Effect of antithymocyte globulin source on outcomes of bone marrow transplantation for severe aplastic anemia

Cyclophosphamide and horse anti-thymocyte globulin versus fludarabine, reduced cyclophosphamide and rabbit anti-thymocyte globulin conditioning regimen for allogeneic hematopoietic stem cell transplantation from matched sibling donors in patients with acquired aplastic anemia

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative treatment for acquired aplastic anemia (acquired AA) in young patients. The objective of the study was to compare patient outcomes after Cyclophosphamide and horse antithymocyte globulin (Cy-hATG) versus Fludarabine-cyclophosphamide and rabbit ATG (Flu-Cy-rATG) as part of conditioning regimen in allo-HSCT for acquired AA.

RESEARCH DESIGN AND METHODS

Descriptive retrospective study conducted on patients with acquired AA who received allo-HSCT from HLA-matched sibling donors between January 2008 and August 2022 after conditioning regimen with Cy-hATG or Flu-Cy-rATG.

RESULTS

A total of 121 patients were enrolled. Cumulative incidence of graft failure was 11.2% in Cy-hATG and 5.3% Flu-Cy-rATG group. There were no significant differences between the two groups in terms of acute GVHD, chronic GVHD, and transplant related mortality. Flu-Cy-rATG group was associated with significantly higher CMV and EBV reactivation(s) compared to Cy-hATG group (p = 0.008 and 0.035, respectively). After a median follow-up of 58 months, estimated overall survival, event-free survival, and graft rejection-free survival were not statistically different between the two groups.

CONCLUSIONS

In high-risk population, Flu-Cy-rATG is associated with comparable outcomes to Cy-hATG in allo-HSCT from MSD. However, it seems to be associated with significant risk of viral infections.

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.

Hematopoietic stem cell transplantation for B-thalassemia major with alemtuzumab

While matched related donor (MRD) allogeneic hematopoietic stem cell transplantation (HSCT) is a curative option for transfusion-dependent beta-thalassemia (TDT), the use of alternative sources has increased, resulting in the exploration of novel transplant-conditioning regimens to reduce the contribution of graft-versus-host disease (GVHD) and graft failure (GF) to transplant-related morbidity and mortality. Alemtuzumab is a CD52 monoclonal antibody that has been successfully incorporated into myeloablative conditioning regimens for other hematologic conditions, yet there have been limited studies regarding the use of alemtuzumab in HSCT for TDT. The purpose of this study was to evaluate engraftment, incidence of GVHD, and transplant related morbidity and mortality in patients with TDT who received alemtuzumab in addition to standard busulfan-based conditioning. The primary endpoint was severe GVHD-free, event-free survival (GEFS). Our cohort included 24 patients with a median age of 6.8 years (range 1.5-14.9). Eleven patients received a 10/10 MRD HSCT, eleven 10/10 unrelated donor (UD), and two mismatched UD. All patients achieved primary engraftment. For all patients, 5-year GEFS was 77.4% and 5-year overall survival (OS) was 91%. The 5-year cumulative incidence of GF (attributed to poor graft function) without loss of donor chimerism was 13.8% (95% CI: 4.5, 35.3). We report low rates of significant acute GVHD grade II-IV (12.5%) and chronic GVHD (4.4%). Younger age and MRD were associated with significantly improved GEFS, OS and EFS. Our results show that the use of alemtuzumab promotes stable engraftment, may reduce rates of severe GVHD, and results in acceptable GEFS, OS, and EFS.

Comparison of Different Rabbit Anti-Thymocyte Globulin Formulations in the Prophylaxis of Graft-Versus-Host Disease: A Systematic Review

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is a potentially curative treatment modality, frequently used for patients suffering from haematological malignancies. In the last two decades, there have been multiple randomised controlled trials (RCTs), review articles, and meta-analyses addressing the efficacy of rabbit anti-thymocyte globulin (r-ATG) as a graft-versus-host disease (GvHD) prophylaxis. Nevertheless, only a few aimed to compare the effectiveness of different r-ATG formulations. Since the last article we retrieved comparing different r-ATGs in GvHD prophylaxis dates back to 2017, we performed a systematic literature review of articles published since 2017 to this day, utilising PubMed, Scopus, Cochrane, and MEDLINE, with the main endpoints being prophylaxis of acute GvHD (aGvHD) and chronic GvHD (cGvHD). We subjected to scrutiny a total of five studies, of which four compared the differences between Thymoglobulin (ATG-T) and Grafalon (ATG-G), and one discussed the impact of ATG-T dose. Overall, cGvHD, aGvHD grades II-IV, TRM, OS, NRM, LFS, relapse, overall infections, and EBV reactivation do not seem to be affected by the type of utilised rATG. However, data on aGvHD grades III-IV, GRFS, moderate-severe cGvHD, and CMV reactivation is conflicting. Through our research, we sought to summarise the most recent findings concerning r-ATGs in allo-HCT, and provide insight into the differences between the targets and origin of various ATG formulations.

