Donor-Specific Anti-HLA Antibodies in Haploidentical Stem Cell Transplantation with Post-Transplantation Cyclophosphamide: Risk of Graft Failure, Poor Graft Function, and Impact on Outcomes

Graft failure after allogeneic hematopoietic stem cell transplantation in pediatric patients with acute leukemia: autologous reconstitution or second transplant?

BACKGROUND

Graft failure (GF) is a rare but serious complication after allogeneic hematopoietic stem cell transplantation (HSCT). Prevention of graft failure remains the most advisable approach as there is no clear recommendation for the best strategies for reversing this complication. Administration of growth factor, additional hematopoietic progenitor boost, or a salvage HSCT are current modalities recommended for the treatment of GF. Autologous recovery without evidence of disease relapse occurs rarely in patients with GF, and in the absence of autologous recovery, further salvage transplantation following a second conditioning regimen is a potential treatment option that offers the best chances of long-term disease-free survival. The preconditioning regimens of second HSCT have a significant impact on engraftment and outcome, however, currently there is no consensus on optimal conditioning regimen for second HSCT in patients who have developed GF. Furthermore, a second transplant from a different donor or the same donor is still a matter of debate.

OBSERVATIONS

We present our experience in managing pediatric patients with acute leukemia who encountered graft failure following stem cell transplantation.

CONCLUSIONS AND RELEVANCE

Although a second transplantation is almost the only salvage method, we illustrate that some pediatric patients with acute leukemia who experience graft failure after an allogeneic stem cell transplant using Myeloablative conditioning (MAC) regimen may achieve long-term disease-free survival through autologous hematopoiesis recovery.

Effect of serum panel reactive antibodies on allogeneic hematopoietic stem cell transplantation in pediatric thalassemia patients: A single-center experience

BACKGROUND

The aim of this study was to assess the impact of serum panel reactive antibodies (PRA) on the outcomes of allogeneic hematopoietic stem cell transplantation (HSCT) in pediatric thalassemia patients.

METHODS

A total of 73 pediatric patients with thalassemia were included in this single-center study. Pre-transplant PRA levels were evaluated, and the patients were divided into two groups: PRA-negative (group 1; n = 44) and PRA-positive (group 2; n = 29). Patient characteristics, including age, gender, donor type, stem cell source, and HLA compatibility, were analyzed. Transplant outcomes, including engraftment, transfusion requirements, and transplant-related complications, were compared between the two groups. Further subgroup analysis was performed based on MFI values.

RESULTS

At the time of transplantation, patients in group 1 were younger than those in group 2 (p = .008). The number of fully matched donors within the family (MSD and MFD) was significantly higher in group 1 (p = .049). Additionally, Rh blood group incompatibility was higher in group 2 (p = .03). There was no statistically significant difference in the engraftment days of neutrophils, platelets, and erythrocytes between the two groups. The frequency of poor graft function and graft failure was higher in the group 2, but there was no statistically significant difference. Post-transplant transfusion requirements for platelets and red blood cells were significantly higher in the group 2 (p < .001). Transplant-related complications such as VOD, PRES, and aGvHD were more common in the group 2, but no statistical significance was detected.

CONCLUSIONS

Serum PRA in pediatric thalassemia patients may impact the outcomes of HSCT. PRA-positive patients had higher rates of blood product transfusion requirements. Although poor graft function, graft failure, and post-transplant complications were more common in the group 2, statistical significance was not observed. Identifying patients with high PRA levels can assist in optimizing transplant strategies and post-transplant care, leading to improved outcomes for the patients.

The impact of pre-transplant anti-HLA antibodies in transplants from HLA-identical sibling donors: A multicenter study

Few studies have performed comparative analysis of the outcome of hematopoietic stem cell transplantation from HLA-identical sibling donors (ISD-HSCT) in patients with or without anti-HLA Abs. In this study we retrospectively collected data from a multicenter study to analyze the distribution and impact of the pre-existing anti-HLA Abs in ISD-HSCT. Among 402 recipients, 111 were positive for anti-HLA Abs. Gender, time from diagnosis to transplantation and distribution of primary disease might be risk factors for the occurrence of anti-HLA Abs. We found that patients with anti-HLA Abs had delayed neutrophil engraftment and were more vulnerable to experience Cytomegalovirus (CMV) reactivation. The presence of anti-HLA Abs was proved to be an independent risk factor for neutrophil engraftment (HR 1.42 95% CI 1.13-1.80, p = 0.003) and CMV reactivation (HR 2.03 95% CI 1.19-3.46, p = 0.009). We found that anti-HLA Abs have a negative impact on the prognosis in the early period after transplantation from sibling donors and anti-HLA Abs was also an independent risk factor for the overall survival (OS) at 180 days (HR 2.32, 95% CI 1.03-5.27, p = 0.042) among female recipients. In conclusion, anti-HLA Abs have a negative impact on the prognosis early after ISD-HSCT.

Umbilical Cord Blood Transplantation for Myelodysplastic Syndromes with Donor-Specific Anti-HLA Antibodies against HLA-DP

The presence of donor-specific anti-human leukocyte antigen (HLA) antibodies (DSAs) against anti-HLA-A, -B, -C, and -DRB1 in HLA-mismatched hematopoietic stem cell transplantation (HSCT) is associated with graft failure. DSAs against HLA-A, -B, -C, and -DRB1 with a mean fluorescence intensity (MFI) of greater than > 1,000 was shown to increase the risk of graft failure in single-unit umbilical cord blood transplantation (UCBT). Nevertheless, the impact of DSAs against HLA-DP or -DQ on transplantation outcomes is not fully understood. In this report, we present a case of UCBT in a patient with myelodysplastic syndrome who was positive for DSAs against HLA-DP with MFI of 1,263 before UCBT but successfully achieved neutrophil engraftment. If HLA-DP or -DQ is mismatched in UCBT, evaluating DSAs against HLA-DP or -DQ is crucial to avoid graft failure. However, the criteria for DSAs against HLA-A, -B, -C, and -DRB1 may not be directly applicable to those against HLA-DP or -DQ.

