Kyowa Kirin Presents Real-World Findings at ASBMR Annual Meeting Highlighting Progressive Disease Burden of X-linked Hypophosphatemia (XLH)

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• Kyowa Kirin, Inc., an affiliate of Kyowa Kirin Co., Ltd. (Kyowa Kirin, TSE: 4151), a global specialty pharmaceutical company based in Japan, presented two posters at the American Society for Bone and Mineral Research (ASBMR) 2023 annual meeting in Vancouver, BC, Canada, demonstrating the significant burden and progressive, accumulative nature of X-linked hypophosphatemia (XLH), a rare genetic metabolic bone disease. "Because XLH is a progressive, life-long disease, it's important to understand the clinical characteristics and real-world impact on patients over time," said Zhiyi Li, MA, MBA, one of the study authors and director of health economics and outcomes research at Kyowa Kirin North America. "Both studies found that serious disease-related morbidities often start at a young age and accumulate over time, an important consideration for physicians when making decisions about patient care." Real-world characteristics and disease history of patients with X-linked hypophosphatemia treated with burosumab: a United States claims database study In this retrospective cohort study, researchers examined the patient characteristics and disease history of 1,358 people ≥6 months of age prior to initiation of treatment with burosumab using Komodo Health's Healthcare Map™, a real-world de-identified patient-level claims database assembled from clearinghouse, payer, and provider data sources. Among the claims assessed, researchers found high levels of XLH-related morbidities and extra-musculoskeletal manifestations, including osteoarthritis, arthralgia (joint pain), fractures, muscle pain, spinal stenosis, hypertension, obesity, depression, renal disease and enthesopathy, a disorder that affects the site of attachment between bones and tendons or ligaments.1 Most of these complications were seen in early adulthood and increased with age group. Most patients had received some form of conventional therapy for XLH prior to burosumab treatment, with 61% receiving calcitriol and 43% receiving phosphate supplements. Physical therapy use was also observed across all age groups. There were several study limitations including the lack of a specific diagnosis code for XLH. Patients were identified using diagnosis codes for familial hypophosphatemia (FH) and other disorders of phosphorus metabolism; however, the inclusion of burosumab claims helped to minimize the inclusion of misdiagnosed patients, as XLH is the only disorder of FH for which burosumab is indicated. In addition, the study used non-primary insurer (open source) claims, which captures a higher number of medical claims as compared to payer-complete (closed source) claims; however, completeness is not guaranteed. Older patients were under-represented in the study population, limiting the generalizability of the findings to this group. Clinical and treatment characteristics of pediatric and adult patients with familial hypophosphatemia compared with demographically matched controls In this retrospective observational cohort study, researchers examined healthcare claims data from the Merative™ MarketScan® Commercial and Medicare Databases. The analysis compared 570 patients with at least one diagnosis code for FH to 1,710 people without FH in a matched control group. FH represents a group of rare genetic disorders characterized by impaired renal phosphate conservation; roughly 80% of FH cases are classified as XLH.2 Patients were excluded from the study if ever prescribed burosumab. The study found patients with FH experienced multiple FH-related morbidities, supplemented with oral phosphate and active vitamin D, and used healthcare services for managing orthopedic conditions at a significantly greater rate than the control group. The differences between the study groups were apparent even among young children and persisted throughout a person's life. Key findings included: Kidney disease, joint pain, osteoarthritis, delayed growth/walking, muscle weakness, and fracture were the most common FH-related morbidities; all were significantly more common among patients with FH (P<0.001) and generally increased with age. Depression (FH: 22.5% vs. controls: 5.6%), hypertension (55.4% vs. 17.4%), and obesity (34.0% vs. 16.4%) were more common among patients with FH (P<0.001). Most monitoring and management practices to control FH and associated morbidities were more common among patients with FH, including laboratory tests, physical therapy, and use of walking assistance devices (all P <0.001). This study was limited to patients with commercial health insurance or Medicare coverage; results may not be generalizable to patients with other types of insurance (e.g., Medicaid) or the uninsured, and the study population may under-represent the true burden of disease. Patients with FH who received burosumab during the study period were excluded. The outcomes assessed in this study may differ for burosumab-treated patients.