-Author name in bold denotes the presenting author
-Asterisk * with author name denotes a Non-ASH member
Clinically Relevant Abstract denotes an abstract that is clinically relevant.

PhD Trainee denotes that this is a recommended PHD Trainee Session.

Ticketed Session denotes that this is a ticketed session.

4953 A Novel Protocol Improves Engraftment in Tαβ+ Cell Depleted Haplo-HSCT for Patients with Thalassemia Major

Program: Oral and Poster Abstracts
Session: 723. Allogeneic Transplantation: Long-term Follow-up and Disease Recurrence: Poster III
Hematology Disease Topics & Pathways:
Research, clinical trials, Clinical Research, Thalassemia, pediatric, Hemoglobinopathies, Diseases, Therapies, therapy sequence, clinical procedures, Technology and Procedures, Study Population, Human
Monday, December 11, 2023, 6:00 PM-8:00 PM

Jianyun Liao1*, Chaoke Bu1*, Lan He1*, Yuelin He1*, Jujian He1*, Dan Chen1*, Bo Lyu1*, Weiwei Zhang1*, Haoran Tang1*, Xinrui Liu1* and Chunfu Li, PhD2

1Nanfang-Chunfu Children's Institute of Hematology & Oncology, Taixin Hospital, Dongguan, China
2Nanfang-Chunfu Children's Institute of Hematology & Oncology, Taixin Hospital, Dongguan, Guangdong, China

Background: Hematopoietic stem cell transplantation (HSCT) remains a proven curative approach for patients with thalassemia major (TM) over long-term practice. However, achieving successful engraftment and managing graft-versus-host disease (GVHD) continue to pose significant challenges. While low incidence of GVHD has been observed in Tαβ+ cell-depleted HSCT (TDH) from haploidentical donors, graft failure (GF) remains a considerable concern, particularly in patients with TM. To enhance the engraftment in TM-TDH, we conducted this prospective/retrospective single-center clinical study.

Method: A total of 137 patients diagnosed with TM received TDH at the BMT-center, Taixin Hospital, between March 2021 and April 2023. The median age of the patients was 7 years (ranging from 2 to 19 years), with 89 males and 48 females. The median follow-up time was 408 days (ranging from 99 to 857 days). The conditioning regimen consisted of Thymoglobulin on -day 21, followed by 3-Gy total body irradiation on -day 11. On -day 10, the patients received an infusion of donor lymphocytes (2*108/kg), followed by cyclophosphamide (Cy) at a dose of 50mg/kg on days -8, -7, and -2, and 25mg/kg on day -1. Additionally, blood-concentration adjusted busulfan was administered on days -6 to -4, fludarabine at a dose of 40mg/kg on days -6 to -2, and thiotepa at 10mg/kg on day -3. For GVHD prophylaxis, short-term (< 6 months) low-dose tacrolimus or sirolimus with or without mycophenolate mofetil was used. The mean infused CD34+ cells were 31.09 (ranging from 14.25 to 61.12) *106/kg, TCRγδ+ cells were 39.49 (ranging from 5.18 to 140.39) *106/kg, and NK cells were 109.18 (ranging from 27.52 to 309.41) *106/kg, respectively. The targeted infusion of TCRαβ+ cells was aimed at 1.5-2.0*105/kg.

Results: Out of the 137 patients, 133 achieved successful engraftment (97.1%) with median engraftment times of 16 days (ranging from 9 to 48 days) for ANC to reach 0.5x109/L, 11 days (ranging from 1 to 23 days) for HB to reach 80g/L, and 10 days (ranging from 5 to 22 days) for platelets to reach 20x109/L, respectively. GF was observed in four patients. Among them, two patients with GF underwent salvage alternative donor second HSCT on +day 19 and +day 32, respectively, and are currently thalassemia-free. One patient received infusion of cryopreserved auto-peripheral blood stem cell and continues to live with TM. Unfortunately, four patients passed away, with one GF patient dying from suspected virus myocarditis on +day 11, one potentially due to virus hepatitis or hepatic GVHD on day +188, and the remaining two from virus bronchiolitis obliterans on +day 211 and +day 254, respectively. The overall survival (OS) and thalassemia-free survival (TFS) rates were 96.5% and 94.3%, respectively. The incidence of GF and transplant-related mortality (TRM) were 2.9% and 3.5%, respectively (Fig.). Acute GVHD of grade I-II and grade III-IV was observed in 10.53% and 9.02% of patients, respectively, while mild and moderate chronic GVHD occurred in 7(5.1%) and 1(0.7%) patient(s), respectively. The incidence of veno-occlusive disease was mild and limited.

Conclusion: The current study demonstrates the efficacy of a novel protocol in enhancing engraftment in TDH for patients with TM and with low incidence of both acute GvHD and chronic GvHD. This approach represents a significant advancement in the field of TM-TDH.

Fig.1 Curve of OS, TFS, TRM and Rejection in TM-TDH

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH