Conditioning regimens in allo-SCT for thalassemia major

Hematopoietic Stem Cell Transplantation in Thalassemia

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only consolidated, potentially curative treatment for patients with transfusion-dependent thalassemia major. In the past few decades, several new approaches have reduced the toxicity of conditioning regimens and decreased the incidence of graft-versus-host disease, improving patients' outcomes and quality of life. In addition, the progressive availability of alternative stem cell sources from unrelated or haploidentical donors or umbilical cord blood has made HSCT a feasible option for an increasing number of subjects lacking an human leukocyte antigen (HLA)-identical sibling. This review provides an overview of allogeneic hematopoietic stem cell transplantation in thalassemia, reassesses current clinical results, and discusses future perspectives.

Curative therapy for hemoglobinopathies: an International Society for Cell & Gene Therapy Stem Cell Engineering Committee review comparing outcomes, accessibility and cost of ex vivo stem cell gene therapy versus allogeneic hematopoietic stem cell transplantation

Thalassemia and sickle cell disease (SCD) are the most common monogenic diseases in the world and represent a growing global health burden. Management is limited by a paucity of disease-modifying therapies; however, allogeneic hematopoietic stem cell transplantation (HSCT) and autologous HSCT after genetic modification offer patients a curative option. Allogeneic HSCT is limited by donor selection, morbidity and mortality from transplant conditioning, graft-versus-host disease and graft rejection, whereas significant concerns regarding long-term safety, efficacy and cost limit the broad applicability of gene therapy. Here the authors review current outcomes in allogeneic and autologous HSCT for transfusion-dependent thalassemia and SCD and provide our perspective on issues surrounding accessibility and costs as barriers to offering curative therapy to patients with hereditary hemoglobinopathies.

Effect of increased dose of total body irradiation on graft failure associated with HLA-haploidentical transplantation in patients with severe haemoglobinopathies: a prospective clinical trial

BACKGROUND

Although severe haemoglobinopathies can be cured with allogeneic blood or bone marrow transplantation, availability of matched donors and toxic effects can be problematic. We previously found that non-myeloablative haploidentical related bone marrow transplantation with post-transplantation cyclophosphamide expanded the donor pool while limiting graft-versus-host disease (GVHD). However, graft failure-albeit with full host haemopoietic recovery-occurred in 50% of patients. In this study, we investigated whether increasing total body irradiation from 200 cGy to 400 cGy would improve engraftment while maintaining the safety profile.

METHODS

This study was done at Johns Hopkins Hospital (Baltimore, MD, USA). Patients aged 2-70 years receiving their first bone marrow transplant were eligible for inclusion in the study. Patients received rabbit-derived intravenous anti-thymocyte globulin 0·5 mg/kg on day -9 and 2 mg/kg on days -8 and -7, intravenous fludarabine 30 mg/m² on days -6 to -2, intravenous cyclophosphamide 14·5 mg/kg on days -6 and -5, and total body irradiation 400 cGy administered as a single fraction on day -1. We collected unmanipulated bone marrow and infused on day 0. GVHD prophylaxis comprised intravenous cyclophosphamide 50 mg/kg per day on days 3 and 4 after transplantation, oral mycophenolate mofetil 15 mg/kg per dose (maximum 1 g) every 8 h on days 5 to 35, and oral sirolimus to maintain a level of 5-15 ng/dL for at least 1 year starting on day 5. The original planned primary objectives of this phase 2 clinical trial were transplant-related mortality and progression-free survival. However, the coverage decision by the Centers for Medicare and Medicaid Services to only provide payment for allogeneic bone marrow transplantation for patients with sickle cell disease on a clinical trial that had a comparison arm with patients not receiving bone marrow transplantation prompted the closure of this trial to accrual in 2017. Therefore, as we were unable to perform our planned statistical analysis, the primary objective was modified to evaluate engraftment, assessed by chimerism. This trial is registered with ClinicalTrials.gov, number NCT00489281. The study is closed to new participants and this is the primary analysis.

FINDINGS

Between Sept 24, 2014, and Aug 1, 2017, we enrolled 17 consecutive patients: 12 (71%) with sickle cell disease and 5 (29%) with β-thalassaemia major. The median patient age was 16 years (range 6-31, IQR 7·7-27·5). One (6%) of 17 patients had primary graft failure with recovery of host haemopoiesis. 13 (76%) of 17 patients achieved full donor chimerism and three (18%) had mixed donor-host chimerism. Five (29%) of 17 patients developed grade 2-4 acute GVHD, including four (24%) with maximal grade 2 GVHD and one (6%) with grade 3 GVHD. Chronic GVHD developed in three (18%) patients. As of their last follow-up visit, GVHD had resolved in all patients and no patients were receiving systemic GVHD therapy. All patients remained alive as of Aug 4, 2019, and the median follow-up duration was 705 days (range 355-1294; IQR 398-943). Only one (6%) of the 16 engrafted patients remained transfusion dependent, and 14 (88%) discontinued immunosuppression.