Comparison of haploidentical-allogeneic hematopoietic stem cell transplantation and intensive immunosuppressive therapy for patients with severe aplastic anemia with an absolute neutrophil count of zero: a retrospective study

A retrospective analysis was conducted based on the clinical data from 60 patients older than 16 years from January 2016 to January 2021. All the patients were newly diagnosed with severe aplastic anemia (SAA) with an absolute neutrophil count (ANC) of zero. We compared the hematological response and survival of haploidentical-allogeneic hematopoietic stem cell transplantation (HID-HSCT) (n = 25) and intensive immunosuppressive therapy (IST) (n = 35) treatments. At six months, the overall response rate and complete response were significantly higher in the HID-HSCT group than those in the IST group (84.0% vs. 40.0%, P = 0.001; 80.0% vs. 17.1%, P = 0.001). With a median follow-up of 18.5 months (4.3~30.8 months), patients in the HID-HSCT group had longer overall survival and event-free survival (80.0% vs. 47.9%, P = 0.0419; 79.2% vs. 33.5%, P = 0.0048). These data suggested that HID-HSCT might be an effective alternative treatment option for adult patients with SAA with an ANC of zero, which requires further validation in an additional prospective study.

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

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

HSCT with mismatched unrelated donors: Bone marrow versus peripheral blood stem cells sources in pediatric patients

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) from an unrelated HLA-mismatched donor (MMUD) is one of the alternatives where an HLA-matched donor is not found. The aim of this study was to compare bone marrow (BM) versus peripheral blood stem cells (PBSC) as hematopoietic rescue following allogeneic unrelated mismatched stem cell transplantation (MMUD).

METHODS

The patients were divided into two groups: 43 pediatric patients were treated with BM and 17 pediatric patients with PBSC. The study was registered at ClinicalTrials.gov NCT04598789.

RESULTS

The 3-year Overall Survival (OS) was 74% versus 31% (p = .0011). Transplant related mortality (TRM) was 16% versus 33% (p = .025), and relapse incidence (RI) was 16% versus 35% (p = .005). The day-100 acute Graft-versus-host disease (GvHD) incidence grade II-IV and III-IV was 30% versus 28% (p = NS) and 17% versus 17% (p = NS). The 3-year chronic GvHD incidence was 22% versus 33% (p = NS).

CONCLUSION

Despite all the limits of this retrospective study we were able to show how the combination of BM and ATG is able to prevent GvHDs and guarantee a high OS. Future studies addressing the issue of a post-transplant cellular therapy approach may potentially reduce relapses when GvHD is absent.

Retrospective Comparison of Efficacy and Safety of Rabbit Anti-Thymocyte Globulin and Porcine Anti-Lymphocyte Globulin in Patients With Acquired Aplastic Anemia Undergoing Hematopoietic Stem Cell Transplantation From Matched Sibling Donors

We compared the efficacy and safety of porcine anti-lymphocyte globulin (pALG) (n=140) and rabbit anti-thymocyte globulin (rATG) (n=86) in patients with acquired aplastic anemia (AA) receiving hematopoietic stem cell transplantation (HSCT) from matched sibling donors (MSD) in two transplantation centers in China ranging from 2005 to 2020. The groups had similar baseline characteristics except for a higher number of infused mononuclear cells (P<0.001) and a higher proportion of peripheral blood stem cells as graft sources (P=0.003) in the pALG group. The rates of neutrophil engraftment at day 28 (P=1), platelet engraftment at day 28 (P=0.228), bloodstream infection before engraftment (P=0.867), invasive fungal diseases (P=0.362), cytomegalovirus viremia (P=0.667), and graft rejection (P=0.147) were similar in the two groups. A higher cumulative incidence of grades II-IV acute graft versus host disease (aGvHD) at 100 days occurred in the pALG group (19% vs. 8%, P=0.035) while no significant differences in grades III-IV aGvHD (P=0.572), mild to severe chronic GvHD (cGvHD) (P=0.181), and moderate to severe cGvHD (P=0.586) were observed. The actuarial 5-year overall survival (OS), failure-free survival (FFS), and GvHD-free, FFS rates of the pALG group were 87% (95% confidence interval [CI], 82-93), 85% (95% CI, 80-92), and 78% (95% CI, 72-92) versus 91% (95% CI, 86-99) (P=0.33), 88% (95% CI, 82-97) (P=0.428), and 79% (95% CI, 72-90) (P=0.824) in the rATG group, respectively. A busulfan-containing conditioning regimen was the only adverse risk factor for OS and FFS in multivariate analysis. In conclusion, pALG is an alternative to rATG in patients with severe AA receiving MSD-HSCT. A prospective, large-sample study is needed to explore this therapy further.

