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

Abstract

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 celldepleted 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. (Blood. 2016;128(23):2616-2623 Allogeneic hematopoietic stem cell transplantation is the most powerful therapy for high-risk acute leukemia.1 Donor T cells recognize host alloantigens on leukemic cells and eradicate leukemia (graftversus-leukemia [GVL] effect). They also attack nonhematopoietic tissues (such as skin, gut, and liver) and thus mediate graft-versus-host disease (GVHD), a major cause of morbidity and mortality. Matching donor and recipient human leukocyte antigens (HLA) is considered crucial for optimal transplant outcomes with acceptable nonrelapse mortality (NRM).1 However, only 25% of individuals have an HLAidentical sibling who could serve as donor. Alternative stem cell sources (which of course carry increased risk of NRM due to diverse combinations of graft failure, GVHD, veno-occlusive disease, and infections) are matched unrelated volunteers, unrelated umbilical cord blood, and HLA haplotype mismatched ("haploidentical") family members.1,2 In fact, recent years have witnessed tremendous progress in the field of haploidentical transplantation. 3-10The experience of T cell-depleted haploidentical transplantation and the discovery of donor features that improve outcomesHaploidentical transplantation has become a widely used treatment of patients without a matched donor.2-15 Indeed, a haploidentical donor is immediately available in the family for almost all patients, without delay due to registry search. Because of multiple class I and II HLA disparities between donor and recipient, T cell-mediated hostversus-graft and graft-versus-host alloresponses (leading, ...

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

“…HaploHCT has the potential to fill a substantial therapeutic gap for these patients without a matched related or unrelated donor. Several retrospective studies have compared haploHCT to HLA‐matched allogeneic HCT for de novo AML but not in sAML …”

“…Initial experiences with haploHCT in the 1990s resulted in poor outcomes due to T‐cell alloreactivity secondary to HLA‐mismatches with delayed engraftment, graft failures, and relatively high incidences of acute GVHD . Several strategies were developed to overcome these challenges, including ex vivo and in vivo TCD as well as T‐cell replete (TCR) grafts .…”

“…Several strategies were developed to overcome these challenges, including ex vivo and in vivo TCD as well as T‐cell replete (TCR) grafts . In vivo TCD with ATG has become a commonly used practice for GVHD prophylaxis in haploHCT, especially in China, with improvement in achieving primary engraftment, reducing RI, and minimizing GVHD . However, in vivo TCD is known to be associated with a high incidence of infection and NRM leading to increased morbidity and mortality .…”

Outcome of children with acute leukemia given HLA-haploidentical HSCT after αβ T-cell and B-cell depletion

“…[1][2][3] In order to remove T cells, responsible for graft-versus-host disease (GVHD), and B cells, from which posttransplant lymphoproliferative disease (PTLD) can arise, 4 positive selection of CD34 1 hematopoietic stem cells (HSCs) has been employed for many years in haplo-HSCT. [1][2][3] Although the administration of CD34…”

Natural Killer Cell-Based Cancer Immunotherapies: From Immune Evasion to Promising Targeted Cellular Therapies

“…Evidence for the anticancer efficacy of NK cells comes from allogeneic or haploidentical hematopoietic stem cell (HSC) transplantations that have been used in combination with chemotherapy in the treatment of different forms of leukemia (9). This has shown that NK cells formed from the transplant not only are efficient in killing of allogeneic leukemia cells but are also instrumental in reducing the incidence of graft versus host disease due to their killing activity for dendritic cells (10).…”