Haploidentical Hematopoietic Stem Cell Transplantation: A Global Overview Comparing Asia, the European Union, and the United States

NK cell recovery after haploidentical HSCT with posttransplant cyclophosphamide: dynamics and clinical implications

The use of posttransplant cyclophosphamide (PT-Cy) as graft-versus-host disease (GVHD) prophylaxis has revolutionized haploidentical hematopoietic stem cell transplantation (HSCT), allowing safe infusion of unmanipulated T cell-replete grafts. PT-Cy selectively eliminates proliferating alloreactive T cells, but whether and how it affects natural killer (NK) cells and their alloreactivity is largely unknown. Here we characterized NK cell dynamics in 17 patients who received unmanipulated haploidentical grafts, containing high numbers of mature NK cells, according to PT-Cy-based protocols in 2 independent centers. In both series, we documented robust proliferation of donor-derived NK cells immediately after HSCT. After infusion of Cy, a marked reduction of proliferating NK cells was evident, suggesting selective purging of dividing cells. Supporting this hypothesis, proliferating NK cells did not express aldehyde dehydrogenase and were killed by Cy in vitro. After ablation of mature NK cells, starting from day 15 after HSCT and favored by the high levels of interleukin-15 present in patients' sera, immature NK cells (CD62L⁺NKG2A⁺KIR^-) became highly prevalent, possibly directly stemming from infused hematopoietic stem cells. Importantly, also putatively alloreactive single KIR⁺ NK cells were eliminated by PT-Cy and were thus decreased in numbers and antileukemic potential at day 30 after HSCT. As a consequence, in an extended series of 99 haplo-HSCT with PT-Cy, we found no significant difference in progression-free survival between patients with or without predicted NK alloreactivity (42% vs 52% at 1 year, P = NS). Our data suggest that the majority of mature NK cells infused with unmanipulated grafts are lost upon PT-Cy administration, blunting NK cell alloreactivity in this transplantation setting.

Low-dose post-transplant cyclophosphamide can mitigate GVHD and enhance the G-CSF/ATG induced GVHD protective activity and improve haploidentical transplant outcomes

Use of high-dose, post-transplant cyclophosphamide (PTCy) results in low rates of graft-versus-host-disease (GVHD) and favorable immune reconstitution, although with higher rates of relapse and somewhat high rates of graft failure. We hypothesized that permissible dose reduction of PTCy might be feasible. The current study attempts to establish a murine model and focus on regulatory T cells (Tregs) to clarify the immunological mechanisms for GVHD prevention by low-dose PTCy. In addition, a prospective, clinical cohort study in haploidentical, T-cell replete transplantation is initiated to support the rational. We found that acute GVHD could be alleviated by low-dose PTCy and could be further mitigated after the combined use of low-dose PTCy and antithymocyte globulin (ATG) in mice. Flow-cytometric analyses in mice showed that low-dose PTCy could increase the number of Tregs and the effect on Tregs is significantly prominent with the combined use of low-dose PTCy and ATG. In the clinical cohort study, the cumulative incidence of grades II-IV acute GVHD in combined treatment cohort with low-dose PTCy and ATG/granulocyte colony-stimulating factor (G-CSF) (17%; 95% CI, 5-29%) was significantly lower than both that in matched-pair cohort (33%; 95% CI, 25-41%; P = 0.04) and that in historical cohort (56%; 95% CI, 42-70%; P < 0.001). In-vivo immune reconstitution analysis showed that low-dose PTCy could facilitate suppressive Tregs reconstitution. In conclusion, low-dose PTCy is sufficient for GVHD abrogation under lymphopenic situation and can enhance the protective effect of ATG/G-CSF on GVHD. Intensified conditioning followed by low-dose PTCy might be a feasible option for patients undergoing haploidentical transplantation.

Haploidentical hematopoietic cell transplantation for adult acute myeloid leukemia: a position statement from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Allogeneic blood or marrow hematopoietic cell transplantation continues to be the most potent anti-leukemic treatment for adult patients with standard, high-risk, or chemo-refractory acute myeloid leukemia. Until recently, this procedure was generally limited to those recipients who had an available matched-sibling donor or matched-unrelated donor. Technical advances in graft cell processing and manipulation, control of bidirectional T cell alloreactivity, graft-versus-host disease prophylaxis, and other supportive measures in haploidentical transplantation now enable nearly all patients with acute myeloid leukemia to benefit from the graft-versus-leukemia effect with substantial reduction in procedure-related mortality. Over recent years, haploidentical donors have been increasingly adopted as a valid donor source in allogeneic hematopoietic cell transplantation for acute myeloid leukemia in the absence of an HLA-matched donor. Among centers of the European Society for Blood and Marrow Transplantation, the use of haploidentical related donor transplantation has increased by 250% since 2010, and 291% since 2005. On behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, we summarize recent utilization trends in haploidentical transplantation for acute myeloid leukemia and describe the transformative changes in haploidentical hematopoietic cell transplantation techniques over the past decade, which have led to the current widespread use of this procedure. Furthermore, we review the efficacy of haploidentical hematopoietic cell transplantation for acute myeloid leukemia from available studies, including preliminary comparative studies, and bring attention to remaining unanswered questions and directions for future research. We conclude this report with our recommendations for the role of haploidentical hematopoietic cell transplantation in acute myeloid leukemia.

