CI: 0.378–9.738, p = 0.432). However, pre-treatment PNH clone had a favorable impact on 12-month response (OR: 2.725, 95% CI: 1.525–4.870, p = 0.001). Conclusion Pre-treatment PNH clone is associated with favorable 12-month response to IST in AA, the underlying mechanism needs further exploring.

High Natural Killer Cell Count at Diagnosis Predicts a Good Response to Immunosuppressive Therapy in Aplastic Anemia

Introduction: Aplastic anemia (AA) is an autoimmune-mediated disease with a complex mechanism. Innate as well as acquired immune system have been considered to participate in its pathogenesis. Although several studies have demonstrated the role of T and B cells in AA, there is limited research focusing on natural killer (NK) cells, which are important in innate and adaptive immune system. NK cells interact with T cells and alter their immune responses in a variety of diseases. Recent investigation suggests that NK cells serve immunoregulatory roles by attenuating autologous CD8+ T-cell response in AA (Chen et al. Cell Immunol 335:6-14, 2019). Here we assessed the kinetics of NK cells before and after immunosuppressive therapy (IST) in patients with AA to determine the association between NK cells and clinical courses. Methods: Patients with severe AA, in Japan, who required IST as first-line therapy were prospectively enrolled between May 2012 and October 2017. The IST regimen comprised rabbit anti-thymocyte globulin (ATG, thymoglobulin®, 2.5 or 3.5 mg/kg/day for 5 days), cyclosporine A (6 mg/kg/day for minimum 6 months), and methylprednisolone (2 mg/kg/day for 5 days) with subsequent tapering of the dose for 28 days. Flow cytometry was used to assess lymphocyte subsets, consisting of CD3+, CD4+, and CD8+ T cells, CD19+ B cells, CD56+ NK cells, and CD4+CD25+CD127+ regulatory T cells (Tregs), before and after ATG administration on days 0, 14, 28, 60, 90, 120, and 180. Plasma rabbit ATG levels were measured using a rabbit IgG ELISA kit on days 14 and 28 (Bethyl Laboratories, Montgomery, TX, USA). Receiver-operator characteristic (ROC) curves were generated to differentiate between response and no response to IST. Results: A total of 81 patients (aged 1.7-67.9 years) were randomized; 43 and 38 patients received 2.5 and 3.5 mg/kg of r-ATG, respectively. Median follow-up duration was 445 days (range; 183-2165 days) from first ATG infusion. After 6 months, 50 patients (58%) responded to the therapy, including 4 (5%) who achieved a complete response and 45 (56%) a partial response. The response rates did not differ significantly between the two dosages in ATG groups at 6 months (2.5 mg/kg, 63% vs. 3.5 mg/kg, 58%, P = 0.820). The median absolute number of NK cells before IST was 92/µL (0-1,085/µL). To judge patients' responses to IST, we defined 138/µL as the absolute number of NK cells count before IST as the cut-off value using ROC curves. The response rate of patients with higher NK cells (≥ 138 /mL) to IST at 6 months was significantly higher than those with lower NK cells (Figure 1, < 138 /mL, 78% vs. 52%, P = 0.031). Multivariate logistic regression analysis identified the absolute number of NK cells before IST and reticulocyte at diagnosis (odds ratio [OR] = 0.16; 95% confidence interval [CI], 0.04-0.62; P = 0.008 and OR = 0.20; 95% CI, 0.06-0.67; P = 0.009, respectively) and the r-ATG plasma concentration on day 28 (OR = 0.11; 95% CI, 0.03-0.39; P = 0.001) as independent predictors of response to IST. The median absolute number of NK cells on days 90, 120, and 180 after IST was higher in the responders (113/mL, 118/mL, and 159/mL, respectively) than in the non-responders (57/mL, 53/mL, and 64/mL, P = 0.001, P<0.001, P<0.001, respectively). On the other hand, the recoveries in the number of CD3+, CD4+, CD8+, and Tregs cells were similar in both groups (Figure 2). Three relapses (among 21 responders) in higher NK cells group, and four relapses (among 28 responders) in lower NK cells group were observed. No patients developed clonal evolution in both groups. Two patients in the lower NK cell group died after IST. The etiologies of death included infection and unknown causes. Transplantation-free survival (TFS), failure-free survival (FFS), and overall survival (OS) at two years were similar between the higher and lower NK cell groups [TFS, 90% (95% CI, 64%−97%) vs. 78% (95% CI, 63%−87%); P = 0.147; FFS, 66% (95% CI, 45%−81%) vs. 50% (95% CI, 35%−62%); P = 0.147; OS, 100% (95% CI, 100%−100%) vs. 94% (95% CI, 76%−98%); P = 0.277]. Conclusions: The current study indicates that NK cells play a role in the pathogenesis of AA and may be the predictors of response to IST. Recovery of NK cell count correlated with hematopoietic recovery following IST, indicating that they may be used as markers to assess disease activity, treatment response and relapse. Disclosures Yamazaki: Novartis Pharma K.K.: Honoraria; Sanofi K.K.: Honoraria; Nippon Shinyaku Co., Ltd.: Honoraria. Nakao:Ono Pharmaceutical: Honoraria; Kyowa Kirin: Honoraria; Alaxion Pharmaceuticals: Honoraria; Ohtsuka Pharmaceutical: Honoraria; Celgene: Honoraria; Daiichi-Sankyo Company, Limited: Honoraria; Janssen Pharmaceutical K.K.: Honoraria; SynBio Pharmaceuticals: Consultancy; Novartis Pharma K.K: Honoraria; Bristol-Myers Squibb: Honoraria; Takeda Pharmaceutical Company Limited: Honoraria; Chugai Pharmaceutical Co.,Ltd: Honoraria.