[Impact of immunosuppression intensified conditioning regimen for patients with strong positive pre-transplantation donor-specific anti-HLA antibodies (DSAs) undergoing haploidentical hematopoietic stem cell transplantation]

Objective: To explore the efficacy of immunosuppression intensified conditioning regimen in patients who have strongly positive donor-specific Anti-HLA antibodies (DSAs) and received a haploidentical hematopoietic stem cell transplantation (haplo-HSCT) . Methods: Clinical data of 10 patients with strongly positive pretransplant DSAs (defined as MFI ≥10000) were retrospectively analyzed in this study. All of them received a haplo-HSCT in the Hematology Department of Shanghai Zhaxin Traditional Chinese & Western Medicine Hospital. Results: ① Of all ten patients, three were males, and seven were females, with a median age of 53.5 (36-64) years. Of the 10 patients, three were diagnosed with acute myeloid leukemia, two were myelodysplastic syndromes (MDS), two were chronic myelomonocytic leukemia (CMML), two were in an accelerated phase of chronic myeloid leukemia (CML-AP), and one was primary myelofibrosis (PMF). ② Conditioning regimen consisted of fludarabine (Flu) /busulfan (Bu) combined with whole-body irradiation (TBI) /cyclophosphamide (Cy). ③ On the seventh day after transplantation, the median pretransplant DSA level was MFI 15 999 (10 210-23 417) and 10 787 (0-22 720). ④ Eight patients acquired hematopoietic reconstitution; the median time of neutrophil engraftment was 14 (10-16) days; and 18 (14-20) days for platelet engraftment. After a median follow-up of 12.5 (1.5-27) months, primary graft failure was found in one patient and another with poor graft function. Seven patients remained in a disease remission state, and all were DSA-negative. Conclusions: An intensified immunosuppression conditioning regimen can efficiently decrease the level of donor-specific anti-HLA antibodies (DSAs), leading to good short-term efficacy.

Definitions, incidence and outcome of poor graft function after hematopoietic cell transplantation: A systematic review and meta-analysis

Poor graft function (PGF) after allogeneic hematopoietic stem cell transplantation (HCT) is a serious complication with high morbidity and mortality. The reported incidence of PGF, its risk factors and outcome vary substantially between studies. This variability may be explained by heterogeneity in patient cohorts and HCT strategies, differences in the underlying causes of cytopenia, as well as by differences in PGF definition. In this systematic review and meta-analysis, we provide an overview of the various PGF definitions used and determined the impact of this variability on the reported incidence and outcome. We searched MEDLINE, EMBASE and Web of Science up to July 2022, for any study on PGF in HCT recipients. We performed random-effect meta-analyses for incidence and outcome and subgroup analyses based on different PGF criteria. Among 69 included studies (14.265 HCT recipients), we found 63 different PGF definitions, using various combinations of 11 common criteria. The median incidence of PGF was 7% (IQR: 5-11%, 22 cohorts). The pooled survival of PGF patients was 53% (95% CI: 45-61%, 23 cohorts). The most commonly reported risk factors associated with PGF were history of cytomegalovirus infection and prior graft-versus-host disease. Incidence was lower in studies with strict cytopenic cutoffs, while survival was lower for primary compared to secondary PGF. This work indicates that a standardized, quantitative definition of PGF is needed to facilitate clinical guideline development and to advance scientific progress.

Results of haploidentical transplant in patients with donor-specific antibodies: a survey on behalf of the Spanish Group of Hematopoietic Transplant and Cell Therapy

Background

Donor-specific antibodies (DSAs) are IgG allo-antibodies against mismatched donor HLA molecules and can cause graft failure (GF) in the setting of haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Our aim was to report the experience of the Spanish Group of Hematopoietic Transplant (GETH-TC) in DSA-positive patients who had undergone haplo-HSCT.

Methods

We conducted a survey of patients who underwent haplo-HSCT in GETH-TC centers between 2012 and 2021. Data were collected on the DSA assay used, monitoring strategy, complement fixation, criteria for desensitization, desensitization strategies and transplant outcomes.

Results

Fifteen centers from the GETH-TC responded to the survey. During the study period, 1,454 patients underwent haplo-HSCT. Seventy of the transplants were performed in 69 DSA-positive patients, all of whom lacked a suitable alternative donor; 61 (88%) patients were female (90% with prior pregnancies). All patients received post-transplant cyclophosphamide-based graft-versus-host disease prophylaxis. Regarding baseline DSA intensity, 46 (67%) patients presented mean fluorescence intensity (MFI) >5,000, including 21 (30%) with MFI >10,000 and three (4%) with MFI >20,000. Six patients did not receive desensitization treatment, four of them with MFI <5,000. Of 63 patients receiving desensitization treatment, 48 (76%) were tested after desensitization therapy, and a reduction in intensity was confirmed in 45 (71%). Three patients (5%) experienced an increase in MFI after desensitization, two of whom experienced primary GF. Cumulative incidence of neutrophil engraftment at day 28 was 74% in a median of 18 days (IQR, 15─20); six patients died before engraftment due to toxicity or infection and eight patients had primary GF despite desensitization in seven of them. After a median follow-up of 30 months, two-year overall and event-free survival were 46.5% and 39%, respectively. The two-year cumulative incidence of relapse was 16% and non-relapse mortality (NRM) was 43%. Infection was the most frequent cause of NRM, followed by endothelial toxicity. Multivariate analysis identified baseline MFI >20,000 as an independent risk factor for survival and an increase in titers after infusion as an independent risk factor for GF.

