Reduced-intensity conditioning therapy with busulfan, fludarabine, and antithymocyte globulin for HLA-haploidentical hematopoietic cell transplantation in acute leukemia and myelodysplastic syndrome

Individualized rabbit anti-thymocyte globulin dosing in adult haploidentical hematopoietic cell transplantation with high-risk hematologic malignancy: Exposure-response analysis and population pharmacokinetics simulations

Hematopoietic cell transplantation (HCT) for hematologic malignancies with non-remission disease and/or prior post-transplant relapse have poor relapse-free survival. We previously demonstrated the efficacy of haploidentical reduced-intensity HCT regimen with glucocorticoid-based graft-versus-host disease (GVHD) prophylaxis. We recently showed a possible association between rabbit antithymocyte globulin (rATG) exposure and acute GVHD (aGVHD) risk, leading to hypothesize that optimization of rATG exposure may further improve this regimen. We retrospectively examined the exposure-response association of rATG and key clinical outcomes post haploidentical HCT. We subsequently developed an individualized rATG dosing that optimizes rATG exposure using a previously developed population pharmacokinetic model. Of the 103 patients analyzed, the median age was 47 years (range: 17-70) and majority had a non-remission disease prior to HCT (88%). rATG concentration on day 0 of HCT (Cday_0 ) was the strongest predictor of Grade 2-4 aGVHD through day +100. Patients with Cday_0  ≥ 20 μg/mL had an approximately 3-fold lower risk of Grade 2-4 aGVHD (hazard ratio [HR]: 0.32, 95% confidence interval [CI]: 0.16, 0.62) and Grade 3-4 aGVHD (HR: 0.33, 95% CI: 0.16, 0.68) as well as an approximately 2-fold lower risk of overall mortality (HR: 0.47, 95% CI: 0.28, 0.77) and relapse (HR: 0.50, 95% CI: 0.26, 0.94). In conclusion, this reduced-intensity haploidentical HCT regimen with exposure-optimized rATG may provide a promising option to patients undergoing high-risk HCT for hematologic malignancy. The developed rATG dosing warrant prospective validation.

Haploidentical transplants with a G-CSF/ATG-based protocol: Experience from China

Haploidentical donor stem cell transplantation (haplo-SCT) has made great advances in recent decades. The granulocyte colony-stimulating factor (G-CSF)- and antithymocyte globulin (ATG)-based protocol, which is known as the Beijing Protocol, represents one of the current T-cell repletion strategies in haplo-SCT. The key elements of the Beijing Protocol for graft versus host disease (GvHD) prophylaxis include G-CSF inducing T-cell tolerance and altering graft cell components, as well as ATG administration exerting an immunoregulatory effect for intensive prophylaxis. This review will summarize the GvHD incidence, the underlying novel mechanism for GvHD prophylaxis, how to optimize GvHD prophylaxis, and the recent advances of the Beijing Protocol, mainly focusing on the issues of GvHD.

Low-dose anti-thymocyte globulin plus low-dose post-transplant cyclophosphamide-based regimen for prevention of graft-versus-host disease after haploidentical peripheral blood stem cell transplants: a large sample, long-term follow-up retrospective study

Introduction

The novel low-dose anti-thymocyte (ATG, 5 mg/kg) plus low-dose post-transplant cyclophosphamide (PTCy, 50 mg/kg) (low-dose ATG/PTCy)-based regimen had promising activity for prevention of graft-versus-host disease (GVHD) in haploidentical-peripheral blood stem cell transplantation (haplo-PBSCT), but its impacts on long-term outcomes remain to be defined.

Methods

We performed a large sample, long-term follow-up retrospective study to evaluate its efficacy for GVHD prophylaxis.

Results

The study enrolled 260 patients, including 162 with myeloid malignancies and 98 with lymphoid malignancies. The median follow-up time was 27.0 months. For the entire cohort, the cumulative incidences (CIs) of grade II-IV and III-IV acute GVHD (aGVHD) by 180 days were 13.46% (95% CI, 9.64%-17.92%) and 5.77% (95% CI, 3.37%-9.07%); while total and moderate/severe chronic GVHD (cGVHD) by 2 years were 30.97% (95% CI, 25.43%-36.66%) and 18.08% (95% CI, 13.68%-22.98%), respectively. The 2-year overall survival (OS), relapse-free survival (RFS), GVHD-free, relapse-free survival (GRFS), non-relapse mortality (NRM), and CIs of relapse were 60.7% (95% CI, 54.8%-67.10%), 58.1% (95% CI, 52.2%-64.5%), 50.6% (95% CI, 44.8-57.1%), 23.04% (95% CI, 18.06%-28.40%), and 18.09% (95% CI, 14.33%-23.97%, respectively. The 1-year CIs of cytomegalovirus (CMV) and Epstein-Barr virus (EBV) reactivation were 43.46% (95% CI, 37.39%-49.37%) and 18.08% (95% CI, 13.68%-22.98%), respectively. In multivariate analysis, the disease status at transplantation was associated with inferior survivor outcomes for all patients and myeloid and lymphoid malignancies, while cGVHD had superior outcomes for all patients and myeloid malignancies, but not for lymphoid malignancies.

Discussion

The results demonstrated that the novel regimen could effectively prevent the occurrence of aGVHD in haplo-PBSCT.

Peritransplantation Glucocorticoid Haploidentical Stem Cell Transplantation Is a Promising Strategy for AML Patients With High Leukemic Burden: Comparison With Transplantations Using Other Donor Types

