{
  "abstract": "Background and Importance Dose-response trials initially supported a weight-based dose of 2 mg/kg of pembrolizumab, however a fixed-dose of 200 mg was subsequently established. 1 The pharmacokinetic and pharmacodynamic characteristics of fixed doses and doses based on bodyweight are similar.2 Various organisations such as the Canadian Agency for Drugs (CADTH) and Technologies in Health and the National Health Service in England (NICE) have recommended dosing pembrolizumab by weight.3 4 Aim and Objectives To assess the economic impact of implementing a weight-based dosing protocol for pembrolizumab in our region, in comparison with the standard fixed-dose regimen.Material and Methods A multicentric and retrospective study was carried out from September 2024 to September 2025. The variables collected were age, sex, weight, administered cycles and proportion of patients treated with weight-based dosing. All patients were undergoing treatment with pembrolizumab for an authorised indication. Cost of cycle using a fixed-dose regimen and without weight-based adjustment were determined. To estimate the economic impact, we compared the real cost of weight-adjusted pembrolizumab dosing, administered since protocol implementation (September 2024), with the projected cost of fixed dosing for the same patient cohort. Data collection was performed using program Farmatools and Excel.Results A total of 295 patients were included with median age 66 (34-93) years. There were 46.8% women and 53.2% men. The average weight was 77 (40-118) kg. Median total of cycles received was five (1-14). Patients on weight-adjusted dosing accounted for 65.8% of all those treated with pembrolizumab. In our patients, administering a weight-adjusted treatment cycle results in a 23% reduction in cost, which implied a mean of 497.6 euros per patient. Since the implementation of the protocol, the introduction of the weight-based dosage has led to a 9.4% reduction in expenditure, which translates into a total of 397,000.2 euros in our region.Conclusion and Relevance Since the introduction of the protocol, weight-based dosing has been chosen in more than half of the patients treated with pembrolizumab. This strategy could be considered an efficient cost reduction measure that contributes to the sustainability of healthcare system.References and/or Acknowledgements 1. European Medicines Agency (EMA):EPAR. https://www.ema.europa.eu/en/documents/assessment-report/keytruda-epar-public-assessment-report_en.pdf2. Freshwater T, et al. Evaluation of dosing strategy for pembrolizumab for oncology indications. doi:10.1186/s40425-017-0242-53. 3.CADTH: https://www.cda-amc.ca/sites/default/files/ou-tr/ho0008-dosing-timing-immuno-oncology-drugs.pdf4. 4.NICE: https://www.england.nhs.uk/wp-content/uploads/2018/04/National-Dose-Banding-Table-Pembrolizumab-25mgmL-v3.pdfConflict of Interest No conflict of interest",
  "authors": [
    {
      "affiliations": [
        "Servicio Extremeño De Salud, Servicios Centrales. Subdirección De Farmacia., Mérida- Badajoz, Spain"
      ],
      "name": "C Moreno Ramos"
    },
    {
      "affiliations": [
        "Servicio Extremeño De Salud, Servicios Centrales. Subdirección De Farmacia., Mérida- Badajoz, Spain"
      ],
      "name": "R Castillejo-Garcia"
    },
    {
      "affiliations": [
        "Servicio Extremeño De Salud, Servicios Centrales. Subdirección De Farmacia., Mérida- Badajoz, Spain"
      ],
      "name": "FA Lao-Dominguez"
    }
  ],
  "title": "4CPS-130 Pharmacoeconomic analysis of the pembrolizumab dosing regimen by bodyweight: a multicentre study in real-life",
  "uid": "365f5614-6f48-51a2-8b65-5486fd0052f5"
}