HSCT with Mismatched Unrelated Donors (MMUD): A Comparison of Different Platforms for GvHD Prophylaxis

HSCT from an unrelated HLA-mismatched donor (MMUD) is one of the alternatives where an HLA-matched donor is not found. The aim of this study was to compare GvHD prophylaxis with anti-thymocyte globulin (ATG) vs. post-transplant cyclophosphamide (PT-Cy). Thirty-nine adult patients were uniformly treated with rabbit ATG-Cy-A-MTX and peripheral blood stem cell (PBSC) and 40 adult patients with PT-Cy-MMF-tacrolimus and PBSC. This retrospective study was registered at ClinicalTrials.gov NCT04598789. Three-year overall survival was 42% vs. 64% for ATG and PT-Cy (p < 0.0005), three-year treatment-related mortality (TRM) was 36% vs. 8% (p = 0.0033) and the three-year relapse incidence (RI) was 15% vs. 28% (p = NS), respectively. The incidences of day-100 GvHD graded II–IV and III–IV were 39% vs. 7% (p = 0.0006) and 11% vs. 0% (p = 0.04), respectively, whereas the three-year cGvHD incidences were 48% vs. 13% (p = 0.0005), respectively. We were able to show how PT-Cy can reduce the incidence of GvHDs and TRM in adults, but relapse remains an issue.

A comparative study of porcine antihuman lymphocyte globulin versus antithymocyte globulin-fresenius in an allogeneic hematopoietic cell transplantation conditioning regimen for severe aplastic anemia

OBJECTIVES

To compare the outcomes of antihuman T lymphocyte globulin (ATG-F) and porcine antihuman lymphocyte globulin (p-ALG) as part of a conditioning regimen in hematopoietic stem cell transplantation (HSCT) for severe aplastic anemia (SAA).

METHODS

we performed a retrospective analysis, evaluating the outcome of patients with SAA who received ATG-F based conditioning (n = 26) with those receiving p-ALG conditioning (n = 34).

RESULTS

The median time to neutrophil engraftment was 11 days (range, 8 - 38) and 11 days (range, 9 - 24) in the p-ALG and ATG-F groups (P = 0.857); the median platelet engraftment time was 15 (range, 9 - 330) days and 13 (range, 10 - 56) days (P = 0.155). There were no significant differences in grades II - IV acute graft-versus-host disease (aGVHD), grades III - IV aGVHD, chronic GVHD (cGVHD), and the moderate-severe cGVHD between the ATG-F and p-ALG groups (P>0.05).

DISCUSSION

Patients in the ATG-F group functioned significantly better on role-physical (P = 0.006), general health (P = 0.029), and physical component summary (P = 0.009). The estimated overall survival and failure free survival rates at 5 years were 88.5% ± 6.3% vs. 82.4% ± 6.5% (P = 0.515), 84.6% ± 7.1% vs. 79.4% ± 6.9%, respectively (P = 0.579). The infection rates were 61.53% and 47.05%, respectively (P = 0.265).

CONCLUSION

As part of the conditioning regimen, p-ALG achieved a similar efficacy as ATG-F without increasing the incidence of transplantation complications in SAA patients.

Bone marrow transplantation for acquired aplastic anemia: What's new

Bone marrow transplantation is a major therapeutic option for patients with acquired severe aplastic anaemia: improved survival has been achieved in younger patients, thanks to better donor selection, conditioning regimens and graft versus host disease prophylaxis, together with improved supportive care, including diagnosis and treatment of opportunistic infections. This has not been the case for older patients over the age of 40 years. We will discuss transplantation platforms as used for different donor types and we will analyse major breakthroughs of the last years: the combination of Fludarabine and cyclophosphamide as a conditioning regimen, the use of alternative donors including HLA haploidentical related donors and new strategies to prevent acute and chronic graft versus host disease, including post transplantation Cyclophosphamide. These changes extend the option of a bone marrow transplantation for patients who lack an HLA matched donor and appear to improve engraftment and reduce graft versus host disease: whether this will be true for all age groups is currently being investigated.

Outcomes of haploidentical bone marrow transplantation in patients with severe aplastic anemia-II that progressed from non-severe acquired aplastic anemia

Severe aplastic anemia II (SAA-II) progresses from non-severe aplastic anemia (NSAA). The unavailability of efficacious treatment has prompted the need for haploidentical bone marrow transplantation (haplo-BMT) in patients lacking a human leukocyte antigen (HLA)-matched donor. This study aimed to investigate the efficacy of haplo-BMT for patients with SAA-II. Twenty-two patients were included and followed up, and FLU/BU/CY/ATG was used as conditioning regimen. Among these patients, 21 were successfully engrafted, 19 of whom survived after haplo-BMT. Four patients experienced grade II-IV aGvHD, including two with grade III-IV aGvHD. Six patients experienced chronic GvHD, among whom four were mild and two were moderate. Twelve patients experienced infections during BMT. One was diagnosed with post-transplant lymphoproliferative disorder and one with probable EBV disease, and both recovered after rituximab infusion. Haplo-BMT achieved 3-year overall survival and disease-free survival rate of 86.4% ± 0.73% after a median follow-up of 42 months, indicating its effectiveness as a salvage therapy. These promising outcomes may support haplo-BMT as an alternative treatment strategy for patients with SAA-II lacking HLA-matched donors.

