Alternative Donor Transplantation with High-Dose Post-Transplantation Cyclophosphamide for Refractory Severe Aplastic Anemia

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

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

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

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

Alternative donor transplantation for severe aplastic anemia: a comparative study of the SAAWP EBMT

ABSTRACT

Selecting the most suitable alternative donor becomes challenging in severe aplastic anemia (SAA) when a matched sibling donor (MSD) is unavailable. We compared outcomes in patients with SAA undergoing stem cell transplantation (SCT) from matched unrelated donors (MUD) (n = 1106), mismatched unrelated donors (MMUD) (n = 340), and haploidentical donors (Haplo) (n = 206) registered in the European Society for Blood and Marrow Transplantation database (2012-2021). For Haplo SCT, only those receiving posttransplant cyclophosphamide for graft-versus-host disease (GVHD) prophylaxis were included. Median age was 20 years, and the median time from diagnosis to transplantation 8.7 months. Compared with MUD, MMUD (hazard ratio [HR], 2.93; 95% confidence interval [CI], 1.52-5.6) and Haplo (HR, 5.15; 95% CI, 2.5-10.58) showed significantly higher risks of primary graft failure. MUD had lower rates of acute GVHD compared with MMUD and Haplo (grade 2-4: 13%, 22%, and 19%, respectively; P < .001; grade 3-4: 5%, 9%, and 7%, respectively; P = .028). The 3-year nonrelapse mortality rate was 14% for MUD, 19% for MMUD, and 27% for Haplo (P < .001), whereas overall survival and GVHD and relapse-free survival (GRFS) rates were 81% and 73% for MUD, 74% and 65% for MMUD, and 63% and 54% for Haplo, respectively (P < .001). In addition to donor type, multivariable analysis identified other factors associated with GRFS such as patient age, performance status, and interval between diagnosis and transplantation. For patients with SAA lacking an MSD, our findings support MUDs as the preferable alternative donor option. However, selecting between an MMUD and Haplo donor remains uncertain and requires further exploration.

Recombinant Human Thrombopoietin Promotes Platelet Engraftment in Severe Aplastic Anemia Patients Following Treatment With Haploid Hematopoietic Stem Cell Transplantation using Modified Post-Transplantation Cyclophosphamide

BACKGROUND

Recombinant human TPO (rhTPO) promotes platelet engraftment in patients after allogeneic HSCT (allo-HSCT). However, the effects of rhTPO on platelet recovery after Haplo-HSCT in patients with severe aplastic anemia (SAA) have not been intensively studied.

OBJECTIVE

We aimed to evaluate the efficacy of rhTPO on platelet engraftment in patients with SAA who were treated with Haplo-HSCT using post-transplantation cyclophosphamide (PTCy).

STUDY DESIGN

SAA patients who received Haplo-HSCT plus PTCy regimen were divided into the rhTPO group (with subcutaneous injection of rhTPO, n = 28) and Control group (no rhTPO administration, n = 27). The engraftment of platelet/neutrophil, platelet infusion amount, and transplant-related complications between the 2 groups were compared.

RESULTS

All 55 patients showed successful hematopoietic reconstitution. The median time of platelet engraftment was 11 (9 to 29) days in the rhTPO group and 14 (9 to 28) days in the Control group (P = .003). The rhTPO group had a significantly reduced amount of infused platelets compared to the Control group (2 (1 to 11.5) versus 3 (1 to 14) therapeutic doses; P = .004). There was no significant difference between the 2 groups regarding median time of neutrophil engraftment, incidence of acute graft-versus-host disease (aGVHD) and chronic GVHD (cGVHD), incidence of cytomegalovirus or Epstein-Barr virus reactivation, 3-yr overall survival rate, and failure-free-survival rate. No obvious adverse reactions were observed in the rhTPO group.

CONCLUSION

rhTPO promoted platelet engraftment, reduced the amount of transfused platelets, and demonstrated good safety profiles without evidence of adverse reactions in patients with SAA who received Haplo-HSCT using PTCy regimen.

Upfront Umbilical Cord Blood Transplantation Versus Immunosuppressive Therapy for Pediatric Patients With Idiopathic Severe Aplastic Anemia

Umbilical cord blood transplantation (UCBT) has been rarely reported as a first-line treatment for idiopathic severe aplastic anemia (SAA) patients lacking HLA-matched sibling donors (MSD). Our study aimed to compare the clinical outcomes of pediatric SAA patients who received UCBT and immunosuppressive therapy (IST) upfront. A retrospective analysis was performed on 43 consecutive patients who received frontline IST (n = 17) or UCBT (n = 26) between July 2017 and April 2022. The 3-year overall survival (OS) was comparable between the UCBT and IST groups (96.2% versus 100%, P = .419), while the 3-year event-free survival (EFS) was significantly better in the former than in the latter (88.5% versus 58.8%, P = .048). In the UCBT group, 24 patients achieved successful engraftment, 2 patients developed severe acute graft-versus-host disease (aGVHD), no extensive chronic GVHD (cGVHD), and a high GVHD-free, failure-free survival (GFFS) of 84.6% at 3 years. After 1 year of treatment, 12 patients in the IST group responded, while 5 patients did not achieve remission and 2 patients had disease relapse. At both 3 and 6 months after treatment, the proportion of transfusion-independent patients was higher in the UCBT group than in the IST group. Faster immune recovery and earlier transfusion independence further reduced the risk of infection and bleeding, thereby improving health-related quality of life in the UCBT-treated group. Our results suggested that UCBT as upfront therapy may be an effective and safe option for pediatric SAA patients, with favorable outcomes in experienced centers.

Allogeneic bone marrow transplantation for aplastic anemia

After more than 60 years of intense research in allogeneic hematopoietic cell transplantation (HCT), this therapy has progressed from one that was fraught with seemingly insurmountable complications to a standard treatment of patients with aplastic anemia. During the 1970s and 1980s, HCT donors were almost exclusively HLA-identical siblings. Subsequent advances in the understanding of the complexity of the HLA region along with the development of molecular HLA typing and the establishment of unrelated volunteer donor registries have resulted in an ever-increasing use of such donors. Most recent breakthroughs have enabled HLA-haploidentical HCT and, thereby, finding donors for nearly every patient. The outstanding outcomes reported with any of the donor options have made allogeneic HCT the preferred treatment over immunosuppressive therapy.

Comparison of Haploidentical Stem Cell Transplantation with Post-Transplantation Cyclophosphamide versus Umbilical Cord Blood Transplantation in Adult Patients with Aplastic Anemia

Aplastic anemia patients who are refractory to immunosuppressive therapy or with very low neutrophil counts require allogeneic hematopoietic stem cell transplantation (HSCT). Umbilical cord blood transplantation (UCBT) has been a treatment option when an HLA-matched donor is not available, and HSCT from a related haploidentical donor using post-transplantation cyclophosphamide (PTCy) for graft-versus-host disease (GVHD) prophylaxis (PTCy-haplo) recently became another important approach. We aimed to compare the outcomes of PTCy-haplo and UCBT in adult patients with aplastic anemia to identify more effective and safer approaches for alternative donor transplantation. Data in a nationwide registry were analyzed retrospectively to assess the outcomes of aplastic anemia patients age ≥16 years who underwent PTCy-haplo or UCBT as their first HSCT between 2016 and 2020. The primary endpoint was 1-year overall survival (OS) after HSCT. Secondary endpoints included 1-year failure-free survival (FFS), neutrophil and platelet engraftment, and acute and chronic GVHD. Eighty-three patients who underwent PTCy-haplo (n = 24) or UCBT (n = 59) were eligible. The 1-year OS rate was 78.5% (95% confidence interval [CI], 55.7% to 90.5%) in the PTCy-haplo group and 77.5% (95% CI, 64.5% to 86.3%; P = .895) in the UCBT group. The 1-year FFS rate was 78.7% (95% CI, 56.1% to 90.6%) in the PTCy-haplo group and 62.2% (95% CI, 48.5% to 73.3%; P = .212) in the UCBT group. Among patients age <40 years, the PTCy-haplo group had a significantly higher FFS rate (92.9% [95% CI, 59.1% to 99.0%]) vs 63.9% [95% CI, 43.2% to 78.7%]; P = .047). Neutrophil engraftment and platelet engraftment rates were significantly higher in the PTCy-haplo group compared with the UCBT group: 95.8% (95% CI, 73.9% to 99.4%) vs 78.0% (95% CI, 65.1% to 86.6%, P < .001) and 83.3% (95% CI, 61.5% to 93.4%) vs 72.9% (95% CI, 59.6% to 82.4%; P = .025). No significant difference was observed in the cumulative incidence of grade II-IV acute GVHD and chronic GVHD between the 2 groups. Aplastic anemia patients achieved significantly higher neutrophil and platelet engraftment rates with PTCy-haplo than with UCBT. OS and the incidences of acute and chronic GVHD were similar between the 2 groups. In patients age <40 years, the FFS rate was higher in the PTCy-haplo group. PTCy-haplo is promising for alternative donor transplantation in adult patients with aplastic anemia.