Using a murine haploidentical bone marrow transplantation (BMT) model, we recently showed that peritransplantation administration of glucocorticoid (GC) redistributed donor T cells from the gastrointestinal tract to bone marrow, which resulted in a significant reduction of graft-versus-host disease (GVHD) while promoting graft-versus-leukemia effects. Furthermore, in a retrospective clinical study of patients with acute myelogenous leukemia (AML) undergoing transplantation in non-remission, we also showed that haploidentical stem cell transplantation (haplo-SCT) using peritransplantation GC administration led to a significantly lower relapse rate and better overall survival rate compared with haplo-SCT using post-transplantation cyclophosphamide. In the present study, using the same dataset of patients undergoing GC haplo-SCT, we retrospectively compared with patients with AML undergoing transplantation in non-remission using 3 other donor types: matched sibling donor (MSD), matched unrelated donor (MUD), and umbilical cord blood (UCB). For GC haplo-SCT, 44 patients underwent peripheral blood stem cell transplantation in a single center (Hyogo College of Medicine), with the conditioning treatment consisting of fludarabine, melphalan, anti-thymocyte globulin (2.5 mg/kg), and TBI 3 Gy. Methylprednisolone was given from the start of conditioning treatment, and the GVHD prophylaxis consisted of tacrolimus and methylprednisolone (1 mg/kg). The transplantation outcomes were compared with data of 1889 patients undergoing MSD-SCT (n = 449), MUD-BMT (n = 493), or UCB transplantation (UCBT) (n = 947) in non-CR, which were extracted from the Transplant Registry Unified Management Program data, the largest data registry in Japan. For donor engraftment, significantly faster neutrophil and platelet engraftment was achieved with GC haplo-SCT compared with allo-SCT using the 3 other donor types. Neutrophil engraftment was achieved at a median of 10 days for GC haplo-SCT, and 20 days for MSD-, MUD-, and UCB-transplants. Platelet engraftment was achieved at a median of 19.5 days for GC haplo-SCT, 42 days for MSD-SCT and MUD-BMT, and 43 days for UCBT, respectively. The incidence of grade II-IV acute GVHD was lower after allo-SCTs using MSD (hazard ratio [HR] = 0.465, P = .003), MUD (HR = 0.524, P = .010), and UCB (HR = 0.647, P = .067) compared with GC haplo-SCT. There was no significant difference in the incidence of chronic GVHD between GC haplo-SCT and allo-SCT using the other 3 donor types. Regarding relapse, GC haplo-SCT was associated with a significantly lower risk compared with MSD-SCT (P < .001) or MUD-BMT (P = .004). GC haplo-SCT tended to have a lower risk compared with UCBT (P = .063). Especially, all the 43 evaluable GC haplo-SCT recipients achieved CR after transplantation, whereas 23.9%, 22.8%, and 27.0% of patients who underwent MSD-SCT, MUD-BMT, and UCBT could not achieve CR after transplantation, respectively. Regarding non-relapse mortality, GC haplo-SCT was associated with a significantly higher risk compared with MUD-BMT (P = .014), and tended to have a higher risk compared with MSD-SCT (P = .061). There was no significant difference between GC haplo-SCT and UCBT (P = .600). Allo-SCTs using MSD (HR = 2.548, P < .001), MUD (HR = 2.134, P = .005), and UCB (HR = 2.376, P = .001) lead to significantly higher overall mortality compared with GC haplo-SCT; the adjusted overall survival at 3 years was 19.8% for MSD, 26.1% for MUD, 28.0% for UCB, and 65.1% for GC haplo. Thus GC haplo-SCT is a promising treatment option for patients with AML with a high leukemic burden.

The infusion of ex vivo, interleukin-15 and -21-activated donor NK cells after haploidentical HCT in high-risk AML and MDS patients-a randomized trial

Clinical effect of donor-derived natural killer cell infusion (DNKI) after HLA-haploidentical hematopoietic cell transplantation (HCT) was evaluated in high-risk myeloid malignancy in phase 2, randomized trial. Seventy-six evaluable patients (aged 21-70 years) were randomized to receive DNKI (N = 40) or not (N = 36) after haploidentical HCT. For the HCT conditioning, busulfan, fludarabine, and anti-thymocyte globulin were administered. DNKI was given twice 13 and 20 days after HCT. Four patients in the DNKI group failed to receive DNKI. In the remaining 36 patients, median DNKI doses were 1.0 × 10⁸/kg and 1.4 × 10⁸/kg on days 13 and 20, respectively. Intention-to-treat analysis showed a lower disease progression for the DNKI group (30-month cumulative incidence, 35% vs 61%, P = 0.040; subdistribution hazard ratio, 0.50). Furthermore, at 3 months after HCT, the DNKI patients showed a 1.8- and 2.6-fold higher median absolute blood count of NK and T cells, respectively. scRNA-sequencing analysis in seven study patients showed that there was a marked increase in memory-like NK cells in DNKI patients which, in turn, expanded the CD8⁺ effector-memory T cells. In high-risk myeloid malignancy, DNKI after haploidentical HCT reduced disease progression. This enhanced graft-vs-leukemia effect may be related to the DNKI-induced, post-HCT expansion of NK and T cells. Clinical trial number: NCT02477787.

A uniform conditioning regimen of busulfan, fludarabine, and antithymocyte globulin for allogeneic haematopoietic cell transplantation from haploidentical family, matched sibling, or unrelated donors-A single-centre, prospective, explorative study

In a prospective, explorative study, the donor-source difference of haploidentical family (HF), matched sibling (MS), and unrelated donors (UD) was evaluated for the outcome of haematopoietic cell transplantations (HCT) in 101 patients with acute myeloid leukaemia (AML) in complete remission (CR). To eliminate compounding effects, a uniform conditioning regimen containing antithymocyte globulin (ATG) was used. After transplantation, there was a significantly higher cumulative incidence of acute graft-versus-host disease (GVHD) in HF-HCT patients (49%, 7%, and 16% for HF-, MS- and UD-HCT respectively; p < 0.001). A quarter of acute GVHD cases observed in HF-HCT patients occurred within three days of engraftment and were characterized by diffuse skin rash, fever, weight gain, and hypoalbuminaemia. This peri-engraftment acute GVHD was not observed in MS-HCT or UD-HCT patients. Additionally, a significantly higher proportion of HF-HCT patients achieved complete donor chimaerism in the peripheral mononuclear cells at one month (88%, 46%, and 69% for HF-, MS- and UD-HCT respectively; p = 0.001). There was no significant difference in engraftment, chronic GVHD, leukaemia recurrence, non-relapse mortality, and patient survival. In patients with AML in CR who received HCT using ATG-containing conditioning, stronger donor-patient alloreactivity was observed in HF-HCT, in terms of increased acute GVHD and higher likelihood of complete donor chimaerism.

Decoding lymphomyeloid divergence and immune hyporesponsiveness in G-CSF-primed human bone marrow by single-cell RNA-seq

Granulocyte colony-stimulating factor (G-CSF) has been widely used to mobilize bone marrow hematopoietic stem/progenitor cells for transplantation in the treatment of hematological malignancies for decades. Additionally, G-CSF is also accepted as an essential mediator in immune regulation, leading to reduced graft-versus-host disease following transplantation. Despite the important clinical roles of G-CSF, a comprehensive, unbiased, and high-resolution survey into the cellular and molecular ecosystem of the human G-CSF-primed bone marrow (G-BM) is lacking so far. Here, we employed single-cell RNA sequencing to profile hematopoietic cells in human bone marrow from two healthy donors before and after 5-day G-CSF administration. Through unbiased bioinformatics analysis, our data systematically showed the alterations in the transcriptional landscape of hematopoietic cells in G-BM, and revealed that G-CSF-induced myeloid-biased differentiation initiated from the stage of lymphoid-primed multipotent progenitors. We also illustrated the cellular and molecular basis of hyporesponsiveness of T cells and natural killer (NK) cells caused by G-CSF stimulation, including the potential direct mechanisms and indirect regulations mediated by ligand–receptor interactions. Taken together, our data extend the understanding of lymphomyeloid divergence and potential mechanisms involved in hyporesponsiveness of T and NK cells in human G-BM, which might provide basis for optimization of stem cell transplantation in hematological malignancy treatment.