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.

Allogeneic hematopoietic stem cell transplantation in aplastic anemia: current indications and transplant strategies

Treatment options for newly diagnosed aplastic anemia (AA) patient includes upfront allogeneic hematopoietic stem cell transplant (HSCT) or immunosuppressive therapy (IST). With recent advances in supportive care, conditioning regimens and post-transplant immunosuppression the overall survival for HSCT approaches 70-90%. Transplant eligibility needs to be assessed considering age, comorbidities, donor availability and probability of response to immunosuppressive therapy (IST). Upfront HSCT should be offered to children and young adults with matched related donor (MRD). Upfront HSCT may also be offered to children and young adults with rapidly available matched unrelated donor (MUD) who require urgent HSCT. Bone marrow (BM) graft source and cyclosporine (CsA) plus methotrexate (MTX) as graft versus host disease (GVHD) prophylaxis are preferable when using anti-thymocyte globulin (ATG) based conditioning regimens. Alemtuzumab is an acceptable alternative to ATG and is used with CsA alone and with either BM or peripheral blood stem cells (PBSC). Cyclophosphamide (CY) plus ATG conditioning is preferable for patients receiving MRD transplant, while Fludarabine (Flu) based conditioning is reserved for older adults, those with risk factors of graft failure and those receiving MUD HSCT. For haploidentical transplant, use of low dose radiotherapy and post-transplant cyclophosphamide has resulted in a marked reduction in graft failure and GVHD.

Choice of conditioning regimens for bone marrow transplantation in severe aplastic anemia

Allogeneic bone marrow transplantation (BMT) is curative therapy for the treatment of patients with severe aplastic anemia (SAA). However, several conditioning regimens can be used for BMT. We evaluated transplant conditioning regimens for BMT in SAA after HLA-matched sibling and unrelated donor BMT. For recipients of HLA-matched sibling donor transplantation (n = 955), fludarabine (Flu)/cyclophosphamide (Cy)/antithymocyte globulin (ATG) or Cy/ATG led to the best survival. The 5-year probabilities of survival with Flu/Cy/ATG, Cy/ATG, Cy ± Flu, and busulfan/Cy were 91%, 91%, 80%, and 84%, respectively (P = .001). For recipients of 8/8 and 7/8 HLA allele-matched unrelated donor transplantation (n = 409), there were no differences in survival between regimens. The 5-year probabilities of survival with Cy/ATG/total body irradiation 200 cGy, Flu/Cy/ATG/total body irradiation 200 cGy, Flu/Cy/ATG, and Cy/ATG were 77%, 80%, 75%, and 72%, respectively (P = .61). Rabbit-derived ATG compared with equine-derived ATG was associated with a lower risk of grade II to IV acute graft-versus-host disease (GVHD) (hazard ratio [HR], 0.39; P < .001) but not chronic GVHD. Independent of conditioning regimen, survival was lower in patients aged >30 years after HLA-matched sibling (HR, 2.74; P < .001) or unrelated donor (HR, 1.98; P = .001) transplantation. These data support Flu/Cy/ATG and Cy/ATG as optimal regimens for HLA-matched sibling BMT. Although survival after an unrelated donor BMT did not differ between regimens, use of rabbit-derived ATG may be preferred because of lower risks of acute GVHD.

High Overall and GVHD-Free Survival in Patients with Aplastic Anemia Receiving in vivo T-cell Depletion Transplants and Long-Term Complications

We report a single-center experience of allogeneic hematopoietic stem cell transplant for patients with severe aplastic anemia over 13 years of age. Fifty-eight patients were included, and in vivo T-cell depletion was used in all cases. Fifty-one (88%) received alemtuzumab and 7 (12%) were given rabbit anti-thymocyte globulin. The median follow-up period was 6 years (range: 0-13.5). Data was collected retrospectively and updated in April 2019. The median age was 31 years (range: 18-67). Forty (69%) recipients received grafts from related donors and 18 (31%) received them from unrelated donors. Peripheral blood grafts were infused in 12 (20.7%) patients. Five-year overall survival (OS) was 80.7%. Five-year graft-versus-host disease (GVHD)/rejection-free survival was 56%. Eight (13.8%) patients experienced graft failure. The cumulative incidence of grade II-IV acute GVHD at day 100 was 14% and that of chronic GVHD at 1 year was 7%. The selection of unrelated donors and the use of peripheral blood grafts were not significant risk factors for clinically relevant GVHD or for lower OS. Recipients older than 40 years showed significantly worse OS, as observed from the results of univariate analysis. T-cell depletion in severe aplastic anemia shows low rates of GVHD and high OS, but older patients remain a group with higher risk of mortality. Long-term complications were mainly autoimmune in character.