15-PGDH Inhibition Mitigates Aplastic Anemia Severity

Acquired aplastic anemia (AA) is a primary bone marrow (BM) failure syndrome in which hematopoietic stem cells (HSC) are depleted in an immune-mediated fashion. AA is rare, with an estimated 900 new cases per year in the U.S., and onset is typically in childhood or adolescence. AA is fatal if untreated and poses a high burden of frequent, long-term transfusions and associated complications. The current standard of care for severe AA is allogeneic stem cell transplantation for young patients who have a matched related donor or immunosuppressive therapy (IST) for those who do not. Among other toxicities, prolonged neutropenia, immune suppression and the resulting risk of severe infections remain challenges in managing even AA patients responding to standard therapies. These challenges are more critical in severe AA patients refractory to front line therapy. Importantly, this disorder is also associated with clonal evolution of myeloid progenitor cells, and the development of myelodysplastic syndrome and acute myeloid leukemia in 10-20% of cases (Yoshizato, N Engl J Med, 2015). Therefore, additional therapies to either block immune-mediated BM destruction, or to accelerate hematologic recovery in patients receiving IST, are needed. Inhibiting 15-hydroxyprostaglandin dehydrogenase (15-PGDH) using the small molecule SW033291 (PGDHi) in mice was recently shown by Zhang et al. to increase BM prostaglandin E2 (PGE2) levels, expand HSC numbers, accelerate hematologic reconstitution following BM transplantation, and synergize with G-CSF for neutrophil recovery (Zhang, Science, 2015). To determine whether PGDHi is capable of improving hematopoiesis in acquired AA, we induced immune-mediated BM failure in mice (Chen, Blood, 2004) and treated with SW033291 starting at day 4 post-induction. PGDHi mitigated both neutropenia and thrombocytopenia, increased phenotypic and functional BM HSC and progenitor cells, and significantly extended survival compared to vehicle-treated mice in the same cohort. Analysis of peripheral blood serum revealed no impact of PGDHi on circulating IFNγ levels, however. These data suggest that PGDHi protects hematopoietic stem cell function in acquired AA. There was an observed trend for lower CD8+ FasL+ T cells in the BM of PGDHi treated mice. Experiments are underway to determine if PGDHi reproducibly impairs T cell activation and modulates the inflammatory cytokine milieu in the BM. A comparison of PGDHi and Cyclosporine (CsA), the backbone of IST in AA, is also underway to examine if PGDHi can augment IST efficacy using lower, better tolerated cyclosporine dosing. In this murine model, low dose (10mg/kg) CsA, unlike standard dose (50mg/kg) CsA, did not cause kidney or liver toxicity as assessed in peripheral blood serum, but failed to protect against neutropenia and thrombocytopenia. Preliminary results demonstrate that dual PGDHi and low dose Cyclosporine administration significantly enhances neutrophil and platelet recovery, achieving responses similar to that of standard dose IST, thus suggesting that PGDHi can complement IST to accelerate hematologic recovery and reduce morbidity in severe AA. Disclosures Markowitz: Rodeo Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Desai:Rodeo Therapeutics: Consultancy.