Association between the pharmacokinetics of rabbit anti-thymocyte globulin and acute graft-versus-host disease in patients who received haploidentical hematopoietic stem cell transplantation

Anti-thymocyte globulin (ATG) is an important prophylactic drug against acute graft-versus-host disease (aGVHD) after haploidentical hematopoietic stem cell transplantation (haplo-HSCT). This study analyzed the pharmacokinetics of rabbit ATG 2.5 mg/kg and its effect against aGVHD in 24 patients undergoing unmanipulated haplo-HSCT. All patients had hematological malignancies not in remission. The median absolute lymphocyte count (ALC) before rabbit ATG administration was 9.5/µL (range 0-41/µL). The grade ≥ II aGVHD group had a significantly lower median rabbit ATG concentration on days 0 (C₀) and 7 (C₇) and areas under the curve on days 0-7 (AUC_0-7) and 0-32 (AUC_0-32) than the grade 0-I aGVHD group. Among the four parameters, C₀ was the most optimal for predicting aGVHD according to the receiver-operating characteristic (ROC) analysis (area under the ROC curve 0.893; 95% confidence interval 0.738-1.000). The high C₀ (≥ 27.8 µg/mL) group had significantly lower cumulative incidence of grade ≥ II aGVHD on day 100 than the low C₀ (< 27.8 µg/mL) group (13.8% vs. 88.9%, p < 0.001). In haplo-HSCT, the C₀ of rabbit ATG is a good predictor of grade ≥ II aGVHD, even though ALC before rabbit ATG administration is not a predictor of aGVHD.

HLA-haploidentical peripheral blood stem cell transplantation following reduced-intensity conditioning with very low-dose antithymocyte globulin for relapsed/refractory acute leukemia in pediatric patients: a single-institution retrospective analysis

The prognosis of relapsed/refractory (R/R) pediatric acute leukemia is extremely poor. We retrospectively reviewed 20 consecutive pediatric patients with R/R acute leukemia who underwent a first HLA-haploidentical peripheral blood stem cell transplantation following reduced-intensity conditioning (haplo-RIC-PBSCT) with very low-dose antithymocyte globulin (ATG) between 2012 and 2019. Of these 20 patients, 7 patients had acute lymphoblastic leukemia, and 13 had acute myeloid leukemia. At the time of haplo-RIC-PBSCT, 15 patients had active disease. The median follow-up duration for survivors was 56 months (range 22-108 months). Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus, short-term methotrexate, methylprednisolone, and ATG 1.25 mg/kg on day-2. The 2-year cumulative incidence of transplant-related mortality and relapse were 5.0% [95% confidence interval (CI) 0.7-30.5%)] and 57.8% (95% CI 37.4-79.6%), respectively. Among the 20 patients, 16 (80.0%) developed grade III-IV acute GVHD, and 2 developed severe chronic GVHD. The 2-year event-free survival and overall survival rates were 40.0% (95% CI 19.3-60.0%) and 50.0% (95% CI 27.1-69.2%), respectively. Although the sample size is small, the survival outcomes of the present study are encouraging.

Immunosuppressant indulges EBV reactivation and related lymphoproliferative disease by inhibiting Vδ2+ T cells activities after hematopoietic transplantation for blood malignancies

Background

Following the extensive use of immunosuppressive drugs in the clinic, immunosuppression-associated side effects have received increasing attention. Epstein-Barr virus (EBV) reactivation and related lymphoproliferative diseases (LPD) are the lethal complications observed after allogeneic hematopoietic cell transplantation (alloHCT). While studies generally suggest an association between immunosuppressants and EBV reactivation, the effects of specific immunosuppressive drugs and which T-cell subsets mediate these correlations are unclear. Vδ2⁺ T cells are correlated with EBV reactivation after alloHCT. Researchers have not determined whether Vδ2⁺ T-cell activities are affected by immunosuppressants and thereby facilitate EBV reactivation and related LPD.

Methods

A clinical cohort study of 170 patients with hematopoietic malignancies who received haploidentical hematopoietic cell transplantation (haploHCT) was performed to investigate whether the early cessation of mycophenolate mofetil (MMF) decreases EBV reactivation and related LPD and to determine whether this change is associated with the recovery of Vδ2 ⁺ T cells after transplantation. The effects of MMF on the expansion and anti-EBV capacity of Vδ2⁺ T cells were detected in vitro and in an immunodeficient mouse model.

Results

A reduction in the course of MMF significantly improved the recovery of Vδ2⁺ T cells from 30 to 90 days after haploHCT (p=0.002, p=0.042 and p=0.035, respectively), accompanied by a significant decrease in EBV reactivation (from 26% to 13%, p=0.033) and EBV-LPD (from 10.6% to 2.4%, p=0.029). The day-30 Vδ2⁺ T level remained an independent factor for EBV reactivation in patients with different MMF durations (p=0.007). In the in-vitro experiments, MMF inhibited Vδ2⁺ T-cell expansion and its cytotoxicity on EBV-transformed malignant cells. Furthermore, the therapeutic and prophylactic effects of adoptively transferred human Vδ2⁺ T cells were attenuated by the MMF treatment in immunodeficient mice with EBV-LPD.

Conclusions

These results elucidated a negative effect of immunosuppressants on the anti-EBV capacity of Vδ2⁺ T cells. Strategies that appropriately relieve the immunosuppression may improve anti-EBV immunity by increasing the activity of Vδ2⁺ T cells after alloHCT.

Current Use of Total Body Irradiation in Haploidentical Allogeneic Hematopoietic Stem Cell Transplantation

Total body irradiation (TBI) is included in the conditioning regimen for allogeneic hematopoietic stem cell transplantation (HSCT), with unique advantages such as uniform distribution over the whole body and decreased exposure to cytotoxic chemotherapeutic agents. For individuals who lack matched sibling or matched unrelated donors, the use of haploidentical donors has been increasing despite challenges such as graft rejection and graft-versus-host disease (GVHD). Although a limited number of studies have been performed to assess the clinical role of TBI in haploidentical HSCT, TBI-based conditioning showed comparable results in terms of survival outcomes, rate of relapse, and GVHD in diverse hematologic malignancies such as leukemia, lymphoma, and multiple myeloma. Advances in supportive care, along with recent technical improvements such as restriction of maximum tolerated dose, appropriate fractionation, and organ shielding, help to overcome diverse adverse events related to TBI. Post-transplantation cyclophosphamide was used in most studies to reduce the risk of GVHD. Additionally, it was found that post-transplantation rituximab may improve outcomes in TBI-based haploidentical HSCT, especially in patients with B-cell lymphoma. Along with the advances of techniques and strategies, the expansion of age restriction would be another important issue for TBI-based haploidentical HSCT considering the current tendency toward increasing age limitation and lack of matched donors. This review article summarizes the current use and future perspectives of TBI in haploidentical HSCT.

Similar transplant outcomes between haploidentical and unrelated donors after reduced-intensity conditioning with busulfan, fludarabine, and anti-thymocyte globulin in patients with acute leukemia or myelodysplastic syndrome

Background

Although T-cell-replete hematopoietic cell transplantation (HCT) from haploidentical donors (HIDs) using anti-thymocyte globulin (ATG) has shown promising outcomes, previous studies often adopted heterogenous graft sources and conditioning.

Methods

We retrospectively compared HCT outcomes from 62 HIDs, 36 partially-matched unrelated donors (PUDs), and 55 matched unrelated donors (MUDs) in patients with acute leukemia or myelodysplastic syndrome using the same graft source of peripheral blood and a reduced intensity conditioning of busulfan, fludarabine, and ATG.

