Second Hematopoietic Stem Cell Transplant for Thalassemia Major: Improved Clinical Outcomes with a Treosulfan-Based Conditioning Regimen

Metformin pretreatment ameliorates busulfan-induced liver endothelial toxicity during haematopoietic stem cell transplantation

The success of Haematopoietic cell transplantation (HCT) is often limited by regimen-related toxicity (RRT) caused by conditioning regimen drugs. Among different conditioning drugs, busulfan (Bu) and treosulfan (Treo), although widely used in HCT, exhibit different toxicity profiles, the mechanism of which is still unclear. Here we investigated the effects of Bu and Treo in endothelial cells. While both Bu and Treo induced DNA damage in endothelial cells, we observed Bu alone to induce oxidative stress and sustained activation of phospho-ERK1/2, leading to apoptosis. However, Treo-treated cells exhibited no oxidative stress/apoptosis of endothelial cells. Screening of pharmacological inhibitors of both ROS and p-ERK revealed that metformin effectively ameliorates Bu-mediated toxicity in endothelial cells. In Balb/c mice, we observed a significant reduction in bone marrow endothelial cells in Bu-treated mice compared to Treo-treated mice. Further, liver sinusoidal endothelial cells (LSEC) was damaged by Bu, which is implicated in liver vasculature and their functional capacity to uptake FITC-albumin. However, Treo-treated mice liver vasculature was morphologically and functionally normal. When mice were pretreated with metformin followed by Bu, LSECs damage was ameliorated morphologically and functionally. Bone marrow transplants done on these mice did not affect the engraftment of donor cells.

TCRαβ/CD19 depleted HSCT from an HLA-haploidentical relative to treat children with different non-malignant disorders

Several non-malignant disorders (NMDs), either inherited or acquired, can be cured by allogeneic hematopoietic stem cell transplantation (HSCT). Between January 2012 and April 2020, 70 consecutive children affected by primary immunodeficiencies, inherited/acquired bone marrow failure syndromes, red blood cell disorders or metabolic diseases, lacking a fully-matched donor or requiring urgent transplantation, underwent TCRαβ/CD19-depleted haploidentical HSCT from an HLA-partially matched relative as part of a prospective study (#NCT01810120). Median age at transplant was 3.5 years (range 0.3-16.1); median time from diagnosis to transplant was 10.5 months (2.7 for SCID patients). Primary engraftment was obtained in 51 patients, while 19 and 2 patients experienced either primary or secondary graft failure (GF), the overall incidence of this complication being 30.4%. Most GFs were observed in children with disease at risk for this complication (e.g., aplastic anemia, thalassemia). All but 5 patients experiencing GF were successfully retransplanted. Six patients died of infectious complications (4 had active/recent infections at time of HSCT), the cumulative incidence of transplant-related mortality (TRM) being 8.5%. Cumulative incidence of grade I-II acute GvHD was 14.4% (no patient developed grade III-IV acute GVHD). Only one patient at risk developed mild chronic GvHD. With a median follow-up of 3.5 years, the 5-year probability of overall and disease-free survival was 91.4% and 86.8%, respectively. In conclusion, TCRαβ/CD19-depleted haploidentical HSCT from an HLA-partially matched relative is confirmed to be an effective treatment for children with NMDs. Prompt donor availability, low incidence of GvHD and TRM make this strategy an attractive option in NMDs patients.

Repeated CD45RA-depleted DLI successfully increases donor chimerism in a patient with beta-thalassemia major after haploidentical stem cell transplant