Idarubicin-intensified haploidentical HSCT with GvHD prophylaxis of ATG and basiliximab provides comparable results to sibling donors in high-risk acute leukemia

We designed a novel haploidentical hematopoietic stem cell transplantation (haplo-HSCT) system using idarubicin (IDA) intensified conditioning regimens and combination of antithymocyte globulin and basiliximab for GvHD prophylaxis. The outcomes of 110 high-risk acute leukemia patients undergoing haplo-HSCT were compared with 69 contemporaneous high-risk patients receiving HLA-matched sibling transplantation using uniform IDA-intensified regimens. The relapse incidence of haplo-HSCT was 23.4%, and 3-year overall survival (OS) and disease-free survival (DFS) achieved 62.9%, 59.1%, respectively. The cumulative incidences of II-IV and III-IV aGvHD were 28.6 and 14.3%, while limited and extensive cGvHD were 19.4, 13.8%. All these results were equivalent to those of concurrent identical sibling transplantation. Three-year OS and DFS for patients in advance stage reached 48.5, 47.3%. Furthermore, the relapse, 3-year OS of positive minimal residual disease (MRD) patients did not differ from negative MRD patients (18.9% vs 11.5%, 63.6% vs 69.6%), indicating our intensified haplo-HSCT technique could circumvent the dismal prognosis of MRD. These data provide reinforcing evidence that our haplo-HSCT system could dramatically improve the survival of high-risk acute leukemia with low relapse and acceptable transplantation-related mortality, and might be a promising therapeutic option for high-risk patients.

Role of major histocompatibility complex variation in graft-versus-host disease after hematopoietic cell transplantation

Graft-versus-host disease (GVHD) remains a significant potentially life-threatening complication of allogeneic hematopoietic cell transplantation (HCT). Since the discovery of the human leukocyte antigen (HLA) system over 50 years ago, significant advances have clarified the nature of HLA variation between transplant recipients and donors as a chief etiology of GVHD. New information on coding and non-coding gene variation and GVHD risk provides clinicians with options to consider selected mismatched donors when matched donors are not available. These advances have increased the availability of unrelated donors for patients in need of a transplant and have lowered the overall morbidity and mortality of HCT.

Related haploidentical donors are a better choice than matched unrelated donors: Counterpoint

Publisher's Note: This article has a companion Point by Fuchs. Publisher's Note: Join in the discussion of these articles at Blood Advances Community Conversations.

Anti-thymocyte globulin as graft-versus-host disease prevention in the setting of allogeneic peripheral blood stem cell transplantation: a review from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Allogeneic hematopoietic stem cell transplantation is increasingly used as treatment for patients with life-threatening blood diseases. Its curative potential is largely based on immune-mediated graft-versus-leukemia effects caused by donor T cells contained in the graft. Unfortunately, donor T cells are also the cause of graft-versus-host disease. The vast majority of human leukocyte antigen-matched allogeneic hematopoietic stem cell transplants are nowadays carried out with peripheral blood stem cells as the stem cell source. In comparison with bone marrows, peripheral blood stem cells contain more hematopoietic stem/progenitor cells but also one log more T cells. Consequently, the use of peripheral blood stem cells instead of bone marrow has been associated with faster hematologic recovery and a lower risk of relapse in patients with advanced disease, but also with a higher incidence of chronic graft-versus-host disease. These observations have been the basis for several studies aimed at assessing the impact of immunoregulation with anti-thymocyte globulin on transplantation outcomes in patients given human leukocyte antigen-matched peripheral blood stem cells from related or unrelated donors. After a brief introduction on anti-thymocyte globulin, this article reviews recent studies assessing the impact of anti-thymocyte globulin on transplantation outcomes in patients given peripheral blood stem cells from human leukocyte antigen-matched related or unrelated donors as well as in recipients of grafts from human leukocyte antigen haploidentical donors.