Immunosuppressive therapy for aplastic anemia: a single-center experience from western India

Immunosuppressive therapy (IST) with antithymocyte globulin (ATG) and cyclosporine A (CsA) is the first-line therapy for acquired aplastic anemia (AA) in those not suitable for bone marrow transplant. Horse ATG (hATG) is preferred for this purpose, but its use is often impeded by shortages and costs. Being a rare disease, there is limited data on this therapy. This study aimed to evaluate this therapy in a large cohort of AA patients from western India. We retrospectively analyzed AA patients who received an indigenous preparation of hATG along with CsA as first-line treatment, between 2012 and 2015, at our center and evaluated the response, survival, and occurrence of adverse events. The response was further assessed separately for adults and children. During the period, 91 AA patients (4 non-severe, 57 severe and 30 very severe) were treated with IST. At 2 years, 23.5% adults and 39.1% children showed complete response and an overall of 68.1% cases became transfusion independent. More than half of the patients developed febrile neutropenia while roughly one sixth of the patients developed gum hypertrophy and/or hypertension. Two patients had clonal evolution. Mortality rate was calculated to be 31%; most common causes of death were infection and intracranial hemorrhage. The results of the study substantiate the effectiveness of IST in AA, using an inexpensive indigenous preparation of hATG along with CsA.

Predicting Response to Immunosuppressive Therapy in Patients with Acquired Aplastic Anemiausing EGFR and TWIST1 Expression Levels

INTRODUCTIONEGFR (epidermal growth factor receptor) is important for the proliferation of stem cells across the body including the hematopoietic niche. However, the role of EGFR in aplastic anemia and subsequent responses to standard-of-care therapy is unknown.TWIST is a basic helix-loop-helix transcription factor recently found to regulate the hematopoietic stem cell (HSC) niche. The HSC niche is important for treatment of aplastic anemia. Telomerase and associated gene mutations have been reported in aplastic anemia, but these mutations are not present in all subjects and hence the cellular mechanisms of therapeutic responses observed is not explained by deregulated telomerase or associated genes. OBJECTIVETo investigate the utility of measuring gene expression levels of EGFR and TWIST on the clinical response to immunosuppressive therapy in acquired Aplastic anemia patients without mutations in telomerase gene. METHODSThis was a single institution analysis of patients with acquired Aplastic anemia, in the age group of 16 to 60 years, who were treated with immunosuppressive therapy between June 2014 to December 2015. 15 patients who did not have homozygous TERT (telomerase catalytic subunit) or DKC (Dyskeratosiscongenita) mutations as determined by sequencing were included in this study. Diagnosis of Aplastic anemia was established with bone marrow aspiration and biopsy with normal cytogenetics. PNH was ruled out in all patients. 7 patients had very severe aplasticanemia (VSAA) and 8 had severe aplastic anemia. There were 11 males and 4 females.Following informed consent, we performed RT-PCR analysis on harvested RNA from each patient and measured levels of TWIST and EGFR expression compared to that of normal samples (n=6).15 patients underwent immunosuppressive therapy with horse ATG at 40mg/kg/day for 4 days followed by oral cyclosporine for at least 3 months. Clinical response was assessed at 3 months and 6 months post ATG administration. Total RNA from healthy donors (6) were used to establish normal baseline gene expression values. RESULTSOut of the 15 patients that received ATG infusion, 10 patients (66%) had an 8-fold reduced expression of EGFR and TWIST compared to normal control. We grouped the study subjectsintoEGFR/TWIST-low (C1) and EGFR/TWIST-normal(C2). C1 subjects were younger in age (average age 29) compared with C2 (average age 40) andwere more likely to be diagnosed with a more severe form of the disease (VSAA). In the C1 group, all patients responded well to treatment with 4 (80%) patients achieving CR and 1 patient achieving a partial response. In C2, 8 (80%) patients showed no response, with 2 patients showing a partial response at the end of 6 months. CONCLUSIONOur data suggests that EGFR and TWIST may have significant impact on the ability of the hematopoietic stem cell niche to respond to immunosuppressive therapy in aplastic anemia, particularly in the absence of telomerase mutations. Therefore, low expression levels of EGFR/TWIST at diagnosis in may be useful in predicting response to immunosupressive therapy and thereby influence treatment decisions in aplastic anemia patients. DisclosuresNo relevant conflicts of interest to declare.

Association of Human Leukocyte Antigen DRB1*15 and DRB1*15:01 Polymorphisms with Response to Immunosuppressive Therapy in Patients with Aplastic Anemia: A Meta-Analysis.