Results

The estimates of 3-yr disease-free survival (DFS) and overall survival (OS) rates were not significantly different among the MUD, HID, and PUD groups, at 46%, “41%, and 36%” for the DFS rate (P=0.844), and 55%, 45%, and 45% for the OS rate (P=0.802), respectively. Cumulative incidence of relapse and non-relapse mortality at 3 yr was similar among different donor types. Subsequent multivariable analyses showed that the sex of the patient (male) and a high/very high disease risk index were independently associated with poorer DFS and OS, while the donor type was not.

Conclusion

T-cell replete HCT from HIDs using an ATG-containing reduced intensity conditioning regimen may be a reasonable option in the absence of matched related donors in patients with acute leukemia or myelodysplastic syndrome.

Influence of HLA 1-3-locus mismatch and antithymocyte globulin administration in unrelated bone marrow transplantation

For patients without an HLA-matched donor, an HLA-mismatched unrelated donor (MMUD) has been considered as an alternative donor in allogeneic hematopoietic cell transplantation (allo-HCT). We conducted a nationwide retrospective study to compare the transplant outcomes among 1-, 2-, and 3-locus (allele/antigen) mismatched unrelated donors (1MMUD n = 2044, 2MMUD n = 492, and 3MMUD n = 73) in allo-HCT and to assess the impact of antithymocyte globulin (ATG) in allo-HCT from 1-3MMUD. 2MMUD and 3MMUD were independent significant adverse factors for grade III-IV acute graft-versus-host disease (GVHD) (hazard ratio [HR] 1.72, p < 0.001 and HR 2.48, p < 0.001), non-relapse mortality (NRM) (HR 1.47, p < 0.001 and HR 2.00, p < 0.001), and overall survival (OS) (HR 1.21, p = 0.0066 and HR 1.60, p = 0.0015). Conversely, the use of ATG was an independent favorable factor for grade III-IV acute GVHD (HR 0.43, p < 0.001), NRM (HR 0.51, p < 0.001), and OS (HR 0.74, p = 0.0012). On the other hand, HLA compatibility and the use of ATG were not associated with a risk of relapse. An interaction test between the number of HLA mismatches and the use of ATG revealed that the effect of ATG on NRM and OS in the 2MMUD group was significantly less than that in the 1MMUD group (HR 1.53, p = 0.036 and HR 2.34, p = 0.0046). This study indicated that the number of HLA mismatches and the use of ATG were significantly associated with not only GVHD, but also NRM and OS. Whereas the use of ATG could improve transplant outcomes in allo-HCT from 1MMUD, its effectiveness with 2MMUD and 3MMUD was limited.

Innate Immune Responses in the Outcome of Haploidentical Hematopoietic Stem Cell Transplantation to Cure Hematologic Malignancies

In the context of allogeneic transplant platforms, human leukocyte antigen (HLA)-haploidentical hematopoietic stem cell transplantation (haplo-HSCT) represents one of the latest and most promising curative strategies for patients affected by high-risk hematologic malignancies. Indeed, this platform ensures a suitable stem cell source immediately available for virtually any patents in need. Moreover, the establishment in recipients of a state of immunologic tolerance toward grafted hematopoietic stem cells (HSCs) remarkably improves the clinical outcome of this transplant procedure in terms of overall and disease free survival. However, the HLA-mismatch between donors and recipients has not been yet fully exploited in order to optimize the Graft vs. Leukemia effect. Furthermore, the efficacy of haplo-HSCT is currently hampered by several life-threatening side effects including the onset of Graft vs. Host Disease (GvHD) and the occurrence of opportunistic viral infections. In this context, the quality and the kinetic of the immune cell reconstitution (IR) certainly play a major role and several experimental efforts have been greatly endorsed to better understand and accelerate the post-transplant recovery of a fully competent immune system in haplo-HSCT. In particular, the IR of innate immune system is receiving a growing interest, as it recovers much earlier than T and B cells and it is able to rapidly exert protective effects against both tumor relapses, GvHD and the onset of life-threatening opportunistic infections. Herein, we review our current knowledge in regard to the kinetic and clinical impact of Natural Killer (NK), γδ and Innate lymphoid cells (ILCs) IRs in both allogeneic and haplo-HSCT. The present paper also provides an overview of those new therapeutic strategies currently being implemented to boost the alloreactivity of the above-mentioned innate immune effectors in order to ameliorate the prognosis of patients affected by hematologic malignancies and undergone transplant procedures.

Clinical Features of Chronic Graft-Versus-Host Disease Following Haploidentical Transplantation Combined with Infusion of a Cord Blood

Our previous studies demonstrated promising outcomes after haploidentical donor transplant combined with unrelated umbilical cord blood (haplo-cord- hematopoietic stem cell transplantation [HSCT]) for hematological disorders. However, clinical profiling regarding chronic graft-versus-host disease (cGVHD) has not yet been fully described under this protocol. This study analyzed the clinical characteristics of cGVHD among 300 patients with hematological malignancies who received haplo-cord-HSCT between January 2012 and July 2016 at our center. During the follow-up, the 5-year cumulative incidence of cGVHD based on the National Institutes of Health (NIH) consensus criteria was 32.2% (95% confidence interval [CI], 28.7-35.7); the 5-year cumulative incidence of moderate to severe cGVHD was 11.4% (95% CI, 9.4-13.4). After the multivariate analysis, the GVHD overall survival (GOS) was associated with relapse, thrombocytopenia, bronchiolitis obliterans syndrome, and steroid-refractory cGVHD. The infused CD34⁺ cells (≥3.46 × 10⁶/kg) from haploidentical grafts were a protective factor affecting GOS. This study proposed a nomogram for predicting GOS using the aforementioned five variables. The concordance index was 0.877 (95% CI, 0.859-0.895) for the accuracy evaluation of the nomogram. Our results suggested that the 5-year cumulative incidence of NIH-defined cGVHD after haplo-cord-HSCT was 32.2%, and this nomogram may help clinicians select reasonable treatment strategies.

Review of Haploidentical Hematopoietic Cell Transplantation

Use of haploidentical (haplo) donors for hematopoietic cell transplantation (HCT) has significantly increased in the last decade. The major advantage with this strategy is universal availability and faster acquisition of the donor, along with affordability and provision of immunotherapy in post-transplantation period. Historically, haplo-HCT was associated with compromised outcomes because of high rates of graft-versus-host disease and graft failure, but after the development of a post-transplantation high-dose cyclophosphamide strategy, which results in selective T-cell depletion, these issues have been addressed to a large extent. Nevertheless, graft failure, high treatment-related mortality due to graft-versus-host disease, infections, delayed immune reconstitution, and disease relapse remain significant concerns. As the experience with haplo-HCTs grows, the clinical outcomes are becoming more at par with those seen with fully matched unrelated donor allogeneic HCTs.