Rabbit ATG/ATLG in preventing graft-versus-host disease after allogeneic stem cell transplantation: consensus-based recommendations by an international expert panel

This collaborative initiative aimed to provide recommendations on the use of polyclonal antithymocyte globulin (ATG) or anti-T lymphocyte globulin (ATLG) for the prevention of graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (HSCT). A comprehensive review of articles released up to October, 2018 was performed as a source of scientific evidence. Fourteen clinically relevant key questions to the domains indication, administration, and post-transplant management were developed and recommendations were produced using the Delphi technique involving a Panel of 14 experts. ATG/ATLG was strongly recommended as part of myeloablative conditioning regimen prior to matched or mismatched unrelated bone marrow or peripheral blood allogeneic HSCT in malignant diseases to prevent severe acute and chronic GvHD. ATG/ATLG was also recommended prior to HLA-identical sibling peripheral HSCT with good but lesser bulk of evidence. In reduced intensity or nonmyeloablative conditioning regimens, ATG/ATLG was deemed appropriate to reduce the incidence of acute and chronic GvHD, but a higher risk of relapse should be taken into account. Recommendations regarding dose, application, and premedication were also provided as well as post-transplant infectious prophylaxis and vaccination. Overall, these recommendations can be used for a proper and safe application of polyclonal ATG/ATLG to prevent GvHD after allogeneic HSCT.

Anti-thymocyte globulin in haematology: Recent developments

Anti-thymocyte globulin (ATG) is a polyclonal antiserum introduced into clinical medicine more than 30 years ago. It induces a broad non-specific immunosuppression. In haematology, standard indications are severe aplastic anaemia and prophylaxis and treatment of graft-versus-host disease (GVHD) (after allogeneic transplantation). For aplastic anaemia, ATG from horses has been found to be superior to ATG from rabbits. In the situation of allogeneic transplantation, ATG lessens the risk of chronic GVHD but may not improve survival. There is current controversy regarding which patients benefit most from ATG and what the ideal dosage is. It is likely that in the coming years a more specific immunosuppressive will be developed that will minimize GVHD while maintaining the graft-versus-malignancy effect.

Control of graft-versus-host disease with rabbit anti-thymocyte globulin, rituximab, and bortezomib in TCRαβ/CD19-depleted graft transplantation for leukemia in children: a single-center retrospective analysis of two GVHD-prophylaxis regimens

Both acute GVHD and chronic GVHD remain the leading cause of morbidity and death after allogeneic HSCT. We conducted a retrospective analysis comparing two GVHD-prophylaxis regimens: 35 patients received "Regimen 1" (horse ATG, tacrolimus, and methotrexate) and 46 "Regimen 2" (rabbit ATG, rituximab, and peritransplant bortezomib). All 81 patients with a median age of 9 (0.6-23) years with ALL (n = 31) or AML (n = 50) in complete remission received TCRαβ/CD19-depleted transplants between May 2012 and October 2016, from 40 HLA-matched unrelated and 41 haploidentical donors. After a median follow-up of 3.9 years, the CI of acute GVHD II-IV was 15% (95% CI: 7-30) in the "Regimen 2" group and 34% (95% CI: -54) in the "Regimen 1" group, P = .05. "Regimen 2" was also more effective in the prevention of chronic GVHD; the CI at 1 year after HSCT was 7% (95% CI: 2-19) vs 31% (95% CI: 19-51), P = .005. The CI of relapse at 3 years adjusted for the GVHD-prophylaxis regimen groups 31% (95% CI: 19-51) for the "Regimen 1" vs 21% (95% CI: 11-37) for the "Regimen 2", P = .3. The retrospective observation suggests that the use of the rATG, rituximab, and bortezomib was associated with significantly lower rate of GVHD without the loss of anti-leukemic activity.

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

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

Impact of T-cell depletion strategies on outcomes following hematopoietic stem cell transplantation for idiopathic aplastic anemia: A study on behalf of the European blood and marrow transplant severe aplastic anemia working party

We retrospectively analyzed the outcomes of 1837 adults and children with severe aplastic anemia (SAA) who underwent matched sibling donor (MSD) and matched unrelated donor (MUD) hemopoietic stem cell transplantation (HSCT) between 2000 and 2013. Patients were grouped by transplant conditioning containing either anti-thymocyte globulin (ATG) (n = 1283), alemtuzumab (n = 261), or no serotherapy (NS) (n = 293). The risks of chronic GvHD were significantly reduced when ATG or alemtuzumab were compared with NS (P = .021 and .003, respectively). Acute GVHD was significantly reduced in favor of alemtuzumab compared with ATG (P = .012) and NS (P < .001). By multivariate analysis, when compared with ATG, alemtuzumab was associated with a lower risk of developing acute (OR 0.262; 95% CI 0.14-0.47; P < .001) and chronic GVHD (HR 0.58; 95% CI 0.35-0.94; P = .027). OS was significantly better in ATG and alemtuzumab patients compared with NS (P = .010 and .025). Our data shows inclusion of serotherapy in MSD and MUD HSCT for patients with SAA reduces chronic GVHD and provides a survival advantage over patients not receiving serotherapy. Notably, alemtuzumab reduced the risk of acute and chronic GvHD compared with ATG and indicates that alemtuzumab might be the serotherapy of choice for MSD and MUD transplants for SAA.

