{
  "abstract": "Background and Importance Sinusoidal obstruction syndrome (SOS) is a potentially life-threatening complication after haematopoietic stem cell transplantation (HSCT). Defibrotide, an endothelial-protective agent, is established for SOS treatment and has been used prophylactically in high-risk paediatric subgroups; however, its prophylactic role is not well defined, and real-world paediatric evidence remains limited.Aim and Objectives To describe patient characteristics and SOS outcomes at days +30 and +100 in paediatric HSCT patients, at a tertiary paediatric hospital, who met SOS risk criteria and received defibrotide prophylaxis.Material and Methods Retrospective cohort of paediatric patients undergoing HSCT between January 2023 and June 2025 fulfilling ≥1 SOS-risk criteria (high-risk neuroblastoma, adrenoleukodystrophy, prior HSCT, prior SOS, iron overload, exposure to inotuzumab/gemtuzumab ozogamicin). Variables: sex, age, diagnosis, transplant type, risk factors. Outcomes: cumulative incidence of SOS by day +30 and day +100 from HSCT, and severity grade per EBMT criteria. Descriptive statistics are reported as median (range).Results Thirty-three children were included (60% girls) and the median age was 10.7 years (1.0–19.3). Diagnoses were B-ALL 10/33 (30.3%), neuroblastoma 9/33 (27.3%), AML 6/33 (18.2%), adrenoleukodystrophy 3/33 (9.1%), and other conditions 5/33 (15.2%). Transplant type was allogeneic in 22/33 (66.7%) and autologous in 11/33 (33.3%). Prophylaxis regimen was defibrotide 6.25 mg/kg every 6 hours for 21 days. Cumulative SOS incidence was 6/33 (18.2%) by day +30 and 9/33 (27.3%) by day +100. Among the nine SOS cases, severity was mild in 4/9 (44.4%), moderate in 3/9 (33.3%), and severe in 2/9 (22.2%). The table details SOS development by risk-factor category. Risk factor (n/N,%) SOS by day +30 SOS by day +100 High-risk neuroblastoma 9/33 (27.3%) 3/9 (33.3%) 3/9 (33.3%) Adrenoleukodystrophy 3/33 (9.1%) 0/3 (0%) 0/3 (0%) Prior HSCT 10/33 (30.3%) 1/10 (10.0%) 2/10 (20%)* Prior SOS 3/33 (9.1%) 0/3 (0%) 0/3 (0%) Iron overload 4/33 (12.1%) 0/4 (0%) 1/4 (25%) Inotuzumab exposure 9/33 (27.3%) 1/9 (11.1%) 3/9 (33.3%)* Gemtuzumab exposure 1/33 (3.0%) 1/1 (100%) 1/1 (100%) *One SOS case had two risk factors: prior HSCT and inotuzumab exposure.Conclusion and Relevance Evidence for defibrotide prophylaxis in high-risk paediatric HSCT remains limited. This study offers a real-world perspective and underscores the importance of standardised risk assessment and close multidisciplinary monitoring. Further research is needed to define the role of defibrotide prophylaxis, identify which paediatric subgroups benefit most, and assess its comparative effectiveness against alternative strategies.Conflict of Interest No conflict of interest",
  "authors": [
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "E Algarra"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "A Merino Pardo"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "MI Gonzalez Rodriguez"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "B Arce Abaitua"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "L Fernández Romero"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "B Leal Pino"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "B Riva De La Hoz"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "M Echávarri De Miguel"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "A Abril Cabero"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "E Nieto Martil"
    },
    {
      "affiliations": [
        "Hospital Infantil Universitario Niño Jesus, Pharmacy, Madrid, Spain"
      ],
      "name": "M Pozas Del Río"
    }
  ],
  "title": "4CPS-249 Defibrotide prophylaxis in high-risk paediatric patients undergoing haematopoietic stem cell transplantation: real-world cohort",
  "uid": "7d3666c3-99ef-5224-8833-4339c867a19f"
}