Increased opportunity for prolonged survival after allogeneic hematopoietic stem cell transplantation in patients aged 60-69 years with myelodysplastic syndrome

We conducted a nationwide retrospective study to evaluate the outcomes of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in 651 patients aged 60-69 years with de novo myelodysplastic syndrome (MDS). We divided patients into two groups: 152 and 499 patients with an early and advanced disease status, respectively. The 3-year overall survival (OS) rate of patients with an early disease status was 45.9% (95% confidence interval [CI], 37.0 to 54.2%). A multivariate analysis revealed five adverse factors for OS: performance status (PS) 2-4 (hazard ratio [HR] 4.48; P < .001), poor cytogenetic risk group (HR 1.83; P = .041), male recipient (HR 2.58; P = .003), use of HLA-mismatched related grafts (HR 4.75; P = .003), and unrelated cord blood (HR 2.47; P = .023). The 3-year OS rate of patients with an advanced disease status was 37.2% (95% CI 32.4 to 41.9%). Five factors correlated with worse OS: PS 2-4 (HR 1.72; P = .003), poor cytogenetic risk group (HR 1.49; P = .003), use of HLA-mismatched related grafts (HR 1.96; P = .015), unrelated cord blood (HR 2.05; P < .001), and the high number of red blood cell transfusions before transplantation (HR 1.85; P = .018). The present results revealed the more frequent utilization of allo-HSCT for MDS patients aged 60-69 years, which increases the curative potential.

Haploidentical transplantation outcomes for secondary acute myeloid leukemia: Acute Leukemia Working Party (ALWP) of the European Society for Blood and Marrow Transplantation (EBMT) study

Secondary acute myeloid leukemia (sAML) traditionally has inferior outcomes compared to de novo AML. Allogeneic hematopoietic cell transplantation (HCT) is the sole potentially curative therapy. This study analyzes the outcomes for unmanipulated haploidentical HCT (haploHCT) for sAML using the Acute Leukemia Working Party (ALWP) registry of the European Society for Blood and Marrow Transplantation (EBMT). We identified 154 patients with sAML who underwent haploHCT from 2006 to 2016. Median age at HCT was 60 years with time from diagnosis to HCT 5 months. At transplantation, 69 patients were in first CR and 85 had active disease. Fifty-seven (38.0%) patients underwent myeloablative conditioning and 97 (62.0%) reduced intensity conditioning (RIC) conditioning. Multivariate analysis showed that there was no difference in RI, nonrelapse mortality (NRM), leukemia free survival (LFS), overall survival (OS), or GVHD-free/relapse free survival (GRFS) for conditioning intensity, age, performance status, or graft source. Active disease was associated with higher RI and inferior LFS, OS, and GRFS compared with patients in CR at time of transplant. T-cell depletion with anti-thymoglobulin resulted in higher NRM and inferior LFS, OS, and GRFS compared to post-transplant cyclophosphamide (PTCy) (HR 2.25, 2.01, 2.16, and 1.73, respectively with P values <.05). Our data shows that haploHCT is a feasible alternative for sAML when matched transplantation is unavailable.

Update on current research into haploidentical hematopoietic stem cell transplantation

INTRODUCTION

Haploidentical stem cell transplantation (Haplo-SCT) is currently a suitable alternative worldwide for patients with hematological diseases, who lack human leukocyte antigen (HLA)-matched siblings or unrelated donors. Areas covered: This review summarizes the advancements in Haplo-SCT in recent years, primarily focusing on the global trends of haploidentical allograft, the comparison of outcomes between Haplo-SCT and other transplantation modalities, strategies for improving clinical outcomes, including donor selection, hematopoietic reconstitution promotion, and graft-versus-host disease, and relapse prevention/management, as well as the expanded indications of Haplo-SCT, such as severe aplastic anemia, myeloma and lymphoma. Expert commentary: Haploidentical allografts, including granulocyte colony-stimulating factor-based protocol and a post-transplant cyclophosphamide-based protocol, have been the mainstream strategy for Haplo-SCT. However, there are many unanswered questions in this field.

Prognostic Impact of Donor Source on Allogeneic Hematopoietic Stem Cell Transplantation Outcomes in Adults with Chronic Myelomonocytic Leukemia: A Nationwide Retrospective Analysis in Japan

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapeutic option for patients with chronic myelomonocytic leukemia (CMML). We retrospectively compared the post-transplantation outcomes of 159 patients with CMML who underwent allo-HSCT using 4 types of donor sources: HLA-matched related donor graft, unrelated bone marrow (U-BM), unrelated cord blood (U-CB), and HLA-mismatched related donor graft. The median patient age at allo-HSCT was 54 years (range, 16 to 75 years). In multivariate analyses, the use of HLA-matched related donor grafts correlated with better overall survival than U-BM (hazard ratio [HR], 2.05; 95% confidence interval [CI], 1.21 to 3.48; P = .008), U-CB (HR, 3.80; 95% CI, 2.07 to 6.95; P < .001), or HLA-mismatched related donor grafts (HR, 6.18; 95% CI, 2.70 to 14.15; P < .001). Mortality after the relapse or progression of CMML did not significantly differ among the 4 types of donor source. Transplantation-related mortality was highest in recipients of U-CB (HR, 3.32; 95% CI, 1.33 to 8.26; P = .010). In patients with CMML, allo-HSCT using an alternative donor may contribute to durable remission; however, further improvements in transplantation-related mortality are required for this type of transplantation.

Reduced-Intensity Conditioning with Busulfan, Fludarabine, and Antithymocyte Globulin for Hematopoietic Cell Transplantation from Unrelated or Haploidentical Family Donors in Patients with Acute Myeloid Leukemia in Remission

To investigate the role of antithymocyte globulin (ATG)-containing reduced-intensity conditioning (RIC) in hematopoietic cell transplantation (HCT) from unrelated (UD) or haploidentical family donors (HFD), we conducted a phase 2 trial of 237 patients (age range, 16 to 69 years) with acute myeloid leukemia (AML) in remission. Patients undergoing UD-HCT (n = 93) or HFD-HCT (n = 59) received RIC comprising busulfan, fludarabine, and ATG, 9 mg/kg, whereas those undergoing HCT from matched sibling donors (MSD, n = 85) received myeloablative busulfan and cyclophosphamide conditioning or aforementioned RIC with ATG, 4.5 mg/kg. For graft-versus-host disease (GVHD) prophylaxis, cyclosporine and methotrexate were administered. The median follow-up period was 44.7 months after HCT for 161 survivors. For UD-HCT versus HFD-HCT, there were no significant differences in leukemia recurrence, nonrelapse mortality, relapse-free survival, grades 2 to 4 acute GVHD, and moderate-to-severe chronic GVHD. Furthermore, when the outcomes of UD-HCT and HFD-HCT were combined and compared with those of MSD-HCT, there were no significant differences in leukemia recurrence (3-year cumulative incidence, 30% versus 29%), nonrelapse mortality (3-year cumulative incidence, 7% versus 8%), relapse-free survival (3-year estimate, 63% versus 63%), and grades 2 to 4 acute GVHD (120-day cumulative incidence, 16% versus 13%). Moderate-to-severe chronic GVHD, however, occurred less frequently in UD/HFD-HCT (2-year cumulative incidence, 22% versus 40%; P = .006). The addition of ATG to conditioning regimen was a significant predictor for less chronic GVHD (subdistribution hazard ratio, .59). In AML in remission, UD/HFD-HCT after ATG-containing RIC achieved leukemia control equivalent to that of MSD-HCT. Despite HLA disparity in UD/HFD-HCT, chronic GVHD occurred less frequently after ATG-containing RIC, suggesting a strong GVHD-modulating effect of ATG.