INTERPRETATION

Increasing total body irradiation to 400 cGy substantially reduced graft failure while maintaining the safety of haploidentical bone marrow transplantation with post-transplantation cyclophosphamide. These results suggest that engraftment after haploidentical bone marrow transplantation for haemoglobinopathies is possible, and primary graft failure-the main problem previously reported-might be addressed by this strategy. Therefore, this curative approach should no longer be restricted to patients with HLA-matched donors.

FUNDING

Maryland Stem Cell Research Fund and US National Institutes of Health.

Impact of low-dose irradiation and in vivo T-cell depletion on hematopoietic stem cell transplantation for non-malignant diseases using fludarabine-based reduced-intensity conditioning

Reduced-intensity conditioning is widely used with hematopoietic stem cell transplantation for non-malignant diseases: however, the optimal conditioning to ensure stable engraftment has not been established. In this study, we retrospectively compared the impact of low-dose (1-6 Gy) irradiation and in vivo T-cell depletion on the clinical outcome of 523 patients with non-malignant disease who underwent a first allogeneic hematopoietic stem cell transplantation using fludarabine-based reduced-intensity conditioning. Use of low-dose irradiation, but not of anti-thymocyte globulin/anti-lymphocyte globulin, showed a beneficial effect on overall survival (adjusted hazard ratio: 0.56; 95% confidence interval: 0.35-0.91, P = 0.018). Furthermore, use of low-dose irradiation was strongly associated with lower transplant-related mortality (adjusted hazard ratio: 0.55; 95% confidence interval: 0.32-0.96, P = 0.034). The addition of low-dose irradiation to the conditioning regimen was beneficial, at least to the short-term clinical outcome. A large prospective study with long-term follow-up is now required to extend these findings and establish the optimal hematopoietic stem cell transplant conditioning for patients with at least some subgroups of non-malignant diseases.

ATG vs thiotepa with busulfan and cyclophosphamide in matched-related bone marrow transplantation for thalassemia

Matched-related bone marrow transplantation (BMT) may cure >80% of low-risk children with severe thalassemia (ST). Very long-term follow-up studies have shown how the standard busulfan-cyclophosphamide (BuCy) regimen may be associated with normalization of health-related quality of life, no second malignancies in the absence of chronic graft-versus-host disease, and fertility preservation in many patients. However, because BuCy may be associated with high rejection rates, some centers incorporate thiotepa (Tt) in busulfan- or treosulfan-based regimens, a combination that may increase the risk of permanent infertility. This study retrospectively compares matched-related BMT outcomes in 2 groups of low-risk ST patients conditioned with either Tt or anti-thymocyte globulin (ATG) in addition to BuCy. A total of 81 consecutive first BMTs were performed in 5 collaborating startup BMT centers in the Indian subcontinent between January 2009 and January 2016; 30 patients were transplanted after conditioning with Tt-BuCy between January 2009 and July 2013, whereas between August 2013 and January 2016, 51 patients received ATG-BuCy. All patients were <15 years and had no hepatomegaly (liver ≤2 cm from costal margin). Actuarial overall survival in the Tt-BuCy and ATG-BuCy groups was 87% and 94% and thalassemia-free survival was 80% and 85% at a median follow-up of 37 and 17 months, respectively, with no significant differences by log-rank statistics. Substituting Tt with ATG in the standard BuCy context seems safe and effective and may decrease transplant-related mortality. Higher fertility rates are expected for patients who received ATG-BuCy.

The Start-Up of the first Hematopoietic Stem Cell Transplantation Center in the Iraqi Kurdistan: a Capacity-Building Cooperative Project by the Hiwa Cancer Hospital, Sulaymaniyah, and the Italian Agency for Development Cooperation: an Innovative Approach

We describe the entire process leading to the start-up of a hematopoietic stem cell transplantation center at the Hiwa Cancer Hospital, in the city of Sulaymaniyah, Kurdistan Iraqi Region. This capacity building project was funded by the Italian Development Cooperation Agency and implemented with the support of the volunteer work of Italian professionals, either physicians, nurses, biologists and technicians. The intervention started in April 2016, was based exclusively on training and coaching on site, that represent a significant innovative approach, and led to a first autologous transplant in June 2016 and to the first allogeneic transplant in October. At the time of reporting, 9 months from the initiation of the project, 18 patients have been transplanted, 15 with an autologous and 3 with an allogeneic graft. The center at the HCH represents the first transplantation center in Kurdistan and the second in wide Iraq. We conclude that international development cooperation may play an important role also in the field of high-technology medicine, and contribute to improved local centers capabilities through country to country scientific exchanges. The methodology to realize this project is innovative, since HSCT experts are brought as volunteers to the center(s) to be started, while traditionally it is the opposite, i.e. the local professionals to be trained are brought to the specialized center(s).

Optimal Outcomes in Young Class 3 Patients With Thalassemia Undergoing HLA-Identical Sibling Bone Marrow Transplantation

BACKGROUND

Bone marrow transplantation (BMT) for class 3 patients with thalassemia is challenging due to high rates of graft rejection and transplant-related mortality. Since the first studies of BMT in the late 1980s, a number of conditioning regimens have been designed to improve outcomes, but with suboptimal results. Here we report the outcome of transplantation in class 3 patients using a modified protocol.