Infections in patients with aplastic Anemia in Chiang Mai University

Background

Infection is a major complication in aplastic anemia (AA) patients. Primary objectives of this study were to determine the prevalence of infections and to determine types of pathogens associated with infections in patients with AA. Secondary objectives were to evaluate overall survival after infections as well as risk factors of infections in patients with AA.

Methods

The authors retrospectively evaluated the infectious episodes (IEs), type of infections, associated pathogens, and outcomes of infections in patients with AA who were diagnosed and treated at Chiang Mai University between January 2010 and December 2015.

Results

Sixty-seven patients with a median age of 51 years (range, 15–87 years) were enrolled. Forty two patients (62.6%) were severe AA. Median absolute neutrophil count (ANC) was 984 /mm³ (range, 120–5500/mm³). Twenty five patients (37.3%) received antithymocyte globulin plus cyclosporine A, 41 patients (61.1%) received anabolic hormone, and 2 patients (2.9%) underwent allogeneic hematopoietic stem cell transplantation. Overall, 31 IEs were documented in 22 patients (32.8%). The most common microbiologically documented site of infection was bloodstream infection (23.4%) followed by pulmonary infection (14.9%). Culture-negative febrile neutropenia occurred in 12.7%. Common pathogens identified were bacteria (73.9%), mainly gram-negative (52.9%) including Acinetobacter baumannii (23.5%) and Pseudomonas aeruginosa (17.6%). Fungal infections were diagnosed in 21.7% and all were Aspergillus spp. Six patients (9%) died during the study period. All of them died from infection which gram-negative bacteria were most common pathogens (66.7%). Patients with infections had 5-year overall survival of 72% that is significantly less than patients without infection (100%) (p = 0.0002). Only risk factor that correlates with high probability of infection was ANC < 500/mm³. (HR 2.29, 95%CI 1.03–7.72, p = 0.043).

Conclusions

Prevalence of infections in AA patients in Chiang Mai University was 32.8% Bacterial infections especially gram-negative bacteria were the major pathogens. Patients with ANC < 500/mm³ had higher risk of infections. Infection was the most important cause of death in AA.

Alternative donor transplants for severe aplastic anemia

Allogeneic hematopoietic stem-cell transplantation remains the only curative treatment for patients with acquired severe aplastic anemia (SAA). When a matched sibling is not available, one can search for a matched unrelated donor or a cord blood unit (CB) in the international registries or, more recently, for an HLA haploidentical (HAPLO) family member. International guidelines call for a course of antithymocyte globulin (ATG) and cyclosporine before a patient with SAA receives a transplant from a donor other than an HLA identical sibling, but whether this is necessary for patients age <20 years is less clear. Here I will examine the rapid increase in HAPLO transplantations for SAA, showing encouraging early results both in children and young adults. Graft-versus-host disease prophylaxis remains of primary importance in patients with SAA, and in vivo T-cell depletion with either ATG or alemtuzumab offers a significant survival advantage. Finally, I will discuss the strong age effect, which is particularly evident at >40 and 50 years of age for reasons not entirely clear and which should be taken into account when designing a treatment strategy for a given patient.

Eculizumab Bridging before Bone Marrow Transplant for Marrow Failure Disorders Is Safe and Does Not Limit Engraftment

Paroxysmal nocturnal hemoglobinuria (PNH) often develops secondary to other bone marrow failure (BMF) disorders, especially aplastic anemia (AA). Patients with the AA/PNH syndrome may require treatment with both eculizumab to reduce intravascular hemolysis and the risk of thrombosis and allogeneic stem cell transplant for the severe BMF. There has been concern that eculizumab could adversely affect the outcomes for transplant in these patients. This is a retrospective, single-center study of severe AA (SAA)/PNH patients treated with eculizumab immediately before the start of conditioning for transplant. Metrics of engraftment and infectious outcomes are described. Eight patients with SAA/PNH and PNH-related symptoms were treated with eculizumab and then proceeded to transplant. All were successfully transplanted without adverse events related to C5 blockage before conditioning. All were also cured of their both PNH and SAA. Eculizumab is safe and efficacious in patients with PNH clones who require transplant. This is sometimes required to "bridge" patients before bone marrow transplantation and does not appear to adversely impact outcomes even when using HLA matched unrelated or haploidentical donors.