Conclusions

Haplo-HSCT is feasible in DSA-positive patients, with high rates of engraftment after desensitization guided by DSA intensity. Baseline MFI >20,000 and increased intensity after infusion are risk factors for survival and GF.

Comparison of efficacies of haploidentical transplantation and matched sibling donor transplantation in treating T-cell lymphoblastic lymphoma

OBJECTIVE

To investigate the differences in efficacy and safety between haploidentical donor hematopoietic stem cell transplantation (HID-HSCT) and matched sibling donor HSCT (MSD-HSCT) in patients with T-cell lymphoblastic lymphoma (T-LBL).

METHODS

In this retrospective analysis, we enrolled 38 patients who had undergone allogeneic HSCT at our institution between 2013 and 2021. The study participants included 28 patients who underwent HID-HSCT and 10 patients who underwent MSD-HSCT. We compared the patient characteristics and treatment effectiveness and safety between the two groups and evaluated potential prognostic variables for patients with T-LBL.

RESULTS

The median follow-up durations in the HID-HSCT and MSD-HSCT groups were 23.5 (range: 4-111) and 28.5 (range: 13-56) months, respectively. All patients showed full-donor chimerism after hematopoietic stem cell transplantation (HSCT). Except for two patients in the HID-HSCT cohort who developed poor graft function, all patients showed neutrophil and platelet engraftments after HSCT. The cumulative incidences of grades III-IV acute graft-versus-host disease were 37.5% and 28.57% in the HID-HSCT and MSD-HSCT groups, respectively (p = 0.84). The cumulative incidences of limited (34.13% vs. 28.57%, p = 0.82) and extensive (31.22% vs. 37.50%, p = 0.53) chronic graft-versus-host disease did not differ between the two cohorts. In the HID-HSCT and MSD-HSCT cohorts, the estimated 2-year overall survival rates were 70.3% (95% confidence interval [CI]: 54.9%-90.0%) and 56.2% (95% CI: 31.6%-100%), respectively (p = 1.00), and the estimated 2-year progression-free survival (PFS) rates were 48.5% (95% CI: 32.8%-71.6%) and 48.0% (95% CI: 24.6%-93.8%), respectively (p = 0.94). Furthermore, the Cox proportional-hazards model showed that a positive positron emission tomography/computed tomography (PET/CT) status before HSCT in patients who had completed chemotherapy was an independent risk factor for PFS in the multivariate analysis (p = 0.0367).

CONCLUSION

This study showed that HID-HSCT had comparable effectiveness and safety to MSD-HSCT in treating T-LBL. HID-HSCT could serve as an alternate treatment option for T-LBL in patients without an eligible identical donor. Achievement of the PET/CT-negative status before HSCT may contribute to better survival.

"Incidence and significance of donor-specific antibodies in haploidentical stem cell transplantation"

PGF is a devastating complication after allogeneic transplant. We retrospectively analyzed our haploidentical transplant registry to report the incidence and impact of DSA and anti-HLA on engraftment. 107 patients were identified. Median recipient-age of 22, median donor-age of 31. Sixty-two patients had AML (58%), 29 had ALL (27%), 16 (15%) had other malignancies. Sixty-one recipients (57%) had positive anti-HLA, 56 of them had the DSA results available, of these 17 patients had DSAs (15% of the total number of patients, or 28% of patients who have anti-HLA antibodies). The median cumulative MFI was 2062. Sixty-three percent of the DSA were against class-II HLA antigens. The OS, CIR, aGvHD, and cGvHD did not differ between patients with and without anti-HLA antibodies, nor between patients with and without DSA. The gender of the recipient and donor, as well as the gender mismatch between recipient and donor, were statistically associated with the incidence of anti-HLA antibodies. Three patients only developed GF (2.8%), one was primary (0.9%) and the other two secondary GF (1.9%). None of the GF cases was in patients with anti-HLA antibodies or DSA. The presence of anti-HLA or DSAs did not affect the outcomes including the incidence of PGF.

Effects of donor-specific antibodies on engraftment and long-term survival after allogeneic hematopoietic stem cell transplantation-A systematic review and meta-analysis

The presence of donor-specific antibodies (DSAs) have been reported to be associated with an increased risk of primary graft failure following allogeneic hematopoietic stem cell transplantation (allo-HSCT), but its effects on the time to engraftment and long-term outcomes remain unclear. We performed a systematic review and meta-analysis of studies investigating the impact of DSAs on engraftment and long-term survival of patients undergoing allo-HSCT. We systematically searched PubMed, Embase, the Cochrane Library, and CBM. Data were analyzed using RevMan5.4. Pooled hazard ratio (HR), standard mean difference (SMD) or odds ratio (OR) and corresponding 95% confidence interval (CI) are calculated for time-to-event data, continuous data, discontinuous data respectively. 17 eligible studies were included, involving 2169 patients main receiving haploidentical SCT (haplo-SCT) or umbilical cord blood transplantation (UCBT). Meta-analysis showed that DSAs-positive patients are associated with significantly higher risk of GF(OR = 12.87, 95%CI, 6.45-25.70; P < 0.00001; OR = 4.76, 95%CI, 2.88-7.87), poorer neutrophil engraftment (HR = 2.20, 95%CI, 1.02-4.73; P = 0.04; HR = 1.83, 95%CI, 1.46-2.30; P < 0.00001), worse OS (HR = 3.19, 95%CI, 1.85-5.50; P < 0.0001; HR = 1.68, 95%CI, 1.04-2.71; P = 0.03), and inferior PFS (HR = 4.25, 95%CI, 1.59-11.40; P = 0.004; HR = 4.83, 95%CI, 1.65-14.12; P = 0.004) in haplo-SCT and UCBT, respectively.

