Hematopoietic Recovery and Safety Following Early Romiplostim Administration After Pediatric HSCT: A Prospective Randomized Pilot Study

ABSTRACT Background Delayed platelet recovery remains a frequent and clinically significant complication following hematopoietic stem cell transplantation (HSCT) in children, contributing to increased transfusion burden, bleeding risk, and prolonged hospitalization. Thrombopoietin receptor agonists (TPO‐RAs), including romiplostim, have demonstrated activity in post‐transplant thrombocytopenia; however, prospective pediatric data on their early post‐transplant use are limited. We evaluated the safety and potential effects of early romiplostim administration on platelet and hematopoietic recovery following pediatric HSCT. Methods In this prospective, open‐label, randomized pilot study conducted at a tertiary care center in India, children aged 1–18 years undergoing autologous or allogeneic HSCT were randomized (1:1) to receive standard post‐transplant care with or without romiplostim. Romiplostim (5 µg/kg subcutaneously) was administered on Days +1 and +8 post‐transplant (or Days +5 and +12 for haploidentical transplants with post‐transplant cyclophosphamide). The primary endpoint was time to platelet engraftment (platelet count ≥20 × 10 9 /L for 3 consecutive days without transfusion). Secondary endpoints included platelet transfusion requirements, platelet nadir, platelet counts on Day +28, time to platelet count ≥50 × 10 9 /L, neutrophil recovery, bleeding, and thrombotic events. Results Thirty‐two children were enrolled (romiplostim n = 17; control n = 15). Median time to platelet engraftment was comparable between the romiplostim and control groups (12 vs. 12.5 days; p = 0.88), with no significant difference on Kaplan–Meier analysis. Platelet transfusion requirements, platelet nadir, and time to platelet count ≥50 × 10 9 /L were also similar between groups. By Day +28, higher platelet counts were observed in the romiplostim arm, with exploratory subgroup analysis demonstrating higher platelet counts following allogeneic HSCT. Romiplostim recipients also demonstrated higher absolute neutrophil counts on Day +28. No thrombotic events, severe bleeding episodes, or drug‐related serious adverse events were observed. Conclusion Early administration of romiplostim following pediatric HSCT was safe and well tolerated, with no significant treatment‐related toxicity observed. Although it did not shorten time to platelet engraftment, exploratory analyses demonstrated higher Day +28 platelet and neutrophil counts, generating the hypothesis that romiplostim may support sustained hematopoietic recovery. These findings require confirmation in larger, adequately powered multicenter studies before conclusions regarding efficacy can be drawn.