This study aimed to review and quantitatively analyze (1) the association of aplastic anemia (AA) with human leukocyte antigen (HLA)-DRB1*15 and HLA-DRB1*15:01 polymorphisms and (2) the association of HLA-DRB1*15 and HLA-DRB1*15:01 polymorphisms with response to immunosuppressive therapy (IST) in AA. Published studies have reported conflicting and heterogeneous results regarding the association of HLA-DRB1*15 and HLA-DRB1*15:01 polymorphisms with response to IST in AA. The PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, Chinese BioMedical Literature, Wangfang and Chinese Social Sciences Citation Index databases were searched. All relevant publications were searched through December 2015. Odds ratio (OR), risk ratio (RR), and 95% confidence intervals (CI) for the comparison between case–control or cohort studies were evaluated. Finally, 24 articles were identified. For HLA-DRB1*15 and HLA-DRB1*15:01, the OR (95% CI) was 2.24(1.33–3.77), P < 0.01 and 2.50(1.73–3.62), P < 0.01, respectively; and the overall pooled RR was 1.72 (1.30–2.29), P < 0.01 and 1.59 (1.29–1.96), P < 0.01, respectively. Statistical evidence showed no publication bias (P > 0.05). Sensitivity analyses revealed that the results were statistically robust. The meta-analysis suggested that HLA-DRB1*15 and HLA-DRB1*15:01 polymorphisms might be associated with increased AA risk in Asians. IST might be more effective in HLA-DRB1*15+ and HLA-DRB1*15:01+ Asian patients with AA than in HLA-DRB1*15− and HLA-DRB1*15:01− Asian patients with AA. Future studies with adequate methodological quality on gene–gene and gene–environment interactions and gene treatment may yield valid results.

Deep phenotyping of Tregs identifies an immune signature for idiopathic aplastic anemia and predicts response to treatment

AbstractIdiopathic aplastic anemia (AA) is an immune-mediated and serious form of bone marrow failure. Akin to other autoimmune diseases, we have previously shown that in AA regulatory T cells (Tregs) are reduced in number and function. The aim of this study was to further characterize Treg subpopulations in AA and investigate the potential correlation between specific Treg subsets and response to immunosuppressive therapy (IST) as well as their in vitro expandability for potential clinical use. Using mass cytometry and an unbiased multidimensional analytical approach, we identified 2 specific human Treg subpopulations (Treg A and Treg B) with distinct phenotypes, gene expression, expandability, and function. Treg B predominates in IST responder patients, has a memory/activated phenotype (with higher expression of CD95, CCR4, and CD45RO within FOXP3hi, CD127lo Tregs), expresses the interleukin-2 (IL-2)/STAT5 pathway and cell-cycle commitment genes. Furthermore, in vitro–expanded Tregs become functional and take on the characteristics of Treg B. Collectively, this study identifies human Treg subpopulations that can be used as predictive biomarkers for response to IST in AA and potentially other autoimmune diseases. We also show that Tregs from AA patients are IL-2–sensitive and expandable in vitro, suggesting novel therapeutic approaches such as low-dose IL-2 therapy and/or expanded autologous Tregs and meriting further exploration.

Clinical significance and origin of leukocytes that lack HLA-A allele expression in patients with acquired aplastic anemia.

To gain insight into the origin and clinical significance of leukocytes that lack human leukocyte antigen A (HLA-A) allele expression caused by a copy-number-neutral loss of heterozygosity in the short arm of chromosome 6 in patients with acquired aplastic anemia (AA),weused a high-sensitivity flow cytometry assay to investigate the presence of HLA-A allele-lacking leukocytes(HLA-LLs) in 144 AA patients. HLA-LLs, accounting for0.2-99.8% of each leukocyte population, were detected in 18 of 71 (25.4%) newly diagnosed patientsand in 25 of 73 (34.2%) previously treated patients. The lineage combination patterns of the HLA-LLs in the 43 HLA-LL(+)patients were granulocytes (Gs), monocytes (Ms), Bcells (Bs), and Tcells (Ts; GMBT) in 13 cases, GMB in 16 cases, GM in 11 cases, and B alone in three cases. The response rate to antithymocyte globulin plus cyclosporine therapy (100%) and the 2-year, failure-free survivalrate (100%) in 8 newly diagnosed HLA-LL(+) patients were significantly higher than in 23 HLA-LL(-) patients (52.2% for both). These data suggest that HLA-LLs are a useful marker of the presence of immune pathophysiology in AA and that T-cell attacks against hematopoietic progenitor cells, rather than against hematopoietic stem cells, can trigger bone marrow failure in AA patients.