Graft failure in allogeneic hematopoietic stem cell recipients: diagnosis and treatment

Graft failure is a group of complications after allogeneic hematopoietic stem cell transplantation, which occurs according to different data up to 30%. The group of complications includes primary and secondary graft failure, primary, secondary and transient poor graft function and graft rejection. Diagnostic difficulties consist in the lack of unified diagnostic criteria accepted in the transplantation community and in the dual interpretation of these complications according to the foreign literature. The purpose of this literature review was to identify the most common criteria of different types of graft failure and determine the tactics of diagnosis and treatment. In this review we analyzed data from various literature sources, gave definitions of graft failure and poor graft function. We analyzed the literature data on the methods used to treat these conditions.

Avatrombopag for the treatment of thrombocytopenia in children's patients following allogeneic hematopoietic stem-cell transplantation: A pilot study

Thrombocytopenia following allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a common and life-threatening complication. Thus, new prevention and treatment strategies for post-HSCT thrombocytopenia are urgently required. In recent studies, thrombopoietin receptor agonists (TPO-RA) for treating post-HSCT thrombocytopenia indicated efficiency and safety. The improved effect of post-HSCT thrombocytopenia in adults was found in the administration of avatrombopag which was a new TPO-RA. However, there was no relevant study in the children's cohort. Herein, we retrospectively analyzed the effect of avatrombopag in post-HSCT thrombocytopenia in children. As a result, the overall response rate (ORR) and complete response rate (CRR) were 91% and 78%, respectively. Furthermore, both cumulative ORR and CRR were significantly lower in the poor graft function (PGF)/secondary failure of platelet recovery (SFPR) group compared to the engraftment-promotion group (86.7% vs. 100%, p = 0.002 and 65.0% vs. 100%, p < 0.001, respectively). Achieving OR required a median of 16 days in the PGF/SFPR group while 7 days in the engraftment-promotion group (p = 0.003). Grade III-IV acute graft vs. host disease and inadequate megakaryocytes were identified as risk factors of CRR only in univariate analysis (p = 0.03 and p = 0.01, respectively). No severe adverse events were documented. Conclusively, avatrombopag is an alternatively efficient and safe agent for treating post-HSCT thrombocytopenia in children.

Posttransplant de novo DSA and NDSA affect GvHD, OS, and DFS after haplo-HSCT in patients without pre-existing HLA antibodies of hematological malignancies

To examine the production time, type, and MFI of post-transplantation de novo HLA antibodies, and their effects on haplo-HSCT outcomes, we retrospectively included 116 patients who were negative for pre-existing HLA antibodies. In total, 322 serum samples from pre-transplantation to post-transplantation were dynamically tested by Luminex and single-antigen bead reagents. Patients were divided into: HLA antibody persistently negative group (group 1), the de novo HLA antibody transiently positive group (group 2), the de novo HLA antibody non-persistently positive group (group 3), and the de novo HLA antibody persistently positive group (group 4). Group 4 included DSA+non-DSA (NDSA) (group 4a) and NDSA (group 4b) groups. The detection rate of de novo HLA antibodies was 75.9% (88/116). The median MFI for de novo HLA antibodies was 2439 (1033-20162). The incidence of II-IV aGvHD was higher in group 2 than in group 1 (52.6% vs 17.9%, P < 0.01); in group 4a than in group 1 (87.5% vs 17.9%, P < 0.001); and in group 4a than in group 4b (87.5% vs 40.0%, P = 0.001). The DFS (37.5% vs 85.7%, P < 0.01) and OS (37.5% vs 85.7%, P < 0.01) of group 4a were lower than those of group 1. The DFS (48.0% vs 85.7%, P < 0.01) and OS (56.0% vs 85.7%, P = 0.03) of group 4b were lower than those of group 1. Multivariate analysis showed that de novo HLA antibody being transiently positive (HR: 5.30; 95% CI: 1.71-16.42, P = 0.01) and persistently positive (HR: 5.67; 95% CI: 2.00-16.08, P < 0.01) were both associated with a higher incidence of II-IV aGvHD. Persistently positive de novo HLA antibodies were a risk factor for reduced DFS (HR: 6.57; 95% CI: 2.08-20.70, P < 0.01) and OS (HR: 5.51; 95% CI: 1.73-17.53, P < 0.01). DSA and NDSA can be detected since 15 days after haplo-HSCT in patients without pre-existing HLA antibodies, and affect aGvHD, DFS, and OS. Haplo-HSCT patients must be monitored for HLA antibodies changes for appropriate preventive clinical management, and we recommend that 1-month post-transplantation is the best test time point.