Rabbit antithymocyte globulin dose does not affect response or survival as first-line therapy for acquired aplastic anemia: a multicenter retrospective study

In a prospective randomized study, treatment for aplastic anemia (AA) with rabbit antithymocyte globulin (r-ATG) and cyclosporine showed inferior hematological response and survival in comparison to horse antithymocyte globulin (h-ATG) and cyclosporine. However, h-ATG was discontinued in most Asian, South American, and European countries, where r-ATG became the only ATG formulation available. We retrospectively evaluated consecutive patients with acquired AA who received either rabbit (n = 170) or horse (n = 85) ATG and cyclosporine for first-line treatment from 1992 to 2014 in seven referral centers in Brazil and Argentina. Overall response at 3 months was 17% (95%CI, 11-23%) for r-ATG and 44% (95%CI, 33-55%) for h-ATG (p < 0.001). At 6 months, it was 31% (95%CI, 34-39%) for r-ATG and 59% (95%CI, 48-69%) for h-ATG (p < 0.001). Overall survival at 5 years was 57% (95%CI, 47-65%) for r-ATG and 80% (95%CI, 69-87%) for h-ATG (log-rank = 0.001). Relapse was significantly higher in patients receiving h-ATG (28%; 95%CI, 17-43%) as compared to r-ATG (9.4%; 95%CI, 4-21%; log-rank, p = 0.01). The type of ATG was the only factor associated with both response and survival. The r-ATG dose varied from 1 to 5 mg/kg/day, but it did not correlate with outcomes. In summary, this is the largest multicenter study comparing the two ATG formulations in AA. Our results indicate that the dose of r-ATG does not influence hematologic response or survival in first-line therapy for acquired AA. Considering the toxicity and costs of r-ATG, our findings challenge its aggregate benefit to cyclosporine therapy and further strengthen that h-ATG should remain standard therapy in AA.

Acquired Aplastic Anemia: What Have We Learned and What Is in the Horizon?

Acquired aplastic anemia (aAA) characterized by peripheral pancytopenia and bone marrow aplasia is a rare and serious disorder. Differential diagnosis includes constitutional bone marrow failure syndromes and myelodysplastic disorders. Autoimmune reaction to altered hematopoietic stem cells highlights the underlying mechanism. Matched related donor allogeneic hematopoietic stem cell transplantation is the ideal pediatric treatment; alternative approaches include immunosuppressive therapy and use of eltrombopag. Progression to clonal disorders can occur. Recently, alternative donor hematopoietic stem cell transplantation outcomes have significantly improved. Despite advances, aAA continues to be a challenge for hematologists.

Anti-thymocyte globulin improves survival free from relapse and graft-versus-host disease after allogeneic peripheral blood stem cell transplantation in patients with Philadelphia-negative acute lymphoblastic leukemia: An analysis by the Acute Leukemia Working Party of the EBMT

BACKGROUND

Mobilized peripheral blood stem cells are currently the predominant source of grafts for allogeneic transplantation (allogeneic peripheral blood stem cell transplantation [allo-PBSCT]), although, in comparison with bone marrow, their use is associated with an increased risk of chronic graft-versus-host disease (cGVHD). Attempts to reduce the incidence of cGVHD include the addition of anti-thymocyte globulin (ATG) to the pretransplant conditioning regimen.

METHODS

The goal of this retrospective study was to analyze the effect of ATG on allo-PBSCT outcomes for adults with Philadelphia-negative acute lymphoblastic leukemia (Ph-neg ALL). The primary endpoint was survival free from relapse, grade 3 to 4 acute graft-versus-host disease (aGVHD), and cGVHD (ie, graft-versus-host disease-free/relapse-free survival [GRFS]). Nine-hundred twenty-four patients who underwent unmanipulated allo-PBSCT in their first complete remission between 2007 and 2016 were included. ATG was used in 97 of the 494 transplants from matched sibling donors (20%) and in 307 of the 430 transplants from human leukocyte antigen-matched (8 of 8 loci) unrelated donors (71%).

RESULTS

The use of ATG was an independent factor for an improved chance of GRFS (hazard ratio [HR], 0.70; P = .0009). Furthermore, it was associated with a reduced risk of both grade 2 to 4 (HR, 0.66; P = .005) and grade 3 to 4 aGVHD (HR, 0.58; P = .03). Similarly, its addition reduced the incidence of both total (HR, 0.45; P < 10^-5 ) and extensive cGVHD (HR, 0.30; P < 10^-5 ) as well as nonrelapse mortality (HR, 0.58; P = .01). No significant effect was found with respect to leukemia-free or overall survival. However, an increased risk of relapse was noted for those who received ATG (HR, 1.40; P = .04).

CONCLUSIONS

Patients with Ph-neg ALL treated with allo-PBSCT benefit from the use of ATG in terms of improved GRFS. Its use may, therefore, be considered in this setting. Cancer 2018;124:2523-33. © 2018 American Cancer Society.