Post-transplantation cyclophosphamide as GVHD prophylaxis in allogenic hematopoietic stem cell transplantation: Recent advances and modification

Allogenic hematopoietic stem cell transplantation (allo-HSCT) is the most important therapeutic option for hematological disorders, although graft-versus-host disease (GVHD) remains the main cause of mortality. Post-transplantation cyclophosphamide (PTCY) induces immune tolerance and is associated with a low incidence of GVHD and non-relapse mortality. Therefore, PTCY has emerged as a safe and effective GVHD prophylaxis in haploidentical transplantation and has been expanded to matched related or unrelated donor and mismatched unrelated donor HSCT. On the basis of current understanding of the mechanisms of PTCY and antithymocyte globulin (ATG) in the prevention of GVHD, growing evidence suggests that the combination of ATG and PTCY could improve allo-HSCT clinical outcomes. Further research will focus on optimizing PTCY regimens by modifying the timing of administration or adding other immunosuppressive agents.

Combining PTCy and ATG for GvHD prophylaxis in non-malignant diseases

Bone marrow transplantation for non-malignant diseases such as aplastic anemia and hemoglobinopathies is a burgeoning clinical area. The goal of these transplants is to correct the hematopoietic defect with as little toxicity as possible. This requires mitigation of transplant-specific toxicities such as graft versus host disease, given this is not needed in non-malignant disorders. This review details current clinical outcomes in the field with a focus on post-transplantation cyclophosphamide and anti-thymoglobulin as intensive graft versus host disease prophylaxis to achieve that goal.

The next horizon now that everyone has a donor: Precision allogeneic transplantation

Post-transplant cyclophosphamide (PTCy) allows safe and effective partially matched donor allogeneic blood or marrow transplantation (alloBMT), so that almost everyone in need of the procedure now has a donor. Moreover, PTCy and other recent advances have lowered alloBMT mortality rates to less than half of that seen before the turn of the century, at costs that are substantially less than most newly approved anticancer agents. These advances also make tailoring BMT based on patients' unique diseases and characteristics now feasible for further improving outcomes. Personalizing every aspect of alloBMT, including conditioning, donor, graft type, and post-transplant maintenance is now possible. For example, alloBMT's antitumor activity historically was restricted to the allogeneic graft-versus-tumor effect directed against histocompatibility antigens. However, replacing exhausted immune systems with healthy non-exhausted, non-tolerant ones likely can enhance the activity of novel targeted therapies. The impressive results seen with tyrosine kinase inhibitors after alloBMT for patients with both Ph+ acute lymphoblastic leukemia and FLT/ITD+ acute myeloid leukemia herald the potential of precision BMT.

Haploidentical Hematopoietic Stem Cell Transplantation in Pediatric Patients with Acquired Hypocellular Bone Marrow Failure

Children with acquired hypocellular bone marrow failure of unknown cause (AHBMF) are usually diagnosed either with severe aplastic anemia (SAA) or refractory cytopenia of childhood (RCC). Patients with AHBMF who lack a matched donor and who failed or relapsed after immunosuppressive therapy (IST) need alternative therapies. Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) offers a curative treatment for these patients. We report a multicenter Spanish experience with haplo-HSCT in pediatric patients with AHBMF. Eleven pediatric patients (SAA, n = 9; RCC, n = 2) underwent haplo-HSCT with different lymphodepletion strategies. Most patients (10 of 11) had previously failed to respond or relapsed after IST. The conditioning regimen was reduced intensity in SAA and myeloablative in RCC. Patients with SAA received low-dose radiotherapy as part of their conditioning regimen. All patients engrafted. Viral reactivation was common (8 of 11). Acute GVHD grade ≥II was seen in 5 patients. Chronic GVHD was diagnosed in 4 of the long-term survivors. Transplantation-associated microangiopathy was a frequent complication in SAA patients and was related to worse outcome. Two patients died of transplantation-related complications. Overall survival was 81%, with a median follow-up of 36 months. Haplo-HSCT can be a successful salvage curative treatment for pediatric patients with AHBMF, but with significant toxicities that must be addressed. Transplantation-associated microangiopathy was the most critical complication.

Low-dose post-transplant cyclophosphamide with G-CSF/ATG based haploidentical protocol provides favorable outcomes for SAA patients

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT), as one of the life-saving treatments for severe aplastic anemia (SAA), is widely used because of its great donor availability. Over decades, granulocyte colony-stimulating factor (G-CSF)/antithymocyte globulin (ATG)-based protocol (the so-called Beijing Protocol) has achieved favorable engraftment and survival outcomes. In this study, we modified the conventional Beijing Protocol: the full-dose Cyclophosphamide (Cy) (200 mg/kg in total) was divided into 42.75 mg/kg Cy on day -5 to day -2 and Low dose post-transplant Cy (PTCy) (14.5 mg/kg on days +3 and +4), hoping to reduce the incidence of severe acute graft-versus-host disease (aGVHD) and to guarantee successful and stable engraftment. Here we retrospectively reported and analyzed the data of first 17 patients with SAA who had received haplo-HSCT using this novel regimen between August 2020 and August 2022. The median follow-up was 522 days (range, 138-859 days). No patient developed primary graft failure. Four (23.5%) patients developed grade II bladder toxicity, two (11.8%) patients developed grade II cardiotoxicity. All patients achieved neutrophil and platelet engraftment at median times of 12 days (range, 11-20 days) and14 days (range, 8-36 days). During our follow-up, no patients developed grade III-IV aGVHD. The cumulative incidence of grade II and grade I aGVHD at 100 days was 23.5% (95% CI, 6.8%-49.9%) and 47.1% (95% CI, 23.0%-72.2%). Three patients (17.6%) developed chronic GVHD of skin, mouth, and eyes and all of which were mild. All patients are alive by the end of the follow-up, with a failure-free survival of 100%, which was defined as survival without treatment failures, such as death, graft failure, or relapse rate. The rate of cytomegalovirus (CMV) reactivation was 82.4% (95% CI, 64.3%-100%). The rate of Epstein-Barr virus (EBV) reactivation was 17.6% (95% CI, 3.8%-43.4%). No CMV disease and post-transplantation lymphoproliferative disorder (PTLD) occurred among these patients. In conclusion, the encouraging results of prolonged survival outcomes and reduced incidence of GVHD suggest promising effect of this novel regimen in haplo-HSCT for patients with SAA. Larger-sample prospective clinical trials are needed to confirm the effectiveness of this regimen.