Haploidentical hematopoietic transplantation for the cure of leukemia: from its biology to clinical translation

The present review describes the biology of human leukocyte antigen haplotype mismatched ("haploidentical") transplantation, its translation to clinical practice to cure leukemia, and the results of current transplantation protocols. The 1990s saw what had been major drawbacks of haploidentical transplantation, ie, very strong host-versus-graft and graft-versus-host alloresponses, which led respectively to rejection and graft-versus-host disease (GVHD), being overcome through transplantation of a "mega-dose" of T cell-depleted peripheral blood hematopoietic progenitor cells and no posttransplant pharmacologic immunosuppression. The absence of posttransplant immunosuppression was an opportunity to discover natural killer cell alloreactions that eradicated acute myeloid leukemia and improved survival. Furthermore, it also unveiled the benefits of transplantation from mother donors, a likely consequence of the mother-to-child interaction during pregnancy. More recent transplantation protocols use unmanipulated (without ex vivo T-cell depletion) haploidentical grafts combined with enhanced posttransplant immunosuppression to help prevent GVHD. Unmanipulated grafts substantially extended the use of haploidentical transplantation with results than even rival those of matched hematopoietic transplantation. In T cell-depleted haploidentical transplantation, recent advances were made by the adoptive transfer of regulatory and conventional T cells.

Donor-Derived Natural Killer Cell Infusion after Human Leukocyte Antigen-Haploidentical Hematopoietic Cell Transplantation in Patients with Refractory Acute Leukemia

The optimum method of donor natural killer cell infusion (DNKI) after allogeneic hematopoietic cell transplantation (HCT) remains unclear. Fifty-one patients (age range, 19 years to 67 years) with refractory acute leukemia underwent HLA-haploidentical HCT and underwent DNKI on days 6, 9, 13, and 20 of HCT. Median DNKI doses were .5, .5, 1.0, and 2.0 × 10⁸/kg cells, respectively. During DNKI, 33 of the 45 evaluated patients (73%) developed fever (>38.3°C) along with weight gain (median, 13%; range, 2% to 31%) and/or hyperbilirubinemia (median, 6.2 mg/dL; range, 1.0 mg/dL to 35.1 mg/dL); the toxicity was reversible in 90% of patients. After transplantation, we observed cumulative incidences of neutrophil engraftment (≥500/µL), grade 2 to 4 acute graft-versus-host disease (GVHD), chronic GVHD, and nonrelapse mortality of 84%, 28%, 30%, and 16%, respectively. The leukemia complete remission rate was 57% at 1 month after HCT and 3-year cumulative incidence of leukemia progression was 75%. When analyzed together with our historical cohort of 40 patients with refractory acute leukemia who underwent haploidentical HCT and DNKI on days 14 and 21 only, higher expression of NKp30 (>90%) on donor NK cells was an independent predictor of higher complete remission (hazard ratio, 5.59) and less leukemia progression (hazard ratio, .57). Additional DNKI on days 6 and 9 was not associated with less leukemia progression (75% versus 55%).

Haploidentical transplant for myelodysplastic syndrome: registry-based comparison with identical sibling transplant

Encouraging results from a small sample of patients with myelodysplastic syndrome (MDS) undergoing haploidentical donor (HID) hematopoietic stem cell transplantation (HSCT) must be extended. Furthermore, an algorithm derived from a comparison of the outcomes of HID and identical-sibling donor (ISD) HSCT must be established. Therefore, the outcomes of 454 MDS patients who underwent HSCT from HIDs (n=226) or ISDs (n=228) between 2003 and 2013 that were reported to the Chinese Bone Marrow Transplantation Registry were analyzed. Among the 3/6 HID (n=136), 4-5/6 HID (n=90) and ISD patient groups, the 4-year adjusted cumulative incidences of non-relapse mortality were 34, 29 and 16%, respectively (overall P=0.004), and of relapse were 6, 7 and 10%, respectively (overall P=0.36). The 4-year adjusted probabilities of overall survival were 58, 63 and 73%, respectively (overall P=0.07), and of relapse-free-survival were 58, 63 and 71%, respectively (overall P=0.14); pairwise comparison showed that the difference was only statistically significant in the 3/6 HID vs ISD pair. The data suggest that ISDs remain the best donor source for MDS patients while HIDs (perhaps 4-5/6 HID in particular) could be a valid alternative when an ISD is not available; human leukocyte antigen disparity had no effect on survival among the HID patients.

Survey of experts on therapeutic policies and proposals for the optimal timing for allogeneic peripheral blood stem cell transplantation in transfusion-dependent patients with myelodysplastic syndrome-refractory anemia

BACKGROUND

Most hypomethylating agent (HMA) responders with myelodysplastic syndrome (MDS) eventually need allogeneic stem cell transplantation (SCT) because they often acquire resistance to HMAs within two years of treatment. Considering the nature of MDS and the poor outcomes of SCT when performed after confirming the progression of MDS to acute myeloid leukemia (AML), allogeneic SCT should be performed with caution in patients with low-risk MDS.

METHODS

To address low-risk MDS, the Korean AML/MDS working party group designed a survey for 34 MDS experts in Korea on therapeutic HMA and allogeneic SCT policies for low-risk MDS. The level of consensus was defined as the percentage of agreement among the experts.

RESULTS

With regard to the optimal time for allogeneic SCT for HMA responders with MDS-RA, 76% experts agreed that allogeneic SCT should be performed when a patient has a low platelet count. With regard to the relapse pattern that was most commonly found during HMA treatment in responding patients with MDS-RA, 54% experts agreed that the most common pattern that indicated HMA failure was the gradual worsening of cytopenia.

CONCLUSION

The optimal time to perform allogeneic SCT in RA patients who achieved hematologic complete remission during HMA treatment is when the platelet count decreases. However, these suggestions need to be evaluated in larger future studies. Therefore, careful decisions should be taken at each step of allogeneic SCT to maximize the outcomes for patients with MDS-RA and iron overload.

Advances in haploidentical stem cell transplantation for hematologic malignancies

One of the most important advances in allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the use of alternative donors and cell sources, such as haploidentical transplants (haplo-HSCT) from family donors. Several approaches have been developed to overcome the challenging bidirectional alloreactivity. We discuss these approaches, including ex vivo T-cell-depleted grafts with megadose of CD34(+) cells, not requiring immunosuppression after allogeneic transplantation for graft-versus-host disease (GVHD) prophylaxis, and other strategies using unmanipulated T-cell-replete grafts with intensive immunosuppression or post-transplantation cyclophosphamide to minimize the GVHD. We also address the role of other strategies developed in the context of the haplo-HSCT platforms, such as ex vivo selective depletion of alloreactive donor T-cell subpopulations, infusion of antigen-specific T-cells against several pathogens, and infusion of regulatory T-cells, among other experimental approaches. Finally, some considerations about the selection of the most suitable donor, when more than one family member is available, are also addressed.

How do we choose the best donor for T-cell-replete, HLA-haploidentical transplantation?

