RESUMEN
Background: X-linked hypophosphatemia (XLH) is a rare, progressive disorder characterized by excess fibroblast growth factor 23 (FGF23), causing renal phosphate-wasting and impaired active vitamin D synthesis. Burosumab is a recombinant human monoclonal antibody that inhibits FGF23, restoring patient serum phosphate levels. Safety data on long-term burosumab treatment are currently limited. Objectives: This post-authorization safety study (PASS) aims to monitor long-term safety outcomes in children and adolescents (1-17 years) treated with burosumab for XLH. This first interim analysis reports the initial PASS safety outcomes. Design: A 10-year retrospective and prospective cohort study. Methods: This PASS utilizes International XLH Registry (NCT03193476) data, which includes standard diagnostic and monitoring practice data at participating European centers. Results: At data cut-off (13 May 2021), 647 participants were included in the International XLH Registry; 367 were receiving burosumab, of which 67 provided consent to be included in the PASS. Mean (SD) follow-up time was 2.2 (1.0) years. Mean (SD) age was 7.3 (4.3) years (range 1.0-17.5 years). Mean duration of burosumab exposure was 29.7 (25.0) months. Overall, 25/67 participants (37.3%) experienced ⩾1 adverse event (AE) during follow-up; 83 AEs were reported. There were no deaths, no AEs leading to treatment withdrawal, nor serious AEs related to treatment. The most frequently reported AEs were classified as 'musculoskeletal and connective tissue disorders', with 'pain in extremity' most frequently reported, followed by 'infections and infestations', with 'tooth abscess' the most frequently reported. Conclusion: In this first interim analysis of the PASS, covering the initial 2 years of data collection, the safety profile of burosumab is consistent with previously reported safety data. The PASS will provide long-term safety data over its 10-year duration for healthcare providers and participants with XLH that contribute to improvements in the knowledge of burosumab safety. Trial registration: European Union electronic Register of Post-Authorisation Studies: EUPAS32190.
RESUMEN
CONTEXT: X-linked hypophosphatemia (XLH) is a rare genetic disorder causing renal phosphate wasting, which predicates musculoskeletal manifestations such as rickets. Diagnosis is often delayed. OBJECTIVE: To explore the recording of clinical features, and the diagnostic odyssey of children and adolescents with XLH in primary care electronic healthcare records (EHRs) in the United Kingdom. METHODS: Using the Optimum Patient Care Research Database, individuals aged 20 years or younger after January 1, 2000, at date of recorded XLH diagnosis were identified using Systematized Nomenclature of Medicine Clinical Terms (SNOMED)/Read codes and age-matched to 100 controls. Recording of XLH-related clinical features was summarized then compared between cases and controls using chi-squared or Fisher's exact test. RESULTS: In total, 261 XLH cases were identified; 99 met the inclusion criteria. Of these, 84/99 had at least 1 XLH-related clinical feature recorded in their primary care EHR. Clinical codes for rickets, genu varum, and low phosphate were recorded prior to XLH diagnosis in under 20% of cases (median of 1, 1, and 3 years prior, respectively). Rickets, genu varum, low phosphate, nephrocalcinosis, and growth delay were significantly more likely to be recorded in cases. CONCLUSION: This characterization of the EHR phenotypes of children and adolescents with XLH may inform future case-finding approaches to expedite diagnosis in primary care.