Prospective study of a modified posttransplant cyclophosphamide regimen for severe aplastic anemia patients with HLA-haploidentical transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative modality for severe aplastic anemia (SAA). The availability of haploidentical donors has expanded valid choices for SAA. However, previous posttransplantation cyclophosphamide (PTCy)-based protocols for HLA-haploidentical HSCT in SAA patients are associated with relatively delayed neutrophil and platelet engraftment. We prospectively studied HLA-haploidentical HSCT using bone marrow combined with peripheral blood stem cells as grafts and a modified PTCy regimen for treating SAA; we evaluated the efficacy and safety of this regimen, which had an increased dose (from 4.5 mg/kg to 6.0 mg/kg) and backward adjusted timing (from day -9 to -7 to day -5 to -3) of antithymocyte globulin (ATG) compared with previous PTCy protocols. Seventy-one eligible patients were included in this prospective study between July 2019 and June 2022. The median time to and cumulative incidence (CI) of neutrophil and platelet engraftment were 13 days (range, 11-19) and 97.2±2.2% and 12 days (range, 7-62) and 94.4 ± 2.9%, respectively. Five patients experienced graft failure (GF), including 2 with primary GF and 3 with secondary GF. The CI of GF was 7.0±3.1%. The interval between diagnosis and transplantation (≥1 year) was a risk factor for GF development (HR 8.40, 95% confidence interval (1.40-50.47), p=0.02). No patients developed grade IV acute graft-versus-host disease (aGVHD) or severe chronic GVHD (cGVHD). The 100-day CI of grade II-IV aGVHD and 2-year cGVHD were 13.4±4.2% and 5.9±2.9%, respectively. With a median follow-up of 580 days (range, 108-1014) for 63 survivors, the estimated 2-year overall survival (OS) and 2-year GVHD-free and failure-free survival (GFFS) were 87.3% (95% confidence interval, 79.4-96.0) and 83.8% (95% confidence interval, 74.9-93.7), respectively. In conclusion, the PTCy regimen with an increased dose and backward adjusted timing of ATG is an effective and feasible choice for treatment with HLA-haploidentical HSCT using BM combined with PBSCs as grafts, with a high rate of and faster engraftment, a low rate and intensity of aGVHD and cGVHD, and prolonged OS and GFFS.

Alternative Transplantation With Post-Transplantation Cyclophosphamide in Aplastic Anemia: A Retrospective Report From the BMF-WG of Hunan Province, China

Although the possibility of first-line hematopoietic cell transplantation (HCT) from alternative donors in severe aplastic anemia (SAA) patients has been suggested recently, transplantation strategies are still being investigated. We established a novel post-transplantation cyclophosphamide-based HCT protocol for patients with SAA in prior studies. We explores the effectiveness and safety of this HCT approach either as first-line or as salvage treatment in SAA patients. Outcomes of 71 consecutive young patients, who received HCT from unrelated or haploidentical donors, were retrospectively analyzed. According to their treatment before transplantation, the patients were classified into treatment-naive (TN) and relapsed or refractory (R/R) patients. The R/R patients were designated as such when a patient did not respond to previous immunosuppressive therapy or relapsed. We administered an antithymocyte globulin (ATG)-free, total body irradiation (TBI)-free conditioning regimen comprising cyclophosphamide, busulfan, and fludarabine, all in an intravenous formula. We used a thorough post-transplantation prophylaxis regimen for GVHD, including post-transplantation cyclophosphamide (PTCy) and short-term methotrexate and long-term cyclosporine A. The median age of the cohort was 16 (95% confidence interval, 12-20) years at transplantation. Most patients (61 of 71) received HCT from haploidentical donors, and the others received HCT from unrelated donors. TN patients (n = 38) were younger and had a shorter time-to-transplant and lower HCT-specific comorbidity index than patients with R/R diseases (n = 33). The frequencies of graft failure, grade II-IV acute graft-versus-host disease (GVHD), and moderate-severe chronic GVHD were similar, at 5.3% versus 6.5% (P = .057), 8.3% versus 0% (P = .109), and 5.7% versus 0% (P = .199) between R/R and TN patients. With a median 42-month follow-up, the frequencies of overall survival (OS) and event-free survival (EFS) were higher in the TN group than in the R/R group (100% versus 84.8% [P = .013] and 86.8% versus 75.8% [P = .255], respectively). All patients who achieved successful engraftment showed full donor chimerism. Four patients, all in the R/R group, suffered from donor-type aplasia; of these, 2 died, 1 was salvaged with another transplantation, and the final one was still receiving transfusion at the last follow-up. Currently, 93.9% (62 of 66) of the patients are alive more than 12 months after transplantation; of these 93.5% (58 of 62) no longer receive immunosuppression, including 91.7% (33 of 34) of the TN group and 89.3% (25 of 28) in the R/R group. This novel TBI-free and ATG-free HCT protocol using a reduced-intensity conditioning regimen followed by modified PTCy achieved promising engraftment, minimal GVHD risk, and encouraging OS and EFS. Our study suggests that unrelated or haploidentical HCT with PTCy can be used as a first-line treatment for young patients with SAA. Nevertheless, further efforts are needed to explore possibilities for older patients and patients with a poor performance status.

Hematopoietic Cell Transplantation for Systemic Sclerosis-A Review

Systemic sclerosis (SSc) is an autoimmune, multi-organ, connective tissue disease associated with significant morbidity and mortality. Conventional immunosuppressive therapies demonstrate limited efficacy. Autologous hematopoietic stem cell transplantation (HCT) is more efficacious but carries associated risks, including treatment-related mortality. Here, we review HCT as a treatment for SSc, its efficacy and toxicity in comparison to conventional therapies, and the proposed mechanisms of action. Furthermore, we discuss the importance of and recent developments in patient selection. Finally, we highlight the knowledge gaps and future work required to further improve patient outcomes.

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.

Haploidentical bone marrow transplantation in patients with relapsed or refractory severe aplastic anaemia in the USA (BMT CTN 1502): a multicentre, single-arm, phase 2 trial

BACKGROUND

Relapsed severe aplastic anaemia is a marrow failure disorder with high morbidity and mortality. It is often treated with bone marrow transplantation at relapse post-immunosuppressive therapy, but under-represented minorities often cannot find a suitably matched donor. This study aimed to understand the 1-year overall survival in patients with relapsed or refractory severe aplastic anaemia after haploidentical bone marrow transplantation.

METHODS

We report the outcomes of BMT CTN 1502, a single-arm, phase 2 clinical trial done at academic bone marrow transplantation centres in the USA. Included patients were children and adults (75 years or younger) with severe aplastic anaemia that was refractory (fulfilment of severe aplastic anaemia disease criteria at least 3 months after initial immunosuppressive therapy) or relapsed (initial improvement of cytopenias after first-line immunosuppressive therapy but then a later return to fulfilment of severe aplastic anaemia disease criteria), adequate performance status (Eastern Cooperative Oncology Group score 0 or 1, Karnofsky or Lansky score ≥60%), and the presence of an eligible related haploidentical donor. The regimen used reduced-intensity conditioning (rabbit anti-thymocyte globulin 4·5 mg/kg in total, cyclophosphamide 14·5 mg/kg daily for 2 days, fludarabine 30 mg/m2 daily for 5 days, total body irradiation 200 cGy in a single fraction), related HLA-haploidentical donors, and post-transplantation cyclophosphamide-based graft-versus-host disease (GVHD) prophylaxis. Additionally, for GVHD prophylaxis, mycophenolate mofetil was given orally at a dose of 15 mg/kg three times a day up to 1 g three times a day (maximum dose 3000 mg per day) from day 5 to day 35, and tacrolimus was given orally or intravenously from day 5 to day 180 as per institutional standards to maintain a serum concentration of 10-15 ng/mL. The primary endpoint was overall survival 1 year after bone marrow transplantation. All patients treated per protocol were analysed. This study is complete and is registered with ClinicalTrials.gov, NCT02918292.

FINDINGS

Between May 1, 2017, and Aug 30, 2020, 32 patients with relapsed or refractory severe aplastic anaemia were enrolled from 14 centres, and 31 underwent bone marrow transplantation. The median age was 24·9 years (IQR 10·4-51·3), and median follow-up was 24·3 months (IQR 12·1-29·2). Of the 31 patients who received a transplant, 19 (61%) were male and 12 (39%) female. 13 (42%) patients were site-reported as non-White, and 19 (61%) were from under-represented racial and ethnic groups; there were four (13%) patients who were Asian, seven (23%) Black, one (3%) Hawaiian/Pacific Islander, and one (3%) more than one race, with seven (23%) patients reporting Hispanic ethnicity. 24 (77%) of 31 patients were alive with engraftment at 1 year, and one (3%) patient alive with autologous recovery. The 1-year overall survival was 81% (95% CI 62-91). The most common grade 3-5 adverse events (seen in seven or more patients) included seven (23%) patients with abnormal liver tests, 15 (48%) patients with cardiovascular changes (including sinus tachycardia, heart failure, pericarditis), ten (32%) patients with gastrointestinal issues, seven (23%) patients with nutritional disorders, and eight (26%) patients with respiratory disorders. Six (19%) deaths, due to disease and unsuccessful bone marrow transplantation, were reported after transplantation.