Biomarkers for predicting clinical response to immunosuppressive therapy in aplastic anemia.

The decision to select hematopoietic stem cell transplantation (HSCT) or immunosuppressive therapy (IST) as initial therapy in acquired aplastic anemia (AA) is currently based on patient age and the availability of a human leukocyte antigen (HLA)-matched donor. Although IST is a promising treatment option, the ability to predict its long-term outcomes remains poor due to refractoriness, relapses, and the risk of clonal evolution. Several predictive biomarkers for response to IST have been posited, including age, gender, pre-treatment blood cell counts, cytokines, gene mutations, paroxysmal nocturnal hemoglobinuria (PNH), and telomere length (TL). While previous studies have provided substantial biological insights into the utility of IST, the prognostic power of the reported biomarkers is currently insufficient to contribute to clinical decision making. Recently, a large retrospective analysis proposed the combination of minor PNH clones and TL as an efficient predictor of IST response. Identification of a reliable predictor would provide a useful tool for determining the most appropriate treatment choice for AA patients, including up-front HSCT from HLA-matched unrelated donor. The present review summarizes studies evaluating the utility of biomarkers in predicting the clinical response to IST of patients with AA, and provides a baseline for prospective studies aimed at validating previously reported biomarkers.

Fatal Epstein-Barr Virus Reactivation in an Acquired Aplastic Anemia Patient Treated with Rabbit Antithymocyte Globulin and Cyclosporine A.

Epstein-Barr virus (EBV) associated lymphoproliferative disorder (LPD) after immunosuppressive therapy for aplastic anemia (AA) is extremely rare in a nontransplant setting and has not been well described. This report describes a severe AA patient in whom fatal EBV-LPD developed after being treated with rabbit antithymocyte globulins (ATG) and cyclosporine A (CsA). An 81-year-old man was diagnosed as having severe AA. He was started on CsA followed by administration of ATG for five consecutive days. One month after the start of ATG, persistent fever which was not responsive to antibiotics or antifungal agents developed and atypical lymphocytes emerged in peripheral blood. Repeated blood cultures were negative. An extremely high level of EBV virus in his peripheral blood plasma was detected by means of a quantitative real-time PCR assay. Even after the cessation of CsA, the fever persisted and the peripheral atypical lymphocytes proliferated rapidly. The patient suffered from respiratory failure, liver dysfunction, and metabolic acidosis. Rituximab was administered without success and he died.

The optimal immunosuppressive therapy for aplastic anemia

Immunosuppressive treatment (IST) has been the most effective therapeutic modality for patients with aplastic anemia (AA) who are not eligible for allogeneic stem cell transplantation from HLA-matched siblings because of donor unavailability, old age, or comorbidities. The combination of horse anti-thymocyte globulin (ATG) with cyclosporine A (CsA) has shown satisfactory results for these patients, and so it has been regarded as the standard IST regimen. However, treatment failure including unresponsiveness, relapse, and occurrence of clonal evolution remains a major problem, although the results of IST have been improved in the past two decades. Many studies have been conducted to overcome these problems; however, they have yet to show any satisfactory results. This review will discuss immune-mediated pathophysiology of AA, which is associated with therapeutic targets of immunosuppressive agents and clinical outcomes of most commonly used IST regimens. Several trials to improve IST including the addition of other immunosuppressive agents or growth factors to standard IST regimen, comparison between horse ATG/CsA and rabbit ATG/CsA as first-line treatment, and promising alternative agents including alemtuzumab and eltrombopag will also be discussed, focusing on recently published literatures.

Immunosuppressive therapies in the management of acquired immune-mediated marrow failures

Immunosuppression is a key treatment strategy for patients suffering from aplastic anemia or related immune-mediated bone marrow failure syndromes. Several attempts have been performed to improve the standard immunosuppression regimen of horse antithymocyte globulin (h-ATG) and cyclosporine A (CyA). The addition of a third immunosuppression agent to h-ATG + CyA did not result in any improvement. Antilymphocyte agents other than h-ATG have been investigated. A rabbit-ATG preparation, which was known to be more immunosuppressive than h-ATG, resulted in markedly inferior outcome in a large randomized study from the National Institutes of Health. These data seem to be confirmed in additional experiences with rabbit-ATG from other groups. Cyclophosphamide and alemtuzumab have been proven to be biologically active in small studies, but available data suggest inferior outcomes when compared with h-ATG. All these alternative agents result in a more pronounced lymphocyte depletion, suggesting that the actual mechanisms of action of immunosuppressive therapy in aplastic anemia are not fully understood. Immunosuppression by h-ATG and CyA remains the standard of care for aplastic anemia patients lacking a low-risk transplant procedure, resulting in a 60-70% response rate. Rabbit-ATG, cyclophosphamide and alemtuzumab demonstrated a biological activity, but resulted in inferior outcome as compared with h-ATG; thus, they are not recommended as front-line therapy of aplastic anemia.