In haploidentical stem cell transplantations (haplo-SCT), nearly all patients have more than one donor. A key issue in the haplo-SCT setting is the search for the best donor, because donor selection can significantly impact the incidences of acute and chronic graft-versus-host disease, transplant-related mortality, and relapse, in addition to overall survival. In this review, we focused on factors associated with transplant outcomes following unmanipulated haplo-SCT with anti-thymocyte globulin (ATG) or after T-cell-replete haplo-SCT with post-transplantation cyclophosphamide (PT/Cy). We summarized the effects of the primary factors, including donor-specific antibodies against human leukocyte antigens (HLA); donor age and gender; killer immunoglobulin-like receptor-ligand mismatches; and non-inherited maternal antigen mismatches. We also offered some expert recommendations and proposed an algorithm for selecting donors for unmanipulated haplo-SCT with ATG and for T-cell-replete haplo-SCT with PT/Cy.

Impact of conditioning intensity in T-replete haplo-identical stem cell transplantation for acute leukemia: a report from the acute leukemia working party of the EBMT

BACKGROUND

Increasing numbers of patients are receiving haplo-identical stem cell transplantation (haplo-SCT) for treatment of acute leukemia with reduced intensity (RIC) or myeloablative (MAC) conditioning regimens. The impact of conditioning intensity in haplo-SCT is unknown.

METHODS

We performed a retrospective registry-based study comparing outcomes after T-replete haplo-SCT for patients with acute myeloid (AML) or lymphoid leukemia (ALL) after RIC (n = 271) and MAC (n = 425). Regimens were classified as MAC or RIC based on published criteria.

RESULTS

A combination of post-transplant cyclophosphamide (PT-Cy) with one calcineurin inhibitor and mycophenolate mofetil (PT-Cy-based regimen) for graft-versus-host disease (GVHD) prophylaxis was used in 66 (25%) patients in RIC and 125 (32%) in MAC groups. Patients of RIC group were older and had been transplanted more recently and more frequently for AML with active disease at transplant. Percentage of engraftment (90 vs. 92%; p = 0.58) and day 100 grade II to IV acute GVHD (24 vs. 29%, p = 0.23) were not different between RIC and MAC groups. Multivariable analyses, run separately in AML and ALL, showed a trend toward higher relapse incidence with RIC in comparison to MAC in AML (hazard ratio (HR) 1.34, p = 0.09), and no difference in both AML and ALL in terms of non-relapse mortality (NRM) chronic GVHD and leukemia-free survival. There was no impact of conditioning regimen intensity in overall survival (OS) in AML (HR = 0.97, p = 0.79) but a trend for worse OS with RIC in ALL (HR = 1.44, p = 0.10). The main factor impacting outcomes was disease status at transplantation (HR ≥ 1.4, p ≤ 0.01). GVHD prophylaxis with PT-Cy-based regimen was independently associated with reduced NRM (HR 0.63, p = 0.02) without impact on relapse incidence (HR 0.99, p = 0.94).

CONCLUSIONS

These data suggest that T-replete haplo-SCT with both RIC and MAC, in particular associated with PT-Cy, are valid options in first line treatment of high risk AML or ALL.

Hematopoietic stem cell transplantation for patients with AML in first complete remission

Postremission therapy in patients with acute myeloid leukemia (AML) may consist of continuing chemotherapy or transplantation using either autologous or allogeneic stem cells. Patients with favorable subtypes of AML generally receive chemotherapeutic consolidation, although recent studies have also suggested favorable outcome after hematopoietic stem cell transplantation (HSCT). Although allogeneic HSCT (alloHSCT) is considered the preferred type of postremission therapy in poor- and very-poor-risk AML, the place of alloHSCT in intermediate-risk AML is being debated, and autologous HSCT is considered a valuable alternative that may be preferred in patients without minimal residual disease after induction chemotherapy. Here, we review postremission transplantation strategies using either autologous or allogeneic stem cells. Recent developments in the field of alternative donors, including cord blood and haploidentical donors, are highlighted, and we discuss reduced-intensity alloHSCT in older AML recipients who represent the predominant category of patients with AML who have a high risk of relapse in first remission.

Use of alternative donors for allogeneic stem cell transplantation

For patients without a human leukocyte antigen (HLA)-matched sibling or unrelated donor, options include transplantation from HLA-mismatched related donors, HLA-mismatched unrelated donors, or unrelated cord blood units. Graft failure remains a problem in 10%-20% of cord blood transplants that contain a limited number of hematopoietic cells. Many approaches are tested in clinical trials to offset the risk of graft failure after cord blood transplantation. GVHD remains a hurdle with any HLA mismatched graft. The use of post-transplant cyclophosphamide holds the promise to overcome the HLA barrier and prevent GVHD despite donor mismatch for a full HLA haplotype. Priority should be given to enrolling patients onto transplant protocols addressing the fundamental problems of engraftment, GVHD, relapse or treatment-related mortality tested with one or more of the alternative stem cell sources. Principles for prioritization of alternative stem cell sources are discussed separately for children and adults who cannot be enrolled on clinical trials. It is difficult ranking currently available sources in the face of multiple factors affecting outcomes, rapidly changing transplant technology and without results from comparative trials.

Modern approaches to HLA-haploidentical blood or marrow transplantation

Allogeneic blood or bone-marrow transplantation (alloBMT) is a potentially curative treatment for a variety of haematological malignancies and nonmalignant diseases. Historically, human leukocyte antigen (HLA)-matched siblings have been the preferred source of donor cells owing to superior outcomes compared with alloBMT using other donors. Although only approximately one-third of patients have an HLA-matched sibling, nearly all patients have HLA-haploidentical related donors. Early studies using HLA-haploidentical alloBMT resulted in unacceptably high rates of graft rejection and graft-versus-host disease (GVHD), leading to high nonrelapse mortality and consequently poor survival. Several novel approaches to HLA-haploidentical alloBMT have yielded encouraging results with high rates of successful engraftment, effective GVHD control and favourable outcomes. In fact, outcomes of several retrospective comparative studies seem similar to those seen using other allograft sources, including those of HLA-matched-sibling alloBMT. In this Review, we provide an overview of the three most-developed approaches to HLA-haploidentical alloBMT: T-cell depletion with 'megadose' CD34(+) cells; granulocyte colony-stimulating factor-primed allografts combined with intensive pharmacological immunosuppression, including antithymocyte globulin; and high-dose, post-transplantation cyclophosphamide. We review the preclinical and biological data supporting each approach, results from major clinical studies, and completed or ongoing clinical studies comparing these approaches with other alloBMT platforms.