Allogeneic hematopoietic stem cell transplantation is curative for transfusion-dependent thalassemia, but mixed chimerism (MC) may herald graft rejection. We report a child who failed bone marrow transplant (BMT) from matched unrelated donor (MUD) successfully salvaged with haploidentical peripheral blood stem cell transplant (PBSCT), but had MC in T-lymphocyte compartment despite near-complete donor chimerism in myeloid compartment. MC was successfully improved by repeated CD45RA-depleted donor lymphocyte infusion (DLI). A 2-year-old Chinese girl with beta-thalassemia major underwent 12/12-MUD BMT with HU/AZA/Cy/Flu/Bu/TT conditioning resulted in graft rejection. As donor refused second donation, rescue haploidentical PBSCT was performed with alemtuzumab/fludarabine/treosulfan conditioning. Harvest product was CD3/CD45RA depleted with extra products cryopreserved. Split cell chimerism performed 1-month after haplo-transplant showed 97% mother, 3% MUD, and 0% host for granulocytes but 38% mother, 62% MUD, and 0% host for CD3 + T cells. In view of low haploidentical donor chimerism in T-lymphocyte compartment, CD45RA-depleted DLI using cryopreserved product was performed on day + 38, after thymoglobulin 3 mg/kg given as T-cell depletion 3 days beforehand. T-cell chimerism improved to 51% mother and 49% MUD post-DLI. Second cryopreserved CD45RA-depleted DLI was given 17 days after the first DLI (day + 55), and 100% full chimerism of mother's T cells was gradually established without significant graft-versus-host disease (GVHD) or viral reactivation. To conclude, split lineage chimerism determination is beneficial to guide management strategy. For MC in T-cell compartment, CD45RA-depleted DLI is a potential alternative to unselected T cells as it carries lower risk of GVHD and infection.

Comparison of Hematopoietic Stem Cell Transplantation Results in Patients with β-Thalassemia Major from Three Different Graft Types

Allogeneic hematopoietic stem cell transplantation (HSCT) is the curative therapy for β-thalassemias that induces severe life-threatening complications. The human leukocyte antigen (HLA) registries and umbilical cord blood banks have carried out diligent searches to find matched unrelated donors (MUDs) for about 70.0% of patients from 2000 onwards. The chance of finding a non-sibling fully matched family donors is higher in some ethnic groups in which consanguineous marriages are common. We have studied and compared transplant complications and outcomes in different graft types (sibling, non-sibling family and unrelated). The non-sibling matched family donor (MFD) group consisted of four mothers, three fathers, five cousins, one paternal uncle and one paternal aunt. There was no significant difference in the mean transfused CD34+ cells, engraftment, median days of neutrophil and platelet recovery were achieved (p > 0.05). The distribution of postttransplant complication did not show any significant difference between groups (p > 0.05). In univariate analysis and multivarite analyses, age, gender, Pesaro risk group (I-II vs. III) and ABO incompatibilty demonstrated a significant difference in disease free survival (p < 0.05). Furthermore, in the second step of investigating overall survival (OS), age, gender and Pesaro risk group (I-II vs. III) showed a significant difference (p < 0.05). There was no significant difference in transplant-related mortality (TRM) between groups. Non-sibling related donor transplants are important for populations where consanguineous marriages are common. Transplant groups according to graft type had similar thalassemia-free survival (TFS) and OS when using a treosulfan-based regimen in our study.

Non-myeloablative matched sibling stem cell transplantation with the optional reinforced stem cell infusion for patients with hemoglobinopathies

BACKGROUND

The NIH protocol for non-myeloablative (NMA) conditioning allogeneic stem cell transplantation (alloSCT) with alemtuzumab and low-dose total body irradiation corrected the abnormal sickle cell disease (SCD) phenotype without the risk of graft-versus-host disease. However, alloSCT using NMA conditioning had been rarely applied to β-thalassemia major (β-TM) patients.

METHODS

To avoid prolonged immunosuppression, we developed a two-stage strategy. Mixed donor chimerism was initially achieved using the protocol developed by the NIH protocol. Thereafter, we facilitated donor chimerism using the optional reinforced stem cell (SC) infusion in cases requiring protracted immunosuppression or experiencing impending graft failure.

RESULTS

In this study, β-TM (n = 9) and SCD (n = 4) patients were equally effectively treated with eradicating the abnormal hemoglobin phenotype. Five patients, including four β-TM, achieved stable mixed chimerism without receiving optional reinforced SC infusion. All patients that received optional reinforced infusion achieved complete (n = 4) or mixed chimerism (n = 1). The overall survival rate and event-free survival at 4 years were 91.7% (95% CI; 53.9-98.8) in both groups, with a thalassemia-free survival rate in β-TM patients of 87.5% (95% CI; 38.7-98.1).

CONCLUSION

This study is the first to report successful NMA conditioning alloSCT to achieve stable mixed chimerism correcting the abnormal hemoglobin phenotype in adult β-TM patients.