Low-dose antithymocyte globulin inhibits chronic graft-versus-host disease in peripheral blood stem cell transplantation from unrelated donors

HLA-Haploidentical Peripheral Blood Stem Cell Transplantation with Post-Transplantation Cyclophosphamide versus HLA-Matched Unrelated Donor Transplantation for Myelodysplastic Syndrome

Allogeneic hematopoietic cell transplantation (allo-HCT) is the sole curative therapy for myelodysplastic syndrome (MDS). In the absence of an HLA-matched sibling donor, an HLA-matched unrelated donor (MUD) is considered the leading candidate. However, in recent decades, the alternative donor pool has been extended to HLA-haploidentical donors, especially with the development of graft-versus-host disease (GVHD) prophylaxis using post-transplantation cyclophosphamide (PTCy). Comparative data for haploidentical and MUD allo-HCT in patients with MDS are scarce. We retrospectively analyzed 697 adult patients with MDS who underwent HLA-haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) with PTCy (n = 136), MUD bone marrow transplantation (MUD-BMT) (n = 465), or MUD peripheral blood stem cell transplantation (MUD-PBSCT) (n = 96) as their first allo-HCT between 2014 and 2020 using Japanese registry data. Multivariable analyses demonstrated faster neutrophil engraftment (hazard ratio [HR], 2.19; 95% confidence interval [CI], 1.65 to 2.90; P < .001) and platelet engraftment (HR, 2.31; 95% CI, 1.72 to 3.10; P < 0001) in the MUD-PBSCT cohort compared with the haplo-PBSCT cohort. MUD-BMT was associated with a higher incidence of grade II-IV acute GVHD than haplo-PBSCT (HR, 1.52; 95% CI, 1.00 to 2.29; P = .048). Among patients without in vivo T cell depletion using antithymocyte globulin (ATG) (haplo-PBSCT, n = 136; MUD-BMT, n = 446; MUD-PBSCT, n = 65), MUD-PBSCT recipients experienced faster hematopoietic recovery, MUD-BMT recipients (HR, 1.54; 95% CI, 1.02 to 2.32; P = .042) or MUD-PBSCT recipients (HR, 1.83; 95% CI, 1.06 to 3.18; P = .03) had a higher incidence of grade II-IV acute GVHD, and MUD-PBSCT recipients developed chronic GVHD more frequently than haplo-PBSCT recipients (HR, 1.74; 95% CI, 1.04 to 2.89; P = .034). There were no significant differences in overall survival, disease-free survival, GVHD-free relapse-free survival, relapse, or nonrelapse mortality in the haplo-PBSCT cohort versus the MUD-BMT or MUD-PBSCT cohorts. In conclusion, despite differences in the incidences of hematopoietic engraftment and GVHD depending on graft type and ATG use in MUD transplant recipients, major transplantation outcomes were comparable between recipients of haplo-PBSCT using PTCy and recipients of MUD-BMT or MUD-PBSCT.

Different effects of thymoglobulin on acute leukemia with pre-transplant residual blasts in HLA mismatch transplantation

Anti-thymocyte globulin (ATG) is widely used to reduce acute and chronic graft-versus-host disease (a/cGVHD), one of the leading causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). As the removal of alloreactive T cells by ATG may also reduce the graft-versus-leukemia effect, the question of whether ATG use affects relapse incidence and survival outcomes in acute leukemia patients with pre-transplant bone marrow residual blasts (PRB) remains controversial. Here, we evaluated the impact of ATG on transplant outcomes in acute leukemia patients with PRB (n = 994) who underwent HSCT from HLA 1-allele mismatched unrelated donors (MMUD) or HLA 1-antigen mismatched related donors (MMRD). In MMUD with PRB (n = 560), multivariate analysis demonstrated that ATG use significantly decreased grade II-IV aGVHD (hazard ratio [HR], 0.474; P = 0.007) and non-relapse mortality (HR, 0.414; P = 0.029) and marginally improved extensive cGVHD (HR, 0.321; P = 0.054) and GVHD-free/relapse-free survival (HR, 0.750; P = 0.069). We concluded that ATG had different effects on transplant outcomes using MMRD and MMUD, and its use would be beneficial to decrease a/cGVHD without increasing non-relapse mortality and relapse incidence in acute leukemia patients with PRB following HSCT from MMUD.