Successful desensitization of high level donor-specific anti-HLA antibody in patients with hematological diseases receiving haploidentical allografts

Donor-specific anti-human leukocyte antigen (HLA) antibody (DSA) is associated with a higher incidence of graft failure and mortality in HLA-mismatched allograft settings. However, the optimal protocol of desensitization for patients with positive DSA remains uncertain. We investigated the effectiveness of a desensitization protocol, including rituximab, high-dose intravenous immunoglobulin (IVIG), and a single session of plasma exchange (PE), for haploidentical allograft recipients with a high mean fluorescence intensity (MFI) level of DSA (≥ 5,000). Eleven patients with hematological disease who had positive DSA (median, 11,676, range 5387-20,435) were desensitized by the protocol. All of the patients achieved hematopoietic recovery. The median times for neutrophil and platelet engraftment were 13 (range, 11-26) days and 19 (range, 11-90) days, respectively. Grade II-IV acute graft-versus-host disease (GVHD) was seen in one patient and was controlled completely. Chronic cutaneous GVHD was seen in eight patients. Nine patients are alive with good performance so far. One patient suffered extramedullary relapse, and one patient died of transplantation-associated thrombotic microangiopathy. The 1-year probability of overall survival was 81.8%. These results suggest that successful desensitization could be obtained by a combination of rituximab, high-dose IVIG, and PE for haploidentical allograft recipients with high MFI levels of DSA.

Impact of Donor-to-Recipient ABO Mismatch on Outcomes of Antithymocyte Globulin-Based Peripheral Blood Stem Cell-Derived Myeloablative Conditioning Haploidentical Stem Cell Transplantation

ABO incompatibility is common in hematopoietic stem cell transplantation (HSCT); however, the impact of donor-recipient ABO compatibility on transplantation outcomes in different HSCT settings is controversial. Moreover, haploidentical stem cell transplantation (haplo-SCT) with peripheral blood stem cell (PBSC)-derived grafts has not been well investigated. The present study aimed to investigate the impact of ABO incompatibility on post-transplantation outcomes, engraftment kinetics, blood product requirements, transfusion independence, and the incidence of poor graft function (PGF) in antithymocyte globulin (ATG)-based haplo-SCT with PBSC grafts during long-term follow-up. We prospectively evaluated 510 patients with hematologic malignancies who underwent haplo-SCT after myeloablative conditioning (MAC). The primary endpoint was overall survival (OS), and secondary endpoints were nonrelapse mortality (NRM), graft-versus-host disease (GVHD), relapse, neutrophil and platelet engraftment, blood transfusion requirements, transfusion independence, and the incidence of PGF. There was no significant association between ABO matching and OS, disease-free survival (DFS), relapse, NRM, grade II-IV acute GVHD, grade III-IV acute GVHD, and moderate and severe chronic GVHD. There were also no significant differences in neutrophil and platelet engraftment, blood transfusion independence, and transfusion requirements at 30, 60, 90, 180, and 365 days post-transplantation among patients with ABO matching and those with minor, major, or bidirectional ABO incompatibility. Donor-recipient ABO matching did not differ significantly according to graft function (good versus poor). ABO incompatibility status has no major impact on patient outcomes in patients with hematologic malignancies undergoing ATG-based MAC haplo-SCT with PBSC-derived grafts.

The Impact of Panel Reactive Antibodies and Different Desensitization Methods on Pediatric Allogeneic Hematopoietic Stem Cell Transplantation Outcomes

INTRODUCTION

In highly sensitized patients who have panel reactive antibodies (PRAs) before hematopoietic stem cell transplantation, primary graft failure risk may increase. In this study, we aimed to determine the association of PRA with engraftment, and graft versus host disease (GVHD) in pediatric patients.

MATERIALS AND METHODS

Forty-three PRA-positive and 42 PRA-negative patients were taken into study. Both groups were compared in terms of graft failure, acute GVHD, viral infection and survival rates. PRA-positive group was also divided into 2 according to treatment modality (steroid-only group/combination therapy) and compared for the same parameters.

RESULTS

There was no difference in PRA-positive and negative patients in terms of graft failure, acute GVHD and viral infections. Analysis of the PRA-positive group in itself showed that there was also no difference in terms of graft failure and viral infection frequency. The only difference is that acute grade 3 to 4 GVHD was higher in the steroid-only group. The 100-day overall survival was 90.2% and 90.4% for the PRA-positive and negative groups, respectively.

CONCLUSIONS

Different treatment strategies like plasmapheresis, steroid, rituximab, or combination therapies can be used for the desensitization of PRA-positive patients before hematopoietic stem cell transplantation. Patient-specific treatment modality for sensitized patients before transplant can increase the success rate.

Treatment of allosensitized patients receiving allogeneic transplantation

Treatment with PE, rituximab, IVIg, and donor buffy coat is effective in promoting engraftment in patients with DSA <20 000 MFI.

Patients with persistent positive C1q at transplant have a higher risk of engraftment failure and poor survival.

Donor-specific anti-HLA antibodies (DSAs) are a major cause of engraftment failure in patients receiving haploidentical stem cell transplantation (HaploSCT). Effective treatments are needed for these patients, who often have no other donor options and/or are in need to proceed urgently to transplantation. We studied a multimodality treatment with alternate-day plasma exchange (PE), rituximab, intravenous γ globulin (IVIg) and an irradiated donor buffy coat for patients with DSAs at 2 institutions. Thirty-seven patients with a median age of 51 years were treated with this desensitization protocol. Treatment outcomes were compared with a control group of HaploSCT patients without DSAs (n = 345). The majority of patients in the DSA group were female (83.8% vs 37.1% in controls, P < .001) and received stem cells from a child as the donor (67.6% vs 44.1%, P = .002). Mean DSA level before and after desensitization was 10 198 and 5937 mean fluorescence intensity (MFI), respectively, with mean differences of 4030 MFI. Fourteen of 30 tested patients (46.7%) had C1q positivity, while 8 of 29 tested patients (27.6%) remained positive after desensitization. In multivariable analysis, patients with initial DSA > 20 000 MFI and persistent positive C1q after desensitization had a significantly lower engraftment rate, which resulted in significantly higher non-relapse mortality and worse overall survival (OS) than controls, whereas graft outcome and survival of patients with initial DSA < 20 000 MFI and those with negative C1q after treatment were comparable with controls. In conclusion, treatment with PE, rituximab, IVIg, and donor buffy coat is effective in promoting engraftment in patients with DSAs ≤20 000 MFI.

