TCRαβ CD19 depletion in allogeneic haematopoietic stem cell transplantation performed for Hurler syndrome

Results of a multicenter phase I/II trial of TCRαβ and CD19-depleted haploidentical hematopoietic stem cell transplantation for adult and pediatric patients

Hematopoietic stem cell transplantation (HSCT) from haploidentical donors is a viable option for patients lacking HLA-matched donors. Here we report the results of a prospective multicenter phase I/II trial of transplantation of TCRαβ and CD19-depleted peripheral blood stem cells from haploidentical family donors after a reduced-intensity conditioning with fludarabine, thiotepa, and melphalan. Thirty pediatric and 30 adult patients with acute leukemia (n = 43), myelodysplastic or myeloproliferative syndrome (n = 6), multiple myeloma (n = 1), solid tumors (n = 6), and non-malignant disorders (n = 4) were enrolled. TCR αβ/CD19-depleted grafts prepared decentrally at six manufacturing sites contained a median of 12.1 × 10⁶ CD34⁺ cells/kg and 14.2 × 10³ TCRαβ⁺ T-cells/kg. None of the patients developed grade lll/IV acute graft-versus-host disease (GVHD) and only six patients (10%) had grade II acute GVHD. With a median follow-up of 733 days 36/60 patients are alive. The cumulative incidence of non-relapse mortality at day 100, 1 and 2 years after HSCT was 5%, 15%, and 17% for all patients, respectively. Estimated probabilities of overall and disease-free survival at 2 years were 63% and 50%, respectively. Based on these promising results in a high-risk patient cohort, haploidentical HSCT using TCRαβ/CD19-depleted grafts represents a viable treatment option.

T-Cell-Replete Versus ex vivo T-Cell-Depleted Haploidentical Haematopoietic Stem Cell Transplantation in Children With Acute Lymphoblastic Leukaemia and Other Haematological Malignancies

Allogeneic haematopoietic stem cell transplantation (HSCT) represents a potentially curative option for children with high-risk or refractory/relapsed leukaemias. Traditional donor hierarchy favours a human leukocyte antigen (HLA)-matched sibling donor (MSD) over an HLA-matched unrelated donor (MUD), followed by alternative donors such as haploidentical donors or unrelated cord blood. However, haploidentical HSCT (hHSCT) may be entailed with significant advantages: besides a potentially increased graft-vs.-leukaemia effect, the immediate availability of a relative as well as the possibility of a second donation for additional cellular therapies may impact on outcome. The key question in hHSCT is how, and how deeply, to deplete donor T-cells. More T cells in the graft confer faster immune reconstitution with consecutively lower infection rates, however, greater numbers of T-cells might be associated with higher rates of graft-vs.-host disease (GvHD). Two different methods for reduction of alloreactivity have been established: in vivo T-cell suppression and ex vivo T-cell depletion (TCD). Ex vivo TCD of the graft uses either positive selection or negative depletion of graft cells before infusion. In contrast, T-cell-repleted grafts consisting of non-manipulated bone marrow or peripheral blood grafts require intense in vivo GvHD prophylaxis. There are two major T-cell replete protocols: one is based on post-transplantation cyclophosphamide (PTCy), while the other is based on anti-thymocyte globulin (ATG; Beijing protocol). Published data do not show an unequivocal benefit for one of these three platforms in terms of overall survival, non-relapse mortality or disease recurrence. In this review, we discuss the pros and cons of these three different approaches to hHSCT with an emphasis on the significance of the existing data for children with acute lymphoblastic leukaemia.