Higher dose of CD34+ peripheral blood stem cells is associated with better survival after haploidentical stem cell transplantation in pediatric patients

Haploidentical stem cell transplantation (SCT) is increasingly used to treat pediatric patients with malignant or nonmalignant hematological disorders. The CD34+ dose of bone marrow or peripheral blood stem cells (PBSCs) has been shown to be an important determinant of the transplant outcome in adults under various preparative regimens. However, knowledge of the effect of the CD34+ dose in pediatric haploidentical SCT is limited. We analyzed the data of 348 pediatric patients (aged 2-18 years) with acute or chronic leukemia, myelodysplastic syndrome (MDS), and other hematological disorders that received a transplant between 2002 and 2012. The results of multivariate analysis showed that PBSC CD34+ counts greater than 1.01 × 10⁶  kg^-1 improved platelet engraftment, improved overall survival, and reduced nonrelapse mortality. In contrast, a higher PBSC CD34+ dose did not affect the incidence of acute or chronic graft-versus-host disease, including engraftment syndrome. These data suggest that a PBSC CD34+ dose greater than 1.01 × 10⁶  kg^-1 is optimal for pediatric haploidentical SCT.

Human Herpesvirus 6 replication predicts Cytomegalovirus reactivation after allogeneic stem cell transplantation from haploidentical donor

BACKGROUND AND OBJECTIVES

Since HHV-6 reactivation after transplant has been reported to increase the risk of CMV infection, we tested this hypothesis in the HLA-haploidentical hematopoietic stem cell transplantation setting.

STUDY DESIGN

From February 2011 to October 2015, 75 patients received hematopoietic stem cell transplantation using a T-cell replete graft from a HLA-haploidentical donor at our Institution.

RESULTS

Interestingly, 87% of HHV-6 reactivations were followed by a CMV reactivation, at a median of 15days between the two viruses. Incidence of CMV reactivation was 14.5-fold higher in those patients with prior HHV-6 reactivation vs. those without it (p-value<0.001).

CONCLUSION

The present results suggest that HHV-6 can be considered as a predicting indicator of cellular immunosuppression preceding the onset of CMV infection.

Improved clinical outcomes of rhG-CSF-mobilized blood and marrow haploidentical transplantation compared to propensity score-matched rhG-CSF-primed peripheral blood stem cell haploidentical transplantation: a multicenter study

The effects of haploidentical rhG-CSF-mobilized blood and marrow transplantation (HBMT) on hematological malignances are well established. Previous prospective single-center studies have demonstrated better survival after HBMT versus haploidentical rhG-CSF-mobilized peripheral blood stem cell transplantation (HPBSCT) for acute leukemia (AL) not in remission (NR) or in more than the second complete remission (>CR2). To test the hypothesis that HBMT is still superior to HPBSCT for patients with AL, multiple myeloma (MM), or non-Hodgkin lymphoma (NHL) in CR1/CR2 and for patients with chronic myeloid leukemia in the first and second chronic phase lacking a matched donor, we designed a propensity score method-based multicenter study. Hematopoietic recovery, acute graft-versus-host disease (aGVHD), and chronic GVHD were comparable between the HBMT group (n=168) and the HPBSCT group (n=42). No significant differences were found in non-relapse mortality rate (20.17%±3.58% and 27.24%±7.16%, P=0.18) or relapse rate (19.96%±3.72% and 28.49%±8.25%, P=0.32) between the HBMT group and the HPBSCT group. HBMT recipients had better overall survival (65.0%±4.2% and 54.2%±8.3%, P=0.037) and disease-free survival (59.9%±4.6% and 44.3%±8.7%, P=0.051). Multivariate analysis showed that HPBSCT was associated with poorer DFS (HR (95%CI), 1.639 (0.995-2.699), P=0.052). Our comparisons showed that HBMT was superior to HPBSCT as a post-remission treatment for patients lacking an identical donor.

Novel approaches for preventing acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (alloHSCT) offers potential curative treatment for a wide range of malignant and nonmalignant hematological disorders. However, its success may be limited by post-transplant acute graft-versus-host disease (aGVHD), a systemic syndrome in which donor's immune cells attack healthy tissues in the immunocompromised host. aGVHD is one of the main causes of morbidity and mortality after alloHSCT. Despite standard GVHD prophylaxis regimens, aGVHD still develops in approximately 40-60% of alloHSCT recipients.

AREAS COVERED

In this review, after a brief summary of current knowledge on the pathogenesis of aGVHD, the authors review the current combination of a calcineurin inhibitor with an antimetabolite with or without added anti-thymocyte globulin (ATG) and emerging strategies for GVHD prevention.

EXPERT OPINION

A new understanding of the involvement of cytokines, intracellular signaling pathways, epigenetics and immunoregulatory cells in GVHD pathogenesis will lead to new standards for aGVHD prophylaxis allowing better prevention of severe aGVHD without affecting graft-versus-tumor effects.