Haploidentical donor transplant is associated with secondary poor graft function after allogeneic stem cell transplantation: A single-center retrospective study

Background

Secondary poor graft function (sPGF) is a serious complication after allogeneic hematopoietic stem cell transplantation (allo‐HSCT) related to poor outcome. We aimed to retrospectively evaluate the morbidity and hazard elements of sPGF after allo‐HSCT.

Methods

Eight hundred and sixty‐three patients who achieved initial engraftment of both neutrophils and platelets were retrospectively reviewed in this study.

Results

Fifty‐two patients developed sPGF within 180 days post‐transplants, with the median onset time was 62 days (range, 34–121 days) post‐transplants. The overall cumulative incidence of sPGF within 180 days post‐transplantation was 6.0%, with 3.4%, 3.4%, and 10.1%, respectively, in matched sibling donor (MSD), matched unrelated donor (MUD), and haploidentical donor (HID) transplant (p < 0.0001). Multivariable analysis showed that HID (HID vs. MSD: hazard ratio [HR] 2.525, p = 0.004; HID vs. MUD: [HR] 3.531, p = 0.017), acute graft versus host disease (aGVHD) within +30 days ([HR] 2.323, p = 0.003), and cytomegalovirus (CMV) reactivation ([HR] 8.915, p < 0.0001) within +30 days post‐transplants were hazard elements of sPGF. The patients with sPGF had poorer survival than good graft function (51.7±8.1% vs. 62.9±1.9%, p < 0.0001). Our results also showed that only CMV reactivation was the hazard element for the development of PGF in HID transplant ([HR] 12.521 p < 0.0001).

Conclusion

HID transplant is also an independent hazard element of sPGF except for aGVHD and CMV reactivation.

The impact of donor-specific anti-human leukocyte antigen antibodies in salvage haploidentical hematopoietic cell transplantation with posttransplant cyclophosphamide in patients with nonmalignant disorders

The presence of donor-specific anti-human leukocyte antigen (HLA) antibodies (DSAs) has been recognized as a major risk factor for graft failure (GF) after haploidentical hematopoietic cell transplantation with posttransplant cyclophosphamide (haplo-PTCy). However, the role of DSAs in salvage haplo-PTCy for rescuing patients with nonmalignant disorders (NMDs) has not yet been reported. The present study retrospectively analyzed 22 patients with NMDs who underwent salvage haplo-PTCy from January 2008 to December 2017. The median age at the time of the rescue haplo-PTCy was 9 years (range, 1-26 years). Median time from the first transplant to second haplo-PTCy was 56 days (range, 37-591 days). Among all patients, six (27.3%) had DSAs, with a median DSA strength (mean fluorescence intensity [MFI]) of 5201 (range, 1412-11,543) in the first DSA testing. In addition, the median DSA MFI was 2672 (range, 832-10,498) before the bone marrow infusion. Overall, GF occurred in 5 (25%) of the 20 assessable patients. Three of four (75%) patients with DSAs experienced GF versus 2 of 16 (12.5%) DSA-negative patients (P = 0.032). The median DSA MFI for patients with GF was 6437 (range, 1412-10,498) versus 1845 (range, 832-2672) for those who engrafted or had early death (P = 0.030). One-year event-free survival was significantly lower in DSA-positive patients than in those without DSAs (16.7% vs. 62.5%, P = 0.002). DSA-negative patients had an acceptable 1-year survival of 62.5%. In conclusion, this study suggests that DSAs may be associated with deleterious outcomes after salvage haplo-PTCy in patients with NMDs.

Correlation analysis between virtual and Complement-Dependent-Cytotoxicity crossmatch in a monocenter retrospective series of 118 allografted patients

PURPOSE OF THE STUDY

The detection of patients' anti-HLA antibodies before allogeneic hematopoietic stem cell transplantation (HSCT) may affect post-transplant outcome, due to a potential detrimental impact on engraftment or toxicity-related issues. Crossmatch (XM) techniques provide support to physicians during the pre-transplant phase but the role of Complement-Dependent Cytotoxicity XM (CDC-XM) is not well-defined when performed routinely and in parallel with the virtual XM.

PATIENTS AND METHODS

We report here our experience with both virtual and CDC-XM tests on n = 118 patients undergoing search for a donor other than HLA-identical sibling from July 2013 to June 2018 at our Institution. When anti-HLA antibodies (Abs) were present, they were classified as donor-specific Abs (DSA) or non-DSA.

RESULTS

On the n = 118 patients, n = 35 (29.7 %) had a positive virtual XM test (of which one of more DSA were found in n = 8; 6.8 %) and n = 5 had a positive CDC-XM test. These latter, positive for HLA class II only, were interpreted as false-positive results due to prior administration of anti-CD20 to the patients, all affected by lymphoma; none of them had a positive virtual XM for anti-HLA Abs of class II. Importantly, all these patients successfully engrafted, further supporting the lack of significant impact of CDC-XM positive results in this series.