INTERPRETATION

Haploidentical bone marrow transplantation using this approach results in excellent overall survival with minimal GVHD in patients who have not responded to immunosuppressive therapy, and can expand access to bone marrow transplantation across all populations. In clinical practice, this could now be considered a standard approach for salvage treatment of severe aplastic anaemia. Attention to obtaining high cell doses (>2·5 × 108 nucleated marrow cells per kg of recipient ideal bodyweight) from bone marrow harvests is crucial to the success of this approach.

FUNDING

US National Heart, Lung, and Blood Institute and US National Cancer Institute.

Comparisons Between modified PTCY and G-CSF/ATG Regimens for Haploidentical Transplantation in Patients with Aplastic Anemia

BACKGROUND

Haploidentical transplantation has become an alternative treatment option for aplastic anemia patients without matched sibling donors or matched unrelated donors. Recently, the post-transplantation cyclophosphamide (PTCY) regimen and granulocyte colony-stimulating factor (G-CSF)/antithymocyte globulin (ATG) regimen have become the most common protocols used worldwide.

OBJECTIVE

We designed this retrospective study to compare the outcomes of patients receiving a modified post-transplantation cyclophosphamide (mPTCY) regimen versus the G-CSF/ATG regimen.

STUDY DESIGN

We retrospectively reviewed and analyzed the clinical data of 130 aplastic anemia patients who underwent haplo-HSCT and received the mPTCY regimen (n=55) or G-CSF/ATG regimen (n=75) between Jan 2013 and Jun 2021 across seven transplant centers.

RESULTS

Neutrophil engraftment was successful in all patients within 30 days in the G-CSF/ATG group. The cumulative neutrophil engraftment rate in the mPTCY group was 96.36% (95% CI, 94.57-97.57, P=0.010). The median time of neutrophil engraftment in the G-CSF/ATG group was 10 (7-28) days, which was more rapid than that observed in the mPTCY group (P <0.001). There were no significant differences in the incidence of graft versus host disease (GVHD) between the two groups. The cumulative incidence of II-IV acute GVHD was 18.40% (95% CI, 4.27-40.31) in the mPTCY group and 19.32% (95% CI, 5.86-38.58) in the G-CSF/ATG group, while the cumulative incidence of III-IV acute GVHD was 7.31% (95% CI, 0.09-37.48) in the mPTCY group and 7.57% (95% CI, 0.20-34.19) in the G-CSF/ATG group. Similarly, no significant difference was observed between the two groups in terms of overall survival (OS), failure-free survival (FFS), and GVHD relapse-free survival (GRFS). The 2-year OS, FFS and GRFS rates were 95.91% (95% CI, 84.59-98.96), 92.25% (95% CI, 80.59-97.03) and 86.68% (95% CI, 73.98-93.44), respectively, in the mPTCY group and 86.67% (95% CI, 76.64-92.59), 81.28% (95% CI, 70.45-88.46) and 77.20% (95% CI, 65.89-85.16), respectively, in the G-CSF/ATG group. The transplantation-related mortality (TRM) rate was significantly higher in the G-CSG/ATG group than in the mPTCY group (13.33% in the G-CSG/ATG group versus 1.96% in the mPTCY group, P=0.022). In multivariate analysis, female donors, a higher hematopoietic cell transplantation comorbidity index (HCT-CI) and III-IV aGVHD were associated with worse survival outcomes.

CONCLUSIONS

In conclusion, the mPTCY and G-CSF/ATG regimens led to similar outcomes in AA patients, but quicker engraftment was observed with the ATG/G-CSF regimen, and a lower incidence of TRM was observed with the mPTCY regimen.

KIR in Allogeneic Hematopoietic Stem Cell Transplantation: Need for a Unified Paradigm for Donor Selection

Allogeneic hematopoietic stem cell transplantation (aHSCT) is a lifesaving therapy for hematological malignancies. For years, a fully matched HLA donor was a requisite for the procedure. However, new immunosuppressive strategies have enabled the recruitment of viable alternative donors, particularly haploidentical donors. Over 95% of patients have at least two potential haploidentical donors available to them. To identify the best haploidentical donor, the assessment of new immunogenetic criteria could help. To this end, the clinical benefit of KIR genotyping in aHSCT has been widely studied but remains contentious. This review aims to evaluate the importance of KIR-driven NK cell alloreactivity in the context of aHSCT and explain potential reasons for the discrepancies in the literature. Here, through a non-systematic review, we highlight how the studies in this field and their respective predictive models or scoring strategies could be conceptually opposed, explaining why the role of NK cells remains unclear in aHCST outcomes. We evaluate the limitations of each published prediction model and describe how every scoring strategy to date only partly delivers the requirements for optimally effective NK cells in aHSCT. Finally, we propose approaches toward finding the optimal use of KIR genotyping in aHSCT for a unified criterion for donor selection.

Epstein-Barr virus-related lymphoproliferative disorders in T-cell repleted haploidentical transplantation with post-transplant cyclophosphamide

EBV-associated lymphoproliferative disorders (LPDs) are common in hematopoietic stem cell transplantation (HSCT) with T-cell-depleted grafts, but are extremely rare in HSCT patients with T-cell-replete grafts with post-transplant cyclophosphamide (PTCy). Here we present the cases of two pediatric patients who developed EBV-related LPD after T-cell-replete haplo-HSCT with PTCy. One of these is the first reported case of EBV-positive mucocutaneous ulcer (EBVMCU) developing after PTCy. EBV-related diseases are rare in T-cell-replete haplo-HSCT patients with PTCy. However, in patients with risk factors, it is reasonable to screen for EBV viremia for LPD.

Outcome of Haploidentical Peripheral Blood Allografts Using Post-Transplantation Cyclophosphamide Compared to Matched Sibling and Unrelated Donor Bone Marrow Allografts in Pediatric Patients with Hematologic Malignancies: A Single-Center Analysis

The introduction of post-transplantation cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis has made haploidentical (haplo) hematopoietic stem cell transplantation (HSCT) a common approach in adults, but pediatric experience is limited. Based on the encouraging adult data and with the aim of decreasing the risk of graft failure, our center is increasingly using peripheral blood stem cells (PBSCs) from haplo donors with PTCy. Here we compare outcomes of bone marrow (BM) transplantation with traditional donor choices, including matched sibling donors (MSDs) and 10/10 HLA matched unrelated donors (MUDs), with those of haplo PBSC grafts in pediatric patients with hematologic malignancies. In this retrospective single-center study, the primary endpoint was the comparison of GVHD-free relapse-free survival (GRFS; defined as absence of acute GVHD [aGVHD] grade III-IV, relapse, death, or chronic GVHD [cGVHD] requiring systemic therapy) for the 3 cohorts. Secondary endpoints included overall survival (OS), relapse-free survival (RFS), nonrelapse mortality (NRM), and incidence of aGVHD and cGVHD). A total of 104 consecutive patients underwent first allogeneic (allo)-HSCT for a hematologic malignancy or myelodysplastic syndrome between January 2014 and December 2020 using a haplo family donor (PBSCs; n = 26), an MSD (BM; n = 31), or an MUD (BM; n = 47). Patient demographic and transplantation characteristics were not significantly different across the cohorts, apart from remission status, with the haplo cohort having more patients in third or later complete remission before HSCT (P < .01). The median duration of follow-up for the entire cohort was 573 days. The cumulative incidence of aGVHD (grade II-IV or grade III-IV) was not significantly different among the cohorts; however, the cumulative incidence of cGVHD at 18 months was highest in the MUD cohort (31.7%, versus 10.0% in the MSD cohort and 9.2% in the haplo cohort; P = .02). There were no differences in the 18-month cumulative incidence of relapse or NRM. OS and RFS at 18 months were 80.7% (95% confidence interval [CI], 61.7% to 100%) and 73.8% (95% CI, 55.5% to 98.1%) for the haplo cohort, 83.4% (95% CI, 72.8% to 95.5%) and 70.3% (95% CI, 57.9% to 85.3%) for the MUD cohort, and 80.9% (95% CI, 66.9% to 97.7%) and 66.5% (95% CI, 50.5% to 87.5%) for the MSD cohort, with no statistically significant differences among the cohorts. GRFS at 18 months was 61% (95% CI, 43.3% to 85.9%) for the haplo cohort, 44.6% (95% CI, 31.8% to 62.5%) for the MUD cohort, and 62.1% (95% CI, 45.7% to 84.3%) for the MSD cohort (P = .26). Haploidentical PBSC HSCT with PTCy had comparable outcomes to MSD and MUD BM HSCT and less cGVHD compared with MUD BM HSCT in children. The logistical advantages and lower resource burden of haplo HSCT with PBSCs make it a feasible alternative to MUD HSCT in children with hematologic malignancies. Nonetheless, given that this is a retrospective comparison of transplantation platforms rather than donor types, further prospective studies are warranted. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