TCR α+ β+ /CD19+ cell-depleted hematopoietic stem cell transplantation for pediatric patients

TCR α⁺ β⁺ /CD19⁺ cell depletion is an emerging technique for ex vivo graft manipulation in HSCT. We report 20 pediatric patients who underwent TCR α⁺ β⁺ /CD19⁺ cell-depleted HSCT in four Australian centers. Conditioning regimen was dependent on HSCT indication, which included immunodeficiency (n = 14), Fanconi anemia (n = 3), and acute leukemia (n = 3). Donor sources were haploidentical parent (n = 17), haploidentical sibling (n = 2), or matched unrelated donor (n = 1). Mean cell dose was 8.2 × 10⁸ /kg TNC, 12.1 × 10⁶ /kg CD34⁺ cells, and 0.4 × 10⁵ /kg TCR α⁺ β⁺ cells. All patients achieved primary neutrophil and platelet engraftment, with average time to neutrophil engraftment 11 days (range 8-22) and platelet engraftment 24 days (range 12-69). TRM at 1 year was 15%. Rate of grade II-IV aGVHD at 1 year was 20% with no grade III-IV aGVHD seen. CMV reactivation occurred in 81% of CMV-positive recipients, with one patient developing CMV disease. Average time to CD4 recovery (>400 × 10⁶ /L) was 258 days. Overall survival for the cohort at 5 years was 80%. This report highlights the initial experience of TCR α⁺ β⁺ /CD19⁺ cell-depleted HSCT in Australian centers, with high rates of engraftment, low rates of aGVHD, and acceptable TRM.

Posttransplant Cyclophosphamide for HLA-haploidentical Transplantation in Patients With Mucopolysaccharidosis

We successfully used a haploidentical transplantation protocol with posttransplant cyclophosphamide (CY) (50 mg/kg/d on days +3 and +4) for in vivo T-cell depletion in patients with mucopolysaccharidosis using reduced-intensive conditioning regimens, followed by a busulfan-based conditioning regimen, which included busulfan (12 to 16 mg/kg) and fludarabine(150 to 200 mg/m)+rabbit antihuman thymocyte globulin (7.5 to 10 mg/kg) as a conditioning regimen. Cyclosporine or tacrolimus, methotrexate, mycophenolate mofetil, and methylprednisolone were administered to prevent graft-versus-host disease (GVHD). After follow-up for a median period of 1.5 years, all 8 patients without preexisting severe comorbidities and early transplant referrals are alive, with 100% donor chimerism and excellent performance status. Only 1 patient developed chronic GVHD(II). We conclude that posttransplant CY is effective in vivo for T-cell depletion to promote full donor engraftment in patients with mucopolysaccharidosis. In addition, with posttransplant CY, the procedure reduced the rate of GVHD and the cost of transplant and improved the patients' quality of life.

Treosulfan-Based Conditioning Regimen in Sibling and Alternative Donor Hematopoietic Stem Cell Transplantation for Children with Sickle Cell Disease

BACKGROUND AND OBJECTIVES

Lack of suitable donors and regimen related toxicity are major barriers for hematopoietic stem cell transplantation (HSCT) in patients with sickle cell disease (SCD). The aim of the study is the assessment of efficacy and toxicity of Treosulfan-based conditioning regimen for SCD also when alternative donors such as mismatched unrelated donor and haploidentical donor are employed.

METHODS

We report our single-center experience: 11 patients with SCD received HSCT with a Treosulfan/Thiotepa/Fludarabine/Anti-thymoglobulin conditioning regimen between 2010 and 2015. The donor was a matched sibling donor (n= 7), a haploidentical parent (n= 2), a matched unrelated donor (n= 1) or a mismatched unrelated donor (n=1). The haploidentical and mismatched unrelated donor grafts were manipulated by removing TCRαβ and CD19 positive cells.

RESULTS

All patients survived the procedure and achieved stable engraftment. Stable mixed chimerism was observed in 5/11 patients. Grade III-IV regimen related toxicity was limited to mucositis and no grade III-IV graft-versus-host disease (GvHD) occurred. No SCD manifestation was observed post transplant and cerebral vasculopathy improved in 3/5 evaluable patients. Organ function evaluation showed no pulmonary, cardiac or renal toxicity but gonadal failure occurred in 1/4 evaluable patients.

CONCLUSION

Our data suggest that Treosulfan is associated with low toxicity and may be employed also for unrelated and haploidentical donor HSCT.