METHODS

Sixty-three patients between 5 and 16.7 years of age with class 3 thalassemia received HLA-matched sibling BMT following either the original protocol (26 patients) or the modified protocol (37 patients). Both regimens comprised preconditioning cytoreduction with hydroxyurea and azathioprine starting at -45 days pretransplant, and fludarabine from days -16 to -12. Conditioning was performed with busulfan and cyclophosphamide (original protocol) or with busulfan, thiotepa, and cyclophosphamide (modified protocol).

RESULTS

The 2 groups showed similar patient demographics. At day 0, the degree of cytoreduction (lymphopenia, neuthropenia, and thrombocytopenia) achieved by the modified protocol was greater than the original protocol. The incidence of graft failure/rejection was significantly higher in the original group (15%; 95% confidence interval [95% CI], 5-32%) compared with the modified group (0%) (P = 0.014). The respective 5-year thalassemia-free survival rates were 73% (95% CI, 51-86%) and 92% (95% CI, 77-97%) (P = 0.047). Both groups showed similar incidences of grades II to IV acute graft-versus host disease. Modified protocol did not increase nonhematological toxicity or infectious complications.

CONCLUSIONS

The modified treatment protocol effectively and safely prevented graft failure/rejection and significantly increased thalassemia-free survival of class 3 patients with thalassemia.

Allogeneic Stem Cell Transplantation in Congenital Hemoglobinopathies Using a Tailored Busulfan-Based Conditioning Regimen: Single-Center Experience

Hematopoietic stem cell transplantation (HSCT) is the only proven curative option for patients with hemoglobinopathies, both thalassemia and sickle cell anemia (SCA). A busulfan-based myeloablative conditioning regimen is the standard of care for HSCT in these patients, although increased treatment-related morbidity, including veno-occlusive disease (VOD), has been demonstrated. Thirty-eight pediatric patients, median age 8 years (range, 6 months to 22 years), suffering from hemoglobinopathy were treated at Rambam Medical Center in Haifa, Israel, between 1998 and 2011. Thirty-four patients had thalassemia major and 4 had SCA. The 38 patients underwent 40 HSCTs, 34 of which were first transplants and 6 second transplants. Most transplants (32/40) were from matched sibling donors. Sources of stem cells were peripheral blood in 30 transplants, bone marrow in 7 transplants, and cord blood in 3 transplants. All received different customized busulfan-based conditioning regimens tailored by pharmacokinetic analysis of busulfan levels. Primary engraftment occurred in 37 of 40 transplants. Neutrophil engraftment (>.5 × 10(9)/L) occurred at a median of 15.3 days post-transplantation (range, 10 to 45). Platelet transfusion independence (>20 × 10(9)/L) occurred at a median of 22.3 days (range, 11 to 60). The rate of 5-year overall survival for thalassemia patients after first transplantation was 90.5% ± 5.3%. The rate of 5-year thalassemia-free survival was 81.7% ± 6.8%. Cumulative incidence of acute graft-versus-host disease (GVHD) was 17.6%. Rate of grades III to IV GVHD was 8.8%. Cumulative incidence of chronic GVHD was 23.5%, with 11.8% incidence of extensive chronic GVHD. One patient developed VOD. Full donor chimerism occurred in 36.4% of patients with class 1 + 2 thalassemia, compared with 78.6% in class 3 thalassemia (P = .049). Overall survival above 90% in patients undergoing their first transplant was demonstrated using busulfan-based conditioning regimens. The low incidence of VOD was probably due to busulfan area under the curve measurements and dose adjustment.

Thalassemia 2016: Modern medicine battles an ancient disease

Thalassemia was first clinically described nearly a century ago and treatment of this widespread genetic disease has greatly advanced during this period. DNA-based diagnosis elucidated the molecular basis of the disease and clarified the variable clinical picture. It also paved the way for modern methods of carrier identification and prevention via DNA-based prenatal diagnosis. Every aspect of supportive care, including safer blood supply, more regular transfusions, specific monitoring of iron overload, parenteral and oral chelation, and other therapies, has prolonged life and improved the quality of life of these patients. Significant advances have also been made in allogenic bone marrow transplantation, the only curative therapy. Recently, there has been a rejuvenated interest in studying thalassemia at the basic science level, leading to the discovery of previously unknown mechanisms leading to anemia and enabling the development of novel therapies. These will potentially improve the treatment of, and possibly cure the disease. Pathways involving activin receptors, heat shock proteins, JAK2 inhibitors and macrophage targeted therapy, among others, are being studied or are currently in clinical trials for treating thalassemia. Novel types of genetic therapies are in use or under investigation. In addition to the challenges of treating each individual patient, the longer survival of thalassemia patients has raised considerations regarding worldwide control of thalassemia, since prevention is not universally implemented. This review will trace a number of the original medical milestones of thalassemia diagnosis and treatment, as well as some of the most recent developments which may lead to innovative therapeutic modalities.