Colonic EBV-Associated Lymphoproliferative Disorder in a Patient Treated with Rabbit Antithymocyte Globulin for Aplastic Anemia

Epstein-Barr-virus- (EBV-) associated lymphoproliferative disorder (LPD) after immunosuppressive therapy for aplastic anemia (AA), in a nontransplant setting, has not been well described. We report one case of colonic EBV-LPD after a single course of immunosuppressive therapy for AA. The patient developed multiple colonic tumors 3 months after receiving immunosuppressive therapy, which consisted of rabbit antithymocyte globulin (ATG), cyclosporine, and methyl-predonisolone. The histological findings of biopsy specimens revealed that atypical lymphocytes had infiltrated colonic glands. Immunohistochemical staining for CD20 was positive, and in situ hybridization for EBV-encoded small RNAs was also positive. The EBV viral load in peripheral blood was slightly increased to 140/106 white blood cells. After the cessation of immunosuppressant, the colonic tumors spontaneously regressed, and the EBV viral load decreased to undetectable levels. This is the first report of the single use of rabbit ATG inducing colonic EBV-LPD. Because a single use of immunosuppressive therapy containing rabbit ATG can cause EBV-LPD, we should carefully observe patients receiving rabbit ATG for AA.

The Efficacy of Rabbit Antithymocyte Globulin (Thymoglobulin®) with Cyclosporin As First-Line Treatment in Aplastic Anemia,

Abstract 3430 Background:Antithymocyte globulin (ATG) is the drug of choice for immunosuppressive therapy (IST) in patients with aplastic anemia (AA) unsuitable for hematopoietic stem cell transplantation. The standard ATG preparation in AA had been horse ATG because of the larger experience and the results already reported with this preparation. Due to the unavailability of the horse ATG since 2006, rabbit ATG became the only available ATG preparation in Korea. But, there are only limited data about the therapeutic efficacy of rabbit ATG as first-line IST in AA. Method:We retrospectively investigated the outcome of 58 evaluable patients among 62 patients with AA treated with IST using rabbit ATG as front line between March 2006 and April 2010 at our institution. 70.7% of enrolled patients were very severe (n=18) or severe AA (n=23). All patients received rabbit ATG (Thymoglobulin®, 2.5mg/kg per day for 5 days) with methylprednisolone and cyclosporine A. Response rate (RR) was assessed at 3, 6, 9, 12 and 18 months after IST. Results:After IST, overall RR was 27.8%, 50.8%, 52.8%, 52.8% and 56.7% after 3, 6, 9, 12 and 18 months, respectively. Complete response (CR) rates were 0.8%, 1.8%, 5.6%, 9.6% and 21.2% after 3, 6, 9, 12 and 18 months, respectively. Median time to achieve partial response (PR) and CR were 93 (range; 12∼977 days) and 381 (range; 12–614) days. Among 31 responders, 10 patients (32.3%) relapsed. Median time between response and relapse were 396 days (range; 254∼681 days).Estimated overall survival and failure free survival at 3 years from ATG treatment were 85.8% and 42.8%, respectively. Age (>45) at the use of ATG was an independent predictor of overall survival and overall response (p=0.033 and 0.027) in univariate analysis. Other factors such as disease severity, pre-ATG hematological parameters (absolute lymphocyte count and absolute reticulocyte count) were not associated with overall survival and failure free survival. Conclusion:These data indicate that rabbit ATG was as effective as horse ATG based on other recently published data. But, the response time of rabbit ATG treatment is longer than that of horse ATG treatment. Especially, more than half of patients who achieved CR required time over 1 year after ATG treatment. Rabbit ATG can be effective IST regimen comparable to horse ATG, but it takes longer time to achieve sufficient response. Disclosures:No relevant conflicts of interest to declare.

Impending Ruptured Arteriosclerotic Abdominal Aortic Aneurysm in a Young Man Receiving Immunosuppressive Therapy for Aplastic Anemia

Impending Ruptured Arteriosclerotic Abdominal Aortic Aneurysm in a Young Man Receiving Immunosuppressive Therapy for Aplastic Anemia