Efficacy and Safety of Romiplostim in Treating Thrombocytopenia After Hematopoietic Stem Cell Transplantation in Pediatric Patients: A Single-Arm Clinical Trial Publisher Pubmed



Karimizadeh Z ; Behfar M ; Karimzadeh A ; Jafari L ; Kalantari A ; Nikfetrat Z ; Hamidieh AA
Source: Transplantation and Cellular Therapy Published:2026

Abstract

Prolonged thrombocytopenia after hematopoietic stem cell transplantation (HSCT) in pediatric patients is associated with significant morbidity, including increased transfusion dependency, bleeding events, and reduced survival. Romiplostim (Nplate, Amgen), a thrombopoietin receptor agonist, has shown efficacy in various thrombocytopenic disorders but remains understudied in the post-HSCT pediatric setting. This prospective single-arm clinical trial enrolled 47 pediatric patients (median age 7 yr, range 0.42 to 17 yr) with prolonged isolated thrombocytopenia (n = 14) or secondary failure of platelet recovery (SFPR; n = 33) post-HSCT. Patients received weekly subcutaneous romiplostim at 5 μg/kg for up to 12 wk or until platelet count >100 × 10⁹/L. Primary endpoints were hematologic response (complete response [CR]: platelet >100 × 10⁹/L; partial response [PR]: >50 × 10⁹/L; minimal response [MR]: increase >10 × 10⁹/L from baseline), transfusion independence, and bleeding events (World Health Organization scale). Secondary endpoints included erythroid/neutrophil responses, safety (National Cancer Institute Common Terminology Criteria for Adverse Events v5.0), graft-versus-host disease (GVHD), and 6-mo overall survival (OS)/event-free survival (EFS). Overall response rate (CR + PR + MR) was 80.9% (CR: 42.6%; PR: 25.5%; MR: 12.8%). Median time to platelet >50 × 10⁹/L was 3 wk (range 1 to 12); 81.6% of responders (31/38) maintained treatment-free response for ≥12 wk. Platelet and packed red blood cell transfusion independence was achieved in 74.5% (35/47) and 78.9% (30/38) of the patients, respectively (both P < .001). Bleeding events significantly decreased, with grade 0 to 1 increasing from 55.3% to 80.9% (P < .001). Erythroid response occurred in 81.6% (31/38), and neutrophil improvement was observed in 50% (2/4) of evaluable patients. No serious adverse events or discontinuations occurred; minor events (eg, headache, diarrhea) were reported in 27.7% of the patients. Acute and chronic GVHD occurred in 53.2% (grades III to IV: 36.1%) and 25.5% of the patients, respectively. Six-month OS and EFS were 82.3% and 70.1%, respectively. Romiplostim is safe and effective for post-HSCT thrombocytopenia in children, providing rapid, durable responses and reducing transfusion needs and bleeding. As the largest prospective pediatric study to date, these findings support multicenter randomized trials to optimize its role in HSCT supportive care. © 2026 American Society for Transplantation and Cellular Therapy. Published by Elsevier, Inc.