Plain language summary of a study looking at the safety of burosumab in children and adolescents with X-linked hypophosphatemia

Plain Language Summary: What is this summary about? X-linked hypophosphatemia (XLH for short) is a genetic condition where people have low levels of phosphate in the blood because too much phosphate is lost in the urine. XLH is rare, occurring in just one in 20,000–70,000 people. XLH affects bones, muscles, and joints, leading to bow legs (when the legs curve outwards at the knees) or knock knees (when the legs curve inwards at the knees), reduced growth, dental problems, pain, and increased fatigue. Burosumab is the latest available treatment for XLH, but so far information about its safety is incomplete. To better understand its safety, researchers set up a post-authorization safety study (PASS) using information from participants who agreed to have their data collected in a database called the International XLH Registry. A PASS study occurs after a treatment has been approved for treating a medical condition to gather more information about the safety of the treatment. This study is ongoing, and this summary describes the results from its first interim analysis. This included information gathered in children and adolescents only. What were the results? A total of 67 children and adolescents with XLH from six European countries were included in the study. All were treated with burosumab in the study: 36 took burosumab only, and 31 had previously taken oral phosphate supplements and/or active vitamin D before burosumab. The participants took burosumab for an average of 30 months. The most common adverse events were ‘pain in extremity’, ‘tooth abscess’ (infection), ‘joint pain’, and ‘pain’, which can be signs and symptoms of XLH itself. A total of 12 out of 67 participants had adverse events that were probably or possibly related to burosumab treatment. The most common of these were ‘pain in extremity’, ‘tooth abscess’, and ‘injection site erythema’ (redness of the skin). Five participants had chronic kidney disease before the study started: three of these had adverse events, and one had adverse events probably or possibly related to burosumab. What do the results mean? This study had similar results to those from clinical trials of burosumab in people with XLH. Specifically, treating people with XLH with burosumab in real-life clinical settings identified no new adverse events, and most of the reported adverse events were the same as well-known symptoms of XLH. How to say (download PDF and double click sound icon to play sound)… Abscess: Ab-ses Burosumab: bur-OH-sue-mab Chromosome: KROH-muh-some Craniosynostosis: KRAY-ni-oh-SIN-os-TOH-sis Fibroblast growth factor: FY-broh-blast grothe FAK-ter Hypercalciuria: HY-pur-kal-SYOOR-ee-uh Hyperphosphatemia: HY-pur-FOS-fuh-TEE-mee-uh Hypophosphatemia: HY-poh-FOS-fuh-TEE-mee-uh Monoclonal antibody: MAH-noh-KLOH-nul AN-tee-BAH-dee Nephrocalcinosis: neff-ROH-kal-suh-NOH-suhss Osteomalacia: OS-tee-oh-muh-LAY-shuh Parathyroid hormone: pair-uh-THIGH-royd HOR-mohn Phosphate: FOS-fayt Rickets: RIH-kets Interim analysis: An analysis of data from an ongoing study. This means that the PASS study is still ongoing and that the final analysis has not been completed yet, therefore the results should be interpreted with caution. Adverse events: An unfavorable change in health. The researchers may have decided that an adverse event was caused by the treatment, or other reasons, such as the disease being studied. Adverse events can range from mild to life-threatening, and can cause death. This is an abstract of the Plain Language Summary of Publication article. View the full Plain Language Summary PDF of this article to read the full-text Link to original article here Trial registration:ClinicalTrials.gov identifier: NCT03193476; ClinicalTrials.gov identifier: EUPAS32190.