Unmanipulated Haploidentical Reduced-Intensity Stem Cell Transplantation Using Fludarabine, Busulfan, Low-Dose Antithymocyte Globulin, and Steroids for Patients in Non-Complete Remission or at High Risk of Relapse: A Prospective Multicenter Phase I/II Study in Japan

This prospective, multicenter phase I/II study of unmanipulated HLA-haploidentical reduced-intensity stem cell transplantation using a low dose of anti-T lymphocyte globulin (ATG) and steroid was conducted in 5 institutions in Japan. Thirty-four patients with hematologic malignancies who were in an advanced stage or at a high risk of relapse at the time of transplantation were enrolled. Among them, 7 patients underwent transplantation as a second transplantation because of relapse after the previous allogeneic stem cell transplantation. The conditioning regimen consisted of fludarabine, busulfan, and ATG (Fresenius, 8 mg/kg), and graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus and methylprednisolone (1 mg/kg). All patients except 1 (97.1%) achieved donor-type engraftment. Rapid hematopoietic engraftment was achieved, with neutrophils > .5 × 10(9)/L on day 11 and platelets > 20 × 10(9)/L on day 17.5. Treatment was started for ≥grade I GVHD, and the cumulative incidences of acute grade I and grade II to IV GVHD were 27.5% and 30.7%, respectively. The incidence of chronic GVHD (extensive type) was 20%. Fourteen patients (41.2%) had a relapse. The cumulative incidence of transplantation-related mortality at 1 year after transplantation was 26.5%. The survival rate at day 100 was 88.2%. The survival rates at 1 year for patients with complete remission (CR)/chronic phase (n = 8) and non-CR (n = 26) status before transplantation were 62.5% and 42.3%, respectively. In the multivariate analysis, non-CR status before transplantation was the only factor significant prognostic factor of increased relapse (P = .0424), which tended to be associated with a lower survival rate (P = .0524). This transplantation protocol is safe and feasible, if a suitable donor is not available in a timely manner. As the main cause of death was relapse and not GVHD, more intensified conditioning or attenuation of GVHD prophylaxis and/or donor lymphocyte infusion may be desirable for patients with non-CR status.

[The role of pre-transplant debulking treatment in patients undergoing allogeneic stem cell transplantation for high-risk myelodysplastic syndrome]

Treatment of myelodysplastic syndromes (MDS) remains unsatisfactory. Variable success in the correction of blood cytopenias, reduction of the proportion of marrow myeloblasts, and normalization of cytogenetics has been achieved with a variety of treatment strategies, including the use of immunosuppressive drugs, differentiating agents, conventional chemotherapy, and hypomethylating agents (HMAs) However, in general, responses have not been complete and have been of limited duration; prolongation of survival, if achieved, on average has been in the range of months. Currently, allogeneic hematopoietic stem-cell transplantation (allo-SCT) remains the only approach with curative potential for patients with higher risk/advanced MDS. Yet, despite the beneficial effects of allo-SCT, post-transplant relapse is a major cause of failure. Debulking prior to transplant treatment in patients with MDS is a matter of debate. The achievement of complete remission (CR) before allo-SCT improves post-transplantation outcome, although it is not clear whether this reflects the selection of patients with more responsive disease or is related to a reduction in disease burden. Higher CR rates in patients with MDS are obtained with induction chemotherapy (ICT) than with hypomethylating agents (HMAs), although HMAs may be active in patients with complex karyotypes in whom ICT almost invariably fails. Furthermore, HMAs have a good toxicity profile compared with ICT and may therefore be considered especially in older patients and in patients with comorbidities. However, all interventions aimed at reducing disease burden before allo-SCT expose patients to the risk of complications, which may prevent them from undergoing transplantation. Therefore, up-front allo-SCT is an option, particularly for patients with life-threatening cytopenias. In the absence of prospective randomized trials, the main therapeutic approaches are discussed in this review.

"No donor"? Consider a haploidentical transplant

Haploidentical stem cell transplantation (HaploSCT) is an attractive option for patients requiring a hematopoietic stem cell transplant who do not have an HLA-matched donor, because it is cheaper, can be performed faster, and may extend transplantation to virtually all patients in need. Significant advances have been made in the recent decade with dramatic improvement in treatment outcomes. Historically, overcoming the HLA-incompatibility barrier has been a significant limitation to the expansion of this form of transplant. While ex vivo T-cell depletion effectively prevented the development of acute GVHD, it was associated with a higher treatment-related mortality, in excess of 40% in some series, due to a significant delay in recovery of the adaptive immune system. Newer methods have successfully maintained the memory T cells in the graft and/or selectively depleted alloreactive T cells, and are associated with improved treatment outcomes. Post-transplant cyclophosphamide for GVHD prevention has proven very effective in controlling GVHD with lower incidence of infectious complications and treatment-related mortality-as low as 7% at 1 year-and has become the new standard in how this transplant is performed. Here, we reviewed the current experience with this approach and various other strategies employed to control alloreactivity in this setting, including selective depletion of T cells from the graft, as well as we discuss post-transplantation therapy to prevent disease relapse and improve immunologic reconstitution.

Haploidentical hematopoietic transplantation without T-cell depletion: current status and future perspectives

Human leukocyte antigen (HLA)-haploidentical hematopoietic stem cell transplantation (HLA-haplo HSCT) without T-cell depletion has tremendously progressed over the past 20 years and has become a feasible treatment option for leukemia patients without an HLA-identical sibling donor. Advances in conditioning regimens, graft manipulation, and pharmacological graft-versus-host disease (GVHD) prophylaxis have reduced the risk of fatal graft failure and severe GVHD, two of the most serious complications of traversing the HLA barrier. According to clinical observations, killer immunoglobulin-like receptor (KIR) mismatch and donor-specific anti-HLA (DSA) antibodies-negative status play potential roles in reducing the risk of GVHD and graft failure following HLA-haploidentical SCT. New strategies to improve transplant outcomes include donor lymphocyte, NK cell and selected T-cell subset infusion, mesenchymal stem cell (MSC) co-transplantation and interleukin-2 (IL-2) application. Future challenges remain in improving post-transplant immune reconstitution and finding the best approach to reduce the incidence and severity of GVHD while simultaneously preserving the graft-versus leukemia effect to prevent the recurrence of underlying malignancy.

Feasible outcomes of T cell-replete haploidentical stem cell transplantation with reduced-intensity conditioning in patients with myelodysplastic syndrome

Even with the recent optimization of haploidentical stem cell transplantation (SCT), its role for patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia evolving from MDS (sAML) should be validated. We analyzed the outcomes of consecutive 60 patients with MDS or sAML who received T cell-replete haploidentical SCT after reduced-intensity conditioning with fludarabine, busulfan, and rabbit antithymocyte globuline ± 800 cGy total body irradiation. Patients achieved a rapid neutrophil engraftment after a median of 12 days (range, 8 to 23) and an early immune reconstitution without high incidences of acute graft-versus-host disease (GVHD) II to IV and chronic GVHD (36.7% and 48.3%, respectively). After a median follow-up of 4 years, incidence of relapse and nonrelapse mortality and rate of overall survival and disease-free survival was 34.8%, 23.3%, 46.8%, and 41.9%, respectively. In multivariate analysis, the disease status at peak was a significant predictor for relapse (lower-risk MDS versus higher-risk MDS or sAML; hazard ratio [HR], 5.69; 95% confidence interval [CI], 1.45 to 22.29; P = .013) and disease-free survival (HR, 4.44; 95% CI, 1.14 to 17.34; P = .032). Chronic GVHD was an additional significant predictor for relapse (no versus yes; HR, 2.87; 95% CI, 1.03 to 7.51; P = .043). Our T cell-replete haploidentical SCT may be a feasible option for patients with MDS and sAML without conventional donors.