The objective of this observational study is to investigate the long-term effects of Hetrombopag in promoting platelet engraftment during haploidentical hematopoietic stem cell transplantation (HSCT) in children with thalassemia, with a specific focus on a 28-day time window post-transplantation. The core question to be addressed is: Is Hetrombopag safe and effective for platelet engraftment in children with thalassemia undergoing haploidentical HSCT within a 28-day post-transplant period? Subjects who received Hetrombopag as part of routine care for haploidentical HSCT in children with thalassemia will be required to complete a 28-day online survey on platelet engraftment outcomes.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a critical and often the sole curative modality for diverse hematological malignancies and disorders. Post-transplant thrombocytopenia (platelet count <20×10⁹/L) significantly compromises long-term patient survival, with an incidence of 5-20% in allo-HSCT recipients, thereby escalating treatment morbidity and costs. Current research on platelet engraftment promotion in pediatric thalassemia patients undergoing allo-HSCT is limited. Repeated platelet transfusions are associated with substantial complications, including transfusion reactions, platelet alloimmunization, and transfusion-transmitted viral infections. Eltrombopag, a thrombopoietin receptor agonist (TPO-RA), carries a black-box warning for hepatotoxicity, with a real-world incidence of 11.8%. Transplant recipients frequently experience diarrhea, which impairs the absorption of oral thrombopoietic agents, while daily subcutaneous injections exacerbate pediatric patient discomfort and reduce treatment adherence. In contrast, long-acting TPO-RAs administered once post-transplant have demonstrated favorable tolerability and promising efficacy in thalassemia transplant pediatric populations. To date, clinical data on Hetrombopag use for platelet recovery in haploidentical HSCT for pediatric thalassemia are lacking. Therefore, this observational study aims to evaluate the efficacy and safety of Hetrombopag in facilitating platelet engraftment during haploidentical HSCT in children with thalassemia.

Inclusion Criteria:

• Diagnosed with severe thalassemia via thalassemia gene testing, transfusion history, and complete blood count (CBC).
• Pediatric patients aged 2-17 years.
• Consented to haploidentical transplantation and evaluated by the transplant team as having no transplant contraindications.

Exclusion Criteria:

• Presence of a fully matched donor with refusal of haploidentical transplantation.
• Donor or recipient with transaminase levels >2× the upper limit of normal (ULN).
• Positive hepatitis B DNA test result.
• Active infection at the time of enrollment.
• Donor-specific antibodies (DSA) >5,000 and unable to decrease below 3,000 after antibody therapy.
• Presence of transplant contraindications as assessed by the transplant team.

The Department of Hematology of Haikou People's Hospital accepts children with severe thalassemia aged 2 - 17 years old for haploidentical hematopoietic stem cell transplantation.

The IPD encompasses highly sensitive and confidential data that was collected through significant investment of our resources, both in terms of time and funding. This data is integral to our ongoing research initiatives, which are at a crucial stage of development. Premature sharing could disrupt our research timelines and strategic plans. Additionally, we have not yet established comprehensive safeguards to ensure that the data will be used appropriately by external researchers. Without proper protocols in place, there is a risk of misuse or misinterpretation of the data, which could lead to inaccurate research outcomes and potential reputational damage to our institution. For these reasons, we have decided not to share the IPD at this time.