CONCLUSIONS

According to our data on more than a hundred patients, routinely performed CDC-XM does not seem to add significant information with respect to virtual XM. We cannot exclude the usefulness of CDC-XM in specific situations, although a positive CDC-XM result was an unfrequent event.

Second haploidentical stem cell transplantation for primary graft failure

We report the outcome of 19 patients who experienced primary graft failure (PrGF) after a haploidentical (HAPLO), unmanipulated bone marrow transplant. The median age of patients was 52 years; the conditioning regimen of the first HAPLO transplant was either full dose total body irradiation (TBI) or fludarabine, busulfan, and thiotepa (TBF); PTCY was given to all patients together with cyclosporine and mycophenolate. All 19 patients with PrGF received a second HAPLO graft, at a median interval of 42 days (34-82) after HSCT, using the Baltimore protocol and G-CSF mobilized PB from the same (n = 13) or another HAPLO family donor (n = 6). GvHD prophylaxis was again PTCY-based; 14/19 patients had trilineage recovery (74%) and 1-year survival was 66%. Engraftment at second HAPLO was seen in 7/8 patient with, and in 5/7 patients without donor-specific antibodies (DSA). In a multivariate logistic regression analysis on the original group of 503 patients, there was a trend for a reduced dose of busulfan, to increase the risk of PrGF (p = 0.1). In conclusion, patients with PrGF following a HAPLO transplant, can be rescued with a second early HAPLO transplant, using the same or a different donor.

Advances in the understanding of poor graft function following allogeneic hematopoietic stem-cell transplantation

Poor graft function (PGF) following allogeneic hematopoietic stem-cell transplantation (allo-HSCT) is a life-threatening complication and is characterized by bilineage or trilineage blood cell deficiency and hypoplastic marrow with full chimerism. With the rapid development of allo-HSCT, especially haploidentical-HSCT, PGF has become a growing concern. The most common risk factors illustrated by recent studies include low dose of infused CD34+ cells, donor-specific antibody, cytomegalovirus infection, graft versus host disease (GVHD), iron overload and splenomegaly, among others. Because of the poor prognosis of PGF, it is crucial to uncover the underlying mechanism, which remains elusive. Recent studies have suggested that the bone marrow microenvironment may play an important role in the pathogenesis of PGF. Deficiency and dysfunction of endothelial cells and mesenchymal stem cells, elevated reactive oxygen species (ROS) levels, and immune abnormalities are believed to contribute to PGF. In this review, we also discuss recent clinical trials that evaluate the safety and efficacy of new strategies in patients with PGF. CD34+-selected stem-cell boost (SCB) is effective with an acceptable incidence of GVHD, despite the need for a second donation. Alternative strategies including the applications of mesenchymal stem cells, N-acetyl-l-cysteine (NAC), and eltrombopag have shown favorable outcomes, but further large-scale studies are needed due to the small sample sizes of the recent clinical trials.

[Relevance of antibodies in hematopoietic stem cell transplantation: Antibodies anti-HLA, anti-platelets, anti-granulocytes, anti-erythrocytes and anti-MICA. Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

The presence of allo-antibodies in the serum of a recipient awaiting hematopoietic stem cell transplantation (HSCT) may have an impact on transfusion efficiency and/or donor choice, especially in the absence of an identical sibling donor. Prior to transplantation, donor specific anti-HLA (Human Leukocyte Antigen) antibodies (DSA) have a recognized effect on transplant outcome, correlated with the increasing MFI value and with the ability of such antibody to fix the complement fraction. Anti-platelet antibodies (anti-HLA class I and anti-HPA [Human Platelet Antigen]) are better involved in transfusion inefficiency and can be responsible for refractory status. ABO incompatibilities require a specific treatment of the graft in presence of high titer to avoid hemolytic adverse effects. Investigations of these antibodies should be carried out on a regular basis in order to establish appropriate transfusion recommendation, select an alternative donor when possible or adapt the source of cells. After transplantation, in case of delayed recovery or graft rejection, long term aplasia, persistent mixed chimerism or late release, and after elimination of the main clinical causes, a biological assessment targeted on the different type of antibodies will have to be performed in order to orient towards the cause or the appropriate therapy. Further studies should be carried out to determine the impact of anti-MICA antibodies and recipient specific anti-HLA antibodies, on the outcome of the transplantation.

HLA antibodies in haematopoietic stem cell transplantation

The negative impact of donor specific HLA alloantibodies in solid organ transplantation is well known and understood within the histocompatibility and immunogenetics community. However the influence of donor-specific antibodies in the outcome of haematopoietic stem cell transplantation is less well regarded. As donor choices have evolved from HLA matched siblings and extremely well matched unrelated donors to mismatched cord blood and haplo-identical-related donors, we are now identifying more patients with antibodies reactive against their donor mismatches. The clinical significance of the antibodies that can be detected has not yet been fully elucidated.

Rituximab for desensitization during HLA-mismatched stem cell transplantation in patients with a positive donor-specific anti-HLA antibody

To define the efficacy of a single dose of 375 mg/m² rituximab for DSA-positive patients with 2000 ≤ MFI < 10,000, we enrolled a prospective clinical cohort including patients with positive DSA treated with rituximab (n = 55, cohort A), a matched-pair cohort including cases with negative DSA (n = 110, cohort B) and a historical cohort including subjects with 2000 ≤ MFI < 10,000 without receiving any treatment for DSA (n = 22, cohort C). The incidences of primary poor graft function (PGF) in cohort A and cohort B were 5% and 1% (P = 0.076), respectively, both of which were lower than that in cohort C (27%, P < 0.001, for all). Rituximab was associated with a reduced incidence of primary PGF (HR 0.200, P = 0.023). The 3-year nonrelapse mortality of patients in cohort A and cohort B were 23% and 24%, respectively, both of which were lower than that in the cohort C (37%), although no statistical significance was observed. These results led to a low 3-year overall survival in patients in the cohort C (58%) compared with those in the cohort A (71%) and the cohort B (73%). We suggest that a single dose of rituximab could be effectively used to prevent the onset of primary PGF. The prospective cohort of this study is registered at http://www.chictr.org.cn/ChiCTR-OPC-15006672.

How we perform haploidentical stem cell transplantation with posttransplant cyclophosphamide

HLA-haploidentical hematopoietic stem cell transplantation is now one of the most commonly employed alternative donor techniques, with most centers applying T-cell-replete strategies such as that developed by the Baltimore group using high-dose posttransplant cyclophosphamide. HLA-haploidentical hematopoietic stem cell transplantation using posttransplant cyclophosphamide is associated with low rates of severe graft-versus-host disease and nonrelapse mortality and does not require graft manipulation or storage, which results in a low graft acquisition cost. Its remarkable safety when used with reduced-intensity conditioning has been demonstrated in patients up to 75 years old with outcomes similar to those of patients in their 50s. Several large, registry-based retrospective studies have confirmed the efficacy of HLA-haploidentical hematopoietic stem cell transplantation with posttransplant cyclophosphamide, achieving results comparable to those of HLA-matched hematopoietic stem cell transplantation. In this article, we describe our approach to this rapidly available and clinically simple platform and address some of the key clinical questions associated with its use.

How we perform haploidentical stem cell transplantation with posttransplant cyclophosphamide

HLA-haploidentical hematopoietic stem cell transplantation is now one of the most commonly employed alternative donor techniques, with most centers applying T-cell-replete strategies such as that developed by the Baltimore group using high-dose posttransplant cyclophosphamide. HLA-haploidentical hematopoietic stem cell transplantation using posttransplant cyclophosphamide is associated with low rates of severe graft-versus-host disease and nonrelapse mortality and does not require graft manipulation or storage, which results in a low graft acquisition cost. Its remarkable safety when used with reduced-intensity conditioning has been demonstrated in patients up to 75 years old with outcomes similar to those of patients in their 50s. Several large, registry-based retrospective studies have confirmed the efficacy of HLA-haploidentical hematopoietic stem cell transplantation with posttransplant cyclophosphamide, achieving results comparable to those of HLA-matched hematopoietic stem cell transplantation. In this article, we describe our approach to this rapidly available and clinically simple platform and address some of the key clinical questions associated with its use.

Granulocyte Colony-Stimulating Factor-Primed Unmanipulated Haploidentical Blood and Marrow Transplantation

Granulocyte colony-stimulating factor (G-CSF), a growth factor for neutrophils, has been successfully used for stem cell mobilization and T cell immune tolerance induction. The establishment of G-CSF-primed unmanipulated haploidentical blood and marrow transplantation (The Beijing Protocol) has achieved outcomes for the treatment of acute leukemia, myelodysplastic syndrome, and severe aplastic anemia with haploidentical allografts comparable to those of human leukocyte antigen (HLA)-matched sibling donor transplantation. Currently, G-CSF-mobilized bone marrow and/or peripheral blood stem cell sources have been widely used in unmanipulated haploidentical transplant settings. In this review, we summarize the roles of G-CSF in inducing T cell immune tolerance. We discuss the recent advances in the Beijing Protocol, mainly focusing on strategies that have been used to improve transplant outcomes in cases of poor graft function, virus infections, and relapse. The application of G-CSF-primed allografts in other haploidentical modalities is also discussed.

Impact of CD34+ cell dose on reduced intensity conditioning regimen haploidentical hematopoietic stem cell transplantation

OBJECTIVES

Haploidentical hematopoietic stem cell transplant (haplo-SCT) has been associated with higher rates of graft rejection, and a higher dose of CD34+ cell dose is frequently requested. We aim to explore the impact of CD34+ cell dose in peripheral blood stem cell (PBSC) grafts using reduced intensity conditioning (RIC) in haplo-SCT.

METHODS

Sixty-eight consecutive haplo-SCT in adult patients were included. Graft-vs-host disease (GVHD) prophylaxis consisted on ATG, PTCy, and CsA. The cohort was divided in two groups using CD34+ dose of ≥ 9 × 10⁶ CD34+/Kg as cutoff point. Median follow-up was 8.9 months.

RESULTS

Median cell dose infused was 9.32 × 10⁶ CD34+/Kg. Forty (58.8%) recipients received grafts with CD34+ cells ≥9 × 10⁶ /kg. The infusion ≥ 9 × 10⁶ CD34+/Kg cell dose had a negative impact in overall survival (P = .03) after adjusting for age at transplant. The cumulative incidence of acute GVHD and graft failure were not significantly influenced per CD34+ cell dose. Only four recipients had grade III aGVHD, and all of them received grafts with a CD34+ cell dose ≥ 9 × 10⁶ .

CONCLUSION

In RIC haplo-SCT, recipients may not benefit from PBSC grafts with a CD34+/kg cell dose higher than 9 × 10⁶ cells/kg, as it can have an adverse impact in post-transplant outcome.