A modified conditioning regimen based on low-dose cyclophosphamide and fludarabine for haploidentical hematopoietic stem cell transplant in severe aplastic anemia patients at risk of severe cardiotoxicity

Severe cardiotoxicity is a fatal complication during high-dose cyclophosphamide (Cy)-based conditioning in hematopoietic stem cell transplant (HSCT) for severe aplastic anemia (SAA). This study aimed to evaluate the feasibility and efficacy of a modified conditioning regimen in haploidentical HSCT (haplo-HSCT) for severe-cardiotoxic-risk SAA patients. This BuCy^low Flu conditioning utilized busulfan (Bu, 3.2 mg/kg for 2 days), low-dose Cy (100 mg/kg), fludarabine (150 mg/m² ), and rabbit antithymocyte globulin (rATG, 10 mg/kg). Compared to BuCy conditioning using high-dose Cy of 200 mg/kg, Bu of 3.2 mg/kg for 2 days, and rATG of 10 mg/kg, the incidence of severe cardiotoxicity of BuCy^low Flu conditioning was significantly decreased (2.17% vs 12.80%, p = .032). The engraftment rates (100% for neutrophil and 84.44% for platelet) were favorable. The probabilities of 100-day transplant-related mortality were similar in the BuCy^low Flu and the BuCy group (8.75% vs 10.53%, p = .671). Both 1-year overall survival (88.79% vs 84.66%, p = .357) and 1-year failure-free survival (84.78% vs 81.70%, p = .535) were comparable. The BuCy^low Flu group had higher rates of cytomegalovirus and Epstein-Barr virus reactivation. In conclusion, the BuCy^low Flu provided reduced severe cardiotoxicity, and achieved favorable engraftment and survival. Our results suggest BuCy^low Flu conditioning can be a feasible alternative for haplo-HSCT recipients at risk of severe cardiotoxicity.

Inefficacy of Immunosuppressive Therapy for Severe Aplastic Anemia Progressing From Non-SAA: Improved Outcome After Allogeneic Hematopoietic Stem Cell Transplantation

Background and Aims

This study aimed at comparing the efficacy and safety of severe aplastic anemia (SAA) cases that had met the criteria for SAA at the time of diagnosis (group A) with SAA that had progressed from non-SAA (NSAA) (group B), both undergoing first-line immunosuppressive therapy (IST). Additionally, group B was compared with SAA that had progressed from NSAA and who had been treated by allogeneic hematopoietic stem cell transplantation (allo-HSCT) (group C).

Methods

We retrospectively compared 608 consecutive patients in group A (n = 232), group B (n = 229) and group C (n = 147) between June 2002 and December 2019. Six months after treatment, the rate of overall response and the fraction of patients who had achieved normal blood values, treatment-related mortality (TRM), secondary clonal disease, 5-year overall survival (OS) and failure-free survival (FFS) were indirectly compared between group A and group B, group B and group C.

Results

Six months after treatment, the rate of overall response and the fraction of patients who had achieved normal blood values in group A was higher than in group B (65.24% vs. 40.54%, P < 0.0001; 23.33% vs. 2.25%, P < 0.0001); the same was true for group C (92.50% vs. 2.25%, P < 0.0001). The rate of relapse in group B was higher than in group C (P < 0.0001), but there were no differences in TRM and secondary clonal disease (P > 0.05). There were no differences in estimated 5-year OS between groups A and B (83.8% ± 2.6% vs. 85.8% ± 2.6%, P = 0.837), or between B and C (85.8% ± 2.6% vs. 77.9% ± 3.4%, P = 0.051). The estimated 5-year FFS in groups A and C was higher than for group B (57.1% ± 3.3% vs. 39.7% ± 3.4%, P < 0.001; 76.7% ± 3.5% vs. 39.7% ± 3.4%, P < 0.0001).

Conclusion

These results indicate that IST is less effective in SAA progressing from non-SAA but allo-HSCT can improve outcomes.

Combined haploidentical and cord blood transplantation for refractory severe aplastic anaemia and hypoplastic myelodysplastic syndrome

Umbilical cord blood (UCB) transplantation is a potentially curative treatment for patients with refractory severe aplastic anaemia (SAA), but has historically been associated with delayed engraftment and high graft failure and mortality rates. We conducted a prospective phase 2 trial to assess outcome of an allogeneic transplant regimen that co-infused a single UCB unit with CD34⁺ -selected cells from a haploidentical relative. Among 29 SAA patients [including 10 evolved to myelodysplastic syndrome (MDS)] who underwent the haplo cord transplantation (median age 20 years), 97% had neutrophil recovery (median 10 days), and 93% had platelet recovery (median 32 days). Early myeloid engraftment was from the haplo donor and was gradually replaced by durable engraftment from UCB in most patients. The cumulative incidences of grade II-IV acute and chronic graft-versus-host disease (GVHD) were 21% and 41%, respectively. With a median follow-up of 7·5 years, overall survival was 83% and GVHD/relapse-free survival was 69%. Patient- and transplant-related factors had no impact on engraftment and survival although transplants with haplo-versus-cord killer-cell immunoglobulin-like receptor (KIR) ligand incompatibility had delayed cord engraftment. Our study shows haplo cord transplantation is associated with excellent engraftment and long-term outcome, providing an alternative option for patients with refractory SAA and hypoplastic MDS who lack human leucocyte antigen (HLA)-matched donors.

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

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

Optimizing outcomes for haploidentical hematopoietic stem cell transplantation in severe aplastic anemia with intensive GVHD prophylaxis: a review of current findings

Introduction: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has resulted in increased levels of disease-free survival in severe aplastic anemia (SAA). Haploidentical transplantation (haplo-SCT) was previously not recommended due to unacceptable incidences of graft-versus-host disease (GvHD) and graft failures. With the advent of intensive GvHD prophylaxis strategies, the outcomes obtained with haplo-SCT for SAA have gradually improved.Areas covered: A comprehensive search considered PubMed reported articles before 1 February 2021, presented abstracts, and clinical trials pertaining to haplo-HSCT for SAA. This manuscript covers modern approaches with intensive GvHD prophylaxis in haplo-SCT for SAA. The representative methods consist of granulocyte colony stimulating factor (G-CSF) plus ATG-based and posttransplantation cyclophosphamide (PT-Cy)-based protocols.Expert opinion: Currently, haplo-SCT has become a feasible option for treating SAA. The G-CSF/ATG-based protocol included the largest sample size and reported comparable survival rates with identical siblings. The PT-Cy protocol resulted in a relatively lower incidence of GvHD and seemingly poorer but continuously improved engraftment with augmented conditioning. The optimized outcomes are constantly updated with the modification of the conditioning regimen, donor selection, graft source and GvHD prophylaxis. In the future, we should pay more attention to quality of life in addition to survival, and personalized haplo-SCT may improve outcomes.

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.