Controversies and expectations for the prevention of GVHD: A biological and clinical perspective

Severe acute and chronic graft versus host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation. Historically, cord blood and matched sibling transplantation has been associated with the lowest rates of GVHD. Newer methods have modified the lymphocyte components to minimize alloimmunity, including: anti-thymocyte globulin, post-transplant cyclophosphamide, alpha/beta T cell depletion, and abatacept. These agents have shown promise in reducing severe GVHD, however, can be associated with increased risks of relapse, graft failure, infections, and delayed immune reconstitution. Nonetheless, these GVHD prophylaxis strategies have permitted expansion of donor sources, especially critical for those of non-Caucasian decent who previously lacked transplant options. This review will focus on the biologic mechanisms driving GVHD, the method by which each agent impacts these activated pathways, and the clinical consequences of these modern prophylaxis approaches. In addition, emerging novel targeted strategies will be described. These GVHD prophylaxis approaches have revolutionized our ability to increase access to transplant and have provided important insights into the biology of GVHD and immune reconstitution.

Advantages of peripheral blood stem cells from unrelated donors versus bone marrow transplants in outcomes of adult acute myeloid leukemia patients

BACKGROUND AIMS

In allogeneic stem cell transplantation, unrelated donors are chosen in cases where appropriate related donors are not available. Peripheral blood stem cells (PBSCs) are more often selected as a graft source than bone marrow (BM). However, the prognostic benefits of PBSCs versus BM transplants from unrelated donors have not been carefully examined in patients with acute myeloid leukemia (AML). This study compared outcomes of adult AML patients who underwent unrelated PBSC and BM transplantation, evaluating post-transplant complications, including engraftment, graft-versus-host disease (GVHD) and infections, and determined subgroups of patients who are most likely to benefit from unrelated PBSCs compared with BM transplants.

METHODS

The authors analyzed 2962 adult AML patients who underwent unrelated PBSC or BM transplants between 2011 and 2018 (221 PBSC and 2741 BM) using the Japanese nationwide registry database, in which graft source selection is not skewed toward PBSCs.

RESULTS

In 49.7% of patients, disease status at transplantation was first complete remission (CR1). In 57.1% of cases, HLA-matched donors were selected. Myeloablative conditioning was performed in 75.1% of cases, and anti-thymocyte globulin (ATG) was added to conditioning in 10.5%. Multivariate analyses showed a trend toward favorable non-relapse mortality (NRM) in PBSC recipients compared with BM recipients (hazard ratio [HR], 0.731, P = 0.096), whereas overall survival (OS) (HR, 0.959, P = 0.230) and disease-free survival (DFS) (HR, 0.868, P = 0.221) were comparable between PBSC and BM recipients. Although the rate of chronic GVHD (cGVHD) was significantly higher in PBSC patients (HR, 1.367, P = 0.016), NRM was not increased, mainly as a result of significantly reduced risk of bacterial infections (HR, 0.618, P = 0.010), reflecting more prompt engraftments in PBSC recipients. Subgroup analyses revealed that PBSC transplantation was advantageous in patients transplanted at CR1 and in those without ATG use. PBSC recipients experienced significantly better OS and/or DFS compared with BM recipients in this patient group.

CONCLUSIONS

The authors' results confirmed the overall safety of unrelated PBSC transplantation for adult AML patients and suggested an advantage of PBSCs, especially for those in CR1. Further optimization of the prophylactic strategy for cGVHD is required to improve the overall outcome in transplantation from unrelated PBSC donors.

Graft-Versus-Host Disease Prophylaxis Using Low-Dose Antithymocyte Globulin in Peripheral Blood Stem Cell Transplantation-A Matched-Pair Analysis

Antithymocyte globulin (ATG) decreases chronic graft-versus-host disease (cGVHD) in peripheral blood stem cell transplantation (PBSCT); however, the optimal ATG dose has not been elucidated. We conducted a matched-pair analysis to evaluate whether low-dose ATG could inhibit cGVHD in HLA-matched PBSCT after myeloablative conditioning. A total of 70 patients who were enrolled in the JSCT-ATG15 study, a multicenter phase II clinical trial of 2 mg/kg of ATG (thymoglobulin) given on days -2 and -1, were compared with 210 patients not receiving ATG, who were matched for age, sex, disease, and calcineurin inhibitor selected from the database in Japan. The primary endpoint, cumulative incidence of extensive cGVHD at 2 years was significantly less in the ATG group than that in the non-ATG group (8.7% [95% CI, 3.5%-16.8%] versus 26.2% [95% CI, 20.3%-32.5%], P = .002). ATG significantly reduced the incidence of overall cGVHD and inhibited multiple organ involvement. The ATG group had favorable outcome compared to the non-ATG group in GVHD-free, and relapse-free survival at 2 years. In conclusion, low-dose ATG effectively inhibits chronic GVHD in PBSCT.