Background and Significance: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) offers curative potential for hematologic malignancies but carries significant bleeding risks, affecting up to one-third of recipients. Delayed platelet engraftment (DPE) occurring in 5–37% of allo-HSCT patients, drives hemorrhage risk and correlates with increased infection, graft-versus-host disease (GVHD), and transplant-related complications. No standardized thrombopoietic support exists for DPE management, while previous studies recommend platelet transfusions, recombinant human thrombopoietin (rhTPO), or thrombopoietin receptor agonists (TPO-RAs), et al. The efficacy of romiplostim (a TOP-RA) for the treatment thrombocytopenia post HSCT has been published in several articles. However, the efficacy of romiplostim versus rhTPO for improving platelet engraftment after allo-HSCT has not yet been assessed. Romiplostim N01, a long-acting TPO-RA developed and produced by Chinese pharmaceutical enterprise, is approved by the National Medical Products Administration (NMPA) for immune thrombocytopenia (ITP). Considering the convenience of drug administration and economic costs, romiplostim N01 is significant valuable for transplant patients compared to rhTPO.

This study addresses these gaps by evaluating romiplostim N01 versus rhTPO for DPE management, with implications for optimizing supportive care strategies in allo-HSCT.

Study design and Methods: This investigator-initiated, prospective, randomized, multicenter trial (ChiCTR2500096407) compares romiplostim N01 versus rhTPO in terms of platelet engraftment following allo-HSCT. Conducted across three centers (The First Affiliated Hospital of Nanchang University, Jiangxi Provincial Children's Hospital, First Affiliated Hospital of Gannan Medical University) in China, the protocol has received approval from the institutional ethics committees.

100 patients (age unrestricted, weight ≥ 30 kg, Eastern Cooperative Oncology Group [ECOG] performance status ≤ 1) with hematologic malignancies planned for allo-HSCT will be randomized 1:1 to receive romiplostim N01 (initiation dosage at 3µg/kg, subcutaneously once weekly) or rhTPO (300U/kg/d, administered subcutaneously for a maximum of 14 consecutive days) treatment. Exclusion criteria include severe organ dysfunction (e.g., cardiac, hepatic, renal, pancreatic) or uncontrolled comorbidities. Patients are treated starting day +3 after allo-HSCT until the platelet count exceed 70×109/L without platelet transfusion. Dose of romiplostim N01 is adjusted based on a predefined regimen according to the platelet count. Patients receive no more than 4 doses of romiplostim N01 or 14 days rhTPO even if engraftment is delayed. The primary endpoint is time to platelet engraftment (platelet count exceeding 20×109/L for 7 consecutive days without need for platelet transfusion). The secondary endpoints included the cumulative platelet engraftment rate by day +28, 28-day cumulative platelet transfusion volume, incidence and severity of bleeding events, time to neutrophil engraftment (neutrophil count exceeding 0.5×109/L for 3 consecutive days without granulocyte colony-stimulating factor support), progression-free survival (PFS), overall survival (OS) and safety (adverse events [AEs], serious AEs [SAEs]). The first patient was included in February 2025. As of July 15, 2025, 31 patients have been enrolled (of 100 planned).

Conclusions: Optimal management of delayed platelet engraftment post-allo-HSCT remains clinically challenging. While prior studies have been limited to single-arm, single-center designs, this first randomized trial comparing romiplostim N01 versus rhTPO will generate pivotal evidence to optimize thrombopoietic support strategies and inform clinical guidelines.

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2025
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