Selective T-cell depletion targeting CD45RA as a novel approach for HLA-mismatched hematopoietic stem cell transplantation in pediatric nonmalignant hematological diseases

Severe aplastic anemia and congenital amegakaryocytic thrombocytopenia are rare bone marrow failure syndromes. Treatment for aplastic anemia consists of hematopoietic stem cell transplantation (HSCT) from a matched sibling donor or immunosuppressant drugs if there is no donor available. Congenital amegakaryocytic thrombocytopenia is a rare autosomal recessive disease that causes bone marrow failure and has limited treatment options, except for transfusion support and HSCT. In the absence of a suitable matched sibling donor, matched-unrelated, haploidentical, or mismatched donors may be considered. A 2-step partial T-cell-depletion strategy can remove CD45RA+ naïve T cells responsible for graft-versus-host disease (GvHD) while preserving memory T cells. Five patients underwent transplantation using this strategy with rapid neutrophil and platelet recovery. Acute and chronic GvHD ≥ grade 2 appeared in two and one patient, respectively. No severe infections were observed before day + 100. A high (60%) incidence of transplant-associated microangiopathy was observed. Three patients (60%) remain alive, with a median follow-up of 881 (range 323-1248) days. CD45RA-depleted HSCT is a novel approach for patients lacking a suitable matched donor; however, further improvements are needed.

Efficacy of Allogeneic Hematopoietic Cell Transplantation for Autoimmune Diseases

Allogeneic hematopoietic cell transplantation (HCT) may be efficacious for autoimmune diseases (AIDs), but its efficacy for individual AIDs is unknown. Factors influencing the likelihood of relapse for each AID are also unknown. This study aimed to determine the likelihood of relapse for each common AID and to generate hypotheses about factors influencing the likelihood of relapse. We reviewed charts of adult patients with nonhematologic AIDs who had undergone HCT in Alberta (n = 21) and patients described in the literature (n = 67). We used stringent inclusion criteria to minimize the inclusion of patients whose AID may have been cured before transplantation. We also used stringent definitions of AID relapse and remission. AID relapsed in 2 of 9 patients (22%) with lupus, in 4 of 12 (33%) with rheumatoid arthritis (RA), in 0 of 4 (0%) with systemic sclerosis (SSc), in 3 of 16 (19%) with psoriasis, in 1 of 12 (8%) with Behçet's disease (BD), in 1 of 15 (7%) with Crohn's disease (CD), in 0 of 5 (0%) with ulcerative colitis (UC), in 4 of 8 (50%) with multiple sclerosis (MS), and in 3 of 3 (100%) with type 1 diabetes mellitus (T1DM). Among highly informative patients (followed for >1 year after discontinuation of immunosuppressive therapy if no relapse, or donor AID status known if relapse), relapse occurred in 0 of 3 patients with lupus, in 2 of 7 with RA, in 0 of 2 with SSc, in 3 of 6 with psoriasis, in 0 of 3 with BD, in 0 of 10 with CD, in 0 of 3 with UC, in 2 of 3 with MS, and in 2 of 2 with T1DM. There appeared to be no associations between AID relapse and low intensity of pretransplantation chemoradiotherapy, multiple lines of AID therapy (surrogate for AID refractoriness) except perhaps for lupus, absence of serotherapy for graft-versus-host disease (GVHD) prophylaxis, lack of GVHD except perhaps for lupus, or incomplete donor chimerism. Even though remission commonly occurs after HCT in lupus, RA, SSc, psoriasis, BD, CD, and UC, HCT is efficacious for only a subset of patients. The efficacy appears to be unrelated to pretransplantation therapy, GVHD, or chimerism. Large studies are needed to determine the characteristics of patients likely to benefit from HCT for each AID.

Mesenchymal stromal cells as prophylaxis for graft-versus-host disease in haplo-identical hematopoietic stem cell transplantation recipients with severe aplastic anemia?-a systematic review and meta-analysis

BACKGROUND

Mesenchymal stromal cells (MSCs) are an emerging prophylaxis option for graft-versus-host disease (GVHD) in haplo-identical hematopoietic stem cell transplantation (haplo-HSCT) recipients with severe aplastic anemia (SAA), but studies have reported inconsistent results. This systematic review and meta-analysis evaluates the efficacy of MSCs as prophylaxis for GVHD in SAA patients with haplo-HSCT.

METHODS

Studies were retrieved from PubMed, EMBASE, Cochrane, Web of Science, and http://clinicaltrials.gov from establishment to February 2020. Twenty-nine single-arm studies (n = 1456) were included, in which eight (n = 241) studies combined with MSCs and eleven (n = 1215) reports without MSCs in haplo-HSCT for SAA patients. The primary outcomes were the incidences of GVHD. Other outcomes included 2-year overall survival (OS) and the incidence of cytomegalovirus (CMV) infection. Odds ratios (ORs) were calculated to compare the results pooled through random or fixed effects models.

RESULTS

Between MSCs and no MSCs groups, no significant differences were found in the pooled incidences of acute GVHD (56.0%, 95% CI 48.6-63.5% vs. 47.2%, 95% CI 29.0-65.4%; OR 1.43, 95% CI 0.91-2.25; p = 0.123), grade II-IV acute GVHD (29.8%, 95% CI 24.1-35.5% vs. 30.6%, 95% CI 26.6-34.6%; OR 0.97, 95% CI 0.70-1.32; p = 0.889), and chronic GVHD (25.4%, 95% CI 19.8-31.0% vs. 30.0%, 95% CI 23.3-36.6%; OR 0.79, 95% CI 0.56-1.11; p = 0.187). Furtherly, there was no obvious difference in 2-year OS (OR 0.98, 95% CI 0.60-1.61; p = 1.000) and incidence of CMV infection (OR 0.61, 95% CI 0.40-1.92; p = 0.018).

CONCLUSIONS

Our meta-analysis indicates that the prophylactic use of MSC co-transplantation is not an effective option for SAA patients undergoing haplo-HSCT. Hence, the general co-transplantation of MSCs for SAA haplo-HSCT recipients may lack evidence-based practice.

Haploidentical Transplantation with Modified Post-transplantation Cyclophosphamide for Patients with Primary Aplastic Anemia: A Multicenter Experience

Aplastic anemia (AA) is a life-threatening hematological disorder that can be cured by hematopoietic stem cell transplantation. Haploidentical transplantation becomes an alternative choice for patients in the absence of a matched sibling donor. We used a retrospective study aimed to confirm the feasibility of busulfan-based modified post-transplantation cyclophosphamide (PTCY) strategy in haploidentical hematopoietic stem cell transplantation for AA patients. We analyzed the outcomes of 27 patients from 3 clinical centers who had undergone haploidentical transplantation between October 2018 and July 2020. The modified condition regimen consisted of anti-thymoglobulin/antilymphocyte globulin, fludarabine, busulfan and low-dose cyclophosphamide, and high-dose cyclophosphamide, mycophenolate mofetil (MMF) and tacrolimus were administered as graft versus host disease (GVHD) prophylaxis after transplantation. The median follow-up time was 370 (range 65-721) days. One patient developed primary graft failure, and successful engraftment was observed in 96.29% (95% confidence interval [CI], 93.45%-97.91%) of patients. The median times for neutrophil and platelet engraftment were 13 (range 11-18) days and 13 (range 11-28) days, respectively. The most common regimen-related toxicity was bladder toxicity, followed by stomatitis and gastrointestinal toxicity. The cumulative incidence of grade II-IV aGVHD was 25.93% (95% CI, 5.84%-52.64%), whereas the cumulative incidence of grade III-IV aGVHD was 7.4% (95% CI, 0%-52.16%). Chronic GVHD was observed in 3 patients by the end of follow-up. All 27 patients are alive, with a failure-free survival rate of 96.30% (95% CI, 6.49%-99.47%) and GVHD relapse-free survival rate of 88.89% (95% CI, 69.39%-96.28%). Virus reactivation was comparable, with rates of 53.54% for cytomegalovirus (CMV) reactivation and 41.57% for Epstein-Barr virus, but the CMV diseases and post-transplantation lymphoproliferative disorder were rare. Our study using haploidentical transplantation with modified PTCY demonstrated an encouraging result with prolonged survival and reduced complications for aplastic anemia patients.

Haploidentical stem cell transplantation for aplastic anemia: the current advances and future challenges

Haematopoietic stem cell transplantation (HSCT) is a curative option for severe aplastic anemia (SAA). Finding a suitable matched donor in a timely manner is a challenge. The availability of haploidentical donors and their successful use in transplantation have expanded valid choices for SAA. In recent decades, haploidentical HSCT (haplo-HSCT) for the treatment of SAA has been continuously attempted, and great strides have been made. Nowadays, haplo-HSCT using different regimens has overcome the difficulty of graft failure and severe graft-versus-host disease (GvHD), and achieved inspiring survival outcomes in SAA. The regimens consist mainly of granulocyte colony-stimulating factor (G-CSF) plus antithymocyte globulin (ATG), posttransplantation cyclophosphamide (PT-Cy), and ex vivo graft T-cell depletion (TCD). In particular, the G-CSF and ATG-based regimen includes the largest sample size and the successful wide use of the G-CSF and ATG-based regimen has promoted haplo-HSCT a higher priority in SAA patients without matched related or unrelated donors in China. Recent studies have also indicated that haplo-HSCT using PT-Cy or TCD regimen is a practicable alternative, but the sample size is relatively small. Here, we offer an overview of clinical results obtained through the use of haploidentical transplantation in SAA, mainly focusing on current advances and future challenges.

Reduced Intensity Bone Marrow Transplantation with Post-Transplant Cyclophosphamide for Pediatric Inherited Immune Deficiencies and Bone Marrow Failure Syndromes

PURPOSE

Allogeneic bone marrow transplantation (alloBMT) is the only cure for many primary immune deficiency disorders (PIDD), primary immune regulatory disorders (PIRD), and inherited bone marrow failure syndromes (IBMFS).

METHODS

We report the results of 25 patients who underwent alloBMT using reduced intensity conditioning (RIC), alternative donors, and post-transplantation cyclophosphamide (PTCy). In an attempt to reduce regimen-related toxicities, we removed low-dose TBI from the prep and added mycophenolate mofetil and tacrolimus for graft-versus-host disease (GVHD) prophylaxis for all donor types in the latter 14 patients. Donors were haploidentical related (n = 14), matched unrelated (n = 9), or mismatched unrelated (n = 2). The median age was 9 years (range 5 months-21 years).

RESULTS

With a median follow-up of 26 months (range 7 months-9 years), the 2-year overall survival is 92%. There were two deaths, one from infection, and one from complications after a second myeloablative BMT. Three patients developed secondary graft failure, one at 2 years and two at >3 years, successfully treated with CD34 cell boost in one or second BMT in two. The remaining 20 patients have full or stable mixed donor chimerism and are disease-free. The incidence of mixed chimerism is increased since removing TBI from the prep. The 6-month cumulative incidence of grade II acute GVHD is 17%, with no grade III-IV. The 1-year cumulative incidence of chronic GVHD is 14%, with severe of 5%.

CONCLUSION

This alloBMT platform using alternative donors, RIC, and PTCy is associated with excellent rates of engraftment and low rates of GVHD and non-relapse mortality, and offers a curative option for patients with PIDD, PIRD, and IBMFS.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04232085.

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.

Evolution of the role of haploidentical stem cell transplantation: past, present, and future

INTRODUCTION

The accessibility to haplo-donors has led to an increase in the number of haplo-HSCT worldwide. A systematic search of the PubMed database between 2000 to present was performed.

AREAS COVERED

In this review, the authors discussed the most used approaches to perform haplo-HSCT and its results: T-cell depletion (TCD, including Perugia platform and its modifications) and T-cell repleted haplo (TCR, including the high-dose post-transplant cyclophosphamide strategy (Baltimore protocol) and the Beijing protocol). The improvements and modifications made to the different strategies have increased the indications of haplo-HSCT, including both malignant and nonmalignant disorders. Focusing on the Baltimore protocol, the authors review the results of the retrospective studies that have compared it to other donor transplants. The limitations of this strategy in terms of toxicity, graft complications, and GVHD are also discussed in detail. Finally, possible approaches to improve the outcomes of TCR haplo-HSCT are presented.

EXPERT OPINION

The recent advances in the field of haplo-HSCT have allowed a large number of patients with incurable diseases to benefit from this procedure despite not having a matched donor. With all available strategies, virtually no patient who needs an allogeneic transplant should be excluded by the absence of a donor.

Successful Use of Hematopoietic Stem Cell Transplantation for 2 Pediatric Cases of Glanzmann Thrombasthenia and Review of the Literature

Glanzmann thrombasthenia is a rare platelet disorder characterized by an abnormal integrin receptor on the surface of platelets that results in the failure of platelets to aggregate. Currently, curative therapy is allogeneic hematopoietic stem cell transplantation (HSCT). The authors report 2 patients with Glanzmann thrombasthenia who successfully underwent allogeneic HSCT from unrelated donors, including one using umbilical cord blood stem cells. Although both patients had evidence of engraftment, hematopoietic recovery, and normalization of platelet aggregation, they also experienced several post-transplant complications. Allogeneic HSCT carries a significant risk of morbidity and mortality that should be considered before proceeding with the transplant.

Comparison of efficacy and health-related quality of life of first-line haploidentical hematopoietic stem cell transplantation with unrelated cord blood infusion and first-line immunosuppressive therapy for acquired severe aplastic anemia

We retrospectively compared the efficacy and health-related quality of life (HRQoL) of (1) first-line haploidentical hematopoietic stem cell transplantation (haplo-HSCT, n = 146) combined with unrelated cord blood (UCB) infusion and (2) first-line immunosuppressive therapy (IST, n = 219) in acquired severe aplastic anemia (SAA) patients. At 6 months post treatment, 90.30% patients in the haplo-HSCT group and 18.78% patients in the IST group achieved normal blood routine (P < 0.0001). The time required to discontinue red blood cells and platelets transfusion in the IST group were longer than in the haplo-HSCT group (P < 0.0001). The estimated overall survival at 4 years was similar (80.1 ± 3.5% vs. 80.1 ± 3.0%, P = 0.726); the estimated failure-free survival (FFS) at 4 years was 77.8 ± 3.7% in the haplo-HSCT group and 48.0 ± 3.6% in the IST group (P < 0.0001). Patients treated with haplo-HSCT scored significantly better in the HRQoL than treated with IST (P < 0.0001). In the multivariate analysis, first-line haplo-HSCT was the favorable factor for FFS and HRQoL (P < 0.0001). These results suggest that first-line haplo-HSCT combined with UCB infusion might provide a better chance of success and HRQoL than first-line IST for SAA patients.

Excellent outcomes following hematopoietic cell transplantation for Wiskott-Aldrich syndrome: a PIDTC report

Wiskott-Aldrich syndrome (WAS) is an X-linked disease caused by mutations in the WAS gene, leading to thrombocytopenia, eczema, recurrent infections, autoimmune disease, and malignancy. Hematopoietic cell transplantation (HCT) is the primary curative approach, with the goal of correcting the underlying immunodeficiency and thrombocytopenia. HCT outcomes have improved over time, particularly for patients with HLA-matched sibling and unrelated donors. We report the outcomes of 129 patients with WAS who underwent HCT at 29 Primary Immune Deficiency Treatment Consortium centers from 2005 through 2015. Median age at HCT was 1.2 years. Most patients (65%) received myeloablative busulfan-based conditioning. With a median follow-up of 4.5 years, the 5-year overall survival (OS) was 91%. Superior 5-year OS was observed in patients <5 vs ≥5 years of age at the time of HCT (94% vs 66%; overall P = .0008). OS was excellent regardless of donor type, even in cord blood recipients (90%). Conditioning intensity did not affect OS, but was associated with donor T-cell and myeloid engraftment after HCT. Specifically, patients who received fludarabine/melphalan-based reduced-intensity regimens were more likely to have donor myeloid chimerism <50% early after HCT. In addition, higher platelet counts were observed among recipients who achieved full (>95%) vs low-level (5%-49%) donor myeloid engraftment. In summary, HCT outcomes for WAS have improved since 2005, compared with prior reports. HCT at a younger age continues to be associated with superior outcomes supporting the recommendation for early HCT. High-level donor myeloid engraftment is important for platelet reconstitution after either myeloablative or busulfan-containing reduced intensity conditioning. (This trial was registered at www.clinicaltrials.gov as #NCT02064933.).

