Characteristics and clinical outcomes of patients with severe asthma receiving tezepelumab after marketing approval in Spain (T-ROSS II study): an observational study protocol.

backgroundAsthma is a prevalent chronic respiratory disease characterised by airway inflammation, reversible airflow obstruction and airway hyper-responsiveness. Most patients with severe asthma (SA) remain uncontrolled despite the availability of multiple therapies, representing a significant global health burden.Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine that plays a central role in asthma initiation via both allergic and non-allergic mechanisms as well as in the persistence of airway inflammation in patients with asthma, acting upstream in the inflammatory cascade.Tezepelumab, a monoclonal antibody that targets TSLP, has shown clinical efficacy and safety in pivotal trials in patients with T2 and non-T2 asthma. Tezepelumab was approved for use in Europe in October 2022, and the marketing authorisation was issued in Spain in October 2023. METHODS/

designThe T-ROSS II study is a retrospective, observational, single-arm, multicentre study planned to include 400 patients aged ≥12 years treated in SA units. T-ROSS II will represent the largest published series of patients with SA who initiated tezepelumab after its market authorisation.Eligible patients must have at least 12 months of medical history prior to treatment initiation and a minimum of 3 months of follow-up data recorded in the electronic health records.The co-primary outcomes are to describe baseline patient demographics and clinical characteristics and evaluate changes in the annualised asthma exacerbation rate before and after the initiation of tezepelumab. DISCUSSION: These findings will complement clinical trial data and inform physicians and healthcare decision-makers about the real-world effectiveness and utilization of tezepelumab in patients with SA. This study is expected to provide valuable insights into the clinical outcomes and treatment patterns of this population. ETHICS AND DISSEMINATION: The final protocol of the study has been approved by the ethics committee/Institutional Review Board (EC/IRB) of the University Hospital 12 de Octubre (Madrid, Spain) (EC/IRB number: 25/226). The results will be disseminated through scientific publications, including manuscripts submitted to peer-reviewed journals and presentations at national and international congresses. TRIAL REGISTRATION NUMBER: NCT07013760.