Hematopoietic cell transplantation for aplastic anemia

PURPOSE OF REVIEW

Improvements in allogeneic hematopoietic cell transplantation (HCT) with better donor selection, conditioning regimens and graft vs. host disease prophylaxis make it reasonable to move HCT earlier in the algorithm for management of severe aplastic anemia (SAA). Recent progress in transplantation is reviewed whereas issues related to developing countries are also addressed.

RECENT FINDINGS

Multiple research centers are reporting on clonality, mutations and telomere disorders in SAA, which may help to choose the most appropriate therapy upfront. Eltrombopag, in combination with immunosuppressive therapy (IST), has shown remarkable improvement over historical IST, and long-term follow-up is awaited. In younger patients and in experienced centers, matched unrelated-donor (MUD) and related haploidentical transplants (haplo-HCT) are being reported with survival approaching that seen with sibling transplants. Literature from resource-limited countries highlight the need to modify guidelines to make them affordable and cost-effective. Bone marrow remains the graft source of choice; peripheral blood stem cells may be acceptable in special circumstances in resource-constrained countries.

SUMMARY

The potential of novel research findings and new therapeutic trials should be maximized by validation in different centers, countries and patient populations to provide personalized care to patients with aplastic anemia.

Diagnosis and Treatment of Aplastic Anemia

OPINION STATEMENT

Acquired aplastic anemia (AA) is a rare, life-threatening bone marrow failure (BMF) disorder that affects patients of all ages and is caused by lymphocyte destruction of early hematopoietic cells. Diagnosis of AA requires a comprehensive approach with prompt evaluation for inherited and secondary causes of bone marrow aplasia, while providing aggressive supportive care. The choice of frontline therapy is determined by a number of factors including AA severity, age of the patient, donor availability, and access to optimal therapies. For newly diagnosed severe aplastic anemia, bone marrow transplant should be pursued in all pediatric patients and in younger adult patients when a matched sibling donor is available. Frontline therapy in older adult patients and in all patients lacking a matched sibling donor involves immunosuppressive therapy (IST) with horse antithymocyte globulin and cyclosporine A. Recent improvements in upfront therapy include encouraging results with closely matched unrelated donor transplants in younger patients and the emerging benefits of eltrombopag combined with initial IST, with randomized studies underway. In the refractory setting, several therapeutic options exist, with improving outcomes of matched unrelated donor and haploidentical bone marrow transplantation as well as the addition of eltrombopag to the non-transplant AA armamentarium. With the recent appreciation of frequent clonal hematopoiesis in AA patients and with the growing use of next-generation sequencing in the clinic, utmost caution should be exercised in interpreting the significance of somatic mutations in AA. Future longitudinal studies of large numbers of patients are needed to determine the prognostic significance of somatic mutations and to guide optimal surveillance and treatment approaches to prevent long-term clonal complications.

Effect of Antithymocyte Globulin Source on Outcomes of HLA-Matched Sibling Allogeneic Hematopoietic Stem Cell Transplantation for Patients with Severe Aplastic Anemia

We wanted to evaluate efficacy of porcine antithymocyte globulin (ATG) in HLA-matched sibling donor allogeneic hematopoietic stem cell transplantation (MSD-HSCT) for patients with severe aplastic anemia (SAA). The clinical data of 113 SAA patients who received MSD-HSCT from January 2005 to November 2016 were analyzed retrospectively. Of these, 58 patients received rabbit ATG as a part of conditioning regimen (R-ATG group), whereas the other 55 patients received porcine ATG (P-ATG group). Patient baseline characteristics and donor conditions of the 2 groups were similar, except patients were older and more received peripheral blood stem cell transplantation in the P-ATG group. All patients engrafted in 2 groups. There were significant differences in the incidence of acute (20.7% ± 5.3% versus 43.4% ± 7.0%, P = .015) and chronic graft-versus- host disease (GVHD; 20.1% ± 5.8% versus 46.0% ± 7.9%, P = .003) between the R-ATG and P-ATG groups. However, there were no significant differences in terms of 3-year overall survival (93.1% ± 3.3% versus 84.4% ± 5.7%, P = .235), grades III to IV acute GVHD (3.4% ± 2.4% versus 12.3% ± 4.7%, P = .098), moderate to severe chronic GVHD (12.6% ± 4.9% versus 11.5% ± 4.9%, P = .905), or graft rejection (7.4% ± 3.6% versus 5.5% ± 3.1%, P = .852). There was also no significant difference with regard to the incidence of severe bacterial infection (P = .075), invasive fungal disease (P = .701), or cytomeglovirus viremia (P = .770). P-ATG showed satisfactory efficacy and safety compared with R-ATG in the setting of MSD-HSCT for SAA patients. P-ATG could be a potential alternative preparation for R-ATG, further offering the advantage of lower costs.