Hematopoietic Stem Cell Transplantation, Where Have We Come and Where Do We Go

Hematopoietic cellular transplantation (HCT) has impacted medicine beyond simply treating certain diseases. Allogeneic HCT was the first documented successful immunological cellular therapy. Its usage continues to increase. The immunological disparity between donor and recipient has been associated with better antitumor efficacy as well as immunological toxicities. Through active clinical trials and research, considerable improvements in HCT therapy have been made over the past 50 years. The HCT international outcomes registry has considerably contributed to these improvements by identifying factors that could never be studied by a single center. With the use of unrelated donors, international collaboration increased as donor cell access through registries was not inhibited by international boundaries. HCT as a field pioneered the development of organizations for self-regulation that were assessing the entire program as an integrated whole rather than simply assessing facilities and providers separately.

Haploidentical hematopoietic stem cell transplantation in aplastic anemia: a systematic review and meta-analysis of clinical outcome on behalf of the severe aplastic anemia working party of the European group for blood and marrow transplantation (SAAWP of EBMT)

Aplastic anemia (AA) is a serious hematological disorder, which is solely cured by hematopoietic stem cell transplantation (HSCT). Haploidentical HSCT is an emerging modality with encouraging outcomes in several blood conditions. The present study aims to comprehensively assess the feasibility and safety of haploidentical HSCT in patients with severe and very severe AA. It is a systematic review and meta-analysis of studies related to haploidentical stem cell transplantation in idiopathic AA investigating rates of successful engraftment, acute graft-versus-host disease (aGvHD), chronic GvHD (cGvHD), transplant-related mortality (TRM), and posttransplantation viral infections (including cytomegalovirus [CMV]) in patients with AA. The effects of reduced-intensity conditioning (RIC) and nonmyeloablative conditioning (NMA), as well as various GvHD prophylaxis regimens on these outcomes were evaluated. In total 15 studies were identified, (577 patients, 58.9% males), successful engraftment was observed in 97.3% of patients (95% CI, 95.9-98.7) while grades II-IV aGvHD and cGvHD were reported in 26.6% and 25.0%, respectively. The pooled incidence of TRM was 6.7% per year (95% CI, 4.0-9.4). RIC regimens were associated with higher proportions of successful engraftment (97.7% vs 91.7%, P = 0.03) and aGvHD (29.5% vs 18.7%, P = 0.008) when compared with NMA regimens with no differences in cGvHD or mortality incidence. When compared with methotrexate-containing regimens and other regimens, posttransplant cyclophosphamide-containing regimens reduced the rates of aGvHD (28.6%, 27.8%, and 12.8%, respectively, P = 0.02), CMV viremia (55.7%, 38.6%, and 10.4%, respectively, P < 0.001), and CMV disease in initially viremic patients (2.1%, 33.0%, and 0%, respectively, P < 0.001). We have concluded that Haploidentical HSCT was associated with promising outcomes in terms of successful engraftment and reduced complications. Future prospective trials are needed to identify the preferred conditioning regimen, GvHD prophylaxis, and graft source in the setting of haploidentical transplant for AA.

HLA-Haploidentical Hematopoietic Cell Transplantation for Treatment of Nonmalignant Diseases Using Nonmyeloablative Conditioning and Post-Transplant Cyclophosphamide

Allogeneic hematopoietic cell transplant (HCT) is often the only curative therapy for patients with nonmalignant diseases; however, many patients do not have an HLA-matched donor. Historically, poor survival has been seen after HLA-haploidentical HCT because of poor immune reconstitution, increased infections, graft-versus-host disease (GVHD), and graft failure. Encouraging results have been reported using a nonmyeloablative T cell-replete HLA-haploidentical transplant approach in patients with hematologic malignancies. Here we report the outcomes of 23 patients with various nonmalignant diseases using a similar approach. Patients received HLA-haploidentical bone marrow (n = 17) or granulocyte colony-stimulating factor-mobilized peripheral blood stem cell (n = 6) grafts after conditioning with cyclophosphamide 50 mg/kg, fludarabine 150 mg/m², and 2 or 4 Gy total body irradiation. Postgrafting immunosuppression consisted of cyclophosphamide, mycophenolate mofetil, tacrolimus, ± sirolimus. Median patient age at HCT was 10.8 years. Day 100 transplant-related mortality (TRM) was 0%. Two patients died at later time points, 1 from intracranial hemorrhage/disseminated fungal infection in the setting of graft failure and 1 from infection/GVHD. The estimated probabilities of grades II to IV and III to IV acute GVHD at day 100 and 2-year National Institutes of Health consensus chronic GVHD were 78%, 26%, and 42%, respectively. With a median follow-up of 2.5 years, the 2-year overall and event-free rates of survival were 91% and 78%, respectively. These results are encouraging and demonstrate favorable disease-specific lineage engraftment with low TRM in patients with nonmalignant diseases using nonmyeloablative conditioning followed by T cell-replete HLA-haploidentical grafts. However, additional strategies are needed for GVHD prevention to make this a viable treatment approach for patients with nonmalignant diseases.

Combination of haploidentical haematopoietic stem cell transplantation with an unrelated cord-blood unit in patients with severe aplastic anemia: a report of 146 cases

We analyzed the outcomes of 146 severe aplastic anemia (SAA) patients who received a combination of haploidentical haematopoietic stem cell transplantation (haplo-HSCT) and an unrelated cord-blood (UCB) unit between September 2011 and December 2017. One hundred and seventeen patients underwent transplantation as first-line therapy. Seven patients experienced early mortality, and among the evaluable 139 patients, one patient experienced primary graft failure (GF), while the other 138 patients achieved successful haploidentical donor engraftment; additionally, three patients experienced secondary GF. Six patients demonstrated delayed platelet recovery, and three patients demonstrated platelet GF. The median time for myeloid and platelet engraftment was 11 (range: 9-28) days and 15 (range: 9-330) days, respectively. With a median follow-up of 40 (range: 18-93) months, the cumulative incidences were 31.43% and 10.00% for grades II-IV and grades III-IV acute graft-versus-host disease (GVHD), respectively. The cumulative incidences of chronic GVHD (cGVHD) and moderate-severe cGVHD were 36.23% and 11.71%, respectively. There was no patient relapse. The probabilities of 4-year overall survival and GVHD-free, failure-free survival were 81.4 ± 3.3% and 69.2 ± 3.9%, respectively. These encouraging preliminary results indicated that haplo-HSCT combined with the infusion of UCB is a feasible choice for SAA patients without matched donors.

Allo-HSCT compared with immunosuppressive therapy for acquired aplastic anemia: a system review and meta-analysis

Background

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) and immunosuppressive therapy (IST) are two major competing treatment strategies for acquired aplastic anemia (AA). Whether allo-HSCT is superior to IST as a front-line treatment for patients with AA has been a subject of debate. To compare the efficacy and safety of allo-HSCT with that of IST as a front-line treatment for patients with AA, we performed a meta-analysis of available studies that examined the impact of the two major competing treatment strategies for AA.

Results

Fifteen studies including a total of 5336 patients were included in the meta-analysis. The pooled hazard ratio (HR) for overall survival (OS) was 0.4 (95% CI 0.074–0.733, P = 0.016, I² = 58.8%) and the pooled HR for failure-free survival (FFS) was 1.962 (95% CI 1.43–2.493, P = 0.000, I² = 0%). The pooled relative risk (RR) for overall response rate (ORR) was 1.691 (95% CI 1.433–1.996, P = 0.000, I² = 11.6%).

Conclusion

Although survival was significantly longer among AA patients undergoing first-line allo-HSCT compared to those undergoing first-line IST, the selection of initial treatment for patients with newly diagnosed AA still requires comprehensive evaluation of donor availability, patient age, expected quality of life, risk of disease relapse or clonal evolution after IST, and potential use of adjunctive eltrombopag.